There are two types of dysentery-bacillary dysentery and amoebic dysentery. Bacillary dysentery is caused by the Shigella group of organisms. These are very motile and are found in the faeces of sick persons. The bacteria thrive well in human food kept at about 37° C temperature. The temperature in tropical countries is very favourable for bacterial multiplication.
Amoebic dysentery is caused by Entamoeba histolytic. These protozoa are parasitic in man. They pass out in the stools and form cysts. Cysts are very resistant forms of the amoeba and can survive long periods of un favourable conditions. Thus infection may spread through these cysts, transmitted to the host by dirty hands, contaminated water and food. Flies are often a cause of this contamination of food as they carry the cysts.
After entry into a new host the entamoeba multiply by division and produce the symptoms of the disease. The incubation period for bacillary dysentery is 2-3 days while that for amoebic dysentery varies from a week to several months.
The disease spreads when the organism finds entry into the body through contaminated food and water. The disease also spreads through carriers. It is characterised by severe gripping pain in the lower abdomen. There is inflammation and probable un creation of the large intestine. There will be diarrhea and fever. The stools passed are fluid and contain mucus. In severe cases sick person also pass blood. In acute cases only mucus and blood may be passed and the patient becomes weak. If neglected, the disease becomes chronic and difficult to treat.
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A high level of personal cleanliness and environmental sanitation help greatly in the prevention of this disease. Sanitary disposal of wastes and safe handling of food are essential. Disease carriers should not be allowed to handle food. Prophylactic vaccine for bacillary dysentery has not proved very effective.