Surveillance of Arbovirus Activity in Iowa , 1977

The State of Iowa maintains a continuing surveillance program for the detection of arbovirus activity. Results of laboratory studies of avian, human, and mosquito specimens collected during the summer of 1977 are presented. Cache Valley, Flanders, trivittatus, Turlock, and western equine encephalomyelitis arboviruses were isolated from 73 of the 613 pools of mosquitoes examined. Avian blood specimens collected from 41 species were examined for St. Louis encephalitis The State Hygienic Laboratory has monitored arbovirus activity in Iowa since the inauguration of an encephalitis surveillance program in 1965. That year, 6 cases of LaCrosse (California) encephalitis (LAC) were detected in children with central nervous system disease (Wong et al. 1970). Results of subsequent studies involving the collection of mosquitoes for virus isolation and the serologic testing of indicator animals placed in areas of known virus activity to monitor arboviruses in Iowa have been reported (Wong et al. 1971, 1973). Since 1971, the surveillance program has been a cooperative effort with the Entomology Department of Iowa State University. Field and laboratory studies have been expanded to include collection sites throughout Iowa. In 1971, Cache Valley (CV), Flanders (FL), LaCrosse (LAC), St. Louis encephalitis (SLE), and western equine encephalomyelitis (WEE) viruses were isolated from 41 of 1,542 pools total1 Journal Paper No. J-9155 of the Iowa Agriculture and Home Economics Experiment Station, Ames, Iowa, Project No. 2053. 2 State Hygienic Laboratory, University of Iowa, Iowa City, Iowa 52242. 3 Department of Entomology, Iowa State University, Ames, Iowa 50011. 4 Iowa State Health Department, Lucas Office Building, Des Moines, Iowa 50319. (SLE) and western equine encephalomyelitis (WEE) hemagglutination-inhibition (HI) antibodies. Both SLE and WEE antibodies were detected among the 1,037 avian sera tested. One case of WEE and three cases of California encephalitis in humans were serologically confirmed and are discussed. A survey to determine the incidence of encephalitis in equines revealed arbovirus activity throughout the