The increased difficulty and expense of using live animals for delivering infectious blood meals in arthropod-borne virus vector competence experiments has resulted in an increase in the use of artificial feeding systems. Compared to live hosts, artificial systems require higher viral titers to attain mosquito infection, thereby limiting the utility of such systems with low or moderate titer virus stocks. Based on the report that freshly propagated virus is more infectious than previously frozen virus, we determined whether such a preparation would enhance the ability to use artificial feeding systems. Culex quinquefasciatus and Aedes aegypti mosquitoes were offered blood in artificial membrane feeders containing freshly collected or previously frozen St. Louis encephalitis and dengue serotype-2 viruses (family Flaviviridae), respectively. Infection rates and estimates of vector competence were significantly lower (P < 0.05) for mosquitoes feeding on blood meals containing frozen-thawed compared to freshly collected virus. We indicate that the use of freshly propagated virus in artificial feeding systems can be an effective blood delivery method for low-titer viruses and viruses that are otherwise inefficient at infecting vectors in such systems. Fresh viruses used in artificial feeding systems may be a viable alternative to the heavily regulated and expensive use of live animals.
KeywordsFlavivirus; Artificial feeding; Mosquito; Arthropod-borne virusIn recent years, the use of live animals has become more difficult and expensive, resulting in an increase in utility of artificial feeding systems for vector competence experiments. Artificial membrane feeding systems are an alternative to live animals for delivering viremic blood meals in vector competence experiments. Infection rates tend to be reduced in mosquitoes exposed to artificial feeding systems, compared to live hosts, as was reported for Culex quinquefasciatus exposed to St. Louis encephalitis virus (SLEV) (family Flaviviridae) via pledget versus viremic chick (Meyer et al., 1983). Compared to live hosts, artificial systems require higher viral titers to attain mosquito infection, thereby limiting the use of virus stocks with low titers (Jupp, 1976;Meyer et al., 1983). In a study of Culex pipiens and Aedes taeniorhynchus exposed to Rift Valley fever virus (RVFV) (family Bunyaviridae) via bloodsoaked pledgets as compared to viremic hamsters, infection rates were lower in the artificial system when viral titer ingested by mosquitoes was <4.7 logs plaque-forming units (pfu) RVFV/mosquito, but were equivalent in both systems when mosquitoes ingested >4.7 logs pfu RVFV/mosquito (Turell, 1988 Previous studies have attributed diminished rates of mosquito infection using artificial versus live feeding systems to the use of frozen-thawed virus stocks mixed with blood prior to mosquito feeding. Investigations comparing vector competence of mosquitoes exposed to artificial systems with fresh (i.e. virus-infected tissue culture supernatant collected immedia...