Diagnosis of feline whipworm infection using a coproantigen ELISA and the prevalence in feral cats in southern Florida

Trichuris felis, the whipworm of cats, is a relatively rare parasite, although more common in tropical and sub-tropical regions such as the Caribbean and South America. In southern Florida, T. felis is known to occur, but estimating prevalence can be challenging using fecal egg counts due to low intensity and single sex infections. A microplate enzyme-linked immunosorbent assays (ELISAs) for parasite-specific antigen in feces could increase the ability to detect these infections. In this study, the IDEXX Fecal Dx™ antigen ELISA for whipworm (designed for detection of Trichuris vulpis) was evaluated for detection of T. felis using 35 feral cats from St. Kitts, euthanized for non-study related reasons. Twenty-nine of the cats were positive for T. felis with worm counts ranging from 1 to 66 per cat (mean 9.6) and egg counts ranging from 0 to >500 (mean 109.8). The ELISA detected 26 of 29 positive cats while flotation (centrifugation with Sheather's sugar solution) detected 24 of the 29 positive cats. To estimate prevalence in southern Florida, feces from 65 feral cats from the greater Miami area were tested using the ELISA and fecal flotation (centrifugation with zinc sulfate). Twenty-five cats (38%) were identified as positive with the ELISA compared to 17 using fecal flotation. This prevalence was surprising and further investigated by reviewing results of feline samples from Florida submitted to IDEXX Reference Laboratories between 2010 and 2017 and analyzed using fecal flotation. While prevalence was below 1%, there was an apparent trend in increasing prevalence. The results of this study confirm that the IDEXX Fecal Dx™ antigen test for whipworm ELISA, while developed for T. vulpis, can detect T. felis infections. It also suggests that prevalence might be higher than previously known in Florida and might be increasing. Further studies are required to determine the distribution of this higher prevalence and if the distribution and prevalence of T. felis are changing.