Control of cambendazole-resistant small strongyles (Population S) with oxibendazole in a pony band: an 8 year field test (1984-1992).

The research article discusses a longitudinal field study investigating the effectiveness of the drug oxibendazole on small strongyles (a type of parasite) in a group of ponies, which showed a decline in effectiveness over a period of fourteen years.

Introduction and Background

• The study took place over 18 years, starting in 1974, focusing on a population of ponies harbouring small strongyles resistant to the drug cambendazole.
• For the first 4 years, the ponies were treated with cambendazole, with the subsequent 14 years of treatment involving the use of oxibendazole (OBZ).
• Prior studies and data covered the first ten years of this research period.
• This specific article presents the data collected over the last eight years of research, i.e., between 4th October 1984 to 11th September 1992, which correspond to years seven through fourteen of treatment with OBZ.

Methodology

• To gauge the effectiveness of the OBZ treatment, researchers carried out pre- and post-treatment counts of strongyle eggs (referred to as epg) and larvae (referred to as lpg), bi-weekly, per gram of feces for the entire duration of the study.

Results

• The outcome of the research indicated that the average annual percentage reductions in epg counts, as a result of OBZ treatments, ranged between 51%, 53%, 38%, 38%, 39%, 28%, 40%, and 19% for each of the seven through fourteen years, respectively.
• The study also disclosed similar levels of reduction in lpg counts over the same period.
• Initially, the treatment with OBZ proved highly effective on this population of small strongyles. However, over time, both the epg and lpg counts gradually declined.
• Despite this decline, from the research’s fifth year onwards, the counts remained more or less consistent.
• The study revealed that the reduction levels were at their lowest during the final year of the research.