Canine distemper, a highly contagious disease of dogs, is caused primarily by air- borne virus which belongs to the genus Morbillivirus in family Paramyxoviridae. Wolves and foxes are also susceptible. Among laboratory animals, ferrets are the most susceptible and hence are suitable for use in diagnostic studies.
Clinical signs: The disease has an incubation period of 3 to 7 days. The symptoms include fever generally accompanied by loss of appetite. Typically, the temperature follows a diphasic course with an initial rise lasting for 1 to 3 days followed by an apparently normal temperature for 1 or 2 day(s) and then a secondary rise lasting for a week or longer. Leucopenia accompanies fever. Later, the virus attacks in succession or simultaneously the various tissues of the body and according to its location the disease is designated as cutaneous, oculo-nasal, pulmonary, gastro-enteric and nervous. Constipation followed by diarrhoea is a constant feature. Vomiting is frequently seen in cases where the stomach is involved. Complications affecting the respiratory tract lead to coughing, laboured breathing and nasal discharge. In some cases nervous symptoms are observed. The animal develops epileptic fits followed by blindness, paralysis of hind legs, meningitis and twitching of the ears, jaws and limbs. The virus produces inclusion bodies usually found in the cytoplasm of epithelial cells of the respiratory and urinary tracts.
Diagnosis: Any dog showing generalized signs of illness with fever and congested mucous membranes usually will have one of the diseases like distemper, infectious hepatitis or leptospirosis. However, diseases such as toxoplasmosis, fungal infections and occasional bacteraemia can confuse diagnosis.In the absence of typical nervous symptoms or a serological finding based on the development of specific distemper antibodies, the positive diagnosis of distemper is difficult. Bleeding time is more prolonged in infectious hepatitis than in distemper. Similarly, a high leukocyte count is more indicative of leptospirosis than of distemper.
Treatment, prevention and control: Care and nursing are two very important measures for adoption in treating a dog affected with distemper. The animal should be kept comfortable and protected from draft and extremes of temperature. Soft foods viz. scraped raw meat, warm milk, beaten eggs and meat broth, are generally liked by the animals. The eruptions occurring on the under surface of the body should be dusted with boric acid. The drugs like sulphonamides and penicillin help in the prevention with secondary infections. Immune serum has been found to be of value when given in early stages of the disease. Recovery from an attack makes the animals resistant to further infection.
The best method of preventing the disease is by vaccination. The present-day vaccines include formalin-killed, live-ferret-adapted, egg-adapted, cell-culture attenuated viruses or combined antiserum and virulent-virus. Vaccines of egg or of cell-culture origin are inoculated in pups of 6- to 8- week-old, followed by revaccination at 12 or 16 weeks of age.