Studies on canine distemper infection by means of fluorescein-labeled antibody: I. The pathogenesis, pathology, and diagnosis of the disease in experimentally infected ferrets

A study of the pathogenesis of canine distemper infection in ferrets by means of fluorescein-labeled antibody revealed that viral antigen was first detectable in the cervical lymph nodes 2 days after intranasal inoculation. Subsequently, the virus spread to the mediastinal nodes, the mesenteric nodes, the spleen, the Kupffer cells of the liver and the blood. About one week after infection, viral antigen began to appear in the epithelium of the gastrointestinal tract, the respiratory tract, the urinary tract, and the cutaneous tissues. Infected animals usually became moribund and died. The viral antigen usually appeared as fine intracytoplasmic fluorescent granules during the early stage of infection. As the infection progressed, the antigen aggregated to form large, oval objects in the cytoplasm or in the nucleus corresponding to the size and shape of eosinophilic inclusion bodies. Viremia was present before fever and other obvious signs of distemper infection appeared and persisted until the death of the animals. By the examination of peripheral blood smears for the presence of fluorescent leucocytes containing specific viral antigen, a rapid method is available for the diagnosis of distemper in ferrets.