Diagnosing Worms in Pets Not Always Simple

Jennifer Coates, DVM
By Jennifer Coates, DVM on Apr. 21, 2014

Intestinal parasites are a common problem faced by almost every pet owner. Despite this, confusion over how to deal with “worms” seems to be the norm. Let me see if I can clarify why veterinarians and pet owners don’t always see eye to eye on how best to “worm” (actually deworm) a dog or cat. The following is how I usually handle these cases and why I take the approach I do.

First, I check the pet’s medical record to make sure that I’ve performed a physical exam within a reasonable amount of time. For a healthy adult animal, that will usually be about one year. For the very young, old, or those individuals with chronic health problems, it might be between one and six months. If I haven’t seen your pet recently or am concerned that intestinal parasitism might make your pet especially sick, I’m not comfortable proceeding without examining them first.

Next, I’ll ask for a description of your pet’s symptoms and the worms that you’ve seen. If the dog or cat is not eating and drinking well, is lethargic or depressed, or has vomiting or diarrhea, I’ll want to see them to assess whether additional therapy is necessary before prescribing a dewormer. When the pet seems to be feeling fine, a good description of the worm(s) may help you avoid a trip to the clinic. This is especially true in the case of tapeworms. Tapeworms have a distinctive appearance — they are “ribbon-like,” being flattened from top to bottom, and typically shed segments of their bodies in a pet’s feces. These segments look like squished pieces of rice. If it sounds like we’re dealing with tapeworms and all the other conditions we’ve talked about have been met, I’ll recommend a dewormer that will be effective against tapeworms — usually one containing the active ingredient praziquantel.

If tapeworms seem unlikely, I will ask for you to bring a fresh fecal sample to the clinic for examination. Fecal examinations are noninvasive, cheap, simple to perform, and often allow us to diagnose exactly what type of intestinal parasite were dealing with, including those that cannot be identified with the naked eye. A fecal flotation will detect many types of worm eggs (roundworms, hookworms, whipworms, less frequently tapeworms) and protozoan cysts (Giardia, Toxoplasma, Tritrichomonas). I may also add a fecal smear if I’m especially concerned about the presence of protozoa.

The reason for all this back and forth is simple. No single medication will eradicate every type of intestinal parasite a dog or cat might be harboring. A specific diagnosis allows the veterinarian to prescribe the most effective and least expensive medication and make recommendations that can prevent reinfection or spread of the parasite to other pets or even to people. Sure, products are available that kill multiple types of worms. I happily use them when fecal testing is negative but I still suspect that worms are present (no test is 100% accurate, after all). However, this shotgun approach is second best to diagnosing and treating the particular type of parasite that is making its home in your dog or cat.

Dr. Jennifer Coates

Image: Thinkstock

Related Content:

Intestinal Worms in Dogs (and Cats) 101

Tapeworm in Cats

Tapeworm in Dogs

Jennifer Coates, DVM


Jennifer Coates, DVM


Dr. Jennifer Coates is an accomplished veterinarian, writer, editor, and consultant with years of experience in the fields of veterinary...

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