Malarial Parasite More Serious Than Previously Thought

Editor's Choice
Main Category: Tropical Diseases
Also Included In: Infectious Diseases / Bacteria / Viruses;  Public Health
Article Date: 17 Jun 2008 - 0:00 PDT

email to a friend   printer friendly   opinions  

Plasmodium vivax can cause malaria and substantial morbidity and mortality, especially in young children, according to two studies released on June 16, 2008 in the open access journal PLoS Medicine.

Seldom fatal and less virulent than some other malarial strains such as P. falciparum, P. vivax was generally considered benign before this set of studies. It was thought to cause a recurring form of the disease, with serious but rarely deadly symptoms.

In the first study, Ric Price and colleagues from the Menzies School of Health Research, Darwin, Australia, took data collected from all patients, inpatient and outpatient, in a hospital serving a large areas of the southern lowlands of Papua, Indonesia between January 2004 and December 2007. Of inpatients with confirmed malaria, two thirds were infected with P. falciparum, a quarter with P. vivax, while the res had a mixture of parasites causing the disease. When comparing the rates of severe malaria in this population, almost one quarter of patients with P. vivax developed severe malaria, in comparison with one fifth of patients with P. falciparum, and one third of those with both parasites. Severe malaria was also most frequent in children under five years old.

The second study, run by Blaise Genton and colleagues at the Swiss Tropical Institute, Basel, Switzerland, gathered data from everyone showing malaria like symptoms (but no other indication of disease) in either of two rural health facilities in the Wosera district of Papua New Guinea in an eight year timespan. Of more than 17,000 presumptive malaria cases, almost 500 displayed severe malaria (2.8%,) most of whom were children under five years old. In this age group, 11.7% were infected with P. falciparum, 8.8% were infected with P. vivax and 17.3% had both parasites.

Similar rates and outcomes of severe malaria were shown in both studies due to P. vivax or P. falciparum, despite being in different locations, with different populations, and different cultural and ethnic characteristics. In general, P. vivax peaks at an earlier age, and young children were more likely to develop clinical and severe disease. Notably, the studies reported cases of cerebral malaria due to P. vivax, which usually shows very few cases of secondary infection.

Stephen Rogerson of the University of Melbourne, Australia, contributed a related comment in the same issue of PLoS Medicine. He states that these findings are in direct challenge of the current philosophy in the field, that P. falciparum is severe and life threatening, while P. vivax is almost exclusively mild.

He also points out that limitations to these studies do exist, for instance: comorbidities such as bacterial or viral infections, and the potential underestimation of the mixed infections. However, the similarity of the results in the face of these limitations indicates some robustness of the study: "Despite these limitations, a striking feature of the two studies is the overall comparable incidence of severe disease in P. vivax and P. falciparum infections in each setting.  There were differences in the prevalence of the components of severe disease in the two locations and a notable disparity in the overall rates of severe disease," he comments.

He continues, encouraging a greater focus on P. vivax in the spectrum of international health. "With calls for increased efforts to control malaria internationally, it will be important to ensure that P. vivax receives appropriate attention.  We still lack reliable estimates of its global burden, and are only now starting to appreciate certain aspects of disease presentation of P. vivax malarial infection. The burden and severity of vivax in different settings requires further study," he says, then continues.  "The two reports by Price et al and Genton et al provide information about disease burden critical to improved decision making for the public health management of P. vivax malaria."

About PLoS Medicine

PLoS Medicine is an open access, freely available international medical journal. It publishes original research that enhances our understanding of human health and disease, together with commentary and analysis of important global health issues. For more information, visit http://www.plosmedicine.org.

About the Public Library of Science

The Public Library of Science (PLoS) is a non-profit organization of scientists and physicians committed to making the world's scientific and medical literature a freely available public resource. For more information, visit http://www.plos.org.

Multidrug-resistant Plasmodium vivax associated with severe and fatal malaria: a prospective study in Papua, Indonesia.
Tjitra E, Anstey NM, Sugiarto P, Warikar N, Kenangalem E, et al.
PLoS Med 5(6): e128.
Click Here For Full Length Article

Plasmodium vivax and mixed infections are associated with severe malaria in children: a prospective cohort study from Papua New Guinea.
Genton B, D'Acremont V, Rare L, Baea K, Reeder JC, et al.
PLoS Med 5(6): e127.
Click Here For Full Length Article

Severe vivax malaria: Newly recognised or rediscovered?
Rogerson SJ, Carter R
PLoS Med 5(6): e136.
Click Here For Full Length Comment

Written by Anna Sophia McKenney
Copyright: Medical News Today
Not to be reproduced without permission of Medical News Today

• Additional
• References
• Citations