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Intestinal Nematodes: Soil-Transmitted Helminths (STH) 81

4 Embryonated eggs are ingested
i
3 Advanced cleavage
i = Infective Stage
d = Diagnostic Stage

5

Larvae hatch
in small intestine

2
2-cell stage

d
1 Unembryonated eggs
passed in faeces.

6 Adults in caecum

Fig. 10.2 Life cycle of Trichuris trichiura (Reproduced from https://www.cdc.gov/dpdx/trichu-
riasis/index.html)

Humans acquire infection by ingesting the embryonated eggs. (5) The egg hatches
into larva in the intestine. (6) Larva matures into adult in about 2–3 months in the
large intestine (caecum). Female worm produces eggs which are passed out in the
faeces.
Human is its natural host. No intermediate host is required. The embryonated
eggs are the infective stage to human.

Pathogenesis and Clinical Features
Infection with T. trichiura (trichuriasis) is usually asymptomatic, except in heavy
infection. Blood may ooze out at the site of attachment of the anterior part of the