Environmental conditions during collection and storage of equine fecal samples impact the resulting fecal egg counts (FECs), report parasitologists from both Denmark and the United States.

"Due to the concern regarding anthelmintic resistance in horses, counting strongylid eggs in equine fecal samples pre- and post-deworming has become an important tool in screening for drug resistance and devising targeting worming strategies," said Martin K. Nielsen, DVM, from the University of Copenhagen in Denmark.

But one of the problems associated with performing FECs is that little information regarding collection and storage of fecal samples on the accuracy of egg counts is available.

 To assess pre-analytic factors on egg counts, Nielsen and colleagues rectally collected feces from horses in both Copenhagen, Denmark, and Athens, Ga., when temperatures were approximately 2.3-7.0°C and 30.6-32.4°C, respectively. Fecal samples were stored in airtight containers in the freezer and fridge, at room temperature, and in an incubator set at 38°C. They performed FECs immediately and periodically for up to 120 hours after collection.

Key findings in this study included:

• No decline in FECs was noted for samples maintained in the refrigerator, but FECs did decrease for fecal samples stored in the freezer and incubator.
• Samples maintained at room temperature did have declining egg numbers in Denmark after 24 hours, but not the United States.
• No difference in FECs over time was noted in fecal samples stored in airtight or open containers in Denmark, but FECs significantly decreased when stored in open containers in the United States, but only after 12 hours.

"Our results demonstrate that refrigeration is the best method for storage of fecal samples intended for egg count analysis, but accurate results can be derived from fecal samples collected from the ground within 12 hours of passage," Nielsen said. "The results of this study are important for parasitologists, equine veterinarians, stable managers, and horse owners alike."

The study, "Effects of fecal collection and storage factors on strongylid egg counts in horses," is available online and is scheduled to be published in an upcoming edition of Veterinary Parasitology. The abstract is available for free on PubMed.

Disclaimer: Seek the advice of a qualified veterinarian before proceeding with any diagnosis, treatment, or therapy.