Roundworms are extremely common in domestic dogs, especially in newborns. Fortunately, they are not particularly difficult to diagnose. A veterinarian presented with a puppy showing signs of internal parasites will take a history from the owner and perform a thorough physical examination. He probably will also take a blood sample to run routine blood work, including a complete blood count and a serum biochemistry panel. A urine sample may also be taken for a urinalysis, which is another common test performed as part of an initial work-up. The results of these tests may suggest that the puppy has an internal parasite infection. For example, the puppy may be anemic (have low levels of circulating red blood cells), have liver enzyme abnormalities, or have abnormal numbers of circulating white blood cells, which can reflect a mounting immune response to internal parasites.
The best way to diagnose roundworms is to analyze the dog’s feces. The simplest way to do this is through a fecal flotation. This test is performed on a small, fresh fecal sample, which usually is taken manually at the veterinary clinic. It can also be done on a fresh stool sample brought in by the dog’s owner. The fecal sample will be mixed with a solution that has specific chemical properties which enable parasite eggs and cysts to float to its surface. After the solution and the feces are mixed in a glass beaker, the mixture will be strained into a test tube. A thin glass coverslip will be placed on top of the full test tube, coming into direct contact with the mixture. The contents of the tube will then be mixed mechanically in a centrifuge, at a set speed for a defined period of time. After being spun, the tube will be allowed to sit, so that any parasite eggs and cysts can float to the surface. In theory, after this process, the eggs and cysts will rise to the surface and stick to the glass coverslip, which will be in direct contact with the mixture.
After an appropriate resting period, the coverslip will be carefully removed, placed sample-side down onto a regular glass slide and examined under a microscope. The eggs of many different internal parasites, including roundworms, can be identified in this fashion. Most parasite eggs look different depending upon their species. Because roundworm eggs are excreted sporadically in the feces of an infected dog, a single negative result from a fecal flotation test does not necessarily mean that the dog is free from these parasites. However, a positive test, especially if lots of eggs are identified, is always diagnostic.
Another way to diagnose roundworms is by examining a fecal smear. The stool sample for this test is taken directly from the dog’s anus with a cotton swab, smeared on a glass slide, sometimes stained with certain dyes and then examined under a microscope for bacteria, parasite eggs and other abnormalities. This test is less specific and less commonly used for internal parasites than is the fecal floatation.
Sometimes, adult roundworms (or pieces of adult worms) can be seen in the vomitus or feces of infected dogs. This is not especially common, which probably is a good thing because adult roundworms are quite large and usually are disturbing to owners who see them.
Most veterinarians can easily perform an in-house fecal floatation on a fresh stool sample. The results will be available in short order. Roundworm infections are common and potentially dangerous to young puppies. Owners should be sure that their puppies are de-wormed appropriately from birth, and they should follow an appropriate de-worming protocol according to the puppy’s veterinarian.