Prevalence of Equine Herpesvirus 1(EHV-1) and Equine Herpesvirus 4 (EHV-4), Molecular Epidemiology of EHV-1 in Kelantan, Malaysia

the past few years, equine herpesvirus-1 (EHV-1) has been considered as a potentially emerging disease by the United States Department of Agriculture (USDA) due to the sudden increase of outbreak and mortality. The infection of EHV-1 can cause abortion, respiratory, and neurological diseases in equids which could affect the economy of the equine industry. Current diagnostic tests for EHV-1 usually involve expensive instruments, laborious procedures, or are time-consuming. Rapid, highly-sensitive, and specific technique for identification of EHV-1 is important, especially during outbreak so that the spread of disease is minimised. Information regarding the prevalence of EHV-1 infection in Kelantan has yet to be collected. Therefore, this study aims to provide baseline data on the seroprevalence of EHV-1 and EHV-4 in Kelantan. Novel molecular assay of LAMP was assessed and compared to PCR in terms of sensitivity for the detection of EHV-1. Subsequently, sequence analysis of partial glycoprotein C (gC) gene of EHV-1 isolates from Kelantan was performed and a phylogenetic tree was generated to discover their relatedness with other strains in the gene database. A total of 54 archived serum samples were tested for the EHV-1 and EHV-4 antibody using ELISA test. Thirty archived DNA samples, as well as 40 whole blood and nasal swab samples collected from several Kelantan districts, were tested for EHV-1 gC by LAMP and PCR. The seroprevalence data indicate that EHV-4 antibody was more prevalent than EHV-1 with 85% and 1.9% rate of seropositivity, respectively. The prevalence of EHV-1 by LAMP was 60% (24/40) in blood and nasal swab samples. In comparison, LAMP performance in the detection of EHV-1 was on par with PCR in nasal swabs samples but appeared to be more sensitive in detecting EHV-1 in blood samples. The sensitivity of LAMP for EHV-1 and the detection limit at DNA level were 100 times and 10 times more sensitive than PCR, respectively. The nucleotide sequencing of the partial gC gene shows that Kelantan EHV-1 isolates are 100% homogenous and clustered with EHV-1 strains from the United Kingdom and the United States. The performance of LAMP in detecting EHV-1 in field samples is comparable to PCR. LAMP assay is indeed sensitive, rapid, and simple to use. However, LAMP still needs modifications in order to contain the high risk of carrying over contamination, which is the major drawback that limits its usage in the diagnostic laboratory or for the use in epidemiological study. Until further modifications are made to improve the concerns, evidence from this study is insufficient to be recommended either in favour or against the use of LAMP as a replacement test for PCR of EHV-1 detection in the diagnostic setting. Overall, this is the first study that provides information on the molecular identification of EHV-1 which indicates that this virus is circulating in Kelantan horse population.