Tapeworm are a parasitic worm which live within the horse's digestive system, management routines are key to tackle tapeworm infestations in horses. Tapeworm have flattened bodies and are made up of segments (proglottids) which are full of eggs to be fertilised during reproduction, wherein each segment is capable of reproducing by themselves by having both male and female reproductive organs. Tapeworms have suckers which attach them to the gut wall inside the horse’s intestines, where they then feast on food passing by, meaning that your horse cannot absorb nutrients from their food, thus making them lose weight and can lead to them being lethargic.

There are three species of tapeworms that can infect horses. These are called: Anoplocephala perfoliata, Anoplocephala magna and Anoplocephaloides mamillana (previously known as Paranoplocephala mamilliana), with Anoplocephala perfoliate being the most commonly found in the UK. A. magna and A. mamillana are generally found in the horse’s small intestine, whereas A. perfoliata are usually found between the small intestine and large intestine, usually where the caecum is connected to be more specific. Colonisation by A. perfoliata can result in physical damage to the tissue lining the gut wall and a large infestation can result in clinical disease, such as colic, which can be fatal if left untreated.

How do tapeworm infections begin?

The life cycle of any tapeworm, including A. perfoliate, requires an intermediate host, which usually consists of a flea or an oribatid mite. Infected horses pass tapeworm segments which are full of eggs onto the pasture where they are consumed by free-living intermediate hosts. The eggs develop into larvae within the hosts’ digestive tract, where they then live until the mite is ingested by a horse while they are grazing. The host is killed within the horse’s digestive tract by the stomach acid, allowing the tapeworm larvae to be released into the horse’s intestine. The larvae complete their life cycle by attaching to the lining of the intestines, to develop into adult tapeworms, capable of releasing their own egg-filled segments.

The body of an adult tapeworm is composed of a chain of increasingly mature segments. New segments are constantly being produced behind the tapeworm’s head and they develop progressively as they are pushed towards the rear. Mature segments are full of fertilised eggs (known as gravid) and are ready to detach from the body of the tapeworm, where they then pass within the faeces into the horse’s environment, such as the stable or pasture, whereupon they can be eaten by oribatid mites, and the cycle begins again.

   This therefore means that even if your horse has never suffered from tapeworm in the past, or you believe that they may not be affected, continual testing and treatment is still necessary as mites can pass from pasture to pasture and from horse to horse. Whenever your horse moves to a different yard, a new horse arrives on your yard, or you go away to competition or day out, always bare in the mind the possibility that your horse may have encountered a tapeworm-infested oribatid mite or another horse who may pass tapeworm segments within their droppings.

Tapeworm lifecycle

How often should I test for a tapeworm infestation?

To help tackle tapeworm, you should carry out tapeworm testing twice a year, ideally in the Spring and Autumn months. These are considered the most optimal times to test and treat for tapeworm as this is when they are most active and reproduce the most often.

Ensure that you leave 4-6 months between your last test/treatment and your next tapeworm test. This is due to tapeworm-specific antibodies taking up to 6 months to dissipate within a sample for horses who have never been tested or rarely suffered from tapeworm. This mean that if you carry out a regular worming treatment and then test almost straight away, the results may come back that your horse is still infected with tapeworm, even though this may not be the case.

If your horse has had a previous borderline or moderate/high diagnosis, you can retest 2-3 months after worming treatment for tapeworm. It has been shown that, in most cases, tapeworm-specific antibodies reduce within a few weeks following treatment. Austin Davis Biologics have conducted a study regarding this, which can be found below:

When to test and treat

"Austin Davis Biologics (who produce EquiSal Saliva Tapeworm Tests) carried out a pilot trial in which EquiSal Tapeworm testing was carried out on horses (with access to grazing) every two weeks following deworming treatment for tapeworm. Data collected from this trial showed that, in most horses kept in well-managed paddocks, reduction in tapeworm-specific antibodies was seen within two to three weeks following treatment. 73% of horses had Saliva Scores which dropped to low within five weeks of treating for tapeworm. The remaining horses took a further six weeks to drop to low. This suggests that antibodies present in saliva have less memory of tapeworm infection than antibodies in blood, however, it is still recommended to leave the ideal 4-6 months before testing. This is especially true for horse’s who regularly leave the yard, are grazed with a variety of different horses year-round, and those who are kept on poorly managed land.
   It is important to understand that horses can still become reinfected by tapeworm larvae after any worming treatment. Tapeworm reinfection has been seen in horses kept in poorly managed paddocks where reinfection can happen very easily. Nonetheless, given the necessity for an intermediate host in the tapeworm’s life cycle, even well managed paddocks containing horses with high tapeworm burdens could harbour infected oribatid mites within the environment. This means that there is still a reinfection risk after worming for horses grazing in these circumstances." - EquiSal

What can I use to test my horse for a tapeworm burden?

Testing for tapeworm is becoming increasingly important to reduce the risk of anthelmintic resistance within horses. This is where worms become resistant to the active ingredients used to treat them and so they are then less effective, which makes future treatments more difficult as the current licenced active ingredients will become less effective overtime. It is important to remember there are not yet any new treatments to tackle tapeworm burdens, this means that it is vital that resistance is kept as low as possible by only treating when absolutely necessary.

The EquiSal Saliva Tapeworm Test is a highly effective way of testing your horse for tapeworm prior to administering a wormer. When you purchase your kit, you will receive a swab that is immersed in preservative with a testing tube, a barcode sticker to identify your horse’s sample, and a pre-paid returns envelope.

Allow your horse to stand without eating or being exercised for at least 30 minutes before conducting the test, and then remove the swab from the tube, remember to keep the tube safe so you do not spill any of the preservative whilst you collect the saliva sample. Place this swab in the corner of the horse’s mouth and hold it there for 30 seconds for the swab to collect enough saliva for an accurate test and result to be given.

Place this back inside the tube filled with preservative and seal the tube as best as you can. Place this inside your provided return envelope and send your sample off! Ensure that the sample is collected on the same day that you send this off and try to do this at the beginning of the week, if possible, to ensure that the sample remains viable.

Your results will then be reported, and you will be told if your horse requires treatment to tackle tapeworm or not, and which course of action is best to take.

What should you do if your horse needs treating for tapeworm?

If your horse requires treatment to tackle tapeworm infestation, either after a borderline or moderate/high diagnosis, or at the appropriate time of year, it is best to use a wormer containing Praziquantel or a double dose of Pyrantel Embonate.

Always weigh your horse as accurately as you can and ensure that the appropriate amount of wormer is administered to your horse. It is always best to slightly over-treat your horse to ensure that all worm burdens are treated appropriately, as underdosing contributes to an increase in resistance by not fully eradicating the worm burden present. As an example, if your horse weighs 430kg, treat up to 450kg. NEVER give your horse excessive amounts of worming treatments. As an example, if your horse weighs 430kg, do not give more than 500kg worth of treatment. Doing this will increase the risk of anthelmintic resistance to the wormer’s active ingredients, which eventually will reduce the effectiveness of your worming treatments, making any worm burdens more difficult to treat in the future.

Worm when necessary

In summary, it is important to manage and control tapeworm burdens. Management routines are important for helping to prevent the spread of infection, however, due to the nature of tapeworm using mites as a host for their larvae, it is always possible for infection to occur, even with the best management practices in place. To ensure your horse does not have a burden it is vital to carry out regular testing to ensure that deworming strategies are effective, with minimal contribution to the increase in resistance to the wormers we have available. Current data from EquiSal testing suggests that regular testing has an important part to play in monitoring effective worm control.

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