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The incidence of malaria in travellers to South-East Asia: is local malaria transmission a useful risk indicator?

Behrens RH, Carroll B, Hellgren U, Visser LG, Siikamäki H, Vestergaard LS, Calleri G, Jänisch T, Myrvang B, Gascon J, Hatz C - Malar. J. (2010)

Bottom Line: The remaining six countries rates were < 1 case per 100,000 visits.The number of visitors arriving from source countries increased by 60% from 8.5 Million to 13.6 million over the 6 years.Policy needs to be adjusted regularly to reflect the changing risk.

View Article: PubMed Central - HTML - PubMed

Affiliation: Travel Clinic, Hospital for Tropical Diseases, Mortimer Market, London, WC1E 6JB, UK. ron.behrens@lshtm.ac.uk

ABSTRACT

Background: The presence of ongoing local malaria transmission, identified though local surveillance and reported to regional WHO offices, by S-E Asian countries, forms the basis of national and international chemoprophylaxis recommendations in western countries. The study was designed to examine whether the strategy of using malaria transmission in a local population was an accurate estimate of the malaria threat faced by travellers and a correlate of malaria in returning travellers.

Methods: Malaria endemicity was described from distribution and intensity in the local populations of ten S-E Asian destination countries over the period 2003-2008 from regionally reported cases to WHO offices. Travel acquired malaria was collated from malaria surveillance reports from the USA and 12 European countries over the same period. The numbers of travellers visiting the destination countries was based on immigration and tourism statistics collected on entry of tourists to the destination countries.

Results: In the destination countries, mean malaria rates in endemic countries ranged between 0.01 in Korea to 4:1000 population per year in Lao PDR, with higher regional rates in a number of countries. Malaria cases imported into the 13 countries declined by 47% from 140 cases in 2003 to 66 in 2008. A total of 608 cases (27.3% Plasmodium falciparum (Pf)) were reported over the six years, the largest number acquired in Indonesia, Thailand and Korea. Four countries had an incidence > 1 case per 100,000 traveller visits; Burma (Myanmar), Indonesia, Cambodia and Laos (range 1 to 11.8-case per 100,000 visits). The remaining six countries rates were < 1 case per 100,000 visits. The number of visitors arriving from source countries increased by 60% from 8.5 Million to 13.6 million over the 6 years.

Conclusion: The intensity of malaria transmission particularly sub-national activity did not correlate with the risk of travellers acquiring malaria in the large numbers of arriving visitors. It is proposed to use a threshold incidence of > 1 case per 100,000 visits to consider targeted malaria prophylaxis recommendations to minimize use of chemoprophylaxis for low risk exposure during visits to S-E Asia. Policy needs to be adjusted regularly to reflect the changing risk.

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The trend of all imported malaria from, and travel to S-E Asia between 2003 and 2008. The trend of imported malaria and numbers of visitors to the 13 countries over 6 years. Malaria cases fell by 47% while visits to the region increased by 60%
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Figure 1: The trend of all imported malaria from, and travel to S-E Asia between 2003 and 2008. The trend of imported malaria and numbers of visitors to the 13 countries over 6 years. Malaria cases fell by 47% while visits to the region increased by 60%

Mentions: Over the six-year period a total of 608 cases of malaria were included in the study reported by the source countries (Table 3). Table 4 details the malaria species with, P. falciparum (166), P. vivax (349), Plasmodium ovale (11), Plasmodium malariae (5) and Plasmodium knowlesi (3) and not-specified (65). The total number of malaria cases range from 140 cases in 2003 to 66 cases in 2008 (47% reduction) as reported by source country surveillance bodies, detailed in Table 5. Plasmodium falciparum constituted 30.3% of identified Plasmodium species during the study period. Table 6 shows all the malaria cases by county of probable acquisition by year reported. The national mean endemic rates of malaria transmission are detailed in Table 2. This also shows the range of rates from lowest to highest in endemic provinces or regions where populations are living under risk of malaria. Figure 1 shows the trend of imported malaria during the study period.


The incidence of malaria in travellers to South-East Asia: is local malaria transmission a useful risk indicator?

Behrens RH, Carroll B, Hellgren U, Visser LG, Siikamäki H, Vestergaard LS, Calleri G, Jänisch T, Myrvang B, Gascon J, Hatz C - Malar. J. (2010)

The trend of all imported malaria from, and travel to S-E Asia between 2003 and 2008. The trend of imported malaria and numbers of visitors to the 13 countries over 6 years. Malaria cases fell by 47% while visits to the region increased by 60%
© Copyright Policy - open-access
Related In: Results  -  Collection

License
Show All Figures
getmorefigures.php?uid=PMC2959067&req=5

Figure 1: The trend of all imported malaria from, and travel to S-E Asia between 2003 and 2008. The trend of imported malaria and numbers of visitors to the 13 countries over 6 years. Malaria cases fell by 47% while visits to the region increased by 60%
Mentions: Over the six-year period a total of 608 cases of malaria were included in the study reported by the source countries (Table 3). Table 4 details the malaria species with, P. falciparum (166), P. vivax (349), Plasmodium ovale (11), Plasmodium malariae (5) and Plasmodium knowlesi (3) and not-specified (65). The total number of malaria cases range from 140 cases in 2003 to 66 cases in 2008 (47% reduction) as reported by source country surveillance bodies, detailed in Table 5. Plasmodium falciparum constituted 30.3% of identified Plasmodium species during the study period. Table 6 shows all the malaria cases by county of probable acquisition by year reported. The national mean endemic rates of malaria transmission are detailed in Table 2. This also shows the range of rates from lowest to highest in endemic provinces or regions where populations are living under risk of malaria. Figure 1 shows the trend of imported malaria during the study period.

Bottom Line: The remaining six countries rates were < 1 case per 100,000 visits.The number of visitors arriving from source countries increased by 60% from 8.5 Million to 13.6 million over the 6 years.Policy needs to be adjusted regularly to reflect the changing risk.

View Article: PubMed Central - HTML - PubMed

Affiliation: Travel Clinic, Hospital for Tropical Diseases, Mortimer Market, London, WC1E 6JB, UK. ron.behrens@lshtm.ac.uk

ABSTRACT

Background: The presence of ongoing local malaria transmission, identified though local surveillance and reported to regional WHO offices, by S-E Asian countries, forms the basis of national and international chemoprophylaxis recommendations in western countries. The study was designed to examine whether the strategy of using malaria transmission in a local population was an accurate estimate of the malaria threat faced by travellers and a correlate of malaria in returning travellers.

Methods: Malaria endemicity was described from distribution and intensity in the local populations of ten S-E Asian destination countries over the period 2003-2008 from regionally reported cases to WHO offices. Travel acquired malaria was collated from malaria surveillance reports from the USA and 12 European countries over the same period. The numbers of travellers visiting the destination countries was based on immigration and tourism statistics collected on entry of tourists to the destination countries.

Results: In the destination countries, mean malaria rates in endemic countries ranged between 0.01 in Korea to 4:1000 population per year in Lao PDR, with higher regional rates in a number of countries. Malaria cases imported into the 13 countries declined by 47% from 140 cases in 2003 to 66 in 2008. A total of 608 cases (27.3% Plasmodium falciparum (Pf)) were reported over the six years, the largest number acquired in Indonesia, Thailand and Korea. Four countries had an incidence > 1 case per 100,000 traveller visits; Burma (Myanmar), Indonesia, Cambodia and Laos (range 1 to 11.8-case per 100,000 visits). The remaining six countries rates were < 1 case per 100,000 visits. The number of visitors arriving from source countries increased by 60% from 8.5 Million to 13.6 million over the 6 years.

Conclusion: The intensity of malaria transmission particularly sub-national activity did not correlate with the risk of travellers acquiring malaria in the large numbers of arriving visitors. It is proposed to use a threshold incidence of > 1 case per 100,000 visits to consider targeted malaria prophylaxis recommendations to minimize use of chemoprophylaxis for low risk exposure during visits to S-E Asia. Policy needs to be adjusted regularly to reflect the changing risk.

Show MeSH
Related in: MedlinePlus