Africa Health: Plasmodium vivax infection is conspicuously absent in most of Africa – except in Ethiopia where it accounts for a significant proportion of malaria morbidity. MMV reports on the collaborations under development to counter the problem.
New antimalarial medicines and the clinical trial capacity to develop them are urgently needed in malaria-endemic countries, particularly those just south of the African Sahara where the burden of this disease is heaviest. In this region, malaria has historically been almost exclusively attributed to Plasmodium falciparum (Pf), while Plasmodium vivax (Pv) or relapsing malaria, has been conspicuously ‘absent’.1 One possible reason is that most populations in sub-Saharan Africa are negative for Duffy antigen expression. As a result, their blood lacks the Duffy antigen that allows the Pv parasite to establish erythrocitic infection and so prevents Pv from establishing stable transmission.2
Ethiopia, however, presents a different case. The country has to deal with a huge burden of Pv in addition to high rates of Pf morbidity. This may in part be explained by the relatively higher proportion of people that are positive for Duffy antigen expression in Ethiopia compared to other African countries.3 Both Pf and Pv are prevalent in a ratio of approximately 75:25 in the country.4 Ethiopia together with India, Indonesia and Pakistan account for more than 80% of estimated Pv cases in the world.1 While the risks of severe disease and case fatality rates for Pv have not been firmly established, Pv clearly accounts for a significant proportion of malaria morbidity and the overall burden of disease.
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2. Howes RE, et al. The global distribution of the Duffy blood group. Nat Commun 2011; 2: 266
3. Mathews HM, Armstrong JC. Duffy blood types and vivax malaria in Ethiopia. Am J Trop Med Hyg 1981; 30 (2): 299–303.