Patterns of variation in equine strongyle community structure across age groups and gut compartments

Abstract

Background Equine strongyles encompass more than 64 species of nematode worms that are responsible for growth retardation and the death of animals. The factors underpinning variation in the structure of the equine strongyle community remain unknown. Methods Using horse-based strongyle community data collected after horse deworming (48 horses in Poland, 197 horses in Ukraine), we regressed species richness and the Gini-Simpson index upon the horse’s age, faecal egg count, sex and operation of origin. Using the Ukrainian observations, we applied a hierarchical diversity partitioning framework to estimate how communities were remodelled across operations, age groups and horses. Lastly, strongyle species counts collected after necropsy (46 horses in France, 150 in Australia) were considered for analysis of their co-occurrences across intestinal compartments using a joint species distribution modelling approach. Results First, inter-operation variation accounted for > 45% of the variance in species richness or the Gini-Simpson index (which relates to species dominance in communities). Species richness decreased with horse’s age (P = 0.01) and showed a mild increase with parasite egg excretion (P < 0.1), but the Gini-Simpson index was neither associated with parasite egg excretion (P = 0.8) nor with horse age (P = 0.37). Second, within-host diversity represented half of the overall diversity across Ukrainian operations. While this is expected to erase species diversity across communities, community dissimilarity between horse age classes was the second most important contributor to overall diversity (25.8%). Third, analysis of species abundance data quantified at necropsy defined a network of positive co-occurrences between the four most prevalent strongyle genera. This pattern was common to necropsies performed in France and Australia. Conclusions Taken together, these results show a pattern of β-diversity maintenance across age classes combined with positive co-occurrences that might be grounded by priority effects between the major species. Graphical Abstract

Strongylids of Domestic Horses in Eastern Slovakia: Species Diversity and Evaluation of Particular Factors Affecting Strongylid Communities

“…[ 40 ]. Thus, in this study, we could observe the same tendency of decreasing the proportion of large strongylids in the horse parasite community and the dominance of cyathostomins, as was indicated in recent decades worldwide [ 5 , 6 , 25 – 27 ; 30 ]. Also, we could observe an increase in the dominance of one of the most prevalent cyathostomin species, C. catinatum (the Berger-Parker dominance index of 0.41).…”

“…An individual horse may be co-infected with as many as 15–25 species of strongylids [ 5 , 6 , 17 – 19 ]. Accordingly, the horse strongylid community has a complex structure [ 5 , 8 ; 20 – 25 ]. The prevalence and proportion of each species in the strongylid community may vary depending on the age, sex, and horse-management conditions, in particular, the frequency of anthelmintic treatments [ 5 , 22 ].…”

“…Meta-analysis of published data collected worldwide revealed that three cyathostomin species (Cylicocyclus nassatus, Cylicostephanus longibursatus, and Cyathostomum catinatum) were the most prevalent and relatively abundant species of equine strongylids [6]. Simultaneously, the species composition of strongylid communities varies in different countries [25]. In Europe, horse strongylid studies have been performed in different countries for more than 50 years [5,8,20,22,23,[28][29][30][40][41][42][43][44].…”

Molecular Species Determination of Cyathostomins from Horses in Ireland

“…Following infection, cyathostomin larvae penetrate into the mucosa of the large intestine, and can remain here in a dormant (hypobiotic) state, emerging to mature and establish patent infection in the lumen after a variable pre-patent period of up to three years (Gibson, 1953; Nielsen and Lyons, 2017). The hypobiotic state is relevant to anthelmintic efficacy and to cyathostomin-associated disease (Boisseau et al ., 2023; Morariu et al ., 2016). Typically, of the total worm burden in an individual animal, the majority will comprise hypobiotic larvae in the mucosa (Dowdall et al ., 2002; Duncan et al ., 1998; Gibson, 1953; Matthews, 2008).…”