Summary Plasmodium vivax is geographically the most widely distributed cause of malaria in people, with up to 2·5 billion people at risk and an estimated 80 million to 300 million clinical cases every year—including severe disease and death. Despite this large burden of disease, P vivax is overlooked and left in the shadow of the enormous problem caused by Plasmodium falciparum in sub-Saharan Africa. The technological advances enabling the sequencing of the P vivax genome and a recent call for worldwide malaria eradication have together placed new emphasis on the importance of addressing P vivax as a major public health problem. However, because of this parasite's biology, it is especially difficult to interrupt the transmission of P vivax , and experts agree that the available methods for preventing and treating infections with P vivax are inadequate. It is thus imperative that the development of new methods and strategies become a priority. Advancing the development of such methods needs renewed emphasis on understanding the biology, pathogenesis, and epidemiology of P vivax . This Review critically examines what is known about P vivax , focusing on identifying the crucial gaps that create obstacles to the elimination of this parasite in human populations.

https://www.thelancet.com/pdfs/journals/laninf/PIIS1473-3099(09)70177-X.pdf

Key gaps in the knowledge of Plasmodium vivax, a neglected human malaria parasite

Background: Current understanding of the spatial epidemiology and geographical distribution of Plasmodium vivax is far less developed than that for P. falciparum, representing a barrier to rational strategies for control and elimination. Here we present the first systematic effort to map the global endemicity of this hitherto neglected parasite. Methodology and Findings: We first updated to the year 2010 our earlier estimate of the geographical limits of P. vivax transmission. Within areas of stable transmission, an assembly of 9,970 geopositioned P. vivax parasite rate (PvPR) surveys collected from 1985 to 2010 were used with a spatiotemporal Bayesian model-based geostatistical approach to estimate endemicity age-standardised to the 1–99 year age range (PvPR1–99) within every 565 km resolution grid square. The model incorporated data on Duffy negative phenotype frequency to suppress endemicity predictions, particularly in Africa. Endemicity was predicted within a relatively narrow range throughout the endemic world, with the point estimate rarely exceeding 7% PvPR1–99. The Americas contributed 22% of the global area at risk of P. vivax transmission, but high endemic areas were generally sparsely populated and the region contributed only 6% of the 2.5 billion people at risk (PAR) globally. In Africa, Duffy negativity meant stable transmission was constrained to Madagascar and parts of the Horn, contributing 3.5% of global PAR. Central Asia was home to 82% of global PAR with important high endemic areas coinciding with dense populations particularly in India and Myanmar. South East Asia contained areas of the highest endemicity in Indonesia and Papua New Guinea and contributed 9% of global PAR.

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A long neglected world malaria map: Plasmodium vivax endemicity in 2010.

Background: A research priority for Plasmodium vivax malaria is to improve our understanding of the spatial distribution of risk and its relationship with the burden of P. vivax disease in human populations. The aim of the research outlined in this article is to provide a contemporary evidence-based map of the global spatial extent of P. vivax malaria, together with estimates of the human population at risk (PAR) of any level of transmission in 2009. Methodology: The most recent P. vivax case-reporting data that could be obtained for all malaria endemic countries were used to classify risk into three classes: malaria free, unstable (,0.1 case per 1,000 people per annum (p.a.)) and stable ($0.1 case per 1,000 p.a.) P. vivax malaria transmission. Risk areas were further constrained using temperature and aridity data based upon their relationship with parasite and vector bionomics. Medical intelligence was used to refine the spatial extent of risk in specific areas where transmission was reported to be absent (e.g., large urban areas and malaria-free islands). The PAR under each level of transmission was then derived by combining the categorical risk map with a high resolution population surface adjusted to 2009. The exclusion of large Duffy negative populations in Africa from the PAR totals was achieved using independent modelling of the gene frequency of this genetic trait. It was estimated that 2.85 billion people were exposed to some risk of P. vivax transmission in 2009, with 57.1% of them living in areas of unstable transmission. The vast majority (2.59 billion, 91.0%) were located in Central and South East (CSE) Asia, whilst the remainder were located in America (0.16 billion, 5.5%) and in the Africa+ region (0.10 billion, 3.5%). Despite evidence of ubiquitous risk of P. vivax infection in Africa, the very high prevalence of Duffy negativity throughout Central and West Africa reduced the PAR estimates substantially. Conclusions: After more than a century of development and control, P. vivax remains more widely distributed than P. falciparum and is a potential cause of morbidity and mortality amongst the 2.85 billion people living at risk of infection, the majority of whom are in the tropical belt of CSE Asia. The probability of infection is reduced massively across Africa by the frequency of the Duffy negative trait, but transmission does occur on the continent and is a concern for Duffy positive locals and travellers. The final map provides the spatial limits on which the endemicity of P. vivax transmission can be mapped to support future cartographic-based burden estimations.

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The international limits and population at risk of Plasmodium vivax transmission in 2009

Tegumentary leishmaniasis, comprising the cutaneous and mucocutaneous forms, is caused by at least 13 dermotropic species of protozoa of the genus Leishmania, most of which are prevalent in the New World. Although diseases in the Old and New Worlds share similar characteristics, the ultimate manifestations and severity are quite different, with more severe forms associated with mucosal lesions observed in the New World. For the diagnosis and treatment of leishmaniasis, differences based on clinical features, usefulness/sensitivity of diagnostic methods and therapeutic responses are mainly emphasized. We present a critical review of the diagnostic methods, their contribution and the necessity for their improvement/development, particularly in molecular diagnosis aimed at detection and species identification, as well as serodiagnosis. In addition to a review of the drugs currently utilized, we describe differences in their effectiveness in Old and New World leishmaniasis. HIV/Leishmania coinfection is also presented in the context of diagnosis and treatment.

https://www.tandfonline.com/doi/pdf/10.1586/eri.10.19

Current diagnosis and treatment of cutaneous and mucocutaneous leishmaniasis

Malaria is still a major public health problem in Brazil, with approximately 306 000 registered cases in 2009, but it is estimated that in the early 1940s, around six million cases of malaria occurred each year. As a result of the fight against the disease, the number of malaria cases decreased over the years and the smallest numbers of cases to-date were recorded in the 1960s. From the mid-1960s onwards, Brazil underwent a rapid and disorganized settlement process in the Amazon and this migratory movement led to a progressive increase in the number of reported cases. Although the main mosquito vector (Anopheles darlingi) is present in about 80% of the country, currently the incidence of malaria in Brazil is almost exclusively (99,8% of the cases) restricted to the region of the Amazon Basin, where a number of combined factors favors disease transmission and impair the use of standard control procedures. Plasmodium vivax accounts for 83,7% of registered cases, while Plasmodium falciparum is responsible for 16,3% and Plasmodium malariae is seldom observed. Although vivax malaria is thought to cause little mortality, compared to falciparum malaria, it accounts for much of the morbidity and for huge burdens on the prosperity of endemic communities. However, in the last few years a pattern of unusual clinical complications with fatal cases associated with P. vivax have been reported in Brazil and this is a matter of concern for Brazilian malariologists. In addition, the emergence of P. vivax strains resistant to chloroquine in some reports needs to be further investigated. In contrast, asymptomatic infection by P. falciparum and P. vivax has been detected in epidemiological studies in the states of Rondonia and Amazonas, indicating probably a pattern of clinical immunity in both autochthonous and migrant populations. Seropidemiological studies investigating the type of immune responses elicited in naturally-exposed populations to several malaria vaccine candidates in Brazilian populations have also been providing important information on whether immune responses specific to these antigens are generated in natural infections and their immunogenic potential as vaccine candidates. The present difficulties in reducing economic and social risk factors that determine the incidence of malaria in the Amazon Region render impracticable its elimination in the region. As a result, a malaria-integrated control effort - as a joint action on the part of the government and the population - directed towards the elimination or reduction of the risks of death or illness, is the direction adopted by the Brazilian government in the fight against the disease.

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Malaria in Brazil: an overview

Epidemiologic studies and clinical description of severe Plasmodium vivax malaria in adults living in malaria-endemic areas are rare and more attention is needed to understand the dynamics and its interaction with the immune system. This observational study included 1,091 adult patients admitted to medical wards of S. P. Medical College and associated group of hospitals in Bikaner, India from September 2003 through December 2005. The diagnosis of P. vivax malaria was established by peripheral blood film (PBF), rapid diagnostic test (RDT), and polymerase chain reaction (PCR), and severe malaria was categorized as per World Health Organization guidelines. Of 1,091 patients with malaria, 635 had P. falciparum malaria and 456 had P. vivax malaria. Among patients with severe manifestations, 40 had evidence of monoinfection of P. vivax malaria diagnosed by PBF, RDT, and PCR. Complications observed were hepatic dysfunction and jaundice in 23 (57.5%) patients, renal failure in 18 (45%) patients, severe anemia in 13 (32.5%) patients, cerebral malaria in 5 patients (12.5%), acute respiratory distress syndrome in 4 patients (10%), shock in 3 patients (7.5%), and hypoglycemia in 1 (2.5%) patient. Thrombocytopenia was observed in 5 (12.5%) patients, and multi-organ dysfunction was detected in 19 (47.5%) patients. Further large-scale multicentric epidemiologic studies are needed to define the basic pathology of this less known entity.

Severe Plasmodium vivax Malaria : A Report on Serial Cases from Bikaner in Northwestern India

The occurrence, relation and magnitude of thrombocytopenia in different species of malaria are not clearly defined. This study included 1,064 patients admitted with malaria to study thrombocytopenia (platelet count <150,000 /cumm) in Plasmodium falciparum (Pf) and Plasmodium vivax (Pv) mono infection and mixed infection (Pf + Pv). The species diagnosis was done by peripheral blood film (PBF) and rapid diagnostic test (RDT). Validation by polymerase chain reaction (PCR) was done only in patients with severe thrombocytopenia (platelet count <20,000 /cumm). The breakup of patients was 525 (49.34%) Pf, 460 (43.23%) Pv and 79 (7.42%) mixed malaria (Pf + Pv). Thrombocytopenia was observed in 24.6% (262/1064) patients. The risk was greatest in the mixed infections in comparison to monoinfection individually (43.04% [34/79]; mixed vs Pv monoinfection: Odds Ratio [OR] = 1.675 [95% Confidence Interval (CI) 1.029–2.726], p < 0.0366; mixed vs Pf monoinfection: OR=3.911 [95% CI 2.367–6.463], p < 0.0001). Pv monoinfect...

Thrombocytopenia in Plasmodium falciparum, Plasmodium vivax and mixed infection malaria: a study from Bikaner (Northwestern India).

Background & objectives: This study was conducted on 50 patients of Anthroponotic cutaneous leishmaniasis (oriental sore) to assess the efficacy of rifampicin and omeprazole through a double blind, randomised placebo control study. Methods: The diagnosis of Anthroponotic cutaneous leishmaniasis (ACL) caused by Leishmania tropica was done by demonstration of Leishmania tropica (LT) bodies from the painless, dry ulcerative lesion. Each patient was assessed clinically in the beginning of the study, at the end of 2 ,4 and 6 weeks and all observations were compared in both the groups. Twenty-five patients received rifampicin with omeprazole (Group A) whereas other 25 patients received placebo (Group B) for a period of six weeks. Results: Altogether 23 cases in group A and 21 cases in group B completed the study. About 16 (69.7%) cases in group A and 3 (14.29%) cases in group B had complete healing, whereas 3 patients (13.04%) of group A and 4 patients (19.05%) of group B had partial response and 4 patients (17.93%) of group A and 14 patients (66.67%) of group B had no response at the end of study. The difference of two groups was statistically highly significant (p<0.00025). All patients tolerated the drug and placebo very well and no side effect was reported. Interpretation & conclusion: In our opinion rifampicin and omeprazole is a highly effective, less toxic and cheaper alternative for the management of cutaneous leishmaniasis.

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A double blind, randomised placebo controlled trial of rifampicin with omeprazole in the treatment of human cutaneous leishmaniasis.

https://www.thelancet.com/pdfs/journals/lancet/PIIS0140-6736(07)61417-2.pdf

An unexpected cause of fever and seizures

Background & objectives: Plasmodium falciparum (Pf) and Plasmodium vivax (Pv) are responsible for most of the global burden of malaria. With changing spectrum of clinical presentation in malaria, pulmonary system involvement has always been under diagnosed. The present study was planned to estimate the pulmonary system involvement in patients with malaria from north-western India (Bikaner). Study design & description of the patients: Our study was conducted during 2007 to 2009 in 200 cases of severe malaria [Pf , Pv, and mixed (Pf + Pv)] with pulmonary involvement. It included adult patients of both sexes (145 males and 55 females) belonging to all age groups. The diagnosis of Pf and Pv was confirmed by demonstrating asexual form of parasites in peripheral blood smear and OptiMal test. Main outcome measures: Pulmonary involvement was observed in 30% (60/200) patients among which cough in 24% , dyspnea in 12%, acute respiratory distress syndrome (ARDS) in 7% , bronchitis in 3% and pneumonia in 1.5% were the major clinical manifestations of malaria. Metabolic acidosis and low oxygen saturation was observed in 7% patients. Chest X-ray abnormality in 11.5% patients, 7% had bilateral infiltrates, 1.5% had inflammatory patch and 3% had findings suggestive of bronchitis. Spirometry findings showed 17% patients had early small airway obstruction. All the patients with ARDS had poor disease outcome. Results & conclusion: Our results suggest that pulmonary system involvement was observed in patients infected with Pf and Pv. If these clinical presentations are ignored, it may lead to delay in diagnosis and can alter the outcome and prognosis of the disease. Therefore, early diagnosis of malaria induced ARDS can significantly affect the outcome.

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Parmendra Sirohi

Papers

Severe Plasmodium vivax Malaria : A Report on Serial Cases from Bikaner in Northwestern India

Thrombocytopenia in Plasmodium falciparum, Plasmodium vivax and mixed infection malaria: a study from Bikaner (Northwestern India).

A double blind, randomised placebo controlled trial of rifampicin with omeprazole in the treatment of human cutaneous leishmaniasis.

An unexpected cause of fever and seizures

A study on pulmonary manifestations in patients with malaria from northwestern India (Bikaner).