Case study: Coinfection with Tritrichomonas foetus and Giardia duodenalis in Two Cats with Chronic Diarrhea
Robert Lo, Ph.D, D.V.M
A mixed infection of Tritrichomonas foetus and Giardia duodenalis was confirmed in two 6-year-old Maine Coon cats. One of the cats had a history of chronic liquid diarrhea and several treatment failures. Both cats observed G. duodenalis and trichomonas from the fecal smears, and the infection of T. foetus was also confirmed by RT-PCR. The cat recovered completely after taking ronidazole treatment. In refrigerated stool specimens collected from cats with chronic diarrhea, drop-shaped trichomonad pseudocysts, which are smaller than the cysts of G. duodenalis, were detected. When the pseudocysts are stained with Lugol’s solution or Giemsa, they appear brown or light blue, respectively, and their morphological characteristics are similar to those of bovine T. foetus in vitro. It is worth noting that the pseudocysts in feline trichomonads may be a way for the protozoa to fight against unfavorable environments. Clinicians detected pseudocysts in refrigerated stool, which may be a useful clues to the diagnosis of this disease.
Fecal smears of a 6-month-old female Maine Coon cat with chronic liquid diarrhea, stained with Lugol’s solution (a–c) and Giemsa stain (d–f); showed (a) and (d) Giardia duodenalis trophozoites ; (B) and (e) a Giardia duodenalis cyst; (c) and (f) drop-shaped trichomonads (630x).
Fecal smears from a 6-month-old female Maine Coon cat with chronic liquid diarrhea stained with Lugol’s solution (a–c) and Giemsa stain (d–f); (a) and (d) showed Giardia duodenalis trophozoite; (b) and (e) showed a Giardia duodenalis cyst; (c) and (f) showed drop-shaped trichomonads (630x).
Trichomonads in fecal smear from the cat with diarrhea. Arrow heads in (a) indicate anterior flagella emerging from the trophozoite, while arrow heads in (b) indicate undulating membrane (1000x).
Typical morphology of trichomonads observed in saline solution-diluted fresh fecal smear from the cat with diarrhea. Arrow heads in (a) and in (b) indicate anterior flagella and undulating membrane, respectively (630x).
Drop-shaped unidentified elements in fecal smears stained with Lugol’s solution (a) and Giemsa stain (b-c). Arrow heads in (a) indicate an internal oval structure (400x). Arrow heads in (b) indicate a curved linear structure (1000x). Arrow heads in (c) indicate an undulated portion of the surface (1000x).