Epidemiology of forest malaria in central Vietnam: a large scale cross-sectional survey.
In Vietnam, a large proportion of all malaria cases and deaths occurs in the central mountainous and forested part of the country. Indeed, forest malaria, despite intensive control activities, is still a major problem which raises several questions about its dynamics.A large-scale malaria morbidity survey to measure malaria endemicity and identify important risk factors was carried out in 43 villages situated in a forested area of Ninh Thuan province, south central Vietnam. Four thousand three hundred and six randomly selected individuals, aged 10-60 years, participated in the survey. Rag Lays (86%), traditionally living in the forest and practising "slash and burn" cultivation represented the most common ethnic group. The overall parasite rate was 13.3% (range [0-42.3] while Plasmodium falciparum seroprevalence was 25.5% (range [2.1-75.6]). Mapping of these two variables showed a patchy distribution, suggesting that risk factors other than remoteness and forest proximity modulated the human-vector interactions. This was confirmed by the results of the multivariate-adjusted analysis, showing that forest work was a significant risk factor for malaria infection, further increased by staying in the forest overnight (OR= 2.86; 95%CI [1.62; 5.07]). Rag Lays had a higher risk of malaria infection, which inversely related to education level and socio-economic status. Women were less at risk than men (OR = 0.71; 95%CI [0.59; 0.86]), a possible consequence of different behaviour. This study confirms that malaria endemicity is still relatively high in this area and that the dynamics of transmission is constantly modulated by the behaviour of both humans and vectors. A well-targeted intervention reducing the "vector/forest worker" interaction, based on long-lasting insecticidal material, could be appropriate in this environment.
Erhart
Annette
A
Prince Leopold Institute of Tropical Medicine, Nationalestraat 155, 2000 Antwerp, Belgium. aerhart@itg.be
Ngo
Duc Thang
DT
Phan
Van Ky
VK
Ta
Thi Tinh
TT
Van Overmeir
Chantal
C
Speybroeck
Niko
N
Obsomer
Valerie
V
Le
Xuan Hung
XH
Le
Khanh Thuan
KT
Coosemans
Marc
M
D'alessandro
Umberto
U
D000293:Adolescent; D000328:Adult; D000818:Animals; D000913:Antibodies, Protozoan / Q000097:blood; D002648:Child; D003430:Cross-Sectional Studies; D003710:Demography; D019353:Endemic Diseases / Q000517:prevention & control / Q000706:statistics & numerical data; D005260:Female; D019084:Fluorescent Antibody Technique, Indirect; D006801:Humans; D016015:Logistic Models; D008288:Malaria / Q000453:epidemiology* / Q000517:prevention & control; D008297:Male; D008875:Middle Aged; D009017:Morbidity; D010963:Plasmodium falciparum / Q000276:immunology / Q000302:isolation & purification; D011891:Rain; D012307:Risk Factors; D016036:Seroepidemiologic Studies; D014197:Trees; D014744:Vietnam / Q000453:epidemiology
D000913:Antibodies, Protozoan