PREVENTION AND CONTROL OF CHOLERA

INTRODUCTION

Cholera is an acute dehydrating diarrhea along with rice watery or colourless  stool as a consequence of vibrio cholera or vibrio El Tor stains. Mortality is more in vibrio cholera and morbidity and  carrier state is more in El Tor. It was spread over vast areas of world in the past and the most important epidemic centre in the world was Bengal in India from where the pandemics had, and also important centers are central India and south Tamilnadu and Uttarpradesh and deltas of main rivers in India, so that India was known as home of cholera. There are also endemic areas in China Yangtse valley and in Burma and Philippines. It increases with the onset of monsoon and decreases rapidly after monsoon. Places of pilgrimage are the main epidemic centers for its dispersion all over the countries. Pandemics and epidemics follow the routes of travel.

Cholera EL Tor stain

A research worker in 1905 on the shores of Red sea isolated peculiar strains of from the bodies of pilgrims of from mecca, who had shown no signs and symptoms of cholera, but shown in laboratory just reacted like vibrio cholera bacillus except that it produced a haemolysin. Because the pilgrims had not really seen died of cholera. Thus it was thought that vibrio E Tor was not a disease producing bacteria till it was proved and established in Celebes causing a severe disease exactly like cholera. The infection remained and confined for a long time to small areas of the island of Celebes till 1961 and it attacked many countries in pacific region and in south east Asia from where cholera had disappeared, encroaching upon the traditional areas of classified cholera. During 1955 El Tor cholera spread in many countries and epidemics broke out in India, Nepal, Pakistan,etc, and question raised whether the cholera El Tor is a variation of classical cholera or is a different disease from practical point of view been settled in 1962 by WHO research group on cholera. The illness caused by the El Tor vibrio is indistinguishable from that caused by the vibrio classical cholera. It is, therefore, now regarded necessarily identical with classical cholera and must be treated as such and international health regulations also redefined cholera to include cholera El Tor. Man is the reservoir of infection. 

Source of infection

Cases suffering from cholera and polluting water, food, etc, are the immediate source of infection. Route and mode of transmission are infection by vibrio cholera by ingestion and most common vehicle of infection being water.Organism of cholera can survive in water with saline and organic contents for a long time. Mild cases cholera defecating daily on the river bank or near collection of water, like ponds, for few days can start an explosive out break of cholera amongst those who drink this water. Vegetables and fruits washed or watered with polluted water may also carry the illness if eaten raw. If milk is diluted with polluted water can spread the disease and also flies may infect food in the presence of a cholera case close by. Mineral water is also a vehicle when it is made by unpurified water. Food contamination by polluted water, cooks and other food handlers serve as a vehicle of infection. Incubation period is less than 5 days and may be little as 12 hours. A case of cholera is ineffective during the incubation period, the course of disease and about 7 days there after.

Prevention and control

Protected water supply purified, protected, chlorinated and proper disposal of night soil and sewage. Safe and protected milk supply, protected wholesome food, and washed green raw vegetables and fruits like watermelon and absence of flies and healthy habits of eating, drinking and defecating and personal hygiene. A prohibition of employment of workers who may be carriers to handle food are the principal preventive measures. Regular preventive inoculation campaign in endemic areas of cholera. It confers protection for 3 to 6 months after which re inoculation is required. All the cholera vaccines manufactured in India contain El Tor component. International Health regulations by WHO are important to prevent the international spread of cholera which has become very easy because of the increase of speed of  modern travel. Under the regulations people coming from areas where cholera persists, must be vaccinated and are carefully screened. Preventive measures are taken on arrival from suspected areas by ships, aircraft, trans and road vehicles. A better standard of living, personal cleanliness, clean water supply, better health services permitting rapid hospitalization of cholera cases, better food hygiene and health habits are the important factors in the control of and research in cholera is to be hoped that the long standing epidemicity in India will disappear and spread of cholera El Tor will be prevented.

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