What are the prevention and treatment methods for sheep Clostridium welchii disease?

Between February and March 2002, at a certain city's @#@229@#@ farm, lambs less than 2 months old suddenly fell ill one after another, and died within less than 2 h despite treatment.

1 Clinical symptoms

The affected sheep separated from the flock, lay down alone in a crouched position, and were unwilling to move; when forced to move, they showed weakness and incoordination, abdominal distension, and mild symptoms of lying down and getting up. One had difficulty defecating, and one had tenesmus, with black, softened feces mixed with mucus and sloughed mucous membrane, and occasional blood streaks. One sheep had a body temperature of 38.5°C, and the other two had 40.5°C and 41.2°C, with a pulse of 80 to 100 beats/min and respiration of 20 to 30 breaths/min. The affected sheep were extremely exhausted and died one after another within 2 h.

2 Necropsy lesions

The visible mucous membranes were cyanotic, with congestion and pinpoint hemorrhages; thick, sticky feces adhered around the anus, with blood streaks; the rectal mucosa was congested and hemorrhagic. The abomasum showed hemorrhagic inflammation; the mucosa of the gastric fundus and around the pylorus had hemorrhagic patches of varying sizes, with surface necrosis; the intestinal mucosa was congested and hemorrhagic. The contents of the duodenum were the color of thin bean porridge; the submucosal tissue was edematous, with obvious congestion and hemorrhagic lesions. The liver was enlarged, and its texture was friable, like that of cooked meat; the epicardium had pinpoint petechial hemorrhages.

3 Diagnosis

3.1 The sheep fell ill suddenly, with a short course and rapid death; based on abomasal hemorrhage and necrotic inflammation, a preliminary diagnosis of Clostridium welchii disease was made.

3.2 The samples were sent to the College of Animal Science of the Chinese People's Liberation Army Quartermaster University for testing, and the diagnosis was confirmed as sheep braxy (Clostridium welchii disease).

3.3 Differential diagnosis: Other infectious diseases similar to sheep braxy include sheep enterotoxemia, lamb dysentery, and sheep toxemia. Their pathogenic bacteria are all Clostridium species.

Sheep braxy is caused by Clostridium septicum; sheep enterotoxemia is caused by Clostridium welchii type D; the pathogen of sheep enterotoxemia is caused by Clostridium welchii type C; and the pathogen of lamb dysentery is Clostridium welchii type B. The symptoms of these diseases are similar, so epidemiology, clinical symptoms, necropsy investigation, and testing must be carried out properly for a preliminary diagnosis, and then a confirmed diagnosis of sheep braxy can be made based on bacteriological testing.

4 Treatment

Large doses of antibiotics and sulfonamides were used, along with cardiac support, fluid replacement, and intestinal disinfection, but because the onset is acute and the course is short, with some dying before symptoms were even seen, the general treatment effect was poor.

5 Experience

5.1 Prevention and control measures that breeding sheep farms should adopt

5.1.1 The adult ewes were immunized twice with a tetravalent vaccine in December of last year and June of this year, forming strong antibodies, and no outbreak occurred.

5.1.2 Lambs under half a year old and over 2 months old were also injected with 2 to 3 mL of the tetravalent vaccine.

5.1.3 Lambs under 2 months old also obtained certain transferred antibodies by suckling colostrum.

5.2 Causes of death

The dead lambs were those under 2 months old. The main causes of death were, first, that the transferred antibodies obtained from colostrum gradually declined and disappeared as the lambs grew older; second, that the lambs' own immune systems were not fully developed, and even vaccination could not produce strong antibodies, so they could not resist attack and invasion by field strains.

In summary, to ensure the healthy development of lambs, immunization of ewes with the tetravalent vaccine before lambing must be carried out properly so that lambs can obtain strong transferred antibodies. After maternal antibodies in lambs decline and before vaccination, drug prevention should be adopted. Lambs must be immunized with the tetravalent vaccine at the proper time to reduce unnecessary losses.