Diagnostic tests are needed to identify giardiasis and exclude other diseases. Tests may include: A complete medical history and a thorough physical examination. Specific diagnostic tests will be needed for your veterinarian to diagnose giardiasis in your pet.
Direct examination of a fecal smear under the microscope. The trophozoites are more likely to be seen in diarrhea and the parasite can be recognized by its rapid forward motion. Cysts are more likely to be found in semi-formed feces. It takes considerable expertise to be able to recognize cysts.
Fecal enzyme-linked immunosorbent assay (ELISA) test to detect substances given off by the trophozoites in feces. Your veterinarian may be able to perform the test in the office or may send a fecal sample to a laboratory that conducts the test.
Zinc sulfate concentration test. A fecal sample is mixed with a zinc sulfate solution in a test tube and, after a few minutes of processing, Giardia cysts (if present) will float to the top of the solution where they can be collected and identified under the microscope. If this test is performed on three separate fecal samples from the same cat, it will detect Giardia more than 96 percent of the time in infected animals.
Several drugs have been used to treat Giardia infections in pets. Anti-parasitic drugs are the most important part of treatment, but additional measures such as adding fiber to the diet can improve stool consistency and hasten your pet's recovery. Specific treatments include:
Metronidazole is an antibiotic that has been widely used to treat Giardia in cats as well as in people. This drug has reasonable efficacy against Giardia and has the added advantage of being effective against other parasitic protozoa and some bacteria that may also have contributed to the diarrhea. Adverse effects on the nervous system have occurred with high doses.
Fenbendazole is a de-worming medication that kills common parasitic worms such as hookworms, roundworms and whipworms. When given at the usual dosage, fenbendazole is also very effective against Giardia. Fenbendazole is very safe and fairly inexpensive.
The combination of praziquantel, pyrantel and febantel is another de-worming medication used against parasitic worms, such as hookworms, roundworms, whipworms and tapeworms. Recent studies show that it also is effective against Giardia. Treatment only has to be given for three consecutive days. The drug, however, is a somewhat expensive.