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1.
J Vis Exp ; (169)2021 03 12.
Artigo em Inglês | MEDLINE | ID: mdl-33779612

RESUMO

The control of such human diseases as dengue, Zika, and chikungunya relies on the control of their vector, the Aedes aegypti mosquito, because there is no prevention. Control of mosquito vectors can rely on chemicals applied to the immature and adult stages, which can contribute to the mortality of non-targets and more importantly, lead to insecticide resistance in the vector. The sterile insect technique (SIT) is a method of controlling populations of pests through the release of sterilized adult males that mate with wild females to produce non-viable offspring. This paper describes the process of producing sterile males for use in an operational SIT program for the control of Aedes aegypti mosquitoes. Outlined here are the steps used in the program including rearing and maintaining a colony, separating male and female pupae, irradiating and marking adult males, and shipping Aedes aegypti males to the release site. Also discussed are procedural caveats, program limitations, and future objectives.


Assuntos
Aedes/fisiologia , Fertilidade/efeitos da radiação , Resistência a Inseticidas , Controle de Mosquitos/métodos , Mosquitos Vetores/fisiologia , Pupa/fisiologia , Esterilização Reprodutiva/métodos , Aedes/efeitos da radiação , Animais , Feminino , Humanos , Masculino , Mosquitos Vetores/efeitos da radiação , Pupa/efeitos da radiação
2.
BMC Genet ; 21(Suppl 2): 142, 2020 12 18.
Artigo em Inglês | MEDLINE | ID: mdl-33339503

RESUMO

BACKGROUND: Aedes aegypti is the primary vector of arthropod-borne viruses and one of the most widespread and invasive mosquito species. Due to the lack of efficient specific drugs or vaccination strategies, vector population control methods, such as the sterile insect technique, are receiving renewed interest. However, availability of a reliable genetic sexing strategy is crucial, since there is almost zero tolerance for accidentally released females. Development of genetic sexing strains through classical genetics is hindered by genetic recombination that is not suppressed in males as is the case in many Diptera. Isolation of naturally-occurring or irradiation-induced inversions can enhance the genetic stability of genetic sexing strains developed through genetically linking desirable phenotypes with the male determining region. RESULTS: For the induction and isolation of inversions through irradiation, 200 male pupae of the 'BRA' wild type strain were irradiated at 30 Gy and 100 isomale lines were set up by crossing with homozygous 'red-eye' (re) mutant females. Recombination between re and the M locus and the white (w) gene (causing a recessive white eye phenotype when mutated) and the M locus was tested in 45 and 32 lines, respectively. One inversion (Inv35) reduced recombination between both re and the M locus, and wand the M locus, consistent with the presence of a rather extended inversion between the two morphological mutations, that includes the M locus. Another inversion (Inv5) reduced recombination only between w and the M locus. In search of naturally-occurring, recombination-suppressing inversions, homozygous females from the red eye and the white eye strains were crossed with seventeen and fourteen wild type strains collected worldwide, representing either recently colonized or long-established laboratory populations. Despite evidence of varying frequencies of recombination, no combination led to the elimination or substantial reduction of recombination. CONCLUSION: Inducing inversions through irradiation is a feasible strategy to isolate recombination suppressors either on the M or the m chromosome for Aedes aegypti. Such inversions can be incorporated in genetic sexing strains developed through classical genetics to enhance their genetic stability and support SIT or other approaches that aim to population suppression through male-delivered sterility.


Assuntos
Aedes/genética , Aedes/efeitos da radiação , Infertilidade/genética , Recombinação Genética/efeitos da radiação , Animais , Feminino , Raios gama , Genes de Insetos , Marcadores Genéticos , Controle de Insetos , Masculino , Mosquitos Vetores/genética , Mosquitos Vetores/efeitos da radiação
3.
Parasit Vectors ; 13(1): 198, 2020 Apr 17.
Artigo em Inglês | MEDLINE | ID: mdl-32303257

RESUMO

BACKGROUND: Radiation induced sterility is the basis of the Sterile Insect Technique, by which a target insect pest population is suppressed by releasing artificially reared sterile males of the pest species in overflooding numbers over a target site. In order for the sterile males to be of high biological quality, effective standard irradiation protocols are required. Following studies investigating the effects of mosquito pupae irradiation in water versus in air, there is a need to investigate the oxy-regulatory behavior of mosquito pupae in water to better understand the consequences of irradiation in hypoxic versus normoxic conditions. METHODS: Pupae of Aedes aegypti, Ae. albopictus, and Anopheles arabiensis were submerged in water inside air-tight 2 ml glass vials at a density of 100 pupae/ml and the dissolved oxygen (DO) levels in the water were measured and plotted over time. In addition, male pupae of Ae. aegypti (aged 40-44 h), Ae. albopictus (aged 40-44 h) and An. arabiensis (aged 20-24 h) were irradiated in a gammacell220 at increasing doses in either hypoxic (water with < 0.5% O2 content) or normoxic (in air) conditions. The males were then mated to virgin females and resulting eggs were checked for induced sterility. RESULTS: All three species depleted the water of DO to levels under 0.5% within 30 minutes, with An. arabiensis consuming oxygen the fastest at under 10 minutes. Following irradiation, the protective effect of hypoxia was observed across species and doses (P < 0.0001), increasing at higher doses. This effect was most pronounced in An. arabiensis. CONCLUSIONS: The consumption of dissolved oxygen by pupae submerged in water was significantly different between species, indicating that their oxy-regulatory capacity seems to have possibly evolved according to their preferred breeding site characteristics. This needs to be considered when sterilizing male mosquitoes at pupal stage in water. Depending on species, their DO consumption rates and their density, irradiation doses needed to achieve full sterility may vary significantly. Further assessments are required to ascertain optimal conditions in terms of ambient atmosphere during pupal irradiation to produce competitive sterile males, and temperature and density dependent effects are expected.


Assuntos
Aedes/efeitos da radiação , Anopheles/efeitos da radiação , Hipóxia , Pupa/efeitos da radiação , Esterilização/métodos , Animais , Feminino , Infertilidade Masculina , Masculino , Controle de Mosquitos/métodos , Mosquitos Vetores/efeitos da radiação , Água/química
4.
PLoS Negl Trop Dis ; 14(3): e0008047, 2020 03.
Artigo em Inglês | MEDLINE | ID: mdl-32187187

RESUMO

Since Zika virus (ZIKV) emerged as a global human health threat, numerous studies have pointed to Aedes aegypti as the primary vector due to its high competence and propensity to feed on humans. The majority of vector competence studies have been conducted between 26-28°C, but arboviral extrinsic incubation periods (EIPs), and therefore transmission efficiency, are known to be affected strongly by temperature. To better understand the relationship between ZIKV EIPs and temperature, we evaluated the effect of adult mosquito exposure temperature on ZIKV infection, dissemination, and transmission in Ae. aegypti at four temperatures: 18°C, 21°C, 26°C, and 30°C. Mosquitoes were exposed to viremic mice infected with a 2015 Puerto Rican ZIKV strain, and engorged mosquitoes were sorted into the four temperatures with 80% RH and constant access to 10% sucrose. ZIKV infection, dissemination, and transmission rates were assessed via RT-qPCR from individual mosquito bodies, legs and wings, and saliva, respectively, at three to five time points per temperature from three to 31 days, based on expectations from other flavivirus EIPs. The median time from ZIKV ingestion to transmission (median EIP, EIP50) at each temperature was estimated by fitting a generalized linear mixed model for each temperature. EIP50 ranged from 5.1 days at 30°C to 24.2 days at 21°C. At 26°C, EIP50 was 9.6 days. At 18°C, only 15% transmitted by day 31 so EIP50 could not be estimated. This is among the first studies to characterize the effects of temperature on ZIKV EIP in Ae. aegypti, and the first to do so based on feeding of mosquitoes on a live, viremic host. This information is critical for modeling ZIKV transmission dynamics to understand geographic and seasonal limits of ZIKV risk; it is especially relevant for determining risk in subtropical regions with established Ae. aegypti populations and relatively high rates of return travel from the tropics (e.g. California or Florida), as these regions typically experience cooler temperature ranges than tropical regions.


Assuntos
Aedes/efeitos da radiação , Aedes/virologia , Exposição Ambiental , Mosquitos Vetores/efeitos da radiação , Mosquitos Vetores/virologia , Temperatura , Zika virus/crescimento & desenvolvimento , Estruturas Animais/virologia , Animais , Modelos Animais de Doenças , Transmissão de Doença Infecciosa , Feminino , Camundongos , Modelos Estatísticos , RNA Viral/análise , Reação em Cadeia da Polimerase em Tempo Real , Reação em Cadeia da Polimerase Via Transcriptase Reversa , Fatores de Tempo , Infecção por Zika virus/transmissão
5.
Sci Rep ; 10(1): 2378, 2020 02 11.
Artigo em Inglês | MEDLINE | ID: mdl-32047234

RESUMO

Acoustic larviciding (AL) occurs by exposing mosquito larvae to acoustic energy that ruptures their dorsal tracheal trunks (DTTs) by the expulsion of gas bubbles into the body. In studying this technique, we serendipitously identified undescribed anatomical and physiological respiratory features. The classical theory of respiration is that the siphon and DTTs play obligate roles in respiration. Our results contradict the accepted theory that culicine larvae respire via atmospheric gas exchange. We identified an undescribed tracheal occlusion (TO) at the posterior extremities the DTTs. The TOs appear necessary for the acoustic rupture of DTTs; this constriction prevents the escape of energized gas from the siphon and allows the tracheal system to be pressurized. With a pressurized isolated tracheal system, metabolic gas exchange directly with the atmosphere is unlikely and could mostly occur through the chitin and setae. Future studies are needed to explore respiration and elucidate the mechanisms of oxygen absorption and carbon dioxide elimination.


Assuntos
Aedes/fisiologia , Respiração , Traqueia/efeitos da radiação , Ondas Ultrassônicas/efeitos adversos , Aedes/crescimento & desenvolvimento , Aedes/efeitos da radiação , Animais , Larva/efeitos da radiação , Controle de Pragas/métodos , Traqueia/fisiologia
6.
Parasit Vectors ; 12(1): 578, 2019 Dec 10.
Artigo em Inglês | MEDLINE | ID: mdl-31823817

RESUMO

BACKGROUND: Producing high quality sterile males is vital in Aedes aegypti rear-and-release birth control strategies. Larval diets, rearing temperatures, and their interactions determine the accumulation rates of essential nutrients in larvae, but these factors have been understudied in relation to mass-rearing techniques for producing eminent males. METHODS: We compared the effects of two larval diets, a cereal-legume-based diet (Khan's diet) and a standard larval diet developed in the FAO/IAEA Insect Pest Control Laboratory (IAEA 2 diet). Diets were tested at selected temperatures for both larval and male adult life history traits, adult extreme temperature tolerance, and mating capacity relative to energy reserves of reared male adult Ae. aegypti. RESULTS: Khan's diet resulted in shorter immature development time at each test temperature (except for 25 °C) than an IAEA 2 diet. Larvae reared at 28 °C and 32 °C with Khan's diet demonstrated low pupation rates (c.80%). We accounted for these phenomena as secondary sex ratio manipulation, because a higher proportion of male adults emerged at 28 °C and 32 °C than that for the IAEA 2 diet. In general, the pupal development time shortened as temperature increased, resulting in higher teneral energy reserves in male mosquitoes. High energy reserves allowed male mosquitoes reared with Khan's diet to have higher adult longevity (5-6 days longer when sugar-fed and 2-3 days longer when water-fed) and tolerance of heat stress than those fed on the IAEA 2 diet. The IAEA 2 diet produced larger male mosquitoes than Khan's diet did: mosquitoes fed on Khan's diet were 1.03-1.05 times smaller than those fed on the IAEA 2 diet at 28 °C and 32 °C. No evidence indicated reduced mating capacity for small mosquitoes fed on Khan's diet. CONCLUSIONS: Larvae reared at 28 °C and 32 °C with Khan's diet were characterized by shorter immature development time compared with those fed on the IAEA 2 diet. Adult mosquitoes produced from that larval rearing condition exhibited a significant male bias, long lifespan, and better endurance against extreme temperatures relative to energy reserves. Thus, the larval diet at rearing temperature of 28 °C and 32 °C optimized rearing techniques for the sterile insect programmes. However, mating competitiveness and flight performance of adult males require further investigation.


Assuntos
Aedes/fisiologia , Aedes/efeitos da radiação , Dieta , Traços de História de Vida , Temperatura , Animais , Entomologia/métodos , Comportamento Alimentar , Larva/fisiologia , Larva/efeitos da radiação , Masculino , Comportamento Sexual Animal
7.
J Vector Ecol ; 44(2): 264-270, 2019 12.
Artigo em Inglês | MEDLINE | ID: mdl-31729799

RESUMO

Urbanization has caused an increase in favorable habitats for Aedes aegypti (Diptera: Culicidae), given their ability to reproduce in small and often non-degradable artificial water-containers. While much work has been done on Ae. aegypti biology and ecology in urban landscapes, the role of shading on immature stages as an independent factor from temperature, and any possible interactions between these factors, remains unexamined. We assessed how temperature and shading affected egg hatch-rate, larval/pupal mortality, and larval development to adult stage under different factorial temperature (28; 31; 34; 37; 40° C) and shade (0%, 3,100 lux; 40%, 1,860 lux; 75%, 775 lux; 100%, 0 lux) regimes. Hatch-rate was significantly lower at 37° C (57 %), and no eggs hatched at 40° C. There was no significant effect caused by shading on hatchability. Larval and pupal mortality at 37° C was significantly higher (35%) compared to lower temperature groups, while the effects of shading were emergent at low temperatures. Developmental times from hatching to adult emergence were significantly reduced with increasing temperatures and with greater light exposures. The eco-physiological response of Ae. aegypti larvae to temperature and light regimes suggest a photosensitivity previously unstudied in this species.


Assuntos
Aedes/fisiologia , Aedes/crescimento & desenvolvimento , Aedes/efeitos da radiação , Animais , Temperatura Baixa , Ecologia , Ecossistema , Feminino , Larva , Luz , Mortalidade , Óvulo , Pupa , Temperatura , Água
8.
Parasit Vectors ; 12(1): 524, 2019 Nov 06.
Artigo em Inglês | MEDLINE | ID: mdl-31694685

RESUMO

BACKGROUND: Aedes koreicus was detected in northern Italy for the first time in 2011, and it is now well established in several areas as a new invasive mosquito species. Data regarding the influence of temperature on mosquito survival and development are not available yet for this species. METHODS: We experimentally investigated the influence of different constant rearing temperatures (between 4 and 33 °C) on the survival rates and developmental times of different life stages of Ae. koreicus under laboratory conditions. The resulting data were subsequently used to inform a mathematical model reproducing the Ae. koreicus life-cycle calibrated to counts of adult females captured in the field in the autonomous province of Trento (northern Italy) between 2016 and 2018. RESULTS: We found that temperatures above 28 °C are not optimal for the survival of pupae and adults, whereas temperate conditions of 23-28 °C seem to be very favorable, explaining the recent success of Ae. koreicus at establishing into new specific areas. Our results indicate that Ae. koreicus is less adapted to local climatic conditions compared to Ae. albopictus, another invasive species which has been invading the area for the last three decades. Warmer seasons, which are more likely to occur in the future because of climate change, might extend the breeding time and therefore increase the abundance of Ae. koreicus in the study region. CONCLUSIONS: Our findings provide, to our knowledge, the first evidence on how temperature influences the bionomics and dynamics of Ae. koreicus and highlight the need for further studies on the phenology of this species in temperate areas of Europe.


Assuntos
Aedes/crescimento & desenvolvimento , Aedes/efeitos da radiação , Espécies Introduzidas , Dinâmica Populacional , Temperatura , Animais , Ecologia , Feminino , Itália , Modelos Teóricos , Análise de Sobrevida
9.
PLoS Negl Trop Dis ; 13(10): e0007771, 2019 10.
Artigo em Inglês | MEDLINE | ID: mdl-31658265

RESUMO

BACKGROUND: Important arboviral diseases, such as dengue, chikungunya, and Zika virus infections, are transmitted mainly by the Aedes aegypti vector. So far, controlling this vector species with current tools and strategies has not demonstrated sustainable and significant impacts. Our main objective was to evaluate whether open field release of sterile males, produced from combining the sterile insect technique using radiation with the insect incompatible technique through Wolbachia-induced incompatibility (SIT/IIT), could suppress natural populations of Ae. aegypti in semi-rural village settings in Thailand. METHODOLOGY/PRINCIPAL FINDINGS: Irradiated Wolbachia-infected Aedes aegypti males produced by the SIT/IIT approach were completely sterile and were able to compete with the wild fertile ones. Open field release of these sterile males was conducted in an ecologically isolated village in Chachoengsao Province, eastern Thailand. House-to-house visit and media reports resulted in community acceptance and public awareness of the technology. During intervention, approximately 100-200 sterile males were released weekly in each household. After 6 months of sterile male release, a significant reduction (p<0.05) of the mean egg hatch rate (84%) and the mean number of females per household (97.30%) was achieved in the treatment areas when compared to the control ones. CONCLUSIONS/SIGNIFICANCE: Our study represents the first open field release of sterile Ae. aegypti males developed from a combined SIT/IIT approach. Entomological assessment using ovitraps, adult sticky traps, and portable vacuum aspirators confirmed the success in reducing natural populations of Ae. aegypti females in treated areas. Public awareness through media resulted in positive support for practical use of this strategy in wider areas. Further study using a systematic randomized trial is needed to determine whether this approach could have a significant impact on the diseases transmitted by Ae. aegypti vector.


Assuntos
Aedes/fisiologia , Entomologia/métodos , Controle de Mosquitos/métodos , Mosquitos Vetores/fisiologia , População Rural , Aedes/microbiologia , Aedes/efeitos da radiação , Animais , Feminino , Humanos , Infertilidade Masculina , Masculino , Mosquitos Vetores/microbiologia , Mosquitos Vetores/efeitos da radiação , Dinâmica Populacional , Caracteres Sexuais , Tailândia , Wolbachia/genética , Wolbachia/fisiologia
10.
Parasit Vectors ; 12(1): 435, 2019 Sep 09.
Artigo em Inglês | MEDLINE | ID: mdl-31500662

RESUMO

BACKGROUND: The sterile insect technique (SIT) for use against mosquitoes consists of several steps including the production of the target species in large numbers, the separation of males and females, the sterilization of the males, and the packing, transport and release of the sterile males at the target site. The sterility of the males is the basis of the technique; for this, efficient and standardized irradiation methods are needed to ensure that the required level of sterility is reliably and reproducibly achieved. While several reports have found that certain biological factors, handling methods and varying irradiation procedures can alter the level of induced sterility in insects, few studies exist in which the methodologies are adequately described and discussed for the reproductive sterilization of mosquitoes. Numerous irradiation studies on mosquito pupae have resulted in varying levels of sterility. Therefore, we initiated a series of small-scale experiments to first investigate variable parameters that may influence dose-response in mosquito pupae, and secondly, identify those factors that potentially have a significantly large effect and need further attention. METHODS: In this study, we compiled the results of a series of experiments investigating variable parameters such as pupal age (Aedes aegypti), pupal size (Ae. aegypti), geographical origin of mosquito strains (Ae. aegypti and Ae. albopictus), exposure methods (in wet versus dry conditions, Ae. albopictus) and subsequently in low versus high oxygen environments [submerged in water (low O2 (< 5 %)] and in air [high O2 (~ 21 %)] on the radiosensitivity of male pupae (Ae. aegypti, Ae. albopictus and Anopheles arabiensis). RESULTS: Results indicate that radiosensitvity of Ae. aegypti decreases with increasing pupal age (99% induced sterility in youngest pupae, compared to 93% in oldest pupae), but does not change with differences in pupal size (P = 0.94). Differing geographical origin of the same mosquito species did not result in variations in radiosensitivity in Ae. aegypti pupae [Brazil, Indonesia, France (La Reunion), Thailand] or Ae. albopictus [Italy, France (La Reunion)]. Differences in induced sterility were seen following irradiation of pupae that were in wet versus dry conditions, which led to further tests showing significant radioprotective effects of oxygen depletion during irradiation procedures in three tested mosquito species, as seen in other insects. CONCLUSIONS: These findings infer the necessity to further evaluate significant factors and reassess dose-response for mosquitoes with controlled variables to be able to formulate protocols to achieve reliable and reproducible levels of sterility for application in the frame of the SIT.


Assuntos
Aedes/efeitos da radiação , Anopheles/efeitos da radiação , Mosquitos Vetores/efeitos da radiação , Pupa/efeitos da radiação , Tolerância a Radiação , Irradiação Corporal Total/normas , Animais , Entomologia/normas , Masculino
11.
Acta Trop ; 199: 105110, 2019 Nov.
Artigo em Inglês | MEDLINE | ID: mdl-31351072

RESUMO

Aedes albopictus is a vector of several human viral diseases, including dengue, chikungunya, and Zika. New control method for Aedes albopictus is needed to replace traditional methods such as chemical insecticides which induce resistance, environmental contamination and toxicity to human. In sterile insect technique (SIT), male mosquitoes are sterilized by γ-ray or X-ray irradiation before released. In this study, the relative effectiveness of X-ray irradiation as a mosquito SIT was investigated. Both pupal and adult Aedes albopictus were subjected to different radiation doses and their emergence, survivorship, longevity, induced sterility, and male mating competitiveness were evaluated. Relative to controls, irradiation had no significant effect on emergence and survivorship but significantly reduce adult longevity. Induced sterility were essentially same for both irradiated pupal and adult. At a dose of 40 Gy, 97% and 100% sterility was respectively achieved for males and females. Mating competitiveness was reduced both in adult males and those derived from pupae exposed to 40 Gy. However, populations can be suppressed by increasing the release ratio (sterile: normal). When the release ratio was 7:1, 74% of the wild population could be suppressed. Overall, the results of the present study showed that SIT based on X-Ray irradiation is scientific and feasible to control Aedes albopictus.


Assuntos
Aedes/efeitos da radiação , Infertilidade , Controle de Mosquitos/métodos , Animais , Feminino , Masculino , Pupa/efeitos da radiação , Raios X
12.
PLoS One ; 14(2): e0212520, 2019.
Artigo em Inglês | MEDLINE | ID: mdl-30779779

RESUMO

The sterile insect technique (SIT) may offer a means to control the transmission of mosquito borne diseases. SIT involves the release of male insects that have been sterilized by exposure to ionizing radiation. We determined the effects of different doses of radiation on the survival and reproductive capacity of local strains of Aedes aegypti and Ae. albopictus in southern Mexico. The survival of irradiated pupae was invariably greater than 90% and did not differ significantly in either sex for either species. Irradiation had no significant adverse effects on the flight ability (capacity to fly out of a test device) of male mosquitoes, which consistently exceeded 91% in Ae. aegypti and 96% in Ae. albopictus. The average number of eggs laid per female was significantly reduced in Ae. aegypti at doses of 15 and 30 Gy and no eggs were laid by females that had been exposed to 50 Gy. Similarly, in Ae. albopictus, egg production was reduced at doses of 15 and 25 Gy and was eliminated at 35 Gy. In Ae. aegypti, fertility in males was eliminated at 70 Gy and was eliminated at 30 Gy in females, whereas in Ae. albopictus, the fertility of males that mated with untreated females was almost zero (0.1%) in the 50 Gy treatment and female fertility was eliminated at 35 Gy. Irradiation treatments resulted in reduced ovary length and fewer follicles in both species. The adult median survival time of both species was reduced by irradiation in a dose-dependent manner. However, sterilizing doses of 35 Gy and 50 Gy resulted in little reduction in survival times of males of Ae. albopictus and Ae. aegypti, respectively, indicating that these doses should be suitable for future evaluations of SIT-based control of these species. The results of the present study will be applied to studies of male sexual competitiveness and to stepwise evaluations of the sterile insect technique for population suppression of these vectors in Mexico.


Assuntos
Aedes/efeitos da radiação , Fertilidade/efeitos da radiação , Controle de Mosquitos/métodos , Animais , Infertilidade , Insetos , Masculino , México , Mosquitos Vetores , Doses de Radiação , Radiação Ionizante , Dosagem Radioterapêutica , Comportamento Sexual Animal/efeitos da radiação , Esterilização Reprodutiva/métodos
13.
Parasit Vectors ; 11(Suppl 2): 657, 2018 Dec 24.
Artigo em Inglês | MEDLINE | ID: mdl-30583749

RESUMO

BACKGROUND: The sterile insect technique (SIT), which is based on irradiation-induced sterility, and incompatible insect technique (IIT), which is based on Wolbachia-induced cytoplasmic incompatibility (a kind of male sterility), have been used as alternative methods to reduce mosquito vector populations. Both methods require the release of males to reduce fertile females and suppress the number of natural populations. Different techniques of sex separation to obtain only males have been investigated previously. Our work involves an application of mechanical larval-pupal glass separators to separate Wolbachia-infected Aedes aegypti males from females at the pupal stage, prior to irradiation, and for use in a pilot field release and to assess the quality of males and females before and after sex separation and sterilization. RESULTS: This study was the first to demonstrate the efficiency of mechanical glass separators in separating males for use in an Ae. aegypti suppression trial by a combined SIT/IIT approach. Our results indicated that male and female pupae of Wolbachia-infected Ae. aegypti mosquitoes were significantly different (p < 0.05) in weight, size, and emergence-time, which made it easier for sex separation by this mechanical method. During the pilot field release, the percentage of female contamination was detected to be quite low and significantly different between the first (0.10 ± 0.13) and the second (0.02 ± 0.02) twelve-week period. Both males and females were almost completely sterile after exposure to 70 Gy irradiation dose. We observed that both irradiated Wolbachia-infected males and females survived and lived longer than two weeks, but males could live longer than females (p < 0.05) when they were irradiated at the same irradiation dose. When comparing irradiated mosquitoes with non-irradiated ones, there was no significant difference in longevity and survival-rate between those males, but non-irradiated females lived longer than irradiated ones (p < 0.05). CONCLUSION: Mechanical sex separation by using a larval-pupal glass separator was practically applied to obtain only males for further sterilization and open field release in a pilot population suppression trial of Ae. aegypti in Thailand. Female contamination was detected to be quite low, and skilled personnel can reduce the risk for female release. The irradiated Wolbachia-infected females accidentally released were found to be completely sterile, with shorter life span than males.


Assuntos
Aedes/fisiologia , Controle de Mosquitos/métodos , Mosquitos Vetores/fisiologia , Wolbachia/fisiologia , Aedes/microbiologia , Aedes/efeitos da radiação , Animais , Feminino , Infertilidade Masculina , Longevidade , Masculino , Mosquitos Vetores/microbiologia , Mosquitos Vetores/efeitos da radiação , Projetos Piloto , Controle da População , Pupa , Caracteres Sexuais , Análise para Determinação do Sexo , Tailândia
14.
Parasit Vectors ; 11(1): 603, 2018 Nov 21.
Artigo em Inglês | MEDLINE | ID: mdl-30463624

RESUMO

BACKGROUND: To ensure the success of a mosquito control programme that integrates the sterile insect technique (SIT), it is highly desirable to release sterile males with a maximal lifespan to increase release effectiveness. Understanding sterile male survival under field conditions is thus critical for determining the number of males to be released. Our study aimed to investigate the effect of mass rearing, irradiation, chilling, packing and release time on irradiated male mosquito longevity. METHODS: Anopheles arabiensis and Aedes aegypti immature stages were mass-reared using a rack and tray system. Batches of 50 males irradiated at the pupal stage were immobilised, packed into canisters and chilled for 6 hours at 6 °C. Mosquitoes were then transferred either in the early morning or early evening into climate chambers set to simulate the weather conditions, typical of the beginning of the rainy season in Khartoum, Sudan and Juazeiro, Brazil for An. arabiensis and Ae. aegypti, respectively. The longevity of experimental males was assessed and compared to mass-reared control males subjected either to simulated field or laboratory conditions. RESULTS: The combined irradiation, chilling and packing treatments significantly reduced the longevity of both An. arabiensis and Ae. aegypti under simulated field conditions (P < 0.001). However, packing alone did not significantly reduce longevity of Ae. aegypti (P = 0.38) but did in An. arabiensis (P < 0.001). Overall, the longevity of mass reared, irradiated and packed males was significantly reduced, with the median survival time (days) lower following an early morning introduction (4.62 ± 0.20) compared to an evening (7.34 ± 0.35) in An. arabiensis (P < 0.001). However, there was no significant difference in longevity between morning (9.07 ± 0.54) and evening (7.76 ± 0.50) in Ae. aegypti (P = 0.14). CONCLUSIONS: Our study showed that sterile mass-reared males have a reduced lifespan in comparison to laboratory-maintained controls under simulated field conditions, and that An. arabiensis appeared to be more sensitive to the handling process and release time than Ae. aegypti. Longevity and release time are important parameters to be considered for a successful area-wide integrated vector control programme with a SIT component.


Assuntos
Aedes/efeitos da radiação , Anopheles/efeitos da radiação , Longevidade , Aedes/crescimento & desenvolvimento , Aedes/fisiologia , Animais , Anopheles/crescimento & desenvolvimento , Anopheles/fisiologia , Clima , Entomologia/instrumentação , Entomologia/métodos , Umidade , Infertilidade , Masculino , Pupa/efeitos da radiação , Temperatura
15.
PLoS One ; 13(8): e0202236, 2018.
Artigo em Inglês | MEDLINE | ID: mdl-30107004

RESUMO

The control of Aedes albopictus through Sterile Male Releases requires that the most competitive males be mass-reared and sterilized usually with gamma- or X-ray radiation prior to release. Developing an understanding of the impact of irradiation treatment on flight performance in sterile males is very important because any fitness cost may reduce the efficacy of SIT intervention in the field. Here, we examined the role of irradiation exposure and sugar-feeding on daily flight activity and performance of Ae. albopictus males sterilized during pupal stage with gamma-radiation at 35Gray from a Caesium 137 source. We used a previously developed automated video tracking system to monitor the flight activity of different groups of sterile and control non-sterile males over 24 hours in a flight arena. This monitoring took place under controlled laboratory conditions and we wished to quantify the daily flight activity and to highlight any changes due to radiation treatment and nutritional conditions (starved versus sugar fed). Our experimental evidence demonstrated a characteristic diurnal flight activity with a bimodal pattern regardless of the treatment. Precisely, both irradiated and non-irradiated males exhibited two distinct peaks in flight activity in the morning (6-8 a.m.) and late afternoon (4-6 p.m.). Under changing physiological conditions, irradiated males were generally more active over time and flew longer overall distances than control male populations. These results suggest some internal circadian control of the phase relation to the light-dark cycle, with evidence for modification of flight performance by nutritional status. The fact that daily activity patterns are alike in irradiated and control Ae. albopictus males, and that sterile males could display higher flight performance, is in contrast with the hypothesis that irradiation treatment appears to reduce the fitness of male mosquitoes. We discuss the implications of the present study in sterile-male release programs against Ae. albopictus.


Assuntos
Aedes/fisiologia , Aedes/efeitos da radiação , Voo Animal/efeitos da radiação , Controle de Mosquitos/métodos , Mosquitos Vetores/fisiologia , Mosquitos Vetores/efeitos da radiação , Aedes/virologia , Animais , Radioisótopos de Césio , Ritmo Circadiano , Relação Dose-Resposta à Radiação , Fertilidade/efeitos da radiação , Raios gama , Humanos , Masculino , Mosquitos Vetores/virologia , Pupa/efeitos da radiação
16.
Pathog Glob Health ; 112(3): 107-114, 2018 05.
Artigo em Inglês | MEDLINE | ID: mdl-29737236

RESUMO

Arthropod-borne disease outbreaks, facilitated by the introduction of exotic mosquitoes, pose a significant public health threat. Recent chikungunya virus (CHIKV) epidemics in Europe highlight the importance of understanding the vector potential of invading mosquitoes. In this paper we explore the potential of Aedes koreicus, a mosquito new to Europe, to transmit CHIKV. Mosquitoes were challenged with CHIKV and maintained at two temperatures: 23 °C and a fluctuating temperature. Total CHIKV infection rates at 3, 10 and 14 days post-feeding were low for both temperature treatments (13.8% at 23 °C; 6.2% at fluctuating T). A low percentage (6.1%, n = 65) of mosquitoes maintained at a constant 23 °C showed dissemination of the virus to the wings and legs. Infection of mosquito saliva, with live virus, occurred in 2 mosquitoes. No dissemination was noted under the fluctuating temperature regime. Based on these results we conclude that CHIKV transmission by this species is possible.


Assuntos
Aedes/crescimento & desenvolvimento , Aedes/virologia , Febre de Chikungunya/transmissão , Vírus Chikungunya/isolamento & purificação , Mosquitos Vetores/crescimento & desenvolvimento , Mosquitos Vetores/virologia , Aedes/classificação , Aedes/efeitos da radiação , Animais , Transmissão de Doença Infecciosa , Europa (Continente) , Extremidades/virologia , Mosquitos Vetores/efeitos da radiação , Saliva/virologia , Temperatura , Asas de Animais/virologia
17.
Parasit Vectors ; 11(1): 212, 2018 03 27.
Artigo em Inglês | MEDLINE | ID: mdl-29587850

RESUMO

BACKGROUND: In Switzerland, the invasive Asian tiger mosquito, Aedes albopictus, is firmly established in the Canton of Ticino, south of the Alps. According to a large-scale distribution model developed in 2013, suitable climatic conditions for the establishment of Ae. albopictus north of the Alps are found in Basel and Geneva while Zurich appears to be characterized by winters currently being too cold for survival of diapausing eggs. However, the spatial resolution of large-scale distribution models might not be sufficient to detect particular climatic conditions existing in urban settings, such as the presence of microclimatic temperatures, which may positively influence the probability of diapausing eggs to overwinter. In order to investigate this, microclimatic monitoring of potential diapausing sites (i.e. catch basins) and external controls was performed in January 2017 in Ticino and within the cities of Basel, Geneva and Zurich. RESULTS: Mean January temperatures in catch basins of Basel, Geneva and Zurich were always higher than the -1 °C temperature threshold previously set for survival probability of diapausing eggs, while mean January temperatures were below -1 °C in several catch basins south of the Alps, where Ae. albopictus eggs currently overwinter. The catch basin absolute January daily minimum temperatures both south and north of the Alps were in general higher than the external control temperatures. Absolute January daily minimum temperatures in catch basins in Basel, Geneva and Zurich were always above -10 °C, indicating that diapausing Ae. albopictus eggs could potentially survive winter nights in urban areas north of the Alps. CONCLUSIONS: The findings confirmed previous conclusions that urban catch basins can provide favourable conditions for overwintering of diapausing eggs compared to more cold-exposed sites. The results confirmed the presence of suitable winter conditions for the establishment of Ae. albopictus in the cities of Basel and Geneva. In addition, the microclimate-scale analysis added new information compared to the previous large-scale prevision model by showing that also the city of Zurich could provide winter conditions suitable for the establishment of Ae. albopictus. This illustrates the importance of the resolution of climate data in using models to predict Ae. albopictus distribution.


Assuntos
Aedes/fisiologia , Aedes/efeitos da radiação , Diapausa de Inseto/efeitos da radiação , Ecossistema , Zigoto/fisiologia , Zigoto/efeitos da radiação , Animais , Cidades , Suíça , Temperatura
18.
Parasit Vectors ; 11(1): 22, 2018 01 08.
Artigo em Inglês | MEDLINE | ID: mdl-29310716

RESUMO

BACKGROUND: Taiwan is geographically located in a region that spans both tropical and subtropical climates (22-25°N and 120-122°E). The Taiwan Centers for Disease Control have found that the ecological habitat of Aedes aegypti appears only south of 23.5°N. Low temperatures may contribute to this particular habitat distribution of Ae. aegypti under the influence of the East Asian winter monsoon. However, the threshold condition related to critically low temperatures remains unclear because of the lack of large-scale spatial studies. This topic warrants further study, particularly through national entomological surveillance and satellite-derived land surface temperature (LST) data. METHODS: We hypothesized that the distribution of Ae. aegypti is highly correlated with the threshold nighttime LST and that a critical low LST limits the survival of Ae. aegypti. A mosquito dataset collected from the Taiwan Centers for Disease Control was utilized in conjunction with image data obtained from the moderate resolution imaging spectroradiometer (MODIS) during 2009-2011. Spatial interpolation and phi coefficient methods were used to analyze the correlation between the distributions of immature forms of Ae. aegypti and threshold LST, which was predicted from MODIS calculations for 348 townships in Taiwan. RESULTS: According to the evaluation of the correlation between estimated nighttime temperatures and the occurrence of Ae. aegypti, winter had the highest peak phi coefficient, and the corresponding estimated threshold temperatures ranged from 13.7 to 14 °C in the ordinary kriging model, which was the optimal interpolation model in terms of the root mean square error. The mean threshold temperature was determined to be 13.8 °C, which is a critical temperature to limit the occurrence of Ae. aegypti. CONCLUSIONS: An LST of 13.8 °C was found to be the critical temperature for Ae. aegypti larvae, which results in the near disappearance of Ae. aegypti during winter in the subtropical regions of Taiwan under the influence of the prevailing East Asian winter monsoon.


Assuntos
Aedes/fisiologia , Aedes/efeitos da radiação , Temperatura Baixa , Exposição Ambiental , Animais , Bioestatística , Entomologia/métodos , Larva/fisiologia , Larva/efeitos da radiação , Análise de Sobrevida , Taiwan
19.
Toxicol Ind Health ; 33(12): 930-937, 2017 Dec.
Artigo em Inglês | MEDLINE | ID: mdl-28992792

RESUMO

The study was undertaken to evaluate gamma radiation-induced DNA damage in Aedes aegypti. The comet assay was employed to demonstrate the extent of DNA damage produced in adult male A. aegypti exposed to seven different doses of gamma radiation, ranging from 1 Gy to 50 Gy. DNA damage was measured as the percentage of comet tail DNA. A significant linear increase in DNA damage was observed in all samples; the extent of damage being proportional to the dose of gamma radiation the organism received, except in those treated with 1 Gy. The highest amount of DNA damage was noticed at 1 h postirradiation, which decreased gradually with time, that is, at 3, 6 and 12 h postirradiation. This may indicate repair of the damaged DNA and/or loss of heavily damaged cells as the postirradiation time increased. The comet assay serves as a sensitive and rapid technique to detect gamma radiation-induced DNA damage in A. aegypti. This could be used as a potential biomarker for environmental risk assessment.


Assuntos
Aedes/genética , Aedes/efeitos da radiação , Dano ao DNA/efeitos da radiação , Raios gama/efeitos adversos , Animais , Ensaio Cometa , DNA/genética , Relação Dose-Resposta à Radiação , Masculino , Testes de Mutagenicidade
20.
PLoS Negl Trop Dis ; 11(9): e0005881, 2017 Sep.
Artigo em Inglês | MEDLINE | ID: mdl-28892483

RESUMO

The capacity of the released sterile males to survive, disperse, compete with wild males and inseminate wild females is an essential prerequisite to be evaluated in any area-wide integrated pest management (AW-IPM) programs including a sterile insect release method. Adequate quality control tests supported by standardized procedures need to be developed to measure these parameters and to identify and correct potential inappropriate rearing or handling methods affecting the overall male quality. In this study, we report results on the creation and validation of the first quality control devices designed to infer the survival and mating capacity of radio-sterilized Aedes albopictus males through the observation of their flight capacity under restricted conditions (flight organ device) and after stress treatment (aspirator device). Results obtained consistently indicate comparable flight capacity and quality parameters between untreated and 35 Gy irradiated males while a negative impact was observed with higher radiation doses at all observation time performed. The male flight capacity registered with the proposed quality control devices can be successfully employed, with different predictive capacities and response time, to infer the adult male quality. These simple and cost-effective tools provide a valuable method to detect and amend potentially sub-standard procedures in the sterile male production line and hence contribute to maintaining optimal quality and field performance of the mosquitoes being released.


Assuntos
Aedes/fisiologia , Controle Biológico de Vetores/normas , Aedes/efeitos da radiação , Animais , Voo Animal/efeitos da radiação , Masculino , Controle Biológico de Vetores/economia , Controle Biológico de Vetores/métodos , Pupa/efeitos da radiação , Controle de Qualidade , Comportamento Sexual Animal
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