Current Advice on Parasite Control:
Intestinal Parasites - Whipworms
Trichuris vulpis occurs in the dog, fox, and coyote.
Although feline whipworms occur in tropical areas, they appear to be rare in domestic cats in North America; putative whipworm eggs in feline fecal samples are more likely to be a capillarid other than Trichuris sp.
- For this reason, feline whipworms will not be discussed further in this document, but additional information about feline whipworm infections can be obtained by consulting Bowman DD et al., 2002. Feline Clinical Parasitol, 348-350.
Overview of Life Cycle
- Eggs are unembryonated when passed in feces and are highly resistant to desiccation, extremes in temperature, and ultraviolet radiation. Eggs embryonate in 9 to 21 days (or longer) depending on the temperature and moisture content of the soil. Infective whipworm eggs can remain viable for many years.
- Hosts are infected by ingesting embryonated eggs from the soil or other substrates in which eggs are found.
- Larvae hatch from eggs (generally in the small intestine) and penetrate the mucosa. They develop for 2 to 10 days in the mucosa, move to the cecum (occasionally the terminal small intestine or colon), and mature to adult worms.
- The prepatent period of T. vulpis is 74 to 90 days.
- Whipworms are named for their characteristic whip-shaped body. The body is composed of a thin, filamentous, anterior end (the “lash” of the whip) and a thick posterior end (the “handle” of the whip). Adult worms are 4.5- to 7.5-cm long. Approximately 75% of their length is composed of the anterior (lash) portion of the whipworm (see image on right).
- Eggs are football or barrel-shaped and yellow-brown, with prominent bipolar end plugs and a smooth shell.
- Eggs are approximately 79 by 38 μm (link to image). They must be distinguished from eggs of Eucoleus spp. and Pearsonema spp., which are smaller and have a rough surface (see Lungworm Guidelines and Urinary Nematode Guideline).
- Larvae hatch from ingested embryonated eggs and enter the mucosa of the small intestine (occasionally the large intestine). Larvae reenter the lumen and move to the cecum where they mature to adult worms (see image on right).
- Adult worms begin producing eggs between 74 and 90 days after infection. Each female T. vulpis can produce more than 2,000 eggs per day.
- Many canine whipworm infections are either asymptomatic or subclinical.
- Some infections result in hemorrhagic typhilitis or colitis characterized by diarrhea that is often streaked with mucus and fresh blood.
- Severe infections result in bloody diarrhea, weight loss, dehydration, anemia, and in the most extreme cases, death.
Host Associations and Transmission Between Hosts
- Dogs acquire T. vulpis infections only by ingesting eggs containing infective larvae from the environment.
- Indirect transmission between animals via paratenic hosts and transplacental or transmammary transmission from the dam to her offspring does not occur.
Prepatent Period and Environmental Factors
- The period from ingestion of embryonated eggs until eggs appear in feces is 74 to 90 days.
- Infective whipworm eggs may persist in the environment for several years.
Site of Infection and Pathogenesis
- Developing larvae of T. vulpis live in the mucosa of the small intestine (rarely the large intestine).
- Development of larvae in the mucosa does not appear to result in demonstrable disease.
- Trichuris vulpis adults live primarily in the cecum. Occasionally adult worms are recovered from the posterior small intestine or the anterior large intestine.
- Adult worms thread their anterior ends through the superficial mucosa. The larger posterior end extends into the cecal lumen.
- Adult whipworms consume blood, tissue fluids, and mucosal epithelium.
- Feeding habits of the worms can result in bloody diarrhea, weight loss, dehydration.
- Trichuris vulpis infections are usually diagnosed by detecting characteristic eggs in feces.
- o Even when eggs are not present, disease caused by T. vulpis may be identified on the basis of history, clinical signs, and response to therapy.
Three issues may complicate diagnosis:
- Because of the long prepatent period, infected animals may show clinical signs before eggs are shed in the feces.
- Eggs may be shed intermittently.
- Eggs are quite dense (average specific gravity = 1.15); proper technique (centrifugation) must be used to recover them on fecal flotation. The use of sugar solution and centrifugation can increase the sensitivity of whipworm egg detection.
The following anthelmintics are approved for treatment of T. vulpis infections in dogs:
- Drontal Plus® (febantel [25 mg/kg], pyrantel pamoate [5 mg/kg], and praziquantel [5 mg/kg]), single administration)
- Panacur® (fenbendazole [50 mg/kg]) for 3 consecutive days
- To achieve control, treatment can be administered once a month for 3 months.
The following anthelmintics are approved for treatment and the continued monthly treatment of T. vulpis infections in dogs:
- Interceptor® (milbemycin oxime [0.5 mg/kg])
- Sentinel (milbemycin oxime [0.5 mg/kg] and lufenuron [10 mg/kg])
- Advantage Multi (moxidectin [2.5 mg/kg] and imidacloprid [10 mg/kg])
- Trifexis® (milbemycin oxime [0.5 mg/kg] and spinosad [30 mg/kg])
- The following anthelmintics are approved for treatment of T. vulpis infections in dogs:
Control and Prevention
- Prevention of T. vulpis infections requires reducing exposure of dogs to embryonated eggs in the environment. This is best achieved by promptly removing feces from yards and other environments where dogs defecate.
- Perform periodic fecal examinations as described in the section on Fecal Examination Procedures and treat infected dogs immediately with one of the products described previously in the Treatment section.
- Control of T. vulpis can be achieved by use of monthly broad-spectrum heartworm prevention products that also control whipworms (see Treatment).
Public Health Considerations
- Although there are reports in the medical literature of human infections with T. vulpis, these reports lack sufficient validation to consider T. vulpis a zoonotic parasite at this time.
- Bowman DD, Legg W, Stansfield DG, 2002. Efficacy of moxidectin 6-month injectable and milbemycin oxime/lufenuron tablets against naturally acquired Trichuris vulpis infections in dogs. Vet Therapeutics 3:286-289.
- Dryden MW, Payne PA, Ridley R, Smith V. 2005. Comparison of common fecal flotation techniques for the recovery of parasite eggs. Veterinary Therapeutics. 6: 15-28.
- Kirkova Z, 2003. Studies on the life cycle of Trichuris vulpis. Bulgarian J Vet Med 6:35-42.
- Nolan T, Smith G. 1995. Time series analysis of the prevalence of endoparasitic infections in cats and dogs presented to a veterinary teaching hospital. Veterinary Parasitology. 59: 87-96.
- Traversa D. 2011. Are we paying too much attention to cardiopulmonary nematodes and neglecting old fashioned worms like Trichuris vulpis? Parasites and Vectors 4:32.