Application of real-time PCR for evaluation of distribution of equine herpesvirus type 1 in tissues of aborted fetuses.
REASONS FOR PERFORMING STUDY EHV-1 and EHV-4 abortion diagnosis is based upon detailed examination of the aborted fetus. However, in some cases, only the placenta is available for examination. Furthermore, the contribution of lesions in the placenta to pathogenesis and diagnosis of EHV-1 and EHV-4 abortion has been neglected. OBJECTIVES To assess the utility of placental examination in equine herpesvirus-1 (EHV-1) and EHV-4 abortion diagnosis. METHODS Sections of allantochorion from 49 herpesvirus abortions were analysed by PCR, in situ hybridisation and immunostaining. RESULTS Virus-specific nested PCR confirmed the presence of viral DNA in 46 cases; 41 cases were EHV-1-positive and 5 EHV-4-positive. Microscopic changes were nonspecific. Examination of the PCR-positive sections of allantochorion revealed EHV-1 DNA by in situ hybridisation (ISH) in 21 cases and EHV-4 in 4 cases. In 2 samples, DNA of both viruses was present on PCR and ISH. Viral antigen was found by immunohistology in 15 cases. Regarding the localisation of virus in the placentae, both viral DNA and antigen of EHV-1 and EHV-4 were found in endothelial cells of chorionic villi and, occasionally, in trophoblast epithelium. In the stromal endothelium, only EHV-1 was found. CONCLUSIONS The data indicate that examination of placentae is a useful diagnostic aid in EHV-1 and EHV-4 abortion diagnosis. POTENTIAL RELEVANCE Virological examination of the placenta should become standard practice in equine abortion investigations, particularly in those cases where the fetus is not available for examination.