An infectious hepatitis of undetermined origin in mice. I. Description of the disease.

Serial intraperitoneal passage in mice of a saline extract of the pooled livers, spleens, and kidneys of such animals has led to the demonstration after three or more passages of a transmissible agent causing hepatitis. The mice developed an illness after 3 to 4 weeks characterized by hepatosplenomegaly, and serous ascites. Spontaneous diuresis and recovery usually occurred during the subsequent 2 to 4 weeks. Histological studies of the livers showed diffuse mononuclear infiltrations, focal accumulations of mononuclear cells, perivascular mononuclear cuffing, dilated sinusoids, and occasionally focal areas of necrosis. Mice which have recovered from the disease showed no noteworthy resistance to it, and their sera failed to protect against the infectious agent. Attempts to infect rabbits, guinea pigs, monkeys, and embryonated hens' eggs yielded negative results, but young hamsters developed the disease in mild form.