The Importance of Worming for Tapeworm

18th April 2018 

Dr Rosie Naylor BVetMed MVetMed DipACVIM MRCVS RCVS Specialist in Equine Internal Medicine, Technical Product Manager - Equine, Virbac UK

Tapeworm are recognised as a risk factor for various types of colic in horses (Proudman and Holstock 2000). The most common species, Anoplocephala perfoliata, is the main tapeworm associated with health problems. The adult tapeworm tend to cluster around the narrow junction between the small and the large intestine (the ileo-caecal junction). This can result in blockages which prevent the passage of food through the intestines resulting in an impaction, a potential cause of colic.

Horses become infected with tapeworms by eating forage mites containing the tapeworm larvae. These mites are not visible to the eye but are often present in large numbers on summer pasture, or occasionally hay and bedding. These larvae then mature to adult tapeworm within the horse and start to shed eggs within 6-10 weeks. 

 

 

Figure 1: The tapeworm life-cycle

Tapeworm eggs are passed in segments which means that they will not necessarily be detected by routine faecal egg count testing. Specific testing must therefore be carried out to check for tapeworm and to determine whether a horse needs treating. Such tests measure antibody levels, in either blood or saliva, and give information regarding previous exposure to tapeworm.

Whilst horses of all ages are at risk of tapeworm, a recent study found that younger horses required more tapeworm treatments, with 55% of horses aged 1-5 years old needing treatment (Lightbody et al 2018). The same study also found that 41% of new arrivals required treatment, highlighting the importance of testing or treating new horses when they arrive at the yard (Lightbody et al 2018). Antibody levels increase in horses greater than 16 years of age (Proudman et al 1997), suggesting an increased susceptibility of older horses.

Figure 2: Equine tapeworm

If testing is not performed, a wormer that is effective against tapeworm should be incorporated into the annual worming programme. This may be given once or twice a year depending on age, previous worm test results and other risk factors (Nielsen 2016). Traditionally tapeworm treatment has been recommended in the spring and autumn, at the start and at the end of the grazing season. Only two wormer ingredients are effective against tapeworms, pyrantel (used at twice the standard dose rate) which controls one species of tapeworm or praziquantel at the standard dose, which kills all three species of tapeworm known to affect horses. Speak to your vet or SQP for direction on tapeworm treatment.

It is important to remember that worm populations can be reduced by good pasture management. Frequent poo-picking, at least twice preferably three times per week is vital. Keeping young stock separate from older horses will prevent younger horses from contaminating the pasture of older horses and ensuring sufficient grazing per horse will also reduce pasture contamination. Rotating and regularly resting paddocks in addition to co-grazing with sheep can all help to reduce the risk of infection. 

Brought to you by Virbac, the manufacturer of Equimax® and Eraquell®. 

References

Lightbody, K.L., Matthews, J.B., Kemp-Symonds, J.G., Lambert, P.A. and Austin, C.J. (2018) Use of a saliva-based diagnostic test to identify tapeworm infection in horses in the UK. Equine Vet J.

Proudman, C.J. and Holstock, N.J. (2000) Investigation of an outbreak of tapeworm-associated colic in a training yard. Equine Vet J. 

Proudman, C.J., Holmes, M.A., Shearan, A.S., Edwards, S.E.R. and Trees, A.J. (1997) Immunoepidemiology of the equine tapeworm Anoplocephala perfoliata: age-intensity profile and age-dependency of antibody subtype responses. Parasitology.

Nielsen, M.K. (2016) Equine tapeworm infections: Disease, diagnosis and control. Equine vet. Educ.