Epidemiological Risk Factors for Severe Plasmodium vivax Malaria in Peru
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Recent investigation has produced a significant shift in the paradigm of Plasmodium vivax. No longer characterized as a mild and clinically benign disease, P. vivax can produce severe and life-threatening symptoms. While most of the recent literature seeks to address the clinical manifestations of severe P. vivax infection, we have chosen to examine the epidemiological risk factors in the progression to severe disease. We conducted an analysis based upon a prospective case-control study that took place between the years of 2012-2015 in the Peruvian Amazon Basin. The study population of 215 total patients with mono-infection of P. vivax consisted of 125 cases and 90 controls - as defined by the WHO guidelines for severe falciparum malaria. Men and women comprised 56% and 44% of the patients, respectively. Ages ranged from 4 to 88 years, including 20 children. Factors we found to be associated with severe malaria include sex, previous infection with malaria, and residence proximity to water. To determine significance, we performed chi-squared and logistic regression analyses and obtained odds ratios, p-values, and 95% confidence intervals using STATA software. Women were three times more likely to present with severe vivax malaria than men (p=0.0001). Patients with previous malaria infection(s) of any species were 4.16 times less likely to develop severe malaria (p=0.0003), suggesting that prior infection may be protective. Finally, we observed that study participants who lived near a source of water are 2.9 times more likely to present with severe infection (p=0.0005. Future studies should focus on identifying the relative contributions of innate host factor (immuno-tolerance and genetics) with differences associated with pathogen exposure (parasite load strain).