Cryptic etiopathological conditions of equine nervous system with special emphasis on viral diseases

Abstract

The importance of horse (Equus caballus) to equine practitioners and researchers cannot be ignored. An unevenly distributed population of equids harbors numerous diseases, which can affect horses of any age and breed. Among these, the affections of nervous system are potent reason for death and euthanasia in equids. Many episodes associated with the emergence of equine encephalitic conditions have also pose a threat to human population as well, which signifies their pathogenic zoonotic potential. Intensification of most of the arboviruses is associated with sophisticated interaction between vectors and hosts, which supports their transmission. The alphaviruses, bunyaviruses, and flaviviruses are the major implicated groups of viruses involved with equines/humans epizootic/epidemic. In recent years, many outbreaks of deadly zoonotic diseases such as Nipah virus, Hendra virus, and Japanese encephalitis in many parts of the globe addresses their alarming significance. The equine encephalitic viruses differ in their global distribution, transmission and main vector species involved, as discussed in this article. The current review summarizes the status, pathogenesis, pathology, and impact of equine neuro-invasive conditions of viral origin. A greater understanding of these aspects might be able to provide development of advances in neuro-protective strategies in equine population.

Eastern Equine Encephalitis Virus: A Scoping Review of the Global Evidence

“…To confirm that all relevant primary research was found during the search, the reference lists of 12 literature reviews/ key articles focused on EEEV identified by the ScR team were hand searched for additional articles (Sellers 1989, Freier 1993, Calisher 1994, Deresiewicz et al 1997, Olsen et al 1997, Armstrong and Andreadis 2010, Zacks and Paessler 2010, Silverman et al 2013, Arechiga-Ceballos and Aguilar-Setien 2015, Kumar and Patil 2017, Chapman et al 2018. At the point of saturation, when no new references were identified, the ScR team stopped evaluating reference lists.…”

Equine Viruses

“…In the insect vector, where the establishment of a persistent viral infection is important, there is no observable cytopathic effect and viral release is mediated exclusively via vesicle formation at the cytoplasmic membrane [53] (Figure 3). It is interesting to note that the more variable AHSV NS3 causes a much greater cytopathic effect (CPE) earlier on in the infection cycle than BTV NS3, possibly indicating that AHSV NS3 is expressed at a higher level or is more toxic than BTV NS3 [73]. The outer capsid proteins VP5 and VP2 are acquired during this process to produce mature virions.…”

“…VEEV aerosol and IN challenge of several mouse strains (CD-1, BALB/c, outbred ICR, and C3H/HeN mice) in the literature were demonstrated to be lethal models, with death mainly due to encephalitis. Mice were challenged most commonly with wild-type VEE TrD strain or V3000 strain (VEEV derived from a cDNA clone of the VEE TrD strain with a passage history of once in guinea pig brain and 14 times in chick embryonated eggs) [48,52,61,63,[72][73][74][75][76][77]. These studies demonstrated that, regardless of the exposure route, VEEV in mice entered the CNS mainly via the olfactory system due to the increased susceptibility of olfactory neurons to VEEV infection.…”

Viral Equine Encephalitis, a Growing Threat to the Horse Population in Europe?

“…The virus replicates within the CNS during phase 2, leading to clinical signs of encephalomyelitis. Phase 2 in horses is characterized by extensive virus replication in the limbic system (including hypothalamus, hippocampus, amygdala, and other nearby areas) and the spinal cord [73]. Because phase 2 is the period with the most dramatic clinical signs, most horses will be euthanized during that phase.…”