Guidelines on Animal Epidemic Prevention Measures and Disease Prevention and Control Techniques for Flood Disasters
Since the start of summer in the south, many places have been hit by heavy rains and floods, and epidemics, especially among animals, tend to break out after flooding. So what are the animal epidemic prevention measures for flood disasters? Please keep this technical guide for disease prevention and control!
Technical Guide for Animal Disease Prevention and Control in Flood Disasters
When floods occur, large numbers of livestock and poultry die in the disaster, carcasses rot, pathogens easily spread through infection, and large amounts of pathogenic microorganisms in the soil are exposed, readily contaminating water sources and other environments; the resistance of livestock and poultry declines, making them susceptible to disease attacks, causing the occurrence and spread of major animal diseases such as African swine fever, foot-and-mouth disease, highly pathogenic porcine reproductive and respiratory syndrome, and highly pathogenic avian influenza, as well as multiple zoonoses such as schistosomiasis, anthrax, swine streptococcosis, and leptospirosis.
To do a good job in post-disaster COVID-19 prevention and control and animal epidemic prevention, disaster areas should focus on the following tasks: First, promptly carry out harmless disposal of dead animals; second, comprehensively disinfect farms, slaughterhouses, trading markets, and sites for handling livestock and poultry carcasses; third, strengthen biosafety protection measures and animal disease vaccination; fourth, strengthen feeding management to ensure the safety of livestock and poultry feed and drinking water and ensure breeding environmental hygiene; fifth, ensure the COVID-19 protection of workers in disaster areas. When handling dead animals, workers should wear protective clothing, masks, and wash hands frequently as required, and strengthen personal hygiene protection; once a worker is found to have suspected COVID-19 symptoms, report to the health department promptly.
I. Harmless disposal of dead livestock and poultry
When floods occur, because dead livestock and poultry contain large amounts of microorganisms in their bodies, if harmless disposal is not carried out promptly and they are left to rot and stink, pathogens will spread everywhere, not only polluting the environment but also easily causing zoonoses. Dead animals should be handled in accordance with the requirements of relevant regulations such as the Technical Specifications for Harmless Treatment of Dead and Diseased Animals.
(1) Treatment methods
Promptly salvage the carcasses of dead livestock and poultry. Incineration, rendering, and other methods are preferred for professional harmless disposal. Where conditions do not permit, deep burial may be chosen; deep burial should select high ground, and where conditions permit, incineration followed by deep burial may be used.
(2) Technical points for deep burial treatment of livestock and poultry carcasses in disaster areas
1. Facilities and equipment. According to the number of dead animals to be handled, prepare working tools, such as trucks (lay plastic film on the bottom contact surface of the truck), tractors, excavators, bulldozers, loading and unloading tools, animal carcass bags (preferably sealed), etc. Transport vehicles should prevent leakage of body fluids, and contact surfaces should be easy to repeatedly clean and disinfect.
2. Transport of livestock and poultry carcasses. Animal carcasses should preferably be placed in sealed bags. Transport vehicles should be sealed and impermeable. Vehicles and related transport facilities should be disinfected when leaving pens and burial sites. Animal carcasses must not be transported in the same vehicle as food or live livestock and poultry.
3. Selection of deep burial pits for livestock and poultry. There should be enough covering soil, soil permeability should not be high (if soil permeability is high, the bottom of the burial pit should be at least 1 m above the groundwater level), and there should be a certain distance from water bodies such as rivers, lakes, ponds, and well water, at least 100 m to 150 m. In addition, consider convenient transport of animal carcasses, avoid public view, keep at least 100 m from residential areas, and avoid flood discharge channels, places frequently scoured by floods, and rock layers.
Under specific circumstances, on-site burial may be considered for dead animals on farms. Scattered small animals (such as chickens) may be buried under tree roots and similar places.
4. Excavation of the burial pit. The volume of the pit is generally 2 to 4 times the volume of the animal carcasses. The width of the pit is generally not less than 1.2 m, the depth is generally 2 m and not more than 3 m, and the length must be able to accommodate all dead animals. The bottom of the pit should be relatively flat. The pit volume can be calculated according to the estimated weight of the animal carcasses: animal carcass volume (cubic meters) = estimated weight of animal carcasses (kg) / 1000.
5. Burial methods and requirements. Spread quicklime at the bottom of the burial pit, then lay some combustible material; place the carcasses in the pit, pour on fuel oil for incineration, and after incineration, cover with soil. The thickness of the covering soil layer must not be less than 1.5 m. When the number of small animal carcasses is large, they may be incinerated and buried in layers. The thickness of each layer of carcasses should generally not exceed 0.3 m, with at least 0.3 m of combustible material laid between layers, incinerated and buried layer by layer in sequence, and finally the thickness of the covering soil layer must not be less than 1.5 m. During burial, the covering soil must not be compacted, so as not to affect natural decomposition. After burial, prevent wild animals (wild dogs, wild cats, etc.) from digging.
6. Set up warning lines and warning signs around harmless disposal sites. Prevent personnel from entering by mistake and causing danger; arrange staff to patrol regularly as required to prevent lawbreakers from stealing and digging up livestock and poultry carcasses for resale.
7. For livestock and poultry carcasses that died from zoonoses such as anthrax, dissection is prohibited, and direct burial disposal is absolutely not allowed; the carcasses must first be incinerated, and after complete incineration, the incinerated material should then be deeply buried together.
8. Animal carcasses found in the field should also be collected promptly for harmless disposal.
(3) Protection and safety of workers
First, when carrying out harmless disposal operations, workers should wear protective clothing, rubber gloves, masks, goggles, and rubber boots. Second, after disposal is completed, clean and disinfect promptly, receive health monitoring, and if adverse symptoms appear, go to the health department for examination as soon as possible.
(4) Treatment of livestock and poultry excreta and sewage
Livestock and poultry manure, bedding straw, and sewage must all enter biogas pits or be centrally piled and fermented in a sealed manner for 42 days before being returned to the fields for use; a small amount of manure or bedding straw may be air-dried, dried, and centrally incinerated; sewage from farms must undergo 3 sedimentation cycles, and only the clear water flowing out may be discharged.
(5) Inform farmers that it is strictly prohibited to arbitrarily discard livestock and poultry carcasses into water sources, rivers, roadsides, and other places.
II. Disinfection
Flood disaster areas have suffered continuous heavy rainfall. Dead livestock and poultry and various pollutants flow with the water, and water sources and other environments are easily contaminated. At the same time, pathogens in the soil are washed out by rainwater, which can also trigger disease. To eliminate pathogens in the environment, cut off transmission routes, prevent and control the spread of infectious diseases, and protect human and animal health, large-scale disinfection must be carried out. Animal husbandry and veterinary departments in disaster areas should guide affected farms (households) in carrying out disinfection work, guide large-scale farms and breeding communities in implementing hygiene and disinfection measures, and prevent outbreaks.
(1) Disinfection scope
After floods, guide farms (households) in disaster areas to thoroughly clean and disinfect pens and the surrounding environment. First, clean the pen environment well, prevent wild animals from entering, and eliminate rats, mosquitoes, and flies; second, conduct a comprehensive disinfection of all pens. Disinfection should focus on livestock and poultry houses, slaughterhouses (points), livestock and poultry and their product processing and sales sites, warehouses, transit sites, livestock and poultry trading markets, drinking water sources, livestock and poultry transport vehicles, and utensils; especially thorough and repeated disinfection of pens where dead animals were kept.
1. Disinfection of pens and the environment: After the disaster, thoroughly clean and disinfect pens and the surrounding environment. First, disinfect collapsed pens, focusing on thorough disinfection of pens where dead animals were kept; second, disinfect farms that can continue to be used. Large farms should clean regularly and disinfect regularly with disinfectants, maintain pen cleanliness and environmental hygiene, prevent wild animals from entering, and eliminate rats, mosquitoes, and flies. For small farms and free-range households, the focus is on regularly cleaning pens and handling manure to maintain cleanliness. If an outbreak occurs, chemical disinfectants or disinfectant agents should be used for disinfection. Third, disinfect rebuilt pens. In addition to routine disinfection, after the disaster the number of disinfections should be increased according to the epidemic situation, and suitable disinfectants should be selected. Where conditions permit, build biogas pits to ferment manure and prevent mosquito and fly breeding.
2. Disinfection management of live livestock and poultry trading markets: Use low-irritation disinfectants to disinfect the body surfaces of livestock and poultry such as chickens and pigs, and clean and disinfect livestock and poultry trading venues, transport vehicles, and cages; establish a regular market closure and disinfection system.
(2) Commonly used disinfectants and methods of use
1. Quicklime: Suitable for brushing shed and pen walls, posts, and spreading on the ground for disinfection. Preparation of limewater: 1 kg quicklime plus 4-9 kg water. First place the quicklime in a bucket, add a small amount of water to dissolve it, then add the full amount of water. Limewater should be prepared and used immediately; if left for too long it will lose effectiveness.
2. Caustic soda: A 2% caustic soda solution can be used to disinfect sheds, pens, sites, utensils, and vehicles. A 3%-5% caustic soda solution can disinfect ground contaminated by anthrax spores. When disinfecting sheds and pens, drive (lead) livestock out of the pens, wait half a day, rinse the disinfected feed troughs, water troughs, cement floors, or wooden floors with water, then let the livestock back into the pens.
3. Peracetic acid: A 2%-5% peracetic acid solution can be sprayed to disinfect sheds, pens, sites, walls, utensils, vehicles and boats, and manure.
4. Compound phenol: A 100-300 times dilution of compound phenol is suitable for disinfecting livestock houses, sites, and pollutants.
5. Quaternary ammonium salts: A 3000 times dilution can be sprayed, rinsed, or soaked and used to disinfect livestock houses, environments, machinery, utensils, hatching eggs, etc. A 2000 times dilution of quaternary ammonium salts can be used for emergency preventive disinfection of livestock and poultry houses. A 10000-20000 times dilution of quaternary ammonium salts can prevent water storage towers and drinking fountains from being clogged by pollutants, and can kill microorganisms, remove algae, deodorize, and improve water quality.
In addition, disinfectants such as chlorine preparations, iodine preparations, and acid preparations (such as Miedusha, Shaduba, and Shadu Xianfeng may be selected) can be prepared according to the instructions and used to disinfect pen environments and equipment.
(3) Disinfection frequency
Ensure the frequency of disinfection. After a disaster, the environment should be disinfected at least twice a week, and pens may be disinfected 3-4 times a week with livestock and poultry present. Once an outbreak occurs, the number of disinfections should be increased, and the disinfection effect should be monitored.
Ensure the effective concentration of disinfectants; prevent mixing acid and alkaline disinfectants, which would affect the disinfection effect.
(4) Disinfection of workers
After workers complete harmless disposal work and disinfection work, the removed protective clothing, gloves, masks, etc. should be centrally incinerated; after contact with pollutants, use a waterless hand sanitizer to rub both hands, with a disinfection contact time of not less than 1 minute, then wash with water.
III. Immunization and monitoring for major animal diseases
Large-scale farms and households should, in light of actual prevention and control conditions, effectively carry out biosafety work for African swine fever and do a good job in supplementary vaccination for major animal diseases such as foot-and-mouth disease, highly pathogenic avian influenza, highly pathogenic porcine reproductive and respiratory syndrome, and classical swine fever. Livestock and poultry with unqualified immune antibodies should be promptly given supplementary vaccination.
(1) Strengthen immunization and effectively improve the resistance of livestock and poultry
Immunization is an effective measure for preventing and controlling major animal diseases such as foot-and-mouth disease, highly pathogenic porcine reproductive and respiratory syndrome, and highly pathogenic avian influenza. According to emergency monitoring results, promptly carry out supplementary and booster immunization against major animal diseases such as highly pathogenic porcine reproductive and respiratory syndrome, avian influenza, foot-and-mouth disease, and classical swine fever for livestock and poultry with low antibody levels, those about to exceed the immune protection period, and newly added animals. Focus on testing antibody levels in large-scale farms and households to ensure the immune antibody level of large-scale farms. In particular, strengthen immunization of sows and weaned piglets, and ensure all eligible animals are vaccinated. In light of local epidemic conditions, carry out emergency immunization in old epidemic areas, densely populated areas, and areas around temporary personnel resettlement sites. Actively carry out publicity on the Animal Epidemic Prevention Law and knowledge of animal disease prevention and control for grassroots epidemic prevention personnel and farmers, and effectively improve the epidemic prevention level of grassroots personnel and farmers' awareness of independent epidemic prevention.
(2) Strengthen monitoring and promptly eliminate hidden outbreak risks
Further increase the intensity of animal epidemic monitoring and epidemiological investigation in disaster-affected areas, and promptly discover and eliminate hidden risks. Focus on carrying out antibody testing for livestock and poultry in large-scale farms (households), areas where outbreaks have occurred, and other high-risk areas. If an outbreak is found, promptly collect samples and send them for testing, do a good job in monitoring and epidemiological investigation, and comprehensively analyze the causes of the outbreak. Based on monitoring results, animal husbandry and veterinary departments in disaster areas should strengthen supervision and inspection to ensure that all prevention and control measures are implemented; county- and township-level veterinarians responsible for designated areas should increase patrols of farms (households), report outbreaks promptly, and handle them promptly.
IV. Prevention of moldy feed poisoning and feeding management
(1) Prevention of moldy feed poisoning
Disaster areas have continuous heavy rain and high humidity, which easily causes feed to become moldy. Mold in moldy feed can cause poisoning in animals. After poisoning, animals generally have normal body temperature, dry feces, and vomiting symptoms. Sows become infertile and show abortion. Some show neurological symptoms, and severe cases die. There is bleeding in many parts of the body, including internal organs, and necrosis of the liver.
There is no effective treatment for moldy feed poisoning; prevention is key. It is strictly prohibited to feed spoiled, deteriorated, or moldy feed. Moldy feed can be centrally incinerated or returned to fields for treatment; pay attention to the shelf life of feed and prevent consumption of expired feed.
(2) Strengthen feeding management
First, promptly clear the drainage channels of livestock and poultry farms, remove standing water in livestock houses, and repair and reinforce damaged livestock houses. If they cannot be repaired in time, livestock and poultry should be moved to dry, safe areas as soon as possible. Second, create a good feeding environment, maintain hygiene in livestock houses, clean manure promptly, and do ventilation work well. Third, supply nutrient-rich feed and clean drinking water. Feed should be added in small amounts and frequently to avoid mold. Compound vitamin B and Vc can be added to drinking water to enhance the resistance of livestock and poultry, increase appetite, and eliminate stress. Fourth, strengthen the feeding of breeding livestock and poultry, do a good job in protecting the pregnancy of female animals, and for female animals that have miscarried, increase nutrition and breed promptly, while strengthening the care of young animals. Fifth, promptly cull young, weak, injured, disabled, and seriously ill livestock and poultry to reduce feeding costs. Commercial livestock and poultry that have reached the marketing standard should be marketed as soon as possible to reduce stocking density.
V. Technical measures for prevention and treatment of animal diseases after flood disasters
Animal diseases prone to occur during floods include Japanese schistosomiasis, anthrax, swine streptococcosis, leptospirosis, swine pasteurellosis, swine erysipelas, Japanese encephalitis, highly pathogenic porcine reproductive and respiratory syndrome, and African swine fever, etc.
(1) Japanese schistosomiasis
Japanese schistosomiasis is a zoonotic parasitic disease caused by Schistosoma japonicum parasitizing humans or mammals. The Ministry of Agriculture and Rural Affairs lists it as a Class II animal disease, and the National Health Commission lists it as a Class B human infectious disease.
1. Epidemic situation
The endemic areas of Japanese schistosomiasis in China can be divided into three types, namely the water-network type, the lake-marsh type, and the hilly type. Water-network type: located between the Yangtze River and the Qiantang River, namely the vast plain area of the Yangtze River Delta. Lake-marsh type: located on the beaches along both banks of the middle and lower reaches of the Yangtze River and the vast lake areas connected with the Yangtze River. Hilly type: mainly distributed in the mountainous and hilly areas of Sichuan and Yunnan provinces.
The feces of animals and patients with Japanese schistosomiasis contain viable eggs, which are the main source of infection of this disease. Pigs and dogs themselves are hosts and can become sources of infection. Mammals are almost all susceptible to Schistosoma japonicum. Cattle (water buffalo, yellow cattle) and sheep are the most susceptible, and humans are also susceptible. The disease is mainly contracted through contact of skin and mucous membranes with infected water. Infected Oncomelania snails release cercariae that contaminate water sources; water containing cercariae is called infected water, and humans and animals become ill after contact with infected water. Water-borne transmission is the main transmission route of schistosomiasis. The frequency and area of contact of various animals with infected water differ, so infection rates and degrees of infection also differ. The infection rate and degree of infection of the same animal species also differ in different regions.
2. Clinical symptoms
Clinical symptoms vary with the breed, age, and intensity of infection of the infected livestock. Generally, yellow cattle and dairy cattle are more obvious than water buffalo, equine animals, and pigs; goats are more obvious than sheep; and calves are more obvious than adult cattle. The main clinical symptoms are emaciation, rough coat, diarrhea, bloody stool, stunted growth, decreased plowing capacity of draft cattle, decreased milk production of dairy cows, infertility or abortion of female animals. A small number of affected animals, especially heavily infected calves and sheep, often have long-term diarrhea, bloody stool, rectal prolapse, pain, cessation of appetite, swaying gait, prolonged recumbency, slow breathing, and finally die of exhaustion.
Clinical symptoms of human schistosomiasis can be divided into acute, chronic, and advanced. Symptoms of acute schistosomiasis mostly occur in first-time infected persons; some people develop dotted red papules on the skin at the contact site, with intense itching. Symptoms of chronic schistosomiasis mainly manifest as chronic diarrhea or dysentery. Advanced schistosomiasis has several types: (1) ascitic type, ascites is one of the main signs of advanced schistosomiasis, (2) massive splenomegaly type, (3) dwarfism type, (4) colonic proliferation type. Common complications of advanced schistosomiasis include upper gastrointestinal bleeding and hepatic coma. Massive upper gastrointestinal bleeding and liver failure are the main causes of death.
3. Prevention and control measures
Implement key agricultural schistosomiasis control projects such as agricultural engineering snail control (converting paddy fields to dry land, paddy-upland rotation, hardening ditches and channels, and snail control through aquaculture) and livestock infection source management (penning livestock, replacing cattle with machinery, building biogas pits, and livestock screening and treatment), protect water sources and safe grazing, cut off the transmission route of schistosomiasis, and prevent and control schistosomiasis.
In epidemic areas, carry out disease screening by etiological or serological methods, or use serological methods for screening, then confirm positive animals found by etiological methods, and treat confirmed diseased animals with praziquantel or carry out universal treatment for all livestock exposed to infected water. Keep treatment records of diseased animals, compile them into volumes, and file them for reference.
4. Public health and personnel protection
In snail-infested areas of severe schistosomiasis epidemic areas, strengthen warning signs, eliminate grazing of livestock and contact of personnel with infected water, and if contact is unavoidable, personnel protection must be done well.
As long as people contact infected water, they may become infected with schistosomes and then develop the disease. The more times they contact infected water, the greater the possibility of infection with schistosomes. Farmers, fishermen, boatmen, and other groups engaged in production labor in schistosomiasis epidemic areas are more likely to be infected. In recent years, there have been populations flowing from epidemic areas to non-epidemic areas, from non-epidemic areas to epidemic areas, or from one epidemic area to another. When the above personnel develop symptoms such as rash, fever, abdominal pain, diarrhea, fatigue, and liver discomfort, they should actively seek examination. Children and housewives should stay away from infected water. Farmers engaged in production activities should wear protective equipment and use protective drugs. They should wear high rubber boots or protective clothing and gloves; all parts contacting infected water should be coated with protective drugs. At present, the main protective agents used include protective ointment, Pibidi, Fangyou cream, Fangyou pen, etc. Currently available oral drugs include praziquantel, artesunate, or artemether, which can kill schistosomula that have entered the body, with good preventive effects. Do a good job in feces treatment, prevent feces from contaminating water sources, and kill schistosome eggs in feces.
(2) Anthrax
Anthrax is a zoonotic infectious disease caused by Bacillus anthracis. The Ministry of Agriculture and Rural Affairs lists it as a Class II animal disease.
1. Diagnosis and epidemic characteristics
This disease is a zoonotic infectious disease, and various livestock, wild animals, and humans have varying degrees of susceptibility to it. Herbivores are the most susceptible, followed by omnivores, then carnivores; poultry generally do not become infected; humans are also susceptible.
This disease is endemic. It has a certain seasonality and mostly occurs in seasons with many blood-sucking insects, abundant rain, and frequent floods.
Diseased animals and animal carcasses that died of anthrax, as well as contaminated soil, grassland, water, and feed, are the main sources of infection of this disease. Anthrax spores have strong resistance to the environment, and contaminated soil, water sources, and sites can form persistent epidemic foci. This disease is mainly transmitted through the digestive tract, respiratory tract, and skin.
2. Clinical symptoms
This disease mainly has an acute course, mostly characterized by sudden death, bleeding from natural orifices, and incomplete rigor mortis.
Cattle: body temperature often rises above 41°C, visible mucous membranes are dark purple, tachycardia and difficulty breathing. In cattle with a chronic course, edema is common in the neck, chest, shoulder blades, under the abdomen, or external genitalia; skin lesions have increased temperature, are hard, and painful on pressure, and necrosis may also occur, sometimes forming ulcers; neck edema often occurs together with pharyngitis and laryngeal edema, worsening breathing difficulty. Acute cases generally die after 24-36 hours, and subacute cases generally die after 2-5 days.
Horses: body temperature rises, and edema is common under the abdomen, in the udder, shoulders, and throat. Tongue anthrax mostly shows difficulty breathing and cyanosis; intestinal anthrax has obvious abdominal pain. Acute cases generally die after 24-36 hours; when there is an anthrax carbuncle, the course can reach 3-8 days.
Sheep: mostly show peracute (sudden death) symptoms, swaying, teeth grinding, convulsions, struggling, and sudden collapse; in some cases, black-red blood with bubbles can be seen flowing from natural orifices. Those with a slightly longer course also survive only a few hours before death.
Pigs: mostly localized changes, with a chronic course, and clinical symptoms are not obvious; lesions are often seen after slaughter.
Dogs and other carnivores have no obvious clinical symptoms.
3. Outbreak handling
After local animal husbandry and veterinary departments receive a report of suspected anthrax, they should promptly send personnel to the site for epidemiological investigation and clinical examination, collect pathological materials and send them to a compliant laboratory for diagnosis, and immediately isolate suspected diseased animals and animals in the same group and restrict movement. For dead animal carcasses, dissection and examination are strictly prohibited; sampling must be carried out according to regulations to prevent pathogens from contaminating the environment and forming permanent epidemic foci.
When this disease occurs sporadically, diseased animals should be slaughtered without bleeding, animals in the same group should immediately receive compulsory vaccination, and be isolated and observed for 20 days. Dead animals and excreta, possibly contaminated feed, sewage, etc. should be harmlessly treated as required; possibly contaminated items, vehicles, utensils, and animal houses should be strictly and thoroughly disinfected. All susceptible animals in epidemic areas and threatened areas should receive emergency vaccination. Open dissection and examination of dead animal carcasses is strictly prohibited; sampling must be carried out according to regulations to prevent pathogens from contaminating the environment and forming permanent epidemic foci.
When this disease occurs as an outbreak (more than 5 diseased animals found within 10 days in 1 county), request the people's government at the same level to blockade the epidemic area; disinfection facilities must be set up at entrances and exits of epidemic points. Restrict the entry and exit of people, susceptible animals, and vehicles and the transport out of animal products and possibly contaminated items. Animal houses, sites, and all transport vehicles, drinking water utensils, etc. within epidemic points must be strictly and thoroughly disinfected. All diseased animals and animals in the same group shall be slaughtered without bleeding. Other susceptible animals shall receive emergency vaccination. All dead animals, culled animals, excreta, and possibly contaminated bedding, feed, and other items and products shall be harmlessly treated as required. When animal carcasses need to be transported, leak-proof containers shall be used, with obvious markings, and implemented under the supervision of animal disease prevention and control institutions. Trade in and movement of animals and their products in the epidemic area shall be stopped. All susceptible animals must be penned or grazed at designated locations; animal houses, roads, and other possibly contaminated sites shall be disinfected. Emergency vaccination shall be carried out for all susceptible animals in the epidemic area and threatened area, and source analysis and epidemiological investigation shall be carried out.
4. Prevention and control measures
First, environmental control. Breeding, production, and business sites and slaughterhouses must meet the animal epidemic prevention conditions stipulated in the Measures for Review of Animal Epidemic Prevention Conditions and establish strict hygiene (disinfection) management systems. Second, vaccination. Each province shall, according to local epidemic conditions and the immunization plan formulated by the Ministry of Agriculture and Rural Affairs, determine the targets and scope of vaccination; use nationally approved anthrax vaccines, carry out timely vaccination according to immunization procedures, and keep immunization records. Third, disinfection to eliminate sources. Carry out regular disinfection in new and old epidemic areas, with key disinfection during floods. Hides, wool, etc. shall be disinfected as required.
5. Personnel protection
Personnel engaged in animal epidemic prevention and quarantine, laboratory diagnosis, and work in farms, livestock product and hide processing enterprises should pay attention to personal protection. Relevant personnel participating in outbreak handling should wear protective clothing, masks, and gloves, and protect themselves well. Hides shall be disinfected with ethylene oxide under high pressure in a sealed manner.
(3) Swine streptococcosis
Swine streptococcosis is a zoonosis caused by hemolytic streptococci, and the Ministry of Agriculture and Rural Affairs lists it as a Class II animal disease.
1. Diagnosis and epidemic characteristics
Pigs of different ages, breeds, and sexes are all susceptible, and humans can also be infected.
Streptococci often exist in the respiratory tract, digestive tract, and reproductive tract of normal animals and humans. Pathogens are present in the excreta, secretions, blood, internal organs, and joints of infected and diseased animals.
Diseased pigs and carrier pigs are the main sources of infection of this disease. Improper disposal of dead pigs and contamination of transport vehicles are important factors causing the spread of this disease.
This disease is mainly transmitted through the digestive tract, respiratory tract, and damaged skin. It can occur throughout the year, and is more common in summer and autumn. It is endemic; new epidemic areas may show outbreaks, with higher morbidity and mortality. Old epidemic areas mostly show sporadic cases, with lower morbidity and mortality.
2. Clinical symptoms
It can manifest as septicemic, meningitis, and lymph node abscess types, etc.
Septicemic type: divided into peracute, acute, and chronic categories. The peracute type has a sudden onset and short course, often with sudden death without any symptoms. Body temperature reaches as high as 41-43°C, breathing is labored, and most die of septicemia within 24 hours. The acute type mostly occurs suddenly, with body temperature rising to 40-43°C, labored breathing, dry nasal mirror, and serous or purulent discharge flowing from the nasal cavity. Conjunctiva is congested and there is lacrimation. The skin of the neck, ear margins, under the abdomen, and lower ends of the limbs is purplish red with bleeding points. Most die within 1-3 days. The chronic type manifests as polyarthritis. Joints swell, lameness or paralysis occurs, and finally death is caused by weakness and paralysis.
Meningitis type: mainly meningitis, more common in piglets. It mainly manifests as neurological symptoms, such as teeth grinding, foaming at the mouth, circling movement, convulsions, lying down with limbs paddling as if swimming, and finally death from paralysis. The course may be as short as a few hours or as long as 1-5 days, and the mortality rate is extremely high.
Lymph node abscess type: characterized by suppuration and abscess formation in lymph nodes under the jaw, in the pharynx, and in the neck, etc.
3. Outbreak handling
When a suspected swine streptococcosis outbreak is found, the local animal husbandry and veterinary department should promptly send personnel to the site for epidemiological investigation, clinical symptom examination, etc., and collect samples for testing. When confirmed as a suspected swine streptococcosis outbreak, prevention and control measures such as isolation and movement restriction should be immediately taken.
When this disease occurs sporadically, diseased pigs should be slaughtered without bleeding, pigs in the same group should immediately receive compulsory vaccination or drug prevention, and be isolated and observed for 14 days. When necessary, pigs in the same group should be culled. Culled pigs, dead pigs and excreta, possibly contaminated feed, sewage, etc. shall be harmlessly treated according to relevant regulations; possibly contaminated items, vehicles, utensils, and livestock houses shall be strictly and thoroughly disinfected. All susceptible animals nearby shall receive emergency vaccination.
When this disease occurs as an outbreak (more than 50 diseased pigs found within 30 days in one township, or occurrence in more than 2 townships), diseased pigs within the epidemic point should be slaughtered without bleeding, pigs in the same group should immediately receive compulsory vaccination or drug prevention, and be isolated and observed for 14 days. When necessary, pigs in the same group should be culled. Dead pigs and excreta, possibly contaminated feed, sewage, etc. shall be harmlessly treated according to the requirements of the annex; possibly contaminated items, vehicles, utensils, and livestock houses shall be strictly and thoroughly disinfected. Animal health supervision and inspection stations shall be established at major traffic routes, with dedicated personnel supervising the movement of animals and their products, and entering and exiting personnel and vehicles must be disinfected. Trade, slaughter, transport, and movement of live pigs in the epidemic area shall be stopped. Livestock houses, roads, and other possibly contaminated sites shall be disinfected. For healthy pigs in the same group within the epidemic point and pigs within the epidemic area, highly sensitive antibacterial drugs may be used for emergency preventive administration. All pigs in the epidemic area and threatened area shall receive emergency vaccination according to the instructions.
Pig excreta and contaminated or possibly contaminated bedding, feed, and other items all need harmless treatment. When transporting pig carcasses, leak-proof containers should be used.
4. Personnel protection
Relevant personnel participating in outbreak handling should wear protective clothing, rubber boots, masks, and gloves, and protect themselves well.
(4) Leptospirosis
Leptospirosis (lepto disease) is a zoonosis caused by pathogenic Leptospira (abbreviated as leptospira), commonly known as “threshing jaundice” and “rice-field fever”. The Ministry of Agriculture and Rural Affairs lists it as a Class II animal disease, and the National Health Commission lists it as a Class B human infectious disease.
1. Epidemic situation
Except for Xinjiang, Qinghai, Gansu, and Ningxia, all other provinces and cities across the country have reported cases of leptospirosis, with more severe cases in the central-south, southwest, and east China regions that are rich in rice production. During the rice harvest season and flood relief efforts, because more people contact water contaminated with leptospira, large-scale epidemics often occur.
The hosts of leptospira are very extensive. Domestic animals such as pigs, dogs, cattle, sheep, and horses, and wild animals such as rats, wolves, rabbits, snakes, and frogs can all become sources of infection. Rats and pigs are the two major sources of infection. In southern and southwestern China, carrier rats are the main source, while in the north and coastal plains, pigs are the main source.
Leptospira can survive for a long time in slightly alkaline water containing certain humus (such as rice field water) and silt, and it is a water-borne disease. After animals are infected, the pathogen can be excreted through the kidneys with urine, contaminating water sources, soil, feed, cattle sheds, and utensils. This disease is transmitted through the skin, mucous membranes, and digestive tract, and can also be transmitted through mating, artificial insemination, and during bacteremia through blood-sucking insects. It is generally endemic or sporadic, more common in summer and autumn, and young animals are more susceptible than adult animals and have more severe disease.
When people contact water contaminated with leptospira during production labor or daily life, the pathogen can enter the human body through the skin (especially broken skin) and mucous membranes, causing human disease. Direct contact infection refers to infection when people directly contact pathogens on animals during feeding, slaughtering, processing, and transporting animals. Occasionally there are reports of mother-to-child vertical transmission, but human-to-human transmission is of little significance.
Almost all animals can be infected. Rats are the most susceptible and are also the most important reservoir host. Next are pigs, water buffalo, cattle, and ducks, followed by sheep, horses, camels, rabbits, and cats. Poultry can also be infected. Humans are generally susceptible to leptospirosis. Residents of non-epidemic areas entering epidemic areas are especially susceptible.
This disease is a naturally focus-borne infectious disease. Cases are relatively concentrated during summer and autumn rice harvest or after heavy rain and floods, and in areas with higher temperatures it can be seen year-round. This disease is more common in young and middle-aged farmers. Other fishermen, miners, slaughterhouse workers, and breeders who have more opportunities to contact water contaminated with leptospira can also develop the disease.
2. Clinical symptoms
The clinical features of acute cases mainly include short-term fever, anemia, jaundice, hemoglobinuria, and necrosis of mucous membranes and skin. However, most animals have inapparent infection and lack obvious clinical symptoms.
Cattle: In China, 9 serovars of Leptospira have been isolated from cattle, mainly the Pomona group, followed by the Icterohaemorrhagiae group. They often lack typical symptoms, with only emaciation and diarrhea seen. Typical cases have an acute course, with body temperature above 40.5-41°C at the beginning. Depression, complete loss of appetite, dry and even cracked nasal mirror, and progressive emaciation. Milk production decreases or stops, milk color turns yellow like colostrum, and often has blood clots. In some cases, 2-3 days after abortion, visible mucous membranes become yellow-stained, and hemoglobinuria appears at the same time. Diseased cattle often develop necrosis of the skin on the oral mucosa, ears, head, udder, and external genitalia. Chronic cases show intermittent fever, and diseased cattle gradually become emaciated, with jaundice and hemoglobinuria appearing and disappearing intermittently.
Pigs: Leptospirosis in pigs is relatively common. In China, 14 serovars have been isolated from pigs, mainly the Pomona group, followed by the Canicola group. Most have no obvious clinical symptoms. Acute cases are more common in piglets, showing short-term fever (around 39.8-41°C) and conjunctivitis. Depression, reduced appetite, yellow-stained visible mucous membranes, and head edema. Skin elasticity decreases, and skin necrosis appears in the later stage, with urine from light yellow to brown. Sows in late pregnancy often have abortion and stillbirth.
Horses: Most are inapparent infections, and acute cases are relatively few. The symptoms of acutely diseased horses are similar to those of cattle, mainly showing elevated body temperature, depression, conjunctivitis, and yellow-stained visible mucous membranes. Urine volume is small, urine is viscous, and appears yellow-red like soybean oil. Pregnant horses abort, hemoglobin decreases, white blood cell count increases, neutrophils increase, and there is a left shift.
Humans: The incubation period is 2-20 days, generally 7-13 days. The course can be divided into three stages: the early stage “severe cold-like” syndrome, with “three symptoms”, namely chills and fever, muscle aches, and general fatigue; and three signs, namely conjunctival congestion, calf muscle tenderness, and lymph node enlargement. The middle stage can be divided into four types: influenza-typhoid type, massive pulmonary hemorrhage type, jaundice-hemorrhage type, and meningoencephalitis type. Varying degrees of organ damage will appear, such as epistaxis, hemoptysis, diffuse pulmonary hemorrhage, skin and mucous membrane jaundice or bleeding points; patients with the renal type develop proteinuria, hematuria, casts, and other renal function damage; patients with the meningoencephalitis type develop severe headache, vomiting, neck stiffness, and changes in cerebrospinal fluid composition. Within 6 months after fever subsides in the acute phase (in individual cases up to 9 months), some symptoms or manifestations of organ damage appear again. Common sequelae include post-fever, post-ocular complications, and allergic meningitis. The pathological basis of leptospirosis patients is toxic damage to systemic capillaries. Large numbers of leptospira invade internal organs such as the lungs, liver, kidneys, heart, and central nervous system, causing organ damage and corresponding organ complications. The severity of the disease is related to the serovar, bacterial load, and virulence of leptospira. Highly virulent leptospira can cause severe manifestations such as pulmonary hemorrhage or jaundice hemorrhage.
3. Differential diagnosis
Make a preliminary diagnosis based on clinical symptoms, epidemiological investigation, and pathological change characteristics; confirmation requires laboratory diagnosis.
It should be distinguished from piroplasmosis, postpartum hemoglobinuria, bacterial hemoglobinuria, equine infectious anemia, and jaundice and abortion caused by other pathogens.
4. Prevention and control measures
Animals can be treated with penicillin; other drugs such as streptomycin, chloramphenicol, and gentamicin also have good efficacy against this disease. In addition, neoarsphenamine also has good efficacy.
Carry out mass comprehensive preventive measures. Rodent control and vaccination are the key to controlling leptospirosis outbreaks and reducing incidence. Carry out mass movements to eliminate rodents to protect grain and eliminate rodents to prevent disease. In conjunction with the work of “two management (water, feces) and five improvements (water wells, toilets, livestock pens, stoves, environment)”, especially promote penning pigs for manure accumulation and urine and feces management, so as to prevent contamination of water sources, rice fields, ponds, and rivers. Pay attention to drinking water hygiene, isolate diseased animals, and strictly prevent urine of diseased animals from contaminating drinking water and feed. Residents, troops, and personnel participating in harvesting, flood control, and drainage in epidemic areas who may contact infected water should, as far as possible, be vaccinated 1 month in advance with multivalent leptospira vaccine of the same serovar as the local epidemic serovar. In areas where the disease often occurs, leptospira vaccine can be administered. Eliminate rats and stray dogs. For high-risk susceptible persons such as pregnant women, children and adolescents, the elderly, or laboratory personnel who accidentally contact leptospira and are suspected of infection but have no obvious symptoms, penicillin may be injected at 800,000-1,200,000 U per day for 2-3 consecutive days.
5. Public health and personal protection
This disease is a naturally focus-borne infectious disease. Carrier animals can excrete bacteria into the environment for a long time. When susceptible animals and humans contact the pathogen, they can become infected. In rice-producing areas of China, cases have always occurred, especially with flood disasters, often causing outbreaks. For the masses in disaster areas, the main prevention of leptospirosis is deratization (such as chemical rodent control), rodent proofing (such as farmland improvement), and management of livestock to reduce environmental contamination (such as penning pigs). Try to avoid contact with infected water, such as draining and drying the fields before harvesting rice. When necessary, carry out leptospirosis vaccination and take oral drug prevention, etc. Fishermen, miners, slaughterhouse workers, breeders, and other high-risk groups with more opportunities to contact infected water, as well as personnel entering leptospirosis epidemic areas to carry out on-site work, should avoid contact with infected water. When investigating the density and carrier rate of animal hosts, pay attention to wearing protective gloves and do not directly touch animals or their carcasses with hands. When necessary, vaccinate against leptospirosis 15 days before entering the epidemic area for work, or take doxycycline orally as emergency prevention against leptospirosis infection.
(5) Swine pasteurellosis
Swine pasteurellosis (swine pasteurellosis) is an acute infectious disease caused by Pasteurella multocida.
1. Epidemic characteristics
Pasteurella multocida can infect many kinds of animals, and pigs are one of them. Pigs of all ages can be infected and develop the disease, and the incidence is higher in piglets and growing pigs. Diseased pigs and healthy carrier pigs are sources of infection. The pathogen is excreted from the body with secretions and excreta and transmitted through the respiratory tract, digestive tract, and damaged skin. When carrier pigs are exposed to cold, catch cold, are overworked, or are improperly managed, and their resistance decreases, endogenous infection from within the body can occur. Swine pasteurellosis is often sporadic. When pigs are in adverse external environments, such as cold, stuffy heat, drastic climate changes, humidity, crowding, poor ventilation, nutritional deficiency, fatigue, and long-distance transport, their resistance decreases, and the pathogen multiplies in large numbers and causes disease. In addition, diseased pigs excrete bacteria through secretions and excreta, contaminating drinking water, feed, utensils, and the external environment and transmitting to healthy pigs through the digestive tract, which is also an important route of infection. The pathogen can also be excreted through coughing and sneezing and transmitted through droplets via the respiratory tract. In addition, bites by blood-sucking insects and wounds on the skin and mucous membranes can also transmit it. This disease generally has no obvious seasonality, but is more common when cold and heat alternate, when the climate changes frequently, and in high-temperature seasons in flood disaster areas, and generally occurs sporadically or endemically.
This disease commonly affects growing and young pigs; throughout the year, it occurs most often in late autumn, early spring, and seasons with sudden climate changes. In the south, it is prone to occur in the humid and stuffy months from May to September, appearing as epidemic swine pasteurellosis.
2. Clinical symptoms
The incubation period of this disease is 1-5 days, generally about 2 days. The main symptoms are markedly elevated body temperature (42.2°C), complete loss of appetite, extreme difficulty breathing, persistent coughing, purulent conjunctivitis of the visible mucous membranes, first constipation then diarrhea, red spots appearing at the base of the ears, on the ventral sides, and on the inner sides of the limbs, with mortality as high as 50%. Clinical symptoms are divided into peracute, acute, and chronic types. The peracute type is more common in the early stage of an epidemic and often causes sudden death. In those with a slightly longer course, body temperature rises (40-42°C), appetite is completely lost, the whole body is weak, and the animal lies unable to stand. Conjunctiva is congested and cyanotic. Red spots appear on the skin at the base of the ears, neck, ventral sides, and lower abdomen, and do not completely fade on finger pressure. The most characteristic symptom is redness, swelling, heat, and pain in the throat, with acute inflammation; in severe cases, local swelling can extend to the base of the ears and neck. Breathing is extremely difficult, with bloody foam from the mouth and nose, and most die of suffocation after 1-2 days. The acute type mainly shows fibrinous pleuropneumonia. In addition to septicemic symptoms, body temperature rises to 40-41°C at the beginning, with spasmodic dry cough, nasal discharge, and purulent conjunctivitis. Initially constipation, later diarrhea. Difficulty breathing, often in a sitting-dog posture, chest palpation is painful, and auscultation reveals rales and friction sounds. Most die of suffocation. The course is 4-6 days; those that do not die turn chronic. The chronic type mainly shows chronic pneumonia or chronic gastroenteritis. Diseased pigs have persistent cough, difficulty breathing, and sticky or purulent nasal discharge, and auscultation of the chest reveals rales and friction sounds. Joints swell. Diarrhea occurs intermittently, with progressive malnutrition and extreme emaciation, and finally most die of exhaustion; the course is 2-4 weeks.
3. Differential diagnosis
The peracute cases of this disease often die suddenly, and the symptoms and lesions of chronic cases are atypical and often involve mixed infection with other diseases. Diagnosis based solely on epidemiology, clinical symptoms, and pathological changes is difficult to confirm. It should be analyzed and judged based on comprehensive data from epidemiology, symptoms, pathological changes, and bacteriological examination. Pay attention to distinguishing it from classical swine fever and swine erysipelas. In peracute cases, swelling and inflammation of the throat and gelatinous infiltration at necropsy are similar to septicemic anthrax, but acute anthrax in pigs rarely occurs and does not form an epidemic. At necropsy, splenic enlargement in anthrax differs from swine pasteurellosis. If local pathological materials are taken for bacteriological examination, the pathogen morphology and other features of the two are obviously different, making them easy to distinguish.
4. Prevention and control measures
Some healthy pigs carry Pasteurella in their upper respiratory tracts, and under the action of adverse factors, this can often induce the disease. Therefore, the fundamental way to prevent this disease is to implement the policy of “prevention first”, eliminate all adverse factors that reduce pig resistance, strengthen feeding management, and do animal epidemic prevention work well to enhance pig resistance; carry out regular preventive injections every spring and autumn to enhance specific resistance of pigs.
When the disease occurs, isolate diseased pigs and treat promptly. Diseased pigs can be treated with aqueous penicillin 400,000 units by intramuscular injection, 2-3 times a day, for 3-5 consecutive days. Streptomycin 1 g, divided into 2 intramuscular injections daily. 20% sodium sulfathiazole or sodium sulfadiazine injection, 10-15 mL for piglets and 20-30 mL for adult pigs, by intramuscular or intravenous injection, twice daily, for 3-5 consecutive days.
Do a good job in disinfection and care in flood-affected areas. The walls, floors, and feeding management utensils of pig houses should be disinfected, and manure waste should be piled for fermentation; when necessary, in apparently healthy pigs in affected groups, swine pasteurellosis antiserum can be used for emergency preventive injection at half the therapeutic dose; small runt pigs with chronic swine pasteurellosis are better culled.
(6) Swine erysipelas
Swine erysipelas is an acute febrile infectious disease caused by Erysipelothrix rhusiopathiae.
1. Epidemic characteristics
Swine erysipelas occurs throughout the year. Diseased pigs and carrier pigs are the source of infection of this disease. Erysipelothrix rhusiopathiae mainly exists in the tonsils, gallbladder, glands of the ileocecal valve, and bone marrow of carrier pigs. Diseased pigs and carrier pigs excrete Erysipelothrix rhusiopathiae in feces and urine, contaminating feed, drinking water, soil, utensils, and barns, and transmit it to susceptible pigs through the digestive tract. The disease can also be transmitted through damaged skin and blood-sucking insects such as mosquitoes and flies.
2. Clinical symptoms
It is divided into acute and chronic types. Acute septicemic swine erysipelas commonly has body temperature rising to 42-43°C, persistent fever, weakness, no eating, and sometimes vomiting. Feces are dry and hard like millet, with mucus attached; piglets may have diarrhea in the later stage. Severe cases have rapid breathing, cyanotic mucous membranes, and some diseased pigs have flushed and purplish skin on the ears, neck, back, etc. Cases with a short course may die suddenly, with a mortality rate of about 80%. Chronic swine erysipelas commonly has skin necrosis, often occurring on the back, shoulders, ears, hooves, and tail, with local skin swelling, raised, black, dry and hard, resembling leather. After 2-3 months, the necrotic skin falls off, leaving a hairless scar. Chronic arthritis manifests as swelling of limb joints, with the carpal joint more common, and the affected leg is stiff and painful, with lameness or inability to stand. Breathing is rapid, and usually the animal suddenly falls dead due to cardiac paralysis.
3. Prevention and control measures
Strengthen feeding management, keep pig house utensils clean, and disinfect regularly with disinfectants. Carry out preventive vaccination according to plan every year. At present, vaccines used to prevent and control this disease include attenuated vaccines and inactivated vaccines. Immunization of suckling piglets may be affected by maternal antibodies, so it should be carried out after weaning; if immunization has been carried out during the suckling period, another immunization should be carried out after weaning, and then once every 6 months. Do a good job in eliminating mosquitoes, flies, fleas, and lice in pig houses.
After swine erysipelas is detected, diseased pigs should be isolated immediately and treated early. Pig pens, exercise yards, feed troughs, and utensils should be carefully disinfected. Feces and bedding straw are best burned or piled for fermentation for biological heat treatment. After a swine erysipelas outbreak occurs, the temperature of the whole herd should be measured immediately, diseased pigs should be isolated and treated, and dead pigs should be deeply buried or burned. For unaffected pigs in the same group as diseased pigs, penicillin should be used for drug prevention, and after the outbreak is extinguished and medication is stopped, one major disinfection should be carried out.
After isolating and handling affected pig groups, normal pigs should be injected with swine erysipelas vaccine to consolidate the epidemic prevention effect. Chronically diseased pigs should be culled early to reduce economic losses and prevent carrier transmission.
(7) Japanese encephalitis
Porcine Japanese encephalitis (also known as epidemic Japanese encephalitis, Japanese encephalitis) is an acute, zoonotic, naturally focus-borne infectious disease of the central nervous system caused by Japanese encephalitis virus. Mosquitoes are the transmission vector, and pigs are characterized by abortion, stillbirth, and orchitis. The Ministry of Agriculture and Rural Affairs lists it as a Class II animal disease, and the National Health Commission lists it as a Class B human infectious disease.
1. Epidemic situation
China is the country with the highest incidence of Japanese encephalitis, accounting for more than 80% of total cases worldwide. So far, except for Xinjiang, Qinghai, and Tibet, where no Japanese encephalitis cases have been reported, all other provinces and cities have had Japanese encephalitis cases. Japanese encephalitis is a naturally focus-borne disease with obvious seasonality, mostly occurring in the mosquito breeding and activity season from July to September. Apart from sporadic occurrence year-round in tropical regions, subtropical and temperate regions have strict seasonality, with the vast majority of cases concentrated in July, August, and September, accounting for about 80-90% of annual cases. In central China, the epidemic peak is in July-August; in south China it is one month earlier, and in north China one month later. The epidemic characteristics in pig herds are high infection rate and low incidence, generally inapparent infection, and the vast majority do not relapse after recovery and become virus-carrying pigs. Generally speaking, the peak of natural infection in pigs is 3-4 weeks earlier than the epidemic peak of human Japanese encephalitis.
The main sources of infection of porcine Japanese encephalitis are virus-carrying animals, among which pigs and horses are the most important animal hosts and sources of infection. Horses are natural hosts of the virus, and pigs are amplifying hosts and sources of infection. The virus circulates through mosquito → pig → mosquito, causing Japanese encephalitis virus to spread continuously. Birds are also important reservoir hosts of this virus. After infection, birds can produce relatively high-titer viremia. In Japan, antibodies to Japanese encephalitis virus have been found in the blood of many kinds of birds, and Japanese encephalitis virus has been isolated from nestling grey herons. In addition to pigs and birds, cattle, sheep, bats, and other animals can all be infected with Japanese encephalitis virus and become reservoir hosts and sources of infection of this virus.
It is mainly transmitted through bites by mosquitoes (Culex, Aedes, Anopheles, etc.), among which Culex tritaeniorhynchus is the most important. Overwintering mosquitoes can transmit the virus across years, and the virus may also be passed to the next generation through mosquito eggs. The virus transmission cycle is repeated between overwintering animals and susceptible animals through mosquito bites. Pigs can also transmit vertically to fetuses through the placenta.
Equine animals, pigs, cattle, sheep, chickens, and wild birds can all be infected. Horses are the most susceptible. Pigs of all breeds and sexes are susceptible, with young animals being the most susceptible. Humans are also susceptible, mainly through bites by vector insects such as mosquitoes (Culex tritaeniorhynchus). It generally mainly affects children under 10 years old, accounting for more than 80% of total patients; most adults have inapparent infection.
2. Clinical symptoms and diagnosis
The incubation period of artificial infection is generally 3-4 days. Diseased pigs show elevated body temperature, depression, lethargy, and decreased appetite. Body temperature rises to 40-41°C, showing persistent fever. Depression, reduced appetite, and conjunctival congestion. When pregnant sows are affected, abortion and premature birth often occur suddenly, with stillbirth or mummified fetuses. Abortion mostly occurs in late pregnancy; at abortion, the udder swells and milk flows out, and retained placenta is common, with red-brown or gray-brown mucus flowing from the vagina. Piglets develop convulsive symptoms and die within a few days after birth, or become runt pigs. Boars have no obvious symptoms but may develop orchitis.
In affected horses, body temperature rises in the early stage, movement is reduced, and appetite decreases. In severe cases, the animal stands unsteadily, with limbs paddling as if swimming. Some horses are excited and manic. Generally, depression, excitement, and paralysis symptoms appear successively or alternately.
Human Japanese encephalitis mostly occurs in children under 10 years old. The incubation period is 4-21 days, generally 10-14 days. Clinical symptoms mainly include acute onset, fever, headache, projectile vomiting, and after 2-3 days of fever, varying degrees of consciousness disturbance. Severe patients may develop central nervous system symptoms such as generalized convulsions, tonic spasms, or paralysis, and severe cases develop central respiratory failure.
A preliminary diagnosis can be made based on clinical symptoms and pathological changes; confirmation requires further laboratory diagnosis. Differential diagnosis should be made with pseudorabies, parvovirus, classical swine fever, and other diseases.
3. Prevention and control measures
Vaccinate pig herds with attenuated Japanese encephalitis vaccine 1-2 months before the Japanese encephalitis epidemic season. Strengthen animal feeding management, improve animal resistance, carry out regular environmental disinfection, and mosquito elimination and prevention work to reduce disease occurrence.
When a Japanese encephalitis outbreak occurs, adopt strict control and eradication measures to prevent disease spread. Diseased animals shall be culled and harmlessly treated. Dead pigs, aborted fetuses, fetal membranes, and amniotic fluid must all be harmlessly treated. Contaminated sites and utensils should be thoroughly disinfected.
4. Public health and personnel protection
In rural areas and farms, do a good job in pig feeding environmental hygiene and vaccination, and reduce the epidemic of human Japanese encephalitis through control of porcine Japanese encephalitis. Farm workers, veterinarians, laboratory personnel, etc. should wear protective equipment such as protective clothing, masks, and gloves before contacting diseased animals or virus-contaminated materials. After work is completed, all protective equipment should be removed on site, cleaned and disinfected, and disposable items should be harmlessly treated. Age-eligible populations and relevant workers in Japanese encephalitis epidemic areas should be vaccinated against Japanese encephalitis.
(8) Highly pathogenic porcine reproductive and respiratory syndrome
Highly pathogenic porcine reproductive and respiratory syndrome is an acute, highly lethal disease caused by a variant strain of porcine reproductive and respiratory syndrome (commonly known as blue ear disease) virus. The Ministry of Agriculture and Rural Affairs lists it as a Class I animal disease.
1. Epidemic characteristics
The infection rate of porcine reproductive and respiratory syndrome virus in pig herds in China is very high, with the antibody positive rate in pig herds at 10%-88%. At present, persistent infection of porcine reproductive and respiratory syndrome virus on pig farms is an important epidemiological feature of this disease. It can survive for a long time in the serum, lymph nodes, spleen, lungs, and other tissues of infected pigs and can excrete virus into the environment. Older pigs and breeding pigs show inapparent infection. In China, the phenomenon of breeding pigs carrying the virus is relatively serious. Porcine reproductive and respiratory syndrome virus can often be detected from sow blood and boar semen, and the virus can be transmitted through the placenta and semen. Virus-carrying sows and infected sows can show estrus disorders, such as delayed estrus and failure to come into estrus.
2. Clinical symptoms
Body temperature is markedly elevated, reaching above 41°C; conjunctivitis and eyelid edema; respiratory symptoms such as coughing and panting; some pigs have neurological symptoms such as weakness of the hindquarters, inability to stand, or ataxia; the incidence in piglets can reach 100%, mortality can reach more than 50%, the abortion rate of sows can reach more than 30%, and adult pigs can also develop disease and die.
3. Outbreak handling
Any unit or individual that discovers acute disease and death in pigs should promptly report to the local animal disease prevention and control institution. After receiving the report or learning of a clinically suspected outbreak, the local animal disease prevention and control institution should immediately send personnel to the site for preliminary investigation and verification, and collect samples for laboratory diagnosis to confirm the outbreak.
When judged as a suspected outbreak, isolation and monitoring should be implemented for the affected farm/household, the movement of live pigs and their products and related items shall be prohibited, and strict disinfection measures shall be implemented for the internal and external environment. Dead pigs, pollutants, or suspected pollutants shall be harmlessly treated. When necessary, diseased pigs and pigs in the same group shall be culled and harmlessly treated.
After the outbreak is confirmed, the veterinary competent department at or above the county level in the locality shall delineate the epidemic point, epidemic area, and threatened area. Within the epidemic point, cull all diseased pigs and pigs in the same group; harmlessly treat dead pigs, excreta, contaminated feed, bedding, sewage, etc.; thoroughly disinfect contaminated items, vehicles, utensils, pig houses, sites, etc. Within the epidemic area, thoroughly disinfect contaminated items, vehicles, utensils, pig houses, sites, etc.; carry out emergency booster immunization for all live pigs with inactivated highly pathogenic porcine reproductive and respiratory syndrome vaccine, and strengthen outbreak monitoring. For all live pigs in threatened areas, carry out emergency booster immunization with inactivated highly pathogenic porcine reproductive and respiratory syndrome vaccine, and strengthen outbreak monitoring.
4. Prevention and control measures
Strengthen monitoring. Carry out key monitoring of live pigs in high-risk areas such as breeding pig farms, isolation facilities, border areas, and areas where outbreaks have recently occurred or occur frequently. Animal disease prevention and control institutions at all levels shall conduct risk analysis on monitoring results and related information and do a good job in early warning and forecasting. Laboratories designated by the Ministry of Agriculture and Rural Affairs shall analyze and evaluate the biological and molecular biological characteristics of isolated strains.
Improve immunization quality. Immunize all live pigs with inactivated highly pathogenic porcine reproductive and respiratory syndrome vaccine. When a highly pathogenic porcine reproductive and respiratory syndrome outbreak occurs, use inactivated highly pathogenic porcine reproductive and respiratory syndrome vaccine for emergency booster immunization. Animal disease control institutions at all levels shall regularly monitor the immune antibody levels of immunized pig herds and promptly strengthen immunization according to the rise and fall of herd antibody levels.
Strengthen feeding management, implement closed raising, establish and improve various epidemic prevention systems, and do a good job in disinfection, insect extermination, and rodent control.
(9) African swine fever
African swine fever is an acute, severe, highly contagious infectious disease caused by African swine fever virus. The morbidity and mortality rates are as high as 100%. Domestic pigs, wild boars, and Ornithodoros soft ticks infected with African swine fever virus are the main sources of infection. The Ministry of Agriculture and Rural Affairs lists it as a Class I animal disease.
1. Epidemic characteristics
African swine fever is the greatest threat to the production safety of China's live pig industry. At present, the virus has become established in China and formed a relatively large contaminated area, and the risk of outbreak is very high. The transmission route of African swine fever is mainly through contact with pigs infected with African swine fever virus or African swine fever virus contaminants (kitchen waste, feed, drinking water, pens, bedding, clothing, utensils, vehicles, etc.). The digestive tract and respiratory tract are the most important routes of infection; it can also be transmitted through bites by vector insects such as Ornithodoros soft ticks. The risk of aerosol transmission of African swine fever is very low. Domestic pigs and Eurasian wild boars are highly susceptible, with no obvious differences in breed, age, or sex. The seasonality of African swine fever is not obvious.
2. Clinical symptoms
African swine fever incubation period, morbidity, and mortality: due to differences in virus strain, host, and route of infection, the incubation period varies, generally 5-19 days, with a maximum of up to 21 days. The morbidity and mortality of pigs infected with highly virulent strains can both reach 100%; the mortality caused by moderately virulent strains is generally 30%-50%, and low-virulence strains cause death in only a small number of pigs.
Clinical manifestations are divided into peracute, acute, subacute, and chronic.
Peracute: sudden death without obvious clinical symptoms.
Acute: body temperature can reach as high as 42°C, depression, anorexia, bleeding points on the skin of the ears, limbs, and abdomen, splenic enlargement, and mucous-purulent discharge from the eyes and nose; vomiting; diarrhea with blood in the feces. Ataxia or stiff gait, difficulty breathing, and other neurological symptoms such as paralysis and convulsions. Pregnant sows abort. Mortality can reach 100%. The course is 4 to 10 days.
Subacute: symptoms are the same as acute, but the disease is milder and mortality is lower. Body temperature fluctuates irregularly, generally above 40.5°C. Piglet mortality is relatively high. The course is 5 to 30 days.
Chronic: undulant fever, difficulty breathing, and wet cough. Emaciation or retarded development, weakness, and dull coat color. Joint swelling and skin ulcers. Mortality is low. The course is 2 to 15 months.
3. Pathological changes
The typical pathological changes are enlargement and friability of the spleen, dark red to black, with bleeding points on the surface, blunt rounded edges, and sometimes marginal infarction; congestion and hemorrhage on serosal surfaces, bleeding points on the surface of the kidneys and lungs and on the endocardium, diffuse hemorrhage of the gastric and intestinal mucosa, and hemorrhage of the gallbladder and bladder; enlargement of the lungs, with foamy fluid flowing from the cut surface, and bloody foamy mucus in the trachea; enlargement of submandibular lymph nodes and abdominal lymph nodes, with severe hemorrhage. Individuals with the peracute type may not show obvious pathological changes.
4. Laboratory diagnosis
The clinical symptoms of African swine fever are similar to diseases such as classical swine fever, highly pathogenic porcine reproductive and respiratory syndrome, and swine erysipelas, and diagnosis must be carried out through laboratory testing. Serum samples and etiological samples can be collected from diseased pigs or pigs in the same group.
For clinically suspected cases, if retesting by the laboratory of a provincial animal disease prevention and control institution or the laboratory of a prefecture-level animal disease prevention and control institution authorized by the animal husbandry and veterinary competent department of the provincial people's government detects positive African swine fever virus nucleic acid, it is judged as a confirmed case.
5. Outbreak handling and prevention and control measures
At present, there is no approved vaccine for African swine fever prevention and control. It mainly relies on biosafety measures such as pig farm environmental control, pig herd health management, feed nutrition, feeding management, hygiene and epidemic prevention, disinfection, and harmless treatment to eliminate pathogens and reduce the chance of infection. For relevant sites where suspected and probable outbreaks occur, the county-level government animal husbandry and veterinary competent department and township government in the locality shall immediately organize measures such as isolation and observation, sampling and testing, epidemiological investigation, restriction of entry and exit of susceptible animals and related items, and environmental disinfection. When necessary, measures such as blockade and culling may be taken. After the outbreak is confirmed, the animal husbandry and veterinary competent department of the people's government at or above the county level shall immediately delineate the epidemic point, epidemic area, and threatened area.
The delineation of epidemic points, epidemic areas, and threatened areas and outbreak handling shall be implemented in accordance with the provisions of the Emergency Implementation Plan for African Swine Fever Outbreaks (Second Edition 2020).
Disinfection of pig farms in disaster areas: Select effective disinfectants and disinfection methods to carry out disinfection and source elimination work. For drinking water disinfection of pig herds, 2%-3% sodium hypochlorite can be used; for empty pens and vehicle disinfection, 1:200-300 glutaraldehyde or 1:100-300 compound phenol can be used; for the pig farm environment, 0.5% peracetic acid solution can be used for spray disinfection of the pig house environment; for disinfection with pigs present, 2%-5% iodine preparations and 1:100-300 compound phenol spray can be used; the disinfection pool at the gate can be configured with 1%-5% sodium hydroxide solution for disinfection; for the disinfection channel for entering and exiting workers, an ultrasonic atomization disinfection machine can be used to atomize 1:300 Baidusha for disinfection, or ultraviolet irradiation disinfection can be used; pollutants such as manure can be treated by pile fermentation or incineration.
For African swine fever prevention and control on pig farms, the “five do's and four don'ts” must be achieved. “Five do's”: First, reduce the entry of personnel and vehicles from outside the pig farm; second, thoroughly disinfect before personnel and vehicles enter the farm; third, implement “all-in, all-out” feeding management for the pig farm; fourth, isolate newly introduced live pigs; fifth, declare quarantine according to regulations. “Four don'ts”: First, do not use swill to feed pigs; second, do not free-range live pigs; third, do not buy live pigs from epidemic areas; fourth, do not conceal or delay reporting suspected outbreaks.
In areas where African swine fever has occurred, attention should be paid to disinfection of burial sites to prevent secondary contamination caused by floods.