Displaying publications 1 - 20 of 122 in total

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  1. Hew YX, Ya'cob Z, Chen CD, Lau KW, Sofian-Azirun M, Muhammad-Rasul AH, et al.
    Acta Trop, 2024 Feb;250:107097.
    PMID: 38097150 DOI: 10.1016/j.actatropica.2023.107097
    Mitochondrial cytochrome c oxidase subunit I (COI) sequences were utilized to infer the population genetic structure of Simulium (Gomphostilbia) atratum De Meijere, an endemic simulid species to Indonesia. Both median-joining haplotype network and maximum-likelihood tree revealed two genetic lineages (A and B) within the species, with an overlap distribution in Lombok, which is situated along Wallace's line. Genetic differentiation and gene flow with varying frequencies (FST = 0.02-0.967; Nm = 0.01-10.58) were observed between populations of S. (G.) atratum, of which population pairs of different lineages showed high genetic differentiation. Notably, the high genetic distance of up to 5.92 % observed within S. (G.) atratum in Lombok was attributed to the existence of two genetically distinct lineages. The co-occurrence of distinct lineages in Lombok indicated that Wallace's line did not act as faunistic border for S. (G.) atratum in the present study. Moreover, both lineages also exhibited unimodal distributions and negative values of neutrality tests, suggesting a pattern of population expansion. The expansion and divergence time estimation suggested that the two lineages of S. (G.) atratum diverged and expanded during the Pleistocene era in Indonesia.
  2. Wan-Norafikah O, Aliah-Diyanah S, Atiqah-Izzah Z, Chen CD, Sofian-Azirun M, Lailatul-Nadhirah A, et al.
    Exp Parasitol, 2023 Nov;254:108627.
    PMID: 37802180 DOI: 10.1016/j.exppara.2023.108627
    Temephos is the World Health Organization (WHO) recommended larvicide and is still being utilized worldwide to control larvae of dengue vectors; Aedes aegypti and Aedes albopictus. The efficacy of a commercial temephos product; Temebate® to exterminate the local populations of Ae. albopictus larvae originated from different land use particularly dengue-risk and dengue-free housing localities as well as agrarian localities including oil palm plantations, rubber estates and paddy fields was assessed to verify its bioefficacy in these localities. Field populations of Ae. albopictus larvae were attained via a larval survey at each study locality. Each Ae. albopictus larval population was subjected to a 24-h larval bioassay using Temebate® at operational dosage of 1 mg/L. Almost all Ae. albopictus larval populations demonstrated mortalities between 7.00% and 100.00% by the end of the first 4 h of Temebate® exposure with the resistance ratios between 0.94 and 8.33. After 24 h of Temebate® exposure, all sixteen Ae. albopictus larval populations exhibited increased mortalities with ten of them showing 100% mortalities. These results confirmed the relevance of Temebate® to be continuously used by the residents of these localities as their control efforts against dengue vectors. Nevertheless, Temebate® application by consumers in dengue-risk localities need to be carefully monitored to prevent further development of temephos resistance among Ae. albopictus populations and substantiated with other vector control approaches.
  3. Wan-Norafikah O, Chen CD, Sofian-Azirun M
    Trop Biomed, 2023 Sep 01;40(3):320-330.
    PMID: 37897165 DOI: 10.47665/tb.40.3.008
    The susceptibility levels of Malaysian Aedes albopictus larvae sampled from several agricultural, fogging-free residential and dengue prone residential areas against different larvicides were evaluated using revised diagnostic doses derived from the 2xLC99 values of the reference strain. Upon 24-hour recovery period of WHO larval bioassay, incipient resistance was observed among Ae. albopictus larvae from rubber estates against fenitrothion (96.67% mortality) and permethin (97.00% mortality) while Ae. albopictus larvae from rice cultivation areas were moderately resistant to fenthion (94.33% mortality). Aedes albopictus larvae from dengue prone residential areas developed moderate to high resistance against dichlorodiphenyltrichloroethane (DDT), fenitrothion, fenthion, propoxur and permethrin (79.67% - 97.33% mortality). Moderate to high resistance were also demonstrated among all populations of Ae. albopictus larvae against temephos and chlorpyrifos (63.00% - 97.67% mortality). Except for Ae. albopictus larvae from oil palm plantations, all Ae. albopictus larval populations were also highly resistant to bendiocarb (65.67% - 89.67% mortality). Cross resistance between larvicides from similar and different insecticide classes were also revealed in this study. The use of revised diagnostic doses established from the local reference strain could reduce the possibility of underestimation or overestimation of the insecticide susceptibility status of field strain populations.
  4. Putt QY, Ya'cob Z, Adler PH, Chen CD, Hew YX, Izwan-Anas N, et al.
    Parasit Vectors, 2023 Aug 07;16(1):266.
    PMID: 37545007 DOI: 10.1186/s13071-023-05892-0
    BACKGROUND: Prompt and precise identification of black flies (Simuliidae) is crucial, given their biting behaviour and significant impact on human and animal health. To address the challenges presented by morphology and chromosomes in black fly taxonomy, along with the limited availability of molecular data pertaining to the black fly fauna in Vietnam, this study employed DNA-based approaches. Specifically, we used mitochondrial and nuclear-encoded genes to distinguish nominal species of black flies in Vietnam.

    METHODS: In this study, 135 mitochondrial cytochrome c oxidase subunit I (COI) sequences were established for 45 species in the genus Simulium in Vietnam, encompassing three subgenera (Gomphostilbia, Nevermannia, and Simulium), with 64 paratypes of 27 species and 16 topotypes of six species. Of these COI sequences, 71, representing 27 species, are reported for the first time.

    RESULTS: Combined with GenBank sequences of specimens from Malaysia, Myanmar, Thailand, and Vietnam, a total of 234 DNA barcodes of 53 nominal species resulted in a 71% success rate for species identification. Species from the non-monophyletic Simulium asakoae, S. feuerborni, S. multistriatum, S. striatum, S. tuberosum, and S. variegatum species groups were associated with ambiguous or incorrect identifications. Pairwise distances, phylogenetics, and species delimitation analyses revealed a high level of cryptic diversity, with discovery of 15 cryptic taxa. The current study also revealed the limited utility of a fast-evolving nuclear gene, big zinc finger (BZF), in discriminating closely related, morphologically similar nominal species of the S. asakoae species group.

    CONCLUSION: This study represents the first comprehensive molecular genetic analysis of the black fly fauna in Vietnam to our knowledge, providing a foundation for future research. DNA barcoding exhibits varying levels of differentiating efficiency across species groups but is valuable in the discovery of cryptic diversity.

  5. Hew YX, Ya'cob Z, Adler PH, Chen CD, Lau KW, Sofian-Azirun M, et al.
    Parasit Vectors, 2023 Jul 22;16(1):248.
    PMID: 37480109 DOI: 10.1186/s13071-023-05875-1
    BACKGROUND: DNA barcoding is a valuable taxonomic tool for rapid and accurate species identification and cryptic species discovery in black flies. Indonesia has 143 nominal species of black flies, but information on their biological aspects, including vectorial capacity and biting habits, remains underreported, in part because of identification problems. The current study represents the first comprehensive DNA barcoding of Indonesian black flies using mitochondrial cytochrome c oxidase subunit I (COI) gene sequences.

    METHODS: Genomic DNA of Indonesian black fly samples were extracted and sequenced, producing 86 COI sequences in total. Two hundred four COI sequences, including 118 GenBank sequences, were analysed. Maximum likelihood (ML) and Bayesian inference (BI) trees were constructed and species delimitation analyses, including ASAP, GMYC and single PTP, were performed to determine whether the species of Indonesian black flies could be delineated. Intra- and interspecific genetic distances were also calculated and the efficacy of COI sequences for species identification was tested.

    RESULTS: The DNA barcodes successfully distinguished most morphologically distinct species (> 80% of sampled taxa). Nonetheless, high maximum intraspecific distances (3.32-13.94%) in 11 species suggested cryptic diversity. Notably, populations of the common taxa Simulium (Gomphostilbia) cheongi, S. (Gomphostilbia) sheilae, S. (Nevermannia) feuerborni and S. (Simulium) tani in the islands of Indonesia were genetically distinct from those on the Southeast Asian mainland (Malaysia and Thailand). Integrated morphological, cytogenetic and nuclear DNA studies are warranted to clarify the taxonomic status of these more complex taxa.

    CONCLUSIONS: The findings showed that COI barcoding is a promising taxonomic tool for Indonesian black flies. The DNA barcodes will aid in correct identification and genetic study of Indonesian black flies, which will be helpful in the control and management of potential vector species.

  6. Lourdes EY, Low VL, Izwan-Anas N, Dawood MM, Sofian-Azirun M, Takaoka H, et al.
    Parasitol Int, 2023 Jun;94:102733.
    PMID: 36693472 DOI: 10.1016/j.parint.2023.102733
    Mermithids are the most common parasites of black flies and are associated with host feminization and sterilization in infected hosts. However, information on the species / lineage of black fly mermithids in Southeast Asia, including Malaysia requires further elucidation. In this study, mermithids were obtained from black fly larvae collected from 138 freshwater stream sites across East and West Malaysia. A molecular approach based on nuclear-encoded 18S ribosomal RNA (18S rRNA) gene was used to identify the species identity / lineage of 77 nematodes successfully extracted and sequenced from the specimens collected. Maximum likelihood and neighbor-joining phylogenetic analyses demonstrated five distinct mermithid lineages. Four species delimitation analyses: automated simultaneous analysis phylogenetics (ASAP), maximum likelihood Poisson tree processes with Bayesian inferences (bPTP_ML), generalized mixed yule coalescent (GMYC) and single rate Poisson tree processes (PTP) were applied to delimit the species boundaries of mermithid lineages in this data set along with genetic distance analysis. Data analysis supports five distinct lineages or operational taxonomic units for mermithids in the present study, with two requiring further investigation as they may represent intraspecific variation or closely related taxa. One mermithid lineage was similar to that previously observed in Simulium nigrogilvum from Thailand. Co-infection with two mermithids of different lineages was observed in one larva of Simulium trangense. This study represents an important first step towards exploring other aspects of host - parasite interactions in black fly mermithids.
  7. Azratul-Hizayu T, Chen CD, Lau KW, Azrizal-Wahid N, Tan TK, Lim YAL, et al.
    Parasitol Int, 2022 Feb;86:102483.
    PMID: 34678492 DOI: 10.1016/j.parint.2021.102483
    This study examines the biological efficacy of four mosquito mat vaporizers each containing different active ingredients: prallethrin with PBO, dimefluthrin, prallethrin, and d-allethrin. The glass chamber assay was used to evaluate their efficacy on Aedes albopictus (Skuse) (Diptera: Culicidae) from nine districts in Selangor, Malaysia. Aedes albopictus exhibited different knockdown rates, with 50% knockdown times, KT50, varying from 1.19 to 2.00 min, 1.22 to 2.20 min, 1.39 to 5.85 min, and 1.39 to 1.92 min for prallethrin with PBO, dimefluthrin, prallethrin and d-allethrin, respectively. In general, all populations of Ae. albopictus were completely knocked down after exposure to all active ingredients except Hulu Selangor population, which showed 96.00% knockdown against d-allethrin. On the contrary, mortality rates were observed from 84.00-100.00%, 84.00-100.00%, 90.67-100.00% and 90.67-100.00% in populations tested with prallethrin with PBO, dimefluthrin, prallethrin and d-allethrin, respectively. Moreover, significant correlations between mortality rates of prallethrin with PBO vs dimefluthrin (r = 0.836, P = 0.003), prallethrin with PBO vs prallethrin (r = 0.760, P = 0.011), and prallethrin vs d-allethrin (r = 0.694, P = 0.026) were also observed, suggesting cross-resistance among pyrethroids. d-allethrin was found to be high in insecticidal activity, followed by prallethrin, prallethrin with PBO, and dimefluthrin. In consistent with mortality due to insecticide exposure, elevated levels of enzyme activities were also demonstrated in Sabak Bernam, Hulu Selangor, Gombak, Petaling, Hulu Langat and Klang populations.
  8. Elia-Amira NMR, Chen CD, Low VL, Lau KW, Haziqah-Rashid A, Amelia-Yap ZH, et al.
    J Med Entomol, 2022 01 12;59(1):301-307.
    PMID: 34459477 DOI: 10.1093/jme/tjab146
    The efficacy of three groups of insect growth regulators, namely juvenile hormone mimics (methoprene and pyriproxyfen), chitin synthesis inhibitors (diflubenzuron and novaluron), and molting disruptor (cyromazine) was evaluated for the first time, against Aedes albopictus Skuse (Diptera: Culicidae) larvae from 14 districts in Sabah, Malaysia. The results showed that all field populations of Ae. albopictus were susceptible towards methoprene, pyriproxyfen, diflubenzuron, novaluron, and cyromazine, with resistance ratio values ranging from 0.50-0.90, 0.60-1.00, 0.67-1.17, 0.71-1.29, and 0.74-1.07, respectively. Overall, the efficacy assessment of insect growth regulators in this study showed promising outcomes and they could be further explored as an alternative to conventional insecticides.
  9. Lau KW, Chen CD, Low VL, Lee HL, Azidah AA, Sofian-Azirun M
    J Med Entomol, 2021 11 09;58(6):2292-2298.
    PMID: 33999147 DOI: 10.1093/jme/tjab093
    Resistance status of Aedes albopictus (Skuse) from 13 districts in Sarawak State, Malaysia, was evaluated against four major classes of adulticides, namely organochlorine, organophosphate, carbamate, and pyrethroid. Adult bioassays were performed according to the World Health Organization (WHO) standard protocols to assess knockdown and mortality rates of Ae. albopictus. Among the tested pyrethroids, only cyfluthrin was able to exhibit complete knockdown. On the other hand, different susceptibility and resistance patterns were observed in other adulticides. As for mortality rates, the mosquitoes were susceptible to cyfluthrin and dieldrin but exhibited various susceptibilities to other tested adulticides. Cross-resistance was discovered within and between tested insecticide classes. Significant correlations were found within pyrethroid and carbamate classes (i.e., bendiocab and propoxur, P = 0.036; etofenprox and permethrin, P = 0.000; deltamethrin and lambda-cyhalothrin, P = 0.822; deltamethrin and permethrin, P = 0.042). Additionally, insecticides belonging to different groups were also found significantly correlated (i.e., malathion and deltamethin, P = 0.019; malathion and bendiocarb, P = 0.008; malathion and propoxur, P = 0.007; and bendiocarb and deltamethrin, P = 0.031). In conclusion, cyfluthrin was effective for Aedes albopictus control in Sarawak State and these data may assist local authorities to improve future vector control operations.
  10. Azrizal-Wahid N, Sofian-Azirun M, Low VL, Chen CD, Shohaimi S
    J Appl Anim Welf Sci, 2021 Sep 07.
    PMID: 34493142 DOI: 10.1080/10888705.2021.1975539
    A structured questionnaire was distributed to a total of 531 cat owners in Peninsular Malaysia to evaluate their perceptions toward fleas and flea-borne diseases (FBD) using a knowledge-attitude-practice (KAP) approach. This study showed that majority of cat owners (50.5%) had a moderate level of knowledge on fleas, while 65.3% of them had a relatively low level of knowledge on FBD. However, most of them had positive attitudes (87.9%) and good practices (94.5%) toward efforts on prevention from flea infestation and FBD. Statistical analysis showed significant associations between knowledge on fleas and FBD toward demographic and pet ownership profiles of the respondents. Educated cat owners from urban area were more likely to have positive attitudes toward prevention of fleas and FBD. Female cat owners with monthly income of RM 5,001-7,000 ($1143-1600) were more likely to have good practices. Middle-aged cat owners showed the highest odds toward both positive attitudes and good practices. Correlation analyses indicated significant linear relationships between both knowledge, which were also associated with attitudes, but not with practices.
  11. Azratul-Hizayu T, Chen CD, Lau KW, Azrizal-Wahid N, Tan TK, Lim YAL, et al.
    Trop Biomed, 2021 Sep 01;38(3):327-337.
    PMID: 34508340 DOI: 10.47665/tb.38.3.073
    This study aims to examine the efficacy of mosquito mat vaporizers on Aedes aegypti and their associated metabolic detoxication mechanisms. For this purpose, Aedes aegypti (Linnaeus) was collected from nine districts in Selangor, Malaysia and tested with mosquito vaporizing mat bioassays. The same populations were also subjected to biochemical assays to investigate activities of detoxifying enzymes, namely non-specific esterase (EST), glutathione-S-transferase (GST) and mixed function oxidase (MFO). The efficacy of Ae. aegypti on the active ingredients tested in decreasing order were d- allethrin > dimefluthrin > prallethrin with PBO > prallethrin. The results further indicated significant enhancement mean levels of EST, GST and MFO in pyrethroid-resistant populations. The mortality rate of Ae. aegypti in response to pyrethroid active ingredients was associated with MFO activity, suggesting it is an important detoxification enzyme for the populations tested. In view of the presence of resistance against household insecticide products, pyrethroid efficacy on Ae. aegypti populations needs to be monitored closely to ensure the implementation of an effective vector control program in Malaysia.
  12. Lee HY, Loong SK, Ya'cob Z, Low VL, Teoh BT, Ahmad-Nasrah SN, et al.
    Acta Trop, 2021 Jul;219:105923.
    PMID: 33878305 DOI: 10.1016/j.actatropica.2021.105923
    Although the microbiome of blood-feeding insects serves an integral role in host physiology, both beneficial and pathogenic, little is known of the microbial community of black flies. An investigation, therefore, was undertaken to identify culturable bacteria from one of Malaysia's most common black flies, Simulium tani Takaoka and Davies, using 16S rDNA sequencing, and then evaluate the isolates for antibiotic resistance and virulence genes. A total of 20 isolates representing 11 bacterial species in four genera were found. Five isolates showed β-hemolysis on Columbia agar, and virulence genes were found in three of these isolates. Some degree of resistance to six of the 12 tested antibiotics was found among the isolates. The baseline data from this study suggest rich opportunities for comparative studies exploring the diversity and roles of the microbiome of S. tani and other Southeast Asian black flies.
  13. Elia-Amira NMR, Chen CD, Low VL, Lau KW, Haziqah-Rashid A, Amelia-Yap ZH, et al.
    Trop Biomed, 2021 Jun 01;38(2):196-204.
    PMID: 34172711 DOI: 10.47665/tb.38.2.058
    Susceptibility status of Aedes albopictus (Skuse) sampled from residential areas in Interior, Sandakan and Tawau divisions of Sabah, Malaysia, was evaluated based on the WHOrecommended doses of organochlorine and organophosphate larvicides. To determine susceptibility status, larval bioassays were carried out and post 24-hour mortalities based on WHO resistance classifications were adopted. The results demonstrated that Ae. albopictus larvae were resistant toward 5 out of the 8 larvicides tested. Larvae from all populations were resistant against bromophos, fenitrothion, malathion, temephos and dichlorodiphenyltrichloroethane (DDT), with mortalities ranging from 0.00 to 89.33%. Dieldrin, on the other hand, could induce 100.00% mortalities in all populations, followed by fenthion and chlorpyrifos, with mortalities ranging from 97.33 to 100.00% and 81.33 to 100.00% respectively. Despite most populations exhibiting similitude in their resistance status, larvae from Sandakan exhibited the highest resistance level whereas the lowest level was observed in Keningau. In view of the inadequacy of some larvicides in controlling Ae. albopictus in this study, integrated management such as insecticide rotation or combination of interventions is warranted.
  14. Azrizal-Wahid N, Sofian-Azirun M, Low VL
    PMID: 33609991 DOI: 10.1016/j.cimid.2021.101621
    Flea-borne pathogens were screened from 100 individual cat fleas using a PCR approach, of which 38 % were infected with at least one bacterium. Overall, 28 % of the flea samples were positive for Bartonella as inferred from ITS DNA region. Of these, 25 % (7/28) were identified as Bartonella clarridgeiae, 42.9 % (12/28) as Bartonella henselae consisted of two different strains, and 32.1 % (9/28) as Bartonella koehlerae, which was detected for the first time in Malaysia. Sequencing of gltA amplicons detected Rickettsia DNA in 14 % of cat flea samples, all of them identified as Rickettsia asembonensis (100 %). None of the flea samples were positive for Mycoplasma DNA in 16S rRNA gene detection. Four fleas were co-infected with Bartonella and Rickettsia DNAs. Statistical analyses reveal no significant association between bacterial infection and mtDNA diversity of the cat flea. Nevertheless, in all types of pathogen infections, infected populations demonstrated lower nucleotide and haplotype diversities compared to uninfected populations. Moreover, lower haplotype numbers were observed in infected populations.
  15. Wan-Norafikah O, Chen CD, Sofian-Azirun M
    Saudi J Biol Sci, 2021 Jan;28(1):1010-1016.
    PMID: 33424394 DOI: 10.1016/j.sjbs.2020.11.040
    Aedes albopictus larvae obtained from different types of agricultural and non-agricultural localities in Peninsular Malaysia were subjected to several larvicides at World Health Organization (WHO) recommended dosages. Upon 24 h of WHO larval bioassay using two organochlorines and six organophosphates, high resistance against dichlorodiphenyltrichloroethane (DDT), temephos, chlorpyrifos and bromophos were demonstrated among all larval populations. Aedes albopictus larvae from both paddy growing areas (92.33% mortality) and rubber estates (97.00% mortality) were moderately resistant to dieldrin while only Ae. albopictus larvae from dengue prone residential areas (89.00% mortality) showed high resistance against dieldrin. All Ae. albopictus larval populations also developed either incipient or high resistance to both malathion (33.67%-95.33% mortality) and fenitrothion (73.00%-92.67% mortality). Only Ae. albopictus larvae from fogging-free residential areas that were tolerant to fenthion (97.33% mortality), whereas Ae. albopictus larvae from dengue prone residential areas were highly resistant to the same organophosphate (88.33% mortality). Cross resistance between intraclass and interclass larvicides of organochlorines and organophosphates were also exhibited in this study. The present study provided baseline data on various susceptibility levels of Ae. albopictus larval populations from different types of agricultural and non-agricultural localities against organochlorines and organophosphates at WHO recommended dosages. Nevertheless, further susceptibility investigations are suggested using revised doses of larvicides established from the local reference strain of Ae. albopictus to prevent the underestimation or overestimation of insecticide resistance level among Ae. albopictus field strains of larvae.
  16. Amelia-Yap ZH, Tan TK, Prakash BK, Chen CD, Sofian-Azirun M, Low VL
    J Vector Borne Dis, 2020 10 1;57(4):359-361.
    PMID: 34856717 DOI: 10.4103/0972-9062.313959
  17. Takaoka H, Sofian-Azirun M, Chen CD, Halim MRA, Lau KW, Low VL, et al.
    Trop Biomed, 2020 Sep 01;37(3):683-690.
    PMID: 33612782 DOI: 10.47665/tb.37.3.683
    Simulium (Simulium) contractum Takaoka from Sulawesi, Indonesia was known only as the pupa. Its female, male and mature larva are described for the first time. The tentative assignment of this species in the Simulium dumogaense species-group is confirmed by the adult characters including the female and male genitalia. The female and male of this species are similar to those of Simulium (Simulium) tumpaense Takaoka and Roberts but are distinguished by the yellowish femora.
  18. Azrizal-Wahid N, Sofian-Azirun M, Low VL
    Vet Parasitol, 2020 May;281:109102.
    PMID: 32289653 DOI: 10.1016/j.vetpar.2020.109102
    The present study investigated the genetic profile of the cosmopolitan cat flea, Ctenocephalides felis (Siphonaptera: Pulicidae) from Malaysia and the reference data available in the National Center for Biotechnology Information (NCBI) GenBank. A set of sequences of 100 Malaysian samples aligned as 550 characters of the cytochrome c oxidase subunit I (cox1) and 706 characters of the II (cox2) genes revealed ten haplotypes (A1-A10) and eight haplotypes (B1-B8), respectively. The concatenated sequences of cox1 and cox2 genes with a total of 1256 characters revealed 15 haplotypes (AB1-AB15). Analyses indicated that haplotype AB1 was the most frequent and the most widespread haplotype in Malaysia. Overall haplotype and nucleotide diversities of the concatenated sequences were 0.52909 and 0.00424, respectively, with moderate genetic differentiation (FST = 0.17522) and high gene flow (Nm = 1.18). The western population presented the highest genetic diversity (Hd = 0.78333, Pi = 0.01269, Nh = 9), whereas the southern population demonstrated the lowest diversity (Hd = 0.15667, Pi = 0.00019, Nh = 3). The concatenated sequences showed genetic distances ranged from 0.08 % to 4.39 %. There were three aberrant haplotypes in cox2 sequences that highly divergent, suggesting the presence of cryptic species or occurrence of introgression. In the global point of view, the aligned sequences of C. felis revealed 65 haplotypes (AA1-AA65) by the cox1 gene (n = 586), and 27 haplotypes (BB1-BB27) by the cox2 gene (n = 204). Mapping of the haplotype network showed that Malaysian C. felis possesses seven unique haplotypes in both genes with the common haplotypes demonstrated genetic affinity with C. felis from Southeast Asia for cox1 and South America for cox2. The topologies of cox1 and cox2 phylogenetic trees were concordant with relevant grouping pattern of haplotypes in the network but revealed two major lineages by which Malaysian haplotypes were closely related with haplotypes from the tropical region.
  19. Azrizal-Wahid N, Sofian-Azirun M, Low VL
    Trop Biomed, 2019 Dec 01;36(4):810-821.
    PMID: 33597453
    Fleas are the common cause of skin disorders in cats. They are well-known for transmitting various pathogens to both cats and humans. Accordingly, this study was conducted to gain insights on the risk factors associated with flea infestation on cats. Flea combing conducted on 426 cats from four distinct regions in Peninsular Malaysia revealed a relatively high rate of flea infestation on 306 cats (71.83%). A total of 651 fleas were collected, all of them were identified as Ctenocephalides felis with the total intensity of 2.13 and abundance of 1.53. The sex ratio of fleas was female-biased at 2.5:1 (♀=464, ♂=187). Statistical analysis of the data revealed that flea infestation was significantly (P<0.05) associated with several risk factors including region, age, weight, status (stray, sheltered, pet), body condition, and hair length. Higher flea prevalence was also observed in female cats (77.99%), big-sized cats (91.76%), stray cats (84.94%), cats with clean body condition (73.35%), and cats with long hairs (78.38%) as compared to their contemporaries within the same comparison variables. The high infestation of fleas in this study is indicative of cats as a flea reservoir particularly C. felis. Thus the findings of this study and the knowledge gained on the risk factors can be used to develop and improve control measures and management of flea infestations.
  20. Suhana O, Nazni WA, Apandi Y, Farah H, Lee HL, Sofian-Azirun M
    Heliyon, 2019 Dec;5(12):e02682.
    PMID: 31867449 DOI: 10.1016/j.heliyon.2019.e02682
    Chikungunya virus (CHIKV) is maintained in the sylvatic cycle in West Africa and is transmitted by Aedes mosquito species to monkeys. In 2006, four verified CHIKV isolates were obtained during a survey of arboviruses in monkeys (Macaca fascicularis) in Pahang state, Peninsular Malaysia. RNA was extracted from the CHIKV isolates and used in reverse transcription polymerase chain reactions (RT-PCR) to amplify PCR fragments for sequencing. Nucleic acid primers were designed to generate overlapping PCR fragments that covered the whole viral sequence. A total of 11,238 base pairs (bp) corresponding to open reading frames (ORFs) from our isolates and 47 other registered isolates in the National Center for Biotechnology Information (NCBI) were used to elucidate sequences, amino acids, and phylogenetic relationships and to estimate divergence times by using MEGA 7.0 and the Bayesian Markov chain Monte Carlo method. Phylogenetic analysis revealed that all CHIKV isolates could be classified into the Asian genotype and clustered with Bagan Panchor clades, which are associated with the chikungunya outbreak reported in 2006, with sequence and amino acid similarities of 99.9% and 99.7%, respectively. Minor amino acid differences were found between human and non-human primate isolates. Amino acid analysis showed a unique amino acid at position 221 in the nsP1region, at which a glycine (G) was found only in monkey isolates, whereas arginine (R) was found at the same position only in human isolates. The time to the most recent common ancestor (MRCA) estimation indicated that CHIKV probably started to diverge from human to non-human primates in approximately 2004 in Malaysia. The results suggested that CHIKV in non-human primates probably resulted from the spillover of the virus from humans. The study will be helpful in understanding the movement and evolution of CHIKV in Malaysia and globally.
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