Although malaria kills some 600,000 African children each year, most cases of the mosquito-borne parasitic disease in children are mild. Repeated infection does generate some immunity, and episodes of severe malaria are unusual once a child reaches age 5. However, the relative contributions of such factors as the level of malaria-causing parasites in a person's blood—parasite density—to disease severity and to development of protective immunity are not well understood.
To clarify these issues, researchers from the United States and Tanzania regularly examined 882 Tanzanian children beginning at birth and continuing for an average of two years. No simple relationship between parasite density and malaria severity emerged. For example, 253 children had a total of 444 infections characterized by high parasite density and mild symptoms. Of the 102 children who did develop severe malaria at least once while enrolled in the study, almost two-thirds (67) had high parasite density but only mild disease either before or after the episode of severe malaria.
Moreover, data from this study suggest that one or two mild episodes of malaria are not sufficient to eliminate the risk of severe malaria; a finding contrary to predictions made by some mathematical models. The researchers note that this prospective study is the first to provide direct evidence that severe malaria risk is stable over several infections. The findings suggest a new approach to malaria vaccine development based on naturally acquired immunity. Such a vaccine would prevent severe disease and death in children, without necessarily reducing exposure to the malaria parasite.
The research team was led by Patrick E. Duffy, M.D., of the National Institute of Allergy and Infectious Diseases (NIAID), part of the National Institutes of Health.
Explore further: Cross-species malaria immunity induced by chemically attenuated parasites
More information: BP Gonçalves et al. Parasite burden and severity of malaria in Tanzanian children. NEJM DOI: 10.1056/NEJM 10.1056/NEJMoa1303944 (2014).
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Although malaria kills some 600,000 African children each year, most cases of the mosquito-borne parasitic disease in children are mild. Repeated infection does generate some immunity, and episodes of severe malaria are unusual once a child reaches age 5. However, the relative contributions of such factors as the level of malaria-causing parasites in a person's blood—parasite density—to disease severity and to development of protective immunity are not well understood.
To clarify these issues, researchers from the United States and Tanzania regularly examined 882 Tanzanian children beginning at birth and continuing for an average of two years. No simple relationship between parasite density and malaria severity emerged. For example, 253 children had a total of 444 infections characterized by high parasite density and mild symptoms. Of the 102 children who did develop severe malaria at least once while enrolled in the study, almost two-thirds (67) had high parasite density but only mild disease either before or after the episode of severe malaria.
Moreover, data from this study suggest that one or two mild episodes of malaria are not sufficient to eliminate the risk of severe malaria; a finding contrary to predictions made by some mathematical models. The researchers note that this prospective study is the first to provide direct evidence that severe malaria risk is stable over several infections. The findings suggest a new approach to malaria vaccine development based on naturally acquired immunity. Such a vaccine would prevent severe disease and death in children, without necessarily reducing exposure to the malaria parasite.
The research team was led by Patrick E. Duffy, M.D., of the National Institute of Allergy and Infectious Diseases (NIAID), part of the National Institutes of Health.
Explore further: Cross-species malaria immunity induced by chemically attenuated parasites
More information: BP Gonçalves et al. Parasite burden and severity of malaria in Tanzanian children. NEJM DOI: 10.1056/NEJM 10.1056/NEJMoa1303944 (2014).
Medical Xpress on facebook
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Cross-species malaria immunity induced by chemically attenuated parasites
Jul 01, 2013
Malaria, a mosquito-born infectious disease, kills over 600,000 people every year. Research has focused on the development of a vaccine to prevent the disease; however, many malaria vaccines targeting parasite antigens have ...
How the immune system prevents repeated malaria fever episodes in highly exposed children
Apr 17, 2014
Children in Mali (and many other regions where malaria is common) are infected with malaria parasites more than 100 times a year, but they get sick with malaria fever only a few times. To understand how the immune system ...
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May 02, 2014
An Austrian commission following up on claims that doctors deliberately infected patients with malaria to treat others with syphilis says hundreds of people, including orphans in a psychiatric hospital, might have been infected.
Viruses common complication in malaria patients
Sep 24, 2013
Scientists at the University of Liverpool have shown that viral brain infections may be a more important killer in African children than was previously thought.
Malaria's severity reset by mosquito
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15 seconds ago
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