Publications by authors named "Alongkot Ponlawat"

33 Publications

Sand fly identification and screening for Leishmania spp. in six provinces of Thailand.

Parasit Vectors 2021 Jul 3;14(1):352. Epub 2021 Jul 3.

Vector Biology and Control Section, Department of Entomology, Armed Forces Research Institute of Medical Sciences (AFRIMS), Bangkok, 10400, Thailand.

Background: Phlebotomine sand flies are vectors of Leishmania spp. At least 27 species of sand flies have been recorded in Thailand. Although human leishmaniasis cases in Thailand are mainly imported, autochthonous leishmaniasis has been increasingly reported in several regions of the country since 1999. Few studies have detected Leishmania infection in wild-caught sand flies, although these studies were carried out only in those areas reporting human leishmaniasis cases. The aim of this study was therefore to identity sand fly species and to investigate Leishmania infection across six provinces of Thailand.

Methods: Species of wild-caught sand flies were initially identified based on morphological characters. However, problems identifying cryptic species complexes necessitated molecular identification using DNA barcoding in parallel with identification based on morphological characters. The wild-caught sand flies were pooled and the DNA isolated prior to the detection of Leishmania infection by a TaqMan real-time PCR assay.

Results: A total of 4498 sand flies (1158 males and 3340 females) were caught by trapping in six provinces in four regions of Thailand. The sand flies were morphologically classified into eight species belonging to three genera (Sergentomyia, Phlebotomus and Idiophlebotomus). Sergentomyia iyengari was found at all collection sites and was the dominant species at most of these, followed in frequency by Sergentomyia barraudi and Phlebotomus stantoni, respectively. DNA barcodes generated from 68 sand flies allowed sorting into 14 distinct species with 25 operational taxonomic units, indicating a higher diversity (by 75%) than that based on morphological identification. Twelve barcoding sequences could not be assigned to any species for which cytochrome c oxidase subunit I sequences are available. All tested sand flies were negative for Leishmania DNA.

Conclusions: Our results confirm the presence of several sand fly species in different provinces of Thailand, highlighting the importance of using DNA barcoding as a tool to study sand fly species diversity. While all female sand flies tested in this study were negative for Leishmania, the circulation of Leishmania spp. in the investigated areas cannot be ruled out.
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http://dx.doi.org/10.1186/s13071-021-04856-6DOI Listing
http://www.ncbi.nlm.nih.gov/pmc/articles/PMC8254935PMC
July 2021

Field evaluation of four commercial light traps, trap placement, and effect of carbon dioxide on phlebotomine sand fly collection in northern Thailand.

Acta Trop 2021 Aug 9;220:105953. Epub 2021 May 9.

Department of Chemistry and Life Science, United States, Military Academy West Point, West Point, NY, 10996, USA. Electronic address:

Several light trap devices have been invented and developed to assess the abundance of sand flies. Traps available in the market have different designs and attractant combinations to catch sand fly vectors. We evaluated the efficacy of four commercial light traps and determined the effect of trap placement and carbon dioxide (CO) on sand fly collection in northern Thailand. Trap evaluations were conducted at two natural caves located in Chiang Rai province, Thailand. In the first part of the study, the efficacies of four trap types including the Centers for Disease Control miniature light trap (CDC LT), Encephalitis Vector Survey trap (EVS), CDC Updraft Blacklight trap (CDC UB), and Laika trap (LK) were evaluated and compared using a Latin square experimental design. The second half of the study evaluated the influence of trap placement and CO on sand fly collection. Additionally, CDC LT were placed inside, outside, and at the entrance of caves to compare the number of sand flies collected. For the trap efficacy experiment, a total of 11,876 phlebotomine sand flies were collected over 32 trap-nights. Results demonstrated that CDC LT, CDC UB, and LK collected significantly more sand flies than EVS (P > 0.05). However, there were no significant differences between the numbers of sand flies collected by CDC LT, CDC UB, and LK. A total of 6,698 sand flies were collected from the trap placement and CO experiment over 72 trap-nights. Results showed that CO did not influence the numbers of sand flies captured (P < 0.05), whereas trap placement at the entrance of the caves resulted in collection of significantly more sand flies than traps placed inside and outside of the caves. We found the CDC LT, CDC UB, and LK without CO captured the greatest amount of sand flies. This was particularly observed when traps were placed at the entrance of a cave, perhaps because of the greater passage of stimuli caused by wind flow at the entrance of the cave. The light traps in this study can be used effectively to collect sand fly vectors in northern Thailand.
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http://dx.doi.org/10.1016/j.actatropica.2021.105953DOI Listing
August 2021

Enhanced Zika virus susceptibility of globally invasive populations.

Science 2020 11;370(6519):991-996

Viral Diseases Branch, Walter Reed Army Institute of Research, Silver Spring, MD, USA.

The drivers and patterns of zoonotic virus emergence in the human population are poorly understood. The mosquito is a major arbovirus vector native to Africa that invaded most of the world's tropical belt over the past four centuries, after the evolution of a "domestic" form that specialized in biting humans and breeding in water storage containers. Here, we show that human specialization and subsequent spread of out of Africa were accompanied by an increase in its intrinsic ability to acquire and transmit the emerging human pathogen Zika virus. Thus, the recent evolution and global expansion of promoted arbovirus emergence not solely through increased vector-host contact but also as a result of enhanced vector susceptibility.
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http://dx.doi.org/10.1126/science.abd3663DOI Listing
November 2020

Entomological Surveillance for Zika and Dengue Virus in Mosquitoes: Implications for Vector Control in Thailand.

Pathogens 2020 Jun 4;9(6). Epub 2020 Jun 4.

Department of Entomology, Armed Forces Research Institute of Medical Sciences (AFRIMS), Bangkok 10400, Thailand.

Entomological surveillance for arthropod-borne viruses is vital for monitoring vector-borne diseases and informing vector control programs. In this study, we conducted entomological surveillance in Zika virus endemic areas. In Thailand, it is standard protocol to perform mosquito control within 24 h of a reported dengue case. females were collected within 72 h of case reports from villages with recent Zika-human cases in Kamphaeng Phet Province, Thailand in 2017 and 2018. Mosquitoes were bisected into head-thorax and abdomen and then screened for Zika (ZIKV) and dengue (DENV) viruses using real-time RT-PCR. ZIKV RNA was detected in three samples from two female (1.4%). A partial envelope sequence analysis revealed that the ZIKV sequences were the Asian lineage identical to sequences from ZIKV-infected cases reported in Thailand during 2016 and 2017. Dengue virus-1 (DENV-1) and dengue virus-4 (DENV-4) were found in four females (2.8%), and partial capsid sequences were nearly identical with DENV-1 and DENV-4 from Thai human cases reported in 2017. Findings in the current study demonstrate the importance of entomological surveillance programs to public health mosquito-borne disease prevention measures and control.
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http://dx.doi.org/10.3390/pathogens9060442DOI Listing
http://www.ncbi.nlm.nih.gov/pmc/articles/PMC7350330PMC
June 2020

Virological and Immunological Outcomes in Rhesus Monkeys after Exposure to Dengue Virus-Infected Mosquitoes.

Am J Trop Med Hyg 2020 07 14;103(1):112-119. Epub 2020 May 14.

Institute for Vector-Borne Diseases, Monash University, Melbourne, Australia.

This study describes the natural history of dengue virus (DENV) infection in rhesus monkeys exposed to the bites of DENV-infected mosquitoes. Dengue virus-infected mosquitoes were generated by either intrathoracic inoculation or by oral feeding on viremic blood meals. Each of the six rhesus monkeys that were fed upon by intrathoracically infected mosquitoes developed non-structural protein 1 (NS1) antigenemia and an IgM response; viremia was detected in 4/6 individuals. No virological or immunological evidence of DENV infection was detected in the three monkeys exposed to mosquitoes that had been orally infected with DENV. These results demonstrate the utility of mosquito-borne challenge of rhesus monkeys with DENV.
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http://dx.doi.org/10.4269/ajtmh.19-0633DOI Listing
http://www.ncbi.nlm.nih.gov/pmc/articles/PMC7356439PMC
July 2020

Evidence for both sequential mutations and recombination in the evolution of kdr alleles in Aedes aegypti.

PLoS Negl Trop Dis 2020 04 17;14(4):e0008154. Epub 2020 Apr 17.

Department of Entomology, Comstock Hall, Cornell University, Ithaca, New York, United States of America.

Background: Aedes aegypti is a globally distributed vector of human diseases including dengue, yellow fever, chikungunya, and Zika. Pyrethroid insecticides are the primary means of controlling adult A. aegypti populations to suppress arbovirus outbreaks, but resistance to pyrethroid insecticides has become a global problem. Mutations in the voltage-sensitive sodium channel (Vssc) gene are a major mechanism of pyrethroid resistance in A. aegypti. Vssc resistance alleles in A. aegypti commonly have more than one mutation. However, our understanding of the evolutionary dynamics of how alleles with multiple mutations arose is poorly understood.

Methodology/principal Findings: We examined the geographic distribution and association between the common Vssc mutations (V410L, S989P, V1016G/I and F1534C) in A. aegypti by analyzing the relevant Vssc fragments in 25 collections, mainly from Asia and the Americas. Our results showed all 11 Asian populations had two types of resistance alleles: 1534C and 989P+1016G. The 1534C allele was more common with frequencies ranging from 0.31 to 0.88, while the 989P+1016G frequency ranged from 0.13 to 0.50. Four distinct alleles (410L, 1534C, 410L+1534C and 410L+1016I+1534C) were detected in populations from the Americas. The most common was 410L+1016I+1534C with frequencies ranging from 0.50 to 1.00, followed by 1534C with frequencies ranging from 0.13 to 0.50. Our phylogenetic analysis of Vssc supported multiple independent origins of the F1534C mutation. Our results indicated the 410L+1534C allele may have arisen by addition of the V410L mutation to the 1534C allele, or by a crossover event. The 410L+1016I+1534C allele was the result of one or two mutational steps from a 1534C background.

Conclusions/significance: Our data corroborated previous geographic distributions of resistance mutations and provided evidence for both recombination and sequential accumulation of mutations contributing to the molecular evolution of resistance alleles in A. aegypti.
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http://dx.doi.org/10.1371/journal.pntd.0008154DOI Listing
http://www.ncbi.nlm.nih.gov/pmc/articles/PMC7164583PMC
April 2020

An Innovative, Prospective, Hybrid Cohort-Cluster Study Design to Characterize Dengue Virus Transmission in Multigenerational Households in Kamphaeng Phet, Thailand.

Am J Epidemiol 2020 07;189(7):648-659

Difficulties inherent in the identification of immune correlates of protection or severe disease have challenged the development and evaluation of dengue vaccines. There persist substantial gaps in knowledge about the complex effects of age and sequential dengue virus (DENV) exposures on these correlations. To address these gaps, we were conducting a novel family-based cohort-cluster study for DENV transmission in Kamphaeng Phet, Thailand. The study began in 2015 and is funded until at least 2023. As of May 2019, 2,870 individuals in 485 families were actively enrolled. The families comprise at least 1 child born into the study as a newborn, 1 other child, a parent, and a grandparent. The median age of enrolled participants is 21 years (range 0-93 years). Active surveillance is performed to detect acute dengue illnesses, and annual blood testing identifies subclinical seroconversions. Extended follow-up of this cohort will detect sequential infections and correlate antibody kinetics and sequence of infections with disease outcomes. The central goal of this prospective study is to characterize how different DENV exposure histories within multigenerational family units, from DENV-naive infants to grandparents with multiple prior DENV exposures, affect transmission, disease, and protection at the level of the individual, household, and community.
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http://dx.doi.org/10.1093/aje/kwaa008DOI Listing
http://www.ncbi.nlm.nih.gov/pmc/articles/PMC7393304PMC
July 2020

Too "sexy" for the field? Paired measures of laboratory and semi-field performance highlight variability in the apparent mating fitness of Aedes aegypti transgenic strains.

Parasit Vectors 2019 Jul 19;12(1):357. Epub 2019 Jul 19.

Department of Life Sciences, Imperial College London, Silwood Park, Ascot, UK.

Background: Evaluating and improving mating success and competitive ability of laboratory-reared transgenic mosquito strains will enhance the effectiveness of proposed disease-control strategies that involve deployment of transgenic strains. Two components of the mosquito rearing process, larval diet quantity and aquatic environment - which are linked to physiological and behavioural differences in adults - are both relatively easy to manipulate. In mosquitoes, as for many other arthropod species, the quality of the juvenile habitat is strongly associated with adult fitness characteristics, such as longevity and fecundity. However, the influence of larval conditioning on mating performance is poorly understood. Here, we investigated the combined effects of larval diet amount and environmental water source on adult male mating success in a genetically modified strain of Aedes aegypti mosquitoes in competition with wild-type conspecifics. Importantly, this research was conducted in a field setting using low generation laboratory and wild-type lines.

Results: By controlling larval diet (high and low) and rearing water source (field-collected and laboratory water), we generated four treatment lines of a genetically modified strain of Ae. aegypti tagged with fluorescent sperm. Laboratory reared mosquitoes were then competed against a low generation wild-type colony in a series of laboratory and semi-field mating experiments. While neither food quantity nor larval aquatic environment were found to affect male mating fitness, the transgenic lines consistently outperformed wild-types in laboratory competition assays, an advantage that was not conferred to semi-field tests.

Conclusions: Using a model transgenic system, our results indicate that differences in the experimental conditions of laboratory- and field-based measures of mating success can lead to variation in the perceived performance ability of modified strains if they are only tested in certain environments. While there are many potential sources of variation between laboratory and field lines, laboratory adaptation - which may occur over relatively few generations in this species - may directly impact mating ability depending on the context in which it is measured. We suggest that colony-hybridization with field material can potentially be used to mitigate these effects in a field setting. Release programs utilising mass-produced modified laboratory strains should incorporate comparative assessments of quality in candidate lines.
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http://dx.doi.org/10.1186/s13071-019-3617-2DOI Listing
http://www.ncbi.nlm.nih.gov/pmc/articles/PMC6642483PMC
July 2019

Male competition and the evolution of mating and life-history traits in experimental populations of Aedes aegypti.

Proc Biol Sci 2019 06 12;286(1904):20190591. Epub 2019 Jun 12.

1 Department of Life Sciences, Imperial College London , Silwood Park, Ascot SL5 7PY , UK.

Aedes aegypti is an important disease vector and a major target of reproductive control efforts. We manipulated the opportunity for sexual selection in populations of Ae. aegypti by controlling the number of males competing for a single female. Populations exposed to higher levels of male competition rapidly evolved higher male competitive mating success relative to populations evolved in the absence of competition, with an evolutionary response visible after only five generations. We also detected correlated evolution in other important mating and life-history traits, such as acoustic signalling, fecundity and body size. Our results indicate that there is ample segregating variation for determinants of male mating competitiveness in wild populations and that increased male mating success trades-off with other important life-history traits. The mating conditions imposed on laboratory-reared mosquitoes are likely a significant determinant of male mating success in populations destined for release.
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http://dx.doi.org/10.1098/rspb.2019.0591DOI Listing
http://www.ncbi.nlm.nih.gov/pmc/articles/PMC6571471PMC
June 2019

A Comparative Study of Mosquito and Sand Fly (Diptera: Psychodidae: Phlebotominae) Sampling Using Dry Ice and Chemically Generated Carbon Dioxide From Three Different Prototype CO2 Generators.

J Econ Entomol 2019 02;112(1):494-498

European Biological Control Laboratory (EBCL), USDA-ARS, Thessaloniki, Greece.

A comparative study was conducted to test the efficiency of Centers for Disease Control and Prevention (CDC) light traps baited with either dry ice or carbon dioxide (CO2) produced from one of three different sources in collecting mosquitoes (Diptera: Culicidae) in Thailand. Treatments consisted of dry ice pellets, CO2 gas produced from one of three prototype CO2 generator systems (TDA, CUBE, Moustiq-Air Med-e-Cell - MEC), and a CDC light trap without a CO2 source. The best performing prototype from Thailand was then tested in collecting sand flies (Diptera: Psychodidae: Phlebotominae) in Greece. A total of 12,798 mosquitoes and 8,329 sand flies were sampled during the experimentation. The most prevalent mosquito species collected in Thailand were: Culex vishnui Theobald > Anopheles minimus Theobald > Culex tritaeniorhynchus Giles > Anopheles sawadwongporni Rattanarithikul & Green. By far the most prevalent sand fly species collected in Thessaloniki was Phlebotomus perfiliewi Parrot followed by Phlebotomus tobbi Adler and Theodor and Phlebotomus simici Nitzulescu. In general, the TDA treatment was the only treatment with no significant difference from the dry ice-treatment in mean trap catches. Although dry ice-baited traps caught higher numbers of mosquitoes and sand flies than the TDA-baited traps, there was no difference in the number of species collected. Results indicate that the traps baited with the TDA CO2 generator were as attractive as traps supplied with dry ice and, therefore, the TDA CO2 generator is a suitable alternative to dry ice as a source of carbon dioxide for use with adult mosquito and sand fly traps.
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http://dx.doi.org/10.1093/jee/toy319DOI Listing
February 2019

Ultra-Low Volume Application of Spinosad (Natular 2EC) Larvicide as a Residual in a Tropical Environment Against and Species.

J Am Mosq Control Assoc 2018 03;34(1):58-62

We investigated the efficacy of a liquid larvicide, Natular 2EC® (spinosad), applied with ultra-low volume sprayer as a residual application during the dry season in southeastern Thailand against 4 medically important species-, , , and . We found that this larvicide could be applied as a residual to dry areas known to collect water and potentially still be effective after rains or irrigation, which could increase the flexibility and efficiency of an integrated vector management program targeting these species. This investigation also demonstrated, for the 1st time, efficacy of spinosad against and .
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http://dx.doi.org/10.2987/17-6692.1DOI Listing
March 2018

Field evaluation of two commercial mosquito traps baited with different attractants and colored lights for malaria vector surveillance in Thailand.

Parasit Vectors 2017 Aug 7;10(1):378. Epub 2017 Aug 7.

Armed Forces Pest Management Board, Silver Spring, MD, USA.

Background: Sampling for adult mosquito populations is a means of evaluating the efficacy of vector control operations. The goal of this study was to evaluate and identify the most efficacious mosquito traps and combinations of attractants for malaria vector surveillance along the Thai-Myanmar border.

Methods: In the first part of the study, the BG-Sentinel™ Trap (BGS Trap) and Centers for Disease Control and Prevention miniature light trap (CDC LT) baited with different attractants (BG-lure® and CO) were evaluated using a Latin square experimental design. The six configurations were BGS Trap with BG-lure, BGS Trap with BG-lure plus CO, BGS Trap with CO, CDC LT with BG-lure, CDC LT with BG lure plus CO, and CDC LT with CO. The second half of the study evaluated the impact of light color on malaria vector collections. Colors included the incandescent bulb, ultraviolet (UV) light-emitting diode (LED), green light stick, red light stick, green LED, and red LED.

Results: A total of 8638 mosquitoes consisting of 42 species were captured over 708 trap-nights. The trap types, attractants, and colored lights affected numbers of female anopheline and Anopheles minimus collected (GLM, P < 0.01). Results revealed that BGS Trap captured many anophelines but was significantly less than the CDC LT. The CDC LT, when baited with BG-lure plus CO captured the greatest number of anopheline females with a catch rate significantly higher than the CDC LT baited with BG-lure or CO alone (P < 0.05). The number of anopheline females collected from the CDC LT baited with CO was greater than the CDC LT baited with BG-lure (646 vs 409 females). None of the alternative lights evaluated exceeded the performance of the incandescent light bulb in terms of the numbers of anopheline and An. minimus collected.

Conclusion: We conclude that the CDC LT augmented with an incandescent light shows high potential for malaria vector surveillance when baited with CO and the BG-lure in combination and can be effectively used as the new gold standard technique for collecting malaria vectors in Thailand.
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http://dx.doi.org/10.1186/s13071-017-2315-1DOI Listing
http://www.ncbi.nlm.nih.gov/pmc/articles/PMC5547504PMC
August 2017

Ivermectin susceptibility and sporontocidal effect in Greater Mekong Subregion Anopheles.

Malar J 2017 07 7;16(1):280. Epub 2017 Jul 7.

Department of Entomology, Armed Forces Research Institute of Medical Sciences, 315/6 Rajvithi Road, Bangkok, 10400, Thailand.

Background: Novel vector control methods that can directly target outdoor malaria transmission are urgently needed in the Greater Mekong Subregion (GMS) to accelerate malaria elimination and artemisinin resistance containment efforts. Ivermectin mass drug administration (MDA) to humans has been shown to effectively kill wild Anopheles and suppress malaria transmission in West Africa. Preliminary laboratory investigations were performed to determine ivermectin susceptibility and sporontocidal effect in GMS Anopheles malaria vectors coupled with pharmacokinetic models of ivermectin at escalating doses.

Methods: A population-based pharmacokinetic model of ivermectin was developed using pre-existing data from a clinical trial conducted in Thai volunteers at the 200 µg/kg dose. To assess ivermectin susceptibility, various concentrations of ivermectin compound were mixed in human blood meals and blood-fed to Anopheles dirus, Anopheles minimus, Anopheles sawadwongporni, and Anopheles campestris. Mosquito survival was monitored daily for 7 days and a non-linear mixed effects model with probit analyses was used to calculate concentrations of ivermectin that killed 50% (LC) of mosquitoes for each species. Blood samples were collected from Plasmodium vivax positive patients and offered to mosquitoes with or without ivermectin at the ivermectin LC or LC for An. dirus and An. minimus.

Results: The GMS Anopheles displayed a range of susceptibility to ivermectin with species listed from most to least susceptible being An. minimus (LC = 16.3 ng/ml) > An. campestris (LC = 26.4 ng/ml) = An. sawadwongporni (LC = 26.9 ng/ml) > An. dirus (LC = 55.6 ng/ml). Mosquito survivorship results, the pharmacokinetic model, and extensive safety data indicated that ivermectin 400 µg/kg is the ideal minimal dose for MDA in the GMS for malaria parasite transmission control. Ivermectin compound was sporontocidal to P. vivax in both An. dirus and An. minimus at the LC and LC concentrations.

Conclusions: Ivermectin is lethal to dominant GMS Anopheles malaria vectors and inhibits sporogony of P. vivax at safe human relevant concentrations. The data suggest that ivermectin MDA has potential in the GMS as a vector and transmission blocking control tool to aid malaria elimination efforts.
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http://dx.doi.org/10.1186/s12936-017-1923-8DOI Listing
http://www.ncbi.nlm.nih.gov/pmc/articles/PMC5501099PMC
July 2017

Secreted NS1 Protects Dengue Virus from Mannose-Binding Lectin-Mediated Neutralization.

J Immunol 2016 11 19;197(10):4053-4065. Epub 2016 Oct 19.

Division of Dengue Hemorrhagic Fever Research, Department of Research and Development, Faculty of Medicine, Siriraj Hospital, Mahidol University, Bangkok 10700, Thailand;

Flavivirus nonstructural protein 1 (NS1) is a unique secreted nonstructural glycoprotein. Although it is absent from the flavivirus virion, intracellular and extracellular forms of NS1 have essential roles in viral replication and the pathogenesis of infection. The fate of NS1 in insect cells has been more controversial, with some reports suggesting it is exclusively cell associated. In this study, we confirm NS1 secretion from cells of insect origin and characterize its physical, biochemical, and functional properties in the context of dengue virus (DENV) infection. Unlike mammalian cell-derived NS1, which displays both high mannose and complex type N-linked glycans, soluble NS1 secreted from DENV-infected insect cells contains only high mannose glycans. Insect cell-derived secreted NS1 also has different physical properties, including smaller and more heterogeneous sizes and the formation of less stable NS1 hexamers. Both mammalian and insect cell-derived NS1 bind to complement proteins C1s, C4, and C4-binding protein, as well as to a novel partner, mannose-binding lectin. Binding of NS1 to MBL protects DENV against mannose-binding lectin-mediated neutralization by the lectin pathway of complement activation. As we detected secreted NS1 and DENV together in the saliva of infected Aedes aegypti mosquitoes, these findings suggest a mechanism of viral immune evasion at the very earliest phase of infection.
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http://dx.doi.org/10.4049/jimmunol.1600323DOI Listing
http://www.ncbi.nlm.nih.gov/pmc/articles/PMC5123808PMC
November 2016

Global genetic diversity of Aedes aegypti.

Mol Ecol 2016 11 14;25(21):5377-5395. Epub 2016 Oct 14.

Yale University, 21 Sachem Street, New Haven, CT, 06520-8105, USA.

Mosquitoes, especially Aedes aegypti, are becoming important models for studying invasion biology. We characterized genetic variation at 12 microsatellite loci in 79 populations of Ae. aegypti from 30 countries in six continents, and used them to infer historical and modern patterns of invasion. Our results support the two subspecies Ae. aegypti formosus and Ae. aegypti aegypti as genetically distinct units. Ae. aegypti aegypti populations outside Africa are derived from ancestral African populations and are monophyletic. The two subspecies co-occur in both East Africa (Kenya) and West Africa (Senegal). In rural/forest settings (Rabai District of Kenya), the two subspecies remain genetically distinct, whereas in urban settings, they introgress freely. Populations outside Africa are highly genetically structured likely due to a combination of recent founder effects, discrete discontinuous habitats and low migration rates. Ancestral populations in sub-Saharan Africa are less genetically structured, as are the populations in Asia. Introduction of Ae. aegypti to the New World coinciding with trans-Atlantic shipping in the 16th to 18th centuries was followed by its introduction to Asia in the late 19th century from the New World or from now extinct populations in the Mediterranean Basin. Aedes mascarensis is a genetically distinct sister species to Ae. aegypti s.l. This study provides a reference database of genetic diversity that can be used to determine the likely origin of new introductions that occur regularly for this invasive species. The genetic uniqueness of many populations and regions has important implications for attempts to control Ae. aegypti, especially for the methods using genetic modification of populations.
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http://dx.doi.org/10.1111/mec.13866DOI Listing
http://www.ncbi.nlm.nih.gov/pmc/articles/PMC5123671PMC
November 2016

Genetic Characterization of Spondweni and Zika Viruses and Susceptibility of Geographically Distinct Strains of Aedes aegypti, Aedes albopictus and Culex quinquefasciatus (Diptera: Culicidae) to Spondweni Virus.

PLoS Negl Trop Dis 2016 Oct 26;10(10):e0005083. Epub 2016 Oct 26.

The University of Texas Medical Branch, Institute for Human Infections and Immunity, Department of Pathology and Center for Biodefense and Emerging Infectious Diseases, Galveston, Texas.

Background: Zika virus (ZIKV) has extended its known geographic distribution to the New World and is now responsible for severe clinical complications in a subset of patients. While substantial genetic and vector susceptibility data exist for ZIKV, less is known for the closest related flavivirus, Spondweni virus (SPONV). Both ZIKV and SPONV have been known to circulate in Africa since the mid-1900s, but neither has been genetically characterized by gene and compared in parallel. Furthermore, the susceptibility of peridomestic mosquito species incriminated or suspected in the transmission of ZIKV to SPONV was unknown.

Methodology/principal Findings: In this study, two geographically distinct strains of SPONV were genetically characterized and compared to nine genetically and geographically distinct ZIKV strains. Additionally, the susceptibility of both SPONV strains was determined in three mosquito species. The open reading frame (ORF) of the SPONV 1952 Nigerian Chuku strain, exhibited a nucleotide and amino acid identity of 97.8% and 99.2%, respectively, when compared to the SPONV 1954 prototype South African SA Ar 94 strain. The ORF of the SPONV Chuku strain exhibited a nucleotide and amino acid identity that ranged from 68.3% to 69.0% and 74.6% to 75.0%, respectively, when compared to nine geographically and genetically distinct strains of ZIKV. The ORF of the nine African and Asian lineage ZIKV strains exhibited limited nucleotide divergence. Aedes aegypti, Ae. albopictus and Culex quinquefasciatus susceptibility and dissemination was low or non-existent following artificial infectious blood feeding of moderate doses of both SPONV strains.

Conclusions/significance: SPONV and ZIKV nucleotide and amino acid divergence coupled with differences in geographic distribution, ecology and vector species support previous reports that these viruses are separate species. Furthermore, the low degree of SPONV infection or dissemination in Ae. albopictus, Ae. aegypti and Cx. quinquefasciatus following exposure to two geographically and genetically distinct virus strains suggest a low potential for these species to serve as vectors.
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http://dx.doi.org/10.1371/journal.pntd.0005083DOI Listing
http://www.ncbi.nlm.nih.gov/pmc/articles/PMC5082648PMC
October 2016

Semi-Field Evaluation of Metofluthrin-Impregnated Nets on Host-Seeking Aedes aegypti and Anopheles dirus.

J Am Mosq Control Assoc 2016 Jun;32(2):130-8

3  Environmental Health Branch, United States Army Medical Department Center and School, San Antonio, TX 78234.

The efficacy of a metofluthrin-impregnated net (MIN) known as the "Mushikonazu" on the house entry behavior of female Aedes aegypti and Anopheles dirus mosquitoes was evaluated using a semi-field 50-m tunnel setup. While the MIN is labeled for the control of chironomids and moth flies, this study determined the feasibility of using the device, given its current construction and metofluthrin formulation, as a spatial repellent against mosquitoes. Sentinel and cone bioassays were used to determine the insecticidal effect of the MIN. A spatial activity index (SAI) was calculated to evaluate responses of the mosquitoes. For the spatial repellent evaluation against Ae. aegypti, the overall mean of SAI was slightly less than 0 at wk 1 after the MIN application and then decreased for the last 4 wk showing a preference to treatment tent. For An. dirus, the mean SAI at wk 1 was positive, indicating a presumed repellent effect of the MIN against An. dirus. For the subsequent 4 wk, the SAI was negative, indicating a preference for the MIN. Results suggested that the MIN may not be a promising approach to repel Ae. aegypti and An. dirus under field conditions in Thailand. However, it remains probable that the MIN may be effective as a spatial repellent if modifications are made to the metofluthrin concentration or formulation and/or the construction of the device.
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http://dx.doi.org/10.2987/moco-32-02-130-138.1DOI Listing
June 2016

No evidence for local adaptation of dengue viruses to mosquito vector populations in Thailand.

Evol Appl 2016 04 24;9(4):608-18. Epub 2016 Feb 24.

Insect-Virus Interactions Group Department of Genomes and Genetics Institut Pasteur Paris France; Unité de Recherche Associée Centre National de la Recherche Scientifique Paris France.

Despite their epidemiological importance, the evolutionary forces that shape the spatial structure of dengue virus genetic diversity are not fully understood. Fine-scale genetic structure of mosquito vector populations and evidence for genotype × genotype interactions between dengue viruses and their mosquito vectors are consistent with the hypothesis that the geographical distribution of dengue virus genetic diversity may reflect viral adaptation to local mosquito populations. To test this hypothesis, we measured vector competence in all sympatric and allopatric combinations of 14 low-passage dengue virus isolates and two wild-type populations of Aedes aegypti mosquitoes sampled in Bangkok and Kamphaeng Phet, two sites located about 300 km apart in Thailand. Despite significant genotype × genotype interactions, we found no evidence for superior vector competence in sympatric versus allopatric vector-virus combinations. Viral phylogenetic analysis revealed no geographical clustering of the 14 isolates, suggesting that high levels of viral migration (gene flow) in Thailand may counteract spatially heterogeneous natural selection. We conclude that it is unlikely that vector-mediated selection is a major driver of dengue virus adaptive evolution at the regional scale that we examined. Dengue virus local adaptation to mosquito vector populations could happen, however, in places or times that we did not test, or at a different geographical scale.
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http://dx.doi.org/10.1111/eva.12360DOI Listing
http://www.ncbi.nlm.nih.gov/pmc/articles/PMC4831462PMC
April 2016

Improving dengue virus capture rates in humans and vectors in Kamphaeng Phet Province, Thailand, using an enhanced spatiotemporal surveillance strategy.

Am J Trop Med Hyg 2015 Jul 18;93(1):24-32. Epub 2015 May 18.

Viral Diseases Branch, Walter Reed Army Institute of Research, Silver Spring, Maryland; Department of Virology, United States Army Medical Component, Armed Forces Research Institute of Medical Sciences, Bangkok, Thailand; Department of Geography, University at Buffalo, Buffalo, New York; Department of Entomology, Armed Forces Research Institute of Medical Sciences, Bangkok, Thailand; Bureau of Epidemiology, Department of Disease Control Sciences, Ministry of Public Health, Nonthaburi, Thailand; Department of Entomology, University of California, Davis, Davis, California; Institute for Immunology and Informatics, University of Rhode Island, Providence, Rhode Island; Insect-Virus Interactions Group, Department of Genomes and Genetics, Institut Pasteur, Centre National de la Recherche Scientifique, Paris, France; Department of Infectious Diseases, State University of New York, Syracuse, New York; Fogarty International Center, National Institutes of Health, Bethesda, Maryland.

Dengue is of public health importance in tropical and sub-tropical regions. Dengue virus (DENV) transmission dynamics was studied in Kamphaeng Phet Province, Thailand, using an enhanced spatiotemporal surveillance of 93 hospitalized subjects with confirmed dengue (initiates) and associated cluster individuals (associates) with entomologic sampling. A total of 438 associates were enrolled from 208 houses with household members with a history of fever, located within a 200-m radius of an initiate case. Of 409 associates, 86 (21%) had laboratory-confirmed DENV infection. A total of 63 (1.8%) of the 3,565 mosquitoes collected were dengue polymerase chain reaction positive (PCR+). There was a significant relationship between spatial proximity to the initiate case and likelihood of detecting DENV from associate cases and Aedes mosquitoes. The viral detection rate from human hosts and mosquito vectors in this study was higher than previously observed by the study team in the same geographic area using different methodologies. We propose that the sampling strategy used in this study could support surveillance of DENV transmission and vector interactions.
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http://dx.doi.org/10.4269/ajtmh.14-0242DOI Listing
http://www.ncbi.nlm.nih.gov/pmc/articles/PMC4497898PMC
July 2015

Differential susceptibility of two field aedes aegypti populations to a low infectious dose of dengue virus.

PLoS One 2014 24;9(3):e92971. Epub 2014 Mar 24.

Insect-Virus Interactions Group, Department of Genomes and Genetics, Institut Pasteur - Centre National de la Recherche Scientifique, Unité de Recherche Associée 3012, Paris, France.

Background: The infectious dose required to infect mosquito vectors when they take a blood meal from a viremic person is a critical parameter underlying the probability of dengue virus (DENV) transmission. Because experimental vector competence studies typically examine the proportion of mosquitoes that become infected at intermediate or high DENV infectious doses in the blood meal, the minimum blood meal titer required to infect mosquitoes is poorly documented. Understanding the factors influencing the lower infectiousness threshold is epidemiologically significant because it determines the transmission potential of humans with a low DENV viremia, possibly including inapparent infections, and during the onset and resolution of the viremic period of acutely infected individuals.

Methodology/principal Findings: We compared the susceptibility of two field-derived Aedes aegypti populations from Kamphaeng Phet, Thailand when they were orally exposed to low titers of six DENV-2 isolates derived from the serum of naturally infected humans living in the same region. The infectious dose, time-point post-blood feeding, viral isolate and mosquito population, were significant predictors of the proportion of mosquitoes that became infected. Importantly, the dose-response profile differed significantly between the two Ae. aegypti populations. Although both mosquito populations had a similar 50% oral infectious dose (OID50), the slope of the dose-response was shallower in one population, resulting in a markedly higher susceptibility at low blood meal titers.

Conclusions/significance: Our results indicate that mosquitoes in nature vary in their infectious dose-response to DENV. Thus, different mosquito populations have a differential ability to acquire DENV infection at low viremia levels. Future studies on human-to-mosquito DENV transmission should not be limited to OID50 values, but rather they should be expanded to account for the shape of the dose-response profile across a range of virus titers.
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http://journals.plos.org/plosone/article?id=10.1371/journal.pone.0092971PLOS
http://www.ncbi.nlm.nih.gov/pmc/articles/PMC3963970PMC
November 2014

Genetic mapping of specific interactions between Aedes aegypti mosquitoes and dengue viruses.

PLoS Genet 2013 1;9(8):e1003621. Epub 2013 Aug 1.

Institut Pasteur, Centre National de la Recherche Scientifique, Unité de Recherche Associée 3012, Paris, France.

Specific interactions between host genotypes and pathogen genotypes (G×G interactions) are commonly observed in invertebrate systems. Such specificity challenges our current understanding of invertebrate defenses against pathogens because it contrasts the limited discriminatory power of known invertebrate immune responses. Lack of a mechanistic explanation, however, has questioned the nature of host factors underlying G×G interactions. In this study, we aimed to determine whether G×G interactions observed between dengue viruses and their Aedes aegypti vectors in nature can be mapped to discrete loci in the mosquito genome and to document their genetic architecture. We developed an innovative genetic mapping strategy to survey G×G interactions using outbred mosquito families that were experimentally exposed to genetically distinct isolates of two dengue virus serotypes derived from human patients. Genetic loci associated with vector competence indices were detected in multiple regions of the mosquito genome. Importantly, correlation between genotype and phenotype was virus isolate-specific at several of these loci, indicating G×G interactions. The relatively high percentage of phenotypic variation explained by the markers associated with G×G interactions (ranging from 7.8% to 16.5%) is consistent with large-effect host genetic factors. Our data demonstrate that G×G interactions between dengue viruses and mosquito vectors can be assigned to physical regions of the mosquito genome, some of which have a large effect on the phenotype. This finding establishes the existence of tangible host genetic factors underlying specific interactions between invertebrates and their pathogens in a natural system. Fine mapping of the uncovered genetic loci will elucidate the molecular mechanisms of mosquito-virus specificity.
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http://dx.doi.org/10.1371/journal.pgen.1003621DOI Listing
http://www.ncbi.nlm.nih.gov/pmc/articles/PMC3731226PMC
March 2014

Development and evaluation of a pyriproxyfen-treated device to control the dengue vector, Aedes aegypti (L.) (Diptera:Culicidae).

Southeast Asian J Trop Med Public Health 2013 Mar;44(2):167-78

Department of Entomology, Armed Forces Research Institute of Medical Sciences, Bangkok, Thailand.

The resurgence of dengue fever and the chikungunya epidemic make the control of Aedes aegypti mosquitoes, the vectors of these diseases, critically important. We developed and evaluated an Ae. aegypti control device that is visually-attractive to mosquitoes. This pyriproxyfen-treated device was evaluated for its impact on Ae. aegypti egg production and population dynamics in dengue-endemic areas in Thailand. The device consists of a "high rise" shaped ovitrap/ resting station covered with black cotton cloth. The device is easily collapsible and transportable. Ae. aegypti are generally drawn towards darker, shadier areas making this device physically attractive as a resting station to mosquitoes of all physiological stages. The results show this device suppressed Ae. aegypti populations after it was introduced into a village. The observed effect was primarily the result of the Ae. aegypti exposure to pyriproxyfen shortly after adult emergence or after taking a blood meal resulting in decreased egg production. We believe the device may be further improved physically and the formulation should be replaced to provide even better efficacy for controlling Ae. aegypti mosquito, populations.
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March 2013

Variable clinical responses of a scrub typhus outbred mouse model to feeding by Orientia tsutsugamushi infected mites.

Exp Appl Acarol 2012 Sep 24;58(1):23-34. Epub 2012 Apr 24.

Department of Entomology, U.S. Army Medical Component, Armed Forces Research Institute of Medical Sciences, Bangkok, Thailand.

Rodents are the natural hosts for Leptotrombidium mites that transmit Orientia tsutsugamushi, the causative agent of scrub typhus, a potentially fatal febrile human disease. Utilizing mite lines that included O. tsutsugamushi infected and non-infected Leptotrombidium species we investigated the varied infection response of outbred mice (ICR) exposed to L. chiangraiensis (Lc), L. imphalum (Li) and L. deliense (Ld). Each of six mite lines (Lc1, Lc5, Li3, Li4, Li7 and Ld) was separately placed in the inner ears of ICR mice either as a single individual (individual feeding, IF) or as a group of 2-4 individuals (pool feeding, PF). The species of infected chigger feeding on mice significantly affected mortality rates of the mice, with mite lines of Lc causing higher mean (±SE) mortality (90.7 ± 3.6 %) than mite lines of Li (62.9 ± 5.6 %) or Ld (53.6 ± 5.8 %). Mouse responses which included time to death, food consumption and total mice weight change depended on mite species and their O. tsutsugamushi genotype, more than on feeding procedure (IF vs. PF) except for mite lines within the Lc. Infected mite lines of Lc were the most virulent infected mites assessed whereas the infected Ld species was the least virulent for the ICR. Mice killed by various mite lines showed enlarged spleens and produced ascites. The results of this investigation of the clinical responses of ICR mice to feeding by various infected mite lines indicated that the different species of infected mites and their O. tsutsugamushi genotype produced different clinical presentations in ICR mice, a scrub typhus mouse model which mimics the natural transmission of O. tsutsugamushi that is critical for understanding scrub typhus disease in terms of natural transmission, host-pathogen-vector interaction and vaccine development.
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http://dx.doi.org/10.1007/s10493-012-9563-8DOI Listing
September 2012

Dengue-1 virus clade replacement in Thailand associated with enhanced mosquito transmission.

J Virol 2012 Feb 30;86(3):1853-61. Epub 2011 Nov 30.

Department of Virology, Institut Pasteur, Paris, France.

Dengue viruses (DENV) are characterized by extensive genetic diversity and can be organized in multiple, genetically distinct lineages that arise and die out on a regular basis in regions where dengue is endemic. A fundamental question for understanding DENV evolution is the relative extent to which stochastic processes (genetic drift) and natural selection acting on fitness differences among lineages contribute to lineage diversity and turnover. Here, we used a set of recently collected and archived low-passage DENV-1 isolates from Thailand to examine the role of mosquito vector-virus interactions in DENV evolution. By comparing the ability of 23 viruses isolated on different dates between 1985 and 2009 to be transmitted by a present-day Aedes aegypti population from Thailand, we found that a major clade replacement event in the mid-1990s was associated with virus isolates exhibiting increased titers in the vector's hemocoel, which is predicted to result in a higher probability of transmission. This finding is consistent with the hypothesis that selection for enhanced transmission by mosquitoes is a possible mechanism underlying major DENV clade replacement events. There was significant variation in transmission potential among isolates within each clade, indicating that in addition to vector-driven selection, other evolutionary forces act to maintain viral genetic diversity. We conclude that occasional adaptive processes involving the mosquito vector can drive major DENV lineage replacement events.
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http://dx.doi.org/10.1128/JVI.06458-11DOI Listing
http://www.ncbi.nlm.nih.gov/pmc/articles/PMC3264336PMC
February 2012

Behavioral observations and sound recordings of free-flight mating swarms of Ae. Aegypti (Diptera: Culicidae) in Thailand.

J Med Entomol 2011 Jul;48(4):941-6

Department of Entomology, Cornell University, 3138 Comstock Hall, Ithaca, NY 14853, USA.

Sound plays an important role in the mating behavior of mosquitoes, including Aedes aegypti (L). Males orient to the fundamental wing beat frequency of females, and both sexes actively modulate their flight tone before mating to converge at harmonic frequencies. The majority of studies on mosquito mating acoustics have been conducted in the laboratory using tethered individuals. In this study, we present the first free-flight recording of naturally forming Ae. aegypti swarms in Thailand. We describe mating behaviors and present results on the flight tone frequency and dynamics of wild pairs in free flight. To assess the importance of these behaviors in vector control programs, especially those using genetically modified mosquitoes, it will be critical to use methods, such as those described in this work, to measure mosquito mating behaviors in the field.
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http://www.ncbi.nlm.nih.gov/pmc/articles/PMC4948640PMC
http://dx.doi.org/10.1603/me11019DOI Listing
July 2011

Worldwide patterns of genetic differentiation imply multiple 'domestications' of Aedes aegypti, a major vector of human diseases.

Proc Biol Sci 2011 Aug 12;278(1717):2446-54. Epub 2011 Jan 12.

Department of Ecology and Evolutionary Biology, Yale University, New Haven, CT 06520, USA.

Understanding the processes by which species colonize and adapt to human habitats is particularly important in the case of disease-vectoring arthropods. The mosquito species Aedes aegypti, a major vector of dengue and yellow fever viruses, probably originated as a wild, zoophilic species in sub-Saharan Africa, where some populations still breed in tree holes in forested habitats. Many populations of the species, however, have evolved to thrive in human habitats and to bite humans. This includes some populations within Africa as well as almost all those outside Africa. It is not clear whether all domestic populations are genetically related and represent a single 'domestication' event, or whether association with human habitats has developed multiple times independently within the species. To test the hypotheses above, we screened 24 worldwide population samples of Ae. aegypti at 12 polymorphic microsatellite loci. We identified two distinct genetic clusters: one included all domestic populations outside of Africa and the other included both domestic and forest populations within Africa. This suggests that human association in Africa occurred independently from that in domestic populations across the rest of the world. Additionally, measures of genetic diversity support Ae. aegypti in Africa as the ancestral form of the species. Individuals from domestic populations outside Africa can reliably be assigned back to their population of origin, which will help determine the origins of new introductions of Ae. aegypti.
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http://dx.doi.org/10.1098/rspb.2010.2469DOI Listing
http://www.ncbi.nlm.nih.gov/pmc/articles/PMC3125627PMC
August 2011

Factors associated with male mating success of the dengue vector mosquito, Aedes aegypti.

Am J Trop Med Hyg 2009 Mar;80(3):395-400

Department of Entomology, Cornell University, Ithaca, New York 14853, USA.

We studied the effects of male Aedes aegypti age, body size, and density on mating success under laboratory and field conditions. Older males under field conditions transferred the greatest number of sperm to females (1,152 by 1-day-old males to 1,892 sperm by 10-day-old males). Larger males inseminated females with more sperm than smaller ones. Male age, female body size, and density also influenced male mating success. Larger females successfully mated with males more often than smaller females, especially with older males (> 25 days old). Female insemination rates in small high-density laboratory cages (0.009 m(3)) were artificially high (81.6-98.7%) compared with rates (65.4-84.6%) in large low-density field cages (9 m(3)). This is the first study to systematically evaluate the effect of Ae. aegypti male body size and age on sperm transfer to females and the first one to evaluate the mating performance of males in a field setting.
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March 2009

Age and body size influence male sperm capacity of the dengue vector Aedes aegypti (Diptera: Culicidae).

J Med Entomol 2007 May;44(3):422-6

Department of Entomology, Cornell University, Ithaca, NY 14853, USA.

Understanding mosquito mating biology is essential for studies of mosquito behavior, gene flow, population structure, and genetic control. In the current study, we examine the effect of age and body size on spermatozoa number in two laboratory strains of the dengue vector, Aedes aegypti (L.), Thailand and Rockefeller (ROCK), and in wild-collected mosquitoes from Thailand. Body size was a major predictor of total spermatozoa number, with significantly greater sperm numbers in large (2.27-mm wing length) versus small males (1.85-mm wing length) within the same age group. Total sperm capacity also varied by male age. Spermatozoa numbers in virgin Ae. aegypti males increased significantly up to 10 d after emergence and then leveled off until 20 d. Significant variations in sperm number were detected among Ae. aegypti strains, with wild-collected mosquitoes having the greatest total number of sperm. Our study provides the first evidence of spermatogenesis in adult mosquitoes and indicates high rates of spermatogenesis in male mosquitoes up to 10 d of age (3.3 degree-days). Our results emphasize the potential role of body size and age on the mating capacity of this important vector of dengue and yellow fever viruses.
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http://dx.doi.org/10.1603/0022-2585(2007)44[422:aabsim]2.0.co;2DOI Listing
May 2007

Blood feeding patterns of Aedes aegypti and Aedes albopictus in Thailand.

J Med Entomol 2005 Sep;42(5):844-9

Department of Entomology, Cornell University, Ithaca, New York 14853, USA.

Aedes aegypti (L.) and Aedes albopictus (Skuse) were collected with aspirators from Mae Sot, Nakhon Sawan, Nakhon Ratchasima, Surat Thani, and Phatthalung study sites in Thailand from July 2003 though April 2004. The sandwich-B enzyme-linked immunosorbent assay was used to analyze 1,021 blood-fed specimens. Ae. aegypti almost exclusively fed on humans (99%, 658/664) in single host species, and 97% (86/88) of multiple-host bloodmeals included at least one human host. A low frequency of other hosts, including bovine, swine, cat, rat, and chicken were detected, but they represented <1% of bloodmeals. An even higher percentage of human feeding was detected in Ae. albopictus. Hosts of Ae. albopictus collected from sites in southern Thailand were entirely human (100%, n = 105) from both single and mixed meals. In the small number of double-host meals from Ae. albopictus, we detected 3.8% as swine-human and <1% from dog-human and cat-human. Forage ratios for Ae. aegypti indicated that human, dog, and swine were preferred hosts in order of preference. In contrast, bovine and chicken were avoided hosts for this species in Thailand.
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http://dx.doi.org/10.1093/jmedent/42.5.844DOI Listing
September 2005

Insecticide susceptibility of Aedes aegypti and Aedes albopictus across Thailand.

J Med Entomol 2005 Sep;42(5):821-5

Department of Entomology, Cornell University, Ithaca, New York 14853, USA.

Aedes aegypti (L.) and Aedes albopictus (Skuse), two important vectors of dengue fever and dengue hemorrhagic fever, were collected from Mae Sot, Nakhon Sawan, Nakhon Ratchasima, Surat Thani, and Phatthalung, Thailand, from July 2003 to April 2004. The patterns of insecticide susceptibility to temephos, malathion, and permethrin of both Ae. aegypti and Ae. albopictus larvae were determined. Ae. aegypti from all study sites were resistant to permethrin, they but were susceptible to malathion. Resistance to temephos was detected in all strains of Ae. aegypti, except those from Nakhon Ratchasima. Ae. albopictus larvae had low levels of resistance to all three insecticides, except Mae Sot and Phatthalung strains, which were resistant to permethrin.
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http://dx.doi.org/10.1603/0022-2585(2005)042[0821:ISOAAA]2.0.CO;2DOI Listing
September 2005
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