Organism The nematode Trichuris tri-chiura, which has a characteristic egg (elongated and with a knob at each end) when seen in faecal specimens (see Fig. 9.1).
Clinical features A large number of people carry this infection quite asymptomatically, but it has been realized that the debilitating effect of this infection, especially in children in developing countries, can be quite considerable. This is especially the case when tri-churiasis is associated with other common infections, the combined effect leading to much ill health. When there are over 16,000 eggs/g of faeces, a chronic bloody diarrhoea, anaemia, rectal prolapse and occasionally, appendicitis can result. These infections tend to occur when the child eats earth (pica), which can be a result of iron deficiency. Heavy infections are probably potentiated by nutritional deficiencies, especially of zinc.
Diagnosis The characteristic egg is easily seen in a fresh faecal specimen (Fig. 9.1).
Transmission The egg develops in the soil and when swallowed directly or as a contaminant of food, it changes into an adult in the caecum. Eggs are most commonly carried on the fingers or swallowed when the fingers are licked. The soil is readily contaminated from indiscriminate defecation, especially where the faeces are not buried or a latrine used. Villages often have traditional places for defecation, thereby increasing the potential for infection than when such customary places are not the rule.
Incubation period It takes 2-3 months for eggs to be found in the faeces after eggs are first swallowed, with symptoms occurring about 1 month after ingestion.
Period of communicability Persons can remain infected for several years if not treated, continually contaminating the environment if they have poor defecating practices.
Occurrence and distribution It is a very common parasite (perhaps 540 million people are infected) and causes far more disability than previously thought to be the case (see Table 1.1). Most of the infection with debilitating consequences occurs in developing countries, but the parasite is found worldwide.
Control and prevention Washing hands before having food and the careful preparation of food are the main methods of control. Vegetables and root crops, in particular, must be washed carefully to remove all earth. Parents should discourage their children from eating earth and have anaemia treated with iron supplementation. Proper sanitation should be installed to prevent soil contamination.
Treatment is with mebendazole or albendazole. (See under hookworm for dosage.)
Surveillance Routine stool investigation of children admitted to hospital will show a number of nematode infections.
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