Worms and reproductive failure: First evidence of transplacental transmission leading to repeated equine abortion.

Infections with facultatively parasitic spp. nematodes are usually fatal in animals and humans. Here, transplacental transmission of a species of is described for the first time, causing reproductive failure of a mare during two consecutive gestations. In both cases, histology showed adult and larval nematodes in the placenta and various foetal organs, without signs of generalized halicephalobosis in the mare. An identical 18S rRNA-ITS1-5.8S rRNA-ITS2 sequence generated from both placentas showed considerable divergence from a previously sequenced equine isolate, suggesting cryptic diversity among isolates in vertebrates. This ubiquitous nematode may be a cause of equine abortion associated with considerable economic loss. Future research should aim at exploring effective treatment options and clarifying the true taxonomic diversity within the genus .