Answer: While it is unlikely a horse will become ill or suffer harmful effects from being dewormed too often, in the long term, all horses’ health can be compromised by the development of parasite resistance to dewormers.
Regular worm egg counts are necessary during the grazing season, which can be between March and September (weather dependent). Horses with single high worm egg counts, regular elevated counts or susceptible horses (very young or old) do then need treating.
Common signs of parasite or worm infection include:
After worming allow your horses to pass the parasites and then move them to clean pasture (allow 48 hours after treatment). Consider grazing your horse with other species such as sheep/cattle which can ‘mop up’ some of the worm burden.
Many of the data sheets for wormers, notably those that contain praziquantel, ivermectin or moxidectin, advise stabling for two – three days after worming. Equitape data sheet states that “in order to limit pasture excretion of the product and its metabolites, horses should remain stabled for two days after treatment”.
2. Ivermectin and moxidectin are the best choices to control strongyle parasites. Pyrantel, fenbendazole and oxibendazole are good for treating ascarids in young horses. Ivermectin resistance is common in ascarids.
“(Non moxidectin, Non fenbendazole product) has the capacity to treat all common types of parasitic worms (including tapeworms) and bots.” “(Non moxidectin, Non fenbendazole product) has the best combined efficacy and the broadest spectrum of activity of any wormer.”
Treatment for Bots
Traditionally horses are treated for bots at the end of autumn, after a frost that kills the adult fly, and again at the beginning spring to rid the stomach of all the larvae. In the past the treatment was worse than the disease, with extremely toxic chemicals given via a stomach tube to the horse.
There are two types of wormer that can be used for this, fenbendazole or moxidectin based wormers. Horses only need treating for tapeworm twice a year as the lifecycle takes six months to complete. This should be done in March and September. This can be done using a praziquantel or a pyrantel based wormer.
Occasionally you might see the parasites themselves in the droppings. Even if your horse has worms this is rare because they are usually metabolised in the gut first but it’s definitely not unheard of. If you see worms you will want to identify and treat them with the appropriate wormer.
Horses become infected by ingesting the parasite in contaminated food or water. Transmission: The parasite can be transmitted from horses to humans in contaminated water, soil, or surfaces and can survive in the environment for long periods.
Because these worms can migrate to the lungs, infected horses may show signs of respiratory disease such as cough or nasal discharge.
If you do not ACCURATELY know your horse or pony’s weight then by overdosing you will be speeding up the development of worm resistance and by under dosing you will be wasting your money on wormers as your horse or pony may still be suffering from worm infestation and damage.
An untreated tapeworm burden may cause colic. Egg counts do not detect immature, encysted worm larvae which are not producing eggs. … If the horse does not get wormed because it has a low egg count you will not remove bot larvae that live in the horse’s stomach over the winter.