Submitted to: Society for Invertebrate Pathology Meeting
Publication Type: Abstract Only
Publication Acceptance Date: August 26, 2001
Publication Date: August 26, 2001
Citation: BECNEL, J.J., WHITE, S.E. CULEX NIGRIPALPUS NUCLEOPOLYHEDROVIRUS (CUNINPV) INFECTIONS IN ADULT MOSQUITOES AND POSSIBLE ROLES IN DISPERSAL. SOCIETY FOR INVERTEBRATE PATHOLOGY MEETING. 2001. v.III. p.6. Technical Abstract: Culex nigripalpus nucleopolyhedrovirus (CuniNPV) produces small globular occlusion bodies (OBs) restricted to the nuclei of midgut epithelial cells. Similar to other baculoviruses, it has two virion phenotypes, an occluded form (ODV) that initiates infection in midgut epithelium and a budded form (BV) that spreads the infection within the midgut. In the presence of magnesium, CuniNPV is readily transmitted via ODV to all 4 instars of mosquito larvae and normally results in death 72-96 hours post-exposure. While horizontal (larva to larva) transmission of CuniNPV provides the mechanism for spread and persistence within an aquatic habitat, the mechanism by which the virus reaches new habitats is unknown. Therefore, we have conducted field and laboratory studies to determine the role adults might play in the spread of CuniNPV to new aquatic habitats. Some larvae exposed to CuniNPV as late fourth instars survived to become infected adults as determined by laboratory bioassay. Histological examinations of infected adults determined that infectious OBs were found in 1) the meconium (from the infected larval midgut) and 2) replicating in male and female adult midgut epithelial cells. Infection of the adult midgut epithelium was probably initiated by BV that entered larval midgut regenerative cells that form the adult midgut. Field collected egg rafts of Cx. nigripalpus were examined for evidence of vertical transmission. Rafts were cut in half with one half hatched and reared in the presence of magnesium and the other half was ground and fed to 2rd instar larvae in the presence of magnesium. Two of 39 eggs rafts resulted in CuniNPV infected individuals but it was not determined if vertical transmission was transovarial (within eggs) or transovum (contamination of the egg surface). Based on these results, adults could play a role in the spread of CuniNPV to new aquatic habitats by voiding a meconium containing infectious OBs, by death of adults with infected midguts or vertical transmission.