Epidemiology of imported malaria give support to the hypothesis of ‘long-term’ semi-immunity to malaria in sub-Saharan African migrants living in France

Pistone, Thierry; Diallo, A. N.; Méchain, Matthieu; Receveur, Marie‐Catherine; Malvy, Denis

doi:10.1016/j.tmaid.2013.08.006

Cited by 33 publications

(24 citation statements)

References 34 publications

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“…Severe P. falciparum malaria is widely reported to be less frequent in immigrants from sub-Saharan Africa than in nonimmune travellers [5][6][7][8][9][10]; however some authors have not found such differences [16]. Here, using strict definitions of severity, we did not detect any significant overall differences in severe malaria between these groups.…”

Section: Discussioncontrasting

confidence: 69%

“…in Europe, are at high risk of malaria when returning to malarious areas [4]. Nonetheless, African immigrants are generally recognized to be at lower risk of severe forms of the disease than non-immune travellers [5][6][7][8][9][10]. To what extent this protection wanes with time when people are living in non-endemic areas has not been reported.…”

Section: Introductionmentioning

confidence: 99%

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Duration of residency in a non-endemic area and risk of severe malaria in African immigrants

Färnert

Wyss

Dashti

et al. 2015

Clinical Microbiology and Infection

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In malaria-endemic areas, adults very rarely succumb to severe malaria, suggesting that immunity to severe disease is life-long under conditions of repeated exposure. To what extent this protection persists in the absence of exposure remains to be established. The aim of this study was to assess whether duration of residency in a malaria-free country affects the risk for severe malaria in immigrants originating from sub-Saharan Africa. We conducted a retrospective chart review of 948 cases of malaria diagnosed in Stockholm, Sweden in 1995-2013. Among 501 adult patients with Plasmodium falciparum (315 of endemic origin and 186 of non-endemic origin, mainly Sweden), 41 (8.2%) had severe malaria according to WHO criteria (including 5% with parasitaemia), 22 (4.4%) had factors prognostic of poor outcome, and 35 (7.0%) were admitted to intensive care. Overall, patient origin did not affect the odds of severe malaria, according to any of these definitions. However, when the immigrants were stratified with regard to their duration of residency in Sweden, the risk of factors prognostic for poor outcome was associated with duration of prior residency in a malaria-free country among patients of endemic origin (p 0.02), and immigrants who had lived for ≥ 15 years in Sweden had a similar risk as non-immune travellers. The results of this explorative study suggest that, although immunity to severe malaria is maintained for several years in African adults, this protection might be lost with time without repeated re-exposure. A larger study, preferably including multiple centres, will be needed to confirm our findings.

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Section: Discussioncontrasting

confidence: 69%

Section: Introductionmentioning

confidence: 99%

Duration of residency in a non-endemic area and risk of severe malaria in African immigrants

Färnert

Wyss

Dashti

et al. 2015

Clinical Microbiology and Infection

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“…Conversely, very few cases in immigrants or travellers visiting friends or relatives were severe, supporting the hypothesis that at least some long-term semi-immunity to malaria in people born and raised in an endemic area persists and translates into less severe clinical manifestations of disease. 21 Additional clinical context of this report's findings can be found in Appendix 1, available at www .cmajopen.ca/content/4/3/E352/suppl/DC1.…”

Section: Discussionmentioning

confidence: 95%

Malaria in travellers returning or migrating to Canada: surveillance report from CanTravNet surveillance data, 2004-2014

et al. 2016

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Background: Malaria remains the most common specific cause of fever in returned travellers and can be life-threatening. We examined demographic and travel correlates of malaria among Canadian travellers and immigrants to identify groups for targeted pretravel intervention.Methods: Descriptive data on ill returned Canadian travellers and immigrants presenting to a CanTravNet site between 2004 and 2014 with a diagnosis of malaria were analyzed. Data were collected using the GeoSentinel data platform. This network comprises 63 specialized travel and tropical medicine clinics, including 7 Canadian sites (Vancouver, Calgary, Toronto, Ottawa, Winnipeg and Montréal), that contribute anonymous, delinked, clinician-and questionnaire-based travel surveillance data on all ill travellers examined to a centralized Structure Query Language database. Results:During the study period, 20 345 travellers and immigrants were evaluated, and 93% had a travel-related diagnosis. Of these, 437 (2.1%) patients received 456 malaria diagnoses, the most common species being Plasmodium falciparum (n = 282, 61.8%). People travelling to visit friends and relatives were most well-represented (n = 169, 38.7%), followed by business travellers (n = 71, 16.2%). Sub-Saharan Africa was the most common source region, accounting for 341 (74.8%) malaria diagnoses, followed by South Central Asia (n = 55, 12%). Nigeria was the most well-represented source country, accounting for 41 cases (9.0%). India, a high-volume destination for Canadians, accounted for 40 cases (8.8%), 36 of which were caused by Plasmodium vivax. Of 456 malaria diagnoses, 26 (5.7%) were severe. Of 377 nonimmigrant travellers with malaria, 19.9% (n = 75) travelled for less than 2 weeks, and 7.2% (n = 27) travelled for less than 1 week. Interpretation:This analysis provides an epidemiologic framework for Canadian practitioners encountering prospective and returned travellers. It confirms the importance of preventive measures and surveillance associated with travel to sub-Saharan Africa and India, particularly by travellers visiting friends or relatives. Short-duration travel confers important malaria risk. Abstract Research CMAJ OPENCMAJ OPEN, 4(3) E353 surveillance summary of malaria in a cohort of returned travellers and new immigrants presenting for care at CanTravNet sites over a 10-year period. Methods SettingSeven Canadian sites from 5 provinces (British Columbia, Alberta, Manitoba, Ontario and Quebec), also belonging to the GeoSentinel Global Surveillance Network, constitute CanTravNet, as described. 7 These sites are large referral-based outpatient centres staffed by specialists in travel and tropical medicine, which serve the Greater Vancouver-Victoria, Calgary, Winnipeg, Toronto, Ottawa and Montréal metropolitan areas and could account for service of almost 50% of the Canadian population. Network sites have been accrued over time, with inaugural sites in Toronto (1997) and Ottawa (1997), and more recent additional sites in Victoria-Vancouver (2009), Montréal (2007), Calgary...

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“…Over the last ten years, Chinese outbound travel and export of labour services have grown dramatically. More than 50,000 Chinese expatriates work in Africa each year, and this number is rapidly increasing [5]. A health issue of great concern is that Chinese workers, having returned from Africa, represent most cases of imported malaria.…”

Section: Introductionmentioning

confidence: 99%

Using WeChat official accounts to improve malaria health literacy among Chinese expatriates in Niger: an intervention study

Han

Guo

et al. 2016

Malar J

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BackgroundMalaria is the main health risk for Chinese expatriates working in Niger. Health education is a recommended intervention for prevention of malaria among non-immune travellers and expatriate workers. It is urgent to develop an effective and feasible way for these populations to obtain information about the prevention and treatment of malaria.MethodsAn individually randomized, unblinded, controlled trial was used to evaluate the effectiveness of using WeChat official accounts for health education to improve malaria health literacy among Chinese expatriates in Niger. A total 1441 participants completed a baseline malaria health literacy questionnaire and were randomly assigned to an intervention or comparison group in a ratio of 1:1. From July to October 2014, 50 malaria prevention and treatment messages were sent to the intervention group; 50 health news messages were concurrently sent to the control group. Both groups completed the malaria health literacy questionnaire again 4 months after the start of the education intervention. A questionnaire addressing satisfaction with the health education programme was completed by the intervention group. Malaria morbidity data for 2013 and 2014 were also collected.ResultsAt baseline, participant health literacy rates were 58.29, 62, 54, and 34% for skills, knowledge, practice, and attitude, respectively. After the intervention, rates for all four aspects of malaria literacy were above 70%. There was greater change in knowledge, attitude, practice, skills, and overall health literacy among the intervention group compared with the controls, with a statistically significant difference (p < 0.01). This was especially true for acquisition of malaria-related knowledge, practice and attitude; comprehensive intervention practices; and, correct use of rapid diagnostic tests (p < 0.001). The reported malaria morbidity during the study period decreased from 23.72 to 15.40%. Participants reported high levels of satisfaction with the WeChat health education programme with over 80% stating that they would continue to follow the programme.ConclusionsThe present health education intervention, via a WeChat official account, for the prevention and treatment of malaria among non-immune travellers and expatriate workers proved to be an effective, sustainable, feasible, and well accepted strategy for improving malaria health literacy among Chinese expatriates in Niger.

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Epidemiology of imported malaria give support to the hypothesis of ‘long-term’ semi-immunity to malaria in sub-Saharan African migrants living in France

Cited by 33 publications

References 34 publications

Duration of residency in a non-endemic area and risk of severe malaria in African immigrants

Duration of residency in a non-endemic area and risk of severe malaria in African immigrants

Malaria in travellers returning or migrating to Canada: surveillance report from CanTravNet surveillance data, 2004-2014

Using WeChat official accounts to improve malaria health literacy among Chinese expatriates in Niger: an intervention study

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