Adult Trichuris vulpis are 45–75 mm long and consist of a long, slender anterior portion and a thick posterior third. They commonly inhabit the cecum and colon of dogs, where they are firmly attached to the wall with their anterior end embedded in the mucosa. Thick-shelled eggs with bipolar plugs are passed in the feces and become infective in 1–2 mo in a warm, moist environment. Although eggs may remain viable in a suitable environment for up to 5 yr, they are susceptible to desiccation. The life cycle is direct. After infective eggs are ingested, the larvae hatch and develop in the wall of the distal ileum, cecum, and colon, and the adults mature in ~11 wk. They may remain for up to 16 mo.
No signs are seen in light infections, but as the worm burden increases and the inflammatory (and occasionally hemorrhagic) reaction in the cecum and colon becomes more pronounced, weight loss and diarrhea become evident. Fresh blood may be seen in the feces of heavily infected dogs, and anemia occasionally follows.
Trichuris infections are rarely seen in cats in North and South America and the Caribbean but may occasionally be associated with clinical signs similar to those described for dogs.
The eggs are susceptible to desiccation; therefore, by maintaining cleanliness and eliminating moist areas, the risk of infection in dogs can be reduced considerably, although T vulpis infections can be difficult to control. For anthelmintic treatment of dogs, approved compounds include febantel, fenbendazole, milbemycin, moxidectin (topical), and oxantel (see Table: Drugs for Intestinal Helminths of Dogs Approved in the USA and UK). Treatment should be repeated three times at monthly intervals because of the long prepatent period. Finally, milbemycin, milbemycin/lufenuron, milbemycin/spinosad, milbemycin/praziquantel, and moxidectin/imidacloprid, when administered for heartworm prevention, are also approved for control of T vulpis infections.
Effective therapy has yet to be described for Trichuris infections in cats. If required, treatment should be attempted on an experimental basis using a compound with approved activity against T vulpis.