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Vivax Malaria: Not Always Benign

Summary and Comment |
July 8, 2014

Vivax Malaria: Not Always Benign

  1. Mary E. Wilson, MD

Among vivax malaria patients in coastal Peru in 2008–2009, 0.4% were critically ill — more than half of them with severe anemia.

  1. Mary E. Wilson, MD

Several studies have documented that Plasmodium vivax can cause life-threatening illness. In a retrospective, case-control study in a coastal area of Peru where only vivax malaria is endemic, investigators evaluated the records of patients hospitalized with malaria at the area referral center between January 2008 and December 2009.

Patients who met at least one WHO criterion for severe malaria (severe anemia, lung injury, shock, renal failure, cerebral malaria) were considered for inclusion. Those with comorbidities, including HIV infection, were excluded. For each case-patient, the researchers selected four controls — patients with uncomplicated vivax malaria who were treated at local health clinics.

In the study area, 6502 cases of malaria were reported in 2008–2009; 106 required hospitalization. Severe malaria was determined in 81, including 28 (0.43% overall) who were identified as critically ill. Among these 28 patients, 16 (57%) had severe anemia; only 3 (11%) had cerebral malaria. Two deaths potentially related to vivax occurred during the study period. Compared to outpatients with uncomplicated vivax malaria, the hospitalized, critically ill patients were older (mean age, 38 vs. 26 years) and were more likely to have low-density infection (68% vs. 31% with 1 parasite/100 oil-immersion fields).

Comment

This study estimates the proportion of vivax malaria patients with severe or critical illness and underscores our limited understanding of this condition. As noted by an editorialist, the impression that P. vivax causes mild illness has resulted in a 60-year hiatus in vivax malaria research and serious gaps in the understanding of an infection that threatens 2.5 billion people. The contribution of comorbidities has not been well defined, and both the authors and the editorialist call for research to better understand the pathogenesis of the infection, including the occurrence of severe disease in individuals with low-level parasitemia. The hypnozoite reservoir in the liver presents a challenge, especially for pregnant women and people with glucose 6-phosphate dehydrogenase deficiency.

  • Disclosures for Mary E. Wilson, MD at time of publication Editorial boards UptoDate; Clinical Infectious Diseases; RSTMH International Health; Infectious Diseases in Clinical Practice; Travel Medicine and Infectious Diseases

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