Natural Variation in Physicochemical Profiles and Bacterial Communities Associated with Aedes aegypti Breeding Sites and Larvae on Guadeloupe and French Guiana

Aedes aegypti develop in aquatic habitats in which mosquito larvae are exposed to physicochemical elements and microorganisms that may influence their life cycle and their ability to transmit arboviruses. Little is known about the natural bacterial communities associated with A. aegypti or their relation to the biotic and abiotic characteristics of their aquatic habitats. We characterized the physicochemical properties and bacterial microbiota of A. aegypti breeding sites and larvae on Guadeloupe and in French Guiana. In addition, we explored whether geographic location, the type of breeding site and physicochemical parameters influenced the microbiota associated with this mosquito species. We used large-scale 16S rRNA gene sequencing of 160 breeding sites and 147 pools of A. aegypti larvae and recorded 12 physicochemical parameters at the sampled breeding sites. Ordination plots and multiple linear regression were used to assess the influence of environmental factors on the bacterial microbiota of water and larvae. We found territory-specific differences in physicochemical properties (dissolved oxygen, conductivity) and the composition of bacterial communities in A. aegypti breeding sites that influenced the relative abundance of several bacteria genera (e.g., Methylobacterium, Roseoccocus) on the corresponding larvae. A significant fraction of the bacterial communities identified on larvae, dominated by Herbiconiux and Microvirga genera, were consistently enriched in mosquitoes regardless the location. In conclusion, territory-specific differences observed in the biotic and abiotic properties of A. aegypti breeding sites raise concern about the impact of these changes on pathogen transmission by different A. aegypti populations.

Improvement of mosquito identification by MALDI-TOF MS biotyping using protein signatures from two body parts

Background

Matrix-assisted laser desorption/ionization time-of-flight mass spectrometry technology (MALDI-TOF MS) is an innovative tool that has been shown to be effective for the identification of numerous arthropod groups including mosquitoes. A critical step in the implementation of MALDI-TOF MS identification is the creation of spectra databases (DB) for the species of interest. Mosquito legs were the body part most frequently used to create identification DB. However, legs are one of the most fragile mosquito compartments, which can put identification at risk. Here, we assessed whether mosquito thoraxes could also be used as a relevant body part for mosquito species identification using a MALDI-TOF MS biotyping strategy; we propose a double DB query strategy to reinforce identification success.

Methods

Thoraxes and legs from 91 mosquito specimens belonging to seven mosquito species collected in six localities from Guadeloupe, and two laboratory strains, Aedes aegypti BORA and Aedes albopictus Marseille, were dissected and analyzed by MALDI-TOF MS. Molecular identification using cox1 gene sequencing was also conducted on representative specimens to confirm their identification.

Results

MS profiles obtained with both thoraxes and legs were highly compartment-specific, species-specific and species-reproducible, allowing high identification scores (log-score values, LSVs) when queried against the in-house MS reference spectra DB (thorax LSVs range: 2.260–2.783, leg LSVs range: 2.132–2.753).

Conclusions

Both thoraxes and legs could be used for a double DB query in order to reinforce the success and accuracy of MALDI-TOF MS identification.

Electronic supplementary material

The online version of this article (10.1186/s13071-018-3157-1) contains supplementary material, which is available to authorized users.

Screening of natural Wolbachia infection in Aedes aegypti, Aedes taeniorhynchus and Culex quinquefasciatus from Guadeloupe (French West Indies)

Guadeloupe islands are threatened by several mosquito-borne viruses such as Dengue, Chikungunya, Zika and West Nile virus. It appears essential to look for alternative mosquito control methods such as the incompatible insect technique (ITT) aiming at sterilizing wild females by inundative releases of incompatible males. Before considering the implementation of such a strategy, the characterization of genetic diversity of the endocellular bacterium Wolbachia regarding the local mosquito populations is a critical issue. Here, for the first time, we describe the prevalence and diversity of Wolbachia in natural populations of three mosquito species from Guadeloupe: Aedes aegypti, Aedes taeniorhynchus and Culex quinquefasciatus. The detection of Wolbachia in natural Ae. aegypti, Ae. taeniorhynchus and Cx. quinquefasciatus populations was conducted by studying Wolbachia 16S ribosomal RNA gene using a TaqMan quantitative real-time PCR and results were confirmed by conventional PCR and sequencing. In addition, molecular typing of wPip strains in Cx. quinquefasciatus was done by PCR-RFLP. We did not find Wolbachia infection in any of Ae. aegypti and Ae. taeniorhynchus studied populations. Natural Wolbachia infection was detected in Cx. quinquefasciatus with prevalence varying from 79.2% to 95.8%. In addition, no polymorphism was found between the Wolbachia strains infecting Cx. quinquefasciatus specimens, all carrying an infection from the same Wolbachia genetic wPip-I group. These results pave the way for the evaluation of the feasibility of IIT programs to fight against these medically-important mosquito species in Guadeloupe.

Chikungunya virus transmission potential by local Aedes mosquitoes in the Americas and Europe

Background

Chikungunya virus (CHIKV), mainly transmitted in urban areas by the mosquitoes Aedes aegypti and Aedes albopictus, constitutes a major public health problem. In late 2013, CHIKV emerged on Saint-Martin Island in the Caribbean and spread throughout the region reaching more than 40 countries. Thus far, Ae. aegypti mosquitoes have been implicated as the sole vector in the outbreaks, leading to the hypothesis that CHIKV spread could be limited only to regions where this mosquito species is dominant.

Methodology/Principal Findings

We determined the ability of local populations of Ae. aegypti and Ae. albopictus from the Americas and Europe to transmit the CHIKV strain of the Asian genotype isolated from Saint-Martin Island (CHIKV_SM) during the recent epidemic, and an East-Central-South African (ECSA) genotype CHIKV strain isolated from La Réunion Island (CHIKV_LR) as a well-characterized control virus. We also evaluated the effect of temperature on transmission of CHIKV_SM by European Ae. albopictus. We found that (i) Aedes aegypti from Saint-Martin Island transmit CHIKV_SM and CHIKV_LR with similar efficiency, (ii) Ae. aegypti from the Americas display similar transmission efficiency for CHIKV_SM, (iii) American and European populations of the alternative vector species Ae. albopictus were as competent as Ae. aegypti populations with respect to transmission of CHIKV_SM and (iv) exposure of European Ae. albopictus to low temperatures (20°C) significantly reduced the transmission potential for CHIKV_SM.

Conclusions/Significance

CHIKV strains belonging to the ECSA genotype could also have initiated local transmission in the new world. Additionally, the ongoing CHIKV outbreak in the Americas could potentially spread throughout Ae. aegypti- and Ae. albopictus-infested regions of the Americas with possible imported cases of CHIKV to Ae. albopictus-infested regions in Europe. Colder temperatures may decrease the local transmission of CHIKV_SM by European Ae. albopictus, potentially explaining the lack of autochthonous transmission of CHIKV_SM in Europe despite the hundreds of imported CHIKV cases returning from the Caribbean.

More than one million chikungunya cases have been reported in the Americas since October 2013, when the Asian genotype of chikungunya virus (CHIKV) was imported by a traveller returning from Asia. CHIKV is mainly transmitted in urban areas by the domestic mosquitoes Aedes aegypti and Aedes albopictus. In this study, we evaluate the potential for the CHIKV circulating in the Caribbean to initiate outbreaks in Aedes-infested regions of continental America and Europe by assessing the ability of local mosquitoes to experimentally transmit the virus. Mosquitoes were exposed to a blood-meal containing the virus which must overcome several barriers to infect various tissues in the vector before being secreted in the mosquito saliva when biting a host. We found that Ae. aegypti and Ae. albopictus transmitted similarly the virus. When exposing Ae. albopictus from Europe at a temperature of 20°C after infection, we detect a significant drop of CHIKV transmission potential. Our results suggest that the CHIKV outbreak in the Americas could potentially spread throughout Ae. aegypti- and Ae. albopictus-infested regions of the Americas however with a limited risk of spillovers in Ae. albopictus-infested regions in Europe. These data will be useful for adapting vector control strategies and epidemiological surveillance.

The impact of the World Trade Center attack on FDNY firefighter retirement, disabilities, and pension benefits

BACKGROUND

Our goal was to examine the effect of the World Trade Center (WTC) attack and subsequent New York City Fire Department (FDNY) rescue/recovery activities on firefighter retirements. We also analyzed the financial impact associated with the increased number and proportion of service-connected "accidental" disability retirements on the FDNY pension system.

METHODS

A total of 7,763 firefighters retired between 9/11/1994 and 9/10/2008. We compared the total number of retirements and the number and proportion of accidental disability retirements 7 years before and 7 years after the WTC attack. We categorized WTC-related accidental disability retirements by medical cause and worked with the New York City Office of the Actuary to approximate the financial impact by cause.

RESULTS

In the 7 years before 9/11 there were 3,261 retirements, 48% (1,571) of which were accidental disability retirements. In the 7 years after 9/11, there were 4,502 retirements, 66% (2,970) were accidental disability retirements, of which 47% (1,402) were associated with WTC-related injuries or illnesses. After 9/11, the increase in accidental disability retirements was, for the most part, due to respiratory-related illnesses. Additional increases were attributed to psychological-related illnesses and musculoskeletal injuries incurred at the WTC site. Pension benefits associated with WTC-related accidental disability retirements have produced an increased financial burden of over $826 million on the FDNY pension system.

CONCLUSIONS

The WTC attacks affected the health of the FDNY workforce resulting in more post-9/11 retirements than expected, and a larger proportion of these retirees with accidental disability pensions.