Effect Of Wolbachia Infection Research Articles

Wolbachia infection negatively impacts Drosophila simulans heat tolerance in a strain- and trait-specific manner.

The susceptibility of insects to rising temperatures has largely been measured by their ability to survive thermal extremes. However, the capacity for maternally inherited endosymbionts to influence insect heat tolerance has been overlooked. Further, while some studies have addressed the impact of heat on traits like fertility, which can decline at temperatures below lethal thermal limits, none have considered the impact of endosymbionts. Here, we assess the impact of three Wolbachia strains (wRi, wAu and wNo) on the survival and fertility of Drosophila simulans exposed to heat stress during development or as adults. The effect of Wolbachia infection on heat tolerance was generally small and trait/strain specific. Only the wNo infection significantly reduced the survival of adult males after a heat shock. When exposed to fluctuating heat stress during development, the wRi and wAu strains reduced egg-to-adult survival but only the wNo infection reduced male fertility. Wolbachia densities of all three strains decreased under developmental heat stress, but reductions occurred at temperatures above those that reduced host fertility. These findings emphasize the necessity to account for endosymbionts and their effect on both survival and fertility when investigating insect responses to heat stress.

Wolbachia hampers the ability to avoid pesticide exposure in Philodromus spiders but does not alter spider’s personality

Wolbachia is known to manipulate a host’s reproduction to promote its own transmission. However, recent studies show that it can influence some behavioural processes in hosts, including personality, and personality-related behaviours. So far, information about the effects of Wolbachia infection on the host’s non-reproductive behaviours is still very limited. Here, we studied the effect of infection by Wolbachia on the personality, locomotion, capture rate, and pesticide exposure of the agriculturally important spider, Philodromus cespitum (Philodromidae). We assayed naturally-infected and uninfected individuals for the two personality traits boldness and aggressiveness. We also recorded the locomotion and capture rate of each spider. All individuals were then tested for pesticide avoidance. We found that Wolbachia-infected (no Cardinium detected) individuals were bolder but less aggressive than uninfected ones. The presence of Wolbachia did not affect personality consistency nor capture rate or locomotion; however, it hampered the ability of the spider to avoid a pesticide-treated surface. We conclude that the alteration of personality may not bring a direct transmission benefit to Wolbachia; however, Wolbachia still causes changes in the spider’s ability to perceive pesticide, which might likely be a side effect rather than a result of manipulation.

Age-Dependent Survival Rates in SIR-SI Dengue Transmission Model and Its Application Considering Human Vaccination and Wolbachia Infection in Mosquitoes

In this paper, an SIR-SI mathematical model in the form of a system of integral equations describing the transmission of dengue disease between human and mosquitoes is proposed and analyzed. Age-dependent functions are used to describe the survival of individuals in human and mosquito populations. The basic reproduction number is derived and its relationship to the equilibria is also explored. The results show that the existence of the positive endemic equilibrium is determined by a threshold number. This threshold number is also the same one that determines the global stability of the equilibrium. The threshold acts like the known basic reproduction number in the counterpart differential equations model and also follows the same rule for the critical level of intervention. Furthermore, as an application, the effect of wolbachia infection is explored, such as how this infection changes the resulting threshold and what the consequence of its presence is in the dynamics of the disease. In this case, the decrease of the mosquitoes’ life expectancy and biting rate are used to reflect the effect of wolbachia bacterial infection on the mosquitoes. In other words, a mosquito which is infected by wolbachia has a lower life expectancy than a normal mosquito. The results, both from mathematical analysis and numerical examples, show that the presence of wolbachia has the potential as a biological control agent to eliminate the dengue in the human population. A comparison of the wolbachia introduction into the mosquito population with the existing strategy, such as vaccination, is also presented.

Effect of Wolbachia Infection and Adult Food on the Sexual Signaling of Males of the Mediterranean Fruit Fly Ceratitis capitata.

Simple SummaryThe Mediterranean fruit fly (medfly) can infest many plant species and survive in different climatic conditions, thus leading to its invasion in new geographical regions and causing great economic losses in fruit production. Insecticides have been the major approach for the suppression of medfly populations for decades. However, concerns regarding insecticide impact on the environment led to the development of environmentally friendly techniques that rely on field releases of sterile males that produce no viable offspring when mated with wild females. One method of male sterilization is their infection with bacteria such as Wolbachia that induce sterility in infected males when crossed with uninfected wild females. The released sterile males should be competitive with wild males for mating with wild females. Therefore, it is important to evaluate the effect of Wolbachia on traits that determine male mating success, such as sexual pheromone signaling, and assess potential ways to improve mating success (i.e., enrichment of male diet with protein). In this study, we demonstrate that Wolbachia infection decreases sexual signaling frequency, but protein-enriched diets cannot counteract this negative effect. Our results contribute to the assessment of Wolbachia infection as an additional tool for population suppression of insect pests.Sexual signaling is a fundamental component of sexual behavior of Ceratitis capitata that highly determines males’ mating success. Nutritional status and age are dominant factors known to affect males’ signaling performance and define the female decision to accept a male as a sexual partner. Wolbachia pipientis, a widespread endosymbiotic bacterium of insects and other arthropods, exerts several biological effects on its hosts. However, the effects of Wolbachia infection on the sexual behavior of medfly and the interaction between Wolbachia infection and adult food remain unexplored. This study was conducted to determine the effects of Wolbachia on sexual signaling of protein-fed and protein-deprived males. Our findings demonstrate that: (a) Wolbachia infection reduced male sexual signaling rates in both food regimes; (b) the negative effect of Wolbachia infection was more pronounced on protein-fed than protein-deprived males, and it was higher at younger ages, indicating that the bacterium regulates male sexual maturity; (c) Wolbachia infection alters the daily pattern of sexual signaling; and (d) protein deprivation bears significant descent on sexual signaling frequency of the uninfected males, whereas no difference was observed for the Wolbachia-infected males. The impact of our findings on the implementation of Incompatible Insect Technique (IIT) or the combined SIT/IIT towards controlling insect pests is discussed.

Taxonomy of hybridizing Colias croceus (Geoffroy, 1785) and Colias erate (Esper, 1805) (Lepidoptera, Pieridae) in light of mitochondrial and nuclear DNA, with occurrence and effects of Wolbachia infection

The lack of reliable characters and the wide color variation make it difficult to distinguish between Colias species. The sequences of mtDNA are often not reliably distinguishing between species of Colias. On the other hand, the genetic divergences within some species are so large that cryptic speciation appears likely to have taken place. Wolbachia are the most widespread endosymbiotic bacteria manipulating the reproduction of their hosts. The screening for the presence of Wolbachia in the sister species Colias croceus and Colias erate showed an infection rate of 100% in the Slovak population. Most specimens of these two species that frequently hybridize are infected by the Wolbachia strain ST141. The role of introgression as the likely reason for DNA barcode sharing is suggested by mitochondrial markers of COI and Control region as well as nuclear genes of CAD, EF1α, GAPDH, IDH, MDH, RPS5 and Wingless. Our findings suggest that the high vertical transmission of Wolbachia infection, fitness advantage and strong cytoplasmic incompatibility have accelerated the spread of Wolbachia and moreover is related to the spread of introgressed mtDNA in the new species after hybridization. Occurrence of many hybrids with intermediate morphological features suggest hybridization to frequently occur between the two species.

Complex effects of environment and Wolbachia infections on the life history of Drosophila melanogaster hosts.

Wolbachia bacteria are common endosymbionts of many arthropods found in gonads and various somatic tissues. They manipulate host reproduction to enhance their transmission and confer complex effects on fitness‐related traits. Some of these effects can serve to increase the survival and transmission efficiency of Wolbachia in the host population. The Wolbachia–Drosophila melanogaster system represents a powerful model to study the evolutionary dynamics of host–microbe interactions and infections. Over the past decades, there has been a replacement of the ancestral wMelCS Wolbachia variant by the more recent wMel variant in worldwide D. melanogaster populations, but the reasons remain unknown. To investigate how environmental change and genetic variation of the symbiont affect host developmental and adult life‐history traits, we compared effects of both Wolbachia variants and uninfected controls in wild‐caught D. melanogaster strains at three developmental temperatures. While Wolbachia did not influence any developmental life‐history traits, we found that both lifespan and fecundity of host females were increased without apparent fitness trade‐offs. Interestingly, wMelCS‐infected flies were more fecund than uninfected and wMel‐infected flies. By contrast, males infected with wMel died sooner, indicating sex‐specific effects of infection that are specific to the Wolbachia variant. Our study uncovered complex temperature‐specific effects of Wolbachia infections, which suggests that symbiont–host interactions in nature are strongly dependent on the genotypes of both partners and the thermal environment.

Effects of Wolbachia infection on fitness-related traits in Drosophila melanogaster

Wolbachia is an intracellular symbiont that infects a large number of arthropod species, ensuring its success in populations by influencing host reproduction. The wMel strain in Drosophila melanogaster does not cause any strong modifications of sexual reproduction. Consequently, it is not clear how the high infection rates of the bacterium in populations of this species are maintained. The wMel strain is classified into two groups of genotypes - wMel and wMelCS. The wMel genotype is ubiquitous in populations, while wMelCS is rare. In this study, we analyzed fitness-related traits in isofemale lines from the unique natural population from Uman (Central Ukraine), in which we observed preservation of the rare wMelCS genotype despite the fluctuations of infection rates between years. We analyzed these effects of Wolbachia genotype and host genetic background on important fitness parameters such as sensitivity to cold and oxidative stress, female fecundity and lifespan. We found that, in the studied population, Wolbachia had an impact on fitness traits only in certain Drosophila genotypes. Positive effects were manifested in the alterations of fecundity, but at the cost of reduced lifespan and resistance to stress. Based on these findings, we conclude that the effect of bacteria on fitness and stress related traits is context-dependent and is modified by the host genotype, at least in the lines established from the Uman population.

Effect of host fruit, temperature and Wolbachia infection on survival and development of Ceratitis capitata immature stages.

The Mediterranean fruit fly, Ceratitis capitata (Diptera: Tephritidae), holds an impressive record of successful invasions promoted by the growth and development of international fruit trade. Hence, survival of immatures within infested fruit that are subjected to various conditions during transportation seems to be a crucial feature that promotes invasion success. Wolbachia pipientis is a common endosymbiont of insects and other arthropods generating several biological effects on its hosts. Existing information report the influence of Wolbachia on the fitness traits of insect host species, including the Mediterranean fruit fly. However, little is known regarding effects of Wolbachia infection on immature development in different host fruits and temperatures. This study was conducted to determine the development and survival of immature stages of four different Mediterranean fruit fly populations, either infected or uninfected with Wolbachia, in two hosts (apples, bitter oranges) under three constant temperatures (15, 25 and 30°C), constant relative humidity (45-55 ± 5%), and a photoperiod of 14L:10D. Our findings demonstrate both differential response of two fruit fly lines to Wolbachia infection and differential effects of the two Wolbachia strains on the same Mediterranean fruit fly line. Larva-to-pupa and larva-to-adult survival followed similar patterns and varied a lot among the four medfly populations, the two host fruits and the different temperatures. Pupation rates and larval developmental time were higher for larvae implanted in apples compared to bitter oranges. The survival rates of wildish medflies were higher than those of the laboratory adapted ones, particularly in bitter oranges. The Wolbachia infected medflies, expressed lower survival rates and higher developmental times, especially the wCer4 infected line. High temperatures constrained immature development and were lethal for the Wolbachia infected wCer4 medfly line. Lower temperatures inferred longer developmental times to immature stages of all medfly populations tested, in both host fruits. Implications on the ecology and survival of the fly in nature are discussed.

The effect of the endosymbiont Wolbachia on the behavior of insect hosts.

As one of the most successful intracellular symbiotic bacteria, Wolbachia can infect many arthropods and nematodes. Wolbachia infection usually affects the reproduction of their hosts to promote their own proliferation and transmission. Currently, most of the studies focus on the mechanisms of Wolbachia interactions with host reproduction. However, in addition to distribution in the reproductive tissues, Wolbachia also infect various somatic tissues of their hosts, including the brain. This raises the potential that Wolbachia may influence some somatic processes, such as behaviors in their hosts. So far, information about the effects of Wolbachia infection on host behavior is still very limited. The present review presents the current literature on different aspects of the influence of Wolbachia on various behaviors, including sleep, learning and memory, mating, feeding and aggression in their insect hosts. We then highlight ongoing scientific efforts in the field that need addressing to advance this field, which can have significant implications for further developing Wolbachia as environmentally friendly biocontrol agents to control insect‐borne diseases and agricultural pests.

Detection of diverse Wolbachia 16S rRNA sequences at low titers from malaria vectors in Kayin state, Myanmar.

Background : Natural Wolbachia infections in malaria mosquitoes were recently reported in Africa, and negatively correlated with the development of Plasmodium falciparum in the vectors. The occurrence and effects of Wolbachia infections outside Africa have not been described and may have been underestimated. Methods : Mosquitoes were collected by human-landing catch during May and June 2017 in ten villages in Kayin state, Myanmar. Closely related species of malaria vectors were identified with molecular assays. 16S rRNA Wolbachia DNA sequences were detected with quantitative real-time PCR. Results: Low titer of Wolbachia DNA was detected in 13/370 samples in six malaria vector species. Sequences were diverse and different from those described in the African malaria mosquitoes. Conclusion: The detection of Wolbachia DNA in malaria mosquitoes from Kayin state warrants further investigations to understand better the ecology and biology of Anopheles- Wolbachia interactions in Southeast Asia.

Low-density genetically diverse natural Wolbachia infections in malaria vectors in Kayin state, Myanmar

Background: Natural Wolbachia infections in malaria mosquitoes were recently reported in Africa, and negatively correlated with the development of Plasmodium falciparum in the vectors. The occurrence and effects of Wolbachia infections outside Africa have not been described and may have been underestimated. Methods: Mosquitoes were collected by human-landing catch during May and June 2017 in ten villages in Kayin state, Myanmar. Closely related species of malaria vectors were identified with molecular assays. Wolbachia infection rates were assessed with quantitative real-time PCR. Results: Low titer of Wolbachia DNA was detected in 13/370 samples in six malaria vector species. Phylogenetic analysis based on 16S rRNA sequences revealed a high diversity of Wolbachia strains and identified lineages different from those described in the African malaria mosquitoes. Conclusion: These low-density genetically diverse natural Wolbachia infections question the ecology and biology of Wolbachia-Anopheles interactions in Southeast Asia. Their effects on malaria transmission and mosquito vectors are yet to be determined.

Low-density genetically diverse natural Wolbachia infections in malaria vectors in Kayin state, Myanmar

Background: Natural Wolbachia infections in malaria mosquitoes were recently reported in Africa, and negatively correlated with the development of Plasmodium falciparum in the vectors. The occurrence and effects of Wolbachia infections outside Africa have not been described and may have been underestimated. Methods: Mosquitoes were collected by human-landing catch during May and June 2017 in ten villages in Kayin state, Myanmar. Closely related species of malaria vectors were identified with molecular assays. Wolbachia infection rates were assessed with quantitative real-time PCR. Results: Low titer of Wolbachia DNA was detected in 13/370 samples in six malaria vector species. Phylogenetic analysis based on 16S rRNA sequences revealed a high diversity of Wolbachia strains and identified lineages different from those described in the African malaria mosquitoes. Conclusion: These low-density genetically diverse natural Wolbachia infections question the ecology and biology of Wolbachia-Anopheles interactions in Southeast Asia. Their effects on malaria transmission and mosquito vectors are yet to be determined.

Detection of diverse Wolbachia 16S rRNA sequences at low titers from malaria vectors in Kayin state, Myanmar

Background : Natural Wolbachia infections in malaria mosquitoes were recently reported in Africa, and negatively correlated with the development of Plasmodium falciparum in the vectors. The occurrence and effects of Wolbachia infections outside Africa have not been described and may have been underestimated. Methods : Mosquitoes were collected by human-landing catch during May and June 2017 in ten villages in Kayin state, Myanmar. Closely related species of malaria vectors were identified with molecular assays. 16S rRNA Wolbachia DNA sequences were detected with quantitative real-time PCR. Results: Low titer of Wolbachia DNA was detected in 13/370 samples in six malaria vector species. Sequences were diverse and different from those described in the African malaria mosquitoes. Conclusion: The detection of Wolbachia DNA in malaria mosquitoes from Kayin state warrants further investigations to understand better the ecology and biology of Anopheles- Wolbachia interactions in Southeast Asia.

No evidence for an effect of Wolbachia on mtDNA variation and evolution in natural populations of Sesamia inferens (Lepidoptera: Noctuidae)

Wolbachia are widespread maternally-inherited endosymbiotic bacteria that infect numerous arthropods. This study represents a thorough survey of the Wolbachia infection patterns in the pink stem borer, Sesamia inferens (Walker), an important rice pest in China, based on nucleotide comparisons for the surface protein (wsp) and cell division protein (ftsZ) genes. The effects of Wolbachia on mtDNA variation and evolution of S. inferens were also investigated. Although we identified six genetically diverse strains, we found infections to be infrequent, with only 7.8% of hosts infected, and identified geographical differences in infection rates between southern and northern populations. Nucleotide indexes (haplotype diversity (Hd), nucleotide diversity (Π) and number of variable sites (S) of mtDNA in infected populations were not significantly lower or higher than that in the uninfected populations. Furthermore, there was no association between Wolbachia infection status and phylogeny of mtDNA haplotypes. Analysis of molecular variance (AMOVA) showed that significant differentiation mainly existed within groups rather than among the groups. Additionally, using Tajima's D and Fu's F values, the mtDNA genes did not deviate significantly from neutral evolution. Taken together these results indicate that currently there were no effects of Wolbachia infection on host mtDNA variation and evolution in S. inferens.

Natural Wolbachia infections in malaria vectors in Kayin state, Myanmar

Background: Natural Wolbachia infections in malaria mosquitoes were recently reported in Africa, and negatively correlated with the development of Plasmodium falciparum in the vectors. The occurrence and effects of Wolbachia infections outside Africa have not been described and may have been underestimated. Methods: Mosquitoes were collected by human-landing catch during May and June 2017 in ten villages in Kayin state, Myanmar. Closely related species of malaria vectors were identified with molecular assays. Wolbachia infection rates were assessed by quantitative real-time PCR. Results: Malaria vectors were identified in the Funestus, Maculatus and Leucosphyrus Groups. Wolbachia were detected in 6/6 Anopheles species and in 5/10 villages. Mean prevalence of Wolbachia infection was 2.7% (95%CI= [1.3; 4.9]). The median Wolbachia load was seven orders of magnitude less in naturally infected malaria vectors than in artificially infected laboratory-reared Aedes aegypti. Phylogenetic analysis based on 16S rRNA sequences revealed a high diversity of Wolbachia strains and identified lineages different from those described in Africa. Conclusion: Natural Wolbachia infections are common and widespread in malaria vectors in Kayin state, Myanmar. Their effects on Anopheles mosquitoes and malaria transmission is yet to be determined.

Wolbachia Infection Associated with Increased Recombination in Drosophila.

Wolbachia is a maternally-transmitted endosymbiotic bacteria that infects a large diversity of arthropod and nematode hosts. Some strains of Wolbachia are parasitic, manipulating host reproduction to benefit themselves, while other strains of Wolbachia exhibit obligate or facultative mutualisms with their host. The effects of Wolbachia on its host are many, though primarily relate to host immune and reproductive function. Here we test the hypothesis that Wolbachia infection alters the frequency of homologous recombination during meiosis. We use D. melanogaster as a model system, and survey recombination in eight wild-derived Wolbachia-infected (strain wMel) and Wolbachia-uninfected strains, controlling for genotype. We measure recombination in two intervals of the genome. Our results indicate that Wolbachia infection is associated with increased recombination in one genomic interval and not the other. The effect of Wolbachia infection on recombination is thus heterogenous across the genome. Our data also indicate a reproductive benefit of Wolbachia infection; infected females show higher fecundity than their uninfected genotypic controls. Given the prevalence of Wolbachia infection in natural populations, our findings suggest that Wolbachia infection is likely to contribute to recombination rate and fecundity variation among individuals in nature.

Effects of Wolbachia infection on the postmating response in Drosophila melanogaster

The series of stereotypical physiological and behavioral changes that female insects exhibit after mating are called postmating responses (PMR). Wolbachia are widespread intracellular bacteria that are well known for their ability to manipulate the host’s reproductive behavior to facilitate their own maternal spreading. The effect of Wolbachia infection on insect hosts’ PMR is not well understood. Here, we showed that after mating with male Drosophila melanogaster infected with Wolbachia, the uninfected female showed a significant decrease in egg laying on the first day. Furthermore, both Wolbachia-infected and Wolbachia-uninfected females mated with infected males exhibited reduced feeding frequency, low receptivity to remating, and an extended median life span compared to those mated with uninfected males. To determine how Wolbachia triggered these alterations, we detected the influence of Wolbachia infection on the expression of some genes encoding seminal fluid proteins (Sfps) in D. melanogaster. These seminal fluid proteins are known to contribute to PMR upon transfer to females during copulation. We found that Acp26Aa, CG1656, and CG42474 were significantly downregulated in Wolbachia-infected males, whereas SP, CG1652, CG9997, and CG17575 showed no significant difference between Wolbachia-infected and Wolbachia-uninfected males. These results suggest that by decreasing the expression of some Sfps in the male hosts, Wolbachia may modulate sexual conflicts of their insect hosts in a way favoring females, thus benefit their own transmission through host populations. This study provides new insights into the host-endosymbiont interaction, which may support the application of endosymbionts for the control of pests and disease vectors. Wolbachia are among the most successful intracellular bacteria that can infect many insect species as well as filarial nematodes. Wolbachia infect host reproductive tissues and are best known for manipulating host reproductive systems to enhance their transmission through host populations. Mating may result in many physiological and behavioral changes in female insects, which are called postmating responses (PMR). Here, we found that after mating with Wolbachia-infected males, Drosophila melanogaster females showed altered PMR, including decreased feeding frequency, attenuated propensity to remating, and prolonged median survival, when compared to those mated with uninfected males. This could be due to a reduction of seminal fluid proteins induced by Wolbachia infection. These findings may raise new speculation about bacteria–host interactions and the ecological and evolutionary consequences of parasitic infection.

Wolbachia infection alters the relative abundance of resident bacteria in adult Aedes aegypti mosquitoes, but not larvae.

Insect-symbiont interactions are known to play key roles in host functions and fitness. The common insect endosymbiont Wolbachia can reduce the ability of several human pathogens, including arboviruses and the malaria parasite, to replicate in insect hosts. Wolbachia does not naturally infect Aedes aegypti, the primary vector of dengue virus, but transinfected Ae.aegypti have antidengue virus properties and are currently being trialled as a dengue biocontrol strategy. Here, we assess the impact of Wolbachia infection of Ae.aegypti on the microbiome of wild mosquito populations (adults and larvae) collected from release sites in Cairns, Australia, by profiling the 16S rRNA gene using next-generation sequencing. Our data indicate that Wolbachia reduces the relative abundance of a large proportion of bacterial taxa in Ae.aegypti adults, that is in accordance with the known pathogen-blocking effects of Wolbachia on a variety of bacteria and viruses. In adults, several of the most abundant bacterial genera were found to undergo significant shifts in relative abundance. However, the genera showing the greatest changes in relative abundance in Wolbachia-infected adults represented a low proportion of the total microbiome. In addition, there was little effect of Wolbachia infection on the relative abundance of bacterial taxa in larvae, or on species diversity (accounting for species richness and evenness together) detected in adults or larvae. These results offer insight into the effects of Wolbachia on the Ae.aegypti microbiome in a native setting, an important consideration for field releases of Wolbachia into the population.

CanWolbachiamodulate the fecundity costs ofPlasmodiumin mosquitoes?

Vertically transmitted parasites (VTPs) such as Wolbachia are expected not only to minimize the damage they inflict on their hosts, but also to protect their hosts against the damaging effects of coinfecting parasites. By modifying the fitness costs of the infection, VTPs can therefore play an important role in the evolution and epidemiology of infectious diseases.Using a natural system, we explore the effects of a Wolbachia-Plasmodium co-infection on mosquito fecundity. While Plasmodium is known to frequently express its virulence by partially castrating its mosquito vectors, the effects of Wolbachia infections on mosquito fecundity are, in contrast, highly variable. Here, we show that Plasmodium drastically decreases the fecundity of mosquitoes by ca. 20%, and we provide the first evidence that this decrease is independent of the parasite's burden. Wolbachia, on the other hand, increases fecundity by roughly 10%, but does not alter the tolerance (fecundity-burden relationship) of mosquitoes to Plasmodium infection.Although Wolbachia-infected mosquitoes fare overall better than uninfected ones, Wolbachia does not confer a sufficiently high reproductive boost to mosquitoes to compensate for the reproductive losses inflicted by Plasmodium. We discuss the potential mechanisms and implications underlying the conflicting effects of these two parasites on mosquito reproduction.

Modelling Wolbachia infection in a sex-structured mosquito population carrying West Nile virus

Wolbachia is possibly the most studied reproductive parasite of arthropod species. It appears to be a promising candidate for biocontrol of some mosquito borne diseases. We begin by developing a sex-structured model for a Wolbachia infected mosquito population. Our model incorporates the key effects of Wolbachia infection including cytoplasmic incompatibility and male killing. We also allow the possibility of reduced reproductive output, incomplete maternal transmission, and different mortality rates for uninfected/infected male/female individuals. We study the existence and local stability of equilibria, including the biologically relevant and interesting boundary equilibria. For some biologically relevant parameter regimes there may be multiple coexistence steady states including, very importantly, a coexistence steady state in which Wolbachia infected individuals dominate. We also extend the model to incorporate West Nile virus (WNv) dynamics, using an SEI modelling approach. Recent evidence suggests that a particular strain of Wolbachia infection significantly reduces WNv replication in Aedes aegypti. We model this via increased time spent in the WNv-exposed compartment for Wolbachia infected female mosquitoes. A basic reproduction number R_0 is computed for the WNv infection. Our results suggest that, if the mosquito population consists mainly of Wolbachia infected individuals, WNv eradication is likely if WNv replication in Wolbachia infected individuals is sufficiently reduced.