Be alert for Haemonchus contortus
Published 1 July 2020
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At this point in the summer, be alert to the possibility of haemonchosis in grazing sheep and goats, particularly after heavy rains, as this tropical/subtropical parasite is able to survive in warmer temperatures than our more usual gastro-intestinal (GI) parasites e.g. Teladorsagia circumcincta.
- Clinical signs are anaemia, with no diarrhoea, and sub-cutaneous oedema (bottle jaw) where H. contortus predominates in the host.
- Faecal Trichostrongyle-type egg counts may be high as this parasite has a high biotic potential.
- There is little immunity to this parasite, so disease can be seen in lambs and adults.
- APHA Carmarthen can carry out differential staining on Trichostrongyle- type eggs to detect H. contortus eggs (TC777).
- All classes of anthelmintics have activity against H contortus. In addition nitroxynil and closantel will also kill H. contortus (but not other GI worms).
- Anthelmintic resistance in this parasite is common worldwide, so checking anthelmintic efficacy post treatment is recommended.
- Where haemonchosis is diagnosed in lambs, be alert to the possibility of ewes on the same farm harbouring hypobiotic parasites which may cause disease around lambing time. In this situation, anthelmintic treatment at lambing should be considered.
Figure 2. Haemonchus spp eggs differentially stained with fluorescent stain
