There are three main types of winter worms that affect horses at this time of year and so they need to be tested for (and treated if necessary). These are encysted small redworm, tapeworm, and bots. The most important worm to consider is encysted redworm, the larval stages of which have the ability to hibernate in the horse over winter and which are a particularly dangerous threat to health, states Claire Shand from Westgate Labs.Many thousands can burrow into the gut wall and lay dormant before staging a mass emergence in springtime. This can trigger colic that is very difficult to treat.To guard against this, we need to test or treat for worms proactively.Carry out a saliva test for tapeworm if this hasnt been done in the previous six months, and consider bots if any of the small yellowish eggs of this fly have been seen on the horses coat over the summer months, adds Claire.Results from all of these tests will help to decide which, if any, treatment is needed and target this to help slow resistance. Do a faecal worm egg count again eight to 12 weeks on.Tapeworm (Cestodes)Tapeworms are grey, flat, segmented worms that can grow up to 8cm long and 1.5cm wide. They form clusters at the junction between the small and large intestines where the mature worm releases segments full of eggs. These are then passed in the horses droppings onto the pasture. Here, they are eaten by the forage mite, the eggs hatch and the larvae develop inside the mite. The horse then eats the mite while grazing and the larvae develops into a mature adult over the next six to ten weeks. This is why regular poo-picking is an essential part of your worming regime.Once inside the horse, tapeworm can cause digestive issues, loss of condition, spasmodic colic and fatal blockages.Testing and treatmentTapeworms wont show up in a faecal worm egg count, but there is a blood test available and a saliva test that owners can do themselves, explains vet Sue Taylor MRCVS.This should be done once in the spring and once in the autumn to detect whether your horse has a tapeworm burden and requires treatment.Tapeworm burdens are likely to be highest in autumn, at the end of the grazing season, so testing and worming only if necessary should take place then.Encysted small redworm (Cyathostomes)Encysted small redworm is one of the most common and damaging parasites found in horses. The larvae hibernate in the gut wall during the winter and emerge en masse as adults in the early spring, causing severe damage to the horses intestines. Encysted small redworm pose a potentially fatal health risk. Untreated, encysted small redworm may develop into adults. They can cause weight loss, diarrhoea and colic in horses with a mortality rate of up to 50%.Testing and treatmentThe presence of encysted small redworm will not show up in a faecal worm egg count because the larvae do not lay eggs.It is for this reason that all horses should be treated for encysted small redworm during late autumn and winter, recommends Sue.For horses that have had regular worm egg counts under 200epg through the previous year, a small redworm blood test can be carried out by a vet to decide if treatment is required.Earlier this year, a new test was made available that will identify large and small redworm under a microscope by Westgate Labs. Find out more here.If treatment is required, a proactive moxidectin treatment is recommended. This is because, out of the two chemicals licensed against larval small redworm, it is the one with least documented resistance, the alternative being fenbendazole as a five-day course, says Claire Shand. We aim to reserve moxidectin for this use in order to preserve its efficacy as a key medicine against encysted redworm. If you know you are going to treat then carrying out a redworm reduction test this is a worm egg count before treatment and another egg count 10 to 14 days afterwards is advised to measure whether there is any resistance to the chemical used within the worms on your pasture.Bots (Gastrophilus)Bot flies lay sticky yellow eggs on the horses coat, particularly the legs, shoulders and face in the summer, which are then ingested when the horse grooms themselves. The larvae then hatch and penetrate the mucosa of the tongue and mouth and then migrate towards the pharynx and then the stomach. Here, they attach to the stomach lining. After nine months, the large red or yellow larvae are passed in the droppings the following spring and summer. After six weeks, the adult fly emerges.If left untreated, bots can cause inflammation in the mouth and throat, and ulceration and damage in the stomach.Testing and treatmentEvery effort should be made to remove bot fly eggs from the horse in the summer before the horse ingests them, advises Sue. Theres a specific tool that makes this possible as they are tricky to remove by hand alone.There is no test for bots because they pass as larvae in the droppings and not as eggs. Administer a wormer after the first frost when the adult flies have died and before the bots mature.Main image ShutterstockRelated contentNew test available for potentially fatal redworm (and you dont need to buy it from a vet)Resistance to horse wormers: action every owner must take now or horses will dieFaecal worm egg counts for horses explainedUsing the wrong wormer could be fatal, warns vetEssential horse worming schedule from a vetThe post Winter worms: three to test your horse for now appeared first on Your Horse.