Longitudinal estimation of Plasmodium falciparum prevalence in relation to malaria prevention measures in six sub-Saharan African countries

Chris Drakeley, Salim Abdulla, Selidji Todagbe Agnandji, José Francisco Fernandes, Peter Kremsner, Bertrand Lell, Ludovic Mewono, Bache Emmanuel Bache, Michael Gabriel Mihayo, Omar Juma, Marcel Tanner, Marc Christian Tahita, Halidou Tinto, Salou Diallo, Palpouguini Lompo, Umberto D’Alessandro, Bernhards Ogutu, Lucas Otieno, Solomon Otieno, Walter Otieno, Janet Oyieko, Kwaku Poku Asante, Dominic Bon-Ereme Dery, George Adjei, Elisha Adeniji, Dorcas Atibilla, Seth Owusu-Agyei, Brian Greenwood, Samwel Gesase, John Lusingu, Coline Mahende, Robert Mongi, Method Segeja, Samuel Adjei, Tsiri Agbenyega, Alex Agyekum, Daniel Ansong, John Tanko Bawa, Harry Owusu Boateng, Léonard Dandalo, Veronica Escamilla, Irving Hoffman, Peter Maenje, Francis Martinson, Terrell Carter, Didier Leboulleux, David C. Kaslow, Effua Usuf, Jean-Yves Pirçon, Edith Roset Bahmanyar

Plasmodium falciparum prevalence (PfPR) is a widely used metric for assessing malaria transmission intensity. This study was carried out concurrently with the RTS,S/AS01 candidate malaria vaccine Phase III trial and estimated PfPR over ≤ 4 standardized cross-sectional surveys. This epidemiology study (NCT01190202) was conducted in 8 sites from 6 countries (Burkina Faso, Gabon, Ghana, Kenya, Malawi, and Tanzania), between March 2011 and December 2013. Participants were enrolled in a 2:1:1 ratio according to age category: 6 months-4 years, 5-19 years, and ≥ 20 years, respectively, per year and per centre. All sites carried out surveys 1-3 while survey 4 was conducted only in 3 sites. Surveys were usually performed during the peak malaria parasite transmission season, in one home visit, when medical history and malaria risk factors/prevention measures were collected, and a blood sample taken for rapid diagnostic test, microscopy, and haemoglobin measurement. PfPR was estimated by site and age category. Overall, 6401 (survey 1), 6411 (survey 2), 6400 (survey 3), and 2399 (survey 4) individuals were included in the analyses. In the 6 months-4 years age group, the lowest prevalence (assessed using microscopy) was observed in 2 Tanzanian centres (4.6% for Korogwe and 9.95% for Bagamoyo) and Lambaréné, Gabon (6.0%), while the highest PfPR was recorded for Nanoro, Burkina Faso (52.5%). PfPR significantly decreased over the 3 years in Agogo (Ghana), Kombewa (Kenya), Lilongwe (Malawi), and Bagamoyo (Tanzania), and a trend for increased PfPR was observed over the 4 surveys for Kintampo, Ghana. Over the 4 surveys, for all sites, PfPR was predominantly higher in the 5-19 years group than in the other age categories. Occurrence of fever and anaemia was associated with high P. falciparum parasitaemia. Univariate analyses showed a significant association of anti-malarial treatment in 4 surveys (odds ratios [ORs]: 0.52, 0.52, 0.68, 0.41) and bed net use in 2 surveys (ORs: 0.63, 0.68, 1.03, 1.78) with lower risk of malaria infection. Local PfPR differed substantially between sites and age groups. In children 6 months-4 years old, a significant decrease in prevalence over the 3 years was observed in 4 out of the 8 study sites. Trial registration Clinical Trials.gov identifier: NCT01190202:NCT. GSK Study ID numbers: 114001.