Poor efficacy of the most commonly used anthelmintics in sport horse nematodes in Morocco in relation to resistance.

This research investigates the inefficacy of commonly used anti-parasitic drugs in treating nematodes (worms) that infect sport horses in Morocco. It notably discovers for the first time, the resistance to certain drugs among African horses outside South Africa.

Context and Method of the Research

• The study focuses on the treatment of sport and leisure horses in Morocco against nematodes with several anti-parasitic drugs. This such as organophosphates (dichlorvos), benzimidazoles (thiabendazole), and tetrahydropyrimidines (pyrantel pamoate).
• The researchers studied three horse stables in Rabat, one in Meknes, and one in Bouznika.
• Two of the stables in Rabat and Bouznika imported a significant number of horses from Argentina and Europe, where resistance to benzimidazoles have been documented.
• In contrast, the Meknes stable did not import any horses from foreign countries.

Treatment Frequency and Efficacy

• The study found that treatment was not administered very frequently, with adult horses being treated just twice a year.
• However, the same anti-parasitic drugs were used repeatedly.

Nematode Resistance to Medications

• The study importantly revealed a lack of resistance to the organophosphate dichlorvos, which still appears to remain effective in treating the nematodes.
• Concerningly, however, resistance to benzimidazole and pyrantel pamoate was observed for the first time in African horses outside South Africa. This finding implies that over-reliance on, and repetitive use of, certain drugs can lead to the development of resistance, decreasing the effectiveness of these drugs over time.
• This development has crucial implications for the treatment and management of nematode infections in horses across Africa.