Malaria in a rural area of eastern Thailand: baseline epidemiological studies at Bo Thong

Malaria is still a serious health problem in Thailand. Present attempts at controlling the disease by drug treatment and other means remain unsatisfactory. Thus, development of vaccination against malaria is a major research goal of malaria immunology. The objective of this study was to acquire epidemiological base line data for subsequent vaccine trials. A cross-sectional descriptive survey was conducted among 253 local inhabitants during the beginning of the transmission season in July 1989 at Bo Thong District, Chonburi Province, Eastern Thailand where malaria transmission was likely to be moderately high. Following the cross-sectional survey weekly morbidity surveillance was started to detect new cases of malaria by using active and passive case detection at the district hospital, local health centers and at neighboring malaria clinics. Fifty-four percent of the population were male and forty-six percent female: nearly a half (48.3%) were under the age of 15 and 17% under the age of 5 years. Eighty percent of the adults were married. Seventy percent of the subjects interviewed gave a history of malarial illness in the past. Malaria, malnutrition, anemia abnormal hemoglobin diseases and parasitic infestations were the main health problems in the study area. The annual parasite incidence of malaria was 169.4/1,000 population and 77% of parasitemic individuals were asymptomatic, indicating the existence of a semi-immune condition among these subjects. Antibody level to crude parasite antigen increased with age. It is hoped that the information obtained from these field studies may be useful in malaria vaccine trials in the near future.