Revised 01/26/26
Phylum Nematoda
Class Chromadorea
Subclass Chromadoria
Rhabditida
Rhabditina
Strongyloidea
Strongylidae Baird, 1853
Parasites of horses, zebras and other equines.
Two subfamilies based on morphology of buccal cavity, either subglobular (Strongylinae) or cylindrical (Cyathostominae)
The Cyathostominae are a group of small strongylids, while the Strongylinae are larger and better known. The two subfamilies are separated morphologically primarily on the characteristics of the stoma and buccal cavity. The Strongylinae are medium-sized to large nematodes with large, subglobular buccal cavities while the Cyclostominae are smaller nematodes with small and cylindeical buccal cavities.
World-wide, horses are exposed to complex intestinal nematode infections which can compromise their health and welfare. These parasites have a high prevalence and are an important cause of morbidity and mortality. Most horses harbor burdens of tens of thousands of these parasites without developing clinical disease, but in some horses, cyathostomin infection leads to a severe inflammatory enteropathy affecting the large intestine.
Intestinal nematodes are difficult to control, not least because there is limited information available on the basic biology of the commonest group of species, the subfamily Cyathostominae. Within this group, there are more than 50 different species and little is known about the contribution that individual species make to the pathogenesis and epidemiology of mixed infections.
The Strongylidae infect virtually all grazing horses. Unlike the large strongyle (Strongylinae) group, anthelminthic resistance is common in the Cyathostominae.
The cyathostomins have a direct life cycle, during which the parasites undergo a period of inhibited development as early third stage larvae in the large intestinal wall. Large numbers of larvae can accumulate and subsequently reactivate simultaneously to cause a syndrome known as larval cyathostominosis. The principle clinical effect of this syndrome is weight loss, but individuals may exhibit other signs including diarrhea and/or subcutaneous oedema and/or pyrexia (Matthews et al., 2004; Lichtenfels et al., 2008).
Beveridge, I., Spratt, D.M. and Durette-Desset, M-C. 2014. Order Strongylida (Railliet and Henry, 1913). In Schmidt-Raesa, A. (ed). Handbook of Zoology: Gastroctricha, Cycloneurelia and Gnathifera. Vol 2. Nematoda. De Gruyter, Berlin
Lichtenfels, J.R.,Kharchenko, V.A., Dvojnos, G.M. 2008. Illustrated identification keys to strongylid parasites (strongylidae: Nematoda) of horses, zebras and asses (Equidae). Veterinary Parasitology 156 :4-161.
Matthews, J.B., Hodgkinson, J.E., Dowdall, S.M.J., Proudman, C.J. 2004. Recent developments in research into the Cyathostominae and Anoplocephala perfoliata. Vet. Res. 35:371–381.
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