Horses are commonly infected with gastrointestinal nematodes, trematodes and cestodes.
1. Gastronintestinal Nematodes (Round Worms)
The most important worms found in horses are:
- Large strongyles (Strongylus spp.)
- Small strongyles (Cyathostomes)
- Large roundworms (Ascarids)
Other less common worms are listed in Table 3.1 and include:
- Intestinal threadworm (Strongyloides westeri)
- Stomach worms (Trichostrongylus axei)
- Pinworm (Oxyuris equi)
2. Trematodes (Flukes)
- Liver fluke (Fasciola hepatica) is an important parasite of horses in certain areas where conditions are suitable for the intermediate host, an aquatic snail.
- Stomach fluke (such as Paramphistomum spp or Calicopheron spp) occasionally cause disease, mainly in coastal areas.
3. Cestodes (Flatworms)
- Tapeworm (Anoplocephala perfoliata)
4. Bots (Gastrophilus spp.)
- Bots are the larvae of a fly not worms. They will not be detected during a WEC.
5. Coccidia (Eimeria)
- Coccidia are microscopic protozoal parasites not worms..
COMMON HORSE WORMS (Table 3.1)
|Common Name||Scientific Name|
|Most Important Roundworms|
|Large strongyles||Strongylus spp.|
|Large roundworms||Parascaris equorum|
|Intestinal threadworm||Strongyloides westeri|
|Stomach worms||Trichostrongylus axei|
|Liver fluke||Fasciola hepatica|
Source: Beveridge, I., Gasser, R., Sangster, N. (2015). Horses. In: Beveridge, Ian, and Emery, David, (eds.) Australasian Animal Parasites: Inside & Out. Australian Society for Parasitology, pp. 792-841
GUIDE TO WORM EGG COUNTS IN HORSES – Table 3.2
|Worm egg count (epg)||Interpretation / comments|
|0 - 100*||A good result. There would be few situations where you would contemplate drenching at this level. Check egg counts in 4-6 weeks after significant rain.|
|100 - 200*||Low egg count result. Treatment may be required in younger animals or animals under stress. If not treated check egg counts in 4 weeks time.|
|200 - 500*||Moderate egg count result. Treatment would be advisable in most cases.|
|Above 500*||High egg count result. Treatment required.|
*strongyle eggs per gram of faeces (epg)
Source: Anne Oakenful, (2008). Revised by Stephen Love, September 2013. NSW DPI Faecal Egg Counts for Worms Manual.