Abstract:
Equine encephalosis virus (EEV) is a neglected virus endemic to South Africa and is
considered to generally result in mild disease in equines. Specimens were analyzed from live horses
that presented with undefined neurological, febrile, or respiratory signs, or sudden and unexpected
death. Between 2010 and 2017, 111 of 1523 (7.3%) horse samples tested positive for EEV using a
nested real-time reverse transcriptase polymerase chain reaction (rRT-PCR). Clinical signs were
reported in 106 (7.2%) EEV positive and 1360 negative horses and included pyrexia (77/106, 72.6%),
icterus (20/106, 18.9%) and dyspnea (12/106, 11.3%). Neurological signs were inversely associated
with EEV infection (OR < 1, p < 0.05) relative to EEV negative cases despite a high percentage of
animals presenting with neurological abnormalities (51/106, 48.1%). Seventeen of the EEV positive
horses also had coinfections with either West Nile (5/106, 4.7%), Middelburg (4/106, 3.8%) or African
Horse sickness virus (8/106, 7.6%). To investigate a possible genetic link between EEV strains causing
the observed clinical signs in horses, the full genomes of six isolates were compared to the reference
strains. Based on the outer capsid protein (VP2), serotype 1 and 4 were identified as the predominant
serotypes with widespread reassortment between the seven different serotypes.
