A questionnaire study on parasite control practices on Thoroughbred and Standardbred studs in Australia

Information regarding parasite control practices currently used on Thoroughbred and Standardbred studs in Australia is lacking. Questionnaire studies performed in North America, the UK and Europe have documented that control protocols reliant on frequent anthelmintic administration with little or no parasite surveillance are used commonly on horse properties. Anthelmintic resistance (AR) is a global problem with implications for equine health and welfare. The frequent use of anthelmintics in combination with inappropriate management strategies has led to the widespread development of AR. The objectives of this study were to determine parasite control practices used on Thoroughbred and Standardbred studs in Australia and investigate management factors which may be associated with the development of AR. Materials and methodsAn online questionnaire was distributed to 300 studs located in Australia via email. The study was approved by the Charles Sturt University Ethics in Human Research Committee (Approval number 400/2014/28). Information obtained included general property details, grazing management, deworming drug practices (foals and adults), other parasite control practices, use of faecal egg counts (FEC) and perceptions of AR. Univariate analyses were performed and multivariable logistic regression models were developed to assess for associations between management practices and response variables considered to increase the risk of AR and/or parasitic infection. Significance was set at p<0.05.ResultsThere was a 25% response rate to the questionnaire (75/300). Macrocyclic lactones were the most commonly administered anthelmintics in mares and foals and less than 10% of respondents used targeted treatment regimens. For both mares and foals, the majority of respondents administered an anthelmintic at intervals of 2 months. Anthelmintic administration at intervals of >3 months was significantly more likely on more recently established studs (P=0.012) and in association with manure removal (P=0.03). Implementation of pasture hygiene practices was variable and 40% of respondents never removed manure from pasture. While some respondents utilised recommended pasture management practices, these were often undertaken with continued frequent use of anthelmintics. Use of FEC surveillance was less likely on studs that moved horses to a new paddock after treatment (P=0.037). Most respondents (97%) considered AR to be important; however, few were aware of, or implemented, FEC reduction tests for drug efficacy monitoring. Increasing stocking density was associated with the presence of AR on properties (P=0.024). The low response rate and potential for nonresponse bias were the main limitations of this study. Relevance to Australian clinical equine practiceParasite control strategies in Australia remain over-reliant on anthelmintic use. The frequent use of macrocyclic lactones is of concern for the increased selection pressure for AR. Overall, there is a lack of awareness of the importance of non-chemotherapeutic strategies in integrated approaches to parasite control aimed at delaying the development of AR. In an effort to preserve anthelmintic efficiency on horse studs, revision of parasite control strategies is required. There is the potential for greater veterinary involvement in the implementation of more sustainable parasite control practices with greater emphasis placed on surveillance through FEC testing.