A questionnaire survey on helminth control on horse farms in Brandenburg, Germany and the assessment of risks caused by different kinds of management.

Control strategies for horse helminths are controversially discussed, and no ideal strategy exists. Presently, the spreading of anthelmintic resistance against all three classes of anthelmintics is of special concern. Advice on how to slow the development of anthelmintic resistance does not seem to have reached the majority of horse owners yet. In our study, we wanted to capture the current standard of helminth control and to analyse the effectiveness of these control strategies. Seven hundred horse farms in Brandenburg, Germany were sent a questionnaire in June/July 2006 asking various questions on farm structure and practices of helminth control. Two hundred thirty-five farms (33.6%) with 6,007 horses in total returned the questionnaire. The number of horses held on each farm varied from 1 to 320. From those returned questionnaires, a random sample of 126 horse farms and 1,407 horses was selected for faecal examination from August to December 2006. The questionnaire results from these farms were correlated with results from the faecal examination to perform risk analysis via multivariate regression. For each farm, results from faecal examination were summarized in index values. Risk was defined as an over-average level of strongyle egg shedding. Risk factors as established by multivariate regression analyses were integrated into three models. Rare deworming and infrequent cleaning of stables were identified as significant risk factors throughout all three models. Additional risk factors could be identified with respect to individual models: elevated percentage of young horses on a farm, not using macrocyclic lactones in the deworming process and dosing anthelmintics on the basis of weight and height. Pasture hygiene did not lead to significant risk reduction, indicating that such measures are inadequately performed on many farms. The questionnaire on its own gave us an insight into control strategies throughout a representative scope of farms in Brandenburg, Germany: faeces were collected from pasture on 22% of horse farms, 79% cleaned out the stables daily. A number of other measures were employed. With respect to anthelmintic use, 21% of the farms stated to use results from faecal examination as a criterion for deworming. We could also identify the most common deworming frequencies, with adult horses being dewormed two times a year (46% of farms) and foals being dewormed four times a year (35% of farms). The frequency ranged from 1 to 7 and 2 to 12 times, respectively.