June 12 2008 ~ Extracts we have seen from papers presented at Brescia
on the transplacental movement of BTV include the following:
"...circumstantial evidence is presented to indicate contact spread of the bluetongue virus with oral transmission by ingestion of infected placenta being the most probable route of infection" Fraser Menzies et al
"...Transplacental and oral transmission of BTV are rare.... incidental successful transmission of BTV via these routes could lengthen the presence of viraemic animals during the winter period "Anoek Backx et al
"..During January 2008...animals were. PCR-negative for BTV at 12 and 42 days post-importation, three of their calves were shown to be infected with BTV-8 soon after they were born ... indicating vertical transmission... also passed to two previously sero-negative and PCR negative animals (one from the Netherlands and one from Scotland) that had been housed in the same building, indicating horizontal transmission, in the absence of the adult vector insects".
"The majority of calves from infected cows were negative...13 calves were seropositive, most likely by uptake of colostrum from infected cows.. the northern European variant of BTV-8 can spread vertically resulting in viraemic calves in spring. This phenomenon could lengthen the presence of viraemic animals during the winter period without vector activity, and consequently could be of major importance for the overwintering of BTV". Linda van Wuijkhuise-Sjouke et al.
June 12 ~ The 4 studies come from multiple institutes- suggesting consensus
i.e. there is compelling evidence for the vertical and horizontal transmission of BTV during winter when vector insects are absent.
One expert comments:
" what the presentations say to me is that animals should not be moved from infected areas - not even in the early winter even if the vector has become inactive. ...we are moving further and further away from using the vector-free period as a definitive risk-free measure.
It does put the EU in a bind because their main objective has been to keep trade routes open and to compel still uninfected Member States to keep their doors open to the continued movement of livestock. Is this the reason why some countries are beginning to mouth the words: "We are endemic!"?.."