Effects of environment, dietary regime and ageing on the dengue vector microbiota: evidence of a core microbiota throughout Aedes aegypti lifespan

Abstract Mosquito midgut microbiota is a key component of vector competence, as gut bacteria can disturb pathogen development. In this study, we addressed the microbiota composition of Aedes aegypti during its lifespan, under field conditions. We also investigated the possible effects of environment, dietary regime and ageing on the gut community composition. We employed culture independent and dependent approaches to characterise vector microbiota. There was evidence of a lifelong stable core microbiota after mosquitoes were released into an urban settlement, where they presumably fed on a range of vertebrate hosts and carbohydrate sources. This core was formed mainly of bacteria belonging to the genera Pseudomonas, Acinetobacter, Aeromonas and Stenotrophomonas and to the families Oxalobacteraceae, Enterobacteriaceae and Comamonadaceae. We showed that both dietary regime and age were associated with the abundance of some bacterial groups in the Ae. aegypti microbiota. The majority of the bacterial groups we identified have been detected in the midgut of Ae. aegypti from laboratory and wild populations, indicating a possible core microbiota associated with this mosquito species. Our findings suggest that Ae. aegypti harbours a stable bacterial community during its adult life, similar to mosquito populations from distinct geographic areas, which may be further explored for arbovirus biocontrol strategies.

Estimation of Aedes aegypti (Diptera: Culicidae) population size and adult male survival in an urban area in Panama

Traditional mosquito control strategies rely heavily on the use of chemical insecticides. However, concerns about the efficiency of traditional control methods, environmental impact and emerging pesticide resistance have highlighted the necessity for developing innovative tools for mosquito control. Some novel strategies, including release of insects carrying a dominant lethal gene (RIDL®), rely on the sustained release of modified male mosquitoes and therefore benefit from a thorough understanding of the biology of the male of the species. In this report we present the results of a mark-release-recapture study aimed at: (i) establishing the survival in the field of laboratory-reared, wild-type male Aedes aegypti and (b) estimating the size of the local adult Ae. aegypti population. The study took place in Panama, a country where recent increases in the incidence and severity of dengue cases have prompted health authorities to evaluate alternative strategies for vector control. Results suggest a life expectancy of 2.3 days for released male mosquitoes (confidence interval: 1.78-2.86). Overall, the male mosquito population was estimated at 58 males/ha (range 12-81 males/ha), which can be extrapolated to an average of 0.64 pupae/person for the study area. The practical implications of these results are discussed.

Sequence analysis of ribosomal DNA internal transcribed spacer 2 of sym-patric populations of Anopheles sinensis of different feeding preferences / 中国血吸虫病防治杂志

Objective To investigate the existence of genetic divergence of sympatric populations of Anopheles sinensis of different feeding preferences based on the rDNA-ITS2 sequence differences. Methods A large number of wild anopheles popu-lations were trapped all night by man-baited net and calf-baited net that had been set up between high-density natural villages of An. sinensis populations and vector-breeding sites,from which two groups of An. sinensis were separated by morphological iden-tification and brought back to the lab for conventional breeding. A large closed greenhouse which temperature and humidity was appropriate was selected as research settings of mark-release-recapture methods by female mosquitoes ,in the center of which above An. sinensis populations baited by man and calf and respectively correspondingly marked by red and yellow phosphors were released in together,in each side of which An. sinensis were recaptured simultaneously by man-baited net and calf-baited net. An. sinensis populations trapped by man twice were brought back to the lab and bred with man-blood,correspondingly ones trapped by calf with calf-blood. Man-preferring and calf-preferring strains were screened respectively from An. sinensis which had been baited by man and calf by the mark-release-recapture methods after parent and F1 mosquitoes,and sequencing and aligning of both rDNA-ITS2 were conducted via PCR amplification. Results The recapture ratios of wild parental mosquitoes An. sinensis of man-preferring group by man-baited net and calf-baited net were 54.07%(339/627)and 45.93%(288/627)re-spectively,and ones of calf-preferring group by man-baited net and calf-baited net were 58.01%(409/705)and 41.99%(296/705)respectively. Two groups of parental mosquitoes trended towards selecting the original blood hosts in host-seeking prefer-ence(χ2=19.42,P<0.01). The recapture ratios of F1 mosquitoes An. sinensis of man-preferring group by man-baited net and calf-baited net were 63.43%(765/1 206)and 36.57%(441/1 206),and ones of calf-preferring group by man-baited net and calf-baited net were 68.22%(1 039/1 523)and 31.78%(484/1 523). Two groups of F1 mosquitoes had more significant characteris-tics of selecting the original blood hosts in host-seeking preference(χ2=271.69,P<0.01)and showed the genetic differentia-tion phenomenon,but the results of sequencing and aligning of the rDNA-ITS2 via PCR amplification showed no difference in base sequence between the two strains and both were 469 bp. Conclusions The genetic divergence based on the rDNA-ITS2 se-quence does not happen in An. sinensis sympatric populations of different feeding preferences.

Dispersal and survival of Nyssomyia intermedia and Nyssomyia neivai (Diptera: Psychodidae: Phlebotominae) in a cutaneous leishmaniasis endemic area of the speleological province of the Ribeira Valley, state of São Paulo, Brazil

The dispersal and survival of the phlebotomines Nyssomyia intermedia and Nyssomyia neivai (both implicated as vectors of the cutaneous leishmaniasis agent) in an endemic area was investigated using a capture-mark-release technique in five experiments from August-December 2003 in municipality of Iporanga, state of São Paulo, Brazil. A total of 1,749 males and 1,262 females of Ny. intermedia and 915 males and 411 females of Ny. neivai were marked and released during the five experiments. Recapture attempts were made using automatic light traps, aspiration in natural resting places and domestic animal shelters and Shannon traps. A total of 153 specimens (3.48 percent) were recaptured: 2.59 percent (78/3,011) for Ny. intermedia and 5.35 percent (71/1,326) for Ny. neivai. Both species were recaptured up to 144 h post-release, with the larger part of them recaptured within 48 h. The median dispersion distances for Ny. intermedia and Ny. neivai, respectively, were 109 m and 100 m. The greatest dispersal range of Ny. intermedia was 180 m, while for Ny. neivai one female was recaptured in a pasture at 250 m and another in a pigsty at 520 m, showing a tendency to disperse to more open areas. The daily survival rates calculated based on regressions of the numbers of marked insects recaptured on the six successive days after release were 0.746 for males and 0.575 for females of Ny. intermedia and 0.649 for both sexes of Ny. neivai. The size of the populations in the five months ranged from 8,332-725,085 for Ny. intermedia males, 2,193-104,490 for Ny. intermedia females, 1,687-350,122 for Ny. neivai males and 254-49,705 for Ny. neivai females.

Population Dynamics and Spatial Distribution of Spartocera dentiventris (Berg) (Hemiptera: Coreidae) Adults on Nicotiana tabacum L. (Solanaceae) / Dinâmica Populacional e Distribuição Espacial dos Adultos de Spartocera dentiventris (Berg) (Hemiptera: Coreidae) em Nicotiana tabacum L. (Solanaceae)

Spartocera dentiventris (Berg), o percevejo-cinzento-do-fumo, devido ao seu hábito alimentar sugador, provoca o enrolamento e a murcha das folhas de fumo, causando prejuízos à cultura. O conhecimento da dinâmica populacional é fundamental para o estabelecimento de técnicas mais eficientes de monitoramento e manejo da praga. Com o objetivo de monitorar a colonização, o estabelecimento, o crescimento e a distribuição espacial da população adulta de S. dentiventris, através do método de marcação e recaptura, um cultivo experimental de fumo (Nicotiana tabacum) foi estabelecido em Porto Alegre, RS. Todas as plantas foram inspecionadas três vezes por semana durante o período de agosto de 1999 a abril de 2000, marcando-se 217 indivíduos. Apenas em uma geração os indivíduos sobreviveram até a fase adulta na área. O tamanho populacional, estimado através do método de Fisher-Ford, apresentou um pico de 160 indivíduos. O recrutamento médio estimado foi 5,0 ± 2,67 fêmeas/dia e 6,6 ± 1,73 machos/dia (z = 0,71; gl = 118; P = 0,477). A maioria dos indivíduos concentrou-se na região superior da planta e na face abaxial das folhas. Análise realizada por grupo de seis plantas revelou um padrão agregado de distribuição espacial em 78,4 por cento das ocasiões de amostragem. Os adultos concentraram-se em certos locais da cultura e o tamanho populacional parece ter sido afetado por variações climáticas e predação. Essas observações devem ser consideradas na implementação de medidas de monitoramento e controle da espécie.

Spartocera dentiventris (Berg), the gray-tobacco-bug, feeds on the sap of the plant, inducing leaf wilting and twisting, thus causing economic losses to the tobacco crop. The knowledge on its population dynamics is crucial for the development of efficient techniques for monitoring and managing this species. An experimental tobacco (Nicotiana tabacum) crop was established in Porto Alegre County, South Brazil, aiming to study the colonization, establishment, growth and spatial distribution of the adult S. dentiventris population using the mark-release-recapture method. All plants were inspected at least three times a week. From August 1999 to April 2000, 217 individuals were marked. Only one generation completed development up to the adult phase. Population size estimated by the Fisher-Ford method peaked at ca. 160 individuals. Average recruitment was 5.0 ± 2.67 females per day and 6.6 ± 1.73 males per day (z = 0.71; df = 118; P = 0.477). Most individuals concentrated in the upper part of the plant and on the abaxial face of leaves. Analysis performed in groups of six plants revealed an aggregated pattern of distribution in 78.4 percent of sampling occasions. Individuals concentrated in certain areas of the crop and the population size seemed to be highly susceptible to weather variations and predation. These observations should be taken into account on designing measures for monitoring and control of the species.

Movement pattern of Spartocera dentiventris (Berg) (Hemiptera: Coreidae) in an experimental crop of Nicotiana tabacum L. (Solanaceae)

In the present work we investigated the movement pattern of Spartocera (=Corecoris) dentiventris (Berg) (Hemiptera: Coreidae) adults through the mark-release-recapture method in an experimental tobacco crop (Nicotiana tabacum L., Solanaceae) in Porto Alegre, RS, Brazil. We marked 217 specimens from August 1999 to April 2000. Females moved 2.94 FONT FACE=Symbol>± /FONT> 0.198 times and males 1.46 FONT FACE=Symbol>± /FONT> 0.171 times among host plants. The number of movements per capture was 0.53 FONT FACE=Symbol>± /FONT>0.03 for females and 0.54 FONT FACE=Symbol>± /FONT> 0.06 for males. Newly recruited adults took 12.75 FONT FACE=Symbol>± /FONT> 0.919 days to leave their original plant, females moved 9.87 FONT FACE=Symbol>± /FONT> 0.711 m and males 9.16 FONT FACE=Symbol>± /FONT> 1.29 m in this first movement. We estimate that females move an average of 26.22 m and males 13.89 m during their permanence in the area.

O padrão de movimentação dos adultos de Spartocera (=Corecoris) dentiventris (Berg) (Hemiptera: Coreidae) foi investigado por meio do método de marcação e recaptura, em cultivo experimental de fumo (Nicotiana tabacum L., Solanaceae) em Porto Alegre, RS, Brasil. Foram marcados 217 indivíduos no período de agosto de 1999 a abril de 2000; as fêmeas movimentaram-se 2,94 FONT FACE=Symbol>± /FONT> 0,198 vezes e os machos, 1,46 FONT FACE=Symbol>± /FONT> 0,171 vez entre as plantas hospedeiras. O número de movimentos registrados por recaptura foi de 0,53 FONT FACE=Symbol>± /FONT> 0,03 para fêmeas e de 0,54 FONT FACE=Symbol>± /FONT> 0,06 para machos. Os adultos recém-recrutados levaram 12,75 FONT FACE=Symbol>± /FONT> 0,91 dias para dispersar de sua planta de origem; as fêmeas percorreram 9,87 FONT FACE=Symbol>± /FONT> 0,711 m e os machos, 9,16 FONT FACE=Symbol>± /FONT> 1,29 m nesse primeiro movimento. Estima-se que as fêmeas percorram durante sua permanência na área uma média de 26,22 m, e os machos, 13,89 m.

A mark-release-recapture experiment with Anopheles sinensis in the northern part of Gyeonggi-do, Korea

In order to study the range of flight and feeding activity of Anopheles sinensis, the dispersal experiment was conducted in Paju city, located in the northern part of Gyeonggi-do, Republic of Korea, during the period of 7th to 28th September 1998. Unfed females An. sinensis were collected in cowshed and released after being marked with fluorescent dye at 23:00 hours on the same day. Released female mosquitoes were recaptured everyday during 21 days using light traps, which were set at 10 sites in the cowsheds located 1, 3, 6, 9 and 12 km north-northwest and north-northeast and at 3 sites located 1, 6 and 9 km toward south-west from the release point. In addition, to study the longest flight distance in one night, we set the light traps at 16 and 20 km toward north-northeast from the release site. All the collected mosquitoes were placed on filter papers and observed on UV transilluminator after treatment with one drop of 100% ethanol. Out of 12,773 females of An. sinensis released, 194 marked females mosquitoes were recaptured, giving 1.52% recapture rate. Of 194, 72 mosquitoes (37.1%) were recaptured in light traps from three places set at 1 km from the release point, 57 mosquitoes (29.4%) from two places at 1-3 km, 41 mosquitoes (21.1%) from three places at 3-6 km, 20 mosquitoes (10.3%) from three places at 6-9 km, and 4 mosquitoes (2.1%) from two places at 9-12 km. Since 170 female mosquitoes (87.6%) out of 194 marked mosquitoes were captured within 6 km from the release point, this flight radius represents the main activity area. An sinensis was found to be able to fly at least 12 km during one night.