How Whipworms are Diagnosed
Whipworms are not particularly difficult for a veterinarian to diagnose. Sometimes, they are only detected during a routine fecal examination. Dogs brought to a veterinary clinic with gastrointestinal symptoms will be given a thorough physical examination and typically will have blood drawn for routine blood work, including a complete blood count and a serum biochemistry profile. The veterinarian will take a history from the dog’s owner and may also recommend a urinalysis as part of the initial work-up. The results of these tests may indicate an internal parasite infection. If the dog has suffered from prolonged severe diarrhea, it may be dehydrated, and its blood sodium-to-potassium ratio may be off as well.
The best and most common way to diagnose whipworms is through a procedure called “fecal floatation.” This test is performed on a small fresh fecal sample, which usually is obtained manually at the veterinary clinic. The test can also be done on a fresh sample brought in by the owner. The fecal specimen is mixed with a solution that has specific chemical properties that encourage parasite eggs to float to its surface. Some common flotation solutions are sodium nitrate, zinc sulfate and “Sheather’s solution,” which is a sugar solution used by many commercial veterinary laboratories.
After the solution and the fecal sample are combined, the mixture is strained into a test tube. A glass coverslip is placed on top of the tube, touching the liquid mixture. The tube is placed in a centrifuge and mixed mechanically at a set speed for a set period of time, then rested to allow time for the eggs to float to the surface. This is the procedure for most types of centrifuge instruments; with other machines, the laboratory personnel will spin the sample before covering it. Either way, after an appropriate resting period, the coverslip will be removed, placed wet-side down onto a clean glass slide and evaluated under a microscope.
The eggs of a number of different internal parasites can be identified by this procedure. In the case of whipworms, identifiable eggs are shed in low numbers and only intermittently. As a result, a single negative fecal floatation does not necessarily mean that the patient is free from whipworms. Veterinarians often recommend performing a series of fecal floatations over several days or weeks, before whipworm infection is ruled out. Of course, a positive fecal floatation test, especially if a large number of characteristic eggs are identified, is diagnostic of whipworms.
Some of the symptoms of Addison’s disease (hypoadrenocorticism) can closely mimic those of whipworm infestation, especially those caused by low levels of circulating sodium and potassium. Because of this, the dog’s veterinarian may suggest performing an ACTH response test to rule out Addison’s. ACTH stands for adrenocorticotropic hormone. It is produced and secreted in the brain by the pituitary gland and normally stimulates the adrenal glands to secrete key hormones, including corticosteroids, into the bloodstream. The cortisol levels in dogs with whipworms will rise after administration of ACTH, whereas in dogs with Addison’s disease the ACTH will have no measurable effect.
Endoscopy can be used to detect the presence of whipworms in the large bowel. This procedure, also known as a colonoscopy, can help the veterinarian actually see the adult parasites through a tiny camera located on the end tip of the instrument. However, endoscopy is fairly expensive and normally is not necessary to diagnose whipworm infection in dogs.
In a mild case of suspected whipworm infection, the attending veterinarian may elect to treat the dog with an anti-parasitic medication even before a definitive diagnosis of whipworms or any other gastrointestinal parasite is reached. This can be an effective, relatively inexpensive and safe way to both diagnose and treat the condition in one fell swoop. Currently, the drug most commonly used in this fashion is fenbendazole.