Browsing by Author "Ronald E.Morales Vargas"

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    Courtship activity, copulation & insemination success in a mosquito vector fed a herbal aphrodisiac: Implications for sterile insect technology
    (2018-09-01) Hamady Dieng; Tomomitsu Satho; Fatimah Abang; Fumio Miake; Fatin A.B. Azman; Nurshilawati A. Latip; Nur Ezzati Aliasan; Sabina Noor; Cirilo Nolasco-Hipolito; Abu Hassan Ahmad; Idris A. Ghani; Hamdan Ahmad; Wan Fatma Zuharah; Abdul Hafiz A. Majid; Ronald E.Morales Vargas; Noppawan P. Morales; Siriluck Attrapadung; Gabriel Tonga Noweg; Fukuoka University; Universiti Malaysia Sarawak; Mahidol University; Universiti Kebangsaan Malaysia; Universiti Sains Malaysia
    © 2018 Indian Journal of Medical Research. Background & objectives: In sterile insect technology (SIT), mating competitiveness is a pre-condition for the reduction of target pest populations and a crucial parameter for judging efficacy. Still, current SIT trials are being hindered by decreased effectiveness due to reduced sexual performance of released males. Here, we explored the possible role of a herbal aphrodisiac in boosting the mating activity of Aedes aegypti.Methods: Males were fed one of two diets in this study: experimental extract of Eurycoma longifolia (MSAs) and sugar only (MSOs). Differences in life span, courtship latency, copulation activity and mating success were examined between the two groups.Results: No deaths occurred among MSA and MSO males. Life span of MSOs was similar to that of MSAs. The courtship latency of MSAs was shorter than that of MSOs (P<0.01). MSAs had greater copulation success than MSOs (P<0.001). In all female treatments, MSAs mated more than MSOs, but the differences in rate were significant only in the highest female density (P<0.05). In MSAs, mating success varied significantly with female density (P<0.01), with the 20-female group (P<0.01) having the lowest rate. Single MSA had better mating success at the two lowest female densities. In MSOs, there were no significant differences in mating success rate between the different female densities. Interpretation & conclusions: Our results suggested that the herbal aphrodisiac, E. longifolia, stimulated the sexual activity of Ae. aegypti and may be useful for improving the mating competitiveness of sterile males, thus improving SIT programmes.
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    Detection and characterization of enteric viruses in flood water from the 2011 Thai flood
    (2013-09-25) Nathamon Ngaosuwankul; Narin Thippornchai; Akifumi Yamashita; Ronald E.Morales Vargas; Witawat Tunyong; Yuvadee Mahakunkijchareon; Kazuyoshi Ikuta; Pratap Singhasivanon; Tamaki Okabayashi; Pornsawan Leaungwutiwong; Mahidol University; Genome Information Research Center; Osaka University
    Severe flooding, which is associated with numerous outbreaks of a wide range of infectious diseases, particularly those caused by enteric viruses, occurred in all areas of Thailand in 2011. To determine the prevalence of five human enteric viruses, namely enterovirus, rotavirus (RV), norovirus (NV), hepatitis A virus (HAV), and hepatitis E virus, in the flood water, 100 water samples were collected from flood-damaged areas in central Thailand. Viral RNA was extracted from concentrated samples and analyzed by RT-PCR and sequencing. NV was the most commonly detected pathogen in the tested samples (14%). RV and HAV were detected in 9% and 7% of samples, respectively. This study is the first to detect enteric viral genes in flood water in Thailand. Furthermore, it is the first to detect an NV gene in any type of environmental water in Thailand. These results provide useful information for estimating the risk of flood waterborne viral infection.
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    Differential susceptibility and innate immune response of aedes aegypti and aedes albopictus to the haitian strain of the mayaro virus
    (2019-10-09) Fodé Diop; Haoues Alout; Cheikh Tidiane Diagne; Michèle Bengue; Cécile Baronti; Rodolphe Hamel; Loïc Talignani; Florian Liegeois; Julien Pompon; Ronald E.Morales Vargas; Antoine Nougairède; Dorothée Missé; Animal, Santé, Territoires, Risques et Ecosystèmes (ASTRE); Maladies Infectieuses et Vecteurs : Écologie, Génétique, Évolution et Contrôle; Aix Marseille Université; Mahidol University
    © 2019 by the authors. Licensee MDPI, Basel, Switzerland. Mayaro (MAYV) is an emerging arthropod-borne virus belonging to the Alphavirus genus of the Togaviridae family. Although forest-dwelling Haemagogus mosquitoes have been considered as its main vector, the virus has also been detected in circulating Aedes ssp mosquitoes. Here we assess the susceptibility of Aedes aegypti and Aedes albopictus to infection with MAYV and their innate immune response at an early stage of infection. Aedes albopictus was more susceptible to infection with MAYV than Ae. aegypti. Analysis of transcript levels of twenty immunity-related genes by real-time PCR in the midgut of both mosquitoes infected with MAYV revealed increased expression of several immune genes, including CLIP-domain serine proteases, the anti-microbial peptides defensin A, E, cecropin E, and the virus inducible gene. The regulation of certain genes appeared to be Aedes species-dependent. Infection of Ae. aegypti with MAYV resulted in increased levels of myeloid differentiation2-related lipid recognition protein (ML26A) transcripts, as compared to Ae. albopictus. Increased expression levels of thio-ester-containing protein 22 (TEP22) and Niemann-Pick type C1 (NPC1) gene transcripts were observed in infected Ae. albopictus, but not Ae. aegypti. The differences in these gene expression levels during MAYV infection could explain the variation in susceptibility observed in both mosquito species.
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    Presence of a predator image in potential breeding sites and oviposition responses of a dengue vector
    (2017-12-01) Hamady Dieng; Tomomitsu Satho; Nur Farrahana Binti Suradi; Hafijah Hakim; Fatimah Abang; Nur Ezzati Aliasan; Fumio Miake; Wan Fatma Zuharah; Nur Faeza A. Kassim; Abdul Hafiz A. Majid; Nik Fadzly; Ronald E.Morales Vargas; Noppawan P. Morales; Gabriel Tonga Noweg; Universiti Malaysia Sarawak; Fukuoka University; Universiti Sains Malaysia; Mahidol University
    © 2017 Elsevier B.V. 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.