Spring heralds the time for turning our horses out onto new grass after the restrictions of winter and this is one of the most important times to think about your next steps for worming, advise the worming experts at Pfizer.
Appropriate dosing in early spring can have a positive effect on managing the worm burden throughout the summer and in turn may reduce the need for additional dosing during this period.
Small redworm (cyathostomin) is the main concern in grazing horses1 and the level of infection will increase with higher pasture burdens. All horses that are infected with worms will shed eggs onto the pasture, as a part of the parasite’s natural life cycle. However, some horses will naturally cope better with their environment and shed less worm eggs. Conversely, some horses, especially debilitated or young animals, will pass more worm eggs in their faeces, so called high shedders. These ‘high shedders’ can infect the pasture in a short space of time and consequently increase the pasture challenge to other horses that share their grazing. Clean grazing reduces overall worm burdens and reduces the need for excessive use of wormers and this should be the principle for sustainable worm control
This spring, first assess the grazing you intend to use. For example, cleaner pasture, that hasn’t been grazed for at least six months or has experienced hard winter frosts, will hopefully pose a lower infection challenge. In this case it may be sensible to turn out and then use an FWEC to monitor how the horses’ worm burdens are developing over the grazing season. Conversely, turning a horse onto pasture that has been used heavily (worm eggs can survive on pasture from the previous year) means you will need to be very conscientious about your worm control programme during the grazing season and consider whether to dose around turnout.
“In some instances it’s useful to bear in mind the two week persistency of wormers containing moxidectin, against small redworm,” explains Ben Gaskell, Pfizer’s Veterinary Advisor. “Using such a product two weeks after turnout should treat all the small strongyles ingested since turnout and for the two weeks following dosing, This could serve to reduce the initial worm burden on the pasture and in your horses, theoretically reducing the build up of worms over the grazing season and hence reducing the need for repeated worming doses over the later summer months.” Reducing reliance on wormers and using the right wormer at the right time should slow the development of resistance.
To check that your worm control methods are working it’s strongly advisable to use regular FWECs throughout the summer. It’s the best way to identify which horses may need treatment, as each horse may cope differently with the same environment. Remember that FWECs are only a snapshot in time but used regularly they will show trends and in time build a picture of the horse’s shedding patterns.
Even if you are following to best advice on good pasture management and conducting regular FWECs to identify high shedders you will of course still need to remember the more seasonal worm threats. In most instances this will necessitate strategically dosing for tapeworm in the spring and autumn and for encysted small redworm and bots during the winter.
Pfizer Animal Health’s Manage, Test, Plan, Dose campaign provides an outstanding range of information to help horse owners make the right decisions about worming. Talk to your vet or SQP retailer or find out more by visiting www.wormingyourhorse.info
1 Matthews JB (2008) An update on cyathostomins: Anthelmintic resistance and worm control. Equine Vet. Education 20 552-560