Cryptosporidium spp. Are Associated with Giardia duodenalis Co-Infection in Wild and Domestic Canids

Cryptosporidium spp. and Giardia duodenalis are zoonotic food- and water-borne protozoa of
veterinary importance. They are one of the main causes of diarrhea in domestic dogs (Canis familiaris).
Wild canids, such as red foxes (Vulpes vulpes) and raccoon dogs (Nyctereutes procyonoides), can act as
natural reservoirs for these parasites. The aim of this study was to estimate the prevalence of these
pathogens and analyze possible factors that may affect the infection in wild and domestic canids. A
total of 373 domestic dog, 219 red fox, and 78 raccoon dog fecal samples were collected and tested
for Cryptosporidium spp. and G. duodenalis presence with direct immunofluorescent staining. The
dog owners filled a questionnaire on the dog’s habits and lifestyle to identify and analyze potential
factors that may affect the occurrence of these parasites in dogs. Cryptosporidium spp. were found
in 16.3%, 28.3%, and 28.2% and G. duodenalis in 0.7%, 27.4%, and 30.8% of the examined dogs, red
foxes, and raccoon dogs, respectively. The highest prevalence was observed in puppies—15.4% and
18.5% for Cryptosporidium spp. and G. duodenalis, respectively. In all three canid species, infection
with Cryptosporidium increases the risk of co-infection with Giardia and vice versa.