Benign Tertian Malaria: How Benign Is It Today?

Abstract

Malaria is a disease of global importance and afflicts more than 90 countries and territories in the tropical and subtropical regions. Malaria imposes great socio-economic burden on humanity, and with six other diseases (diarrhea, HIV/AIDS, tuberculosis, measles, hepatitis B, and pneumonia), accounts for 85% of global infectious disease burden. TheWorld Health Organization (WHO) estimates 3.3 billion people at risk, 247 million malaria cases and one million estimated annual malarial mortality worldwide [1]. Approximately 2.48 million cases are reported annually from South-east Asia, of which 75% cases are contributed by India alone. WHO has reported malaria mortality rate 15000 per year from India; however, a recent study by million death collaborators suggest much higher annual malarial mortality in India (205,000 overall and 55000 in children <14 years age) [2]. Among cases with malaria, proportion of Plasmodium vivax (Pv) and P. falciparum (Pf) varies in different parts of India with 10–30% cases caused by Pf and remaining 70– 90% by Pv in most parts of the country. A continued rise in Pf has been reported recently and its proportion has gradually risen to nearly 50% of total cases in recent years [3]. Traditionally, infection with Pf is considered responsible for severe malaria and malarial mortality in literature. Very little information is available on the contribution of Pv to severe disease. As the term “benign tertian malaria” implies, Pv malaria has usually enjoyed the status of uncomplicated disease that runs a benign course and is rarely fatal. Earlier studies from Thailand and Vanuatu in last decade suggested a protective effect of Pv and suggested that Pv co-infection with Pf may attenuate severity of Pf malaria [4, 5]. However, there is growing evidence that Pv is responsible for a significant burden of disease worldwide. Recent studies from Papua New Guinea, Indonesia and India have reported all complications of severe malaria with Pv monoinfections as well [6– 8]. These studies have shown that 21–27% of patients with severe malaria have Pv monoinfection and clinical spectrum of these cases is broad with an overall mortality of 0.8–1.6% [9]. A study from Bikaner, in northwest India has reported a much higher proportion (63.1%) of severe malaria contributed by Pv mono-infection in children. In this study, the proportion of severe malaria attributable to P. vivax was 67.4% in children <5 years of age compared with 30.4% of P. falciparum and 2.2% (1/46) of mixed infection. Besides this, proportion of patients having severe manifestations, including severe anemia, thrombocytopenia, cerebral malaria, acute respiratory distress syndrome (ARDS), hepatic dysfunction, renal dysfunction and abnormal bleeding was also significantly higher in association with Pv monoinfection in 0–5 year age group. Also, Pv monoinfection was reported almost equally serious to cause significant mortality in comparison to Pf (case fatality rate of severe Pv was 3.9% versus 3.2% of severe Pf; P=1.0) [7]. This study further reaffirms the emergence of severe vivax malaria. Complications in severe malaria are either sequestration related, such as cerebral malaria, renal dysfunction, hepatic dysfunction and ARDS, or non-sequestration related, such as anemia and thrombocytopenia [10]. Sequestration related complications were earlier reported in Pf infection only; however, clinical data provided by Kochar, et al. indicates that Pv infection can cause both sequestration related and D. Yadav : J. Chandra :A. K. Dutta Department of Pediatrics, Lady Hardinge Medical College and associated Kalawati Saran Children’s Hospital, New Delhi, India