Migration and Malaria in Europe

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Abstract

The proportion of imported malaria cases due to immigrants in Europe has increased during the lasts decades, with higher rates associated with settled immigrants who travel to visit friends and relatives (VFRs) in their country of origin. Cases are mainly due to P. falciparum and Sub-Saharan Africa is the most common origin. Clinically, malaria in immigrants is characterised by a mild clinical presentation including asymptomatic or delayed malaria cases and low parasitic levels. These characteristics may be explained by a semi-immunity acquired after long periods of time exposed to stable malaria transmission. Malaria cases among immigrants, even asymptomatic patients with sub-microscopic parasitemia, could increase the risk of transmission and cause the reintroduction of malaria in certain areas that have adequate vectors and climate conditions. Moreover, imported malaria cases in immigrants can also play an important role in the non-vector transmission out of endemic areas, through blood transfusions, organ transplantation or congenital transmission or occupational exposures. Consequently, outside of endemic areas, malaria screening should be carried out among recently arrived immigrants coming from malaria endemic countries. The aim of screening is to reduce the risk of clinical malaria in the individual as well as to prevent autochthonous transmission of malaria in areas where it has been eradicated.

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Submicroscopic Plasmodium falciparum gametocyte densities frequently result in mosquito infection.

Petra Schneider, J Teun Bousema, Louis C. Gouagna … (2007)

Submicroscopic Plasmodium falciparum gametocytemia (<5,000 gametocytes/mL) is common and may result in mosquito infection. We assessed the relation between gametocyte density and mosquito infection under experimental and field conditions using real-time quantitative nucleic acid sequence-based amplification (QT-NASBA) for gametocyte quantification. Serial dilutions of NF54 P. falciparum gametocytes showed a positive association between gametocyte density and the proportion of infected mosquitoes (beta=6.1; 95% confidence interval [CI], 2.7-9.6; P=0.001). Successful infection became unlikely below an estimated density of 250-300 gametocytes/mL. In the field, blood samples of 100 naturally infected children showed a positive association between gametocyte density and oocyst counts in mosquitoes (beta=0.38; 95% CI, 0.14-0.61; P=0.002). The relative contribution to malaria transmission was similar for carriers with submicroscopic and microscopic gametocytemia. Our results show that transmission occurs efficiently at submicroscopic gametocyte densities and that carriers harboring submicroscopic gametocytemia constitute a considerable proportion of the human infectious reservoir.

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High prevalence of asymptomatic Plasmodium vivax and Plasmodium falciparum infections in native Amazonian populations.

F. Javier Alves, K Krieger, Gabriel H Campolina-Silva … (2002)

The epidemiology of malaria in 2 riverine localities in Rondĵnia, Brazilian western Amazĵnia, was assessed by a 1-year study at Portuchuelo, and a cross-sectional survey at riverine communities at Rio Machado (= Ji-Parana). Plasmodium spp. infections were diagnosed by light microscopy and by polymerase chain reaction (PCR) amplification of ribosomal DNA. PCR was 6-7 times more efficient than microscopy for detecting plasmodial infections. Both Plasmodium vivax and Plasmodium falciparum infections occurred as asymptomatic and symptomatic forms of the disease. The relation between symptomatic and asymptomatic clinical forms was roughly similar for both species of Plasmodium. Symptomless patients were monitored for 2 months. The prevalence of symptomless infections was 4-5 times higher than the symptomatic ones--respectively, 20% and 4.6% for Portuchuelo and 49.5% and 10% for Ji-Parana. Symptomatic malaria occurred mostly in patients in younger age groups. In contrast, there was a significant association of symptomless malaria with older age groups (medians of 26.5 and 21 years, respectively, for Portuchuelo and Ji-Parana), whereas the age medians for symptomatic malaria were 14 and 8 years, respectively, in the 2 regions. Symptomatic malaria also was more prevalent in groups living for shorter times in Amazĵnia (13 and 4 years, respectively, for Portuchuelo and Ji-ParanA) as compared with symptomless malaria, which was more prevalent in groups living for longer periods in the region (medians of 25.5 and 18 years, respectively, for Portuchuelo and Ji-Paraná). The high prevalence of symptomless malaria may pose new problems for the currently adopted strategy for the control of malaria in the Amazonian region, which is essentially based on the treatment of symptomatic patients.

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Association of transmission intensity and age with clinical manifestations and case fatality of severe Plasmodium falciparum malaria.

Chris Drakeley, Redempta Mbatia, Hugh Reyburn … (2005)

There are concerns that malaria control measures such as use of insecticide-treated bed nets, by delaying acquisition of immunity, might result in an increase in the more severe manifestations of malaria. An understanding of the relationships among the level of exposure to Plasmodium falciparum, age, and severity of malaria can provide evidence of whether this is likely. To describe the clinical manifestations and case fatality of severe P falciparum malaria at varying altitudes resulting in varying levels of transmission. A total of 1984 patients admitted for severe malaria to 10 hospitals serving populations living at levels of transmission varying from very low (altitude >1200 m) to very high (altitude or =15 years: OR, 0.44; 95% CI, 0.27-0.73; P 1200 m: OR, 0.55; 95% CI, 0.26-1.15; P for trend = .03). The odds of cerebral malaria were significantly higher in low transmission intensity areas (altitude of residence 1200 m: OR, 3.76; 95% CI, 1.96-7.18; P for trend = .003) and with age 5 years and older (0-1 year: referent; 2-4 years: OR, 1.57; 95% CI, 0.82-2.99; 5 to or =15 years: OR, 6.24; 95% CI, 3.47-11.21; P<.001). The overall case-fatality rate of 7% (139 deaths) was similar at high and moderate levels of transmission but increased to 13% in low transmission areas (P = .03), an increase explained by the increase in the proportion of cases with cerebral malaria. Age and level of exposure independently influence the clinical presentation of severe malaria. Our study suggests that an increase in the proportion of cases with more fatal manifestations of severe malaria is likely to occur only after transmission has been reduced to low levels where the overall incidence is likely to be low.

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Author and article information

Journal

Journal ID (nlm-ta): Mediterr J Hematol Infect Dis

Journal ID (iso-abbrev): Mediterr J Hematol Infect Dis

Journal ID (publisher-id): Mediterranean Journal of Hematology and Infectious Diseases

Title: Mediterranean Journal of Hematology and Infectious Diseases

Publisher: Università Cattolica del Sacro Cuore

ISSN (Electronic): 2035-3006

Publication date Collection: 2012

Publication date (Electronic): 10 March 2012

Volume: 4

Issue: 1

Electronic Location Identifier: e2012014

Affiliations

Tropical Medicine. Infectious Diseases Department. Hospital Ramón y Cajal, Madrid, Spain

Author notes

Correspondence to: Rogelio López-Vélez. Tropical Medicine. Infectious Diseases Department. Hospital Ramón y Cajal. Carretera de Colmenar 9,1. Madrid 28034, Spain. E-mail: rlopezvelez.hrc@ 123456salud.madrid.org

Article

Publisher ID: mjhid-4-1-e2012014

DOI: 10.4084/MJHID.2012.014

PMC ID: 3335816

PubMed ID: 22536477

SO-VID: dd1a604c-b359-4a35-b6f9-a84450c2ab1a

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.

Migration and Malaria in Europe

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Most cited references 90

Submicroscopic Plasmodium falciparum gametocyte densities frequently result in mosquito infection.

High prevalence of asymptomatic Plasmodium vivax and Plasmodium falciparum infections in native Amazonian populations.

Association of transmission intensity and age with clinical manifestations and case fatality of severe Plasmodium falciparum malaria.

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