Possible over-wintering of bluetongue virus in Culicoides populations in the Onderstepoort area, Gauteng, South Africa

Steyn, Jumari, Venter, Gert J., Labuschagne, Karien, Majatladi, Daphney, Boikanyo, Solomon N.B., Lourens, Carina, Ebersohn, Karen, and Venter, Estelle (2016) Possible over-wintering of bluetongue virus in Culicoides populations in the Onderstepoort area, Gauteng, South Africa. Journal of the South African Veterinary Association, 87 (1). pp. 1-5.

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Several studies have demonstrated the ability of certain viruses to overwinter in arthropod vectors. The over-wintering mechanism of bluetongue virus (BTV) is unknown. One hypothesis is over-wintering within adult Culicoides midges (Diptera; Ceratopogonidae) that survive mild winters where temperatures seldom drop below 10 °C. The reduced activity of midges and the absence of outbreaks during winter may create the impression that the virus has disappeared from an area. Light traps were used in close association with horses to collect Culicoides midges from July 2010 to September 2011 in the Onderstepoort area, in Gauteng Province, South Africa. More than 500 000 Culicoides midges were collected from 88 collections and sorted to species level, revealing 26 different Culicoides species. Culicoides midges were present throughout the 15 month study. Nine Culicoides species potentially capable of transmitting BTV were present during the winter months. Midges were screened for the presence of BTV ribonucleic acid (RNA) with the aid of a real-time quantitative reverse transcription polymerase chain reaction (RT-qPCR) assay. In total 91.2% of midge pools tested positive for BTV RNA. PCR results were compared with previous virus isolation results (VI) that demonstrated the presence of viruses in summer and autumn months. The results indicate that BTV-infected Culicoides vectors are present throughout the year in the study area. Viral RNA-positive midges were also found throughout the year with VI positive midge pools only in summer and early autumn. Midges that survive mild winter temperatures could therefore harbour BTV but with a decreased vector capacity. When the population size, biting rate and viral replication decrease, it could stop BTV transmission. Over-wintering of BTV in the Onderstepoort region could therefore result in re-emergence because of increased vector activity rather than reintroduction from outside the region.

Item ID: 47456
Item Type: Article (Research - C1)
ISSN: 2224-9435
Keywords: bluetongue virus; Culicoides midges; overwintering
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All articles published in this journal are licensed under the Creative Commons Attribution 4.0 International (CC BY 4.0) license, unless otherwise stated.

Date Deposited: 27 Feb 2017 05:58
FoR Codes: 30 AGRICULTURAL, VETERINARY AND FOOD SCIENCES > 3009 Veterinary sciences > 300914 Veterinary virology @ 50%
31 BIOLOGICAL SCIENCES > 3109 Zoology > 310913 Invertebrate biology @ 50%
SEO Codes: 83 ANIMAL PRODUCTION AND ANIMAL PRIMARY PRODUCTS > 8399 Other Animal Production and Animal Primary Products > 839999 Animal Production and Animal Primary Products not elsewhere classified @ 50%
96 ENVIRONMENT > 9610 Natural Hazards > 961099 Natural Hazards not elsewhere classified @ 50%
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