Winter Worming

11th October 2019

Winter Worming

Typical Parasites December to February

  • Strongyles (Small & Large Redworm)
  • Encysted Larvae Redworm
  • Roundworms
  • Bots
  • Pinworms

Although responsible horse owners aim to minimise their wormer use to combat resistance, reliable testing is not yet fully established to check for the Encysted Stage of Redworm.

Recommendations are to treat proactively with one of two drugs licensed for the treatment of encysted stage of redworm; Moxidectin or 5 Day Fenbendazole wormer between December and February, preferably after a number of hard frosts.

Moxidectin – Equest & Equest Pramox

5 day Fenbendazole – Panacur Equine Guard

Moxidectin is the preferred treatment in most cases, particularly if you are also looking to target bots at the same time, because of widespread resistance to fenbendazole.

Moxidectin particularly has been popularly prescribed at various times of year historically as it is a broad spectrum wormer and consequently has increased danger of building resistance of parasites. Instead, the best practice is to build one of these drugs (Moxidectin or 5-day Fenbendazole) into your worming program once in the year (twice in exceptional cases)

Warnings: Moxidectin shouldn't be given to underweight horses, foals under 4 months old (6.5 months if also combined with praziquantel) and isn't licenced for donkeys. We also advise caution if using it in miniature Shetlands unless you can calculate dosage accurately. This is because the active ingredient is stored in body fat and these animals don't have sufficient stores to take up the drug.

There are circumstances where a 5-day course of fenbendazole is more appropriate such as where moxidectin is contra-indicated and for young horses under four who are also susceptible to roundworm infection.


It is a good idea to supplement your horse with a Probiotic supplement such as Synbiovit or Diazorb by TRM, at the time of worming to promote healthy gut bacteria. The helpful bacteria, gut motility can become imbalanced and the gut can become inflamed throughout the worming treatment.

Small Redworm

large redworm