Trichuris vulpis is a 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 μm in length and 32–40 μm 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 invade the cells of the Crypts of Leiberkuhn in the colon. The J3 larvae grow and molt while burrowing in the epithelium toward the luminal surface. These worms can invade intestinal cells in many places, but there is no evidence that worms can develop to maturity except in the cells of the colon, or that worms develop in the duodenum and migrate to the colon. Once an adult, their posterior end enlarges (the 'handle of a whip') and bursts into the lumen of the colon. The whip-like anterior end remains in the cells of the large intestinal walls. 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.