With experience, many veterinary surgeons can accurately diagnose most cases of cowpox in cats on clinical signs alone. Differential diagnoses might include cat bite abscesses, neoplasia, eosinophilic granuloma, and miliary eczema, although the discrete, widespread lesions of cowpox are quite characteristic.
Fixed biopsy material
This can be examined microscopically for the characteristic eosinophilic intracytoplasmic inclusion bodies of cowpox virus. However, these are not always found, and immunostaining may be necessary for confirmation.
Isolation can be attempted on dry unfixed scab material. This can be sent by mail without the need for special transport medium. Electron microscopy of scab materia1 enables rapid diagnosis in three out of four cases, but virus isolation is more sensitive. However, isolation may take up to 10 days.
Serum can be tested for antibody using several assays. An immunofluorescence(IF) test is now routinely used as it is both sensitive and relatively rapid. Because cowpox virus is not enzootic in cats, detection of antibody is almost diagnostic of present infection. However, using class-specific monoclonal antibodies, the IF test can be modified to detect only IgM, indicative of present infection.
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