Anoplocephala perfoliata, the most common horse tapeworm, was for a long time thought to be harmless. It is now known that it may be associated with colic. So it is worth monitoring and preventing heavy infestations.
The eggs are released intermittently, so examining fecal samples may give an unreliable estimate of the level of infection. Fecal samples may appear negative even though tapeworms are present in the horse’s gut.
Scientists in Japan have been looking for a more reliable way of detecting tapeworm eggs. Dr Shin-Ichiro Fukumoto and the research team at the Rakuno Gakuen University School of Veterinary Medicine, Ebetsu, Hokkaido, Japan assessed the value of post-treatment testing of fecal samples.
They used bithionol, an anti-tapeworm drug that is available in a paste formulation in Japan. The fecal tapeworm egg count was carried out using a sucrose flotation (modified Wisconsin) method.
A pilot study involved 12 horses (7 mares and 5 foals). Fecal samples were collected before, and one day after, treating with bithionol. All horses had higher egg counts one day after treatment. This included three horses that had no tapeworm eggs in the feces when tested before being treated.
A larger scale field trial found all of 17 horses positive for tapeworm eggs the day after treatment. (Only 16 horses had worm eggs in feces before being treated) The egg count had increased to 13 - 19 times the level at 7 days pre-treatment.
When is the best time to collect a sample after treatment? In the field trial the research team collected samples one, two and seven days after treatment. Tapeworm egg counts were dramatically higher on the first day after treatment. By the second day they had fallen back to near pre-treatment levels. A week after treatment, there were few if any tapeworm eggs in the feces.
The researchers conclude that fecal examination the day after bithionol administration provides a reliable way of diagnosing Anoplocephala perfoliata infection.
For more details:
Evaluation of marked rise in fecal egg output after bithionol administration to horse and its application as a diagnostic marker for equine Anoplocephala perfoliata infection.
Y Sanada, H Senba, R Mochizuki, H Arakaki, T Gotoh, S-I Fukumoto, H Nagahata
J Vet Med Sci. (2009) 71, 617 - 620