Quantification of the increase in the frequency of early calving associated with late exposure to bluetongue virus serotype 8 in dairy cows: implications for syndromic surveillance

Abstract

A recent study evaluating whether reproductive data could be used for syndromic surveillance found an increased frequency of early calving (calving occurring a few days earlier than expected) in areas exposed to the Bluetongue virus serotype 8 (BTV-8) in northern Europe. A high proportion of herds infected during the 2006–2009 European outbreak were not reported through the surveillance system. The objectives of this study were (1) to quantify the increase in the frequency of early calving associated with the exposure to BTV-8 in late gestation and (2) to determine whether this association could be found in populations exposed to BTV-8 but without reported clinical signs. Increases in frequency of early calving were quantified for cows in herds located in the 2007 outbreak area in France, reported or not as cases. Increases were detected for cows in both categories of herds with a larger effect in herds reported after clinical signs. Moreover, the largest effect was found for exposures occurring during the latest stage of pregnancy, suggesting that BTV infection could trigger calving in cows in late gestation, a few days earlier than expected. This is the first study quantifying the association between a viral infection and a shortened pregnancy length (still within a normal range). The high magnitude of the increase in frequency of early calving, their occurrence in herds from infected areas but not reported, and the short time interval between exposure and the occurrence of the event confirm the interest of using early calving as an indicator for syndromic surveillance.Electronic supplementary materialThe online version of this article (doi:10.1186/s13567-015-0296-7) contains supplementary material, which is available to authorized users.

Serological evidence of bluetongue virus infection and serotype distribution in dairy cattle in South Korea

“…These findings indicate that BTV is widespread and actively circulating in dairy cattle in South Korea. The results also support the idea that serosurveillance of this species would be useful for detecting BTV circulation [34, 53–56]. Thorough research on the hosts and vectors involved in BTV circulation in natural ecosystems in the Far East is also needed, as has previously been suggested elsewhere [30].…”

Assessing the export trade risk of bluetongue virus serotypes 4 and 8 in France

“…The clinical symptoms of the disease will not appear immediately after infection, which will arouse the suspicion of the staff. Duration of viraemia (days) was 3 days ( V ) (Nusinovici et al., 2016). The probability that BTV was not detected when the bovine semen export was expressed by Poisson distribution simulation $$1 - \sum\nolimits_{{\rm{i}} = 0}^{30} {( {\frac{{\lambda {\rm{i}}*\exp ( { - \lambda } )}}{{{\rm{i}}!}}}$…”

Vaccination as a Strategy to Prevent Bluetongue Virus Vertical Transmission

“…Once pregnancy advances and the BTV-susceptible glial and neuronal precursor cells migrate to the white matter, the teratogenic effects of BTV infection in fetuses are diminished [81]. Infections in late pregnancy typically produce mild encephalitis and premature births [84,88,89]. Newborn calves/lambs exposed to BTV in utero can be born PCR positive.…”