Displaying publications 121 - 140 of 163 in total

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  1. Morphological description and phylogenetic position of a new cryptic species in the Simulium asakoae species-group, Simulium (Gomphostilbia) mokroense, from Western Thailand
    Srisuka W, Aupalee K, Fukuda M, Saeung A, Takaoka H
    Acta Trop, 2022 Jan 14;228:106313.
    PMID: 35038426 DOI: 10.1016/j.actatropica.2022.106313
    Adult females and males reared from pupae of Simulium sp. from Tak Province and those of S. chiangdaoense Takaoka & Srisuka from four localities in Chiang Mai and Lampang Provinces, northern Thailand, were molecularly and morphologically compared. Simulium sp. is morphologically almost indistinguishable from S. chiangdaoense except the hair tuft at the base of the radius of the adult female and male, which is composed of yellow and dark hairs (in place of yellow hairs only). Molecular analysis using COI gene sequences shows that S. sp. formed a distinct clade and was separated from S. chiangdaoense by a genetic distance of 1.56-2.44%. Based on the results of morphological and molecular analyzes, S. sp. is described as a new species, S. mokroense, from females, males, pupae and mature larvae. It is also found that S. chiangdaoense is genetically diverse, with five lineages, and is morphologically variable in the number of male upper-eye (large) facets, which are in 13 to 17 vertical columns and 14 to 17 horizontal rows on each side. This is a first case, in which the difference in the color of the wing tuft hairs is a clue leading to the discovery of a new cryptic species close to S. chiangdaoense.
  2. Bibliometric analysis of schistosomiasis research in Southeast Asia (1908-2020)
    Tantengco OAG, Rojo RD
    Acta Trop, 2022 Jan 20;228:106322.
    PMID: 35065014 DOI: 10.1016/j.actatropica.2022.106322
    OBJECTIVES: This study determined the characteristics and trends of published articles regarding schistosomiasis in Southeast Asian countries through a bibliometric analysis.

    METHODS: Using the Scopus database, we identified all original research articles on schistosomiasis from 1908 to 2020 from SEA countries: Brunei, Cambodia, Indonesia, Laos, Malaysia, Myanmar, Philippines, Singapore, Thailand, and Vietnam. Bibliographic and citation information was obtained, and visualization of collaboration networks of countries and keywords related to schistosomiasis was conducted using VOSviewer software.

    RESULTS: We obtained 528 schistosomiasis articles published between 1908 and 2020 from SEA countries. The number of publications continued to increase and peaked from 2000 until 2020. The Philippines had the highest number of publications (n = 231), followed by Thailand (n = 153), and Malaysia (n = 64). The leading journals with the highest number of publications in this field include the Southeast Asian Journal of Tropical Medicine and Public Health (n = 96), Acta Tropica (n = 27), and Plos Neglected Tropical Diseases (n = 24). The most common keywords related to schistosomiasis research in SEA were "schistosomiasis", "Schistosoma japonicum", "Schistosoma mekongi", "Schistosoma mansoni", and "praziquantel". International collaboration was significantly correlated with scientific productivity for schistosomiasis research.

    CONCLUSION: Our study showed the research landscape, trends and development, and collaboration among researchers in schistosomiasis in SEA. Our results also revealed the limited schistosomiasis research in several SEA countries. There is a need for more research to improve our understanding of the epidemiology of schistosomiasis in SEA, which can help in improving the control and prevention of this disease.

  3. Fulltext Camellia sinensis solvent extract, epigallocatechin gallate and caffeine confer trophocidal and cysticidal effects against Acanthamoeba castellanii
    Fakae LB, Harun MSR, Ting DSJ, Dua HS, Cave GWV, Zhu XQ, et al.
    Acta Trop, 2023 Jan;237:106729.
    PMID: 36280206 DOI: 10.1016/j.actatropica.2022.106729
    We examined the anti-acanthamoebic efficacy of green tea Camellia sinensis solvent extract (SE) or its chemical constituents against Acanthamoeba castellanii by using anti-trophozoite, anti-encystation, and anti-excystation assays. C. sinensis SE (625-5000 µg/mL) inhibited trophozoite replication within 24-72 h. C. sinensis SE exhibited a dose-dependent inhibition of encystation, with a marked cysticidal activity at 2500-5000 µg/mL. Two constituents of C. sinensis, namely epigallocatechin-3-gallate and caffeine, at 100 μM and 200 μM respectively, significantly inhibited both trophozoite replication and encystation. Cytotoxicity analysis showed that 156.25-2500 µg/mL of SE was not toxic to human corneal epithelial cells, while up to 625 µg/mL was not toxic to Madin-Darby canine kidney cells. This study shows the anti-acanthamoebic potential of C. sinensis SE against A. castellanii trophozoites and cysts. Pre-clinical studies are required to elucidate the in vivo efficacy and safety of C. sinensis SE.
  4. Field efficacy of palm oil-based nanoemulsion insecticides against Aedes aegypti in Malaysia
    Shaari A, Yunus R, Raman IA, Omar D, Shahar MK, Awang Biak DR, et al.
    Acta Trop, 2021 Dec;224:106107.
    PMID: 34450061 DOI: 10.1016/j.actatropica.2021.106107
    This study evaluates the efficacy of palm oil-based nanoemulsion insecticides in thermal fogging applications against adult Ae. aegypti. The nanoemulsion formulations contained a palm oil methyl ester solvent, water, a non-ionic surfactant, and active ingredient deltamethrin, with nanoemulsion droplet diameters ranging from 362 to 382 nm. Knockdown and mortality rates of caged mosquitoes were measured at various distances up to 18 m from the spray nozzle. After 15 min of insecticide exposure, nanoemulsion insecticides achieved a knockdown rate of >97% at a spraying distance of 4 m, and the knockdown effect increased substantially with exposure time. At an 18 m spraying distance, the best nanoemulsion formulation, NanoEW8, achieved a high mosquito mortality rate of more than 80%, whereas the non-nanoemulsion and the commercial product reached only 14 and 8 m distances, respectively, for comparable mortality. The artificial neural network (ANN) was used to predict the mosquito knockdown distribution over the spraying distances and time intervals. The models predicted that NanoEW8 can still cause knockdown at a maximum distance of 61.5 m from the discharge point 60 min after spraying. The results established that Ae. aegypti was susceptible to the newly developed palm oil-based nanoemulsion insecticide, indicating a high potential for mosquito control.
  5. Diversity of nematodes infecting the human-biting black fly species, Simulium nigrogilvum (Diptera: Simuliidae) in central Thailand
    Huang F, Srisuka W, Aupalee K, Streit A, Fukuda M, Pitasawat B, et al.
    Acta Trop, 2021 Dec;224:106140.
    PMID: 34562429 DOI: 10.1016/j.actatropica.2021.106140
    Black flies (Diptera: Simuliidae) are known as vectors of disease agents in humans and livestock, with some species being vectors of Onchocerca volvulus, the filarial nematode that is the causative agent of human onchocerciasis. Nematode infections in adult female black flies have been reported from some areas in northern and western Thailand, but not from other regions of Thailand. In this study, wild-caught adult female black flies from the central region of Thailand were examined for infections with nematodes. Collections of adult females were carried out at Khlong Lan district, Kamphaeng Phet province, central Thailand. A molecular approach, based on the mitochondrial (cox1, 12S rRNA) and nuclear (18S rRNA) genes, was used to identify the species of nematodes recovered from the specimens collected. A total of 911 wild-caught adult black flies were collected. Simulium nigrogilvum was the most abundant species (n = 708), followed by S. doipuiense complex (n = 179), S. chamlongi (n = 11), S. umphangense (n = 10), S. chumpornense (n = 1), S. multistriatum species-group (n = 1), and S. maewongense (n = 1). Nematode infections were detected in nine specimens of S. nigrogilvum, of which two were positive for filarial worms (one worm each, infection rate 0.28%) and seven were positive for non-filarial nematodes (11 worms in total, infection rate 0.99%). The two filarial nematodes (third-stage larvae) were identified molecularly as Onchocerca species type I, while the 11 non-filarial nematodes were classified into ascaridoid (n = 2), tylenchid (n = 6) and mermithid (n = 3) nematodes. The results of this study demonstrated that adult female S. nigrogilvum were parasitized with diverse nematodes (filarial and non-filarial). Detection of the infective larvae of Onchocerca sp. type I in S. nigrogilvum confirms that occurrence of zoonotic onchocerciasis is highly possible in Thailand. Additional in-depth investigation of the morphology, life cycle and host-parasite relationship of nematodes that parasitized this black fly host is still needed.
  6. Morphological and genetic revision of cytoform 'L' of the Simulium (Simulium) tani complex from Taiwan, and cytoform 'D' of the S. (S.) suzukii complex (Diptera: Simuliidae) from the Nansei Islands, Japan
    Takaoka H, Otsuka Y, Low VL, Adler PH, Fukuda M, Huang YT, et al.
    Acta Trop, 2021 Dec;224:106124.
    PMID: 34508715 DOI: 10.1016/j.actatropica.2021.106124
    The species status of two cytoforms of two species complexes in the Simulium (Simulium) tuberosum species-group, which are almost indistinguishable in the pupal stage, was morphologically and genetically evaluated. Cytoform 'L' of the S. (S.) tani Takaoka & Davies complex, previously recognized as S. (S.) suzukii Rubtsov in Taiwan, is described as a new species, S. (S.) jianshiense. It is morphologically distinguishable as adults from two members of the S. (S.) suzukii complex: cytoform 'C' from Hokkaido, selected to represent the type of S. (S.) suzukii sensu stricto, and cytoform 'D' from Okinawa Island and, based on our chromosomal analysis, also from Amami Island. This new species is genetically separated from both cytoforms of the S. (S.) suzukii complex with a genetic distance of 5.31-6.67%. Cytoform 'D' is distinguished from cytoform 'C' by the color of the male forecoxa and relative length of the female sensory vesicle to the third maxillary palpomere. Accordingly, the name S. (S.) ryukyuense Ogata, once regarded as a synonym of S. (S.) suzukii, is revalidated and applied to cytoform 'D'. The genetic distance between S. (S.) ryukyuense and S. (S.) suzukii sensu stricto is 1.24-1.60%.
  7. Redescription of Simulium (Gomphostilbia) omutaense Ogata & Sasa (Diptera: Simuliidae) from Japan and its phylogenetic relationship with other members of the S. batoense species-group
    Takaoka H, Fukuda M, Otsuka Y, Low VL, Ya'cob Z
    Acta Trop, 2022 Jan;225:106207.
    PMID: 34687650 DOI: 10.1016/j.actatropica.2021.106207
    Simulium (Gomphostilbia) omutaense Ogata & Sasa, 1954 is the only named species in the Simulium batoense species-group of the subgenus Gomphostilbia Enderlein recorded from Honshu and Kyushu, Japan. It represents the northernmost distribution of this species-group, of which most members are distributed in the Oriental region. This species, the only member of the Simulium omutaense subgroup, is unique among the seven subgroups of the S. batoense species-group by having the pupal gill with one long filament and seven short filaments, similar to the arrangement of the pupal gill filaments in the S. zonatum subgroup of the S. epistum species-group in the same subgenus. This species is fully redescribed based on adults, pupal exuviae and mature larvae, and is most similar to species of the S. decuplum subgroup, based on adult morphological characteristics, although the pupal gill of the latter subgroup is markedly different by having 10 or 12 short filaments. Its close relationship to the S. decuplum subgroup is supported by a DNA analysis using COI gene sequences, with genetic distances of 9.30-11.02%. On the other hand, genetic distances between S. (G.) omutaense and species of the S. zonatum subgroup were 16.32-16.93%. Our study shows that a similar arrangement of the pupal gills in two different species-groups, which is rarely seen, has evolved independently and its occurrence does not necessarily reflect phylogenetic relationships.
  8. Descriptions of two new species of the Simulium (Simulium) striatum species-group (Diptera: Simuliidae) from Taiwan and Japan, and a revised description of S. (S.) quinquestriatum (Shiraki)
    Takaoka H, Otsuka Y, Huang YT, Low VL, Fukuda M, Ya'cob Z
    Acta Trop, 2021 Dec 25;227:106293.
    PMID: 34958767 DOI: 10.1016/j.actatropica.2021.106293
    Species in the Simulium (Simulium) striatum species-group (Diptera: Simuliidae) in Taiwan and Japan are morphologically reevaluated. Simulium (S.) yanpingense sp. nov. is described as the third member in this species-group from Taiwan and a revised description of S. (S.) quinquestriatum (Shiraki) is provided. The species previously regarded as S. (S.) quinquestriatum in Japan is described as a new species, S. (S.) tanegashimaense. Simulium (S.) yanpingense sp. nov. is similar to S. (S.) pingtungense Huang & Takaoka from Taiwan, in many characteristics including the haired basal portion of the female radius, dark leg color, and male scutum with brassy hairs, but it is distinguished from the latter species by the number of male upper-eye (large) facets, which are in 17 (rarely 18) vertical columns and 17 or 18 horizontal rows in this new species but in 19 vertical columns and 20 horizontal rows in S. (S.) pingtungense. Simulium (S.) tanegashimaense sp. nov. is similar to S. (S.) quinquestriatum originally described from Taiwan by having the male scutum with yellow fine hairs, but is distinguished from the latter species by the number of male upper-eye (large) facets, which are in 17 (rarely 16) vertical columns and 17 horizontal rows in this new species but in 19 or 20 vertical columns and 19 or 20 horizontal rows in S. (S.) quinquestriatum. The morphological differences between these two new species and their related species from India, Malaysia, Thailand and Vietnam are noted.
  9. Varespladib (LY315920) rescued mice from fatal neurotoxicity caused by venoms of five major Asiatic kraits (Bungarus spp.) in an experimental envenoming and rescue model
    Tan CH, Lingam TMC, Tan KY
    Acta Trop, 2021 Dec 18;227:106289.
    PMID: 34929179 DOI: 10.1016/j.actatropica.2021.106289
    The venoms of Asiatic kraits (Bungarus spp.) contain various neurotoxic phospholipases A2 (beta-bungarotoxins) which can irreversibly damage motor nerve terminals, resulting in rapidly fatal suffocation by respiratory muscle paralysis or oral airway obstruction. Hence, there is a need of adjunct therapy at the pre-hospital stage to prevent or delay the onset of neurotoxicity, so that antivenom can be given within golden hour before the envenoming becomes antivenom-resistant. This study investigated the efficacy of varespladib, a small molecule PLA2 (phospholipase A2) inhibitor, given as a bolus subcutaneously upon the onset of krait venom-induced paralysis in a mouse experimental envenoming and rescue model, where the severity of neurotoxicity was scored and the survival rate was monitored over 24 h. Varespladib at 10 mg/kg effectively alleviated the neurotoxicity of Bungarus sindanus, Bungarus multicinctus and Bungarus fasciatus venoms, and rescued all mice from venom-induced lethality (100% survival). Varespladib at this dose, however, only partially reduced the neurotoxicity of Bungarus caeruleus and Bungarus candidus venoms, while all challenged mice were dead by 23 h (B. caeruleus) and 12 h (B. candidus). An increased dose of varespladib at 20 mg/kg markedly abated the venom neurotoxicity past 8 h of envenoming, and protected the mice from venom lethality (B. caeruleus: 75% survival; B. candidus: 100% survival). The finding is consistent with previous studies which demonstrated varespladib's inhibitory effect against some snake venoms. The findings suggest varespladib could be repurposed as an emergency drug for prevention or rescue (if given early enough) from the acute, neurotoxic envenoming syndromes caused by various major krait species in Asia.
  10. Presence of a predator image in potential breeding sites and oviposition responses of a dengue vector
    Dieng H, Satho T, Suradi NFB, Hakim H, Abang F, Aliasan NE, et al.
    Acta Trop, 2017 Dec;176:446-454.
    PMID: 28865898 DOI: 10.1016/j.actatropica.2017.08.033
    In dengue vector control, attempts to minimize or replace the use of pesticides have mostly involved use of predators, but success has been severely impeded by difficulties associated with financial and environmental costs, predator mass production, and persistence in target habitats. Visual deterrents have been used successfully to control animal pests, in some cases in an effort to replace pesticide use. Despite evidence that visual signals are crucial in site choice for egg deposition by dengue vectors, and that female mosquitoes respond to artificial predation, the role of predator intimidation as it affects the oviposition behavior of dengue vectors remains largely unexplored. Here, we examined the oviposition responses of Aedes aegypti exposed to various mosquito predator pictures. Gravid females were presented with equal opportunities to oviposit in two cups with predator images [Toxorhynchites splendens-TXI, Goldfish (Carassius auratus)-small (SFI) and large (LFI) and Tx. splendens+Goldfish-TXFI] and two others without pictures. Differences in egg deposition were examined between sites with and without these images. When given a chance to oviposit in cups with and without TXI, Ae. aegypti females were similarly attracted to both sites. When provided an opportunity to oviposit in cups displaying pictures of fish (SFI or LFI) and blank cups, egg deposition rates were much lower in the fish picture sites. Females showed a preference for blank cups over TXFI for egg deposition. They also equally avoided cups with pictures of fish, regardless of the size of the picture. Our results indicate that the presence of images of goldfish and their association with Tx. larvae significantly reduced egg deposition by Ae. aegypti, and this was not the case with the predatory larvae alone. The observations that the images of natural predators can repel gravid females of a dengue vector provide novel possibilities to develop effective and inexpensive alternative tools to harmful insecticides.
  11. Leptospirosis: Molecular trial path and immunopathogenesis correlated with dengue, malaria and mimetic hemorrhagic infections
    Priya SP, Sakinah S, Sharmilah K, Hamat RA, Sekawi Z, Higuchi A, et al.
    Acta Trop, 2017 Dec;176:206-223.
    PMID: 28823908 DOI: 10.1016/j.actatropica.2017.08.007
    Immuno-pathogenesis of leptospirosis can be recounted well by following its trail path from entry to exit, while inducing disastrous damages in various tissues of the host. Dysregulated, inappropriate and excessive immune responses are unanimously blamed in fatal leptospirosis. The inherent abilities of the pathogen and inabilities of the host were debated targeting the severity of the disease. Hemorrhagic manifestation through various mechanisms leading to a fatal end is observed when this disease is unattended. The similar vascular destructions and hemorrhage manifestations are noted in infections with different microbes in endemic areas. The simultaneous infection in a host with more than one pathogen or parasite is referred as the coinfection. Notably, common endemic infections such as leptospirosis, dengue, chikungunya, and malaria, harbor favorable environments to flourish in similar climates, which is aggregated with stagnated water and aggravated with the poor personal and environmental hygiene of the inhabitants. These factors aid the spread of pathogens and parasites to humans and potential vectors, eventually leading to outbreaks of public health relevance. Malaria, dengue and chikungunya need mosquitoes as vectors, in contrast with leptospirosis, which directly invades human, although the environmental bacterial load is maintained through other mammals, such as rodents. The more complicating issue is that infections by different pathogens exhibiting similar symptoms but require different treatment management. The current review explores different pathogens expressing specific surface proteins and their ability to bind with array of host proteins with or without immune response to enter into the host tissues and their ability to evade the host immune responses to invade and their affinity to certain tissues leading to the common squeal of hemorrhage. Furthermore, at the host level, the increased susceptibility and inability of the host to arrest the pathogens' and parasites' spread in different tissues, various cytokines accumulated to eradicate the microorganisms and their cellular interactions, the antibody dependent defense and the susceptibility of individual organs bringing the manifestation of the diseases were explored. Lastly, we provided a discussion on the immune trail path of pathogenesis from entry to exit to narrate the similarities and dissimilarities among various hemorrhagic fevers mentioned above, in order to outline future possibilities of prevention, diagnosis, and treatment of coinfections, with special reference to endemic areas.
  12. Occurrence of Acanthamoeba genotypes in Central West Malaysian environments
    Basher MHA, Ithoi I, Mahmud R, Abdulsalam AM, Foead AI, Dawaki S, et al.
    Acta Trop, 2018 Feb;178:219-228.
    PMID: 29203378 DOI: 10.1016/j.actatropica.2017.11.015
    Acanthamoeba species are ubiquitous free-living protozoa that can be found worldwide. Occasionally, it can become parasitic and the causative agent of acanthamoebic keratitis (AK) and Granulomatous Amoebic Encephalitis (GAE) in man. A total of 160 environmental samples and 225 naturally-infected animal corneal swabs were collected for Acanthamoeba cultivation. Acanthamoeba was found to be high in samples collected from environments (85%, 136/160) compared to infected animal corneas (24.89%, 56/225) by microscopic examination. Analysis of nucleotide sequence of 18S rRNA gene of all the 192 cultivable Acanthamoeba isolates revealed 4 genotypes (T3, T4. T5 and T15) with T4 as the most prevalent (69.27%, 133/192) followed by T5 (20.31%), T15 (9.90%) and T3 (0.52%). Genotype T4 was from the strain of A. castellanii U07401 (44.27%), A. castellanii U07409 (20.83%) and A. polyphagaAY026243 (4.17%), but interestingly, only A. castellanii U07401 was detected in naturally infected corneal samples. In environmental samples, T4 was commonly detected in all samples including dry soil, dust, wet debris, wet soil and water. Among the T4, A. castellanii (U07409) strains were detected high occurrence in dry (45%) followed by aquatic (32.50%) and moist (22.50%) samples but however A. castellanii (U07401) strains were dominant in dry samples of soil and dust (93.10%). Subsequently, genotype T5 of A. lenticulata (U94741) strains were dominant in samples collected from aquatic environments (58.97%). In summary, A. castellanii (U07401) strains were found dominant in both environmental and corneal swab samples. Therefore, these strains are possibly the most virulent and dry soil or dusts are the most possible source of Acanthamoeba infection in cats and dogs corneas.
  13. Fulltext Major epidemiological factors associated with leptospirosis in Malaysia
    Garba B, Bahaman AR, Bejo SK, Zakaria Z, Mutalib AR, Bande F
    Acta Trop, 2018 Feb;178:242-247.
    PMID: 29217379 DOI: 10.1016/j.actatropica.2017.12.010
    INTRODUCTION: Leptospirosis is a zoonotic disease caused by a diverse pathogenic leptospira species and serovars. The disease is transmitted directly following contact with infected urine and other body fluids or indirectly after contact with water or soil contaminated with infected urine.

    OBJECTIVES: While a wide range of domestic and wild animals are known to be reservoirs of the disease, occupation, international travel and recreation are beginning to assume a center stage in the transmission of the disease. The objective of this study is to review available literatures to determine the extent to which these aforementioned risk factors aid the transmission, increase incidence and outbreak of leptospirosis in Malaysia.

    STUDY DESIGN: The review was conducted based on prevalence, incidence, and outbreak cases of leptospirosis among human and susceptible animals predisposed to several of the risk factors identified in Malaysia.

    METHODS: Literature searchers and reviews were conducted based on articles published in citation index journals, Malaysian ministry of health reports, periodicals as well as reliable newspapers articles and online media platforms. In each case, the newspapers and online media reports were supported by press briefings by officials of the ministry of health and other agencies responsible.

    RESULTS: The disease is endemic in Malaysia, and this was attributed to the large number of reservoir animals, suitable humid and moist environment for proliferation as well as abundant forest resources. Over 30 different serovars have been detected in Malaysia in different domestic and wild animal species. This, in addition to the frequency of flooding which has increased in recent years, and has helped increase the risk of human exposure. Occupation, recreation, flooding and rodent population were all identified as an important source and cause of the disease within the study population.

    CONCLUSION: There is an urgent need for the government and other stakeholders to intensify efforts to control the spread of the disease, especially as it greatly affect human health and the tourism industry which is an important component of the Malaysian economy. The risk of infection can be minimized by creating awareness on the source and mode of transmission of the disease, including the use of protective clothing and avoiding swimming in contaminated waters. Moreover, improved diagnostics can also help reduce the suffering and mortalities that follow infection after exposure to infection source.

  14. New records of 13 species of black flies (Diptera: Simuliidae) from Myanmar
    Takaoka H, Srisuka W, Maleewong W, Saeung A
    Acta Trop, 2018 Feb;178:281-289.
    PMID: 29217382 DOI: 10.1016/j.actatropica.2017.12.009
    A faunistic survey of black flies in Shan State, central Myanmar, was carried out in 2013. A total of 16 species were collected, of which 13 species are newly recorded from Myanmar. Among 13 newly recorded species, S. (S.) chiangmaiense Takaoka & Suzuki varied in the number of pupal gill filaments from eight to 10. This survey increases the number of species of black flies from Myanmar from 8 to 23. They are classified in five subgenera of the genus Simulium: one in Asiosimulium, seven in Gomphostilbia, one in Montisimulium, two in Nevermannia and 12 in Simulium.
  15. Understanding Giardia infections among rural communities using the one health approach
    Lee SC, Ngui R, Tan TK, Roslan MA, Ithoi I, Mahdy MAK, et al.
    Acta Trop, 2017 Dec;176:349-354.
    PMID: 28859958 DOI: 10.1016/j.actatropica.2017.08.030
    The epidemiology of giardiasis in rural villages in Peninsular Malaysia was examined in the context of the One Health triad that encompasses humans, animals and environment (i.e. river water). A cross-sectional study was carried out among five rural communities in Malaysia to determine the prevalence of Giardia duodenalis in humans, animals and river water. Fecal samples collected from humans and animals were examined by light microscopy. Water was sampled from the rivers adjacent to the target communities and investigated for the occurrence of Giardia cysts. The isolated cysts were further genotyped targeting the glutamate dehydrogenase and triosephosphate isomerase genes. The overall prevalence of G. duodenalis was 6.7% (18/269) and 4.7% (8/169) among humans and animals, respectively. Giardia cysts (mean concentration range: 0.10-5.97 cysts/L) were also found in adjacent rivers at four out of the five villages examined. At Kemensah and Kuala Pangsun, Giardia cysts were isolated from humans [rate: 3.7% each (of 54 each)], animals [rates: 6.3% (of 62) and 11.3% (of 16), respectively] and river water [average concentration of 9 samples each: 0.83±0.81 and 5.97±7.00, respectively]. For both villages at Pos Piah and Paya Lebar, 12.2% (of 98) and 6.1% (of 33) of collected human samples were infected, respectively whilst none of the collected animals samples in these villages were found to be positive. The river water samples of these two villages were also contaminated (average concentration: 0.20±0.35 (of 9) and 0.10±0.19 (of 3), respectively). In conclusion, Giardia cysts were simultaneously observed in the human-animal-environment (i.e., river water) interfaces in at least two of five studied communities highlighting a vital need to improve understanding on the interplay of transmission dynamics, the role of infected humans and animals in contaminating the water sources and the role of water as a vehicle of disease transmission in these communities. Indeed, this study illustrates the One Health approach which is to recognize that the optimal health of humans are interconnected with the well-being of animals and their environment.
  16. A new black fly species of the Simulium (Gomphostilbia) epistum species-group (Diptera: Simuliidae) from Thailand
    Takaoka H, Srisuka W, Low VL, Saeung A
    Acta Trop, 2017 Dec;176:373-379.
    PMID: 28919444 DOI: 10.1016/j.actatropica.2017.09.006
    A new species of black fly, Simulium (Gomphostilbia) isanense, is described based on females, males, pupae and mature larvae from Thailand. This new species is placed in the Simulium epistum species-group of the subgenus Gomphostilbia Enderlein. It is characterized by the pupal gill with eight filaments arranged as 3+3+2 from dorsal to ventral, of which an inner filament of the ventral pair is slightly longer than its counter filament. Taxonomic notes are provided to distinguish this new species from S. (G.) angulistylum Takaoka & Davies from Peninsular Malaysia, and three other related species. The difference between this new species and S. (G.) angulistylum is supported by genetic distances using the mitochondrial COI gene.
  17. 3D modelling of the pathogenic Leptospira protein LipL32: A bioinformatics approach
    Kumaran SK, Bakar MFA, Mohd-Padil H, Mat-Sharani S, Sakinah S, Poorani K, et al.
    Acta Trop, 2017 Dec;176:433-439.
    PMID: 28941729 DOI: 10.1016/j.actatropica.2017.09.011
    Leptospirosis is a widespread zoonotic disease caused by pathogenic Leptospira species (Leptospiraceae). LipL32 is an abundant lipoprotein from the outer membrane proteins (OMPs) group, highly conserved among pathogenic and intermediate Leptospira species. Several studies used LipL32 as a specific gene to identify the presence of leptospires. This research was aimed to study the characteristics of LipL32 protein gene code, to fill the knowledge gap concerning the most appropriate gene that can be used as antigen to detect the Leptospira. Here, we investigated the features of LipL32 in fourteen Leptospira pathogenic strains based on comparative analyses of their primary, secondary structures and 3D modeling using a bioinformatics approach. Furthermore, the physicochemical properties of LipL32 in different strains were studied, shedding light on the identity of signal peptides, as well as on the secondary and tertiary structure of the LipL32 protein, supported by 3D modelling assays. The results showed that the LipL32 gene was present in all the fourteen pathogenic Leptospira strains used in this study, with limited diversity in terms of sequence conservation, hydrophobic group, hydrophilic group and number of turns (random coil). Overall, these results add basic knowledge to the characteristics of LipL32 protein, contributing to the identification of potential antigen candidates in future research, in order to ensure prompt and reliable detection of pathogenic Leptospira species.
  18. The biodiversity of black flies (Diptera: Simuliidae) in Indonesia
    Hadi UK, Takaoka H
    Acta Trop, 2018 Sep;185:133-137.
    PMID: 29452114 DOI: 10.1016/j.actatropica.2018.02.013
    Indonesia is one of the megadiversity country in the world endowed with rich and unique biodiversity insects such as blackflies species (Diptera: Simuliidae). Blackflies are found almost anywhere with running water suitable as habitat for the immature stages. This family is one of the most important groups of blood-sucking insects. This study collates the records of Simulium (Diptera: Simuliidae) in previous publications related fauna of Indonesia. Based on the results of this study, there were 124 species of blackflies in Indonesian Archipelago. All species are assigned to the genus Simulium Latreille s.l., and are placed into five subgenera, i.e. Gomphostilbia Enderlein, Morops Enderlein, Nevermannia Enderlein, Simulium Latreille s.str. and Wallacellum Takaoka. Further classification into 27 species groups within the subgenera were also made. Checklists of Indonesian Simuliidae are provided including data on the distribution of each species.
  19. A new species of Simulium (Simulium) (Diptera: Simuliidae) from Genting Highlands, Malaysia
    Ya'cob Z, Takaoka H, Low VL, Sofian-Azirun M
    Acta Trop, 2018 Jun;182:1-3.
    PMID: 29453951 DOI: 10.1016/j.actatropica.2018.02.007
    Simulium (Simulium) rasuli sp. nov. is described from two females collected by a Malaise trap in Genting Highlands, Peninsular Malaysia. This new species is placed in the Simulium christophersi species-group of the subgenus Simulium. The female of this new specie is characterized by the scutum with three longitudinal vittae, dark legs, claw with a small subbasal tooth, and ovipositor valve triangular with its inner margin nearly straight. This new species is distinguished in the female from all the six named species of the species-group by the entirely brownish-black femora and tibiae.
  20. Distribution of Giardia duodenalis (Assemblages A and B) and Cryptosporidium parvum amongst migrant workers in Peninsular Malaysia
    Sahimin N, Douadi B, Yvonne Lim AL, Behnke JM, Mohd Zain SN
    Acta Trop, 2018 Jun;182:178-184.
    PMID: 29501402 DOI: 10.1016/j.actatropica.2018.02.033
    The influx of low skilled workers from socioeconomically deprived neighbouring countries to Malaysia has raised concerns about the transmission of communicable gastrointestinal diseases such as giardiasis and cryptosporidiosis to the local population. Therefore, a cross sectional study was conducted to investigate the prevalence of both diseases and the genetic diversity of these pathogens in the migrant population. Microscopic examination of faecal samples from 388 migrant workers involved in five working sectors were screened and 10.8% (n = 42) were found to be positive with Giardia spp. and 3.1% (n = 12) with Cryptosporidium spp. infections. PCR amplicons at the triosephosphate isomerase (tpi) gene were successfully obtained for Giardia duodenalis from 30 (30/388; 7.73%) samples with assemblages AII and B in 13 (13/30; 43.3%) and 17 (17/30; 56.7%) positive samples, respectively. Nine samples (9/388; 2.3%) were identified as Cryptosporidium parvum using PCR-RFLP analysis. Country of origin, duration of residence in Malaysia and working sectors significantly influenced G. duodenalis assemblage AII infections amongst the targeted population. Meanwhile, C. parvum infection was significantly associated with those working in the food service sector. Despite the low presence of pathogenic G. duodenalis and C. parvum in the study population, the results highlight the risk of anthroponotic foodborne and waterborne transmission and therefore call for implementation of control strategies through improvements in personal hygiene and sanitation standards.
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