FIELD EVIDENCE FOR MULTIPLE HOST CONTACTS DURING BLOOD-FEEDING BY CULEX TARSALIS, CX-RESTUANS, AND CX-NIGRIPALPUS (DIPTERA, CULICIDAE)

Field studies were conducted in Manitoba, Canada, and Florida, United States to evaluate the frequency of multiple host contacts by Culex tarsalis Coquillett, Cx. restuans Theobald, and Cx. nigripalpus Theobald, primary and secondary vectors of several encephalitis viruses in North America. Blood-fed mosquitoes were collected from box traps, each baited with a pair of quail. One quail of each pair was injected with rubidium and the other with cesium to permit the determination of the source(s) of each blood meal. Approximately 5% of all blood-fed Cx. tarsalis, Cx. restuans, and Cx. nigripalpus ingested blood from both quail during overnight exposure. The frequency of multiple feeding by these species ranged from 0 to 18.5%, 0 to 33.3%, and 0 to 17.6%, respectively. Of the 331 mosquitoes that ingested blood from 2 quail, 57 (17.2%) were not fully blood fed. Also, 1.0-3.5% of blood-fed mosquitoes had ingested blood before entering the quail-baited traps. Any increase in the number of host contacts as a result of multiple feeding, however modest, may increase disproportionately the rate at which virus transmission occurs.