Studies on an outbreak of Wesselsbron virus in the Free State Province, South Africa.
In early March 1996, Wesselsbron (WSL) virus caused mortality among lambs on a farm near Bultfontein in the northern Free State Province, South Africa. Mosquito collections were therefore undertaken from 27 March to 1 April to collect floodwater Aedes mosquitoes for attempts at virus isolation. In all, 4,732 floodwater Aedes were tested; 5 WSL, 1 Middelburg (MID), and 5 unidentified viruses were isolated from 3,052 Aedes (Neomelaniconion) mcintoshi/luridus (minimum infection rate [MIR] for WSL = 1.63) and 5 WSL, 1 MID, and 3 unidentified viruses from 1,478 Aedes (Ochlerotatus) juppi/caballus (MIR for WSL = 3.38). One of the authors developed WSL fever on 3 April; WSL virus was isolated from his serum, and he developed a titer of 1:640 in the hemagglutination inhibition (HI) test and became IgM positive against WSL virus. Among a sample of 44 sheep bled on 4-5 September, 59% were antibody positive by the HI test against WSL and 48% against MID viruses. Mosquito collecting was restricted to 2 discrete, shallow, grassy depressions that were the main floodwater Aedes breeding sites on the farm so they will be investigated further as possible foci of transovarial transmission of WSL and MID viruses.
Jupp
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PG
Special Pathogens Unit, National Institute for Virology, Sandringham, South Africa.
Kemp
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A
D000330:Aedes / Q000821:virology*; D000818:Animals; D000914:Antibodies, Viral / Q000097:blood; D003465:Culex / Q000821:virology; D004196:Disease Outbreaks / Q000662:veterinary*; D018178:Flaviviridae Infections / Q000097:blood / Q000453:epidemiology / Q000662:veterinary* / Q000821:virology; D006801:Humans; D007303:Insect Vectors / Q000821:virology*; D051379:Mice; D012756:Sheep; D012757:Sheep Diseases / Q000097:blood / Q000453:epidemiology* / Q000821:virology; D013019:South Africa / Q000453:epidemiology
D000914:Antibodies, Viral