Emergence of La Crosse virus from endemic foci. Fluorescent antibody studies of overwintered Aedes triseriatus
Beaty, B.J.; Thompson, W.H.
American Journal of Tropical Medicine and Hygiene 24(4): 685-691
1975
ISSN/ISBN: 0002-9637 PMID: 1098500 Document Number: 86285
The frequency and distribution of LaCrosse virus overwintering in the diapause eggs of Aedes triseriatus (Say) were studied during 1974 in 64 tree-hole oviposition sites in four enzootic hardwood forest areas in Wisconsin. A direct fluorescent antibody technique, adapted for detection of the virus in individual mosquitos, proved to be a rapid, reliable and economical tool for ascertaining true field infection rates. Virus was found in larvae from each of the four study areas before the seasonal emergence of adults in late June and detected in 10 of 1698 individually processed adults reared from collected larvae. In one of the areas, all 12 located tree holes were enclosed with gauze before emergence of the adults, to ensure that all those collected from these sites originated from overwintered eggs. Of 1280 adults of A. triseriatus processed from this area throughout the season, 1.2% contained virus. Isolates were found in overwintered examples of A. triseriatus throughout the summer months, demonstrating the role of the tree-hole sites as foci for both overwintering and continuing summer season source of the virus in these forested areas.