Tumour necrosis factor, interleukin-6 and interleukin-10 are possibly involved in Plasmodium vivax-associated thrombocytopaenia in southern Pakistani population

Background

In Pakistan, Plasmodium vivax is endemic causing approximately 70% of the malaria cases. A number of haematological changes, especially thrombocytopaenia have been reported for P. vivax. Several host factors including cell-mediated immune cells, such as IL-1, IL-6 and IL-10 have been documented for P. vivax-induced thrombocytopaenia. However, study on correlation of cytokines and thrombocytopaenia in P. vivax, particularly in patients with severe signs and symptoms has not been reported from Pakistan.

Methods

A case control study to correlate TNF, IL-6 and IL-10 in healthy controls and thrombocytopaenic P. vivax-infected patients (both uncomplicated and complicated cases) from southern Pakistan was carried out during January 2009 to December 2011. One Hundred and eighty two patients presenting with microscopy-confirmed asexual P. vivax mono-infection and 100 healthy controls were enrolled in the study at Aga Khan University Hospital, Karachi. Enzyme-linked immunosorbent assay (ELISA) was performed for determination of TNF, IL-6 and IL-10 levels.

Results

Out of 182 cases, mild thrombocytopaenia (platelet count 100,000-150,000 mm³) was observed in ten (5.5%), moderate (50,000-100,000 mm³) in 93 (51.1%), and profound thrombocytopaenia (<50,000 mm³) was detected in 79 (43.4%) patients. IL-6 and IL-10 levels were found approximately three-fold higher in the mild cases compared to healthy controls. Two-fold increase in TNF and IL-10 (p < 0.0001) was observed in profound thrombocytopaenic when compared with moderate cases, while IL-6 was not found to be significantly elevated.

Conclusion

Cytokines may have a possible role in P. vivax-induced thrombocytopaenia in Pakistani population. Findings from this study give first insight from Pakistan on the role of cytokines in P.vivax-associated thrombocytopaenia. However, further studies are required to understand the relevance of cytokines in manifestations of thrombocytopaenia in P. vivax malaria.

Is Plasmodium vivax malaria a severe malaria?: a systematic review and meta-analysis

Background

Plasmodium vivax is one of the major species of malaria infecting humans. Although emphasis on P. falciparum is appropriate, the burden of vivax malaria should be given due attention. This study aimed to synthesize the evidence on severe malaria in P. vivax infection compared with that in P. falciparum infection.

Methods/Principal Findings

We searched relevant studies in electronic databases. The main outcomes required for inclusion in the review were mortality, severe malaria (SM) and severe anaemia (SA). The methodological quality of the included studies was assessed using the Newcastle-Ottawa Scale. Overall, 26 studies were included. The main meta-analysis was restricted to the high quality studies. Eight studies (n = 27490) compared the incidence of SM between P. vivax infection and P. falciparum mono-infection; a comparable incidence was found in infants (OR: 0.45, 95% CI:0.04–5.68, I²:98%), under 5 year age group (OR: 2.06, 95% CI: 0.83–5.1, I²:83%), the 5–15 year-age group (OR: 0.6, 95% CI: 0.31–1.16, I²:81%) and adults (OR: 0.83, 95% CI: 0.67–1.03, I²:25%). Six studies reported the incidences of SA in P. vivax infection and P. falciparum mono-infection; a comparable incidence of SA was found among infants (OR: 3.47, 95%:0.64–18.94, I²: 92%), the 5–15 year-age group (OR:0.71, 95% CI: 0.06–8.57, I²:82%). This was significantly lower in adults (OR:0.75, 95% CI: 0.62–0.92, I²:0%). Five studies (n = 71079) compared the mortality rate between vivax malaria and falciparum malaria. A lower rate of mortality was found in infants with vivax malaria (OR:0.61, 95% CI:0.5–0.76, I²:0%), while this was comparable in the 5–15 year- age group (OR: 0.43, 95% CI:0.06–2.91, I²:84%) and the children of unspecified-age group (OR: 0.77, 95% CI:0.59–1.01, I²:0%).

Conclusion

Overall, the present analysis identified that the incidence of SM in patients infected with P. vivax was considerable, indicating that P. vivax is a major cause of SM. Awareness of the clinical manifestations of vivax malaria should prompt early detection. Subsequent treatment and monitoring of complications can be life-saving.

Until recently, vivax malaria has received less attention than falciparum malaria and was deemed neglected. There has been a surge in studies that documented the contribution of Plasmodium vivax to severe malaria in some endemic countries such as Thailand, Brazil, Indonesia, Papua New Guinea and India. We aimed to synthesize the evidence on severe malaria in P. vivax infection compared with that in P. falciparum infection. We searched relevant studies in electronic databases. The combined results of the eight relatively high quality studies showed a comparable incidence between vivax malaria and falciparum malaria in infants, under 5 year age group, the 5–15 year age group and adults. The combined results of the six relatively high quality studies revealed a comparable incidence of severe anaemia between P. vivax infection and P. falciparum mono-infection in both the infants and the 5–15 year age group. Considering that severe malaria and deaths attributable to P. vivax is not a rare event, raised clinical awareness of the manifestations of vivax malaria in patients of any age should prompt early detection of malaria. It is likely that early detection, appropriate treatment commenced in a timely manner and close monitoring of any complications could be life-saving and contribute to the attainment of the global vision of no malaria deaths.

Plasmodium vivax malaria complicated by splenic infarct

An 11-year-old girl presented with Plasmodium vivax malaria complicated by shock and acute renal failure. The diagnosis of malaria was based on demonstration of trophozoites of P. vivax in the peripheral blood smear and a positive rapid malarial antigen test for P. vivax but negative for P. falciparum. She responded to parenteral artesunate and supportive care. During the course of her infection, she developed pain in her left hypochondrium. Ultrasonography showed multiple hypo-echoic lesions in the spleen and CT scan revealed multiple splenic infarcts. Management was restricted to close clinical monitoring and analgesia. We consider that this is the first report of splenic infarct complicating the course of childhood P. vivax malaria in the English literature. Physicians should suspect and investigate for this rare complication if a patient with malaria complains of left upper quadrant abdominal pain, pleuritic left lower chest pain and/or enlarging tender splenomegaly during the course of malaria infection.

Clinical spectrum and treatment outcome of severe malaria caused by Plasmodium vivax in 18 children from northern India

OBJECTIVE

The study was intended to document the clinical profile and treatment outcome of severe malaria caused by Plasmodium vivax (P.vivax) in children hospitalized in a tertiary care centre of northern India.

METHODS

This prospective observational study was performed among children admitted with severe malaria at a tertiary care referral hospital of northern India from January 2012 to December 2012. Information was recorded pertaining to clinical symptoms at presentation, examination findings, biochemical and hematological investigation, and treatment outcome. Presence of malarial parasite on thick and thin smears and/or positive parasite lactate dehydrogenase (p-LDH) based rapid malaria antigen test was considered diagnostic of 'malaria'. Based on the etiology, children were categorized into three groups: P.vivax, Plasmodium falciparum (P. falciparum) and mixed infection. Children diagnosed with 'severe malaria' (World Health Organization, 2000), were started on intravenous artesunate followed by artemether-lumefantrine combination.

RESULTS

Thirty-five children with a diagnosis of severe malaria were enrolled [18 (51·4%) P. vivax, nine (25·7%) mixed infection, eight (22·8%) P. falciparum]. Clinical features of severe vivax malaria (n = 18) were abnormal sensorium [9 (50%)], multiple seizures [8 (44·4%)], jaundice [5 (27·8%)], severe anaemia [5 (27·8%)], and shock [3 (16·7%)]. Two children [2/18 (11·1%)] infected with P. vivax had died of cerebral malaria, acute respiratory distress syndrome, shock, and metabolic acidosis. The clinical presentation and outcome of severe vivax malaria was found to be similar to severe malaria caused by P. falciparum and mixed infection, except for higher chances of severe anaemia among the children infected with P. falciparum (P = 0·04).

CONCLUSION

The present study highlights P. vivax as an increasingly recognized causative agent for severe malaria in children from Rohtak, with similar clinical presentation and outcome to that caused by P. falciparum.

Plasmodium vivax: clinical spectrum, risk factors and pathogenesis

Vivax malaria was historically described as 'benign tertian malaria' because individual clinical episodes were less likely to cause severe illness than Plasmodium falciparum. Despite this, Plasmodium vivax was, and remains, responsible for major morbidity and significant mortality in vivax-endemic areas. Single infections causing febrile illness in otherwise healthy individuals rarely progress to severe disease. Nevertheless, in the presence of co-morbidities, P. vivax can cause severe illness and fatal outcomes. Recurrent or chronic infections in endemic areas can cause severe anaemia and malnutrition, particularly in early childhood. Other severe manifestations include acute lung injury, acute kidney injury and uncommonly, coma. Multiorgan failure and shock are described but further studies are needed to investigate the role of bacterial and other co-infections in these syndromes. In pregnancy, P. vivax infection can cause maternal anaemia, miscarriage, low birth weight and congenital malaria. Compared to P. falciparum, P. vivax has a greater capacity to elicit an inflammatory response, resulting in a lower pyrogenic threshold. Conversely, cytoadherence of P. vivax to endothelial cells is less frequent and parasite sequestration is not thought to be a significant cause of severe illness in vivax malaria. With a predilection for young red cells, P. vivax does not result in the high parasite biomass associated with severe disease in P. falciparum, but a four to fivefold greater removal of uninfected red cells from the circulation relative to P. falciparum is associated with a similar risk of severe anaemia. Mechanisms underlying the pathogenesis of severe vivax syndromes remain incompletely understood.

Pediatric cerebral malaria: a scourge of Africa

Cerebral malaria, defined as an otherwise unexplained coma in a patient with Plasmodium falciparum parasitemia, affects up to 1 million people per year, the vast majority of them being children living in sub-Saharan Africa. Despite optimal treatment, this condition kills 15% of those affected and leaves 30% of survivors with neurologic sequelae. The clinical diagnosis is hampered by its poor specificity, but the presence or absence of a malarial retinopathy in cerebral malaria has proven to be important in the differentiation of underlying coma etiology. Both antimalarials and intense supportive care are necessary for optimal treatment. As of yet, clinical trials of adjunctive therapies have not improved the high rates of mortality and morbidity. Survivors are at high risk of neurologic sequelae including epilepsy, neurodisabilities and cognitive–behavioral problems. The neuroanatomic and functional bases of these sequelae are being elucidated. Although adjunctive therapy trials continue, the best hope for African children may lie in disease prevention. Strategies include bednets, chemoprophylaxis and vaccine development.

Changing profile of severe malaria in north Indian children

OBJECTIVE

To look for profile of severe malaria and contribution of vivax infection to malarial morbidity in North Indian children.

METHODS

Detailed clinical, biochemical and hematological characteristics of children hospitalized with severe malaria over last 3 y were recorded. Presence of malarial parasite on peripheral smear and/or positive antigen test was considered as diagnostic for malaria.

RESULTS

A total of 131(55.3%) patients with Plasmodium vivax (Pv), 79 (33.3%) with Plasmodium falciparum (Pf) and 27 (11.4%) with mixed infections were admitted. Cerebral malaria, severe anemia and shock were significantly more frequently observed in Pf group, while hepatic, renal, respiratory, and bleeding complications were more commonly seen in Pv patients. Malaria mortality was highest in mixed infection (11.1%), followed by Pf (7.6%) and Pv (3%) group.

CONCLUSIONS

Severe and fatal vivax malaria is an emerging recognized entity and challenges the perception of Pv as a benign disease. Further clinical studies and molecular research is required to understand emergence of severe malaria in vivax mono-infection.

Prospects and Pitfalls of Pregnancy-Associated Malaria Vaccination Based on the Natural Immune Response to Plasmodium falciparum VAR2CSA-Expressing Parasites

Pregnancy-associated malaria, a manifestation of severe malaria, is the cause of up to 200,000 infant deaths a year, through the effects of placental insufficiency leading to growth restriction and preterm delivery. Development of a vaccine is one strategy for control. Plasmodium falciparum-infected red blood cells accumulate in the placenta through specific binding of pregnancy-associated parasite variants that express the VAR2CSA antigen to chondroitin sulphate A on the surface of syncytiotrophoblast cells. Parasite accumulation, accompanied by an inflammatory infiltrate, disrupts the cytokine balance of pregnancy with the potential to cause placental damage and compromise foetal growth. Multigravid women develop immunity towards VAR2CSA-expressing parasites in a gravidity-dependent manner which prevents unfavourable pregnancy outcomes. Although current vaccine design, targeting VAR2CSA antigens, has succeeded in inducing antibodies artificially, this candidate may not provide protection during the first trimester and may only protect those women living in areas endemic for malaria. It is concluded that while insufficient information about placental-parasite interactions is presently available to produce an effective vaccine, incremental progress is being made towards achieving this goal.

Vivax malaria in Mauritania includes infection of a Duffy-negative individual

Background

Duffy blood group polymorphisms are important in areas where Plasmodium vivax is present because this surface antigen is thought to act as a key receptor for this parasite. In the present study, Duffy blood group genotyping was performed in febrile uninfected and P. vivax-infected patients living in the city of Nouakchott, Mauritania.

Methods

Plasmodium vivax was identified by real-time PCR. The Duffy blood group genotypes were determined by standard PCR followed by sequencing of the promoter region and exon 2 of the Duffy gene in 277 febrile individuals. Fisher's exact test was performed in order to assess the significance of variables.

Results

In the Moorish population, a high frequency of the FYB^ES/FYB^ES genotype was observed in uninfected individuals (27.8%), whereas no P. vivax-infected patient had this genotype. This was followed by a high level of FYA/FYB, FYB/FYB, FYB/FYB^ES and FYA/FYB^ES genotype frequencies, both in the P. vivax-infected and uninfected patients. In other ethnic groups (Poular, Soninke, Wolof), only the FYB^ES/FYB^ES genotype was found in uninfected patients, whereas the FYA/FYB^ES genotype was observed in two P. vivax-infected patients. In addition, one patient belonging to the Wolof ethnic group presented the FYB^ES/FYB^ES genotype and was infected by P. vivax.

Conclusions

This study presents the Duffy blood group polymorphisms in Nouakchott City and demonstrates that in Mauritania, P. vivax is able to infect Duffy-negative patients. Further studies are necessary to identify the process that enables this Duffy-independent P. vivax invasion of human red blood cells.

Thrombocytopenia in childhood malaria with special reference to P. vivax monoinfection: A study from Bikaner (Northwestern India)

Thrombocytopenia is commonly seen in Plasmodium vivax malaria, but its prognostic value has not been addressed in children. This prospective study included 676 admitted children of malaria [Plasmodium falciparum (Pf) monoinfection 262, Plasmodium vivax (Pv) monoinfection 380, and mixed (Pf + Pv) infection 34], in which thrombocytopenia (platelet count <150 × 10(3)/mm(3) on admission) was found in 442 (65.38%) children [Pf monoinfection 55.3% (145/262), Pv monoinfection 73.16% (278/380), and mixed infection 55.88% (19/34)]. The association of thrombocytopenia was statistically significant with Pv monoinfection [73.16% (278/380)] in comparison to either Pf monoinfection [55.34% (145/262); odds ratio (OR) = 2.199 (95% confidence interval (CI) 1.577-3.068), p < 0.0001] or mixed infection [55.88% (19/34); OR = 2.152 (95%CI 1.054-4.394), p = 0.032]. In Pv monoinfection, thrombocytopenia was highest in 0-5 years age group and subsequently decreased with advancing age, whereas in Pf monoinfection it was reverse. Severe thrombocytopenia (platelet count <20 × 10(3)/mm(3)) was present in 16.52% (73/442) children [Pv monoinfection 21.58% (60/278) and Pf monoinfection 8.97% (13/145)]. The risk of developing severe thrombocytopenia was also highest in Pv monoinfection [15.79% (60/380)] in comparison to Pf monoinfection [10.59% (13/262); OR = 3.591 (95%CI 1.928-6.690), p < 0.0001]. Bleeding manifestations were associated in 21.27% (94/442) children [Pf monoinfection 9.92% (26/262), Pv monoinfection 16.58% (63/380), and mixed malaria 14.71% (5/34)]. All the children having bleeding manifestations had thrombocytopenia but low platelet counts were not always associated with abnormal bleeding. The association of severe malaria was significantly more among children having Pv monoinfection with platelet counts <20 × 10(3)/mm(3) [OR = 2.569 (95%CI 1.196-5.517), p < 0.014] with specificity of 88.3% and positive predictive value of 85%. Till today, thrombocytopenia is not included in severe malaria criterion described by WHO, but when platelet counts <20 × 103/mm(3), we advocate it to include as one of the severe malaria criteria.

Coma associated with microscopy-diagnosed Plasmodium vivax: a prospective study in Papua, Indonesia

BACKGROUND

Coma complicates Plasmodium falciparum infection but is uncommonly associated with P. vivax. Most series of vivax coma have been retrospective and have not utilized molecular methods to exclude mixed infections with P. falciparum.

METHODS

We prospectively enrolled patients hospitalized in Timika, Indonesia, with a Glasgow Coma Score (GCS) ≤10 and P. vivax monoinfection on initial microscopy over a four year period. Hematological, biochemical, serological, radiological and cerebrospinal fluid (CSF) examinations were performed to identify other causes of coma. Repeat microscopy, antigen detection and polymerase chain reaction (PCR) were performed to exclude infections with other Plasmodium species.

RESULTS

Of 24 patients fulfilling enrolment criteria, 5 had clear evidence for other non-malarial etiologies. PCR demonstrated 10 mixed infections and 3 P. falciparum monoinfections. 6 (25%) patients had vivax monoinfection and no apparent alternative cause, with a median GCS of 9 (range 8-10) and a median coma duration of 42 (range 36-48) hours. CSF leukocyte counts were <10/ul (n=3); 2 of the 3 patients without CSF examination recovered with antimalarial therapy alone. One patient had a tremor on discharge consistent with a post-malarial neurological syndrome. No patient had other organ dysfunction. The only death was associated with pure P. falciparum infection by PCR. Vivax monoinfection-associated risk of coma was estimated at 1 in 29,486 clinical vivax infections with no deaths. In comparison, the risk of falciparum-associated coma was estimated at 1 in 1,276 clinical infections with an 18.5% mortality rate.

CONCLUSIONS

P. vivax-associated coma is rare, occurring 23 times less frequently than that seen with falciparum malaria, and is associated with a high proportion of non-malarial causes and mixed infections using PCR. The pathogenesis of coma associated with vivax malaria, particularly the role of comorbidities, is uncertain and requires further investigation.

Plasmodium vivax malaria: is it actually benign?

Plasmodium vivax (Pv) malaria is being increasingly recognized as a cause of severe malaria in children.

OBJECTIVES

To describe the various severe manifestations associated with vivax malaria by retrospective analysis of records.

METHODS

Children between the ages of 0 and 18 years with a confirmed diagnosis of Pv malaria monoinfection done by peripheral blood film (PBF) and/or rapid diagnostic test (RDT) admitted between June and September 2009 were included. Their clinical, hematological and biochemical manifestations were analyzed.

RESULTS

Twenty-three patients of Pv malaria were retrospectively analyzed. Thrombocytopenia was present in 22 (96%) patients with counts less than 50,000/ μL in 9 patients. Severe anemia (hgb<5mg/dl) was present in 8 (34%) patients. Cerebral malaria was present in 3 patients. Liver enzymes were elevated (>3 times normal) in 4 (17.3%) patients while jaundice (bilirubin>2.5mg/dl) was present in 2 patients (total bilirubin 5.2mg/dl and 14.3mg/dl). Renal dysfunction (creatinine>3mg/dl) was present in 6 (26%) patients with 2 patients showing severely deranged renal functions (blood urea 168 mg/dl, 222 mg/dl and serum creatinine 5.0mg/dl, 5.6 mg/dl, respectively). Hypernatremia was present in one patient. One patient expired within 12h of presentation because of severely deranged hepatic and renal dysfunction.

CONCLUSION

Pv malaria can lead to unusual and fatal complications. All new guidelines should include "Severe Vivax malaria" as a clinical entity. Further research into the etiopathogenesis and treatment would be important.

Pyronaridine-artesunate versus chloroquine in patients with acute Plasmodium vivax malaria: a randomized, double-blind, non-inferiority trial

Background

New antimalarials are needed for P. vivax and P. falciparum malaria. This study compared the efficacy and safety of pyronaridine-artesunate with that of chloroquine for the treatment of uncomplicated P. vivax malaria.

Methods and Findings

This phase III randomized, double-blind, non-inferiority trial included five centers across Cambodia, Thailand, India, and Indonesia. In a double-dummy design, patients (aged >3–≤60 years) with microscopically confirmed P. vivax mono-infection were randomized (1∶1) to receive pyronaridine-artesunate (target dose 7.2∶2.4 mg/kg to 13.8∶4.6 mg/kg) or chloroquine (standard dose) once daily for three days. Each treatment group included 228 randomized patients. Outcomes for the primary endpoint, Day-14 cure rate in the per-protocol population, were 99.5%, (217/218; 95%CI 97.5, 100) with pyronaridine-artesunate and 100% (209/209; 95%CI 98.3, 100) with chloroquine. Pyronaridine was non-inferior to chloroquine: treatment difference −0.5% (95%CI −2.6, 1.4), i.e., the lower limit of the 2-sided 95%CI for the treatment difference was greater than −10%. Pyronaridine-artesunate cure rates were non-inferior to chloroquine for Days 21, 28, 35 and 42. Parasite clearance time was shorter with pyronaridine-artesunate (median 23.0 h) versus chloroquine (32.0 h; p<0.0001), as was fever clearance time (median 15.9 h and 23.8 h, respectively; p = 0.0017). Kaplan-Meier estimates of post-baseline P. falciparum infection incidence until Day 42 were 2.5% with pyronaridine-artesunate, 6.1% with chloroquine (p = 0.048, log-rank test). Post-baseline P. vivax or P. falciparum infection incidence until Day 42 was 6.8% and 12.4%, respectively (p = 0.022, log rank test). There were no deaths. Adverse events occurred in 92/228 (40.4%) patients with pyronaridine-artesunate and 72/228 (31.6%) with chloroquine. Mild and transient increases in hepatic enzymes were observed for pyronaridine-artesunate.

Conclusion

Pyronaridine-artesunate efficacy in acute uncomplicated P. vivax malaria was at least that of chloroquine. As pyronaridine-artesunate is also efficacious against P. falciparum malaria, this combination has potential utility as a global antimalarial drug.

Trial registration

Clinicaltrials.gov NCT00440999

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

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 (> or =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.