Strategies for Controlling Horse Worms on Pasture

The life cycles of all horse worms start with the larvae or eggs being ingested from the grass. They mature through several larvael stages in the host (horse) returning to the pasture as adult egg laying worms in the manure. The eggs in turn hatch fresh larvae. This revolving cycle means new infestations constantly occur. It is almost impossible to completely clear pasture of all types of worm. Re-infestation can be drastically reduced by adopting the following sensible control measures.

Animal Manure

The removal of all animal manure twice weekly is an essential chore. Preferably the faeces will be completely removed from the pasture to be composted. If left in a heap in a corner, you will be composting the worms and not destroying them. Care should be taken to add layers of agricultural lime betwen the layers of horse faeces to hasten decompostion, whilst destroying worm larvae. Otherwise, you will be providing a perfect breeding ground for worm larvae, especially pesky stable flies intermediate hosts to Habronema spp. of stomach worms. Horses are infected by worm larvae that emerge from flies as they feed around the lips the cause of persistent summer sores and blisters round the muzzle.

Harrowing

Harrowing is only useful during the dry hot temperatures of mid summer. Worms can survive freezing temperatures but succumb to heat. Harrowing at any other time of year is a futile waste of time.

Past History & Companion Animals

Your pasture may have been contaminated by other animals? Consideration should be given to other grazers past and present of your pasture. Ruminants such as cattle, sheep and goats are infected by the same small stomach worm of horses - Trichorstrongylus axei. These worms cause a chronic catarrhal gastritis of the stomach, diminishing the horse's ability to digest and absorb feed. Repeated infestations can cause painful lesions leading to stomach ulceration. Horses become afraid to eat anticipating the discomfort. Foals are particularly susceptible to stomach worms.

Donkeys are host to lungworms Dictyocaulus arnfield. Up to 70% of donkeys carry lungworms often showing no clinical signs of infestation. Lungworm can over winter in pasture unaffected by low temperatures. Grazing horses ingest infective larvae that migrate to the lungs via the lymphatic system, and the pulmonary arterial blood supply. Larvae travel from the alveoli to the bronchi and bronchioles where they mature. The eggs are coughed up then swallowed and expelled in the faeces. Once a pasture has been contaminated with lungworm, they emerge every summer. Many horses who are hypersensitive to dust from hay and straw have suffered lung damage as foals. Foals are particularly susceptible to this pest with long lasting lung damage.

All companion animals should be treated for worms. New animals bring added risks of further infestations. They should be dewormed before introduction to the pasture.

Over Grazing & Pasture Contamination

A high density of horses per acre increases the worm count. Over grazing forces horses to graze on rough patches of grass that they usually leave for dunging. Inevitably, this leads to reinfestation and high worm counts.

Rotational grazing will help to control the build up of parasites. The amount of acreage per horse/pony is dependent on the amount of supplementary fed provided and whether winter grazing is provided. A pony would need 1 1/2 to 4 acres, an average adult horse 3 1/2 to 5 acres split into 3 or 4 separate paddocks. Many horses particularly those in livery stables have considerably less than 3 acres leading to fields being contaminated with high levels of parasite infestation.

Regular horse worming schedule and faecal worm counts

Regular de-worming is necessary to keep the worm population of your pasture under control. A regular schedule starts with the first flush of Spring grass. Followed by regular applications every 4 to 6 weeks throughout the summer and autumn months. This regime can be relaxed over the winter months November to late February if the horse is stabled in a clean environment, as the re-infestation rate from pasture has been reduced. If your horse is left out all year round then the worming schedule needs to be continued every 4 to 6 weeks. Contrary to belief, frost and low temperatures do not kill worms.

Moon Cycles

Traditional de-worming of farm animals followed the moon cycles. The worming being started 2 days before a full moon (the moon waxing) and finishing 2 days after a full moon (the moon waning), 5 days in total. This practice is still followed in many parts of rural Europe. We have had consistently good results using the moon cycles every 2nd month. Adult red worms for unexplained reasons are attracted by the light and pull of gravity. Red worms become active over the full moon phase. Could this possibly be explained by some programming in their genes? What rural peasants have always known, science has yet to discover!

Zilch Verm

A blend of traditional herbs added to the feed to maintain the overall health of coat and gut whilst repelling unwanted internal parasites. Added to the feed over 5 consecutive days. 1 litre is sufficient for an average sized (500kgs) horse for 2 parasite de-tox programs 4 to 6 weeks apart. One litre will cover 8 to 12 weeks for one average sized horse.

N.B. Not suitable for pregnant/lactating mares or foals under 6 months old.

Contains: Extracts of traditional vermicide & demulcent herbs. One litre self dispensing bottle

Free Faecal Worm Count Kit & Moon Calendar is included and full directions on using Zilch Verm