FIELD STUDIES ON THE EPIDEMIOLOGY OF VENEZUELAN HEMORRHAGIC-FEVER - IMPLICATION OF THE COTTON RAT SIGMODON-ALSTONI AS THE PROBABLE RODENT RESERVOIR

During February 1992, field studies on the epidemiology of Venezuelan hemorrhagic fever (VHF) were carried out in a rural area of Portuguesa State in central Venezuela. The objective of this work was to determi ne the prevalence of infection with Guanarito virus, the etiologic age nt of VHF, among wild rodents and humans living within an endemic focu s of the disease. A total of 234 rodents, representing nine different species, were collected and their spleens were cultured for virus. Thi rty-one Guanarito virus isolates were made from two rodent species: 19 from 40 Sigmodon alstoni and 12 from 106 Zygodontomys brevicauda. Gua narito virus antibody rates among these two species were 5.1% and 15.0 %, respectively. Nine of the 12 Z. brevicauda that yielded virus from their spleens also had Guanarito virus antibodies in their sera. In co ntrast, none of the 19 Guanarito virus-positive S. alstoni had antibod ies to the virus. These data suggest that S. alstoni usually develops a persistent nonimmunizing infection with Guanarito virus, while Z. br evicauda develops an immunizing infection. Based on knowledge of the b ehavior of other human pathogenic arenaviruses, these results imply th at S. alstoni is the principal rodent reservoir of Guanarito virus in nature. To determine the prevalence of Guanarito virus infection among humans in the same region, 195 people living near one of the rodent c ollecting sites were bled and their sera were tested for antibodies to the virus. Five individuals (2.6%) had Guanarito virus antibodies; al l were adults, and two had been diagnosed previously as having VHF. Th e results of these preliminary serologic studies suggest that the prev alence of human infection with Guanarito virus in the VHF endemic regi on is relatively low, but that the percentage of infected people who d evelop severe disease is relatively high.