Research Article: Parasite control practices on Swedish horse farms

Date Published: September 26, 2007

Publisher: BioMed Central

Author(s): Eva Osterman Lind, Erik Rautalinko, Arvid Uggla, Peter J Waller, David A Morrison, Johan Höglund.


Virtually all horses are infected with helminth parasites. For some decades, the control of parasites of Swedish horses has been based on routine treatments with anthelmintics, often several times per year. Since anthelmintic resistance is becoming an increasing problem it is essential to develop more sustainable control strategies, which are adapted to different types of horse management. The aim of this study was to obtain information on practices used by Swedish horse owners for the control of endoparasites.

A questionnaire with 26 questions about management practices and parasite control routines was posted to 627 randomly selected horse establishments covering most types of horse management in Sweden.

The response rate was good in all categories of respondents (66–78%). A total of 444 questionnaires were used in the analyses. It was found that virtually all horses had access to grazing areas, usually permanent. Generally, pasture hygiene was infrequently practiced. Thirty-six percent of the respondents clipped or chain harrowed their pastures, whereas weekly removal of faeces from the grazing areas was performed by 6% of the respondents, and mixed or rotational grazing with other livestock by 10%. The number of anthelmintic treatments per year varied from 1–8 with an average of 3.2. Thirty-eight percent considered late autumn (Oct-Dec) to be the most important time for deworming. This finding, and an increased use of macrocyclic lactones in the autumn, suggests a concern about bot flies, Gasterophilus intestinalis. Only 1% of the respondents stated that faecal egg counts (FEC) were performed on a regular basis. The relatively high cost of FEC analyses compared to purchase of anthelmintics was thought to contribute to the preference of deworming without a previous FEC. From the study it was evident that all categories of horse owners took advice mainly from veterinarians.

The results show that routines for endoparasite control can be improved in many horse establishments. To increase the knowledge of equine endoparasite control and follow the recommendations for how to reduce the spread of anthelmintic resistance, a closer collaboration between parasitologists and veterinary practitioners is desirable.

Partial Text

The horse is host to a great number of gastrointestinal helminths, of which nematodes of the family Strongylidae, the roundworm Parascaris equorum and the cestode Anoplocephala perfoliata are the most important. These parasites are ubiquitous and have been recognised as significant causes of clinical disease in horses. A previous Swedish study has shown that 2–3 year-old horses on stud farms, particularly in the south of the country, often shed high numbers of strongyle eggs [1]. Although the occurrence of the most pathogenic species, Strongylus vulgaris, has decreased markedly during the past 3 decades, eggs of this nematode were still found in samples from 14% of the investigated farms [1]. Furthermore, studies of A. perfoliata have revealed a high prevalence of this parasite in horses of all ages [2].

A questionnaire on management practices and parasite control routines was developed and tested on 60 horse owners in a pilot study prior to commencing the main study. Subsequently the form was slightly revised, and the final version comprised 26 questions, of which 3 were open-ended and the rest closed (Table 1). In order to include the main types of horse establishments in the study, names of respondents were obtained from the following lists:

The overall response rate was good for all types of farms. However, valid conclusions may be drawn only if the returned questionnaires are representative of all Swedish horse establishments. We consider this likely to be true. First, a representative range of establishments was targeted for the survey. Second, the response rate was high across all categories of establishments. Third, we attempted to independently verify the accuracy of our data. For example, anthelmintic treatments as described by the respondents to the survey were compared to statistics on the sales of anthelmintic drugs for horses, and they were found to be in agreement.

EOL was responsible for the design of the study, performance of the pilot study, the distribution of the questionnaire and writing the draft of the manuscript. ER contributed in the design of the study and in the formulation of questions. AU, PJW and JH participated in the design of the study and helped to word the final version of the manuscript. DAM did most of the data analyses and the interpretation of these.




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