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Thursday, 24 November 2011

Autumn and winter worming

This article has been very kindly supplied by Ben Gaskell, Pfizer’s veterinary advisor

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. Ben Gaskell, Pfizer’s veterinary advisor explains how these parasites can be tackled to best effect.

The truth about tapeworm
Tapeworms are very common in UK horses1,2, but their definitive life cycle is still not completely understood. What we do know is that tapeworm infection can be linked to potentially serious colic3. 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 pasture4, 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
5.             Proudman and Matthews, In Practice (2000) 22, 90-97
6.             Bairden K. et al (2001) Veterinary Record 148, 138-141
7.             Dowdall S.M.J. et al (2002) Veterinary Parasitology 106, 225242
8.             Steinbach T. et al (2006) Veterinary Parasitology 139, 115131

EQUEST and EQUEST PRAMOX are registered trademarks of Pfizer Ltd. EQUITAPE is a registered trademark of Bayer Ltd. EQUEST contains moxidectin and EQUEST PRAMOX contains moxidectin and praziquantel. EQUITAPE contains praziquantel. Advice on the use of these or alternative treatments must be sought from the medicine prescriber POM-VPS. Further information from Pfizer Animal Health, Pfizer Ltd, Walton Oaks, Dorking Road, Walton-on-the-Hill, Tadworth, Surrey  KT20 7NS
Use medicines responsibly:

Friday, 4 November 2011

Equine wormers and their distinct chemical groups
Horse wormers from wormers-direct

Fenbendazole & Mebendazole based products are used less and less nowadays in routine worming as there is confirmed resistance to them. In some cases they still have a role to play when used as part of a rotational system but so it is best to take expert advice before relying on products within that group to control worm burden. Ascertain that your horse is infected with worms that are susceptible to it by taking a dung sample and having an egg count done.. By using a 5-day course  of a fenbendazole-based wormer  between October and March small redworm encysted larvae acquired during the grazing season will be removed. If an early dosage is administered this treatment can be repeated again in February to remove larvae acquired during the winter months. This will also help reduce the levels of infective larvae on the pasture the following spring.
A Moxidectin based wormer has an ability to kill encysted developing cyathostome larvae (small redworm) in a single standard dose. Studies have indicated that the ingredient Moxidectin, suppresses egg reappearance and therefore leads to a long dosing interval for small redworm control. Moxidectin based Wormers are  also effective against large redworm, pinworms, stomach worms, Intestinal threadworms, Ascarids ( adult and larval stages) and will also treat for bots.
Worms are an ever-present threat even during winter months. Worms can survive frost and snow so even a short time on pasture during winter months can be enough for horses to pick up a new infection. Used routinely throughout the winter months, lvermectin based wormers will reduce the risk of infestation. The interval between treatments can be up to 10 weeks and in a single dose it will give effectiveness against both larval and adult stages of the important parasites of horses, including small redworms. lvermectin based Wormers control parasites that are resistant to benzimidazole-based wormers. Ivermectin based wormers control Pinworms, Intestinal Threadworms, Large-mouthed stomach worms, Lungworms, Neck threadworms and Ascarids.
lvermectin based Wormers will also control bots when given as a single dose.
Products based on Pyrantel are effective against most adult roundworms so have a role to play in rotational worming. They need to be administered at twice the standard dose when being used for the treatment of tapeworm. If your horse is stabled on straw or other products where mites can survive then this double dose twice a year will ensure adequate control of tapeworm infestations. The Tapeworm lifecycle is 6 months so although treatment once a year (late September/early October) may well be adequate in some cases it is recommended that you do treat twice per year to break the cycle.
A new study has shown that 69% of horses have a tapeworm burden and horse with tapeworm are up to 8 times more likely to suffer from colic. The timing of the tapeworm control doses is based on the life cycle of the worms.
Products using praziquantel can be a very effective treatment for all three known species of equine tapeworm in a single dose, again being most effective twice a year. Products that contain ivermectin as well as praziquantel  can be used all year as they are also an effective treatment against bots and round worms. Products that contain only praziquantel as the active ingredient give owners the option of treating for tape worm without also treating for roundworm thus helping to reduce the risk of equine anthelmintic resistance building up. This should still be as part of a annually rotated worming scheme with the other distinct chemical groups but care should be taken with regard to encysted small redworm larvae where a treatment using a 5-day course of a fenbendazole-based product or a Moxidectin based product should be considered.

Simon E-SQP