By Mark Andrews

Where you keep your horse can influence the risk of tapeworm infections, according to research from Poland.

The study, by Krzysztof Tomczuk and others of the University of Life Sciences in Lublin, investigated factors affecting tapeworm (Anoplocephala perfoliata) infection in southeastern Poland.

The researchers collected fecal samples from nearly 1,000 horses for the study which ran from 2012 to 2014. Samples came from various farms in southeastern Poland, between the months of October and December. (Previous work by the same research team had shown that late autumn/early winter is the best time of year for detecting tapeworm infections in faecal samples.) They found that the risk of infection increased with the age of the horse. The highest prevalence was noted in the older age group (10 to 20 years of age).

Management and pasture type significantly influenced the level of tapeworm infection.

Horses kept on stud farms showed three times higher prevalence of A. perfoliata (the most common intestinal tapeworm of horses) compared to those kept in individual stables. Horses housed on shared pastures were four times more likely to be infected than those grazing individual paddocks.

Mares had over four times the level of infection of stallions – perhaps because stallions tend to be housed separately.

Horses housed on shared pastures were four times more likely to be infected than those grazing individual paddocks, and mares had over four times the level of infection of stallions. Photo: Canstock/Melory

The moisture level of the pasture also played an important role. Horses kept on boggy pastures had significantly higher levels of infection than did those kept on dry pastures.

The tapeworm’s larval stage (“cysticercoid”) lives in mites (Oribatidae) that inhabit the pasture. In dry conditions these mites tend to stay close to the ground. However, in a moist environment they thrive, becoming more numerous and spreading further up the grass, increasing the risk that horses will ingest them while grazing.

The researchers concluded that the horses at the highest risk of tapeworm infection were mares over ten years of age, kept in herds and grazing on a shared, boggy pasture. They recommend that these animals should be monitored regularly for tapeworm infection and subjected to anthelmintic treatment as necessary.

Printed with permission of Mark Andrews, Equine Science Update.

Survey of Worm Control in the United States

By Mark Andrews

Recommendations for deworming horses have changed over the years to take account of widespread anthelmintic resistance and changing patterns of infection.

Today, the emphasis is on reducing the intensity of anthelmintic treatment. Fecal egg counts are used to identify horses that need treating for cyathostome (small strongyle) infections. Strategic treatments for specific parasites, such as large strongyles, ascarids and tapeworms, are used as necessary. The guidelines also advise the use of routine faecal egg count reduction tests (FECRT) to assess anthelmintic efficacy.

Surprisingly, the last study into equine parasite control in the United States was carried out over 20 years ago.

The recent National Animal Health Monitoring Systems (NAHMS) Equine 2015 Study presented an opportunity to look at the equine parasite control strategies followed by owners in the US and see how closely they followed current guidelines.

The questionnaire-based study approached equine operations in 28 states. Participants provided details of their operation and were questioned about their strategies for deworming and diagnostic testing. A total of 380 respondents provided details.

The findings showed that most owners dewormed two or three times a year, regardless of the age of the horses. The most commonly used anthelmintic was ivermectin.

About 22 percent of participating owners used fecal egg counts, although fewer than 10 percent used them on a regular basis.

Fewer than five percent carried out fecal egg count reduction tests to assess that the anthelmintics they were using were still effective.

Reporting the findings in the journal Veterinary Parasitology, Martin K Nielsen and colleagues suggest there has been little change since the last nationwide survey was conducted in 1998, as most respondents did not report using FECs.

They conclude: “This is in stark contrast to recent European surveys, where 50 to 60 percent of respondents were using FECs routinely. However, the anthelmintic treatment intensity appears to have been lowered compared to 1998. Taken together, these results suggest a continuing need for education and outreach regarding sustainable parasite control.”

Printed with permission of Mark Andrews, Equine Science Update.

This article was originally published in Canada’s Equine Guide 2018, a publication of Canadian Horse Journal.

Photo: Canstock/AFHunta