Longitudinal characterization of Plasmodium inter-species interactions during a period of increasing prevalence of Plasmodium ovale

Background The epidemiology and severity of non-falciparum malaria in endemic settings has garnered limited attention. We aimed to characterize the prevalence, interaction, clinical risk factors and temporal trends of non-falciparum malaria in endemic settings of Kenya. Methods We diagnosed and analyzed infecting malaria species via PCR in 2027 clinical samples collected between 2008 and 2016. Descriptive statistics were used to describe the prevalence and distribution of Plasmodium species. A statistical model was designed and used for estimating the frequency of Plasmodium species and assessing inter-species interactions. Mixed effect linear regression models with random intercepts for each location was used to test for change in prevalence over time. Findings 72•5% of the samples were P. falciparum single species infections, 25·8% were mixed infections and only 1•7% occurred as single non-falciparum species infections. 23•1% were mixed infections containing P. ovale . A likelihood-based model calculation of the population frequency of each species estimated a significant within-host interference between P. falciparum and P. ovale curtisi . Mixed-effect logistic regression models identified a significant increase of P. ovale wallikeri and P. ovale curtisi species over time with reciprocal decrease in P. falciparum single species and P. malariae . The risk of P. falciparum infections presenting with fever was 0•43 times less likely if co-infected with P. malariae . Interpretation Findings show higher prevalence of non-falciparum malaria than expected. The proportion of infections that were positive for infection by P. ovale wallikeri and P. ovale curtisi was observed to significantly increase over the period of study which could be due to attenuated responsiveness to malaria drug treatment on these species. The increase in frequency of P. ovale spp in Kenya could threaten malaria control effort in Kenya and pose increased risk of malaria to travelers. Funding AFHSB and its GEIS Section ### Competing Interest Statement The authors have declared no competing interest. ### Funding Statement Material has been reviewed by the Walter Reed Army Institute of Research. There is no objection to its presentation and/or publication. The opinions or assertions contained herein are the private views of the author, and are not to be construed as official, or as reflecting true views of the Department of the Army or the Department of Defense. The investigators have adhered to the policies for protection of human subjects as prescribed in AR 70–25. Financial support: Funding for this study was provided by the Armed Forces Health Surveillance Branch (AFHSB) and its Global Emerging Infections Surveillance (GEIS) Section, Grant P0209\_15\_KY. The study sponsor had no role in study design; in the collection, analysis, and interpretation of data; in the writing of the report; and in the decision to submit the paper for publication. The corresponding author should confirm that he or she had full access to all the data in the study and had final responsibility for the decision to submit for publication. ### Author Declarations All relevant ethical guidelines have been followed; any necessary IRB and/or ethics committee approvals have been obtained and details of the IRB/oversight body are included in the manuscript. Yes All necessary patient/participant consent has been obtained and the appropriate institutional forms have been archived. Yes I understand that all clinical trials and any other prospective interventional studies must be registered with an ICMJE-approved registry, such as ClinicalTrials.gov. I confirm that any such study reported in the manuscript has been registered and the trial registration ID is provided (note: if posting a prospective study registered retrospectively, please provide a statement in the trial ID field explaining why the study was not registered in advance). Yes I have followed all appropriate research reporting guidelines and uploaded the relevant EQUATOR Network research reporting checklist(s) and other pertinent material as supplementary files, if applicable. Yes All data generated by this study was was available to the authors. The data is also available for this submission