50 - How the presence of other organisms in a viremic vertebrate host may affect the ability of a mosquito feeding on that host to be able to transmit that virus.

Abstract: In order for a mosquito to be able to transmit a virus, it must feed on a viremic animal, and the virus must infect the midgut, escape into the hemocoel, enter the salivary glands, and be secreted into the saliva before that mosquito is able to transmit that virus by bite. Some mosquitoes have midguts that are not susceptible to virus infection, or even if they are, the time from virus ingestion to when they can transmit virus by bite may be over two ovarian cycles. However, in nature, vertebrates often are infected with more than one pathogen (e.g., filarial infection and an arbovirus or malaria and an arbovirus). Because both filaria and malaria infections can persist for long periods of time, animals infected with either of these pathogens, if they become infected with a virus, may allow mosquitoes to ingest both that pathogen and the virus concurrently. Because microfilariae penetrate the midgut almost immediately after a bloodmeal, they may allow a virus to bypass both midgut infection and midgut escape and infect the hemocoel within hours of ingestion. This would not only allow for a much higher dissemination rate but would also greatly shorten the extrinsic incubation period. Similarly, as malaria sporozoites penetrate a salivary gland, they may allow a virus to bypass a salivary gland barrier. However, as with viruses and mosquitoes, there appears to be a species-specific interaction between viruses and these other pathogens. This presentation will illustrate how the presence of these other pathogens can significantly affect the ability of a mosquito to transmit a pathogen and even turn an essentially incompetent mosquito into a competent vector.