Deworming and vaccination


All horses get intestinal parasites, but most often they will not pose any threat to their health, unless they occur in great amounts. Foals and young horses get parasites to a greater extent, while older horses have often built up an immunity against them. To find out whether your horse is heavily contaminated, you need to send a dung sample from the horse to a laboratory such as Vidilab's kollamasken.

The optimal time to send samples is in April-May. This allows you time for any necessary deworming before the summer pasture, thus avoiding further contamination. If your horse is infested with several parasites, you may also take a follow-up sample around 14 days after the deworming. Another good time to take a sample is in September-October, before the horse returns to the stable.

All deworming drug treatments for horses require a prescription. This is due to the fact that many parasites have become, or risks becoming, resistant to the existing drugs. If your horse turns out to have parasites, you should contact your veterinarian for advice and a prescription for a suitable drug treatment.

These are few of the most common parasites:

Large and small redworm

Live in the large intestine of the horse. In greater amounts, they may cause colic, diarrhoea and weight-loss Deworming is most effective in spring.

Large roundworm

Lives in the small intestine, and most often only occurs in foals. Poor growth, decreased appetite and colic may be symptoms of infection. Foals should be treated for large roundworm at 8 and 16 weeks.


Lives in the junction between the small and large intestines. Colic and constipation of the cecum may occur in the event larger amounts of the parasite. Deworming is most effective in spring.


The botflies lay their eggs primarily on the front legs of the horse in the summer. When the horse uses its mouth to scratch its legs, it gets larvae in its mouth, which later travel to the stomach where they stay over the winter. Large amounts can cause colic and inflammation. Deworming is most effective in the autumn, but the best thing is to remove all the eggs from the horse's legs before it eats them.

Some common vaccinations

Equine influenza (horse flu)

Equine influenza is divided into two subtypes; A1 and A2 These occur throughout the year and they are highly contagious. The symptoms include a high fever, coughing and nasal discharge. You should vaccinate your horse against influenza. If you want to compete, you must have a valid vaccination to participate in any competition. Keep track of how often your horse needs its shots, and check the competition rules to make sure you live up to them. If you are unsure, contact your veterinarian.


Tetanus is caused by a bacteria found, for example, in dirt. Infected wounds most often arise as the result of a puncture wound in the hoof or in another place. The poison that builds up affects the nervous system, making the horse stiff and giving it trouble swallowing. The mortality rate is high, and vaccination is therefore to be recommended.


If you feed your horse haylage or ensilage, you may want to vaccinate it against botulism, however, check with your veterinarian first. Clostridium botulinum is bacteria that produces a neurotoxin; botulinum toxin, which is lethal to horses. The bacteria may form in the feed if dirt or dead animals have been wrapped in with the hay bale. This places high demands on both harvesting and storage to achieve good results.


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