Joint malaria surveys lead towards improved cross-border cooperation between Savannakhet province, Laos and Quang Tri province, Vietnam

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Abstract

Background

In Savannakhet province, Laos and Quang Tri province, Vietnam, malaria is still an important health problem and most cases are found in the mountainous, forested border areas where ethnic minority groups live. The objectives of this study were to obtain a better joint understanding of the malaria situation along the border and, on the basis of that, improve malaria control methods through better cooperation between the two countries.

Methods

Fourteen villages in Savannakhet and 22 villages in Quang Tri were randomly selected within 5 km from the border where a blood survey for microscopic diagnosis (n = 1256 and n = 1803, respectively), household interviews (n = 400, both sides) and vector surveys were conducted between August and October 2010. Satellite images were used to examine the forest density around the study villages.

Results

Malaria prevalence was significantly higher in Laos (5.2%) than in Vietnam (1.8%) and many other differences were found over the short distance across the border. Bed net coverage was high (> 90%) in both Laos and Vietnam but, while in Laos more than 60% of the nets were long-lasting insecticide-treated, Vietnam used indoor residual spraying in this area and the nets were untreated. Anopheles mosquitoes were more abundant in Laos than in Vietnam, especially many Anopheles dirus were captured in indoor light traps while none were collected in Vietnam. The forest cover was higher around the Lao than the Vietnamese villages. After this study routine exchange of malaria surveillance data was institutionalized and for the first time indoor residual spraying was applied in some Lao villages.

Conclusions

The abundance of indoor-collected An. dirus on the Laos side raises doubts about the effectiveness of a sole reliance on long-lasting insecticide-treated nets in this area. Next to strengthening the early detection, correct diagnosis and prompt, adequate treatment of malaria infections, it is recommended to test focal indoor residual spraying and the promotion of insect repellent use in the early evening as additional vector interventions. Conducting joint malaria surveys by staff of two countries proved to be effective in stimulating better collaboration and improve cross-border malaria control.

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Most cited references 16

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Malaria transmission and major malaria vectors in different geographical areas of Southeast Asia.

H D Trung, W. Van Bortel, T Sochantha … (2004)

During the last decade, major progress in malaria control has been achieved in Vietnam, Laos and Cambodia. However, malaria is still a potentially fatal disease in some hilly-forested areas and continues to be endemic in a few coastal foci. To estimate the risk that stems from the major vectors after a decade of intensive malaria control, an entomological study based on human landing collections was conducted between April 1998 and November 2000 in six study villages (four in Vietnam, one in Cambodia and one in Laos) located in different physio-geographical areas. Five villages were selected in places where new cases of malaria still occurred. In the sixth village, in the northern hilly area of Vietnam, no case of malaria was detected during the past 3 years. In three study villages of the hilly forested areas of Cambodia and central Vietnam, Anopheles dirus A still played an important role in malaria transmission and maintain perennial transmission inside the villages despite its low density. Anopheles minimus A was found in all study villages except in the southern coastal village of Vietnam. Its role in malaria transmission, however, varied between localities and surveys. In one study village of central Vietnam it was almost absent (one specimen collected over 480 man nights), and in another village sporozoite positive specimens (2.8%) were only observed during the first two surveys whereas this species disappeared from the collections from November 1998 onwards (six surveys: 360 man nights). In the northern study site An. minimus A and C were found in all collections, but no local malaria transmission occurred. However, the constant presence of these two species associated with a high longevity (parous rate up around 80% and 65%, respectively), suggests that transmission can occur at almost any time if parasite reservoirs are reintroduced in the area. The proper management of malaria cases and population movement is, therefore, important to prevent outbreaks and the reintroduction of malaria in northern Vietnam. In the study site of the Mekong delta, An. sundaicus occurred at high densities (up to 190 bites/man/night). The recent changes in land use from rice cultivation to shrimp farming probably explains the increase of this brackish water breeding species during the study period. However, none of the 11,002 specimens was positive for Plasmodium circumsporozoite protein (CSP). The relative low survival rate as estimated by the parous rate (around 47%) may reflect its low vectorial status that could explain the very low malaria incidence (1.9 case/100 persons/year) in this study site. A calculated sporozoite rate of maximum 1/300,000 is enough to explain this low malaria incidence. Despite the successes in malaria control, the vector An. dirus A continues to play an important role in malaria transmission, whereas An. minimus A showed temporal and spatial variation in its role as vector. The role of An. sundaicus as vector could not be confirmed because of the low incidence in the coastal study village. Other Anopheles species may be locally involved, but in the five study villages where malaria is still present they probably do not contribute significantly to malaria transmission. The study also points towards the fact that in Southeast Asia it will become increasingly difficult to incriminate Anopheles species in malaria transmission while the risk for malaria transmission still persist.

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Malaria trends and challenges in the Greater Mekong Subregion.

T. Dai, ShaoHong Lu, John Patrick Ehrenberg … (2009)

This report provides an overview of the epidemiological patterns of malaria in the Greater Mekong Subregion (GMS) from 1998 to 2007, and highlights critical challenges facing national malaria control programs and partners in effort to build on their successes as they move towards malaria pre-elimination and elimination as a programmatic goal. Epidemiological data provided by malaria programs show a drastic decline in malaria deaths and confirmed malaria positive cases over the last 10 years in the GMS. More than half of confirmed malaria cases and deaths recorded in the GMS occur in Myanmar, however, reporting methods and data management are not comparable between countries despite effort made by WHO to harmonize data collection, analysis and reporting among WHO Member States. Malaria is concentrated in forested/forest-fringe areas of the region mainly along international borders providing strong rationale to develop harmonized cross-border pre-elimination programs in conjunction with national efforts. Across the Mekong Region, the declining efficacy of recommended first-line antimalarials, eg artemisinin-based combination therapies (ACTs) against falciparum malaria on the Cambodia-Thailand border, the prevalence of counterfeit and substandard antimalarial drugs, the lack of health services in general and malaria services in particular in remote settings, and the lack of information and services targeting migrants and mobile population present important barriers to reach or maintain malaria pre-elimination programmatic goals. Strengthening networking between research institutions and non-government organizations will increase knowledge-based decision and action.

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Large-scale malaria survey in Cambodia: Novel insights on species distribution and risk factors

Sandra Incardona, Sirenda Vong, Lim Chiv … (2007)

Background In Cambodia, estimates of the malaria burden rely on a public health information system that does not record cases occurring among remote populations, neither malaria cases treated in the private sector nor asymptomatic carriers. A global estimate of the current malaria situation and associated risk factors is, therefore, still lacking. Methods A large cross-sectional survey was carried out in three areas of multidrug resistant malaria in Cambodia, enrolling 11,652 individuals. Fever and splenomegaly were recorded. Malaria prevalence, parasite densities and spatial distribution of infection were determined to identify parasitological profiles and the associated risk factors useful for improving malaria control programmes in the country. Results Malaria prevalence was 3.0%, 7.0% and 12.3% in Sampovloun, Koh Kong and Preah Vihear areas. Prevalences and Plasmodium species were heterogeneously distributed, with higher Plasmodium vivax rates in areas of low transmission. Malaria-attributable fevers accounted only for 10–33% of malaria cases, and 23–33% of parasite carriers were febrile. Multivariate multilevel regression analysis identified adults and males, mostly involved in forest activities, as high risk groups in Sampovloun, with additional risks for children in forest-fringe villages in the other areas along with an increased risk with distance from health facilities. Conclusion These observations point to a more complex malaria situation than suspected from official reports. A large asymptomatic reservoir was observed. The rates of P. vivax infections were higher than recorded in several areas. In remote areas, malaria prevalence was high. This indicates that additional health facilities should be implemented in areas at higher risk, such as remote rural and forested parts of the country, which are not adequately served by health services. Precise malaria risk mapping all over the country is needed to assess the extensive geographical heterogeneity of malaria endemicity and risk populations, so that current malaria control measures can be reinforced accordingly.

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Author and article information

Journal

Journal ID (nlm-ta): Malar J

Journal ID (iso-abbrev): Malar. J

Title: Malaria Journal

Publisher: BioMed Central

ISSN (Electronic): 1475-2875

Publication date Collection: 2012

Publication date (Electronic): 3 August 2012

Volume: 11

Page: 262

Affiliations

[1 ]Savannakhet Provincial Malaria Station, Savannakhet, Laos

[2 ]Quang Tri Province Preventive Medicine Center, Quang Tri, Vietnam

[3 ]Medical Committee Netherlands-Vietnam, Nha Trang, Vietnam

[4 ]Department of Parasitology and International Health, Graduate School of Medicine, University of the Ryukyus, Okinawa, Japan

[5 ]Research Institute for Humanity and Nature, Kyoto, Japan

[6 ]Savannakhet Provincial Health Department, Savannakhet, Laos

[7 ]Graduate School of International Health Development, Nagasaki University, Nagasaki, Japan

[8 ]Department of International Medical Cooperation, National Center for Global Health and Medicine, Tokyo, Japan

Article

Publisher ID: 1475-2875-11-262

DOI: 10.1186/1475-2875-11-262

PMC ID: 3483260

PubMed ID: 22862795

SO-VID: 138fc558-a216-42b7-807b-e39180e91c93

License:

This is an Open Access article distributed under the terms of the Creative Commons Attribution License ( http://creativecommons.org/licenses/by/2.0), which permits unrestricted use, distribution, and reproduction in any medium, provided the original work is properly cited.

Joint malaria surveys lead towards improved cross-border cooperation between Savannakhet province, Laos and Quang Tri province, Vietnam

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Most cited references 16

Malaria transmission and major malaria vectors in different geographical areas of Southeast Asia.

Malaria trends and challenges in the Greater Mekong Subregion.

Large-scale malaria survey in Cambodia: Novel insights on species distribution and risk factors

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