Application of seroepidemiology in identification of local foci in a malarious community in Palawan, The Philippines.

The value of seroepidemiology in malaria control programs has long been recognized, but its use in such situations has been limited. We therefore conducted a seroepidemiologic study in a frontier community on Palawan Island, The Philippines, an area where malaria is highly endemic. The first serologic survey was done at the end of the rainy season and the second was done during the dry season. The sera were examined using an indirect fluorescent antibody test. There was a significant difference in the geometric mean reciprocal titer (GMRT) during the rainy season as compared with the GMRT during the dry season. There were seasonal changes in the distribution of high- and low-titer responses, which is suggestive of the occurrence of recent past malaria epidemics. The differences in the geographic distribution of high and low titers were indicative of permanent foci of malaria transmission in this community. Results of a parallel parasitologic study were consistent with those of the serologic study. These findings may be of practical value not only in the proper reorientation of the local malaria control program, but of those of other endemic countries as well.