Case 7: Cystoisospora Infection In A Puppy

A three-month-old female Pomeranian puppy was presented for veterinary examination and evaluation of bloody diarrhoea. The puppy had been recently purchased from a pet shop. Treatment with antibiotics improved the diarrhoea but it returned once the treatment finished. Two weeks later the puppy was not gaining weight despite a reasonable appetite. Examination of a faecal sample at CityU VDL found Cystoisospora oocysts (previously called Isospora) confirming a diagnosis of canine coccidiosis. Therapy then commenced with metronidazole and trimethoprim sulfa. The diarrhoea resolved on this treatment and the dog returned to full health.

Dogs can become infected with Cystoisospora canis, C ohioensis and C burrowsi. The large size and shape of the Cystoisospora oocysts allows them to be identified to the genus but not the species level. Other protozoa infecting dogs include Hammondia heydorni, Neospora caninum, Cryptosporidium spp, and Sarcocystis spp. All these other protozoa are much smaller in size. Complete identification and clarification can be undertaken by molecular testing.

Other flagellates infecting dogs and a possible cause of diarrhoea are Giardia duodenalis and Tritrichomonas foetus. All of these pathogens can be tested for at CityU VDL by direct visualisation or molecular testing of faecal samples. Contact the laboratory for further information.

Figure 1: Cystoisospora oocysts in a faecal flotation from the infected puppy showing one and two sporocysts with the oocysts.