Multidrug-resistant Plasmodium vivax (Pv) is widespread in eastern Indonesia, and emerging elsewhere in Asia-Pacific and South America, but is generally regarded as a benign disease. The aim of the study was to review the spectrum of disease associated with malaria due to Pv and P. falciparum (Pf) in patients presenting to a hospital in Timika, southern Papua, Indonesia.
Methods and Findings
Data were prospectively collected from all patients attending the outpatient and inpatient departments of the only hospital in the region using systematic data forms and hospital computerised records. Between January 2004 and December 2007, clinical malaria was present in 16% (60,226/373,450) of hospital outpatients and 32% (12,171/37,800) of inpatients. Among patients admitted with slide-confirmed malaria, 64% of patients had Pf, 24% Pv, and 10.5% mixed infections. The proportion of malarial admissions attributable to Pv rose to 47% (415/887) in children under 1 y of age. Severe disease was present in 2,634 (22%) inpatients with malaria, with the risk greater among Pv (23% [675/2,937]) infections compared to Pf (20% [1,570/7,817]; odds ratio [OR] = 1.19 [95% confidence interval (CI) 1.08–1.32], p = 0.001), and greatest in patients with mixed infections (31% [389/1,273]); overall p < 0.0001. Severe anaemia (haemoglobin < 5 g/dl) was the major complication associated with Pv, accounting for 87% (589/675) of severe disease compared to 73% (1,144/1,570) of severe manifestations with Pf (p < 0.001). Pure Pv infection was also present in 78 patients with respiratory distress and 42 patients with coma. In total 242 (2.0%) patients with malaria died during admission: 2.2% (167/7,722) with Pf, 1.6% (46/2,916) with Pv, and 2.3% (29/1260) with mixed infections (p = 0.126).
In this region with established high-grade chloroquine resistance to both Pv and Pf, Pv is associated with severe and fatal malaria particularly in young children. The epidemiology of P. vivax needs to be re-examined elsewhere where chloroquine resistance is increasing.
Ric Price and colleagues present data from southern Papua, Indonesia, suggesting that malaria resulting from infection withPlasmodium vivax is associated with substantial morbidity and mortality.
Malaria, a parasitic disease transmitted to people by mosquitoes, is common throughout the tropical and subtropical areas of the world. In sub-Saharan Africa, infections with Plasmodium falciparum cause most of the malaria-associated illness and death. Elsewhere, another related parasite—P. vivax—is often the commonest cause of malaria. Both parasites are injected into the human blood stream when an infected mosquito bites a person. From there, the parasites travel to the liver, where they multiply for 8–9 d and mature into a form of the parasite known as merozoites. These merozoites are released from the liver and invade red blood cells where they multiply rapidly for a couple of days before bursting out and infecting more red blood cells. This cyclical accumulation of parasites in the blood causes a recurring flu-like illness characterized by fevers, headaches, chills, and sweating. Malaria can be treated with antimalarial drugs but, if left untreated, infections with P. falciparum can cause anemia (by destroying red blood cells) and can damage the brain and other vital organs (by blocking the capillaries that supply these organs with blood), complications that can be fatal.
Why Was This Study Done?
Unlike falciparum malaria, vivax malaria is generally regarded as a benign or nonfatal disease even though there have been several reports recently of severe disease and deaths associated with vivax malaria. These reports do not indicate, however, whether P. vivax is responsible for a significant proportion of malarial deaths. Public health officials need to know this information because strains of P. vivax that are resistant to multiple antimalarial drugs are widespread in Indonesia and beginning to emerge elsewhere in Asia and South America. In this study, therefore, the researchers investigate the relative burden of vivax and falciparum malaria in Papua, Indonesia, a region where multidrug-resistant strains of both P. falciparum and P. vivax are common.
What Did the Researchers Do and Find?
The researchers examined data collected from all the patients attending the outpatient and inpatient departments of a hospital that serves a large area in the southern lowlands of Papua, Indonesia between January 2004 and December 2007. Among those inpatients in whom malaria had been confirmed by finding parasites in blood samples, two-thirds were infected with P. falciparum, a quarter with P. vivax, and the rest with a mixture of parasites. Nearly one in four patients infected with P. vivax developed severe malaria compared with roughly one in five patients infected with P. falciparum. However, about one in three patients infected with both parasites developed severe disease. Whichever parasite was responsible for the infection, the proportion of patients with severe disease was greatest among children below the age of five years. Severe anemia was the commonest complication associated with severe malaria caused by both P. vivax and P. falciparum (present in 87% and 73% of cases, respectively). Finally, one in 50 patients with malaria died; the risk of death was the same for patients infected with P. falciparum, P. vivax, or both parasites.
What Do These Findings Mean?
These findings provide important information about the burden of malaria associated with P. vivax infection. They show that in a region where multidrug-resistant strains of both P. falciparum and P. vivax are common, P. vivax infection (as well as P. falciparum infection) is associated with severe and fatal malaria, particularly in young children. The findings also show that infection with a mixture of the two parasites is associated with a higher risk of severe disease than infection with either parasite alone. Most importantly, they show that similar proportions of patients infected with P. falciparum, P. vivax, or a mixture of parasites die. Further studies need to be done in other settings to confirm these findings and to learn more about the pattern of severe malaria associated with P. vivax (in particular, with multidrug-resistant strains). Nevertheless, these findings highlight the need to consider both P. vivax and P. falciparum when implementing measures designed to reduce the malaria burden in regions where these parasites coexist.
Please access these Web sites via the online version of this summary at http://dx.doi.org/10.1371/journal.pmed.0050128.
A PLoS Medicine Research in Translation article by Stephen Rogerson further discusses this study and a related PLoS Medicine paper on vivax malaria in a community cohort from Papua New Guinea
The MedlinePlus encyclopedia has a page on malaria (in English and Spanish)
The US Centers for Disease Control and Prevention provides information on malaria (in English and Spanish)
Vivaxmalaria provides information on topics related to P. vivax
The Malaria Vaccine Initiative also provides a fact sheet on P. vivax malaria
Information is available from the Roll Back Malaria Partnership on the global control of malaria