Possible resistance of small strongyles from female ponies in The Netherlands against albendazole.

This research focuses on the study of resistance to the drug albendazole in small strongyles (a type of parasitic worm) found in female ponies in The Netherlands. The study found varying effectiveness of the drug, suggesting potential resistance.

Study Design

• The researchers selected six female ponies, divided into two groups. Group 1 ponies grazed on a pasture from May to November 1985 and were treated with 7.5 mg of albendazole per kg of body weight. This treatment was administered orally two days before they started grazing in May and was repeated in June and July.
• Group 2 consisted of ponies that grazed on a similar pasture from May to July and were treated with the same dose of albendazole. After July, they were moved to a different pasture until November.
• In December, both groups were treated with the same dose of albendazole. Eight days later, they were euthanized, and a post-mortem was conducted to analyze the presence and growth of small strongyles.

Findings

• The worm egg count in the ponies’ feces suggested that the May treatment for group 1 and the July treatment for group 2 were more effective than later treatments. This indicates the possibility of worm resistance to the drug.
• There were more small strongyles in Group 1 ponies than in Group 2, suggesting that the regularity of treatment or the grazing environment could have affected the parasite count.
• Treatment was not equally effective against all stages of small strongyles. The results were not as effective against the parasitic 3rd and 4th stage larvae of the worm.
• At autopsy, fifteen species of small strongyles were identified. The drug’s efficacy varied across these species, indicating that albendazole may not be equally effective against all species of this parasite.
• The resistance against albendazole was particularly noticeable in adult Cyathostomum coronatum, Cya labratum, Cylicostephanus calicatus, and Cyl poculatus species in both groups, implying a species-specific resistance.
• The drug was 100% effective against Cya catinatum, Cyl goldi, and five other species that were found in low numbers, providing a contrast in drug efficacy depending on the species of the worm.

This study provides valuable insights into the potential resistance of small strongyles to the drug albendazole and highlights the need for further research into alternative treatments or combating resistance in these parasites.