Reduced Recovery of Rift Valley Fever Virus Associated with Assay of Mosquito (Diptera: Culicidae) Larvae Pools

摘要

Experiments were conducted to determine if the number of uninfected mosquitoes per pool affected recovery of Rift Valley fever (RVF) virus. While the inclusion of as many as 100 uninfected adult male or female mosquitoes per pool did not affect recovery of virus by plaque assay employing Vero cells, the presence of as few as 5 uninfected larvae in a pool significantly reduced the infectivity titer of RVF virus recovered. This phenomenon was observed for larvae of both species tested (Culex pipiens and Aedes aefypti), and for pools containing either an experimentally infected (inoculated) larva or an added constant amount of RVF virsu. By inoculation of larval pools into hamsters, virus could be detected in some pools that were negative by plaque assay, but inoculation failed to detect virus from some of the pools to which less than approx. 700 plaque-forming units (PFU)/ml had been added. An enzyme-linked immunosorbent assay (ELISA) was not affected by pool size but failed to detect antigen from pools to which less than 1000 PFU/ml had been added. Inoculation of Toxorhynchites amboinesis was the most sensitive assay system for detection of virus in pools containing 10 or more larvae to which form a RVF viral suspension had been added (RVF virus was recovered from pools that were negative by plaque assay, hamster inoculation, and ELISDA).