Displaying publications 561 - 580 of 1467 in total

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  1. Fulltext Elucidation of the compatible interaction between banana and Meloidogyne incognita via high-throughput proteome profiling
    Al-Idrus A, Carpentier SC, Ahmad MT, Panis B, Mohamed Z
    PLoS One, 2017;12(6):e0178438.
    PMID: 28575037 DOI: 10.1371/journal.pone.0178438
    With a diverse host range, Meloidogyne incognita (root-knot nematode) is listed as one of the most economically important obligate parasites of agriculture. This nematode species establishes permanent feeding sites in plant root systems soon after infestation. A compatible host-nematode interaction triggers a cascade of morphological and physiological process disruptions of the host, leading to pathogenesis. Such disruption is reflected by altered gene expression in affected cells, detectable using molecular approaches. We employed a high-throughput proteomics approach to elucidate the events involved in a compatible banana- M. incognita interaction. This study serves as the first crucial step in developing natural banana resistance for the purpose of biological-based nematode management programme. We successfully profiled 114 Grand naine root proteins involved in the interaction with M. incognita at the 30th- and 60th- day after inoculation (dai). The abundance of proteins involved in fundamental biological processes, cellular component organisation and stress responses were significantly altered in inoculated root samples. In addition, the abundance of proteins in pathways associated with defence and giant cell maintenance in plants such as phenylpropanoid biosynthesis, glycolysis and citrate cycle were also implicated by the infestation.
    Matched MeSH terms: Musa/parasitology*
  2. Detection of a Borrelia sp. From Ixodes granulatus Ticks Collected From Rodents in Malaysia
    Khoo JJ, Ishak SN, Lim FS, Mohd-Taib FS, Khor CS, Loong SK, et al.
    J Med Entomol, 2018 10 25;55(6):1642-1647.
    PMID: 30137379 DOI: 10.1093/jme/tjy122
    The Borrelia genus consists of spirochete bacteria known to cause Lyme disease (LD) and relapsing fever in humans. Borrelia pathogens are commonly transmitted via arthropod vectors such as ticks, mites, or lice. Here, we report the molecular screening of LD group Borrelia sp. from ticks (Acari: Ixodidae) collected from rodents trapped in recreational forests and a semiurban residential area in the Selangor state in Malaysia. Of 156 adult ticks surveyed, 72 ticks were determined as positive for Borrelia sp. by polymerase chain reaction (PCR). All Borrelia PCR-positive ticks belonged to the Ixodes granulatus Supino species. Borrelia sp. was not detected in other tick species examined, including Dermacentor sp. and Amblyomma sp. ticks. Thirteen Borrelia PCR-positive tick samples were selected for further sequence analyses. Phylogenetic analyses of partial flaB gene sequences revealed that the Borrelia sp. were closely related to the LD group borreliae, Borrelia yangtzensis; a novel Borrelia genospecies reported in East Asian countries including Japan, Taiwan, and China. To our knowledge, this is the first report of Borrelia sp. related to Borrelia yangtzensis detected in Malaysia and Southeast Asia. The zoonotic potential of the Borrelia sp. reported here merits further investigation, as it may explain the previously reported serological evidence for borrelial infections in Malaysia.
    Matched MeSH terms: Rodentia/parasitology*
  3. Special issue - Learning and teaching of veterinary parasitology
    Jabbar A, Gasser RB
    Vet Parasitol, 2018 04 15;253:120-121.
    PMID: 30173728 DOI: 10.1016/j.vetpar.2018.02.020
    Matched MeSH terms: Parasitology/education*
  4. Occurrence and molecular characterisation of Acanthamoeba isolated from recreational hot springs in Malaysia: evidence of pathogenic potential
    Mohd Hussain RH, Ishak AR, Abdul Ghani MK, Ahmed Khan N, Siddiqui R, Shahrul Anuar T
    J Water Health, 2019 Oct;17(5):813-825.
    PMID: 31638031 DOI: 10.2166/wh.2019.214
    This study aimed to identify the Acanthamoeba genotypes and their pathogenic potential in five recreational hot springs in Peninsular Malaysia. Fifty water samples were collected between April and September 2018. Physical parameters of water quality were measured in situ while chemical and microbiological analyses were performed in the laboratory. All samples were filtered through the nitrocellulose membrane and tested for Acanthamoeba using both cultivation and polymerase chain reaction (PCR) by targeting the 18S ribosomal RNA gene. The pathogenic potential of all positive isolates was identified using thermo- and osmotolerance tests. Thirty-eight (76.0%) samples were positive for Acanthamoeba. Water temperature (P = 0.035), chemical oxygen demand (P = 0.026), sulphate (P = 0.002) and Escherichia coli (P < 0.001) were found to be significantly correlated with the presence of Acanthamoeba. Phylogenetic analysis revealed that 24 samples belonged to genotype T4, nine (T15), two (T3) and one from each genotype T5, T11 and T17. Thermo- and osmotolerance tests showed that 6 (15.79%) of the Acanthamoeba strains were highly pathogenic. The existence of Acanthamoeba in recreational hot springs should be considered as a health threat among the public especially for high-risk people. Periodic surveillance of hot spring waters and posting warning signs by health authorities is recommended to prevent disease related to pathogenic Acanthamoeba.
    Matched MeSH terms: Hot Springs/parasitology*
  5. Fulltext Bedbugs Evolved before Their Bat Hosts and Did Not Co-speciate with Ancient Humans
    Roth S, Balvín O, Siva-Jothy MT, Di Iorio O, Benda P, Calva O, et al.
    Curr Biol, 2019 06 03;29(11):1847-1853.e4.
    PMID: 31104934 DOI: 10.1016/j.cub.2019.04.048
    All 100+ bedbug species (Cimicidae) are obligate blood-sucking parasites [1, 2]. In general, blood sucking (hematophagy) is thought to have evolved in generalist feeders adventitiously taking blood meals [3, 4], but those cimicid taxa currently considered ancestral are putative host specialists [1, 5]. Bats are believed to be the ancestral hosts of cimicids [1], but a cimicid fossil [6] predates the oldest known bat fossil [7] by >30 million years (Ma). The bedbugs that parasitize humans [1, 8] are host generalists, so their evolution from specialist ancestors is incompatible with the "resource efficiency" hypothesis and only partially consistent with the "oscillation" hypothesis [9-16]. Because quantifying host shift frequencies of hematophagous specialists and generalists may help to predict host associations when vertebrate ranges expand by climate change [17], livestock, and pet trade in general and because of the previously proposed role of human pre-history in parasite speciation [18-20], we constructed a fossil-dated, molecular phylogeny of the Cimicidae. This phylogeny places ancestral Cimicidae to 115 mya as hematophagous specialists with lineages that later frequently populated bat and bird lineages. We also found that the clades, including the two major current urban pests, Cimex lectularius and C. hemipterus, separated 47 mya, rejecting the notion that the evolutionary trajectories of Homo caused their divergence [18-21]. VIDEO ABSTRACT.
    Matched MeSH terms: Chiroptera/parasitology*
  6. Two Plasmodium knowlesi-specific antigens on the surface of schizont-infected Rhesus monkey erythrocytes induce antibody production in immune hosts
    Schmidt-Ullrich R, Wallach DF, Lightholder J
    J. Exp. Med., 1979 Jul 01;150(1):86-99.
    PMID: 87490
    Purified schizonts (6--10 nuclei) and membranes of schizont-infected erythrocytes from the Malaysian and Philippine strain of Plasmodium knowlesi are analyzed immunochemically using immunoglobulin of rhesus monkey hyperimmune sera against schizonts and of sera from naturally immune monkeys. The anti-schizont Ig identifies less than 20 immune components in Triton X-100-solubilized schizonts and membranes of infected cells. Of these antigens, 9 (component 1, 3, 4, 5, 6, 10, 11, 18, and 20) are common to parasites and membranes of infected erythrocytes, and 12 (2A,B, 6, 8, 9, 12, 13p, 14, 16A,B, 19 A,Bp, 21, 22p, and 23) are predominantly found in the parasite; 4 components (13i, 19A,Bi, 22A, B, and 24) are unique to the membrane of infected erythrocytes. Only three parasite-specific components (1, 13, and 19) are exposed on the surface of parasitized erythrocytes as revealed by both lactoperoxidase-catalyzed radioiodination and extensive absorption of anti-schizont Ig using intact infected erythrocytes. Two plasmodium-specific antigens (1 and 13) on the surface of infected erythrocytes are recognized by sera of rhesus monkeys rendered naturally immune against P. knowlesi infections and, therefore, represent antigens in vivo. Analyses of schizonts and membranes of parasitized erythrocytes of the two different strains of P. knowlesi yields only some minor quantitative, but no qualitative differences when analyzed with both types of antisera. Importantly, components 1 and 13 appear identical in both strains.
    Matched MeSH terms: Erythrocytes/parasitology*
  7. Occurrence of free-living amoebae (Acanthamoeba, Balamuthia, Naegleria) in water samples in Peninsular Malaysia
    Gabriel S, Khan NA, Siddiqui R
    J Water Health, 2019 Feb;17(1):160-171.
    PMID: 30758312 DOI: 10.2166/wh.2018.164
    The aim of this study was to determine the occurrence of free-living amoebae (FLA) in Peninsular Malaysia and to compare different methodologies to detect them from water samples. Water samples were collected from tap water, recreational places, water dispensers, filtered water, etc. and tested for FLA using both cultivation and polymerase chain reaction (PCR) via plating assays and centrifugation methods. Amoebae DNA was extracted using Instagene matrix and PCR was performed using genus-specific primers. Of 250 samples, 142 (56.8%) samples were positive for presence of amoebae, while 108 (43.2%) were negative. Recreational water showed higher prevalence of amoebae than tap water. PCR for the plating assays revealed the presence of Acanthamoeba in 91 (64%) samples and Naegleria in 99 (70%) of samples analysed. All samples tested were negative for B. mandrillaris. In contrast, the centrifugation method was less effective in detecting amoebae as only one sample revealed the presence of Acanthamoeba and 52 (29%) samples were positive for Naegleria. PCR assays were specific and sensitive, detecting as few as 10 cells. These findings show the vast distribution and presence of FLA in all 11 states of Peninsular Malaysia. Further studies could determine the possible presence of pathogenic species and strains of free-living amoebae in public water supplies in Malaysia.
    Matched MeSH terms: Fresh Water/parasitology*
  8. Fulltext Genetic diversity of Plasmodium knowlesi among human and long-tailed macaque populations in Peninsular Malaysia: The utility of microsatellite markers
    Saleh Huddin A, Md Yusuf N, Razak MRMA, Ogu Salim N, Hisam S
    Infect Genet Evol, 2019 11;75:103952.
    PMID: 31279818 DOI: 10.1016/j.meegid.2019.103952
    It has been discovered that Plasmodium knowlesi (P. knowlesi) is transmitted from macaque to man. Thus, the aim of the present study was to determine P. knowlesi genetic diversity in both human (n = 147) and long-tailed macaque (n = 26) samples from high- and low-endemicity localities. Genotyping was performed using seven neutral microsatellite loci markers. The size of the alleles, multiplicity of infection (MOI), mean number of alleles (Na), expected heterozygosity (HE), linkage disequilibrium (LD), and genetic differentiation (FST) were determined. In highly endemic P. knowlesi localities, the MOI for human and long-tailed macaque isolates was 1.04 and 1.15, respectively, while the Na was 11.14 and 7.86, respectively. Based on the allele frequency distribution for all loci, and with FST 
    Matched MeSH terms: Macaca/parasitology*
  9. Suitability of heat- and freeze-killed oothecae of the American cockroach (Dictyoptera: Blattidae) as hosts for an oothecal parasitoid, Aprostocetus hagenowii (Hymenoptera: Eulophidae)
    Tee HS, Saad AR, Lee CY
    J Econ Entomol, 2010 Oct;103(5):1770-4.
    PMID: 21061978
    The objective of this study was to evaluate the suitability of heat- and freeze-killed oothecae of Periplaneta americana (L.) (Dictyoptera: Blattidae) as hosts for parasitoid Aprostocetus hagenowii (Ratzeburg) (Hymenoptera: Eulophidae). The oothecae were subjected to -20, 45, 48, 50, and 55 degrees C at different exposure times (15, 30, 45, and 60 min). The effects of heat- and freeze-killed oothecae on several biological parameters (e.g., parasitism and emergence rates, developmental times, progeny number, and sex ratio) ofA. hagenowii were determined. Embryonic development of 2-d-old oothecae was terminated by either freezing at -20 degrees C or heating at > or = 48 degrees C for > or =30 min. A. hagenowii parasitized live oothecae as well as both heat- and freeze-killed oothecae. Percentage parasitism, emergence rates, and developmental times ofA. hagenowii in both heat- and freeze-killed oothecae were not significantly different from those of the live oothecae. Both heating and freezing did not influence progeny number (male and female) and sex ratio of A. hagenowii emerged from killed oothecae.
    Matched MeSH terms: Periplaneta/parasitology*
  10. Intra- and interspecific agonistic behavior of the subterranean termite Microcerotermes crassus (Isoptera: Termitidae)
    Wong N, Lee CY
    J Econ Entomol, 2010 Oct;103(5):1754-60.
    PMID: 21061976
    The aim of our study was to investigate the intra- and interspecific agonistic behaviors exhibited by the worker and soldier castes of the subterranean termite Microcerotermes crassus Snyder (Isoptera: Termitidae). Aggression between M. crassus colonies from different field locations and also against three termite species--Coptotermes gestroi (Wasmann), Globitermnes sulphureus Haviland, and Odontotermes sp.--were observed in the laboratory. Termite responses were tested in paired combination of castes (soldiers versus soldiers, soldiers versus workers, and workers versus workers) consisting of 10 individuals each. Significant agonistic behaviors were observed only in encounters between pairings of different termite species. M. crassus was aggressive toward individuals from different species but not toward individuals from different M. crassus colonies. Mortality of M. crassus reached 100% in most of the interspecific encounters. However, no or low mortality was recorded in the intraspecific pairings.
    Matched MeSH terms: Soil/parasitology
  11. Prevalence of a koinobiont endoparasitoid Misotermes mindeni (Diptera: Phoridae) in colonies of the fungus-growing termite Macrotermes gilvus (Blattodea: Termitidae) in Malaysia
    Foo FK, Singham GV, Othman AS, Lee CY
    J Econ Entomol, 2011 Oct;104(5):1675-9.
    PMID: 22066198
    A survey of the infestation rate of colonies of Macrotermes gilvus (Hagen) (Termitidae: Macrotermitinae) with the koinobiont endoparasitoid Misotermes mindeni Disney & Neoh (Diptera: Phoridae) was conducted in Malaysia from September 2009 to January 2011 in the states of Kedah, Penang, Perak, Selangor, Kuala Lumpur, Johor, Terengganu, and Sarawak. Of the 1,125 M. gilvus mounds surveyed, 12.4% contained termites parasitized by M. mindeni and these mounds occurred only in the states of Penang and Perak. High frequencies of mounds containing parasitized termites were found at sites in Penang: Bayan Lepas (21.1%), Minden Campus of Universiti Sains Malaysia ([USM]; 24.5%), Teluk Bahang (28.0%), and Bukit Mertajam (35.0%); the lowest frequency (4.0%) was recorded from Gelugor. The parasitized colonies at all sites were classified as healthy, with exception of several from the Minden Campus of USM (96.4% healthy) and Ayer Itam (87.5% healthy). Most parasitized colonies (71.2%) had a low level of M. mindeni infestation. Only 16.7 and 12.1% of the infested colonies had moderate or high parasite infestation levels, respectively. The height of infected mounds was significantly higher than that of the healthy mounds, but there was no difference between the mound diameters of infested and uninfested mounds. Parasite infestation level was not significantly correlated with mound height or mound diameter. The ambient light intensity at sites with infested mounds was significantly lower than that of uninfested mounds. There was also a significant negative relationship between light intensity and degree of parasitism.
    Matched MeSH terms: Isoptera/parasitology*
  12. Relationship between the number of Hepatozoon canis gamonts and hematobiochemical values in dogs
    Hangsawek A, Chutasripanich S, Kammaled P, Rawangchue T, Jirapattharasate C, Moonarmart W, et al.
    Trop Biomed, 2020 Jun 01;37(2):421-432.
    PMID: 33612811
    The occurrence of canine hepatozoonosis in Thailand is primarily caused by Hepatozoon canis. Recently, the relationship of hematology and biochemistry with this disease has been studied, but knowledge regarding the relationship between the quantity of H. canis intracellular gamonts and the hematological profile has not yet been reported. The objective of this study was to investigate the clinical, hematological and biochemical profile of H. canis-positive dogs and the relationship of the number of H. canis gamonts, animal signalment, and hematological and biochemical values. A total of 185 H. canis-positive blood samples were examined, including buffy coat smears and comprehensive data. The number of gamonts was randomly counted from buffy coat smears samples (75/185). The dogs infected with H. canis presented to the animal hospital mostly for health status checks, anorexia, or accidents. Observations from the physical examination on the first day of registration included systemic abnormalities such as digestive, integument, respiratory, urogenital, etc. Most of the dogs showed clinical signs of systemic abnormality in more than one system. Our study shows that plasma proteins are correlated with the number of H. canis gamonts, using Spearman's rho correlation coefficient with significant difference (p <0.05). This finding could be applied to improve the diagnosis and treatment of canine hepatozoonosis.
    Matched MeSH terms: Dog Diseases/parasitology
  13. Morphological characteristics of microfilariae in blood smears of the common treeshrew Tupaia glis (Mammalia: Scandentia) in Gemas, Negeri Sembilan, Malaysia
    Mat Udin AS, Uni S, Zainuri NA, Abdullah Halim MR, Belabut DA
    Trop Biomed, 2020 Dec 01;37(4):1152-1157.
    PMID: 33612768 DOI: 10.47665/tb.37.4.1152
    Some filarial nematodes, such as Wuchereria bancrofti, Brugia malayi, and Brugia timori, cause lymphatic diseases in humans in the tropics, whereas other filarial parasites from wild animals cause zoonotic diseases in humans worldwide. To elucidate the prevalence and diversity of filarial parasites in Malaysia, we investigated the filarial parasites from wild animals in Gemas, Negeri Sembilan. To find adult filarial parasites, we dissected 26 animals, which included five frogs, one skink, one snake, two birds, six common treeshrews, and 11 rats. Then, we examined microfilariae in the blood smears and skin snips obtained from each animal. We found two types of microfilariae in the blood smears of common treeshrews: one was very similar to Malayfilaria sofiani and the other closely resembled Brugia tupaiae. These findings indicate an additional distribution of these filarial parasites in Gemas.
    Matched MeSH terms: Tupaia/parasitology*
  14. Genetic diversity of the full length apical membrane antigen-1 of Plasmodium knowlesi clinical isolates from Peninsular Malaysia
    Ng YL, Fong MY, Lau YL
    Trop Biomed, 2021 Jun 01;38(2):159-164.
    PMID: 34172705 DOI: 10.47665/tb.38.2.052
    The Plasmodium knowlesi apical membrane antigen-1 (PkAMA-1) plays an important role in the invasion of the parasite into its host erythrocyte, and it has been regarded as a potential vaccine candidate against human knowlesi malaria. This study investigates genetic diversity and natural selection of the full length PkAMA-1 of P. knowlesi clinical isolates from Peninsular Malaysia. Blood samples were collected from P. knowlesi malaria patients from Peninsular Malaysia. The PkAMA-1 gene was amplified from DNA samples using PCR, cloned into a plasmid vector and sequenced. Results showed that nucleotide diversity of the full length PkAMA-1 from Peninsular Malaysia isolates (π: 0.006) was almost similar to that of Sarawak (π: 0.005) and Sabah (π: 0.004) isolates reported in other studies. Deeper analysis revealed Domain I (π: 0.007) in the PkAMA-1 had the highest diversity as compared to Domain II (π: 0.004) and Domain III (π: 0.003). Z-test indicated negative (purifying) selection of the gene. Combined alignment analysis at the amino acid level for the Peninsular Malaysia and Sarawak PkAMA-1 sequences revealed 34 polymorphic sites. Thirty-one of these sites were dimorphic, and 3 were trimorphic. The amino acid sequences could be categorised into 31 haplotypes. In the haplotype network, PkAMA-1 from Peninsular Malaysia and Sarawak were separated into two groups.
    Matched MeSH terms: Malaria/parasitology
  15. Ultrastructural analysis of Apicomplexa-Like parasites in two conch species Laevistrombus canarium and canarium urceus from Johor Straits, Malaysia
    Azmi NF, Ghaffar MA, Daud HHM, Cob ZC
    J Invertebr Pathol, 2018 02;152:17-24.
    PMID: 29360442 DOI: 10.1016/j.jip.2018.01.005
    The tropical conch, Laevistrombus canarium (Linnaeus, 1758) and Canarium urceus (Linneaus, 1758) are ecologically and economically important shellfish species in Malaysia and neighboring region. Their populations, however are currently declining and this histopathological study investigates the aspect of parasitism and diseases that may affect their well-being. Conch samples were randomly collected from their natural habitat and histological sections (4-5 µm) of various organs and tissues were examined under light microscope. This was followed by ultrastructure analysis on infected tissues using transmission electron microscope (TEM). Based on the histological analysis, large numbers of gamonts, sporocysts and trophozoites of Apicomplexa-like parasites were observed in the vacuolated cells and pyramidal crypt cells of the digestive tubules, and in the digestive ducts. Furthermore, coccidian and oocysts-like Pseudoklossia sp. stages were also observed in the cells of the kidney. Apart from that, spores with cyst-like structure were observed in the digestive gland and kidney. Although the parasites were present in most of the organs analyzed, there was no obvious symptom, inflammatory response or mortality incurred on both species, which implies the possibility of a non-virulent relationship like commensalisms or mutualism. However, more investigations, including molecular studies, are needed to confirm the parasite identification and dynamics, and to further evaluate the nature of relationship between Apicomplexa parasites and their host.
    Matched MeSH terms: Gastropoda/parasitology*
  16. Aquatic biomonitoring of Giardia cysts and Cryptosporidium oocysts in peninsular Malaysia
    Lee SC, Ngui R, Tan TK, Roslan MA, Ithoi I, Lim YA
    Environ Sci Pollut Res Int, 2014 Jan;21(1):445-53.
    PMID: 23794081 DOI: 10.1007/s11356-013-1925-1
    An aquatic biomonitoring of Giardia cysts and Cryptosporidium oocysts in river water corresponding to five villages situated in three states in peninsular Malaysia was determined. There were 51.3% (20/39) and 23.1% (9/39) samples positive for Giardia and Cryptosporidium (oo)cysts, respectively. Overall mean concentration between villages for Giardia cysts ranged from 0.10 to 25.80 cysts/l whilst Cryptosporidium oocysts ranged from 0.10 to 0.90 oocysts/l. Detailed results of the river samples from five villages indicated that Kuala Pangsun 100% (9/9), Kemensah 77.8% (7/9), Pos Piah 33.3% (3/9) and Paya Lebar 33.3% (1/3) were contaminated with Giardia cysts whilst Cryptosporidium (oo)cysts were only detected in Kemensah (100 %; 9/9) and Kuala Pangsun (66.6%; 6/9). However, the water samples from Bentong were all negative for these waterborne parasites. Samples were collected from lower point, midpoint and upper point. Midpoint refers to the section of the river where the studied communities are highly populated. Meanwhile, the position of the lower point is at least 2 km southward of the midpoint and upper point is at least 2 km northward of the midpoint. The highest mean concentration for (oo)cysts was found at the lower points [3.15 ± 6.09 (oo)cysts/l], followed by midpoints [0.66 ± 1.10 (oo)cysts/l] and upper points [0.66 ± 0.92 (oo)cysts/l]. The mean concentration of Giardia cysts was highest at Kuala Pangsun (i.e. 5.97 ± 7.0 cysts/l), followed by Kemensah (0.83 ± 0.81 cysts/l), Pos Piah (0.20 ± 0.35 cysts/l) and Paya Lebar (0.10 ± 0.19 cysts/l). On the other hand, the mean concentration of Cryptosporidium oocysts was higher at Kemensah (0.31 ± 0.19 cysts/l) compared to Kuala Pangsun (0.03 ± 0.03cysts/l). All the physical and chemical parameters did not show significant correlation with both protozoa. In future, viability status and molecular characterisation of Giardia and Cryptosporidium should be applied to identify species and genotypes/subgenotypes for better understanding of the epidemiology of these waterborne parasites.
    Matched MeSH terms: Rivers/parasitology*
  17. Fulltext Quantification of parasite clearance in Plasmodium knowlesi infections
    T Thurai Rathnam J, Grigg MJ, Dini S, William T, Sakam SS, Cooper DJ, et al.
    Malar J, 2023 Feb 14;22(1):54.
    PMID: 36782162 DOI: 10.1186/s12936-023-04483-9
    BACKGROUND: The incidence of zoonotic Plasmodium knowlesi infections in humans is rising in Southeast Asia, leading to clinical studies to monitor the efficacy of anti-malarial treatments for knowlesi malaria. One of the key outcomes of anti-malarial drug efficacy is parasite clearance. For Plasmodium falciparum, parasite clearance is typically estimated using a two-stage method, that involves estimating parasite clearance for individual patients followed by pooling of individual estimates to derive population estimates. An alternative approach is Bayesian hierarchical modelling which simultaneously analyses all parasite-time patient profiles to determine parasite clearance. This study compared these methods for estimating parasite clearance in P. knowlesi treatment efficacy studies, with typically fewer parasite measurements per patient due to high susceptibility to anti-malarials.

    METHODS: Using parasite clearance data from 714 patients with knowlesi malaria and enrolled in three trials, the Worldwide Antimalarial Resistance Network (WWARN) Parasite Clearance Estimator (PCE) standard two-stage approach and Bayesian hierarchical modelling were compared. Both methods estimate the parasite clearance rate from a model that incorporates a lag phase, slope, and tail phase for the parasitaemia profiles.

    RESULTS: The standard two-stage approach successfully estimated the parasite clearance rate for 678 patients, with 36 (5%) patients excluded due to an insufficient number of available parasitaemia measurements. The Bayesian hierarchical estimation method was applied to the parasitaemia data of all 714 patients. Overall, the Bayesian method estimated a faster population mean parasite clearance (0.36/h, 95% credible interval [0.18, 0.65]) compared to the standard two-stage method (0.26/h, 95% confidence interval [0.11, 0.46]), with better model fits (compared visually). Artemisinin-based combination therapy (ACT) is more effective in treating P. knowlesi than chloroquine, as confirmed by both methods, with a mean estimated parasite clearance half-life of 2.5 and 3.6 h, respectively using the standard two-stage method, and 1.8 and 2.9 h using the Bayesian method.

    CONCLUSION: For clinical studies of P. knowlesi with frequent parasite measurements, the standard two-stage approach (WWARN's PCE) is recommended as this method is straightforward to implement. For studies with fewer parasite measurements per patient, the Bayesian approach should be considered. Regardless of method used, ACT is more efficacious than chloroquine, confirming the findings of the original trials.

    Matched MeSH terms: Parasitemia/parasitology
  18. Fulltext Updating estimates of Plasmodium knowlesi malaria risk in response to changing land use patterns across Southeast Asia
    Tobin RJ, Harrison LE, Tully MK, Lubis IND, Noviyanti R, Anstey NM, et al.
    PLoS Negl Trop Dis, 2024 Jan;18(1):e0011570.
    PMID: 38252650 DOI: 10.1371/journal.pntd.0011570
    BACKGROUND: Plasmodium knowlesi is a zoonotic parasite that causes malaria in humans. The pathogen has a natural host reservoir in certain macaque species and is transmitted to humans via mosquitoes of the Anopheles Leucosphyrus Group. The risk of human P. knowlesi infection varies across Southeast Asia and is dependent upon environmental factors. Understanding this geographic variation in risk is important both for enabling appropriate diagnosis and treatment of the disease and for improving the planning and evaluation of malaria elimination. However, the data available on P. knowlesi occurrence are biased towards regions with greater surveillance and sampling effort. Predicting the spatial variation in risk of P. knowlesi malaria requires methods that can both incorporate environmental risk factors and account for spatial bias in detection.

    METHODS & RESULTS: We extend and apply an environmental niche modelling framework as implemented by a previous mapping study of P. knowlesi transmission risk which included data up to 2015. We reviewed the literature from October 2015 through to March 2020 and identified 264 new records of P. knowlesi, with a total of 524 occurrences included in the current study following consolidation with the 2015 study. The modelling framework used in the 2015 study was extended, with changes including the addition of new covariates to capture the effect of deforestation and urbanisation on P. knowlesi transmission.

    DISCUSSION: Our map of P. knowlesi relative transmission suitability estimates that the risk posed by the pathogen is highest in Malaysia and Indonesia, with localised areas of high risk also predicted in the Greater Mekong Subregion, The Philippines and Northeast India. These results highlight areas of priority for P. knowlesi surveillance and prospective sampling to address the challenge the disease poses to malaria elimination planning.

    Matched MeSH terms: Macaca/parasitology
  19. Population study of Spodoptera exigua (Lepidoptera: Noctuidae) larva and its affecting factors in Sekinchan, Selangor
    Azidah AA
    Pak J Biol Sci, 2007 Jul 01;10(13):2152-8.
    PMID: 19070174
    The aim of this study is to determine the Spodoptera exigua larva population in the field and factor affecting their density. Population study of S. exigua larva and its affecting factors was carried out in Sekinchan, Selangor during 2003-2004. The larval density was found fluctuating during the study, where the highest number of larvae was an averaged of 18.17 per m2, while the lowest number was an averaged of 1.5 per m2. The mean number of larvae per plant also varies from 1.83 to 5.42. It was found that the larval density was influenced by the age and availability of the host plant. A total of 1881 larvae were collected, where 18.29 and 20.31% were successfully becoming female and male moths, respectively; 20.63% was being parasitized, where 7.07, 11.43, 0.11 and 2.02% were being parasitized by Microplitis manilae, Chelonus sp., Temelucha sp. and Peribaea orbata, respectively. Besides that, other biotic factors such as fungal or bacterial infection also cause death to the S. exigua larva, where a total of 1.91 and 10.89% were infected by them, respectively. Whilst 16.64% of the collected larvae were dead due to pesticide and 7.44% were not known cause of the death. Besides that, 3.89% of the S. exigua died during pupal stage or emergence. Further, climatic factor was found not influencing the larva populations. There were no correlation between the number of larva collected with the means of temperature, relative humidity and rainfall.
    Matched MeSH terms: Crops, Agricultural/parasitology
  20. Hydatigera taeniaeformis in urban rats (Rattus rattus) in Faisalabad, Pakistan
    Alvi MA, Li L, Ohiolei JA, Qamar W, Saqib M, Tayyab MH, et al.
    Infect Genet Evol, 2021 Aug;92:104873.
    PMID: 33905888 DOI: 10.1016/j.meegid.2021.104873
    Hydatigera taeniaeformis formerly referred to as Taenia taeniaeformis is a cestode of cats (definitive hosts) and rodents (intermediate hosts). The prevalence of the metacestode larval stage has been reported in rodents in many parts of the world even though the genetic polymorphisms or intraspecies variation is still understudied. Here, we report a prevalence of 22.09% (38/172) from an urban rodent population in Pakistan and a nucleotide diversity (cox1) of 0.00463 among the population. Infection was higher in male (27.85%) and adult (32.29%) rats than female and sub-adult/young rats. Interestingly, The median-joining network and phylogenetic construction comprising isolates from China, Japan, Kenya, Laos, Malaysia, Senegal, the United Arab Emirates, and countries in Europe demonstrated that Pakistani H. taeniaeformis are closer to Asian and African population than those of European origin. The results of the study will add-in preliminary data for H. taeniaeformis and will also contribute to understand the global molecular epidemiology and population structure of H. taeniaeformis.
    Matched MeSH terms: Cestode Infections/parasitology
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