Benzimidazole resistance in small strongyles of horses.

The research article discusses a study wherein treatments of mebendazole, cambendazole and febantel proved ineffective in reducing the faecal egg count in horses infected with small strongyle species. The research also suggests that this resistance extended to fenbendazole but not to morantel tartrate.

Study Overview

In this research, an investigation was conducted on 40 horses infected with small strongyle species, commonly known as horse roundworms. These parasites can cause issues such as digestive problems in horses. To address this issue, the horses were treated with various kinds of drugs such as mebendazole, cambendazole, febantel and fenbendazole.

• The effectiveness of the treatments was assessed based on faecal egg count i.e., the number of parasite eggs present in the horse’s faeces.
• The researchers observed that treatments with mebendazole, cambendazole and febantel did not bring any significant reduction in the faecal egg count, suggesting strong resistance developed by the parasites against these drugs.
• Moreover, it was found that this resistance also extended to another drug, fenbendazole.

Exception to Resistance against Drugs

On an interesting note, the researchers identified that there was one drug that still proved effective against these parasites.

• Horses that were given doses of morantel tartrate showed significant reduction in the faecal egg count. In fact, counts were reduced to zero within 7 days after the administration of this treatment.

Causes of Resistance Development

The research goes one step further and discusses potential causes leading to this resistance development in small strongyle species.

• One important factor that was identified is the horses’ previous treatments. This suggests that the parasites may have developed resistance over time due to the continuous use of these drugs.
• The specific mode of action of febantel was also discussed in regard to this issue of resistance. The drug acts by affecting the energy metabolism of parasites and disrupting their energy utilization at microtubular level. The resistance might suggest an adaptation or mutation in the parasite that allows it to survive despite the drug’s effects.