The elimination of equine strongyles and hematological and pathological consequences following larvicidal doses of thiabendazole.

This study tests the effects of using the drug thiabendazole (TBZ) in varying dosages on horses infected with different levels of strongyle parasites. The results showed promising potential for TBZ in eliminating these parasites, although side effects were noted, including one death that may have been related to treatment.

Methodology

• The research involved twelve horses separated into three groups, each subjected to varying degrees of strongyle infection: light, moderate, and heavy.
• This was achieved by administering mixed species strongyle inoculum at specific doses.
• For each group, three weeks after initial larval inoculation, three horses were given larvicidal doses of TBZ for two consecutive days. One horse per group was not medicated and served as a control.
• This TBZ treatment was then repeated after another three weeks.
• Post-treatment, long-term studies were conducted on one horse from each group. The remaining horses were necropsied to understand their post-treatment parasite loads.

Results

• The treatment caused side effects such as depression, lethargy, and anorexia in horses, which lasted for five days.
• Eosinopenia, lymphopenia, and neutrophilia were also observed in treated horses for about three days.
• Six out of twelve horses developed moderate eosinophilia due to strongylosis (the condition of being infected with strongyles).
• A concerning finding was the death of a horse during the course of TBZ treatment, as a possible result of mis-dosing or an anaphylactic reaction.
• Necropsy revealed active thrombi in the anterior mesenteric artery in parasitized horses, though this was not found in TBZ-treated ones.
• Among the seven treated horses, five were completely free from both adult and larval strongyles. The remaining two had minimal remnants of the parasites.
• Importantly, no Strongylus vulgaris larvae or adults were found in any horse treated with TBZ.

Conclusion

• The research shows the potential of TBZ as an effective treatment for strongylosis in horses. However, side effects from the treatment need to be mitigated for safer treatment protocols.
• Further research and trials may help refine dosages and reduce negative effects, maximising the benefits of TBZ in treating equine strongyles.