Interpretation of Parasitology Results – Companion Animals
Diagnostic tests used in companion animals:
- Fecal flotation: Fecal flotation gives a broad overview of helminth and protozoan parasites present. Results are assigned semi-quantitative results (Rare, few, moderate, high, very high). Recommended for use in dogs and cats.
- McMaster Count: This method is typically used to quantify strongyle It is typically used in equines.
- Fecal sedimentation: Sedimentation methods detect nematode larvae and trematode This test should be requested if lungworms or trematodes are suspected.
- Heartworm Antigen and Knotts/filter test: The American Heartworm Society recommends using both an antigen test and a microfilaria test for the most sensitive detection of heartworm. https://www.heartwormsociety.org/veterinary-resources/american-heartworm-society-guidelines
- Giardia Antigen Test: This test should be used as a confirmatory test when Giardia is suspected; it should not be used as a screening test in otherwise healthy animals.
Considerations for interpretation of results:
Small companion animals: In contrast to livestock where a certain level of parasitism is expected and managed, it is often desirable to aim for total elimination of parasites in dogs and cats. If drug resistance is suspected, please contact the lab. For each parasite there are a number of test limitations and diagnostic strategies to differentiate between the expected features of parasite life cycles and true drug resistance.
Equines: The emergence of drug resistance in strongyles and ascarids has led to a coordinated effort in the equine community to engage in regular diagnostic testing and selective use of deworming medications. The AAEP recommends an annual fecal egg count testing (McMaster test) before and after treatment for evaluation of drug efficacy. We recommend practitioners consult the AAEP recommendations for detailed and up-to-date information about best practices in equine parasite control: https://aaep.org/resource/internal-parasite-control-guidelines/
Created by:
Matthew T. Brewer, DVM, PhD, Dipl. ACVM Associate Professor
Department of Veterinary Pathology
College of Veterinary Medicine