Abstract: Background: Biliary protozoal infections are rare in dogs. Sarcocystidae protozoal infections (i.e Toxoplasma, Neospora, Hammondia spp., etc.) are uncommon and host-specific. Diagnosis is traditionally dependent on tissue or serologic evaluation; sensitivity and specificity for these techniques can be variable. PCR amplification and genetic sequencing provide a technique to expedite diagnosis and speciation in clinical biliary protozoal infections.
Objectives: To characterize a series of canine protozoal cholecystitis cases.
Animals: Two dogs with biliary protozoal infections consistent with Hammondia spp.
Methods: Limited case series of two dogs presenting with mixed hepatopathies and hyperbilirubinemia. Biliary tachyzoites were identified via cholecystocentesis cytology during diagnostic investigations. Bile aerobic and anaerobic culture, Sarcocystidae serology, and protozoal gene PCR amplification were completed.
Results: Crescent-shaped protozoal organisms (4-5μm x 0.5μm) consistent with tachyzoites were identified on bile cytology in both dogs. Bile aerobic and anaerobic cultures would have no growth. Sera were positive for anti-Toxoplasma sp. (n=1/2) and anti-Neospora sp. (n=2/2) antibodies. Genomic isolation from bile followed by pan-Sarcocystidae (18S rRNA) PCR amplification were consistent with Hammondia spp. Subsequent cytochrome b gene-specific amplification (384 bp fragment) and sequencing in one of the samples revealed 99.7% similarity to Hammondia triffittae versus 98.9% to Hammondia heydorni. Treatment with clindamycin and fluoroquinolone resolved clinical and clinicopathologic signs.
Conclusions and clinical importance: Molecular techniques are key adjunctive techniques for protozoal identification in rarer infections. This appears to be the first report of biliary infection with Hammondia triffittae, a protozoan with a definitive fox host and not dogs.
