Use of a reverse line blot assay to survey small strongyle (Strongylida: Cyathostominae) populations in horses before and after treatment with ivermectin.

This research article discusses the application of a PCR hybridization assay for monitoring small strongyle infestations in horses and the effectiveness of an anthelmintic drug ivermectin on them. The results found 11 species of small strongyle before treatment and a somewhat altered population after treatment, suggesting this method could be useful for future study of drug resistance.

Experimental Design

• The research utilized a sensitive and specific technique named PCR (Polymerase Chain Reaction) hybridization assay for the species-specific monitoring of small strongyle populations. Small strongyles are parasitic worms that infest horses.
• Samples were collected both before and after treatment with an anthelmintic drug, ivermectin, which is used to treat various types of parasitic infections.
• The sampling was done weekly on eight horses, four foals and four yearlings, over the course of six weeks. The researchers focused on the count of strongyle eggs present in the horses’ feces (EPGs).
• In addition to the treated horses, two horses served as controls; one was not treated with ivermectin and the other was from a separate herd known to be infected with Strongylus spp., a different species of parasites.
• The researchers extracted genomic DNA from approximately 6000-7000 eggs in the fecal samples.

Methodology

• In order to identify the parasitic species, the researchers amplified the intergenic spacers (IGSs) of ribosomal DNA (rDNA) of small and large strongyles.
• Followed by this, a reverse line blot (RLB) assay was performed to identify the presence of the 12 most common equine small strongyle species and to distinguish them from Strongylus spp.

Results

• Before treatment, the assay identified 11 species of small strongyle. However, four weeks after the treatment with ivermectin, only eight small strongyle species were identified. The dominant four among them were Cylicocyclus nassatus, Cylicostephanus longibursatus, Cylicostephanus calicatus, and Cylicostephanus minutus.
• At 5 and 6 weeks post-treatment, the small strongyle population was almost the same as before treatment.
• Strongylus spp. parasites were identified only in the samples from the positive control horse.

Conclusion

• The study demonstrated the efficacy of the PCR-RLB technique for distinguishing between different species of equine strongyle eggs. This could be significant for further research into drug-resistance studies in parasites.