Investigation of Factors Associated with Subclinical Infections of Giardia duodenalis and Cryptosporidium canis in Kennel-Housed Dogs (Canis lupus familiaris)

Giardia duodenalis and Cryptosporidium spp. are zoonotic protozoal pathogens, spread by a fecal-oral route, which can infect a wide range of hosts including but not limited to dogs and humans. Giardia was recently estimated to be present in 37% to 50% of kennel-housed dogs. Cryptosporidium infections in kennel-housed dogs have been reported in 7% to 21% of the population. The goal of this study was to define demographic factors and fecal scores associated with positive screening test cases of Giardia and Cryptosporidium in kennel-housed laboratory dogs in the state of Texas. Fecal samples were collected from 153 clinically normal laboratory dogs at an academic research facility and a local laboratory dog supplier. We used 3 diagnostic tests evaluated in parallel to determine test positivity to each organism: a human point-of-care coproantigen test, a direct immunofluorescent assay, and an in-house polymerase chain reaction. Dogs were significantly more likely to test positive for Giardia (45%) than Cryptosporidium (7%) (P < 0.01). Dogs that were 18 mo of age or younger had 3 times the odds (P = 0.009) of subclinical Giardia infection compared with older dogs. We found no significant relationship between age and Cryptosporidium prevalence. Dogs with hard feces (fecal score 1-2) at the time of screening had 0.34 times lower odds (P = 0.049) of testing positive for Giardia than dogs with normal feces, but no statistically significant relationship was found between fecal score and Cryptosporidium-positive test status. With these findings, we demonstrated the value of considering age and fecal score when choosing which dogs to screen for subclinical Giardia. Additional studies with larger sample sizes should be conducted to determine the relationship between age and fecal score and subclinical Cryptosporidium infection.