Compilation of 29 years of postmortem examinations identifies major shifts in equine parasite prevalence from 2000 onwards

Abstract

Horses are infected by a wide range of parasite species that form complex communities.Parasite control imposes significant constraints on parasite communities whose monitoring 2 1 remains however difficult to track through time. Postmortem examination is a reliable method to quantify parasite communities. Here, we compiled 1,673 necropsy reports accumulated 2 3 over 29 years, in the reference necropsy centre from Normandy (France). The burden of non-strongylid species was quantified and the presence of strongylid species was noted. 5Details of horse deworming history and the cause of death were registered. Building on these data, we investigated the temporal trend in non-strongylids epidemiology and we 2 7determined the contribution of parasites to the death of horses throughout the study period.Data analyses revealed the seasonal variations of non-strongylid parasite abundance and reduced worm burden in race horses. Beyond these observations, we found a shift in the species responsible for fatal parasitic infection from the year 2000 onward, whereby fatal 3 1 cyathostominosis and Parascaris spp. infection have replaced death cases caused by S. vulgaris and tapeworms. Concomitant break in the temporal trend of parasite species 3 3 prevalence was also found within a 10-year window (1998-2007) that has seen the rise of Parascaris spp. and the decline of both Gasterophilus spp. and tapeworms. A few cases of 3 5parasite persistence following deworming were identified that all occurred after 2000.Altogether, these findings provide insights into major shifts in non-strongylid parasite 3 7prevalence and abundance over the last 29 years. They also underscore the critical importance of Parascaris spp. in young equids.

Intestinal Strongyle Genera in Different Typology of Donkey Farms in Tuscany, Central Italy

“…Interestingly, large strongyles were identified only in the organic farm included in this study, in which anthelmintic treatments are strictly limited by the European law [44][45][46]. As previously evidenced in horses [39,42], this finding reinforces that the drug restriction could be linked with the lower anthelmintic selection pressure in this latter farm in relation to the other examined farms. However, further studies are needed to confirm the effect of this type of management on the genera/species composition of donkey intestinal strongyles.…”

“…More specifically, Strongylus spp. prevalence has drastically decreased over time in horses and donkeys [39], whereas cyathostomin infections have become a major issue [39,40]. Cyathostomins were also prevalent in 100% of the farms in horses in South America [41].…”

Meta-analysis of cyathostomin species-specific prevalence and relative abundance in domestic horses from 1975–2020: emphasis on geographical region and specimen collection method

“…Cyathostomins cause the rare but often fatal clinical syndrome, larval cyathostominosis [11,12], and exhibit emerging or widespread resistance to all currently available anthelmintic drug classes [13]. Cyathostomins are thusly the most important gastrointestinal parasites of horses weaning age and older [14,15]. Despite this, species-specific research on basic cyathostomin biology and ecology or on population and epidemiological dynamics involved in clinical disease and anthelmintic resistance is wanting.…”

Integrative biology defines novel biomarkers of resistance to strongylid infection in horses

“…These small strongyles locate in their host hindgut and are responsible for growth retardation in young animals 7,8 . The massive emergence of developing larval stages from the caeco-colic mucosa can cause a larval cyathostominosis syndrome 9 that remains a leading cause of parasite-mediated death 10 .…”