Background. Equine herpesvirus type 1 (EHV-1) is responsible for respiratory disease in young animals, abortion in pregnant mares and neurological disease, whilst equine herpesvirus 4 (EHV-4) is mainly the causative agent of respiratory disorders and rarely causes abortion. These viruses are considered as one of the most clinically and economically important pathogens of horses and can be detected in a range of tissues. Scope and Approach. Serological methods are used to detect the presence and titre of specific antibodies to EHV-1 and EHV-4 in the sera of examined horses and are useful in epizootiological studies. Commercially available ELISA kits are able to differentiate specific EHV-1 and EHV-4 antibodies. EHV-1 and EHV-4 can both be isolated using susceptible cells such as primary horse cell cultures and other non-equine cells with visible cytopathic effect. Since standard diagnostic methods can be time consuming and arduous, the scope of many studies has been to develop and confirm the sensitivity and specificity of molecular diagnostic methods. Key Findings and Conclusions. Polymerase chain reaction (PCR) has proved to be a good screening method for the presence of latent infections of horses caused by these viruses, also making possible the rapid identification and differentiation of EHV-1 and- EHV-4 in the examined samples. Real-time PCR is a sensitive, specific and quantitative method that enables the determination of viral kinetics in infected horses. Genome sequencing can be used to discover mutations in the genomes of EHV-1 and EHV-4 as well as to track the spread of their different strains globally.
Equine herpesvirus 4 DNA in trigeminal ganglia of naturally infected horses detected by direct in situ PCR.