Displaying publications 21 - 40 of 163 in total

Abstract:
Sort:
  1. A point-of-care cassette test for detection of Strongyloides stercoralis
    Noordin R, Osman E, Kalantari N, Anuar NS, Gorgani-Firouzjaee T, Sithithaworn P, et al.
    Acta Trop, 2022 Feb;226:106251.
    PMID: 34808116 DOI: 10.1016/j.actatropica.2021.106251
    Strongyloides stercoralis is a parasite that causes strongyloidiasis worldwide. It may lead to a life-long infection in immunocompetent people and hyperinfection in immunosuppressed patients. A point-of-care (POC) rapid test is helpful for patient diagnosis in resource-limited settings and as a detection tool in elimination/control programs. Previously, we reported a rapid IgG4 dipstick test (Ss Rapid®) for Strongyloides suitable for a laboratory setting. A POC cassette format of the test, which is field-applicable, has since been developed. Here, we report on a laboratory-based evaluation of the Ss Rapid® cas sette test on 285 sera. We assessed the diagnostic sensitivity of the Ss Rapid® cas sette with 32 sera, comprising samples from larval and/or DNA positive individuals from three countries. Additionally, we also tested samples from 33 seropositive endemic areas residents. We evaluated the diagnostic specificity of the test using 220 samples, comprising sera from other infections (n = 101), allergy cases with high IgE antibodies (n = 4), and blood donors (n = 115). The test showed high diagnostic sensitivity (97%, 31/32), and all sera of the seropositive endemic residents were reactive. It also showed high diagnostic specificity (94.5%, 208/220), and all false-positive samples tested negative after sera adsorption using recombinant NIE-coated microsphere beads. Additionally, we showed that the test worked with spiked whole blood samples. The study results showed that the SsRapid® cas sette test merits further laboratory and field evaluations.
  2. Coexistence and intraguild competition of Chrysomya albiceps and Lucilia sericata larvae: case reports and experimental studies applied to forensic entomology
    Ivorra T, Martínez-Sánchez A, Rojo S
    Acta Trop, 2022 Feb;226:106233.
    PMID: 34808117 DOI: 10.1016/j.actatropica.2021.106233
    The larval development of Chrysomya albiceps and Lucilia sericata is a well-known and valuable tool for estimating the postmortem interval (PMI). The third instar larvae of Ch. albiceps are facultative predators of the larvae of other necrophagous dipterans, and this behaviour is undoubtedly an important factor to consider. Both species are found together during human autopsies in Spain and other parts of Europe, where they cohabit, so a precise knowledge of their larval coexistence data is essential. The aim of this study is to investigate their coexistence and the intraguild predation of Ch. albiceps on L. sericata under experimental conditions and in real case reports. To analyse intra- and interspecific competition, four densities were used under controlled abiotic conditions [25ºC, 60-70% RH and 12:12 (D:N)]. The experimental data were compared with data corresponding to their coexistence in natural conditions, so annual activity and forensic case reports for both species were studied. The results indicate that the mortality of immature specimens in both species, the preimaginal developmental time, and adult size were affected by competition. In natural conditions, adult coexistence during the spring-summer period was confirmed. The simultaneity of the two species colonising human corpses is frequent in the studied area, with Ch. albiceps being the dominant species, and L. sericata the relevant species for estimating the minimum postmortem interval.
  3. Phytochemical, anti-Acanthamoeba, and anti-adhesion properties of Garcinia mangostana flower as preventive contact lens solution
    Sangkanu S, Mitsuwan W, Mahboob T, Mahabusarakam W, Chewchanwuttiwong S, Siphakdi P, et al.
    Acta Trop, 2022 Feb;226:106266.
    PMID: 34890540 DOI: 10.1016/j.actatropica.2021.106266
    Acanthamoeba keratitis infection extends due to the growing number of contact lens users. Indigenous plants including Garcinia mangostana play a vital role in human health and well being. Many species of this plant have been reported with myriads of potent medicinal properties. However, the aims of this study were, for the first time, to isolate compounds from the flower of G. mangostana and to test their anti-Acanthamoeba and anti-adhesion activity against Acanthamoeba triangularis. Powdered flowers of G. mangostana were extracted and chromatographed on a silica gel column. The structures of the compounds were established with the aid of 1H NMR. More so, the anti-Acanthamoeba and anti-adhesion properties were tested on a 96-well polystyrene microtiter plate and soft contact lenses. Scanning electron microscope (SEM) was used to determine the features of A. triangularis on contact lenses. Eight pure compounds were obtained, namely 9-hydroxycalabaxanthone, tovophillin A, garcinone E, garcinone B, α-mangostin, gartinin, 8-deoxygartinin and γ-mangostin. The extract and pure compounds exhibited anti-Acanthamoeba activity with MIC values in the range of 0.25-1 mg/mL. In addition, the extract and α-mangostin displayed significant activity against the adhesion of A. triangularis trophozoites both in polystyrene plate and in contact lenses at 0.5 × MIC (0.25 mg/mL). Furthermore, α-mangostin has the potential to remove A. triangularis adhesion in contact lenses similar to a commercial multipurpose solution (MPS). SEM study confirmed that crude extract and α-mangostin are effective as solutions for contact lenses, which removed A. triangularis trophozoites within 24 h. Alpha-mangostin was non-toxic to Vero cells at a concentration below 39 μM in 24 h. Crude extract of G. mangostana flower and its α-mangostin serve as candidate compounds in the treatment of Acanthamoeba infection or as lens care solution, since they can be used as a source of natural products against Acanthamoeba and virulence factor associated with the adhesion of A. triangularis.
  4. 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.

  5. 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.
  6. 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.
  7. 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.
  8. 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.
  9. 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.
  10. 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.
  11. 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%.
  12. Soft ticks (Acari: Argasidae) in the island nations of Southeast Asia: A review on their distribution, associated hosts and potential pathogens
    Kazim AR, Houssaini J, Ehlers J, Tappe D, Heo CC
    Acta Trop, 2021 Nov;223:106085.
    PMID: 34389326 DOI: 10.1016/j.actatropica.2021.106085
    Soft ticks (Acari: Argasidae) are the second major family of the blood feeding metastriates and vectors of a number of viral and bacterial pathogens for both humans and animals. Despite the growing effort on tick surveillance and studies worldwide, there is still limited information on the soft tick distribution in the island nations of Southeast Asia, especially species that are medically and veterinarily important. With the aim to provide an overview of the current status of knowledge on soft tick distribution in the island nations of Southeast Asia (Malaysia, Singapore, Brunei, Indonesia, the Philippines and Timor-Leste), this article reviews the species of soft ticks (Acari: Argasidae) and their associated hosts and pathogens, with the addition of a pictorial summary and list of tick species discovered in this region. The most prevalent soft tick genus is Carios, and the host species most associated with findings of soft ticks in this region are bats, particularly of the Pteropodidae and Vespertilionidae families. Furthermore, the only known pathogen originating from soft ticks in the island nations of Southeast Asia was the Keterah virus, which was isolated from Argas pusillus tick in Malaysia.
  13. Two new black fly species of the Simulium (Gomphostilbia) asakoae species-group (Diptera: Simuliidae) from Taiwan
    Takaoka H, Low VL, Huang YT, Fukuda M, Ya'cob Z
    Acta Trop, 2021 Oct;222:106023.
    PMID: 34161814 DOI: 10.1016/j.actatropica.2021.106023
    Two new black fly species, Simulium (Gomphostilbia) kaohsiungense and S. (G.) shoufengense, are described from females, males and pupae in Taiwan. These new species are placed in the S. asakoae species-group. Simulium (G.) kaohsiungense sp. nov. is characterized by a combination of the elongate female sensory vesicle, male upper-eye (large) facets in 15 vertical columns and 15 or 16 horizontal rows, male hind basitarsus 1.02-1.15 times the width of the hind femur, and widened pupal terminal hooks. These characteristics distinguish this new species from most species of the S. asakoae species-group. Simulium (G.) shoufengense sp. nov. is similar in the female and male to S. (G.) asakoae Takaoka & Davies originally described from Peninsular Malaysia but is distinguished from the latter species in the pupa by the combined length of the primary and secondary stalks of the dorsal triplet of gill filaments as long as or longer than the common basal stalk of the gill, and dorsum of abdominal segments 1 and 2 not darkened. The species previously regarded in Taiwan as S. (G.) metatarsale Brunetti, originally described from India, is morphologically and molecularly identified as S. (G.) asakoae.
  14. A new antigen detection ELISA for the diagnosis of Strongyloides infection
    Balachandra D, Rahumatullah A, Lim TS, Mustafa FH, Ahmad H, Anuar NS, et al.
    Acta Trop, 2021 Sep;221:105986.
    PMID: 34058161 DOI: 10.1016/j.actatropica.2021.105986
    Serodiagnosis is an essential component of the laboratory diagnosis of Strongyloides infection and is usually performed using an indirect IgG antibody test. A direct antigen detection method can complement the IgG assay, particularly for detecting early infection and post-treatment follow-up. In the present study, a recombinant scFv monoclonal antibody against NIE recombinant protein (rMAb23) that we had previously produced was used to develop a Strongyloides antigen detection ELISA (SsAg-ELISA). The assay is based on detecting immune complexes of circulating NIE antigens bound to Strongyloides-specific IgG antibodies. The optimized ELISA parameters were 10 µg/mL of rMAb23 coated on microtitre plate wells, 2% skim milk as blocking reagent, 1:100 serum dilution, and 1:1000 goat anti-human IgG F(ab')2 conjugated to horseradish peroxidase. Four groups of serum samples were used, i.e., Strongyloides-positive serum samples categorized into Groups IA and IB; the former were from probable chronic infections and the latter from probable early/acute infections. Strongyloides-negative samples comprising Groups II (healthy samples) and III (other infections); the latter were from eleven different types of other parasitic infections. The receiver operating characteristic (ROC) curve showed an area under the curve (AUC) of 1.00, cut-off optical density (OD405) of 0.5002, and 100% diagnostic sensitivity and specificity. The results of the commercial IgG-ELISA and SsAg-ELISA from Group IA were found to be moderately correlated (r = 0.416; p 
  15. Molecular detection of Trypanosoma evansi in dogs from India and Southeast Asia
    Nguyen VL, Iatta R, Manoj RRS, Colella V, Bezerra-Santos MA, Mendoza-Roldan JA, et al.
    Acta Trop, 2021 Aug;220:105935.
    PMID: 33930300 DOI: 10.1016/j.actatropica.2021.105935
    Trypanosoma evansi, the causative agent of surra, is a hemoflagellate protozoan mechanically transmitted by hematophagous flies, mainly in tropical and subtropical regions. This protozoan affects several mammalian hosts, including dogs, which are highly susceptible to the infection. To investigate the occurrence of T. evansi in dogs, a total of 672 DNA samples from India (n = 228), Indonesia (n = 57), Malaysia (n = 45), the Philippines (n = 103), Thailand (n = 120), and Vietnam (n = 119) were screened by using species-specific conventional PCR. Of the tested dogs, 10 (1.5%) scored positive to T. evansi. In particular, positive samples were detected in canine blood samples collected from India (n = 4; 1.8%), Indonesia (n = 4; 7%), and Malaysia (n = 2; 4.4%). All tested samples from the Philippines, Thailand and Vietnam were negative. Nucleotide sequence analysis revealed a high variation (i.e. from 0.4% to 6.2%) among the RoTat 1.2 variant surface glycoprotein (vsg) gene. Although the number of sequences included in this analysis is relatively small, this nucleotide variation may indicate the divergence of T. evansi RoTat 1.2 vsg gene among different strains. The high incidence of T. evansi previously reported in cattle and buffaloes in India and Southeast Asia suggests that these animals are the main source of infection to dogs.
  16. Culturable bacteria in adults of a Southeast Asian black fly, Simulium tani (Diptera:Simuliidae)
    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.
  17. Current tools for the diagnosis and detection of spotted fever group Rickettsia
    Husin NA, AbuBakar S, Khoo JJ
    Acta Trop, 2021 Jun;218:105887.
    PMID: 33713627 DOI: 10.1016/j.actatropica.2021.105887
    Spotted fever group (SFG) rickettsiae causes a number of diseases in humans worldwide, which can range from mild to highly lethal. Since the clinical presentations of rickettsioses caused by SFG rickettsiae are variable and may be similar to the diseases caused by other rickettsiae, such as Orientia tsutsugamushi (agent for scrub typhus), Coxiella burnetii (agent for Q fever) and the typhus group rickettsiae (agents for epidemic and murine typhus), the accurate diagnosis of infections caused by SFG Rickettsia remains challenging especially in resource-poor settings in developing countries. This review summarizes the various diagnostic and detection tools that are currently available for the confirmation of infections by SFG rickettsiae. The advantages and challenges pertaining to the different serological and molecular detections methods, as well as new assays in development, are discussed. The utility of the detection tools contributing to the surveillance of SFG rickettsiae in arthropods and animals are reviewed.
  18. A new species of Simulium (Gomphostilbia) (Diptera: Simuliidae) from Northern Thailand, with its genetic relationship in the S. asakoae species-group
    Srisuka W, Aupalee K, Low VL, Yácob Z, Fukuda M, Saeung A, et al.
    Acta Trop, 2021 Jun;218:105889.
    PMID: 33722581 DOI: 10.1016/j.actatropica.2021.105889
    A new black fly species, Simulium (Gomphostilbia) kiewlomense, is described from females, males, pupae and mature larvae in Thailand. This new species is placed in the S. asakoae species-group and is characterized by having a combination of the elongate female sensory vesicle, widened male hind basitarsus, which is much wider than the hind femur, small pupal terminal hooks, and light greenish larval abdominal segments 1-3. Taxonomic notes are given to separate this new species from other related species. A DNA analysis using the COI gene shows that this new species has two genoforms with 1.21% difference. This is the 28th species of the S. asakoae species-group in Thailand, strengthening the evidence for high species diversity of this species-group.
  19. Simulium (Gomphostilbia) aziruni: First record of a black fly (Diptera: Simuliidae) attracted to a human in Malaysia
    Izwan-Anas N, Ya'cob Z, Low VL, Lourdes EY, Ramli R, Bolongan G, et al.
    Acta Trop, 2021 Jun;218:105904.
    PMID: 33775626 DOI: 10.1016/j.actatropica.2021.105904
    Most female black flies in the genus Simulium are blood-sucking flies and they can cause various parasitic diseases in human and animal. A total of 94 species of black flies have been reported in Malaysia, however, their biting behavior and role as vector of infectious agents remain understudied. To fill in this knowledge gap, we attempted to survey adult black flies from field populations in Peninsular Malaysia. In a survey carried out in 2017 at Tasik Kenyir, Terengganu, three females were caught while attracted and landed on human skin. Further morphological and molecular analyses showed that the specimens were identical to Simulium (Gomphostilbia) aziruni Takaoka, Hashim & Chen of the Simulium gombakense species-group. This is the first report on a black fly species attracted to human in Malaysia which serves as a steppingstone towards in-depth studies for black flies in this region.
  20. A new species of the Simulium (Gomphostilbia) ceylonicum species-group (Diptera: Simuliidae) from Thailand
    Takaoka H, Srisuka W, Ya'cob Z, Low VL, Saeung A
    Acta Trop, 2021 May;217:105865.
    PMID: 33607063 DOI: 10.1016/j.actatropica.2021.105865
    A new black fly species, Simulium (Gomphostilbia) pangsidaense, is described on the basis of adult female, male, pupal exuviae and mature larvae from Pang Sida National Park, Sa Kaew Province, Eastern Thailand. This new species is placed in the Simulium ceylonicum species-group. It is distinguished from three Thai members of the S. ceylonicum species-group by the following characteristics: from S. (G.) curtatum Jitklang et al. and S. (G.) sheilae Takaoka & Davies by the wide pupal terminal hooks (triangular terminal hooks in the latter two species), and from S. (G.) sheilae and S. (G.) trangense Jitklang et al. by the number of male upper-eye facets in 13 vertical columns and 14 or 15 horizontal rows (10 or 11 vertical columns and 12 or 13 horizontal rows in the latter two species). This is the fourth member of the S. ceylonicum species-group recorded from Thailand.
Related Terms
Filters
Contact Us

Please provide feedback to Administrator (afdal@afpm.org.my)

External Links