What are the prevention and control methods for swine dysentery fever?
Swine dysentery fever, also known as swine cholera, is scientifically called "swine fever." It is a serious acute, febrile, contact infectious disease caused by the swine fever virus. It is characterized by elevated body temperature, continued fever. Eating little or no food, liking to drink water, liking to eat young tender feed; mental depression, arched back, shivering, lying down unwilling to move, crowding together or burrowing into bedding straw; feces in ball shape or diarrhea, as well as alternating constipation and diarrhea; purple spots appearing on the ears, neck, abdomen, limbs and other parts. Swine dysentery fever can occur in all four seasons, and pigs of different breeds, sexes, and ages are all susceptible to infection.
1 Infection characteristics
Infection of swine dysentery fever is generally due to gaps in epidemic prevention, drastic climate changes, environmental changes, long-distance transport, and piglets introduced to a different location for rearing being affected by harsh environments; stress dysregulation is most likely to cause disease onset. Once infected, the affected pigs are also the main source of infection for the spread, diffusion, and propagation of the disease. The specific modes of transmission are: (1) direct contact between healthy pigs and sick pigs; (2) drinking water, premises, feed, utensils, etc. contaminated by the saliva and other secretions of sick pigs; (3) contamination by the feces and urine of sick pigs; (4) infection from accidental consumption of pork carrying the swine fever virus; (5) feeding pigs with leftover meat and vegetable soup that has not been boiled and disinfected; (6) buying, selling, and transporting pigs without disinfection treatment; (7) reuse of medical instruments that have been used to inject swine fever vaccine without disinfection; (8) insects flying or crawling over contaminated materials and excreta of affected pigs, then flying or crawling onto healthy pigs and their food items; (9) people and other animals bringing the virus from places where swine fever has occurred, etc., causing the occurrence and transmission of swine dysentery fever.
2 Clinical symptoms
The incubation period of swine dysentery fever is generally 2-8 d, but some affected pigs have a longer incubation period. The symptoms are divided into 3 types: peracute, acute, and chronic.
2.1 Peracute type: sick pigs die suddenly without obvious clinical symptoms.
2.2 Acute type: the body temperature of sick pigs rises to 40.5-42°C, with continued fever. Sick pigs are listless and often lie down. In pens without bedding straw, affected pigs crowd together and huddle; in pens with bedding straw, affected pigs like to burrow into the straw, or stand dully in corners. Conjunctival congestion, and some have purulent secretions on the eyelids. In the early stage of disease, they pass dry hard fecal balls, then diarrhea, or alternating diarrhea and constipation. The feces contain mucus or mucosa, and some contain blood. Affected pigs gradually develop purplish-red spots on the ears, under the neck, abdomen, and limbs, but some only develop purplish-red spots on the ears and the lower parts of both hind legs. This is the hemorrhagic purple spot unique to overt swine dysentery fever.
2.3 Chronic type: generally only after an incubation period of 10-20 d do vague clinical symptoms appear. Some cases transform from acute to chronic. Chronic swine dysentery fever has a long course; sick pigs gradually become emaciated, appetite is abnormal, body temperature fluctuates high and low, sometimes normal. Ear tips are cool or slightly warm, breathing is shallow, conjunctiva is flushed or pale, slight shivering and trembling, arched back and tucked waist or not obvious, movements dull and unsteady, piling on each other or burrowing into bedding straw. First constipation then diarrhea, or first diarrhea then constipation, or alternating diarrhea and constipation; feces contain intestinal mucosa or this is not obvious. Sick pigs have the characteristic of rooting and eating filth, but some do not have this characteristic. In latent swine dysentery fever, there are generally no obvious changes on the body surface skin.
3 Pathological changes
The cut surface of systemic lymph nodes shows a red-and-white marbled appearance, with hemorrhagic edges and raised cut surface, and in severe cases becoming dark red; tonsils are swollen, with severe congestion and blood stasis; laryngeal hemorrhage, with necrotic foci on the oral commissure mucosa; different degrees of hemorrhagic spots on the pericardium and heart surface, with endocardial congestion; splenic marginal infarction, with pinhead-sized hemorrhagic spots on the surface; kidneys are pale, with small hemorrhagic spots on the surface, and hemorrhagic spots in the renal cortex and medulla; cecum and colon have button-like ulcers of varying sizes, and necrotic foci on the intestinal serosa; the gastric fundus has congestive spots of varying degrees; the skin has congestive spots, subcutaneous fat has hemorrhagic spots, and some form red or purplish-red hemorrhagic spots on the ears, neck, abdomen, limbs, etc., but some only show cyanotic spots on the ears and the lower parts of both hind legs.
4 Prevention and control measures
(1) Because there is currently no effective drug treatment for this disease, only by conscientiously carrying out immunization and quarantine for swine dysentery fever, enhancing the immunity of pigs to swine fever, and promptly handling detected pigs with swine fever, can there be powerful measures to prevent and control the occurrence of swine dysentery fever.
(2) A vaccination plan must be formulated, and regular immunization in spring and autumn as well as immunization of newly added pigs at ordinary times must be conscientiously carried out, eliminating delayed and missed vaccinations. Immunity is produced 4 d after vaccination with swine fever vaccine, and the immune period is 1 year. Piglets are best vaccinated after weaning; vaccination during the suckling period is unreliable because suckling piglets have maternal antibody interference.
(3) Strengthen feeding management, do a good job in pen cleanliness and sanitation, and at the same time do a good job in the sanitation of utensils and the environment, which is conducive to the healthy growth of live pigs, thereby enhancing the disease resistance of pigs.
(4) At all times, carry out regular disinfection and sterilization of pens, premises, utensils, etc., as well as rodent control and mosquito and fly pest control.
(5) At ordinary times, always do a good job in observation and quarantine of pig houses, and handle problems promptly when found, that is, isolated rearing, observation, prevention and treatment, or destruction by (incineration and deep burial).
(6) It is strictly forbidden for sick pigs to contact healthy pigs or stray into healthy pig houses, and for other animals to roam about randomly.
(7) All pens, bedding platforms, bedding straw, feed troughs, feed, drinking water, premises, utensils, etc. contaminated by affected pigs should be strictly disinfected.
(8) The feces and urine excreted by sick pigs should be collected for disinfection and fermentation treatment.
(9) Vehicles and personnel buying, selling, and transporting pigs must all undergo strict disinfection.
(10) Outside personnel and animals are not allowed to enter pig farms and pens at will, in order to prevent the transmission of epidemic diseases.