Common Types of Porcine Pathogenic Diarrhea and Prevention and Control Measures

In @#@227@#@ production, there are many causes of pig diarrhea, such as malnutrition, improper feeding management, infectious diseases, internal diseases, parasitic diseases, etc., all of which can cause diarrhea. This article analyzes the mechanisms causing porcine pathogenic diarrhea and proposes prevention and control measures for readers' reference.

1 Classification of Common Pathogenic Diarrhea in Pigs

1.1 Viral Diarrhea

1.1.1 Transmissible Gastroenteritis This disease is an acute, contagious enteric infectious disease caused by transmissible gastroenteritis virus of the Coronaviridae family. Pigs of all ages can be infected and develop the disease; adult pigs rarely die, but the mortality rate of suckling piglets can reach 10%-100%. The disease is endemic, with obvious seasonality, occurring most frequently in winter and spring. Affected piglets suddenly vomit, followed by severe watery diarrhea, elevated body temperature, lethargy, and anorexia. The feces are initially white, then turn yellow-green, often mixed with undigested milk curds and gas bubbles, with an acidic pH and a fishy odor. Sick pigs rapidly become dehydrated, emaciated, severely thirsty, with reduced or absent appetite, and generally die after 2-7 days.

1.1.2 Porcine Epidemic Diarrhea This disease is a highly contagious infectious disease caused by porcine epidemic diarrhea virus of the Coronaviridae family. It occurs mostly in winter, especially in December and January. Pigs of different ages can be infected; adult pigs only develop vomiting and anorexia, and the disease naturally subsides after a course of 4-5 weeks. The typical symptoms in nursery piglets are vomiting and watery diarrhea, severely reduced appetite, depression, rapid emaciation, and death from dehydration in severe cases.

1.1.3 Rotavirus This virus belongs to the genus Rotavirus, family Reoviridae, and has strong resistance to various physical and chemical factors in the external environment, remaining infectious at room temperature for 7 months. Stress factors such as cold, humidity, and poor sanitary conditions can promote the occurrence and development of the disease, so it is more common in autumn, winter, and early spring, and mostly affects piglets around 10 days of age; sometimes pigs around weaning also develop the disease. At the onset, the pigs are lethargic, have poor appetite, are unwilling to move, and often vomit. Then diarrhea rapidly occurs, with feces being watery or pasty, yellow-white or dark black, and dehydration occurs after 3-7 days. Lesions are mainly confined to the digestive tract; the stomach of piglets is filled with milk curds or milk, the small intestinal wall is thin and translucent, and the contents are liquid, gray-yellow or gray-black. Sometimes there is extensive hemorrhage in the small intestine and enlargement of the mesenteric lymph nodes.

1.2 Bacterial Diarrhea

1.2.1 Colibacillosis Diarrhea caused by porcine Escherichia coli can be divided by pig age into piglet yellow scour and piglet white scour.

1.2.1.1 Piglet Yellow Scour Also known as early-onset colibacillosis, it is an acute, highly lethal disease of newborn piglets, characterized by severe watery diarrhea and rapid death. It generally occurs at 1-7 days after birth, with sudden diarrhea, discharge of watery feces that are yellow or gray-yellow, mixed with small gas bubbles and fishy-smelling, after which the diarrhea becomes increasingly severe. Sick pigs are thirsty and dehydrated, but there is no vomiting, and they finally die in a coma. The lesions are acute catarrhal inflammation of the intestinal tract, with the duodenum being the most severely affected.

1.2.1.2 Piglet White Scour Also known as late-onset colibacillosis, it is a common disease of piglets at 10-30 days of age. The pathogen often exists in the pig's intestinal tract and normally does not cause disease. When adverse stress such as sudden temperature changes or sow milk that is too thin or too thick occurs, the piglets' resistance declines and the disease develops. The disease is highly contagious; if 1 piglet in a litter has diarrhea, the whole group will soon be infected if measures are not taken promptly. Its typical symptoms are: discharge of white, pasty, fishy-smelling loose feces, contamination of the area around the anus with feces, a tendency to burrow into straw piles, no vomiting, generally no elevated body temperature, and slow emaciation leading to death. The mortality rate is directly related to feeding management and treatment.

1.2.2 Clostridial Enteritis Also known as infectious necrotic enteritis of piglets, commonly called piglet red scour. The pathogen is Clostridium welchii type C or Clostridium perfringens type C. The disease occurs mostly in newborn piglets at 1-3 days of age, with a short course and high mortality; even if piglets at 4-7 days of age develop the disease, the symptoms are relatively mild. Sick pigs discharge red mucous feces and occasionally vomit.

1.2.3 Swine Dysentery This disease is an intestinal infectious disease caused by the Gram-negative bacterium Brachyspira hyodysenteriae. Pigs of all sizes can be infected, but it occurs mostly in piglets at 2-4 days of age. Seasonality is not obvious; it spreads slowly, has a long epidemic period, is prone to relapse, has a high incidence rate and low mortality rate, and body temperature is normal but slightly elevated at the onset. The discharged feces contain large amounts of mucus and blood and are often jelly-like. Necropsy lesions are mainly in the large intestine.

1.2.4 Porcine Salmonellosis Also known as piglet paratyphoid, it is an intestinal infectious disease of weaned piglets caused by pathogenic Salmonella. It mainly affects pigs at 2-4 months of age, with no obvious seasonality, and occurs sporadically in endemic areas. Salmonella is a Gram-negative bacterium, and commonly used disinfectants can kill it within a short time. Sick pigs have slightly elevated body temperature and show acute septicemia and severe diarrhea; the feces are foul-smelling, and the anus, tail, hind legs, and other areas are contaminated with blood-containing viscous feces. In chronic cases, there is repeated diarrhea; the feces are pale yellow, pale green, etc., foul-smelling, and red patches may appear on the skin. Necropsy may reveal diffuse, irregular depressed ulcers and pseudomembranes in the cecum and colon.

1.3 Proliferative Enteritis

Also known as ileitis or intestinal adenomatosis complex. The pathogen is undetermined. The disease occurs mostly in breeding pigs or large pigs weighing about 100 kg. The clinical features are a long course and black, tar-like feces. Necropsy shows proliferative hemorrhagic enteritis in the large intestine, adenoma-like proliferative protrusions of the mucosa from the ileum to the cecum, and purulent mucus can be expressed in cases with concurrent infection.

1.4 Parasitic Diarrhea

1.4.1 Coccidiosis Coccidiosis mostly causes diarrhea in piglets at 1-3 weeks of age, especially more severe in piglets at 6-10 days of age. In July-August, when the weather is rainy, humid, and the temperature varies greatly, and the pig house is damp, coccidiosis is very likely to break out. Infected pigs initially pass yellow-brown to gray pasty feces, which after 1-2 days become watery diarrhea, with progressive emaciation. If there is concurrent or secondary infection, the mortality rate will increase.

1.4.2 Ascariasis Pigs at 3-6 months of age are susceptible. In addition to Ascaris suum larvae migrating with the bloodstream to the lungs and other organs and causing ascariasis pneumonia, adult worms parasitize the small intestine and secrete toxins, causing affected pigs to have difficulty breathing and diarrhea. Affected pigs progressively emaciate, and development and growth are retarded. Necropsy may reveal Ascaris in the small intestine and other sites, and in severe cases catarrhal enteritis, hemorrhage, or ulcers may be seen.

2 Prevention and Control Measures for Pathogenic Diarrhea

The main measure for preventing and controlling pathogenic diarrhea is to adhere to the principle of "prevention first, prevention more important than treatment," strengthen feeding management, pay attention to environmental hygiene and disinfection, ensure reasonable stocking density, and keep the pens warm in winter and cool in summer. In addition, an immunization program suitable for the farm or region should be formulated, and once the disease occurs, appropriate treatment methods should be adopted.

2.1 Prevention and Control Measures for Viral Diarrhea

At present, there is no specific method for treating viral diseases at home or abroad, so for viral diarrhea, the principle of "prevention first, prevention more important than treatment" should be adhered to even more. The main measures are as follows:

2.1.1 Introduction of Breeding Stock Do not introduce breeding stock from epidemic areas or pig farms with disease, and adhere to self-breeding and self-raising to avoid introducing pathogens. If introduction is necessary, isolate and observe for one month, and only mix into the herd after confirming health.

2.1.2 Immunization For porcine transmissible gastroenteritis and rotavirus, it is best to use a combined attenuated vaccine against transmissible gastroenteritis and rotavirus, administering one intramuscular or intranasal inoculation each at 5-6 weeks and 1 week before farrowing in sows; the passive immune protection rate for 3-day-old suckling piglets can reach more than 95%. For pig farms or areas where the disease has occurred, after autumn arrives, it is sufficient to give finishing pigs and boars one more intramuscular injection of the vaccine; for porcine epidemic diarrhea, porcine epidemic diarrhea aluminum hydroxide inactivated vaccine can be used, with pregnant sows vaccinated with 4 mL at 20-30 days before farrowing, piglets under 25 kg vaccinated with 1 mL, growing pigs at 25-50 kg vaccinated with 2 mL, and growing pigs over 50 kg vaccinated with 4 mL. The inoculation site is the Houhai acupoint, and immunity develops 15 days after inoculation.

2.1.3 Treatment Because there is no specific therapy for viral diarrhea, symptomatic treatment is mainly adopted for viruses, such as administering astringent antidiarrheal agents such as tannalbin and bismuth nitrate, and using sulfonamides and antibiotics to prevent secondary bacterial infection. Commonly used drugs such as mequindox and sulfadimidine have certain effects. At the same time, it is best to also use antiviral drugs such as amantadine.

2.2 Prevention and Control Measures for Bacterial Diarrhea

As the scale of pig farming continues to expand, pollution becomes increasingly serious. In addition, inappropriate use of antibacterial drugs and feed additives containing antibacterial drugs leads many bacteria to develop drug resistance, and resistant strains have become a major problem affecting the pig industry. For this reason, comprehensive prevention and control measures should be adopted to prevent and control porcine bacterial diarrhea. The commonly used measures are as follows:

2.2.1 Prevent Introduction of Infection Sources into Pig Farms Regularly disinfect pig farms with disinfectants, enforce strict management at ordinary times, do not allow unauthorized personnel to enter pig farms, and strictly prevent introduction of infection sources. Introduced pigs must be isolated and observed, and a good living environment should be created for weaned pigs to eliminate various stresses.

2.2.2 Add Microecological Preparations Suppress the growth and reproduction of harmful bacteria, adjust the microecological balance in the pig intestine, and reduce the occurrence of diarrhea.

2.2.3 Add Appropriate Amounts of Trace Elements Such as Copper and Zinc to Feed Practice has proved that adding 250 mg/kg feed copper and 300 mg/kg feed zinc oxide to feed can not only enhance body resistance but also have antibacterial and anti-diarrheal effects.

2.2.4 Treatment After the disease occurs, it is best to select drugs to which the pigs on that farm are sensitive through drug sensitivity testing, and the dosage should be sufficient. In addition, attention should be paid to alternating drugs to prevent the emergence of resistant strains.

2.3 Prevention and Control of Parasitic Diarrhea

Parasitic diarrhea is mainly related to feeding management and sanitary conditions, so the commonly used measures are as follows:

Strengthen feeding management, pay attention to the supply of trace elements and vitamins, and improve body resistance. Clean the pens frequently, keep them clean and dry, and pile and ferment feces to kill worm eggs, coccidian oocysts, and other pathogenic microorganisms.

Use corresponding drugs for preventive deworming, such as ivermectin or avermectin, which act on internal nematodes. Deworm once each in spring and autumn every year, and centrally collect the feces discharged within one week after medication for centralized piling and fermentation. For porcine coccidiosis, anticoccidial drugs should be added to the feed in July-August for prevention and control. Because coccidia are prone to developing drug resistance, the dosage must be sufficient and attention must be paid to rotating drugs.

Cats, dogs, chickens, etc. must be prohibited from being raised in pig farms, and strict rodent control measures must be implemented to cut off animal transmission routes.