How to prevent and treat black disease in sheep? Detailed explanation of key technical points for prevention and treatment

Black disease in sheep, also known as infectious necrotic hepatitis, is an acute, highly fatal toxemia of sheep. Both sheep and goats can be affected.

Expert disease analysis:

(1) Pathogen: The pathogen of this disease is Clostridium novyi type B, a Gram-positive, large bacillus with bluntly rounded ends, mostly occurring singly or in pairs, with a few 3-4 organisms forming short chains. Its toxins can be classified into types A, B, and C.

(2) Epidemiological characteristics: It mainly occurs in spring and summer in low-lying, damp areas where liver flukes are prevalent. Clostridium novyi is widely present in soil. When sheep consume feed contaminated with the spores of this bacterium, the spores enter the liver from the gastrointestinal wall. In a normal liver, the high redox potential is unfavorable for the spores to transform into vegetative forms, so they remain latent in the liver in spore form. When the liver is damaged by immature migrating liver flukes, causing necrosis that lowers its redox potential, the spores present there obtain suitable conditions, rapidly grow and multiply, produce toxins, enter the bloodstream, cause toxemia, damage neurons and other cells related to vital activities, and lead to acute shock and death. Therefore, the occurrence of this disease is often closely related to infection with liver flukes. This disease mainly affects adult sheep over 2-4 years of age; goats can also be infected. The occurrence and prevalence of the disease are closely related to liver fluke infection.

(3) Symptoms: The clinical symptoms of this disease are extremely similar to those of enterotoxemia in sheep and braxy in sheep, with acute onset and often sudden death. In a few cases, the course of the disease may be prolonged to 1-2 days. Affected sheep show separation from the flock, loss of appetite, elevated body temperature, difficulty breathing, drowsiness, lying prone, and sudden death without distress.

(4) Necropsy lesions: Subcutaneous veins are markedly congested, giving the sheepskin a dark black appearance. The pylorus of the true stomach and the small intestine are congested and hemorrhagic. There are varying numbers of gray-black necrotic foci on the surface and in the deeper layers of the lungs, irregularly round, surrounded by a bright red congested band, with a crescent-shaped cut surface.

(5) Diagnosis: A preliminary diagnosis can be made based on the clinical techniques for affected sheep, pathological changes such as the dark black appearance of the sheepskin, and other findings. For laboratory examination, collect tissue from the edge of the liver necrotic foci, make smears, stain and examine under a microscope; large Clostridium novyi with bluntly rounded ends can be seen, occurring singly or in pairs, with a few 3-4 organisms forming short chains.

Expert treatment.

(1) Prevention: Control liver fluke infection, and regularly inject sheep anaerobic disease pentavalent vaccine, 5 mL subcutaneously or intramuscularly. When the disease occurs, move the flock to a high, dry place. Anti-Clostridium novyi serum can also be used for early prevention, 10-15 mL subcutaneously or intramuscularly, repeated once if necessary.

(2) Treatment: a. For sheep with a slow course of disease, penicillin can be used, intramuscularly, 800,000-1,600,000 units, twice daily. b. Anti-Clostridium novyi serum, intramuscularly, subcutaneously, or intravenously, 50-80 mL, used 1-2 times consecutively.