TRICHURIS VULPIS

Trichuris vulpis is whipworm that lives in the large intestine of canines in its adult stages. Out of different types of worms, Trichuris vulpis is one of the smaller worms with a size ranging from 30-50 mm in length . As the name suggests, the worm has a whip-like shape with distinct features including a small, narrow anterior head, which is the digestive part of the worm, and a larger posterior tail, which is the reproductive part of the worm. Eggs from T. vulpis are oval shaped with bipolar plugs and contain a thick outer shell. Their sizes range from 72-90 um in length and 32-40 um in width. Because of their thick outer shell, T. vulpis eggs are very resistant to environmental extremes such as freezing or hot temperatures, thus allowing for their long viability in the outside world. 

LIFE CYCLE

The life cycle of Trichuris vulpis begins with the adult whipworms living in the large intestines of dogs. T. vulpis lay many eggs in the large intestine and are released in the feces into the outside environment. When eggs are released into the outside environment, these unembryonated eggs are able to form embryos in the soil in about 2-4 weeks, at which point they become infective when ingested by the new host . An infective larva develops within the egg before it is even ingested by the new host.  Another canine becomes a new host by ingesting the egg containing the larva. Once ingested, the egg gets into the small intestine where it hatches to release its larva. The larvae invade the small intestinal mucosa and remain there for about 15 days. Afterward, the larva then travel from the small intestine into the large intestine where they go through several stages to become an adult whipworm in the large intestine. Once an adult, their whip-like shape containing a narrow anterior head allows them to burrow through the large intestinal walls while their posterior reproductive end protrudes them into the lumen. Adult whipworms live inside the cecum, colon, and rectum for about three months before they lay eggs intermittently to be released in feces where they can become infective to another host.

EPIDEMIOLOGY

T. vulpis infects canines worldwide. In the United States, it has been reported that 14.3% of shelter dogs are infected with this parasite . Though rare, there are some cases of human infection. The eggs of T. vulpis are prevalent in shady moist soil areas that have been contaminated by canine feces.

PATHOLOGY AND SYMPTOMS

Because the eggs of T. vulpis eggs are very resistant from desiccation, they can live in soil for up to seven years. Once ingested by the canine, the eggs hatch and the resulted larvae live in the small intestine. At this point, though infected, the canine is still asymptomatic. When adult form, T. vulpis live primarily in the cecum with its anterior end attached to the superficial mucosa and its posterior end extended to the cecal lumen where it consumes the canines blood, tissue fluid, and mucosal epithelium. Severe infections include symptoms such as bloody diarrhea, weight loss, dehydration, and anemia, and in extreme cases, death.

DIAGNOSIS

Infection of this parasite can be confirmed with detection of eggs in the canines feces. However, this is difficult because egg production is usually small, its shedding is periodic, and its structure is dense which prevents from floating. Symptoms may appear before the eggs are shed in the feces due to the long prepatent period.

PREVENTION AND CONTROL

Keeping canines away from contaminated areas, especially areas where there are feces can prevent them from contracting T. vulpis. There is no effective way to kill the parasite's eggs in the soil, so it is might be necessary to replace the soil and cleaning out litter boxes and kennels frequently. People cleaning these areas should wear gloves and wash their hands after task.  Dogs should have fecal examinations and deworming as necessary. If a dog is detected to be infected with T. vulpis, it should be treated immediately to prevent infection of other dogs. 

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