Population movement and malaria persistence in Rameswaram Island.

During 1982-84 the Vector Control Research Center (VCRC) of the Indian Council for Medical Research (ICMR) at Pondicherry studied the role of population movement in the persistence of malaria transmission in Rameswaram Island Tamil Nadu between mainland India and Sri Lanka. While the island supports a population of 56000 mostly fishermen there is also a periodic back and forth migration of fishermen between mainland villages and Rameswaram. This population movement greatly contributes to the high prevalence of malaria in both areas since fishermen can be either donor or recipient of malaria in either place. The VCRC monitered and recorded the movement of fishermen in various seasonal camps by questioning them and by the VCRC staff accompanying them when possible. In 9 fishing camps 412 of 1098 families had migrated from mainland villages; 686 families had migrated from villages within Rameswaram Island. A mass blood survey found 138 of 4073 individuals examined positive for malaria; 107 of 680 fever cases examined were positive for malaria. Mosquito collections the lack of permanent treatment facilities for the transient population and ecological factors indicate a high receptivity for malaria on Rameswaram Island. With the island attracting between 1000-4000 tourists daily and over 200000 travelers annually between India and Sri Lanka evidence exists for considerable danger from the importation of chloroquinine resistant malaria strains into Rameswaram. Adequate attention to human ecology will be needed for malaria control in this area.