[A survey on anthelmintic resistance in Strongyles to ivermectin and pyrantel and macrocyclic lactone-resistance in Parascaris equorum].

This study investigates the resistance of horse parasites, particularly the Parascaris equorum, to various antiparasitic drugs. It was found that the parasites were resistant to certain drugs known as macrocyclic lactones, but were effectively treated with a double dose of a drug called pyrantel. In the case of another parasite, strongyles, no resistance was detected towards ivermectin or pyrantel.

Background and Purpose

• The research was conducted on a horse farm that had previously detected resistance in the horse parasite Parascaris equorum to a group of antiparasitic drugs, referred to as macrocyclic lactones.
• The main purpose was to obtain up-to-date data on the efficiency of these drugs against the parasite, and to see if a similar resistance problem existed in another parasite known as strongyles.

Methodology of the Study

• The research was divided into two parts. In the first part, a drug called abamectin was administered to horses infected with P. equorum. Subsequently, horses that still tested positive for the parasite were treated with another drug, pyrantel pamoate, and the successfulness of the treatment was measured.
• The remaining horses, still infected, were given a double dose of pyrantel, and the efficacy of that treatment was reported.
• In the second part of the study, the efficiency of the drugs ivermectin and pyrantel against the parasite strongyles was evaluated.

Results of the Study

• The study found that in 11 out of 12 horses, abamectin did not have any impact on the P. equorum parasite. This demonstrated resistance to the drug.
• When horses that remained infected were treated with pyrantel, the effectiveness varied greatly from 0-80% in three horses, to 96-100% efficacy in eight horses. However, a double dose of pyrantel effectively eliminated the P. equorum infection in all horses.
• In contrast, both ivermectin and pyrantel were 100% effective against the strongyles parasite at 14 and 28 days after treatment. This demonstrated no resistance to the medications in this parasite.

Conclusion

• The researchers concluded that macrocyclic lactone anthelmintics, a group of drugs including abamectin and ivermectin, were ineffective against P. equorum. However, a double dose of pyrantel effectively treated the resistant worms.
• In the case of strongyles, the parasites showed no resistance to either ivermectin or pyrantel. This indicates that these drugs could provide effective treatment for the strongyle infections.