Winter Worming

Winter Worming For Your Horse Climate changes have meant that "winter worming" should not be overlooked. It is known that harsh frosts may kill infective larvae, and that cold conditions cause eggs on the pasture to become dormant, only hatching into infective larvae when the weather warms up. However, our winters in the UK are becoming wetter and milder. The mild ambient temperatures and rainfall now experienced in winter provide ideal conditions for larvae to survive. Peak periods for larval infestation have expanded, with the potential for larvae to be ingested by your horse late in the year, and not just during the traditional "grazing season".

As such routine roundworm control needs to be continued throughout the year, with dosing intervals based on brand's active ingredient, i.e. every 13 weeks with moxidectin (e.g. EQUEST).

Winter Worming Treatments:

• Routine Roundworm Control: Continue throughout winter, even if your horse is only at grass for short periods of time during the winter months.

Additional treatments to be added if not covered as part of routine treatment. Dependent on active ingredient used for routine roundworm control.

• Bots: Treat your horse after the first frost when the adult flies die off, and prior to the larvae maturing and emerging from your horse in the spring. Treatment is with a moxidectin (e.g. EQUEST) or ivermectin based wormer.
• Encysted Small Redworm: Treat your horse in early February against encysted small redworm, as they typically emerge en masse in late winter/early spring. This mass emergence of encysted small redworm, known as larval cyathostominosis, is potentially fatal. Treatment is with a single dose of moxidectin (e.g. EQUEST) or 5-day course of fenbendazole based wormer. However, recent research1 has found that the 5-day course of fenbendazole can itself cause severe damage to the horse's gut wall and may actually mimic the very condition for which this 5-day course is meant to prevent, whereas a single dose of moxidectin was found in the same research not to cause severe damage to the horse's gut wall.

Winter Worming Tips:

• Continue to remove horse droppings from your pasture during the winter at least once a week. However, during mild and wet conditions twice weekly removal will need to be considered.
• Feed hay in mangers and nets. Feeding from the floor, even when in the stable, increases the risk of your horse ingesting worm larvae.

1. Steinbach T et al. Veterinary Parasitology (2006) 139: 115-131

Copyright: Fort Dodge  

Photograph supplied by Voices for Horses
 

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Added on: 30/10/08.

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