METHODS: Study participants included 73 uncomplicated malaria patients with PCR species confirmation: 50 P. knowlesi, 20 P. falciparum and 3 P. vivax. Nineteen malaria-negative, non-endemic area controls were also included. The sensitivity of the Eiken Loopamp™ MALARIA Pan Detection kit (Pan LAMP) for detecting each Plasmodium species was evaluated. Sensitivity and specificity of the Eiken Loopamp™ MALARIA Pf Detection kit (Pf LAMP) for P. falciparum were also determined. The limit of detection for each LAMP assay was evaluated, with results compared to PCR. All P. knowlesi patients were also tested by CareStart™ (Pf/VOM) and OptiMAL-IT™ (Pan/Pf) RDTs.
RESULTS: The sensitivity of the Pan LAMP assay was 100% for P. knowlesi (95% CI 92.9-100), P. falciparum (95% CI 83.2-100), and P. vivax (95% CI 29.2-100). The Pf LAMP was 100% sensitive and specific for P. falciparum detection, with all P. knowlesi samples having a negative reaction. LAMP sensitivity was superior to both RDTs, with only 10 and 28% of P. knowlesi samples testing positive to CareStart™ and OptiMAL-IT™, respectively. Limit of detection using the Pan LAMP for both P. knowlesi and P. vivax was 2 parasites/μL, comparable to PCR. For P. falciparum both the Pan LAMP and Pf LAMP demonstrated a limit of detection of 20 parasites/μL.
CONCLUSIONS: The Eiken Loopamp™ MALARIA Pan Detection kit is sensitive for detection of P. knowlesi in low parasitaemia clinical infections, as well as P. falciparum and P. vivax. However, a P. knowlesi-specific field assay in a simpler format would assist correct species identification and initiation of optimal treatment for all malaria patients.
METHODS: Two real-time PCR methods currently used in Sabah for confirmatory malaria diagnosis and surveillance reporting were evaluated: the QuantiFast™ Multiplex PCR kit (Qiagen, Germany) targeting the P. knowlesi 18S SSU rRNA; and the abTES™ Malaria 5 qPCR II kit (AITbiotech, Singapore), with an undisclosed P. knowlesi gene target. Diagnostic accuracy was evaluated using 52 P. knowlesi, 25 Plasmodium vivax, 21 Plasmodium falciparum, and 10 Plasmodium malariae clinical isolates, and 26 malaria negative controls, and compared against a validated reference nested PCR assay. The limit of detection (LOD) for each PCR method and Plasmodium species was also evaluated.
RESULTS: The sensitivity of the QuantiFast™ and abTES™ assays for detecting P. knowlesi was comparable at 98.1% (95% CI 89.7-100) and 100% (95% CI 93.2-100), respectively. Specificity of the QuantiFast™ and abTES™ for P. knowlesi was high at 98.8% (95% CI 93.4-100) for both assays. The QuantiFast™ assay demonstrated falsely-positive mixed Plasmodium species at low parasitaemias in both the primary and LOD analysis. Diagnostic accuracy of both PCR kits for detecting P. vivax, P. falciparum, and P. malariae was comparable to P. knowlesi. The abTES™ assay demonstrated a lower LOD for P. knowlesi of ≤ 0.125 parasites/µL compared to QuantiFast™ with a LOD of 20 parasites/µL. Hospital microscopy demonstrated a sensitivity of 78.8% (95% CI 65.3-88.9) and specificity of 80.4% (95% CI 67.6-89.8) compared to reference PCR for detecting P. knowlesi.
CONCLUSION: The QuantiFast™ and abTES™ commercial PCR kits performed well for the accurate detection of P. knowlesi infections. Although the QuantiFast™ kit is cheaper, the abTES™ kit demonstrated a lower LOD, supporting its use as a second-line referral-laboratory diagnostic tool in Sabah, Malaysia.
METHODS: A cross-sectional study was carried out from 1 April 2018 to 31 January 2019 in Jazan region, southwestern Saudi Arabia, which targeted febrile individuals attending hospitals and primary healthcare centres. Participants' demographic data were collected, including age, gender, nationality, and residence. Moreover, association of climatic variables with the monthly autochthonous malaria cases reported during the period of 2010-2017 was retrospectively analysed.
RESULTS: A total of 1124 febrile subjects were found to be positive for malaria during the study period. Among them, 94.3 and 5.7% were infected with Plasmodium falciparum and Plasmodium vivax, respectively. In general, subjects aged 18-30 years and those aged over 50 years had the highest (42.7%) and lowest (5.9%) percentages of malaria cases. Similarly, the percentage of malaria-positive cases was higher among males than females (86.2 vs 13.8%), among non-Saudi compared to Saudi subjects (70.6 vs 29.4%), and among patients residing in rural rather than in urban areas (89.8 vs 10.2%). A total of 407 autochthonous malaria cases were reported in Jazan region between 2010 and 2017. Results of zero-inflated negative binomial regression analysis showed that monthly average temperature and relative humidity were the significant climatic determinants of autochthonous malaria in the region.
CONCLUSION: Malaria remains a public health problem in most governorates of Jazan region. The identification and monitoring of malaria transmission hotspots and predictors would enable control efforts to be intensified and focused on specific areas and therefore expedite the elimination of residual malaria from the whole region.
METHODS: A total of 3002 blood samples on filter paper were collected from 555 inhabitants of 8 longhouses with recently reported knowlesi malaria cases in the Betong Division of Sarawak, Malaysian Borneo. Each longhouse was visited bimonthly for a total of 10 times during a 21-month study period (Jan 2014-Oct 2015). DNA extracted from blood spots were examined by a nested PCR assay for Plasmodium and positive samples were then examined by nested PCR assays for Plasmodium falciparum, Plasmodium vivax, Plasmodium malariae, Plasmodium ovale, Plasmodium knowlesi, Plasmodium cynomolgi and Plasmodium inui. Blood films of samples positive by PCR were also examined by microscopy.
RESULTS: Genus-specific PCR assay detected Plasmodium DNA in 9 out of 3002 samples. Species-specific PCR identified 7 P. knowlesi and one P. vivax. Malaria parasites were observed in 5 thick blood films of the PCR positive samples. No parasites were observed in blood films from one knowlesi-, one vivax- and the genus-positive samples. Only one of 7 P. knowlesi-infected individual was febrile and had sought medical treatment at Betong Hospital the day after sampling. The 6 knowlesi-, one vivax- and one Plasmodium-infected individuals were afebrile and did not seek any medical treatment.
CONCLUSIONS: Asymptomatic human P. knowlesi and P. vivax malaria infections, but not P. cynomolgi and P. inui infections, are occurring within communities affected with malaria.
MAIN BODY: A systematic review and meta-analysis of the available literature on thrombocytopaenia in P. vivax malaria patients was undertaken. Relevant studies in health-related electronic databases were identified and reviewed. The Preferred Reporting Items for Systematic Reviews and Meta-Analyses guidelines were followed. Fifty-eight observational studies (n = 29 664) were included in the current review. Severe thrombocytopaenia (vivax infection. A meta-analysis of 11 observational studies showed an equal risk of developing severe/very severe thrombocytopaenia between the patients with P. vivax malaria and those with P. falciparum malaria (OR: 1.98, 95% CI: 0.92-4.25). This indicates that thrombocytopaenia is as equally a common manifestation in P. vivax and P. falciparum malaria patients. One study showed a higher risk of developing very severe thrombocytopaenia in children with severe P. vivax malaria than with severe P. falciparum malaria (OR: 2.80, 95% CI: 1.48-5.29). However, a pooled analysis of two studies showed an equal risk among adult severe cases (OR: 1.19, 95% CI: 0.51-2.77). This indicates that the risk of developing thrombocytopaenia in P. vivax malaria can vary with immune status in both children and adults. One study reported higher levels of urea and serum bilirubin in patients with P. vivax malaria and severe thrombocytopaenia compared with patients mild thrombocytopaenia or no thrombocytopaenia, (P vivax patients and severe P. falciparum patients (P = 0.09). This implied that both P. vivax and P. falciparum infections could present with bleeding episodes, if there had been a change in platelet counts in the infected patients. A pooled analysis of another two studies showed an equal risk of mortality with severe thrombocytopaenia in both P. vivax and P. falciparum malaria patients (OR: 1.16, 95% CI: 0.30-4.60). However, due to the low number of studies with small sample sizes within the subset of studies that provided clinically relevant information, our confidence in the estimates is limited.
CONCLUSION: The current review has provided some evidence of the clinical relevance of severe thrombocytopaenia in P. vivax malaria. To substantiate these findings, there is a need for well designed, large-scale, prospective studies among patients infected with P. vivax. These should include patients from different countries and epidemiological settings with various age and gender groups represented.
METHODS: Patient data was obtained retrospectively through the Ministry of Health, Malaysia, from 2011 to 2016. Patients with incomplete data were excluded. A total of 2044 clinical P. vivax malaria cases treated with primaquine were included. Data collected were patient, disease, and treatment characteristics. Two-thirds of the cases (n = 1362) were used to develop a clinical risk score, while the remaining third (n = 682) was used for validation.
RESULTS: Using multivariate analysis, age (p = 0.03), gametocyte sexual count (p = 0.04), indigenous transmission (p = 0.04), type of treatment (p = 0.12), and incomplete primaquine treatment (p = 0.14) were found to be predictors of recurrence after controlling for other confounding factors; these predictors were then used in developing the final model. The beta-coefficient values were used to develop a clinical scoring tool to predict possible recurrence. The total scores ranged between 0 and 8. A higher score indicated a higher risk for recurrence (odds ratio [OR]: 1.971; 95% confidence interval [CI]: 1.562-2.487; p ≤ 0.001). The area under the receiver operating characteristic (ROC) curve of the developed (n = 1362) and validated model (n = 682) was of good accuracy (ROC: 0.728, 95% CI: 0.670-0.785, p value
METHODS: In 2013, a total of 1744 dried blood spots (DBS) were obtained from residents of 8 longhouses who appeared healthy. Subsequently, 251 venous blood samples were collected from residents of 2 localities in 2014 based on the highest number of submicroscopic cases from prior findings. Thin and thick blood films were prepared from blood obtained from all participants in this study. Microscopic examination were carried out on all samples and a nested and nested multiplex PCR were performed on samples collected in 2013 and 2014 respectively.
RESULTS: No malaria parasites were detected in all the Giemsa-stained blood films. However, of the 1744 samples, 29 (1.7%) were positive for Plasmodium vivax by PCR. Additionally, of the 251 samples, the most prevalent mono-infection detected by PCR was Plasmodium falciparum 50 (20%), followed by P. vivax 39 (16%), P. knowlesi 9 (4%), and mixed infections 20 (8%).
CONCLUSIONS: This research findings conclude evidence of Plasmodium by PCR, among samples previously undetectable by routine blood film microscopic examination, in local ethnic minority who are clinically healthy. SMM in Belaga district is attributed not only to P. vivax, but also to P. falciparum and P. knowlesi. In complementing efforts of programme managers, there is a need to increase surveillance for SMM nationwide to estimate the degree of SMM that warrant measures to block new transmission of malaria.
METHODS: In a systematic study of the presentation and course of patients with acute P. knowlesi infection, clinical and laboratory data were collected from previously untreated, nonpregnant adults admitted to the hospital with polymerase chain reaction-confirmed acute malaria at Kapit Hospital (Sarawak, Malaysia) from July 2006 through February 2008.
RESULTS: Of 152 patients recruited, 107 (70%) had P. knowlesi infection, 24 (16%) had Plasmodium falciparum infection, and 21 (14%) had Plasmodium vivax. Patients with P. knowlesi infection presented with a nonspecific febrile illness, had a baseline median parasitemia value at hospital admission of 1387 parasites/microL (interquartile range, 6-222,570 parasites/microL), and all were thrombocytopenic at hospital admission or on the following day. Most (93.5%) of the patients with P. knowlesi infection had uncomplicated malaria that responded to chloroquine and primaquine treatment. Based on World Health Organization criteria for falciparum malaria, 7 patients with P. knowlesi infection (6.5%) had severe infections at hospital admission. The most frequent complication was respiratory distress, which was present at hospital admission in 4 patients and developed after admission in an additional 3 patients. P. knowlesi parasitemia at hospital admission was an independent determinant of respiratory distress, as were serum creatinine level, serum bilirubin, and platelet count at admission (p < .002 for each). Two patients with knowlesi malaria died, representing a case fatality rate of 1.8% (95% confidence interval, 0.2%-6.6%).
CONCLUSIONS: Knowlesi malaria causes a wide spectrum of disease. Most cases are uncomplicated and respond promptly to treatment, but approximately 1 in 10 patients develop potentially fatal complications.