Update on equine grass sickness

Surveillance Equine grass sickness (EGS, equine dysautonomia) remains a frequently fatal polyneuropathy of equids. The Animal Health Trust (AHT) continues to host a nationwide surveillance scheme (http://www.equinegrasssickness.co.uk/), in which data from 1410 EGS cases, collated for the decade 2000-2009, were published previously [1]. Since 2010 a further 642 EGS cases have been reported to the surveillance scheme, with 69% occurring in England, 29% in Scotland and 2% in Wales. Reported cases since 2010 ranged in age between 5 months and 48 years, with a median age of 6 years; 48% were geldings, 46% were mares and 6% were stallions. Crossbreeds were most commonly represented (52%), with Welsh Cobs (6%), Thoroughbreds (5%) and Highland ponies (4%) the most commonly reported purebreds. EGS cases were reported in every month of the year since 2010, with 59% occurring during April, May and June, and May seeing the most cases of all months of the year. The most common presentation reported was acute EGS (50%, presenting with colic and surviving <48 hours), with 19% of cases reported as subacute (presenting with colic and surviving 2-7 days). Approximately one-third of cases were reported as chronic EGS (presenting with weight loss, surviving >7 days) and reported survival was 53%. EGS was known to have occurred previously on the same premises as 47% of the reported cases, consistent with presence of ‘higher-risk’ premises.