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The term amoebiasis has been defined by WHO as condition harbouring the protozoan parasite ‘Entamoeba histolytica’ with or without clinical manifestations. Less than ten per cent of the infected persons are known to suffer from symptomatic disease. The symptomatic has been further divided into intestinal and extra-intestinal. Intestinal disease varies from mild abdominal discomfort and diarrhoea to acute dysentery. Extra-intestinal disease includes involvement of liver, lungs, brain, spleen, skin etc. amoebiasis is a lethal disease carrying substantial morbidity and mortality.
Epidemiology Determinants:
Agent Factors:
Agent: Amoebiasis is caused by Entamoeba histolytica. The organism is found in two forms-vegetative and cystic. Vegetative forms are not important in transmitting the disease but the cystic forms are infective and viable for several days in feces, water, soil in the presence of moisture and low temperature. The cysts are destroyed by dryness, heat or freezing temperature.
Reservoir of Infection: man is the only known reservoir of infection and immediate source of infection being feces containing cysts. Most individuals infected with the parasite remain symptom free and are healthy carriers. The greatest risk is if the carriers are engaged in preparation and handling of food.
Period of Communiacbility: as long as cysts are excreted, the period may be several years if cases are unrecognized and untreated.
Host Factors:
Age and Sex: the disease occurs at any age and both sexes. It is a household infection. When an individual in the family is treated, others may also be affected.
Environmental Factors:
Amoebiasis is more closely related to poor sanitation and socio-economic status rather than to climate. The use of night soil for agricultural purpose increases the spread of the disease. sewage seeping into drinking water supply can lead to epidemic outbreaks.
Mode of Transmission:
- Fecal-oral route: through the intake of contaminated food and water. Vegetables eaten raw, grown with the use of sewage water for irrigation, are the conveyers of infection. The cysts found in hands and under finger nails may lead to direct hand to mouth transmission.
- Sexual transmission: by oral-rectal contact especially among male homosexuals.
- Vectors: vectors such as flies, cockroaches and rodents are capable of carrying cysts and contaminating food and drink.
Incubation Period: about 2 to 4 weeks or longer.
Prevention and Control:
- Primary prevention: these center around preventing contamination of water, food, vegetables and fruits with human feces.
- Sanitation: safe disposal of human excreta with sanitary practice of washing hands.
- Water supply: the protection of water supplies from fecal contamination is equally important. Sand filters are effective in removing amoebic cysts. Water filteration and boiling are effective compared to chemical treatment of water.
- Food hygiene: environmental measures should also include keeping food and drink away from fecal contamination. Uncooked vegetables and fruits can be disinfected with vinegar. Food handlers are predominant carries and transmitting agents, they should be educated in hygiene practices.
- Health education: health education of the public goes a long way in preventing and controlling the disease.
- Secondary prevention:
- Early diagnosis
- Treatment
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