Parasite control practices on Swedish horse farms

Abstract

Background: 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.

Methods: 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.

Results: 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.

Conclusion: 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.

Figure 1

Percentage of respondents who removed manure weekly or never did it. Other options are not displayed in the figure.

Figure 2

Times of the year considered to being the most important for de-worming (n = 387).

Figure 3

Frequency distribution of anthelmintic treatments performed during the previous 12 months. Note that numbers add up to more than 100 because the horses are dewormed more than once per year.

Figure 4

Usage of different anthelmintic drugs at various times of the year. BZ – benzimidazoles; Pyr – pyrantel; Mox – moxidectin; Ivo – ivermectin.

Figure 5

The proportion of respondents (n = 444) who had personal experience of helminth related problems in their horses.