Displaying publications 41 - 60 of 256 in total

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  1. Bronner U, Divis PC, Färnert A, Singh B
    Malar J, 2009 Jan 16;8:15.
    PMID: 19146706 DOI: 10.1186/1475-2875-8-15
    Plasmodium knowlesi is typically found in nature in macaques and has recently been recognized as the fifth species of Plasmodium causing malaria in human populations in south-east Asia. A case of knowlesi malaria is described in a Swedish man, who became ill after returning from a short visit to Malaysian Borneo in October 2006. His P. knowlesi infection was not detected using a rapid diagnostic test for malaria, but was confirmed by PCR and molecular characterization. He responded rapidly to treatment with mefloquine. Evaluation of rapid diagnostic kits with further samples from knowlesi malaria patients are necessary, since early identification and appropriate anti-malarial treatment of suspected cases are essential due to the rapid growth and potentially life-threatening nature of P. knowlesi. Physicians should be aware that knowlesi infection is an important differential diagnosis in febrile travellers, with a recent travel history to forested areas in south-east Asia, including short-term travellers who tested negative with rapid diagnostic tests.
    Matched MeSH terms: Plasmodium knowlesi/genetics; Plasmodium knowlesi/isolation & purification*
  2. Brown R, Chua TH, Fornace K, Drakeley C, Vythilingam I, Ferguson HM
    PLoS Negl Trop Dis, 2020 09;14(9):e0008617.
    PMID: 32886679 DOI: 10.1371/journal.pntd.0008617
    The zoonotic malaria parasite, Plasmodium knowlesi, is now a substantial public health problem in Malaysian Borneo. Current understanding of P. knowlesi vector bionomics and ecology in Sabah comes from a few studies near the epicentre of human cases in one district, Kudat. These have incriminated Anopheles balabacensis as the primary vector, and suggest that human exposure to vector biting is peri-domestic as well as in forest environments. To address the limited understanding of vector ecology and human exposure risk outside of Kudat, we performed wider scale surveillance across four districts in Sabah with confirmed transmission to investigate spatial heterogeneity in vector abundance, diversity and infection rate. Entomological surveillance was carried out six months after a cross-sectional survey of P. knowlesi prevalence in humans throughout the study area; providing an opportunity to investigate associations between entomological indicators and infection. Human-landing catches were performed in peri-domestic, farm and forest sites in 11 villages (3-4 per district) and paired with estimates of human P. knowlesi exposure based on sero-prevalence. Anopheles balabacensis was present in all districts but only 6/11 villages. The mean density of An. balabacensis was relatively low, but significantly higher in farm (0.094/night) and forest (0.082/night) than peri-domestic areas (0.007/night). Only one An. balabacensis (n = 32) was infected with P. knowlesi. Plasmodium knowlesi sero-positivity in people was not associated with An. balabacensis density at the village-level however post hoc analyses indicated the study had limited power to detect a statistical association due low vector density. Wider scale sampling revealed substantial heterogeneity in vector density and distribution between villages and districts. Vector-habitat associations predicted from this larger-scale surveillance differed from those inferred from smaller-scale studies in Kudat; highlighting the importance of local ecological context. Findings highlight potential trade-offs between maximizing temporal versus spatial breadth when designing entomological surveillance; and provide baseline entomological and epidemiological data to inform future studies of entomological risk factors for human P. knowlesi infection.
    Matched MeSH terms: Plasmodium knowlesi/isolation & purification*
  3. Byrne I, Aure W, Manin BO, Vythilingam I, Ferguson HM, Drakeley CJ, et al.
    Sci Rep, 2021 Jun 03;11(1):11810.
    PMID: 34083582 DOI: 10.1038/s41598-021-90893-1
    Land-use changes, such as deforestation and agriculture, can influence mosquito vector populations and malaria transmission. These land-use changes have been linked to increased incidence in human cases of the zoonotic malaria Plasmodium knowlesi in Sabah, Malaysian Borneo. This study investigates whether these associations are partially driven by fine-scale land-use changes creating more favourable aquatic breeding habitats for P. knowlesi anopheline vectors. Using aerial remote sensing data, we developed a sampling frame representative of all land use types within a major focus of P. knowlesi transmission. From 2015 to 2016 monthly longitudinal surveys of larval habitats were collected in randomly selected areas stratified by land use type. Additional remote sensing data on environmental variables, land cover and landscape configuration were assembled for the study site. Risk factor analyses were performed over multiple spatial scales to determine associations between environmental and spatial variables and anopheline larval presence. Habitat fragmentation (300 m), aspect (350 m), distance to rubber plantations (100 m) and Culex larval presence were identified as risk factors for Anopheles breeding. Additionally, models were fit to determine the presence of potential larval habitats within the areas surveyed and used to generate a time-series of monthly predictive maps. These results indicate that land-use change and topography influence the suitability of larval habitats, and may partially explain the link between P. knowlesi incidence and deforestation. The predictive maps, and identification of the spatial scales at which risk factors are most influential may aid spatio-temporally targeted vector control interventions.
    Matched MeSH terms: Plasmodium knowlesi*
  4. CHIN W, CONTACOS PG, COATNEY GR, KIMBALL HR
    Science, 1965 Aug 20;149(3686):865.
    PMID: 14332847 DOI: 10.1126/science.149.3686.865
    A quotidian-type parasite, Plasmodium knowlesi, has been found as a natural infection in man. The infection was acquired by a white male during a short visit to peninsular Malaysia. This occurrence constitutes the first proof that simian malaria is a true zoonosis.
    Matched MeSH terms: Plasmodium knowlesi*
  5. Cahyo Budiman, Carlmond Goh Kah Wun, Lee, Ping Chin, Rafida Razali, Thean, Chor Leow
    MyJurnal
    FK506-binding protein35 of Plasmodium knowlesi (Pk-FKBP35) is a member of peptidyl prolyl cis-trans isomerase (PPIase) and is considered as a promising avenue of antimalarial drug target development. This protein is organized into the N-terminal domain responsible for PPIase catalytic activity followed and the tetratricopeptide repeat domain for its dimerization. The protease-coupling and protease-free assays are known to be the common methods for investigating the catalytic properties of PPIase. Earlier, the protease-coupling assay was used to confirm the catalytic activity of Pk-FKBP35 in accelerating cis-trans isomerization of the peptide substrate. This report is aimed to re-assess the catalytic and substrate specificity of Pk-FKBP35 using an alternative method of a protease-free assay. The result indicated that while Pk-FKBP35 theoretically contained many possible cleavage sites of chymotrypsin, experimentally, the catalytic domain was relatively stable from chymotrypsin. Furthermore, under protease-free assay, Pk-FKBP35 also demonstrated remarkable PPIase catalytic activity with kcat/KM of 4.5 + 0.13 × 105 M−1 s−1, while the kcat/KM of active site mutant of D55A is 0.81 + 0.05 × 105 M−1 s−1. These values were considered comparable to kcat/KM obtained from the protease-coupling assay. Interestingly, the substrate specificities of Pk-FKBP35 obtained from both methods are also similar, with the preference of Pk-FKBP35 towards Xaa at P1 position was Leu>Phe>Lys>Trp>Val>Ile>His>Asp>Ala>Gln>Glu. Altogether, we proposed that protease-free and protease-coupling assays arereliable for Pk-FKBP35.
    Matched MeSH terms: Plasmodium knowlesi
  6. Chang CY, Pui WC, Kadir KA, Singh B
    Malar J, 2018 Dec 04;17(1):448.
    PMID: 30509259 DOI: 10.1186/s12936-018-2600-2
    BACKGROUND: Plasmodium knowlesi, a malaria parasite typically found in long-tailed and pig-tailed macaques, is the most common cause of human malaria in Malaysian Borneo. Infections in humans result in a spectrum of disease, including fatal outcomes. Spontaneous splenic rupture is a rare, but severe complication of malaria and has not been reported previously for knowlesi malaria.

    CASE PRESENTATION: A 46-year-old man presented with fever and acute surgical abdomen with concomitant P. knowlesi malaria infection at Kapit Hospital. He was in compensated shock upon arrival to the hospital. He had generalized abdominal tenderness, maximal at the epigastric region. Bedside focused abdominal ultrasonography revealed free fluid in the abdomen. He underwent emergency exploratory laparotomy in view of haemodynamic instability and worsening peritonism. Intraoperatively, haemoperitoneum and bleeding from the spleen was noted. Splenectomy was performed. Histopathological examination findings were suggestive of splenic rupture and presence of malarial pigment. Analysis of his blood sample by nested PCR assays confirmed P. knowlesi infection. The patient completed a course of anti-malarial treatment and recovered well post-operation.

    CONCLUSIONS: Spontaneous splenic rupture is a rare complication of malaria. This is the first reported case of splenic rupture in P. knowlesi malaria infection. Detection of such a complication requires high index of clinical suspicion and is extremely challenging in hospitals with limited resources.

    Matched MeSH terms: Plasmodium knowlesi*
  7. Chang CY
    J Vector Borne Dis, 2023;60(4):432-434.
    PMID: 38174522 DOI: 10.4103/0972-9062.374238
    BACKGROUND & OBJECTIVES: Severe malaria is a medical emergency and can lead to severe complications and death if not treated promptly and appropriately. Along with Plasmodium falciparum, P. knowlesi is increasingly recognised as a significant cause of fatal and severe malaria.

    METHODS: We performed a retrospective review on 54 cases of severe malaria in a district hospital in Kapit, Sarawak, from January 2018 to May 2019. The patients' demographics, clinical features, complications based on organ involvement, and treatment outcomes were examined.

    RESULTS: There were 54 cases of severe malaria, with the majority being male (70%) and between the ages of 40 and 49 (26%). All patients with severe malaria were febrile or had a history of pyrexia except for one patient. P. knowlesi (81.5%) was the most common species causing severe malaria in our study, followed by P. falciparum (13%), and P. vivax (5.5%). There were no cases of severe malaria caused by P. ovale or P. malariae. Hyperparasitaemia was present in 76% of patients and the median parasitemia value at hospital admission was 33,944 parasites/μL (interquartile range: 19,920-113,285 parasites/μL). Circulatory shock was observed in 17 patients (31.5%). There were eight patients with acute renal failure and six patients with respiratory distress. One patient died as a result of severe malaria with multiorgan involvement (1.9% fatality rate).

    INTERPRETATION & CONCLUSION: P. knowlesi is the most common cause of severe malaria in Kapit, Sarawak, Malaysia. Recognizing symptoms of severe malaria and prompt administration of antimalarial are critical for good clinical outcomes.

    Matched MeSH terms: Plasmodium knowlesi*
  8. Chaturvedi R, Biswas S, Bisht K, Sharma A
    Parasitology, 2023 Nov;150(13):1167-1177.
    PMID: 37929579 DOI: 10.1017/S003118202300077X
    Of the 5 human malarial parasites, Plasmodium falciparum and Plasmodium vivax are the most prevalent species globally, while Plasmodium malariae, Plasmodium ovale curtisi and Plasmodium ovale wallikeri are less prevalent and typically occur as mixed-infections. Plasmodium knowlesi, previously considered a non-human primate (NHP) infecting species, is now a cause of human malaria in Malaysia. The other NHP Plasmodium species, Plasmodium cynomolgi, Plasmodium brasilianum, Plasmodium inui, Plasmodium simium, Plasmodium coatneyi and Plasmodium fieldi cause malaria in primates, which are mainly reported in southeast Asia and South America. The non-knowlesi NHP Plasmodium species also emerged and were found to cross-transmit from their natural hosts (NHP) – to human hosts in natural settings. Here we have reviewed and collated data from the literature on the NHPs-to-human-transmitting non-knowlesi Plasmodium species. It was observed that the natural transmission of these NHP parasites to humans had been reported from 2010 onwards. This study shows that: (1) the majority of the non-knowlesi NHP Plasmodium mixed species infecting human cases were from Yala province of Thailand; (2) mono/mixed P. cynomolgi infections with other human-infecting Plasmodium species were prevalent in Malaysia and Thailand and (3) P. brasilianum and P. simium were found in Central and South America.
    Matched MeSH terms: Plasmodium knowlesi*
  9. Che Rahim MJ, Mohammad N, Besari AM, Wan Ghazali WS
    BMJ Case Rep, 2017 Feb 20;2017.
    PMID: 28219910 DOI: 10.1136/bcr-2016-218480
    We report a case of severe Plasmodium knowlesi and dengue coinfection in a previously healthy 59-year-old Malay man who presented with worsening shortness of breath, high-grade fever with chills and rigors, dry cough, myalgia, arthralgia, chest discomfort and poor appetite of 1 week duration. There was a history mosquito fogging around his neighbourhood in his hometown. Further history revealed that he went to a forest in Jeli (northern part of Kelantan) 3 weeks prior to the event. Initially he was treated as severe dengue with plasma leakage complicated with type 1 respiratory failure as evidenced by positive serum NS1-antigen and thrombocytopenia. Blood for malarial parasite (BFMP) was sent for test as there was suspicion of malaria due to persistent thrombocytopenia despite recovering from dengue infection and the presence of a risk factor. The test revealed high count of malaria parasite. Confirmatory PCR identified the parasite to be Plasmodium knowlesi Intravenous artesunate was administered to the patient immediately after acquiring the BFMP result. Severe malaria was complicated with acute kidney injury and septicaemic shock. Fortunately the patient made full recovery and was discharged from the ward after 2 weeks of hospitalisation.
    Matched MeSH terms: Plasmodium knowlesi*
  10. Chen Y, Chan CK, Kerishnan JP, Lau YL, Wong YL, Gopinath SC
    BMC Infect Dis, 2015;15:49.
    PMID: 25656928 DOI: 10.1186/s12879-015-0786-2
    Plasmodium knowlesi was identified as the fifth major malaria parasite in humans. It presents severe clinical symptoms and leads to mortality as a result of hyperparasitemia in a short period of time. This study aimed to improve the current understanding of P. knowlesi and identify potential biomarkers for knowlesi malaria.
    Matched MeSH terms: Plasmodium knowlesi/immunology; Plasmodium knowlesi/pathogenicity*
  11. Cheo SW, Khoo TT, Tan YA, Yeoh WC, Low QJ
    Med J Malaysia, 2020 07;75(4):447-449.
    PMID: 32724015
    Malaria is a parasitic disease that is caused by the Plasmodium parasite. Worldwide, it remains a significant public health problem especially in the Africa region where it contributes to more than 90% of cases and malaria death. However, zoonotic (simian) Plasmodium knowlesi parasite is a widely prevalent cause of malaria in the South East Asian countries. It is known to cause severe human disease due to its 24hour erythrocytic cycles. Thus far, cases of severe falciparum malaria have been reported in asplenic patients. Here, we report a case of severe P.knowlesi malaria in a 51-year-old man who is a postsplenectomy patient.
    Matched MeSH terms: Plasmodium knowlesi/drug effects*
  12. Cheong FW, Fong MY, Lau YL
    Acta Trop, 2016 Feb;154:89-94.
    PMID: 26624919 DOI: 10.1016/j.actatropica.2015.11.005
    Plasmodium knowlesi can cause potentially life threatening human malaria. The Plasmodium merozoite surface protein-142 (MSP-142) is a potential target for malaria blood stage vaccine, and for diagnosis of malaria. Two epitope mapping techniques were used to identify the potential epitopes within P. knowlesi MSP-142. Nine and 14 potential epitopes were identified using overlapping synthetic peptide library and phage display library, respectively. Two regions on P. knowlesi MSP-142 (amino acid residues 37-95 and residues 240-289) were identified to be the potential dominant epitope regions. Two of the prominent epitopes, P10 (TAKDGMEYYNKMGELYKQ) and P31 (RCLLGFKEVGGKCVPASI), were evaluated using mouse model. P10- and P31-immunized mouse sera reacted with recombinant P. knowlesi MSP-142, with the IgG isotype distribution of IgG2b>IgG1>IgG2a>IgG3. Significant higher level of cytokines interferon-gamma and interleukin-2 was detected in P31-immunized mice. Both P10 and P31 could be the suitable epitope candidates to be used in malaria vaccine designs and immunodiagnostic assays, provided further evaluation is needed to validate the potential uses of these epitopes.
    Matched MeSH terms: Plasmodium knowlesi
  13. Cheong FW, Fong MY, Lau YL, Mahmud R
    Malar J, 2013;12:454.
    PMID: 24354660 DOI: 10.1186/1475-2875-12-454
    Plasmodium knowlesi is the fifth Plasmodium species that can infect humans. The Plasmodium merozoite surface protein-1(42) (MSP-1(42)) is a potential candidate for malaria vaccine. However, limited studies have focused on P. knowlesi MSP-1(42).
    Matched MeSH terms: Plasmodium knowlesi/genetics; Plasmodium knowlesi/immunology*
  14. Cheong FW, Lau YL, Fong MY, Mahmud R
    Am J Trop Med Hyg, 2013 May;88(5):835-40.
    PMID: 23509118 DOI: 10.4269/ajtmh.12-0250
    Plasmodium knowlesi is now known as the fifth Plasmodium species that can cause human malaria. The Plasmodium merozoite surface protein (MSP) has been reported to be potential target for vaccination and diagnosis of malaria. MSP-1(33) has been shown to be immunogenic and its T cell epitopes could mediate cellular immune protection. However, limited studies have focused on P. knowlesi MSP-133. In this study, an approximately 28-kDa recombinant P. knowlesi MSP-1(33) (pkMSP-1(33)) was expressed by using an Escherichia coli system. The purified pkMSP-1(33) reacted with serum samples of patients infected with P. knowlesi (31 of 31, 100%) and non-P. knowlesi malaria (27 of 28, 96.43%) by Western blotting. The pkMSP-1(33) also reacted with P. knowlesi (25 of 31, 80.65%) and non-P. knowlesi malaria sera (20 of 28, 71.43%) in an enzyme-linked immunosorbent assay (ELISA). Most of the non-malarial infection (49 of 52 in by Western blotting and 46 of 52 in the ELISA) and healthy donor serum samples (65 of 65 by Western blotting and ELISA) did not react with recombinant pkMSP-1(33).
    Matched MeSH terms: Plasmodium knowlesi/genetics; Plasmodium knowlesi/immunology; Plasmodium knowlesi/metabolism*
  15. Chin AZ, Maluda MCM, Jelip J, Jeffree MSB, Culleton R, Ahmed K
    J Physiol Anthropol, 2020 Nov 23;39(1):36.
    PMID: 33228775 DOI: 10.1186/s40101-020-00247-5
    BACKGROUND: Malaria is a major public-health problem, with over 40% of the world's population (more than 3.3 billion people) at risk from the disease. Malaysia has committed to eliminate indigenous human malaria transmission by 2020. The objective of this descriptive study is to understand the epidemiology of malaria in Malaysia from 2000 through 2018 and to highlight the threat posed by zoonotic malaria to the National Malaria Elimination Strategic Plan.

    METHODS: Malaria is a notifiable infection in Malaysia. The data used in this study were extracted from the Disease Control Division, Ministry of Health Malaysia, contributed by the hospitals and health clinics throughout Malaysia. The population data used in this study was extracted from the Department of Statistics Malaysia. Data analyses were performed using Microsoft Excel. Data used for mapping are available at EPSG:4326 WGS84 CRS (Coordinate Reference System). Shapefile was obtained from igismap. Mapping and plotting of the map were performed using QGIS.

    RESULTS: Between 2000 and 2007, human malaria contributed 100% of reported malaria and 18-46 deaths per year in Malaysia. Between 2008 and 2017, indigenous malaria cases decreased from 6071 to 85 (98.6% reduction), while during the same period, zoonotic Plasmodium knowlesi cases increased from 376 to 3614 cases (an 861% increase). The year 2018 marked the first year that Malaysia did not report any indigenous cases of malaria caused by human malaria parasites. However, there was an increasing trend of P. knowlesi cases, with a total of 4131 cases reported in that year. Although the increased incidence of P. knowlesi cases can be attributed to various factors including improved diagnostic capacity, reduction in human malaria cases, and increase in awareness of P. knowlesi, more than 50% of P. knowlesi cases were associated with agriculture and plantation activities, with a large remainder proportion linked to forest-related activities.

    CONCLUSIONS: Malaysia has entered the elimination phase of malaria control. Zoonotic malaria, however, is increasing exponentially and becoming a significant public health problem. Improved inter-sectoral collaboration is required in order to develop a more integrated effort to control zoonotic malaria. Local political commitment and the provision of technical support from the World Health Organization will help to create focused and concerted efforts towards ensuring the success of the National Malaria Elimination Strategic Plan.

    Matched MeSH terms: Plasmodium knowlesi*
  16. Chin AZ, Avoi R, Atil A, Awang Lukman K, Syed Abdul Rahim SS, Ibrahim MY, et al.
    PLoS One, 2021;16(9):e0257104.
    PMID: 34506556 DOI: 10.1371/journal.pone.0257104
    BACKGROUND: In the Malaysian state of Sabah, P. knowlesi notifications increased from 2% (59/2,741) of total malaria notifications in 2004 to 98% (2030/2,078) in 2017. There was a gap regarding P. knowlesi acquisition risk factors related to practice specifically in working age group. The main objective of this study was to identify the risk factors for acquiring P. knowlesi infection in Sabah among the working age group.

    METHODS AND METHODS: This retrospective population-based case-control study was conducted in Ranau district to assess sociodemographic, behavioural and medical history risk factors using a pretested questionnaire. The data were entered and analyzed using IBM SPSS version 23. Bivariate analysis was conducted using binary logistic regression whereas multivariate analysis was conducted using multivariable logistic regression. We set a statistical significance at p-value less than or equal to 0.05.

    RESULTS: A total of 266 cases and 532 controls were included in the study. Male gender (AOR = 2.71; 95% CI: 1.63-4.50), spending overnight in forest (AOR = 1.92; 95% CI: 1.20-3.06), not using mosquito repellent (AOR = 2.49; 95% CI: 1.36-4.56) and history of previous malaria infection (AOR = 49.34; 95% CI: 39.09-78.32) were found to be independent predictors of P. knowlesi infection.

    CONCLUSIONS: This study showed the need to strengthen the strategies in preventing and controlling P. knowlesi infection specifically in changing the practice of spending overnight in forest and increasing the usage of personal mosquito repellent.

    Matched MeSH terms: Plasmodium knowlesi/physiology*
  17. Chong ETJ, Neoh JWF, Lau TY, Lim YA, Chai HC, Chua KH, et al.
    Malar J, 2020 Oct 22;19(1):377.
    PMID: 33092594 DOI: 10.1186/s12936-020-03451-x
    BACKGROUND: Understanding the genetic diversity of candidate genes for malaria vaccines such as circumsporozoite protein (csp) may enhance the development of vaccines for treating Plasmodium knowlesi. Hence, the aim of this study is to investigate the genetic diversity of non-repeat regions of csp in P. knowlesi from Malaysian Borneo and Peninsular Malaysia.

    METHODS: A total of 46 csp genes were subjected to polymerase chain reaction amplification. The genes were obtained from P. knowlesi isolates collected from different divisions of Sabah, Malaysian Borneo, and Peninsular Malaysia. The targeted gene fragments were cloned into a commercial vector and sequenced, and a phylogenetic tree was constructed while incorporating 168 csp sequences retrieved from the GenBank database. The genetic diversity and natural evolution of the csp sequences were analysed using MEGA6 and DnaSP ver. 5.10.01. A genealogical network of the csp haplotypes was generated using NETWORK ver. 4.6.1.3.

    RESULTS: The phylogenetic analysis revealed indistinguishable clusters of P. knowlesi isolates across different geographic regions, including Malaysian Borneo and Peninsular Malaysia. Nucleotide analysis showed that the csp non-repeat regions of zoonotic P. knowlesi isolates obtained in this study underwent purifying selection with population expansion, which was supported by extensive haplotype sharing observed between humans and macaques. Novel variations were observed in the C-terminal non-repeat region of csp.

    CONCLUSIONS: The csp non-repeat regions are relatively conserved and there is no distinct cluster of P. knowlesi isolates from Malaysian Borneo and Peninsular Malaysia. Distinctive variation data obtained in the C-terminal non-repeat region of csp could be beneficial for the design and development of vaccines to treat P. knowlesi.

    Matched MeSH terms: Plasmodium knowlesi/genetics*
  18. Chong ETJ, Neoh JWF, Lau TY, Lim YA, Chua KH, Lee PC
    Acta Trop, 2018 May;181:35-39.
    PMID: 29409854 DOI: 10.1016/j.actatropica.2018.01.018
    Malaria is a notorious disease which causes major global morbidity and mortality. This study aims to investigate the genetic and haplotype differences of Plasmodium knowlesi (P. knowlesi) isolates in Malaysian Borneo and Peninsular Malaysia based on the molecular analysis of the cytochrome b (cyt b) gene. The cyt b gene of 49 P. knowlesi isolates collected from Sabah, Malaysian Borneo and Peninsular Malaysia was amplified using PCR, cloned into a commercialized vector and sequenced. In addition, 45 cyt b sequences were retrieved from humans and macaques bringing to a total of 94 cyt b gene nucleotide sequences for phylogenetic analysis. Genetic and haplotype analyses of the cyt b were analyzed using MEGA6 and DnaSP ver. 5.10.01. The haplotype genealogical linkage of cyt b was generated using NETWORK ver. 4.6.1.3. Our phylogenetic tree revealed the conservation of the cyt b coding sequences with no distinct cluster across different geographic regions. Nucleotide analysis of cyt b showed that the P. knowlesi isolates underwent purifying selection with population expansion, which was further supported by extensive haplotype sharing between the macaques and humans from Malaysian Borneo and Peninsular Malaysia in the median-joining network analysis. This study expands knowledge on conservation of the zoonotic P. knowlesi cyt b gene between Malaysian Borneo and Peninsular Malaysia.
    Matched MeSH terms: Plasmodium knowlesi/classification; Plasmodium knowlesi/enzymology; Plasmodium knowlesi/genetics*
  19. Chong SE, Mohamad Zaini RH, Suraiya S, Lee KT, Lim JA
    Malar J, 2017 01 03;16(1):2.
    PMID: 28049485 DOI: 10.1186/s12936-016-1666-y
    BACKGROUND: Dengue and malaria are two common, mosquito-borne infections, which may lead to mortality if not managed properly. Concurrent infections of dengue and malaria are rare due to the different habitats of its vectors and activities of different carrier mosquitoes. The first case reported was in 2005. Since then, several concurrent infections have been reported between the dengue virus (DENV) and the malaria protozoans, Plasmodium falciparum and Plasmodium vivax. Symptoms of each infection may be masked by a simultaneous second infection, resulting in late treatment and severe complications. Plasmodium knowlesi is also a common cause of malaria in Malaysia with one of the highest rates of mortality. This report is one of the earliest in literature of concomitant infection between DENV and P. knowlesi in which a delay in diagnosis had placed a patient in a life-threatening situation.

    CASE PRESENTATION: A 59-year old man staying near the Belum-Temengor rainforest at the Malaysia-Thailand border was admitted with fever for 6 days, with respiratory distress. His non-structural protein 1 antigen and Anti-DENV Immunoglobulin M tests were positive. He was treated for severe dengue with compensated shock. Treating the dengue had so distracted the clinicians that a blood film for the malaria parasite was not done. Despite aggressive supportive treatment in the intensive care unit (ICU), the patient had unresolved acidosis as well as multi-organ failure involving respiratory, renal, liver, and haematological systems. It was due to the presentation of shivering in the ICU, that a blood film was done on the second day that revealed the presence of P. knowlesi with a parasite count of 520,000/μL. The patient was subsequently treated with artesunate-doxycycline and made a good recovery after nine days in ICU.

    CONCLUSIONS: This case contributes to the body of literature on co-infection between DENV and P. knowlesi and highlights the clinical consequences, which can be severe. Awareness should be raised among health-care workers on the possibility of dengue-malaria co-infection in this region. Further research is required to determine the real incidence and risk of co-infection in order to improve the management of acute febrile illness.

    Matched MeSH terms: Plasmodium knowlesi/isolation & purification*
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