Wolbachia Bacteria Research Articles

Wolbachia infected and uninfected mosquito growth model using the Leslie multispecies matrix model

Currently, there is a new strategy for stopping the spread of dengue, namely infecting wild mosquitoes with Wolbachia bacteria. Wolbachia is a bacteria that can lower the rate of infection in a mosquito's body, which lowers the risk of the virus being transmitted when it bites susceptible people. Our aim in this paper is to find the equilibrium points and perform local stability analysis for each equilibrium point of a growth model of uninfected and Wolbachia-infected Aedes aegypti mosquitoes. The growth model of the two types of mosquitoes was modeled using the Leslie multispecies matrix model. We assume that the first species is Wolbachia-uninfected mosquitoes and the second species is Wolbachia-infected mosquitoes. In this study, we obtained four equilibrium points. Then, we obtain asymptotically local stability conditions at the four equilibrium points. Based on these results, this study provides conditions that guarantee that efforts to use Wolbachia can suppress dengue disease.

First Record of Endosymbiotic Wolbachia in the Remarkably Diverse Tribe Dorcadionini (Coleoptera: Cerambycidae)

Species diversity is remarkable especially in Dorcadion genus, which spreads in Europe and the Caucasus. Most members of the genus are incapable of flight, generally isolated, and some are endemic. Therefore, there are many studies on the distribution and diversity of species of Dorcadion. However, there is no study on endosymbiotic bacteria that play a critical role in the ecology, physiology and evolution of arthropods. In this study, endosymbiotic Wolbachia bacteria were investigated in members of D. crux Bilberg, 1817, D. micans micans Thomson, 1867, D. anatolicum Pic, 1900, D. septemlineatum Waltl, 1838 and D. scabricolle Dalman, 1817, collected from six different localities. Studies were performed with the Wspec-F/R primer pair. Two of the five examined species of Dorcadion (D. septemlineatum and D. micans micans) are not infected by Wolbachia. On the other hand, Wolbachia (supergroup B type) with the same consensus sequence was detected in D. anatolicum, D. scabricolle and D. crux. Interestingly, Wolbachia, which was thought to be accidental, was found to be common in males, but unfortunately this could not be explained by the data set obtained. However, considering the variations in Dorcadion species and the evaluations according to them, it can be claimed that there is no ordinary association between this taxon and Wolbachia. We hypothesize that among the possible explanations for the large morphological variability in Dorcadionini is the influence of the maternally inherited endosymbiotic Wolbachia. Therefore, we believe that the data obtained in this manuscript will contribute to studies on Dorcadion diversity and distribution.

New Wolbachia pipientis Genotype Increasing Heat Stress Resistance of Drosophila melanogaster Host Is Characterized by a Large Chromosomal Inversion.

The maternally transmitted endocellular bacteria Wolbachia is a well-known symbiont of insects, demonstrating both negative and positive effects on host fitness. The previously found Wolbachia strain wMelPlus is characterized by a positive effect on the stress-resistance of its host Drosophila melanogaster, under heat stress conditions. This investigation is dedicated to studying the genomic underpinnings of such an effect. We sequenced two closely related Wolbachia strains, wMelPlus and wMelCS112, assembled their complete genomes, and performed comparative genomic analysis engaging available Wolbachia genomes from the wMel and wMelCS groups. Despite the two strains under study sharing very close gene-composition, we discovered a large (>1/6 of total genome) chromosomal inversion in wMelPlus, spanning through the region that includes the area of the inversion earlier found in the wMel group of Wolbachia genotypes. A number of genes in unique inversion blocks of wMelPlus were identified that might be involved in the induction of a stress-resistant phenotype in the host. We hypothesize that such an inversion could rearrange established genetic regulatory-networks, causing the observed effects of such a complex fly phenotype as a modulation of heat stress resistance. Based on our findings, we propose that wMelPlus be distinguished as a separate genotype of the wMelCS group, named wMelCS3.

Wolbachia RNase HI contributes to virus blocking in the mosquito Aedes aegypti

The endosymbiotic bacterium Wolbachia pipientis blocks replication of several arboviruses in transinfected Aedes aegypti mosquitoes. However, the mechanism of virus blocking remains poorly understood. Here, we characterized an RNase HI gene from Wolbachia, which is rapidly induced in response to dengue virus (DENV) infection. Knocking down w RNase HI using antisense RNA in Wolbachia-transinfected mosquito cell lines and A.aegypti mosquitoes led to increased DENV replication. Furthermore, overexpression of wRNase HI, in the absence of Wolbachia, led to reduced replication of a positive sense RNA virus, but had no effect on a negative sense RNA virus, a familiar scenario in Wolbachia-infected cells. Altogether, our results provide compelling evidence for the missing link between early Wolbachia-mediated virus blocking and degradation of viral RNA. These findings and the successful pioneered knockdown of Wolbachia genes using antisense RNA in cell line and mosquitoes enable new ways to manipulate and study the complex endosymbiont-host interactions.

Treatment of Lymphatic Filariasis with Wolbachia Targets

Nematodes are the cause of filariasis. Tissue nematodes as the cause of lymphatic filariasis are 3 species, namely Wuchereria bancrofti, Brugia malayi, Brugia timori.1 Lymphatic filariasis is the second largest cause of long-term disability, namely lymphedema of the extremities (elephantiasis) and hydrocele, especially in the tropics.2 Wolbachia bacteria are found in Onchocercidae, the family of filarial nematodes, including species that cause filarial disease in humans such as lymphatic filariasis and onchocerciasis. The symbiosis of Wolbachia and Onchocercidae shows that Wolbachia bacteria play a role in the treatment of filarial parasitic infections by using antibiotics such as tetracycline, doxycycline or rifampicin causing growth retardation and embryogenesis. 4 The long term use of antibiotics is feared to cause resistance to bacteria. Therefore, it is necessary to use antibiotics with a shorter time.

Treatment of Lymphatic Filariasis with Wolbachia Targets

Nematodes are the cause of filariasis. Tissue nematodes as the cause of lymphatic filariasis are 3 species, namely Wuchereria bancrofti, Brugia malayi, Brugia timori.1 Lymphatic filariasis is the second largest cause of long-term disability, namely lymphedema of the extremities (elephantiasis) and hydrocele, especially in the tropics.2 Wolbachia bacteria are found in Onchocercidae, the family of filarial nematodes, including species that cause filarial disease in humans such as lymphatic filariasis and onchocerciasis. The symbiosis of Wolbachia and Onchocercidae shows that Wolbachia bacteria play a role in the treatment of filarial parasitic infections by using antibiotics such as tetracycline, doxycycline or rifampicin causing growth retardation and embryogenesis. 4 The long term use of antibiotics is feared to cause resistance to bacteria. Therefore, it is necessary to use antibiotics with a shorter time.

Educational intervention for the control of Aedes aegypti with Wolbachia in Yucatan, Mexico

The implementation of new control strategies for Aedes aegypti (Ae. Aegpyti), a vector of dengue, chikungunya, and Zika viruses, requires communities to adopt specific behaviors to achieve the success of these innovations. AimWe evaluated the effect of an educational intervention based on the Precede-Proceed Model (PPM) and the Diffusion of Innovations Theory (DIT) for the control and prevention of diseases transmitted by Ae. aegypti through release of male mosquitoes infected with Wolbachia bacteria in a suburban town in Yucatan, Mexico. Material and methodsFrom July 2019 to February 2020, a quasi-experimental study was carried out through an educational intervention (pre- and post-measurements) using quantitative-qualitative techniques, in a Yucatan suburban town where male mosquitoes with Wolbachia were released for the suppression of Ae. aegypti populations. Eleven educational workshops were attended by heads of household (n = 19) and schoolchildren (n = 11). Other 136 heads of household not attending the workshops received information individually. ResultsThe educational intervention had a significant effect on the mean scores of the contributing and behavioral factors for adoption of innovation (p < 0.05) in the pre- and post-intervention measurements. ConclusionInnovative methods for the control and prevention of diseases related to Aedes aegypti can be strengthened through educational interventions supported by sound methodologies. DescriptorsCommunity health education, Aedes aegypti, Wolbachia, Mexico

Easy and Effective Method for Extracting and Purifying Wolbachia Genomic DNA

A number of methods for extracting the DNA of maternally inherited obligate intracellular bacteria Wolbachia from an insect host and its subsequent purification have been described in previous scholarship. As Wolbachia is present in the hosts' organisms in rather low quantities, these techniques used to be quite labor-intensive. For this paper, we analyzed them in detail, searched for a possibility to simplify and accelerate the protocol, and proposed an easy and effective method for isolating Wolbachia DNA from Drosophila melanogaster with a purity sufficient for genomic sequencing. Our method involves the centrifugation of homogenized flies or just their ovaries, as the most Wolbachia-enriched tissue, followed by the filtration of homogenate and extraction of DNA using a modified version of the Livak buffer protocol. The proportion of Wolbachia DNA in the total DNA was quantified based on the results of sequencing with the use of the Illumina MiSeq platform and a pipeline of bioinformatic analysis. For the two analyzed D. melanogaster lines infected with two different Wolbachia strains, the proportion was at least 68 and 94%, respectively.

Modelling the ecological dynamics of mosquito populations with multiple co-circulating Wolbachia strains

Wolbachia intracellular bacteria successfully reduce the transmissibility of arthropod-borne viruses (arboviruses) when introduced into virus-carrying vectors such as mosquitoes. Despite the progress made by introducing Wolbachia bacteria into the Aedes aegypti wild-type population to control arboviral infections, reports suggest that heat-induced loss-of-Wolbachia-infection as a result of climate change may reverse these gains. Novel, supplemental Wolbachia strains that are more resilient to increased temperatures may circumvent these concerns, and could potentially act synergistically with existing variants. In this article, we model the ecological dynamics among three distinct mosquito (sub)populations: a wild-type population free of any Wolbachia infection; an invading population infected with a particular Wolbachia strain; and a second invading population infected with a distinct Wolbachia strain from that of the first invader. We explore how the range of possible characteristics of each Wolbachia strain impacts mosquito prevalence. Further, we analyse the differential system governing the mosquito populations and the Wolbachia infection dynamics by computing the full set of basic and invasive reproduction numbers and use these to establish stability of identified equilibria. Our results show that releasing mosquitoes with two different strains of Wolbachia did not increase their prevalence, compared with a single-strain Wolbachia-infected mosquito introduction and only delayed Wolbachia dominance.

Multiple invasions, Wolbachia and human-aided transport drive the genetic variability of Aedes albopictus in the Iberian Peninsula

The Asian tiger mosquito, Aedes albopictus, is one of the most invasive species in the world. Native to the tropical forests of Southeast Asia, over the past 30 years it has rapidly spread throughout tropical and temperate regions of the world. Its dramatic expansion has resulted in public health concerns as a consequence of its vector competence for at least 16 viruses. Previous studies showed that Ae. albopictus spread has been facilitated by human-mediated transportation, but much remains unknown about how this has affected its genetic attributes. Here we examined the factors that contributed to shaping the current genetic constitution of Ae. albopictus in the Iberian Peninsula, where the species was first found in 2004, by combining population genetics and Bayesian modelling. We found that both mitochondrial and nuclear DNA markers showed a lack of genetic structure and the presence of worldwide dominant haplotypes, suggesting regular introductions from abroad. Mitochondrial DNA showed little genetic diversity compared to nuclear DNA, likely explained by infection with maternally transmitted bacteria of the genus Wolbachia. Multilevel models revealed that greater mosquito fluxes (estimated from commuting patterns and tiger mosquito population distribution) and spatial proximity between sampling sites were associated with lower nuclear genetic distance, suggesting that rapid short- and medium-distance dispersal is facilitated by humans through vehicular traffic. This study highlights the significant role of human transportation in shaping the genetic attributes of Ae. albopictus and promoting regional gene flow, and underscores the need for a territorially integrated surveillance across scales of this disease-carrying mosquito.

Microbiome comparison of Dermanyssus gallinae populations from different farm rearing systems and the presence of common endosymbiotic bacteria at developmental stages.

The hematophagous arthropod, Dermanyssus gallinae (Poultry red mite, PRM) can cause remarkable economic losses in the poultry industry across the globe. Although overall composition of endosymbiotic bacteria has been shown in previous studies, how farm habitats influence the microbiome remains unclear. In the present study, we compared the bacterial communities of D. gallinae populations collected from the cage and free-range farms using next-generation sequences targeting the V3-V4 hypervariable region of the 16S rRNA gene. The QIIME2 pipeline was followed in bioinformatic analyses. Proteobacteria represented a great majority of the total bacterial community of D. gallinae from both farming systems. More specifically, Bartonella-like bacteria (40.8%) and Candidatus Cardinium (21.5%) were found to be predominant genera in free-range and cage rearing systems, respectively. However, the microbiome variation based on farming systems was not statistically significant. In addition, the presence of the five common endosymbiotic bacteria (Wolbachia, Cardinium, Rickettsiella, Spiroplasma, and Schineria) was screened in different developmental stages of D. gallinae. Cardinium was detected in all developmental stages of D. gallinae. On the other hand, Wolbachia and Rickettsiella were only found in adults/nymphs, but neither in the eggs nor larvae. To our knowledge, this study provides the first microbiome comparison at genus-level in D. gallinae populations collected from different farm habitats and will contribute to the knowledge of the biology of D. gallinae.

Symbiotic Wolbachia bacteria in coccinellid parasitoids: genetic diversity, horizontal transfer, and recombination.

Parasitoids, which constitute about 25% of all insects and attack arthropods of virtually all taxa, are considered the most suitable vectors for horizontal transmission of the symbiotic bacterium Wolbachia among insects. The parasitoids studied in this article develop in the larvae and pupae of ladybirds. For the first time, Wolbachia was found in parasitic wasp species of the genus Homalotylus (Hymenoptera: Encyrtidae) and from the subfamily Tetrastichinae (Hymenoptera: Eulophidae). To characterize the Wolbachia strains, six bacterial housekeeping genes were examined and compared with previously published Wolbachia gene sequences. The same bacterial strains were found in all individuals of each species of parasitic wasps collected in different places and at different times, which indicates the absence of contamination and testifies to the heritability of the symbionts in the studied chalcids. No evidence was found that the parasitic wasps were infected with Wolbachia, identical to the symbionts of their ladybirds hosts. We found one Wolbachia strain, wHom-2, which is a product of bacterial recombination from unrelated insects, including ladybirds. The lack of correspondence between the molecular phylogenies of Wolbachia strains and mitochondrial DNA of their hosts indicates horizontal transfers of Wolbachia among parasitic wasps of the genus Homalotylus and from the subfamily Tetrastichinae.

The filarial and the antibiotics: Single or combination therapy using antibiotics for filariasis.

Filarial infections caused by nematodes are one of the major neglected tropical diseases with public health concern. Although there is significant decrease in microfilariae (mf) prevalence following mass drug administration (IVM/DEC/ALB administration), this is transient, in that there is reported microfilaria repopulation 6-12 months after treatment. Wolbachia bacteria have been recommended as a novel target presenting antibiotic-based treatment for filarial disease. Potency of antibiotics against filarial diseases is undoubtful, however, the duration for treatment remains a hurdle yet to be overcome in filarial disease treatment.

Wolbachia Invasion Dynamics by Integrodifference Equations

Releasing mosquitoes infected with the endosymbiotic bacterium Wolbachia to invade and replace the wild populations can effectively interrupt dengue transmission. Recently, a reasonable discrete competitive non-spatial model was developed and the conditions for the successful invasion of Wolbachia were given. However, Wolbachia propagation is a matter of spatial dynamics. In this paper, we introduce a dispersal kernel and establish integrodifference equations, a class of discrete-time spatial diffusion systems that have recently gained much attention as an important tool for spatial ecology. We analyzed the spatial model by average dispersal success approximation to find the criteria for the successful spread of Wolbachia, and then compared it with the non-spatial model to discuss the effect of spatial parameters.

Distinct effects of three Wolbachia strains on fitness and immune traits in Homona magnanima.

The endosymbiotic bacterium Wolbachia occasionally increases host fitness or manipulates host reproductions to enhance vertical transmission. Multiple Wolbachia strains can coinfect the same host individual, which alters the density as well as phenotypes of the bacteria. However, the effects of Wolbachia coinfection on host fitness remain largely unknown. Here, we examined the effects of three phylogenetically distinct Wolbachia strains, wHm-a, wHm-b, and wHm-c, on host fitness by comparing non-infected, singly infected, and triply infected Homona magnanima lines within a fixed genetic background. By examining the effects of Wolbachia on host longevity, survivorship, and reproduction, we demonstrated that single infection with either wHm-b or wHm-c reduced host reproduction, but the triple infection led to the highest intrinsic growth rate. Susceptibility to the natural pathogens such as viruses and fungi was not different among the lines regardless of Wolbachia infection status. Cellular and humoral immunities were not affected by Wolbachia in females, whereas phenoloxidase activity was suppressed in males of all Wolbachia-infected lines, implying that it was a result of the mother's curse hypothesis or a strategy of Wolbachia to increase their horizontal transmission efficiency. Although how the host's genetic diversity affects the Wolbachia fitness effects is yet unknown, our findings indicated that the effects of Wolbachia are deeply influenced by infection status and that Wolbachia could change symbiotic strategy depending on host sex and transmission route.

Close Kin Dyads Indicate Intergenerational Dispersal and Barriers.

AbstractThe movement of individuals through continuous space is typically constrained by dispersal ability and dispersal barriers. A range of approaches have been developed to investigate these. Kindisperse is a new approach that infers recent intergenerational dispersal (σ) from close kin dyads and appears particularly useful for investigating taxa that are difficult to observe individually. This study, focusing on the mosquito Aedes aegypti, shows how the same close kin data can also be used for barrier detection. We empirically demonstrate this new extension of the method using genome-wide sequence data from 266 Ae. aegypti. First, we use the spatial distribution of full-sib dyads collected within one generation to infer past movements of ovipositing female mosquitoes. These dyads indicated the relative barrier strengths of two roads and performed favorably against alternative genetic methods for detecting barriers. We then use Kindisperse to quantify recent intergenerational dispersal (-197.1 m generation-1/2) from the difference in variance between the sib and the first cousin spatial distributions and, from this, estimate effective population density (-4,864 km-2). Dispersal estimates showed general agreement with those from mark-release-recapture studies. Barriers, σ, ρ, and neighborhood size (331-526) can inform forthcoming releases of dengue-suppressing Wolbachia bacteria into this mosquito population.

Spatio-Temporal Modelling Informing Wolbachia Replacement Releases in a Low Rainfall Climate.

Simple SummaryAedes aegypti is a mosquito that is responsible for spreading viral diseases including dengue fever, Zika, and chikungunya. Disease spread can be reduced by releasing mosquitoes containing bacteria known as Wolbachia, which inhibit transmission. Before such releases, it is important to collect data about where Ae. aegypti occur in urban landscapes and how populations vary over space and time. In this study, we present a pre-release analysis of mosquito populations using ovitraps (traps that provide a substrate for female mosquitoes to lay eggs), in Jeddah, Saudi Arabia. Our study contains a number of important findings. Firstly, we showed that there was no difference in the numbers of eggs laid between basement and non-basement locations. Secondly, we showed that, for some study sites, there was significant spatial structure to populations, meaning that where numbers of eggs were high (or low) they tended to remain high (or low) on average for many hundreds of meters. We also found that when mosquitoes are present in an area during the dry season, they tend to remain into the wet season; however, regions of high egg production could change between seasons. This suggests that in Jeddah’s arid environment, the quality of breeding environments is inconsistent over time.Releases of Aedes aegypti carrying Wolbachia bacteria are known to suppress arbovirus transmission and reduce the incidence of vector-borne diseases. In planning for Wolbachia releases in the arid environment of Jeddah, Saudi Arabia, we collected entomological data with ovitraps across a 7-month period in four locations. Herein, we show that mosquito presence in basements does not differ from that of non-basement areas of buildings. In modelling mosquito presence across the study sites, we found the spatial structure to be statistically significant in one of the four sites, while a significant spatial structure was found for egg production data across three of the four sites. The length scales of the spatial covariance functions fitted to the egg production data ranged from 143 m to 574 m, indicating that high productivity regions can be extensive in size. Rank-correlation analyses indicated that mosquito presence tended to persist from the dry to wet season, but that egg production ranks at locations could reverse. The data suggest that, in Jeddah, the quality of the local environment for breeding can vary over time. The data support the feasibility of dry season releases but with release numbers needing to be flexible depending on local rates of invasion.

Wolbachia wAlbB inhibit dengue and Zika infection in the mosquito Aedes aegypti with an Australian background.

Biological control of mosquito vectors using the endosymbiotic bacteria Wolbachia is an emerging strategy for the management of human arboviral diseases. We recently described the development of a strain of Aedes aegypti infected with the Wolbachia strain wAlbB (referred to as the wAlbB2-F4 strain) through simple backcrossing of wild type Australian mosquitoes with a wAlbB infected Ae. aegypti strain from the USA. Field releases of male wAlbB2-F4 mosquitoes resulted in the successful suppression of wild populations of mosquitoes in the trial sites by exploiting the strain’s Wolbachia-induced cytoplasmic incompatibility. We now demonstrate that the strain is resistant to infection by dengue and Zika viruses and is genetically similar to endemic Queensland populations. There was a fourfold reduction in the proportion of wAlbB2-F4 mosquitoes that became infected following a blood meal containing dengue 2 virus (16.7%) compared to wild type mosquitoes (69.2%) and a 6–7 fold reduction in the proportion of wAlbB2-F4 mosquitoes producing virus in saliva following a blood meal containing an epidemic strain of Zika virus (8.7% in comparison to 58.3% in wild type mosquitoes). Restriction-site Associated DNA (RAD) sequencing revealed that wAlbB2-F4 mosquitoes have > 98% Australian ancestry, confirming the successful introduction of the wAlbB2 infection into the Australian genomic background through backcrossing. Genotypic and phenotypic analyses showed the wAlbB2-F4 strain retains the insecticide susceptible phenotype and genotype of native Australian mosquitoes. We demonstrate that the Wolbachia wAlbB2-F4, in addition to being suitable for population suppression programs, can also be effective in population replacement programs given its inhibition of virus infection in mosquitoes. The ease at which a target mosquito population can be transfected with wAlbB2, while retaining the genotypes and phenotypes of the target population, shows the utility of this strain for controlling the Ae. aegypti mosquitoes and the pathogens they transmit.

Rare Wolbachia genotypes in laboratory Drosophila melanogaster strains.

Symbiotic bacteria of the genus Wolbachia are widespread in Drosophila melanogaster populations. Based on the polymorphism of the Wolbachia genome, the symbionts’ diversity in D. melanogaster is presented by two groups: MEL (wMel, wMel2, wMel3 and wMel4) and CS (wMelCS and wMelCS2). The wMel genotype is predominant in natural D. melanogaster populations and is distributed all over the world. The CS genotypes, on the other hand, are of particular interest because it is unclear how they are maintained in the fruit f ly populations since they should have been eliminated from them due to their low frequency and genetic drift or been replaced by the wMel genotype. However, this is not what is really observed, which means these genotypes are supported by selection. It is known that the wMelPlus strain of the wMelCS genotype can increase the lifespan of infected f lies at high temperatures. The same genotype also increases the intensity of dopamine metabolism in Drosophila compared to the MEL-group genotypes. In the present study, we searched for the rare Wolbachia wMelCS and wMelCS2 genotypes, as well as for new genotypes in wild-type D. melanogaster strains and in several mutant laboratory strains. The symbiont was found in all populations, in 200 out of 385 wild-type strains and in 83 out of 170 mutant strains. Wolbachia diversity in D. melanogaster wild-type strains was represented by the wMel, wMelCS and wMelCS2 genotypes. More than 90 % of the infected strains carried wMel; 9 %, wMelCS2; and only two strains were found to carry wMelCS. No new Wolbachia genotypes were found. The northernmost point reported for the wMelCS2 genotype was Izhevsk city (Udmurtia, Russia). For the f irst time the wMelCS2 genotype was detected in D. melanogaster from the Sakhalin Island, and wMelCS, in the f lies from Nalchik (the North Caucasus). A comparison of Wolbachia genetic diversity between the wild-type laboratory strains and previously obtained data on mutant laboratory strains demonstrated differences in the frequencies of rare CS genotypes, which were more prevalent in mutant strains, apparently due to the breeding history of these Drosophila strains

Estimating the effect of the wMel release programme on the incidence of dengue and chikungunya in Rio de Janeiro, Brazil: a spatiotemporal modelling study

Introgression of genetic material from species of the insect bacteria Wolbachia into populations of Aedes aegypti mosquitoes has been shown in randomised and non-randomised trials to reduce the incidence of dengue; however, evidence for the real-world effectiveness of large-scale deployments of Wolbachia-infected mosquitoes for arboviral disease control in endemic settings is still scarce. A large Wolbachia (wMel strain) release programme was implemented in 2017 in Rio de Janeiro, Brazil. We aimed to assess the effect of this programme on the incidence of dengue and chikungunya in the city. 67 million wMel-infected mosquitoes were released across 28 489 locations over an area of 86·8 km² in Rio de Janeiro between Aug 29, 2017 and Dec 27, 2019. Following releases, mosquitoes were trapped and the presence of wMel was recorded. In this spatiotemporal modelling study, we assessed the effect of the release programme on the incidence of dengue and chikungunya. We used spatiotemporally explicit mathematical models applied to geocoded dengue cases (N=283 270) from 2010 to 2019 and chikungunya cases (N=57 705) from 2016 to 2019. On average, 32% of mosquitoes collected from the release zones between 1 month and 29 months after the initial release tested positive for wMel. Reduced wMel introgression occurred in locations and seasonal periods in which cases of dengue and chikungunya were historically high, with a decrease to 25% of mosquitoes testing positive for wMel during months in which disease incidence was at its highest. Despite incomplete introgression, we found that the releases were associated with a 38% (95% CI 32-44) reduction in the incidence of dengue and a 10% (4-16) reduction in the incidence of chikungunya. Stable establishment of wMel in the geographically diverse, urban setting of Rio de Janeiro seems to be more complicated than has been observed elsewhere. However, even intermediate levels of wMel seem to reduce the incidence of disease caused by two arboviruses. These findings will help to guide future release programmes. Bill &amp; Melinda Gates Foundation and the European Research Council.