W: Whipworms (Trichuriasis)

Whipworms (Trichuriasis)

BASICS

OVERVIEW

The whipworm, Trichuris, occurs in the cecum of dogs (T. vulpis) and cats (T. felis). Feline trichuriasis is rare in the United States.
Life cycle is direct; infection is acquired by ingestion of larvated eggs present in environments contaminated with feces; infective eggs can persist in the environment for months to years.
Infection can be asymptomatic or cause bloody diarrhea and large bowel inflammation.
Clinical signs can occur before patency, i.e., before eggs are shed in feces; prepatent period is approximately 70–90 days.
No extra-intestinal migration occurs.

SIGNALMENT

Dogs, cats of any age, breed, and sex
Rarely seen in cats in the United States

SIGNS

Range from asymptomatic to severe.
Intermittent large bowel diarrhea often containing mucus and fresh blood (hematochezia).
Bloody diarrhea with dehydration, anemia, and weight loss in severe cases.
Signs can occur before eggs detectable in feces.
Acute to chronic debilitation.

CAUSES & RISK FACTORS

Ingestion of infective (larvated) trichurid eggs from environment contaminated with feces of infected dog.
Eggs accumulate in environment and remain infective for months to years, especially in soil and dirt runs in moist, shady areas.
Return of dog to an environment contaminated with infective eggs after anthelmintic treatment will result in reinfection.

DIAGNOSIS

DIFFERENTIAL DIAGNOSIS

Bacterial (spirochaetal) infections of cecum.
Hookworm infection—identify eggs in feces; signs include anemia, pale mucous membranes, and melena rather than fresh blood in feces.
Capillarid infections (Pearsonema, Eucoleus)—eggs similar in appearance but smaller with roughened surface; infect urinary or respiratory tracts, respectively, rather than GI tract; usually asymptomatic.
Secondary pseudohypoadrenocorticism in severe trichuriasis with metabolic acidosis, hyponatremia, hyperkalemia, and dehydration; normal ACTH stimulation response in trichuriasis.

CBC/BIOCHEMISTRY/URINALYSIS

Usually normal; hyponatremia, hyperkalemia, and metabolic acidosis can occur in very severe cases.

OTHER LABORATORY TESTS

ACTH stimulation test in severe cases with electrolyte disturbances to differentiate trichuriasis from hypoadrenocorticism.

IMAGING

N/A

DIAGNOSTIC PROCEDURES

Centrifugal flotation of feces in sugar solution (s.g. > 1.2) preferred method.
Differentiate Trichuris eggs (brown, ovoid or lemon-shaped with prominent bipolar plugs, smooth shell, single cell within egg, ∼90 × 45 μm) from similar capillarid eggs (smaller, roughened shell surface).

TREATMENT

Outpatient treatment with anthelmintic for most cases.
Severe cases with dehydration and electrolyte disturbances require inpatient fluid therapy plus anthelmintic.

MEDICATIONS

DRUG(S)

Fenbendazole 50 mg/kg PO q24h for 3 days; repeat monthly 3 times; extra-label use in cats.
Febantel/praziquantel/pyrantel pamoate—label dose PO in dogs.
Milbemycin oxime 0.5 mg/kg PO q30 days in dogs.
Moxidectin/imidacloprid, label dose in dogs.

CONTRAINDICATIONS/POSSIBLE INTERACTIONS

Too rapid correction of hyponatremia in severe cases could result in iatrogenic myelinolysis.

FOLLOW-UP

PATIENT MONITORING

Repeat fecal examination for trichurid eggs and/or retreat with anthelmintic at 3 weeks and at 3 months following initial treatment or once a month for 3 months to detect and eliminate recently matured adults.

PREVENTION/AVOIDANCE

Prompt removal and disposal of feces to prevent environmental contamination with infective eggs.
Antehlmintic treatment of infected dogs to prevent shedding of eggs and contamination of environment.

EXPECTED COURSE AND PROGNOSIS

Good prognosis following treatment and implementation of preventive measures.

MISCELLANEOUS

ZOONOTIC POTENTIAL

Relatively rare cases of human infection with T. vulpis have been diagnosed based on morphologic differences between eggs of the human whipworm, T. trichiura, and those of T. vulpis.

ABBREVIATIONS

ACTH = adrenocorticotropic hormone
GI = gastrointestinal

INTERNET RESOURCES

www.capcvet.org.