Role of migratory population in keeping up endemicity of malaria in metropolitan cities of India.

Urbanisation is rapidly taking place in India. A sizeable number of people migrate to metropolitan cities to take up casual labour jobs and settle in pockets scattered all over the city. They generally pay frequent visits to their native place with a higher malarial endemicity and are believed to be important reservoirs of infection for the native population of metropolis. To investigate this problem, a survey was conducted in 1987-88 to compare the prevalence of chronic malaria in two such pockets of migrant population with that of local population of Delhi from nearby villages. Ninetyone out of 701 (12.84 per cent) immigrants investigated had fever clinically diagnosed as malaria at the time of survey, while in the native population 45 out of 646 (6.97 per cent) had such a history. The difference is statistically significant. Splenomegaly was also significantly higher in migrants (15.41 per cent) than in natives of Delhi villages (3.10 per cent). Migrant population is not covered by active surveillance and live in poor environmental conditions conducive to mosquito breeding and malaria transmission. A special attention needs to be paid to the migratory population in the anti-malaria programme in order to control the transmission of the disease in the cities.