Biological characterization of Tritrichomonas foetus of bovine and feline origin

Abstract

Tritrichomonas foetus is a causative agent of venereal trichomoniasis in cattle characterized by early fetal death and post-coital pyometra. Reports have suggested that T. foetus (or a similar organism) is also the causative agent of large-bowel diarrhea in cats, characterized by large bowel inflammation, flatulence, tenesmus and fecal incontinence. Diagnosis of feline trichomoniasis is based upon observation of live organisms in direct smears, cultured feces or by amplification of specific genes using polymerase chain reaction (PCR). No documented treatment successfully eliminates T. foetus consistently from naturally infected cats. Certain drugs may reduce clinical signs and numbers of trichomonads from feces, but relapses of diarrhea commonly occur. In the first study I attempted to estimate the prevalence of feline trichomoniasis within the pet population in the United States. To do so, 173 fecal samples were collected from cats in 16 states. Feces were scored for consistency and subjected to culture and PCR analysis. Seventeen of 173 (10%) were positive for T. foetus by both fecal culture and PCR. Results indicate that T. foetus is prevalent in the pet population and that its presence correlates with the presence of diarrhea. Experimental infections were conducted to determine if T. foetus, whether of bovine or feline origin, are biologically distinct. In the second study, two groups of virgin Angus heifers were inoculated with either T. foetus isolated from a pyometritic cow or a naturally infected cat. Vaginal, cervical, and uterine mucus samples were analyzed over an 11-week period and a single transcervical uterine biopsy sample was obtained from each animal, revealing severe damage to the endometrium in heifers infected with the bovine isolate of T. foetus. This was not observed in heifers infected with the feline isolate. In the third study, 6 cats were inoculated with a bovine (D-1) isolate of T. foetus and one cat was inoculated with a feline (AUTf-1) isolate of T. foetus. Fecal samples from each cat were collected and subjected to culture over a period of five weeks. By PI day 15 the cat infected with the feline (AUTf-1) isolate had become culture positive for trichomonads while only one of six cats infected with the bovine (D-1) isolate was positive by PI day 32. At necropsy, the intestine of each cat was divided into five sections and the contents were collected and subjected to culture. The cat that received the feline (AUTf-1) isolate was positive in 4 of 5 intestinal sections and two cats infected with the bovine (D-1) isolate were positive in only one intestinal section. The combined results of studies two and three indicate that the disease caused by feline and bovine isolates of T. foetus in cattle are not identical and the susceptibility of cats to the feline (AUTf-1) and bovine (D-1) isolates T. foetus also appears demonstrably different.