The Journal of Young Investigators: An Undergraduate, Peer-Reviewed Science Journal

19 November 2004 - Evidence of exposure to a monkey virus possibly related to cancer has been found in the blood of North American zoo workers. According to a study in The Journal of Infectious Diseases, antibodies to Simian vacuolating virus 40, or SV40, have been found more often among zoo workers handling primates than those who did not handle them at all.

Ever since it was shown to cause cancer in laboratory animals, SV40 has been a subject of public health concern. The virus is part of the polyomavirus class, named because the viruses in this class can produce multiple (poly-) tumors (-oma) in their hosts. Researchers are even more concerned about SV40 amidst reports that the viral DNA has been found in human tumors, including lung, brain and bone tumors. More recently, SV40 has also been associated with some types of non-Hodgkin’s lymphoma-- cancers that can spread to many parts of the body.

Eric A. Engels and his colleagues at the National Cancer Institute, National Institutes of Health, Centers for Disease Control and Prevention, and the Johns Hopkins School of Medicine studied 254 zoo workers, 109 of whom handled primate extensively. The remaining 145 workers did not handle primates at all. The zoo workers were tested for SV40 antibodies, which would only be present among those workers who were infected with the virus. The results showed that while SV40 antibodies were more common among zoo workers who handled primates than those who did not, the antibody rates themselves were low. At 23 percent for primate workers and 10 percent for other workers, the low rates imply that SV40 is not replicating, or multiplying, in the workers. Without continued replication, lifelong infection with SV40 is unlikely.

While the study did not find evidence for long-term SV40 infections in humans, it did demonstrate that “individuals who work closely with nonhuman primates are occupationally exposed to SV40.”

In an accompanying editorial, Keerti Shah of the Johns Hopkins University Bloomberg School of Public Health wrote, “…although humans in contact with primates may become infected with SV40, currently available evidence does not suggest that SV40 circulates independently in the community or that it contributes to the development of any human cancer.”

Because the relationship between SV40 exposure and human cancer is still vague, Shah recommends further study of individuals exposed to primates.

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