Revised 02/26/24
Small redworms or small strongylids
Cyathostominae
Intestinal parasites of horses, zebras and other equines.
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 Cyclostominae are smaller nematodes with small and cylindrical buccal cavities while the Strongylinae are medium-sized to large nematodes with large, subglobular 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 of which 10 seem most prevalent; little is known about the contribution that individual species make to the pathogenesis and epidemiology of mixed infections. The systematics of the group have been difficult and efforts have been made to revise and consolidate the taxonomy (e.g. Lichtenfels et al., 1998).
The Strongylidae infect virtually all grazing horses. Unlike the large strongyle (Strongylinae) group, anthelmintic 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 diarrhoea and/or subcutaneous oedema and/or pyrexia (Matthews et al., 2004; Lichtenfels et al., 2008).
Management is centered on repeated dosages of anthelminthics, but development of resistance to the drugs is a problem (Corning, 2009).
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Strongylid bursa |
Species of the Cyathostominae have a direct lifecycle, with no intermediate host.The third larval stage (L3) develops in feces deposited iin areas where animals are grazing. The ingested larval nematodes continue their maturation through subsequent sthegs to the adult and new eggs may be deposited in feces in 5-6 weeks. Eggs hatch in the feces and larvae develpo to the third stage when they enter an apparent dauer stage surrounded by an extra protective cuticle. They are able to survive in the grazing area for prolonged periods. Once ingested, the encysted L3 nematodes may remain encysted in the intestinal wall for periods up to 2 years. In temperate climates, the nematodes tend to enter the dauer stage during cooler months while in tropical areas the dauer stagwe may be entered in the summer as a protection against heat (Corning, 2009).
Host may be in poor condition with diarrhoea, a serum albumin concentration of less than 20 g/L. There may be anaemia wand a large numbers of cyathostomin larvae in feces.
In the tissues of the host, inflammation of colon and/or cecum, mucosal thickening and irregular areas of congestion. Numerous small strongyle larvae occur in the mucosa. In acute infections there is mucosal hyperaemia, haemorrhage, congestion, ulceration or necrosis (Corning, 2009)..
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
Corning, S. 2009. Equine cyathostomins: a review of biology, clinical significance and therapy. Parasites & Vectors 2(Suppl. 2) S1 doi: 10.1186/1756-3305-2-S2-S1
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.
Lichtenfels, J.R., Karchenko, V.A., Krecek, R.C., Gibbons, L.M. 1998. An annotated checklist by genus and species of 93 species level names for 51 recognized species of small strongyles (Nematoda: Strongyloidea: Cyathostominea) of horses, asses and zebras of the world. Veterinary Parasitology 79:65-79.
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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