A comparison of the SNAP® Giardia fecal antigen test and the zinc sulfate double centrifugation fecal flotation procedure to diagnose Giardia intestinalis infections in two populations of infected dogs

Abstract

Giardiasis is a common intestinal protozal parasitic infection of the pet dog and cat population. Veterinarians often have difficulty correctly diagnosing this parasite. Studies were conducted to compare the zinc sulfate double centrifuge fecal flotation to the SNAP (registered trademark) Giardia fecal ELISA test manufactured by IDEXX laboratories Inc. in purpose bred beagles and shelter and commercial kennel dogs. In these evaluations the zinc sulfate double centrifuge fecal flotation and fecal ELISA test performed similarly. Both tests performed better in the shelter and commercial kennel dog population than the chronically infected purpose bred beagles. There was an increase in number of positive animals identified when 3 consecutive daily samples were evaluated as compared to any one individual day for either test method. Post treatment evaluation of the diagnostic tests was performed in 23 laboratory beagles. Each beagle was treated for 3 consecutive days with Drontal plus and then bathed on the last day of treatment and fecal samples were collected from the treated dogs every other day starting one day post treatment for 21 days. It was found that all beagles were negative on zinc sulfate double centrifugation fecal flotation, fecal ELISA and IFA within 24 hours of treatment and nineteen (82.6%) of the beagles did not re-shed cysts during the 21 day post-treatment evaluation period. Four beagles returned to shedding cysts (Flotation or IFA positive) between days 17 and 21. These findings suggest that a positive test within a week of treatment is likely the result of inappropriate treatment. After the prepatent period, positive results may occur due to a return to shedding, reinfection or inappropriate treatment. Chronically infected laboratory beagles may not be a good model for acute Giardia infections as these dogs are rarely clinically ill and detection is more difficult.