PLoS One. 2014 Sep 12;9(9):e106975. doi: 10.1371/journal.pone.0106975.

Seasonal and interseasonal dynamics of bluetongue virus infection of dairy cattle and Culicoides sonorensis midges in northern California–implications for virus overwintering in temperate zones.

Mayo CE1, Mullens BA2, Reisen WK3, Osborne CJ1, Gibbs EP4, Gardner IA5, MacLachlan NJ1.
  • 1Department of Pathology, Microbiology and Immunology, School of Veterinary Medicine, University of California Davis, Davis, California, United States of America.
  • 2Department of Entomology, University of California Riverside, Riverside, California, United States of America.
  • 3Center for Vectorborne Diseases, University of California Davis, Davis, California, United States of America.
  • 4College of Veterinary Medicine, University of Florida, Gainesville, Florida, United States of America.
  • 5Department of Health Management, Atlantic Veterinary College, Charlottetown, Prince Edward Island, Canada.

 

Abstract

Bluetongue virus (BTV) is the cause of an economically important arboviral disease of domestic and wild ruminants. The occurrence of BTV infection of livestock is distinctly seasonal in temperate regions of the world, thus we determined the dynamics of BTV infection (using BTV-specific real time reverse transcriptase polymerase chain reaction) among sentinel cattle and vector Culicoides sonorensis (C. sonorensis) midges on a dairy farm in northern California throughout both the seasonal and interseasonal (overwintering) periods of BTV activity from August 2012 until March 2014. The data confirmed widespread infection of both sentinel cattle and vector midges during the August-November period of seasonal BTV transmission, however BTV infection of parous female midges captured in traps set during daylight hours also was detected in February of both 2013 and 2014, during the interseasonal period. The finding of BTV-infected vector midges during mid-winter suggests that BTV may overwinter in northern California by infection of long-lived female C. sonorensis midges that were infected during the prior seasonal period of virus transmission, and reemerged sporadically during the overwintering period; however the data do not definitively preclude other potential mechanisms of BTV overwintering that are also discussed.

PMID: 25215598

 

Further explanation of novel findings:

Bluetongue virus (BTV) causes a serious disease that costs the cattle and sheep industries in the United States an estimated $125 million annually, manages to survive the winter by reproducing in the insect that transmits it. The occurrence of BTV infection of livestock is distinctly seasonal in temperate regions of the world, thus this study determined the dynamics of BTV infection (using BTV-specific real time reverse transcriptase polymerase chain reaction) among sentinel cattle and vector Culicoides sonorensis (C.sonorensis) midges on a dairy farm in northern California throughout both the seasonal and interseasonal (overwintering) periods of BTV activity from August 2012 until March 2014. The data confirmed widespread infection of both sentinel cattle and vector midges during the August – November period of seasonal BTV transmission, however BTV infection of parous female midges captured in traps set during daylight hours also was detected in February of both 2013 and 2014, during the interseasonal period. The finding of BTV-infected vector midges during mid-winter suggests that BTV may overwinter in northern California by infection of long-lived female C. sonorensis midges that were infected during the prior seasonal period of virus transmission, and reemerged sporadically during the overwintering period. This discovery has important ramifications for predicting the occurrence of bluetongue in livestock and for eventually developing control strategies.

 

 

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