Submitted to: Encyclopedia of Entomology
Publication Type: Peer reviewed journal
Publication Acceptance Date: 5/20/2003
Publication Date: 8/25/2003
Citation: ANDREADIS, T.G., BECNEL, J.J., WHITE, S.E. INFECTIVITY AND PATHOGENICITY OF A NOVEL BACULOVIRUS, CUNINPV FROM CULEX NIGRIPALPUS (DIPTERA: CULICIDAE) FOR FOURTEEN SPECIES AND FOUR GENERA OF MOSQUITOES. ENCYCLOPEDIA OF ENTOMOLOGY. 2003.v.40(4)p.512-517. Interpretive Summary: A naturally occurring virus that kills mosquitoes has been discovered by ARS scientists at the Center for Medical, Agricultural and Veterinary Entomology, Gainesville Florida. Mosquito species susceptible to this virus are important vectors of St. Louis Encephalitis, Eastern Equine Encephalitis and West Nile Virus in the United States. This new virus kills larval mosquitoes quickly and over extended periods. We have evaluated this virus against mosquitoes from the northeastern US and found that it kills the principal vectors of West Nile virus in North America, which makes it an attractive candidate for future development as a biopesticide.
Technical Abstract: The infectivity and pathogenicity of newly discovered baculovirus, CuniNPV (family Baculoviridae, genus Nulclepolyhedrovirus) originally isolated from the mosquito Culex nigripalpus Theobald, was evaluated in laboratory bioassys against fourteen species and four genera of mosquitoes native to the northeastern US. Purified virus at a dosage rate of 1.6 x 107 occlusion bodies/ml with 10 mM Mg2+ added was used in exposures with second through fourth instar larvae at temperatures ranging from 17 0C to 27 0C. High infection rates and accompanying mortality were achieved in Culex pipiens molestus Forskal (80.4% infection), Culex pipiens pipiens L. (83.0 - 14.4%), and Culex salinarius Coquillett (48.0% - 43.1%). Culex restuans Theobald was also susceptible but infection rates were lower (21.3% - 12.5%). The gross pathology associated with infection was identical to that reported in Cx. nigripalpus. Infected larvae were lethargic and were often suspended at the water surface. Development of CuiNPV was observed in the nuclei of the midgut epitheial cells in the gastric caeca and posterior region of the stomach of host larvae. Death of infected larvae usually occurred by day 4 post inoculation and none survived to pupation or adulthood. Culex territans Walker (subgenus Neoculex Dyar) was the only Culex mosquito that was not susceptible. No infections were obtained with any species of Aedes (Aedes vexans (Meigen)), Culiseta (Culiseta morsitans (Theobald)) or Ochlerotatus (Ochlerotatus canadensis (Theobald), Ochlerotatus cantator (Coquillett), Ochlerotatus communis (De Geer), Ochlerotatus excrucians (Walker), Ochlerotatus japonicus (Theobald), Ochlerotatus stimulans (Walker), and Ochlerotatus triseriatus (Coquillett)). The host range of CuniNPV appears to be restricted to Culex mosquitoes within the subgenus Culex. An inhibitory effect on transmission of CuniNPV was observed when a liver powder/Brewer's yeast mixture was used a source of food reinforcing the critical role of Mg2+ and sensitivity of the infection process to the presence other divalent cations (Cu2+, Fe2+, and Zn2+) in the larval medium that interfered with the infection process. The high infectivity and pathogenicity of CuniNPV for the principal vectors of West Nile virus in North America make CuniNPV an attractive candidate for future development as a biopesticide.