Horses infected with the horse tapeworm (Anoplocephala perfoliata) cannot always be identified by performing faecal examinations. Unlike roundworms, tapeworms don’t release eggs regularly. Not only does this make it difficult to identify infected horses; it causes problems monitoring the response to treatment.
A serological test for antibodies to tapeworm antigen gives a good indication of level of infection, but the test is not available in all countries.
It may be possible to increase the sensitivity of faecal examination by treating the horse with a custodial drug, such as praziquantel, and performing the examination 24 - 48 hours later. Once killed, the tapeworms may disintegrate, releasing the eggs into the faeces.
Research carried out by Johanne Elsener of Wyeth Animal Health and Alain Villeneuve of the Faculté de Médecine Vétérinaire, Université de Montréal looked at whether treating for tapeworms one day before carrying out a faecal examination improved the chance of identifying infected animals
The study involved horses of differing ages on a single stud farm - from weanlings to adult breeding mares and stallions.
All horses were presumed to be naturally infected with Anoplocephala perfoliata -as tapeworm-infected animals had been identified previously on the farm.
The horses were weighed and dosed according to weight.
The researchers examined faecal samples before and 24-48 hours after treatment with a paste containing praziquantel (and moxidectin). Faecal samples were examined using a modified Wisconsin sugar centrifugation technique - performed by a technician who was unaware of the treatment given to each .horse.
Overall, the researchers found that they were twice as likely to detect tapeworm eggs in the faeces of horses 24 - 48 hours after treatment with praziquantel than they were before treatment.
In adult horses (mares and stallions) the difference was statistically significant. Young horses (weanlings, yearlings and two year olds) showed a numerical increase in positive horses after treatment, but the difference was not statistically significant.
The two-year old horse group had the highest proportion of positive faeces, (66% horses were positive before treatment)
The researchers conclude that sampling after treatment may give a better idea of the true prevalence of tapeworm infection.
For more details see:Examination of faecal samples after cestocidal treatment in infected horses. J Elsener and A Villeneuve
Canadian Veterinary Journal 52, 158 - 161
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