Compilation of 29-yearpostmortemexaminations identifies major shifts in equine parasite prevalence from 2000 onwards

Abstract

0Horses are infected by a wide range of parasite species that form complex communities. 1Parasite control imposes significant constraints on parasite species assemblage whose 2 2 monitoring remains however difficult to track through time. Postmortem examination is a 2 3 reliable method to quantify parasite communities. Here, we compiled 1,673 necropsy reports 2 4 accumulated over 29 years, in the reference necropsy centre from Normandy (France). The 2 5 burden of non-strongylid species was quantified. Details of horse deworming history and the 2 6 cause of death (resulting from a parasitic infection or not) were registered. Data analyses 2 7 revealed the seasonal fluctuations of non-strongylid parasite species and the least exposure 2 8of race horses to these parasites. Beyond these observations, we found a shift in the species 2 9 responsible for fatal parasitic infection from the year 2000 onward, whereby fatal 3 0 cyathostominosis and Parascaris spp. infection have replaced death cases caused by S. 3 1 vulgaris and tapeworms. Concomitant break in the temporal trend of parasite species 3 2prevalence was also found within a 10-year window (1998)(1999)(2000)(2001)(2002)(2003)(2004)(2005)(2006)(2007)) that has seen the rise of 3 3Parascaris spp. and the decline of both Gasterophilus spp. and tapeworms. A few cases of 3 4 parasite persistence following deworming were identified that all occurred after 2000.3 5Altogether, these findings provide a unique assessment of the major remodelling of equine 3 6 parasitic communities over the last 29 years. They also underscore the critical importance of 3 7Parascaris spp. in young equids.3 8 3 9