Period of communicability Cyst passing can continue for many years.
Occurrence and distribution Amoebiasis is a disease of poor hygiene, more commonly found in cooler environments than hot ones. In the tropics, it predominantly occurs in highland areas or where there is a large temperature fluctuation. It is an infection of adult life and if the period of residence in an endemic area is long, there is greater chance of becoming infected.
Control and prevention is by personal hygiene, food hygiene and the proper provision of water and sanitation. Sand filtration, especially if it is combined with alum floc-culation, removes cysts from water supplies. A high concentration of chlorine is required to kill cysts (3.5 ppm residual) although they are more sensitive to iodine.
Treatment of all stages of the disease is by metronidazole 2.4 g single dose for 3 days or
2 g daily for 5 days or by other derivatives of the 5-nitroimidazole group of compounds (tinidazole, ornidazole and nimorazole). Cyst passers can be given diloxanide furoate (Furomate), 500 mg 8-hourly for 10 days.
Surveillance Routine stool specimens should be examined for amoebic cysts. Cysts of E. histolytica can be differentiated from other cysts by size and number of nuclei (Fig. 8.3).
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