Adult cebus (Cebus sp.), patas (Cercopithecus patas), rhesus (Macaca mulatta), and vervet (Cercopithecus aethiops) monkeys were found susceptible to experimental infection with Leptospira icterohaemorrhagiae (as evidenced by febrile response, weight loss, antibody production, and recovery of leptospires from hemoculture of some of the animals), although they did not show frank illness. Vervets were similarly susceptible to infection with L. canicola, L. mini georgia, and L. pomona. Leptospiruria was uncommon.
Squirrel monkeys (Saimiri sciureus) given L. icterohaemorrhagiae had in contrast clinically acute leptospiral disease, sometimes fatal, with pronounced icterus and minimal hepatic lesions accompanied by markedly increased indirect bilirubin and normal transaminase levels. The findings suggest that hemolysis may be a significant factor in the early development of jaundice in these animals.
In some of the primates tested, the tendency of leptospiral agglutinins to disappear within a few months makes retrospective serologic studies for leptospirosis of doubtful validity. In the various species studied, except squirrel monkeys, L. icterohaemorrhagiae infections elicited the “paradoxical” serologic reaction, which further emphasized the difficulty of determining the infecting leptospiral serotype by serologic means.
Primary infection with L. icterohaemorrhagiae protected animals well against attempted homologous superinfection. Little cross-protection could be demonstrated by prior L. icterohaemorrhagiae infection against subsequent challenge by L. canicola or L. pomona.
Present address: State Department of Health, Hilo, Hawaii.