Trichuris trichiura

Trichuris trichiura is a nematode that is the causative agent of whipworm infection or trichuriasis.

Disease / Pathology

Trichuris trichiura light infections are asymptomatic. Increased numbers produce damage to the intestines and related symptoms. The mucosa may be hyperemic with bleeding and erosion present. Inflammation is present. The intense irritation of the lower colon and rectum may, especially in small children, result in prolapse of the rectum.

In children there is a significant loss of weight associated with heavy infections. This is due to chronic dysentery, and anemia from chronic blood loss.

There is an associated eosinophilia with these infections. The rectal mucosa can have high numbers of these eosinophils and related Charcot-Leyden crystals. Both of these when present in an ova and parasite examination will make the presence of Trichuris trichiura suspect.

Location in the Host

Trichuris trichiura is located in the large intestine, cecum, and can at times inhabit the appendix.

Geographic Distribution

Trichuris trichiura can be found worldwide but is especially prevalent in tropical and subtropical environments where the moist climate is optimal.

Life Cycle

Eggs are passed into the soil by an infected persons feces. Eggs at this stage are unembryonated. Within 2 to 3 weeks of being in the moist soil the larva is developed (embryonated egg).

Eggs are ingested and are the infective form. Once ingested the eggs hatch in the intestine and the larva migrate to the cecum. They attach to the mucosa and mature within 10-12 weeks.

Morphology and Diagnosis

Trichuris trichiura eggs can be found in the feces. The adult worms are rarely seen in the feces and are mostly seen during a colonoscopy exam. Most of the time as an incidental finding.

Trichuris trichiura eggs are characteristically barrel or football shaped with prominent polar plugs at both ends. The eggs will also take up Lugol’s iodine easily and will therefore appear a deep brown color. They are 30-45u in length by 22-23u wide. When passed the eggs are unembryonated. Embryonated eggs are only seen in the soil because it takes about two to three weeks for the eggs to develop from the unembryonated to the embryonated stage.

Trichuris trichiura adult worms have a characteristic bull-whip like appearance with females being about 35-50u long and males 30-45u long.

Even though the eggs are easily identifiable there are a few considerations to take into account that may result in missing or misidentifying the parasite. The first is that the eggs are shed intermittently and in low numbers especially in light infections and may be missed. Secondly, the dog whipworm (Trichuris vulpis) may be misidentified as Trichuris trichiura. However the eggs of Trichuris vulpis are significantly larger at 72-90u by 32-40u, and the eggs are more barrel shaped.


Adult Trichuris trichiura worm removed during colonoscopy – Photo by W. Vientos
Trichuris egg in Lugols iodine – note the distinctive polar plugs and the way it takes up the Luogols iodine so that it is dark brown – photo by W. Vientos
Close-up of Trichuris egg under high oil immersion magnification. Note the plugs at both ends, the thick shell wall, the embryonic contents visible inside, and how intense the egg picks up the Lugol’s Iodine in this formalin concentrate – Photo by W. Vientos