Diagnosis and Treatment of Clostridium perfringens Infection in Raccoon Dogs

In August 2003, raccoon dogs raised by an individual farmer were infected with a disease characterized by fever, diarrhea, respiratory difficulty, and acute death. Through epidemiological investigation, clinical examination, pathological necropsy, bacteriological examination, and serotyping, the disease was confirmed as Clostridium perfringens infection in raccoon dogs.

1 Outbreak information

An individual farmer raised @#@252@#@64 raccoon dogs, 8 became ill, and 4 died, with a morbidity rate of 12.5% and a mortality rate of 50%.

2 Clinical symptoms

The onset was acute, with sudden death without any clinical symptoms, and the course of disease was generally 12-24 hours. Some diseased raccoon dogs had reduced appetite and vomiting. The feces were liquid, green, and mixed with blood.

3 Pathological changes on necropsy

Subcutaneous tissue edema, bloody exudate mixed in the thoracic cavity, and hemorrhagic spots on the diaphragm and pleura; the liver was enlarged and yellowish-brown or yellow; the mucosa of the small intestine and large intestine was hemorrhagic and resembled a blood sausage in appearance, and the intestinal contents were filled with purplish-black blood; the mesenteric lymph nodes were enlarged and hemorrhagic; the cut surface of the spleen was purplish-black; the kidney was slightly soft in texture, with hemorrhage in the cortex and medulla.

4 Microscopic examination of smears from diseased material

Smears of ileal contents and liver were examined microscopically, and Gram-positive large bacilli with flat, squared ends were observed in all cases.

5 Isolation and culture

A small piece of liver tissue was collected aseptically and inoculated into anaerobic meat-liver broth, then cultured at 37°C for 4 hours, after which a large number of gas bubbles were produced above the medium. The liquid culture was aseptically transferred to a selective solid medium and placed in an anaerobic jar, then cultured at 37°C for 48 hours, yielding a pure culture.

6 Enterotoxin examination

2 mL of ileal contents with obvious lesions was collected, an equal amount of sterile normal saline was added, and after shaking evenly, the mixture was centrifuged at 3000 rpm for 20 minutes. 0.1 mL of the supernatant was taken and injected intraperitoneally into a 20 g mouse, and the mouse died 1 hour after injection.

7 Serotyping

1 mL of the centrifugal supernatant from an 8-hour culture in anaerobic meat-liver broth was separately mixed with an equal amount of Clostridium perfringens typing serum and incubated in a water bath at 37°C for 40 minutes. 0.5 mL of each mixture of the type A, B, C, and D sera with toxin was injected intraperitoneally into mice, and the mice were observed for 48 hours after injection, with the results recorded. The serotype of the isolated Clostridium perfringens was confirmed to be type A.

8 Prevention and control measures

Clostridium perfringens infection in raccoon dogs is characterized by acute onset, rapid death, high lethality, and sporadic occurrence. The clinical treatment effect for this disease is relatively poor, so prevention is the main approach.

8.1 Drugs highly sensitive to this disease include ofloxacin, norfloxacin lactate, neomycin, and chloramphenicol, etc. Generally, neomycin is given in feed at 10 mg per kilogram of body weight, twice a day for 3-4 consecutive days, which can achieve a certain effect.

8.2 Many scholars believe that Clostridium perfringens is a common bacterial group in the digestive tract and, under specific conditions, rapidly multiplies in the gastrointestinal tract and produces large amounts of toxin; high concentrations of toxin alter intestinal permeability, enter the blood, and cause systemic toxemia, leading to disease. Probiotics are a type of live bacterial preparation that can effectively regulate the structure of the intestinal flora and inhibit the growth and reproduction of harmful bacteria, thereby preventing the occurrence of this disease.