Effect of normal mosquito extracts upon arbovirus recoveries from mosquito pools
Ksiazek, T.G.; Hardy, J.L.; Reeves, W.C.
American Journal of Tropical Medicine and Hygiene 34(3): 578-585
1985
ISSN/ISBN: 0002-9637 PMID: 2860815 Document Number: 257888
Titers of Turlock (TUR) and Hart Park viruses were reduced to undetectable levels when virus was mixed with a triturated suspension of uninfected (normal) 4th instar larvae of Culex tarsalis prior to plaque assay in cell culture. There was a linear relationship between the number of larvae in the pool and the titer of virus recoverable. Virus was undetectable when 1000-10,000 plaque-forming units of either agent was added to pools that contained .gtoreq. 25 larvae. Suspensions of up to 25 adult male or female C. tarsalis had little effect on detectable viral titers while pupal suspensions had an intermediate effect. The inhibitory effect of normal larval extracts on viral infectivity could be counteracted by use of polycations or a high pH buffer. A similar reduction in titer of TUR virus was observed with extracts of larvae of Aedes melanimon or Anopheles franciscanus. Larval extracts of C. tarsalis similarly reduced titers of California and St. Louis encephalitis viruses but not western equine encephalomyelitis virus. These findings may have significant bearing on the interpretation of transovarial transmission attempts in which pooled larvae are assayed for virus.