The reappearance of eggs in faeces of horses after treatment with ivermectin.

This study has investigated the re-emergence of nematode eggs in horse feces after treatment with ivermectin, showing that the cyathostome larvae almost entirely dominate the cultures after treatment.

Research Methodology and Demographics

• The study was conducted on 104 horses from 10 different farms during their stabling period, using ivermectin to treat nematode infections.
• Fecal samples from these horses were collected on a weekly basis for egg count analysis.
• This research continued until the mean egg output per farm reached above 10% of the pre-treatment egg output, which happened 63 days post-treatment.

Findings Prior to Treatment

• Before ivermectin treatment, the cultures derived from faeces were composed of 95.9% cyathostome type larvae.
• Apart from the cyathostome type, small numbers of other species were detected: Gyalocephalus capitatus, Strongylus vulgaris, S. edentatus, Oesophagodontus/Poteriostomum spp., Triodontophorus spp., and Trichostrongylus axei.

Findings After Treatment

• Post-treatment, almost all cultures produced only cyathostome larvae.
• While the dominance of cyathostome type larvae was more pronounced after treatment, occasionally (<1%), low numbers of large strongyles were seen. These were mainly S. edentatus, with exceptionally rare appearances of S. vulgaris and Oesophagodontus spp.
• Also, Trichostrongylus axei was observed in minor proportions after treatment.

Implications of The Study

• The research demonstrates that the usage of ivermectin as a treatment does not entirely prevent the reappearance of nematode eggs in the faeces of horses.
• Cyathostome larvae seem to be resistant or less susceptible to ivermectin treatment, as they were the dominant species noted in cultures after treatment.
• The study highlights the need for more comprehensive treatment and preventative strategies for nematode infections in horses.