Mekong malaria. II. Update of malaria, multi-drug resistance and economic development in the Mekong region of Southeast Asia.

In an expansion of the first Mekong Malaria monograph published in 1999, this second monograph updates the malaria database in the countries comprising the Mekong region of Southeast Asia. The update adds another 3 years' information to cover cumulative data from the 6 Mekong countries (Cambodia, China/Yunnan, Lao PDR, Myanmar, Thailand, Viet Nam) for the six-year period 1999-2001. The objective is to generate a more comprehensive regional perspective in what is a global epicenter of drug resistant falciparum malaria, in order to improve malaria control on a regional basis in the context of social and economic change. The further application of geographical information systems (GIS) to the analysis has underscored the overall asymmetry of disease patterns in the region, with increased emphasis on population mobility in disease spread. Of great importance is the continuing expansion of resistance of P. falciparum to antimalarial drugs in common use and the increasing employment of differing drug combinations as a result. The variation in drug policy among the 6 countries still represents a major obstacle to the institution of region-wide restrictions on drug misuse. An important step forward has been the establishment of 36 sentinel sites throughout the 6 countries, with the objective of standardizing the drug monitoring process; while not all sentinel sites are fully operational yet, the initial implementation has already given encouraging results in relation to disease monitoring. Some decreases in malaria mortality have been recorded. The disease patterns delineated by GIS are particularly instructive when focused on inter-country distribution, which is where more local collaborative effort can be made to rationalize resource utilization and policy development. Placing disease data in the context of socio-economic trends within and between countries serves to further identify the needs and the potential for placing emphasis on resource rationalization on a regional basis. Despite the difficulties, the 6-year time frame represented in this monograph gives confidence that the now well established collaboration is becoming a major factor in improving malaria control on a regional basis and hopefully redressing to a substantial degree the key problem of spread of drug resistance regionally and eventually globally.

A focus of endemic malaria in central Java.

This report describes one of the few remaining foci of endemic malaria on the island of Java, the Kokap subdistrict, near the Southcentral coast. Kokap was hypoendemic in June 1994 with prevalence of parasitemia at 0.98% (n = 10,606 of 40,246 residents). Plasmodium vivax comprised 63% of infections and P. falciparum all others. The incidence of indigenous infection during 1993 was 48 cases/1,000 person-years (p-yr), and it was relatively uniform among age groups (38 to 53/1,000 p-yr). Nine deaths due to malaria had been recorded in the past three years (8.3 deaths per 100,000 p-yr); the case fatality rate was 0.17%. Subdistricts adjoining Kokap to the north, east, and south reported incidence rates of < 2 cases/1,000 p-yr. To the west, Purworejo District had a high case incidence (11 cases/1,000 p-yr) but other districts to the west did not (< 1.2 cases/1,000 p-yr). The highest case incidence village area within Kokap (169 cases/1,000 p-yr) bordered the district of Purworejo to the west. Endemic malaria in Kokap and Purworejo coincided with where steep hills and narrow valleys dominated the terrain.

Age-specific prevalence of Plasmodium falciparum among six populations with limited histories of exposure to endemic malaria.

The age-specific prevalence of Plasmodium falciparum parasitemia among residents of six villages in northeastern Irian Jaya, Indonesia, has been measured for a period of five years. All study subjects were transmigrants from Java living in Irian Jaya for three weeks to 72 months, depending upon the village and point of measurement. Fifteen separate estimates of prevalence were obtained from 4,554 Giemsa-stained thick blood films from 91 to 701 people (mean sample size = 304) among the six villages. The prevalence of parasitemia among people who had lived in Irian Jaya for less than one year did not decrease as a function of age, except in one village at eight months. In contrast, after 16 months to two years or more of residence, the prevalence of parasitemia decreased markedly with increasing age beyond 6-10 or 11-15 years. Social, behavioral, or entomologic characteristics of these populations did not explain the decreasing prevalence of parasitemia with age. An age-dependent naturally acquired protective immunity appeared to develop in all of these villages after 1-2 years of exposure to hyperendemic malaria.

Insecticide susceptibility status of Anopheles koliensis (Diptera: Culicidae) in northeastern Irian Jaya, Indonesia.

Anopheles koliensis, an important malaria vector in the interior region of Irian Jaya, Indonesia, was evaluated for susceptibility to three different insecticide compounds using the standard World Health Organization diagnostic test kit and pretreated impregnated papers. A series of tests were conducted in Arso PIR I, a transmigrant settlement 60 km south of Jayapura, from January 1988 to May 1989. All compounds were tested at the recommended diagnostic dosage and exposure time. An. koliensis were susceptible to 1.0% fenitrothion at two hour exposure (N = 358) and 5.0% malathion at one hour exposure (N = 371) after the 24-hour holding period. Significant resistance to DDT was observed in both the An. koliensis and Culex quinquefasciatus populations. Approximately 30% of the An. koliensis population (N = 468) was resistant to 4% DDT at both one and two hour exposures. These findings indicate that routine use of DDT in Arso PIR I for indoor residual house spraying may be of limited effectiveness, in part, because of physiological resistance. However, use of an alternative insecticide will be more expensive and might prove equally ineffective because of the exophilic behavior of the species. This is the first confirmed report from repeated observations of DDT resistance in An. koliensis from Indonesia.

Malaria control program in Indonesia.

The malaria situation in Indonesia is reviewed in the major island group of Java-Bali and the remainder of the archipelago called the Outer Islands. Based on their varying epidemiological patterns the areas for control have been stratified and efforts are directed towards the rational use of antimalarial drugs and the institution of integrated vector control ie chemical control in conjunction with biological control and environmental management. The targets of malaria control vary as well between island groups. Administrative, technical and operational constraints are identified. Drug-resistant malaria, forest-related malaria, lack of personnel, supervision and coordination, inadequate resources, and community participation are among the main issues confronting the national malaria control program. Research and training needs are emphasized in the recommendations.