Evidence for transplacental transmission of the current wild-type strain of bluetongue virus serotype 8 in cattle.

摘要

A total of 110 pairs of serum samples from cows and their calves were collected during caesarean sections, between November 2007 and January 2008, to examine the possibility of transplacental transmission of Bluetongue virus serotype 8 (BTV-8) in cattle. The maternal and precolostral calf serum samples were taken from clinically healthy animals on 65 randomly selected farms in southern Belgium. The sera were examined for anti-BTV antibodies using competitive ELISA. To illustrate the antibody reactivity patterns, a frequency distribution analysis, given as a profile distribution of the PN values divided into 10 classes, was made. Results showed that 93% of the maternal sera were seropositive and 35% of the calf sera were positive. This shows that 35% of the calves sampled were infected by BTV-8 in utero. To the authors' knowledge, there are no previous reports of calves born seropositive to dams infected with wild-type strains of BTV. The recent observation of a series of hydranencephalopathies in calves and lambs examined postmortem and the anti-BTV-8 antibody titres measured in paired sera from a cohort of precolostral calves and their dams in this study, strongly suggest that the BTV-8 strain that spread across Europe in 2007 differs from previous wild-type strain in that it is able to cross the ruminant placenta spontaneously and infect the fetus. This has greater impact due to more frequent abortions and the birth of non-viable offspring.