Prevention and Treatment Methods for a Sudden Canine Distemper Outbreak in a Fox Population and Related Experience

1. Outbreak situation

On August 5, 2004, a farmer in this livestock community purchased a batch of Arctic foxes from elsewhere and placed them into cages in the community without isolation or observation. On August 10, the original young foxes became ill, and the disease rapidly spread to the whole group. In about 10 days, all of the more than 100 foxes in stock died. Because the owner did not report the epidemic in time, the outbreak further expanded. By August 20, of the more than 10,000 foxes in stock in the entire community, 980 were affected, an incidence rate of 9.8%. Through collective consultation, the strategy of emergency vaccination and symptomatic treatment was determined. As of September 20, the outbreak was basically brought under control, with no new cases for 10 consecutive days in the healthy fox group. Of the 980 sick foxes, 590 were cured and 390 died.

2. Symptoms

2.1 In the early stage, sick animals showed elevated body temperature (40-41C), listlessness, reduced food intake, sometimes vomiting, and a dry nose. Two to three days after onset, typical clinical symptoms of canine distemper appeared. The conjunctiva began to become red and swollen, progressing to purulent conjunctivitis, with hair loss around the eyes; in severe cases, the upper and lower eyelids stuck together from purulent discharge. The skin of the nose became cracked, the nasal mucosa became inflamed and swollen, and purulent discharge flowed out, blocking the nostrils and causing difficulty breathing. When the lungs were affected, coughing occurred, initially dry and later wet. At the same time, catarrhal inflammation occurred in the digestive organs, with diarrhea, sometimes mixed with blood.

2.2 Neurological symptoms appeared during the recovery period or at the very beginning of fever. These included spasms, epileptic seizures, increased reactivity to stimuli, and sometimes madness. Sick animals that showed neurological symptoms from the outset mostly had an acute course, with a short disease duration, dying within 1-2 days.

3. Necropsy changes

Catarrhal inflammatory lesions in the small intestine, numerous band-like and diffuse hemorrhages in the rectum, pinpoint hemorrhages in the bladder, hemorrhagic spots under the epicardium, congestion and edema of the meninges, the liver dark red or cherry-colored and filled with blood, and pinpoint or streak-like hemorrhages under the renal capsule.

4. Laboratory examination

Nasal fluid and saliva were collected aseptically from sick animals that died acutely, and 2 puppies under one year of age were artificially infected. After becoming ill, the puppies showed typical canine distemper symptoms.

5. Diagnosis

Based on the epidemiological situation, symptoms, and necropsy changes, the diagnosis was confirmed as canine distemper.

6. Control measures and results

6.1 Healthy foxes were given emergency vaccination with a combined canine distemper and viral enteritis vaccine.

6.2 Healthy foxes and sick foxes were separated, and a spray disinfectant containing iodine and chlorine was used around the foxes, twice daily. Feces were cleaned daily, the ground was sprayed with 3-5% caustic soda water, and the carcasses of dead foxes were burned and buried deeply.

6.3 After immunization of the healthy group, drug prophylaxis was carried out, with the daily dose divided into two administrations given in drinking water for 4 consecutive days. Administration method: based on each fox consuming 1 kg of drinking water per day, 100 kg of drinking water was mixed with 10 g of ribavirin, 50 g of Astragalus polysaccharide, 15 g of gentamicin, 200 g of Weitijian, and 2.5 kg of glucose.

6.4 Treatment of sick foxes: antiviral serum once daily, one vial per fox, for 2-3 days; analgin twice daily, 5 mL per fox each time; cefazolin sodium twice daily, 0.5 g per fox each time; Kaiwei Xiaoshi Ling twice daily, 1.5 mL per fox each time; for those with vomiting, Aimor was injected, 1 vial per fox each time, for 3-5 days.

7. Discussion

7.1 After the outbreak occurred, emergency vaccination of healthy foxes was an important means of controlling the epidemic. On the basis of intensive immunization, adding appropriate drugs to fox food for drug prophylaxis could effectively reduce the number of cases. Newly affected animals should be isolated promptly, given symptomatic treatment, and disinfection work should be done well.

7.2 A strict veterinary hygiene system should be established and improved. Other animals should be prohibited from entering the fox farm, and vaccination should be carried out on schedule. Breeding foxes can be vaccinated in November-December, and young animals about 2 weeks after weaning. The vaccination method is subcutaneous injection on the inner side of the hind leg. Unified management should be implemented for various production and business activities such as disease prevention, introduction of breeding stock, purchase of raw materials, and hides @#@136@#@, so that no hidden dangers remain in safe production within the community and the overall interests of farmers in the community are protected.

7.3 Sick foxes should be actively treated with symptomatic therapy and given careful nursing.

7.4 This outbreak was related to the failure of farmers in the community to carry out routine disease prevention. Fox groups in adjacent communities were effectively protected because they had received routine immunization, and after drug prophylaxis, not a single case occurred.