Abstract
Malaria particularly burdens people in poor and neglected settings across the tropics of Africa. Meanwhile, a large proportion of the Togo population have poor understanding of malaria epidemiology and parasites. This study carried out a molecular survey of malaria cases in southern Togo during 2017–2019. We estimated Plasmodium species infection rates and microscopic examination compliance with nested PCR results. Sensitivity and specificity analyses were performed in conjunction with predictive values. Also, phylogenetic characterization of species of malaria parasites was assessed. Plasmodium genus-specific nested PCR identified 565 positive cases including 536/611 (87.8%) confirmed cases from the microscopy-positive group and 29/199 (14.6%) diagnosed malaria cases from the microscopy-negative group. Our findings revealed a disease prevalence (69.8%) higher than that reported (25.5–55.1%) for the country. The diagnostic test had 94.9% sensitivity and 69.4% specificity, i.e., it missed 120 of the people who had malaria and about one-third of the people tested positive for the disease, which they did not have, respectively. In conjunction, the test showed 87.7% positive predictive value and 85.4% negative predictive value, which, from a clinical perspective, indicates the chance that a person with a positive diagnostic test truly has the disease and the probability that a person with a negative test does not have the disease, respectively. Further species-specific nested PCR followed by analysis of gene sequences confirmed species of malaria parasites and indicated infection rates for Plasmodium falciparum (Pf), 95.5% (540/565); P. ovale (Po), 0.5% (3/565); and P. malariae (Pm), 0.4% (2/565). In addition, 20 cases were coinfection cases of Pf-Po (15/565) and Pf-Pm (5/565). This study publicly reports, for the first time, a molecular survey of malaria cases in Togo and reveals the presence of other malaria parasites (Po and Pm) other than Pf. These findings might provide answers to some basic questions on the malaria scenario and, knowledge gained could help with intervention deployment for effective malaria control in Togo.
Highlights
Malaria is a major debilitating infectious disease that affects millions of people and impedes public health and socioeconomic development in Africa (Kassegne et al, 2017)
Malaria epidemiology is poorly understood in Togo, with a paucity of information on species of Plasmodium that are responsible for disease transmission
In other words, nested Polymerase chain reaction (PCR) confirmed 536 out of 611 (87%) cases that were true positive from the microscopy-positive group (MPG) and identified 29/199 (14.6%) malaria cases that were found negative (Table 2) in the microscopynegative group (MNG)
Summary
Malaria is a major debilitating infectious disease that affects millions of people and impedes public health and socioeconomic development in Africa (Kassegne et al, 2017). In tropical Africa, nearly 90% of deaths among young children are related to malaria (World Health Organization [WHO], 2018b). In 2016, uncomplicated malaria was the first cause (41.7%) of outpatient consultations in public health centers and, hospitalization rate related to severe disease accounted for 20.5%, with 3.8% hospital mortality (Thomas et al, 2020). In 2017, > 60% of severe cases have not been to the hospital (Programe National de Lutte contre le Paludisme [PNLP], 2019). Children under 5 years old remain highly affected by malaria, with 35.4% uncomplicated outpatient cases, 58.4% hospitalized severe cases, and 69.7% deaths reported in 2017 (Programe National de Lutte contre le Paludisme [PNLP], 2019). Pregnant women accounted for 5% uncomplicated outpatients and 6% hospitalized severe cases (Programe National de Lutte contre le Paludisme [PNLP], 2019). Studies on disease burden erroneously made believe that malaria cases are only related to Plasmodium falciparum (Pf) infection in Togo (Bakai et al, 2020; Thomas et al, 2020), making the standards of care unilateral with important implications in disease epidemiology
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