Role of evolutionary epidemiology in the determination of the risk factors associated with some equine viral diseases

Abstract

The evolutionary epidemiology is crucial as it does not only help in tracking the origin, spreading, prediction, and control of viruses but also explains the failure causes of some vaccines and serological diagnostic tools. To keep animal welfare, it is essential to raise awareness of the multiple risk factors associated with the different epidemics. Arthropod-borne viruses like African horse sickness virus (AHSV) and equine infectious anaemia virus (EIAV) are related to vectors multiplication. Accordingly, their seasonal occurrence was attributed to the environmental climatic conditions. While equine influenza virus (EIV) and equine herpes virus (EHV) were found to occur in winter and spring (foaling seasons), respectively. The management risk factors resulted in the occurrence and reactivation of latently infected cases. The RNA viruses are characterized by genetic assortment which results in increasing pathogenicity, and failure of the used vaccines. The EHVs able to establish infection in different host tissues adding to their immune evasion strategies. Most of the diseases occurred at the age over 2 years although the EIAV takes long time to appear. The hard work of males and other stress factors render them more liable for infection with equine viral arteritis (EVA), EIAV, and EHV. Genetically, some breeds of horses were at risk of AHSV, EVA, and EHV infection. Most of the donkeys, mules, and zebra develop subclinical forms that magnifies their role in the epidemiological situation. Different phenomena like overwintering in AHSV, hard work in EIV, virus hidden nature and latency in EHV should be more analysed.