Autumn and winter worming

Posted by Wormers-direct on 8th Jan 2020

Autumn and winter worming

During the autumn and early winter the focus of any responsible and sustainable worming programme should be on the management of tapeworm and encysted small redworm – neither of which show up in a standard FWEC. A veterinary advisor explains how these parasites can be tackled to the best effect.

The truth about tapeworm

Tapeworms are very common in UK horses1, 2but their definitive life cycle is still not completely understood. What we do know is that tapeworm infection can be linked to potentially serious colic 3. We also know that a faecal worm egg count won’t definitively identify a tapeworm burden and that not all wormers are effective against this parasite.Although tapeworm infection shows no strong seasonality, exposure is greater during periods of prolonged grazing. Consequently, treatment should be undertaken in the autumn following summer turnout on pasture 4, with repeat treatments usually recommended every six months5.

The treatment for tapeworm in horses involves either a double-dose of a pyrantel-based wormer or a wormer containing Praziquantel. The latter is regarded as offering an effective single dose treatment for the control of equine tapeworms.

The time-bomb effect of encysted small redworm

Encysted small redworm larvae may account for up to 90% of the redworm burden in your horse6. Even if the horse has shown a negative or low count it could still be harbouring several million of these dormant parasites, hidden within the gut wall7.  Encysted small redworm can remain dormant inside a horse for up to two years, but they usually ‘wake-up’ in the late winter or early spring, developing and emerging from the gut wall all at the same time. In severe infestations this can lead to a disease syndrome known as ‘larval cyathostominosis’, causing diarrhoea and colic with up to a 50% mortality rate7. Treating encysted small redworm successfully in the late autumn or early winter is important in order to minimise this serious risk.

Moxidectin is recognised as the only single dose treatment for encysted small redworm. It has been shown to kill the larvae in-situ, without resulting in severe inflammation of the gut wall that other multi-dose treatments may cause8. In addition, Moxidectin is licensed for persistent activity against small redworms, killing larvae ingested as the horse grazes for up to two weeks after treatment.

1. Lyon S et al, Veterinary Record (1995) 147, 456-457

2. Owen RH et al, Veterinary Record (1998) 123, 562-563

3. Proudman CJ Journal of Equine Veterinary Science (2003) 23 (1) 6-9

4. Proudman CJ et al Equine Veterinary Journal (1998) 30 (3) 194-199

6. Bairden K. et al (2001) Veterinary Record 148, 138-141

7. Dowdall S.M.J. et al (2002) Veterinary Parasitology 106, 225‑242

8. Steinbach T. et al (2006) Veterinary Parasitology 139, 115‑131

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