Experimental louse-borne relapsing fever in the grivet monkey, Cercopithecus aethiops. II. Pathology.

Nineteen grivet monkeys, Cercopithecus aethiops, were infected with the spirochete of louse-borne relapsing fever, Borrelia recurrentis, and killed at various intervals following inoculation: 4 during the initial spirochetemia; 4 during remission; 3 during relapse; 2 that were dying following severe relapses; and 6 during convalescence. The histologic changes of histiocytic myocarditis, multiple microabscesses replacing the nodular white pulp of the spleen, and hepatitis with foci of midzonal necrosis were similar to those seen in humans. These changes are rarely seen in other infectious diseases and suggest a specific toxic effect.