Practical aspects of EHV-1 and EHV-4 diagnostics

The authors summarise the pathogenesis, clinical findings and diagnosis of equine herpesvirus-1 and 4 infection, with special regard to new research data which can be applied for performing fast and specific diagnostic methods. The most important herpesviruses of horses are EHV-1 and EHV-4, members of Alphaherpesvirinae subfamily. EHV-4 usually causes severe respiratory signs, while EHV-1 infection can cause serious economic losses through the abortion of pregnant mares and neurological disorders. The herpes-specific latency can also occur among infected horses, these animals serve as a reservoir of the virus. The infection with EHV-1 or EHV-4 can be detected with indirect (antibodies raised against the virus) and direct (virus or DNA of the virus) diagnostic methods. When clinical signs occur, applicability of serological methods is limited; therefore the role of direct virus isolation, especially with molecular methods [polymerase chain reaction (PCR)] is increasing. A single nucleotide polymorphism (SNP) in ORF30 region of the EHV-1 genome is strongly associated with the neuropathogenic attributes of the virus strain. A new real-time PCR method is developed at the Virology Department of AO VDD which can help in distinguishing the neuropathogenic and non-neuropathogenic genotypes of EHV-1.