Trichuris vulpis

Synopsis

CAPC Recommends

• CAPC recommends testing all dogs and cats for whipworms by fecal flotation with centrifugation. Fecal tests for specific parasite antigens and PCR have been optimized for use in companion animals and are also available to aid in identification of infection.

• Puppies should be tested for intestinal parasites more frequently than adult dogs. CAPC recommends testing for intestinal parasites, including whipworms, at least four times in the first year of life and at least two times per year in adults depending on patient health and lifestyle factors.

Species

Canine


Trichuris vulpis occurs in the dog, fox, and coyote.

Feline


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.

Stages

• 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.

Disease

• 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.

Prevalence

• Prevalence surveys confirm that T. vulpis occurs in dogs worldwide.
• Whipworms are found in as many as 14.3% of shelter dogs sampled in the U.S. and 10% of dogs presented to veterinary teaching hospitals.

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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.

Diagnosis

• CAPC recommends testing all dogs and cats for whipworms by fecal flotation with centrifugation. Fecal tests for specific parasite antigens and PCR have been optimized for use in companion animals and are also available for identification of infection.
• Puppies should be tested for intestinal parasites more frequently than adult dogs. CAPC recommends testing for intestinal parasites, including whipworms, at least four times in the first year of life and at least two times per year in adults depending on patient health and lifestyle factors.
• Whipworms have a long prepatent period and the eggs are not commonly found in very young pups but infections may become evident as early as 3-6 months of age.
• Dogs of any age may have subclinical infections and show no signs of disease. However, when whipworm infections are allowed to persist, contamination of the environment with this potentially pathogenic parasite can occur.
• Even when eggs are not present, disease caused by T. vulpis may be suspected on the basis of history, clinical signs, and response to therapy; fecal ELISA can confirm a diagnosis in these suspect, egg-negative cases.
• Three issues may complicate diagnosis by detection of eggs:
  • 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.
• Fecal flotation with centrifugation
  • Diagnosis of patent whipworm infections via fecal flotation can be challenging for the reasons listed above. The use of sugar solution and centrifugation can increase the sensitivity of whipworm egg detection.
  • Mix 1 to 5 g feces and 10 ml of flotation solution (sugar sp. gr. 1.25) and filter/strain into a 15-ml centrifuge tube.
  • Top off with flotation solution to form a slightly positive meniscus, add coverslip, and centrifuge for 5 minutes at 1500 to 2000 rpm.
  • Examine for characteristic eggs.
    • Eggs of Trichuris vulpis can be differentiated from those of other capillarids (e.g. Eucoleus spp.) by size and shape (see images under Life Cycle).
      • Trichuris vulpis: 72-90µ x 32-40µ
      • Eucoleus boehmi: 54-60µ x 30-35µ
      • Eucoleus aerophilus: 58-79µ x 29-40µ
    • Coprophagia is common in dogs and capillarid eggs from other hosts may be present.
    • Whipworm infection is rare in cats in most of the United States; eggs with bipolar plugs in feline fecal samples are more likely Eucoleus aerophilus or a capillarid rather than Trichuris spp.
• Fecal tests for whipworm antigen
  • Commercial assays are available for detection of antigen produced by immature and adult whipworms in the lumen of the small intestine. Both male and female worms can be detected, and antigen production is not linked to egg production.
  • Diagnosis by detection of antigen allows identification of prepatent and single sex infections, supporting use of preventives and allowing earlier treatment.
  • Both centrifugal fecal flotation and fecal antigen tests have their strengths and weaknesses, however to ensure the widest breadth of detection of intestinal parasites in dogs and cats, fecal tests for antigen should be combined with microscopic examination of feces for eggs.
• Fecal PCR tests for Whipworms
  • Nucleic acid is stable in the feces for 10 days at 4ºC.
    
  • Presence of DNA in feces is not linked to egg production.

Trichuris ova

Treatment

• 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) (Elanco)
  • Panacur® (fenbendazole [50 mg/kg]) for 3 consecutive days (Merck Animal Health)
  • 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:
  • Advantage Multi (moxidectin [2.5 mg/kg] and imidacloprid [10 mg/kg]) (Elanco)
  • Coraxis™ Topical Solution for Dogs (moxidectin [2.5mg/kg]) (Elanco)*
  • Interceptor® (milbemycin oxime [0.5 mg/kg]) (Elanco)
  • Interceptor® Plus (milbemycin oxime [0.5 mg/kg] and praziquantel [5 mg/kg]) (Elanco)
  • MilbeGuard™ (milbemycin oxime [0.5 mg/kg] (Ceva)
  • Sentinel (milbemycin oxime [0.5 mg/kg] and lufenuron [10 mg/kg]) (Merck Animal Health)
  • Sentinel Spectrum (milbemycin oxime [0.5 mg/kg], lufenuron [10mg/kg], and praziquantel [5mg/kg]) (Merck Animal Health)
  • Trifexis® (milbemycin oxime [0.5 mg/kg] and spinosad [30 mg/kg]) (Elanco)

Control and Prevention

Control of T. vulpis can be achieved by use of an appropriate monthly broad-spectrum heartworm prevention products that also control whipworms (see Treatment).

If unable to consistently administer a monthly preventive, then treat adult pets four times a year with an appropriate broad-spectrum anthelmintic with efficacy against internal parasites. This should coincide with appropriate fecal diagnostics.

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.

Selected References

• 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.

• Elsemore DA, Geng J, Flynn L, Cruthers L, Lucio-Forster A, Bowman DD. 2014. Enzyme-linked immunosorbent assay for coproantigen detection of Trichuris vulpis in dogs. JVDI. 26:404-411.