The hidden malaria: Misidentification of Plasmodium malariae and Plasmodium ovale in low-transmission setting targeted for elimination in Ethiopia

Background A quartan malaria caused by Plasmodium malariae (Pm) and a tertian Plasmodium ovale (Po) malaria has been largely overlooked in Ethiopia due to milder clinical symptoms, lower prevalence, and the frequent misdiagnosis of these species during routine microscopic. This study estimated the prevalence of Pm and Po infections misdiagnosed as P. vivax (Pv) in selected health facilities in southwestern Ethiopia. Methods A cross-sectional study was conducted among study participants who were positive for Pv by microscopy or rapid diagnostic test (RDTs) and who were attending health facilities within Arjo-Didessa sugarcane plantations and surrounding areas in Oromia, southwestern Ethiopia, between September 2019 and July 2022. Of the 3590 febrile patients attending health facilities, 323 were Pv positive by microscopy or RDTs. Among these, 245 Pv positive samples were re-evaluated using quantitative polymerase chain reaction (qPCR). Species-specific primers targeting Pv, P. falciparum (Pf), Pm and Po were used for species confirmation. Results From 245 vivax malaria cases, RDTs was performed to 162 sub-samples, among them 8.6% (14/162) were negative by RDTs. None of the samples tested by RDTs and microscopy detected Pm or Po. Of these 245 tested Pv positive by microscopy was confirmed by PCR, among them 215 (87.7%, 95% CI: 82.98–91.58) were positive for Pv, 9 (3.7%, 95% CI: 1.69–6.86) for Pf, 8 (3.3%, 95% CI: 1.42–6.33) for Pm, 6 (2.4%, 95% CI: 0.90–5.25) were positive for Po and 7 (2.8%, 95% CI: 1.16–5.80) had mixed infections (Pf and Pv). Conclusion the findings of this study highlights the need for a strategic shift to integrate Pm and Po into Ethiopia's malaria control and elimination program. Moreover, strengthening the diagnostic capacity by including training microscopists for accurate Plasmodium species identification and adopting highly sensitive diagnostic tool for all four Plasmodium species in resource-limited settings. This is essential for enhancing malaria control and accelerating progress toward elimination.