title: Virus recovery rates for wild-type and live-attenuated vaccine strains of African horse sickness virus serotype 7 in orally infected South African Culicoides species.
abstract: Previously reported virus recovery rates from Culicoides (Avaritia) imicola Kieffer and Culicoides (Avaritia) bolitinos Meiswinkel (Diptera, Ceratopogonidae) orally infected with vaccine strain of African horse sickness virus serotype 7 (AHSV-7) were compared with results obtained from concurrently conducted oral infections with five recent AHSV-7 isolates from naturally infected horses from various localities in South Africa. Culicoides were fed sheep bloods spiked with 10(7.6) TCID(50)/mL of a live-attenuated vaccine strain AHSV-7, and with five field isolates in which virus titre in the bloodmeals ranged from 10(7.1) to 10(8.2) TCID(50)/mL). After an extrinsic incubation of 10 days at 23.5 degrees C, virus recovery rates were significantly higher in C. imicola (13.3%) and C. bolitinos (4.2%) infected with the live-attenuated virus than in midges infected with any of the field isolates. The virus recovery rates for the latter groups ranged from 0% to 9.5% for C. imicola and from 0% to 1.5% for C. bolitinos. The C. imicola population at Onderstepoort was significantly more susceptible to infection with AHSV-7 isolated at Onderstepoort than to the virus strains isolated from other localities. Results of this study suggest that tissue culture attenuation of AHSV-7 does not reduce its ability to orally infect competent Culicoides species and may even lead to enhanced replication in the vector. Furthermore, oral susceptibility in a midge population appears to vary for geographically distinct isolates of AHSV-7.
authors: Department of Entomology, Agriculture Research Council-Onderstepoort Veterinary Institute, Onderstepoort, South Africa. venterg@arc.agric.za
authors: G J
authors: GJ
authors: Venter
authors: J T
authors: JT
authors: Paweska
mesh_terms: D000284:Administration, Oral; D000355:African Horse Sickness / Q000517:prevention & control / Q000635:transmission / Q000821:virology; D000356:African Horse Sickness Virus / Q000145:classification / Q000302:isolation & purification*; D000818:Animals; D002519:Ceratopogonidae / Q000821:virology*; D006736:Horses; D007303:Insect Vectors / Q000821:virology*; D012703:Serotyping; D013019:South Africa; D014613:Vaccines, Attenuated; D014765:Viral Vaccines / Q000008:administration & dosage*; D014779:Virus Replication
chemical_list: D014613:Vaccines, Attenuated; D014765:Viral Vaccines