Prevention and Management of Endoparasites in Foals

Parasite control in foals remains more challenging than for any other age group. The young animals are more susceptible to parasite infection than more mature horses and anthelmintic resistance is particularly problematic in foals. In many cases, the anthelmintics that still work against P. equorum have little effect against cyathostomins, and vice versa.

Strongyloides westeri
This parasite was once suspected to be the cause of foal heat diarrhoea, but there is now general agreement that this is not the case. The scientific literature contains one study suggesting an association between diarrhoea and S. westeri egg counts exceeding 2000 eggs per gram (EPG) (Netherwood et al. 1996). However, eggs are often recovered from clinically healthy individuals, and overall there is little evidence for S. westeri being a severe pathogen. It is widely practised to deworm mares with a larvicidal anthelmintic around foaling to interrupt lactogenic transmission of this parasite. While it is possible that this has reduced the prevalence of S. westeri, there is no evidence to verify this. [...]