How to prevent swine dysentery? Prevention and control methods every pig farmer must read

Swine dysentery is an acute infectious disease caused by Brachyspira hyodysenteriae, clinically characterized by mucohemorrhagic diarrhea of varying degrees (commonly known as "bloody dysentery"), weight loss, and catarrhal hemorrhagic and necrotic inflammation of the cecum.

The disease can occur in all four seasons, and pigs of all ages can be affected, with a higher incidence at 2-3 months of age; the morbidity rate of infected piglets can reach 75%, and the mortality rate is 5%-25%. Diseased pigs and carrier pigs are the main sources of infection, and fecal contamination is the main route of transmission; the carrier rate of recovered pigs is very high, and the period during which they carry high bacterial loads lasts as long as several months, often causing the disease to persist endlessly in pig herds and making disinfection and epidemic prevention work more difficult.

When the disease breaks out under natural infection, the first 1-2 weeks mostly present as peracute and acute forms, clinically dominated by hemorrhagic diarrhea, then gradually change to subacute and chronic forms, clinically dominated by mucous diarrhea.

Peracute cases often die suddenly, which is a sign that the disease has begun to break out in the herd. At the beginning of the disease, the pigs are slightly less alert and have reduced appetite, the feces become hard and are covered with milky white mucus on the surface; then acute symptoms appear, with rapid diarrhea, and the feces are yellow, soft, or watery. After 1-2 days, the feces contain relatively large amounts of blood and mucus, or blood clots, and the body temperature rises to 40°C-42.5°C, then drops to normal after a few days. The diseased pigs become depressed, with pale skin, and increased blood, mucus, and fragments of necrotic sloughed epithelial tissue in the feces. The diseased pigs gradually become emaciated, with a sunken abdomen, and may finally die from weakness.

Subacute and chronic cases are milder, with diarrhea and less blood in the feces but more mucus and necrotic epithelial tissue fragments, or no diarrhea, with more blood mixed in the feces giving it a dark red color. The course of disease is longer, with progressive emaciation, pale skin, stunted growth, and a lower mortality rate.

Necropsy lesions are limited to the large intestine and are often confined to the colon; the intestinal wall and mesentery are congested and edematous, and the mesenteric lymph nodes are enlarged and show obvious white granules. The mucosa of the large intestine is congested, hemorrhagic, and swollen, and is often covered by jelly-like mucus and fibrinous exudate containing blood clots; in severe cases, the superficial mucosa becomes necrotic and forms a pseudomembrane with a bran-like or tofu dregs-like appearance.

Clinically, based on the above symptoms and necropsy changes, a preliminary diagnosis is relatively easy to make, but confirmation requires laboratory testing.

Clinically, swine dysentery must be distinguished from other diarrheal diseases: viral diarrhea of pigs is characterized by watery diarrhea with a strong fishy odor and dehydration, salmonellosis is characterized by hemorrhage and necrosis of the small and large intestines, and intestinal colibacillosis is characterized by watery diarrhea containing no blood or mucus.

Prevention and treatment:

(1) Mequindox, by intramuscular injection or oral administration, once daily, with 3-5 consecutive days as one course of treatment. These two drugs are often used alternately to prevent the development of drug resistance. Feeding them mixed into the feed at the same dose for 3 consecutive days each month can prevent the occurrence of the disease.

(2) Acriflavine hydrochloride (yellow pigment), orally at 1.5-2.5 mg per kg body weight, once daily, for 2 consecutive days. Or by slow intravenous injection at 3-5 mg per kg body weight (maximum 0.5 g); in severe cases, inject once more after 3 days.

(3) Strengthen cleaning, hygiene, and disinfection, and properly handle feces.