A study of New and Old World monkeys to determine the likelihood of a simian reservoir of smallpox.

The author presents data indicating that three species of New World monkeys (Cebus apella, Ateles paniscus, Lagothrix lagothricha) are not susceptible to Brazilian variola minor. Although the number of animals tested was not large, no experimental evidence was obtained to suggest that these species could form a non-human reservoir for smallpox in the Western Hemisphere. The results also indicate that Cercopithecus aethiops are not very susceptible to infection with either variola major or minor. Haemagglutination-inhibition tests of sera from monkeys from South America, Africa and the Philippines failed to reveal significant levels of poxvirus antibody. Previous studies have shown that Macaca irus, although susceptible to experimental infection with variola major, are not able to maintain the infection for more than a few generations of disease. The author concludes that there is as yet no clear experimental, serological or epidemiological evidence to support the hypothesis that smallpox can exist in wild simian populations.