Dog laying on dog bed

What Have You Forgotten About Whipworms?

April 2022 by Dr. Matt Stevens

Whipworms are among the most frustrating of the common intestinal parasites that you will face in clinical practice. Infections can be difficult to detect. Clinical signs can vary widely, from none to intermittent large bowel diarrhea. A severe whipworm infestation can present as a critical and life-threatening illness.1,2

Trichuris vulpis is a known cause of pseudo-Addison’s disease. Much like hypoadrenocorticism, patients can present with life-threatening clinical signs including hyperkalemia, hyponatremia and hypovolemic shock that without immediate treatment can be fatal.1

Dogs with less severe signs may improve for a while after being treated for something else, simply by chance. With time, the problem returns, the client is back in your clinic and everyone’s level of frustration climbs.

It’s easy to forget about whipworms when working up a seemingly simple case of diarrhea. When faced with the problem, we are more likely to think of hookworms, roundworms, Giardia or the ever-popular garbage enteritis (He ate what??!!). But whipworms have three characteristics that should keep them on your differential list: They are patient, sneaky and persistent.

Treating and controlling whipworm infections is much easier when you keep these three characteristics in mind. This brief refresher will help you get on top of most cases.

The whipworm is a patient critter

Meet Trichuris vulpis, the canine whipworm. Adult worms really do look like whips, with a short, thick “whip handle” attached to a longer, thinner portion that makes up about 75% of the worm’s length of four to seven centimeters. These adults live primarily in the dog’s cecum; the thick portion remains in the intestinal lumen while the thin end penetrates the cecal mucosa. Adult whipworms live off the dog’s mucosal epithelium, blood and tissue fluids.2

Although she may lay up to 2,000 eggs per day, the female whipworm is patient. She doesn’t produce eggs daily. Days or even weeks can pass between shedding episodes, making detection a matter of “the luck of the draw” on sampling days.2

Nonetheless, when she finally lays eggs, they contaminate the dog’s environment. Whipworm eggs are patient too. Although they usually embryonate within nine to 21 days, they can remain infective in dog parks and dirt patches for years before being ingested by an unsuspecting dog. When a dog finally does ingest Trichuris eggs, the larvae hatch and develop in the mucosal lining of the small intestine for up to 10 days.2

After maturing, the larvae re-enter the intestinal lumen, migrate to the cecum and make themselves at home. From the day the dog ingests the embryonated egg, 74-90 days will pass until female adult worms begin shedding more eggs. Add that to the long periods that eggs can persist in the soil, and you can see why we think of whipworms as patient critters!2

Sneaky little creeps

If you are lucky enough to win the fecal float lottery and receive a sample on a day when the female is shedding, the battle is not over. Like a stealth fighter plane, the whipworm egg is hard to detect. Careful attention to fecal examination technique is essential.3

Trichuris vulpis eggs are very dense, with a specific gravity of approximately 1.15. A more concentrated fecal solution, such as a sugar solution with specific gravity of 1.25, must be used or the eggs will not float. Centrifugation of the sample prior to placing the slide for floating will also increase your likelihood of finding eggs.2

Trichuris vulpis eggs are barrel-shaped, with an additional plug on each end. They measure approximately 72-90 micrometers long and 32-40 micrometers wide. These sneaky little eggs can resemble the eggs of some lungworms and even some parasites found in the urinary tract.2 Make sure that your team can’t be fooled.

In cases where you strongly suspect whipworms but can’t find them, for example in dogs with negative Giardia tests, chronic intermittent diarrhea and a parasite control program that does not address Trichuris, a fecal antigen test may be indicated. These tests can detect the presence of whipworms even in cases when eggs are hard to find, like an infection with very few worms or a single-sex infection.2,4

At a minimum, finding the sneaky whipworm requires close attention to fecal floatation technique and may require testing multiple samples over time.

Nevertheless, they persist

Whipworm eggs are thick and tough, like little oak barrels. They can survive desiccation, extreme temperatures and even ultraviolet radiation.2 This lets them persist in the soil, as many of the conditions that kill the eggs from other parasites don’t faze the whipworm egg in the slightest. A related species, the human whipworm Trichuris trichiura, can survive temperatures up to 126˚F and down to -16˚F.5 That’s persistence!

Whipworm eggs can easily build up in a dog’s environment. One dog with an untreated infection can seed the local dog park with thousands of eggs, leading to infections in many more dogs. That’s why it’s important to have all dogs on an effective Trichuris control program.

How prevalent are whipworms? A recent study of parasite prevalence in 288 dog parks in 30 metropolitan areas found Trichuris vulpis in 18%, or nearly one in five (1 in 5) of the parks tested.6

The bad news is that every dog that visited each of those parks was at risk, and a hot summer or cold winter would not reduce that risk.

The good news is that you have powerful tools to deal with this patient, sneaky and persistent parasite.

What’s your whipworm control strategy?

Whipworms may be patient, sneaky and persistent, but people can be patient and persistent too. And we don’t need to sneak around. Regular deworming with a product effective against whipworms can provide the protection your canine patients need.

SENTINEL® SPECTRUM® Chews (milbemycin oxime/lufenuron/praziquantel) and SENTINEL® FLAVOR TABS® (milbemycin oxime/lufenuron) both contain milbemycin oxime, which removes adult whipworms and controls whipworm infections. One easy and tasty dose, once each month, will deal with the tricky Trichuris.7,8

Your clients want to know when their dog is at risk. According to a recent Companion Animal Parasite Council study, nine of 10 pet owners want to know if there is a high parasite prevalence in their area. They want to hear about it from you. In fact, 78% of pet owners in this survey considered their veterinarian to be their primary source for information on parasites that affect their pets.9 You have the expertise to advise them about protecting their pets, and they know it.

Prescribing SENTINEL SPECTRUM Chews or SENTINEL FLAVOR TABS as your monthly parasite prevention product lets you treat for whipworms regularly. SENTINEL FLAVOR TABS have been shown to kill 99.6% of Trichuris vulpis in naturally infected dogs.10 Why would you use anything less effective?

Yes, whipworms are patient, sneaky and persistent. But with your knowledge, diagnostic tests and SENTINEL Brand products, you can help your clients protect their dogs against Trichuris vulpis.

For more information about parasite prevention with SENTINEL SPECTRUM Chews or SENTINEL FLAVOR TABS, contact your Merck Animal Health Professional Services Veterinarian.

Important Safety Information

SENTINEL® SPECTRUM® Chews (milbemycin oxime/lufenuron/praziquantel). Dogs should be tested for heartworm prior to use. Mild hypersensitivity reactions have been noted in some dogs carrying a high number of circulating microfilariae. Treatment with fewer than 6 monthly doses after the last exposure to mosquitoes may not provide complete heartworm prevention. For complete product information refer to the product insert. SENTINEL® FLAVOR TABS® (milbemycin oxime/lufenuron). Dogs should be tested for heartworm prior to use. In a small percentage of treated dogs, digestive, neurologic, and skin side effects may occur. For complete product information refer to the product insert.


  1. Venco L, Valenti V, Genchi M, Grandi G. A dog with pseudo-Addison disease associated with Trichuris vulpis infection. J Parasitol Res. 2011;2011:682039.
  2. Trichuris vulpis. Companion Animal Parasite Council (CAPC) website. Updated July 28 2020. Accessed March 3, 2022.
  3. Gates, MC, Nolan, TJ. Comparison of passive fecal flotation run by veterinary students to zinc-sulfate centrifugation flotation run in a diagnostic parasitology laboratory. J Parasitol. 2009;95(5): 1213-1214.
  4. Elsemore, DA, Geng J, Flynn L, Cruthers L, Lucio-Forster A, Bowman DD. Enzyme-linked immunosorbent assay for coproantigen detection of Trichuris vulpis in dogs. J Vet Diagn Invest 2014;26(3):404.411.
  5. Spickler, AR. Trichuriasis. The Center for Food Security & Public Health website. Updated January 2019. Accessed March 3, 2022.
  6. Stafford, K., Kollasch TM, Duncan KT, et al. Detection of gastrointestinal parasitism at recreational canine sites in the USA: the DOGPARCS study. Parasit Vectors 2020;13:275.
  7. SENTINEL® SPECTRUM® Chews [product label]. Madison, NJ: Merck Animal Health; 2020.
  8. SENTINEL® FLAVOR TABS® [product label]. Madison, NJ: Merck Animal Health; 2020.
  9. CAPC-Bayer study results released at NAVC 2015. Companion Animal Parasite Council press release, January 19, 2015. CAPC website. Accessed March 3, 2022.
  10. Bowman DD, Legg W, Stansfield DG. Efficacy of moxidectin 6-month injectable and milbemycin oxime/lufenuron tablets against naturally acquired Trichuris vulpis infections in dogs. Vet Ther. 2002;3(3):286-289.

About the author

Dr. Matthew Stevens meet the team

Matt Stevens

Sr. Professional Services Veterinarian,
Shenandoah Valley Region (KY, VA)