Small Redworm Treatment
The fast lifecycle of the small redworm (cyathastomins spp.) has given it the most opportunity to develop evasions to our horse wormers; we no longer have a licenced chemical that isn’t showing some degree of resistance to this parasite - a very worrying position to be in.
Ivermectin and moxidectin are the most effective wormers against this parasite. At most times of year and in most cases, ivermectin is the preferred choice for targeting adult redworm burdens. Where reduction tests had proved efficacy, pyrantel can be a useful treatment, especially in young horses who may also be prone to ascarids.
Wherever possible we want to preserve moxidectin for targeting encysted stages of small redworm as it is our most effective treatment against the dangerous larval stages that can mass emerge in spring with sometimes-fatal consequences. (This is the treatment most often given in the late autumn/winter but can be given at other times of year if the winter dose was missed or there is an indication a second treatment would be useful.) Using moxidectin at other times of year when we only want to treat adult redworm is akin to using a sledgehammer to crack a nut!
A five day course of fenbendazole is our other choice of wormer for targeting encysted redworm – a very useful wormer for young horses and those that don’t have enough body fat to safely absorb moxidectin which is stored in body fat. However it has been around such a long time that resistance is recorded at over 80% in some areas so we would always advise a reduction test if using this to target redworm.
> more on winter worming
LARGE REDWORM Treatment
Worm egg counts don't differentiate between small and large redworm. Up until now this hasn't been a problem as the large redworm was largely eradicated in the UK. However recent studies and confirmed clinical cases have shown that this parasite is making a comeback. Westgate Labs now offer a large strongyle larval culturing service to monitor for this in horses. This is to enable targeted treatment without having to resort to belt and braces treatments that drive resistance.
If large strongyle are identified then the species of large redworm, combined with other factors such as age and health of horse, time of year and other test results will guide treatment choice. Ivermectin, moxidectin and fenbendazole chemicals are all licensed, but not all of them cover all species or all developmental stages. Please contact us for more information or speak to your prescriber.
Ascarid Treatment
Conversely ivermectin and moxidectin are the wormers that ascarids have developed most resistance to. We would choose fenbendazole and pyrantel as the most effective treatments for these parasites. This is the reason we would always ensure these chemicals are included in a programme for young horses under the age of four.
Tapeworm Treatment
Two active ingredients are used to treat tapeworm in horses:
- Praziquantel
- Pyrantel (administered as a double dose)
If treatment is required for tapeworm alone, a praziquantel-only wormer is the preferred option, as it targets tapeworm specifically without exposing other parasites to unnecessary chemicals.
Although availability has reduced since the withdrawal of Equitape in 2018, praziquantel-only products can still be obtained via your vet as a BOVA special order. While prescription requirements may reduce convenience, this approach ensures the most suitable treatment is used and supports sustainable parasite control for the future.
> more on praziquantel through your vet
A double dose of pyrantel may be used as an alternative, particularly where:
- Ascarids are also present, more commonly in foals or yearlings or
- The local redworm population is known to be susceptible to pyrantel.
If testing indicates that redworm treatment is also required alongside tapeworm:
- Spring/Summer/Autumn - An ivermectin + praziquantel combination wormer is recommended.
- Winter (encysted small redworm risk) - A moxidectin + praziquantel combination wormer is preferred.
Alternatively:
- Praziquantel-only treatment followed two weeks later by moxidectin, or
- A 5-day fenbendazole course, where no resistance is known.
Combination products containing praziquantel with ivermectin or moxidectin are available over the counter and are appropriate where multiple parasite types require treatment.
Pinworm Treatment
If pinworm is confirmed then one of the more old fashioned wormers such as pyrantel (Strongid P, Embotape, Pyratape P) or a 5 day course of fenbendazole (Panacur 5 day guard) is a good choice of treatment. Couple this with good stable hygiene to prevent reinfection using a good veterinary disinfectant such to clean down surfaces where the horse may rub.
Lungworm Treatment
Ivermectin and moxidectin are the most effective treatments for lungworm. Both can be used in horses but not all ivermectin based wormers or moxidectin are licenced for use in donkeys. If in doubt, check with your vet or SQP. The Donkey Sanctuary recommends using the Eqvalan brand over generic ivermectin wormers because of treatment results they have seen in their animals.
Liver Fluke Treatment
There are no treatments for liver fluke currently approved for use in horses. The only way to treat an infection is for medication to be prescribed off licence on cascade by a vet.
Bots Treatment
Although we discuss ‘worming’ to treat these parasites they are not technically worms like redworm or roundworm but flies. There are only specific times when treatment will be effective depending on their life stage.
FLIES: Insect repellents can be used to try and repel the bot fly but these won’t deter them entirely.
EGGS: Once eggs are laid on the coat these can be scraped off the hairs using a bot knife or blunt metal edge to try and minimise infection.
LARVAE: Ingested larvae aren’t treatable until they’re in the stomach of the horse. Veterinary guidance is to target them with a single treatment, waiting until after the first frost of the winter which will kill bot flies and ensure no more reinfection. Ivermectin and moxidectin are both effective chemicals and you could choose to combine this with your winter worming dose against encysted redworm.
PUPAE: Sensitive to frost and moisture.
