Small strongyles can develop to infective larval stage in moist straw bedding, study shows

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Stabled horses or donkeys living on a moist layer of deep litter straw could potentially pick up infective cyathostomine larvae if they ate the bedding, researchers report.

The study team, writing in the journal Parasites & Vectors, said domesticated grazing animals, including horses and donkeys, were frequently housed using deep litter bedding systems, where it was commonly presumed that there was no risk of infection by parasites normally associated with grazing at pasture.

The researchers used two different approaches to test whether horses and donkeys could become infected with cyathostomines, also known as small strongyles, from eating deep litter straw bedding.

Sandy Love, Faith Burden, Eoghan McGirr, Louise Gordon and Matthew Denwood described the outcomes of three separate complementary studies in which they used temperature-controlled horticultural incubators to assess the ability of straw bedding to grow the larvae.

They showed that small strongyles – the most numerous parasites in horses – were capable of developing to their infective third-stage larvae on moist straw bedding.

“It is therefore possible for a horse or donkey bedded in deep litter straw to become infected by ingesting the contaminated straw,” they concluded.

“This has implications for parasite control in stabled equids and potentially in housed ruminants, and further investigation is required in order to establish the relative infective pressure from pasture versus straw bedding.”

The researchers used the incubators to simulate three straw-bedding scenarios and one grass turf control. The straw-bedding variations were dry straw, watered clean straw, and watered contaminated straw, in which deep litter straw bedding collected from a horse stable was used as a bottom layer. Faecal pats were placed in each of the incubators.

No nematodes other than cyathostomine larvae and free-living larvae were identified from the samples in the studies. Free-living larvae were detected in about 20% of the deep litter and turf plots during monitoring over 2- to 3-week periods.

To provide further validation, 24 samples of straw bedding were collected over an eight-week period from six barns in which a large number of donkeys lived. Of the 24 samples, 18 were positive for cyathostomine larvae.

Third-stage cyathostomine infective larvae were found on straw bedding samples from each of the six individual donkey barns on at least one occasion.

Love, McGirr and Dawson are affiliated with the University of Glasgow in Scotland; Denwood with the University of Copenhagen in Denmark; and Burden with The Donkey Sanctuary in Britain.

Equine Cyathostominae can develop to infective third-stage larvae on straw bedding
Sandy Love, Faith A. Burden, Eoghan C. McGirr, Louise Gordon and Matthew J. Denwood.
Parasites & Vectors 2016 9:478 DOI: 10.1186/s13071-016-1757-1

The study, published under a Creative Commons License, can be read here

Earlier report

 

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