Epidemiology of malaria in the Amazon basin of Ecuador

Malaria is reemerging in most endemic countries of South America. In Ecuador, malaria is endemic on the Pacific coast, in the inter-Andean valleys, and in the Amazon River basin. In the Lower-Napo region of northeastern Ecuador, malaria was considered eliminated in the 1970s, but the disease has reemerged in recent years. Three organizations are involved in malaria-related work in the area, but they are not coordinating their efforts. This study was designed to describe the epidemiology of malaria incidence in the Lower-Napo region for the period of January 1992 through December 1995, and to determine the extent of seasonality in transmission in the area. To determine malaria incidence, data were collected for that 4-year period from the records of the three malaria-related organizations: the office of the National Center for Malaria Eradication (NCME) in the town of Coca, the district hospital in Nuevo Rocafuerte (DHNR), and an association of community health workers called Sandi Yura. Data on climatic conditions for the same period were collected from the Ecuadorian Air Force and civil aviation authorities. During the 1992-1995 period, NCME diagnosed a total of 773 malaria cases, DHNR diagnosed 485, and Sandi Yura clinically diagnosed 859. For the 4-year period, an annual parasite index of 40.4 was found with the DHNR data, 35.8 with the Sandi Yura data, and 6.2 with the NCME data. The predominant parasite in the area was Plasmodium vivax (92% of all the cases). Twenty-eight percent of the infected persons were under 10 years old. No discernible differences between the genders were found. There was also no seasonal variation among the cases. Further research is needed in order to confirm these findings and better understand malaria transmission in the region. The study highlights the need for a closer coordination among the area's malaria-control organizations so as to have an improved understanding of malaria epidemiology and to design and implement effective control strategies.