Effect of temperature on African horse sickness virus infection in Culicoides
This paper shows that both the infection rate and the rate of virogenesis of African horse sickness virus (AHSV) within vector Culicoides are temperature dependent. As temperature is reduced from permissive levels the lifespan of the vector itself is extended but the rate of virogenesis decreases and infection rate falls dramatically so that at 10°C virtually all midges are free from virus by 13 days post infection (dpi). When vectors that had been kept at this temperature for 35 days were moved to a permissive temperature for 3 days; however, the apparent zero infection rate increased to 15.5%. It therefore appears that at low temperature (≤ 15°C) AHSV does not replicate but virus may persist in some vectors at a level below that detectable by traditional assay systems and when the temperature later rises to permissive levels virus replication is able to commence. On the basis of this information an overwintering mechanism for AHSV is suggested. The temperature at which the immature stages of Culicoides are reared may also influence infection with AHSV. A 5-10°C rise in larval developmental temperature resulted in an increase in oral infection rate of a normally non-vector species of Culicoides, from < 1% to > 10%. A mechanism is suggested.
KeywordsInfection Rate Virus Titre Salivary Gland Cell Bluetongue Virus Culicoides Species
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- 1.Ando M, Carcavallo R, Epstein PR, Haines A, Jendritzky G, Kalkstein LS, McMichael AJ, Odongo RA, Patz I, Piver WT, Slooff R (1996) Effects on biological disease agents. In: McMichael AJ, Haines A, Slooff R, Kovats S (eds) Climate change and human health. WHO, Geneva, pp 71–105Google Scholar
- 4.Boorman J (1990) A review of Culicoides subgenus Avaritia species (Insecta, Diptera, Ceratopogonidae), vectors of viruses of sheep, cattle and horses, with particular reference to Culicoides imicola in Europe and the Mediterranean region. A report prepared for the Overseas Development Administration of the British Government, Natural History Museum, LondonGoogle Scholar
- 7.Finney DJ (1994) Statistical method in biological assay, 2nd ed. Griffin, LondonGoogle Scholar
- 8.Fu H (1996) Mechanisms controlling infection of Culicoides biting midges with blue-tongue virus. PhD thesis, University of HertfordshireGoogle Scholar
- 11.Meiswinkel R (1989) Afrotropical Culicoides: a redescription of C. (Avaritia) imicola Kieffer, 1913 (Diptera: Ceratopogonidae) with description of the closely allied C. (A) bolitinos sp.nov. reared from the dung of the African buffalo, blue wildebeest and cattle in South Africa. Onderstepoort J Vet Res 56: 23–39PubMedGoogle Scholar
- 13.Mellor PS (1990) The replication of bluetongue virus in Culicoides vectors. In: Roy P, Gorman BM (eds) Bluetongue viruses. Curr Top Microbiol Immunol 162: 143–161Google Scholar
- 17.Mellor PS, Boorman JPT, Wilkinson PJ, Martinez-Gomez F (1983) Potential vectors of bluetongue and African horse sickness viruses in Spain. Vet Rec 112: 229–230Google Scholar
- 20.Sellers RF, Mellor PS (1993) Temperature and the persistence of viruses in Culicoides during adverse conditions. Rev Sci Tech OIE 12: 733–755Google Scholar
- 22.Wellby MP, Baylis M, Rawlings P, Mellor PS (1996) Effect of temperature on survival and rate of virogenesis of African horse sickness virus in Culicoides variipennis sonoren-sis (Diptera: Ceratopogonidae) and its significance in relation to the epidemiology of the disease. Bull Entomol Res 86: 715–720CrossRefGoogle Scholar