Risk Assessment of the Transmission of Swine Fever Virus by Blow Flies

Abstract

We focused on blow flies as a potential route for classical swine fever virus (CSFV) to enter pig farms. To assess the risk of CSFV transmission by blow flies, we investigated CSFV possession in wild flies collected near the site where wild boars infected with swine fever were found and found that the CSFV gene was detected in 29.4% (5/17) of captured blow flies. In addition, to investigate the duration of CSFV possession in blow flies, captive Aldrichina grahami were fed a GPE⁻ strain culture (10^4.7 TCID₅₀/50 μl, and the viral titer obtained from the blow flies 24 hours after feeding was 10^3.3 TCID₅₀. Furthermore, a survey of fly distribution on pig farms showed that blow flies were captured mainly in the vicinity of the dead pig storage and the piggery, confirming that blow flies were flying to the farms. This study showed that blow flies can be a potential route for classical swine fever infection and that, in addition to conventional biosecurity measures, on-farm fly control is believed to be important as a classical swine fever control measure.