How mosquitoes determine which individuals to bite has important epidemiological consequences. This choice is not random; most mosquitoes specialize in one or a few vertebrate host species, and some ...individuals in a host population are preferred over others. Mosquitoes will also blood feed from other hosts when their preferred is no longer abundant, but the mechanisms mediating these shifts between hosts, and preferences for certain individuals within a host species, remain unclear. Here, we show that olfactory learning may contribute to Aedes aegypti mosquito biting preferences and host shifts. Training and testing to scents of humans and other host species showed that mosquitoes can aversively learn the scent of specific humans and single odorants and learn to avoid the scent of rats (but not chickens). Using pharmacological interventions, RNAi, and CRISPR gene editing, we found that modification of the dopamine-1 receptor suppressed their learning abilities. We further show through combined electrophysiological and behavioral recordings from tethered flying mosquitoes that these odors evoke changes in both behavior and antennal lobe (AL) neuronal responses and that dopamine strongly modulates odor-evoked responses in AL neurons. Not only do these results provide direct experimental evidence that olfactory learning in mosquitoes can play an epidemiological role, but collectively, they also provide neuroanatomical and functional demonstration of the role of dopamine in mediating this learning-induced plasticity, for the first time in a disease vector insect.
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•Aversive learning by mosquitoes suppresses responses to human hosts•Mosquitoes can learn the association between mechanical shock and certain odorants•CRISPR/Cas9 modification of the dopamine-1 receptor prevents learning•Dopamine causes heterogeneous modulation of antennal lobe neurons
Mosquitoes show an ability to avoid defensive hosts, but the mechanisms mediating these shifts in host preferences are unclear. Vinauger et al. show that Aedes aegypti mosquitoes rapidly learn host odors and that learning is dependent on the dopamine-1 receptor. Understanding the mechanisms of learning may provide new tools for mosquito control.
Agricultural lands are integrated into and interact with natural areas. Such is the case of Emek HaMa'ayanot, northern Israel, comprising a springs-rich area characterized by multiple land-uses, ...including spring-water-based aquaculture, recreational springs, and nature reserves. Aquacultural farms suffer from pest snails that carry fish disease; in the study region, these species are invasive (Thiara scabra, Tarebia granifera, Pseudosuccinea columella) and outbreak endemic (Melanoides tuberculata). Previous snail control efforts have focused on individual fishponds without considering management on larger environmental scales in the waterways from the source springs to the fish farms. To broaden our understanding of the status of the pest snail problem in the study area prior to suggesting environmental managerial solutions, we quantified changes in the community composition of snail species along the springs-to-fishponds gradients in a spatially explicit system. We found a remarkable increase in pest snail abundances along these gradients, indicating that pest snails might be invading upstream towards the springs. There were always nearly 100% pest snails in the endpoint sites for water tracks that ended in fishponds. Moreover, pest snails dominated the site when it was used as a fishpond, even though the site was also a spring. In contrast, in a water track that does not end in a fish farm, the relative abundances of non-pest snail species was similar between the source spring and the downstream endpoint, in spite of an increase in pest snail abundance at a midpoint site. These results suggest that invasive pest snails are actively moving upstream and that the fishponds have a marked upstream effect on the ability of non-pest snails to resist pest species invasions. We suggest further investigation of possible strategies for biocontrol of the observed invasion of the snails into natural areas as a basis for environmental management efforts. Finally, the observations made during this study could have practical global implications for snail management in aquaculture and agriculture, and for the control of snails and snail vectors implicated in animal and human diseases.
•Fishponds modified snail community composition upstream on the water gradient.•Non-pest snails dominated water sources, and pest snails dominated fishponds.•The relative abundance of pest snails increased gradually toward fishponds.•Possible active invasion of pest snail upstream.•Recommendations for snail control in waterways in pest-dominated areas.
Rapid adaptation in response to novel environments can facilitate species invasions and range expansions. Understanding how invasive disease vectors rapidly evolve to novel conditions—particularly at ...the edge of its non‐native range—has important implications for mitigating the prevalence and spread of disease.
Here, we evaluate the role of local adaptation in overwintering capability of the Asian tiger mosquito, Aedes albopictus. This species invaded the Southern United States in the 1980s and rapidly spread northward into novel climate compared to its native range. Photoperiodically induced egg diapause is a key trait contributing to the establishment and spread of Ae. albopictus in temperate latitudes, and diapause incidence rapidly developed a cline along a latitudinal gradient in the United States shortly after its initial invasion. However, variation in overwintering survival of diapause‐induced eggs along this gradient is not known, but is critical to the fitness‐related role of diapause evolution in the establishment of Ae. albopictus in its northern US range.
Using reciprocal transplants, we detected local adaptation in overwinter survival of diapausing Aedes albopictus eggs. In northern range‐edge winters, eggs produced by range‐edge individuals survived better than those produced by range‐core individuals. Diapause eggs from range‐edge and range‐core locations survived equally well in range‐core winters, and no eggs survived a winter beyond the current northern range limit in the United States.
Synthesis and applications. These results demonstrate rapid (~3 decades) local adaptation of egg diapause, a key trait facilitating overwinter survival and range expansion for the invasive Asian tiger mosquito. In light of these results, control efforts could shift from targeting satellite populations to a focus on preventing dispersal into locally adapted, range‐edge locations and to aim removal efforts towards areas surrounding locally adapted populations. Adopting new approaches to target rapidly adapting populations will require large‐scale collaboration among control agencies and research institutions, and should begin in the northern US range to better control Aedes albopictus mosquito populations in the face of rapid adaptation.
•We propose a novel modelling framework to estimate insect dispersal.•We consider time, space and insect survival in one single mathematical equation.•Insect flight range can be computed as function ...of the time.
Dispersal is an important driver for animal population dynamics. Insect dispersal is conventionally assessed by Mark-Release-Recapture (MRR) experiments, whose results are usually analyzed by regression or Bayesian approaches which do not incorporate relevant parameters affecting this behavior, such as time dependence and mortality. Here we present an advanced mathematical-statistical method based on partial differential equations (PDEs) to predict dispersal based on MRR data, taking into consideration time, space, and daily mortality. As a case study, the model is applied to estimate the dispersal of the mosquito vector Aedes albopictus using data from three field MRR experiments. We used a two-dimensional PDE heat equation, a normal bivariate distribution, where we incorporated the survival and capture processes. We developed a stochastic model by specifying a likelihood function, with Poisson distribution, to calibrate the model free parameters, including the diffusion coefficient. We then computed quantities of interested as function of space and time, such as the area travelled in unit time. Results show that the PDE approach allowed to compute time dependent measurement of dispersal. In the case study, the model well reproduces the observed recapture process as 86%, 78% and 84% of the experimental observations lie within the 95% CI of the model predictions in the three releases, respectively. The estimated mean values diffusion coefficient are 1,800 (95% CI: 1,704–1 896), 960 (95% CI: 912- 1 128), 552 (95% CI 432–1 080) m2/day for MRR1, MRR2 and MRR3, respectively. The incorporation of time, space, and daily mortality in a single equation provides a more realistic representation of the dispersal process than conventional Bayesian methods and can be easily adapted to estimate the dispersal of insect species of public health and economic relevance. A more realistic prediction of vector species movement will improve the modelling of diseases spread and the effectiveness of control strategies against vectors and pests.
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After the first confirmed outbreak of
Xylella fastidiosa
in the European Union (EU), associated with an olive disease denoted olive quick decline syndrome, mandatory surveys are now carried out in ...the member States and inspections increased at EU entry points such as ports. Such activities led to the interception of
X. fastidiosa
-infected coffee plants in consignments originating from Central America. Similarly, the geographic expansion of the olive decline epidemic area of the Apulia region (southern Italy) prompted investigations to identify new host plants. Here we report the interception of three novel bacterial sequence types in Italy, based on multi-locus sequence typing, that cluster with different
X. fastidiosa
subspecies, illustrating the risk of the introduction of additional pathogen genetic diversity into Europe. In the epidemic area of Apulia, new foci as well as host plant species positive with
X. fastidiosa
, including cherry, myrtleleaf and rosemary, were found to be all infected with the same sequence type of this bacterium (ST53, or CoDiRO strain). This work highlights the limited knowledge of
X. fastidiosa
phylogenetic and phenotypic diversity, the risk of novel
X. fastidiosa
introductions via contaminated plant material, and corroborates other studies indicating that the Apulia epidemic emerged from a single introduction of this pathogen into the region.
A new species of the genus
Triatoma
Laporte, 1832 (Hemiptera, Reduviidae) is described based on specimens collected in the department of Huehuetenango, Guatemala.
Triatomahuehuetenanguensis
sp. n.
is ...closely related to
T.dimidiata
(Latreille, 1811), with the following main morphological differences: lighter color; smaller overall size, including head length; and width and length of the pronotum. Natural
Trypanosomacruzi
(Chagas, 1909) infection, coupled with its presence in domestic habitats, makes this species a potentially important vector of
Trypanosomacruzi
in Guatemala.
The triatomines are vectors of Trypanosoma cruzi (Chagas, 1909), the etiologic agent of Chagas disease. All species are strictly hematophagous, and the hosts used by vector species are important to ...understand the transmission dynamics of T. cruzi, and eventually, for the development of effective control strategies in endemic countries. In the current review, we gather a comprehensively number of literature reporting triatomine feeding sources, using rigorous targeted search of scientific publications, which includes research papers and reviews to put together the most recent findings of the feeding behavior in triatomines and their applications for vector control of Chagas disease. Our main findings suggest that the main feeding source in triatomines is the human blood (22.75%), T. dimidiata (Latreille, 1811) (Hemiptera: Reduviidae) is the most frequent (13.68%) triatomine species in this type of study, and most of the studies on feeding sources (47.5%) are conducted in the domestic and peri-domestic environment.
Genetically modified (GM) mosquitoes expressing anti-plasmodial effectors propagating through wild mosquito populations by means of gene drive is a promising tool to support current malaria control ...strategies. The process of generating GM mosquitoes involves genetic transformation of mosquitoes from a laboratory colony and, often, interbreeding with other GM lines to cross in auxiliary traits. These mosquito colonies and GM lines thus often have different genetic backgrounds and GM lines are invariably highly inbred, which in conjunction with their independent rearing in the laboratory may translate to differences in their susceptibility to malaria parasite infection and life history traits. Here, we show that laboratory
Anopheles gambiae
colonies and GM lines expressing Cas9 and Cre recombinase vary greatly in their susceptibility to
Plasmodium falciparum
NF54 infection. Therefore, the choice of mosquitoes to be used as a reference when conducting infection or life history trait assays requires careful consideration. To address these issues, we established an experimental pipeline involving genetic crosses and genotyping of mosquitoes reared in shared containers throughout their lifecycle. We used this protocol to examine whether GM lines expressing the antimicrobial peptide (AMP) Scorpine in the mosquito midgut interfere with parasite infection and mosquito survival. We demonstrate that Scorpine expression in the Peritrophin 1 (Aper1) genomic locus reduces both
P. falciparum
sporozoite prevalence and mosquito lifespan; both these phenotypes are likely to be associated with the disturbance of the midgut microbiota homeostasis. These data lead us to conclude that the Aper1-Sco GM line could be used in proof-of-concept experiments aimed at mosquito population replacement, although the impact of its reduced fitness on the spread of the transgene through wild populations requires further investigation.
•Afrotropical Atylotus horse flies are often misidentified morphologically.•COI struggles to distinguish between aftrotropical Atylotus species.•Horse flies transmit disease and must be correctly ...identified.
The Afrotropical fly genus, Atylotus has previously shown little differentiation into species groups using the barcode gene COI. This study analysed all available Atylotus COI sequences from GenBank and BOLD to determine if COI is suitable for delimiting species of this genus. Morphological assessments of the different Afrotropical species were done to determine if these species have been accurately identified in recent publications. The results show that COI does not separate the species of this genus into species clades and these species are often misidentified in the literature. This is of concern as species of this genus are known vectors of pathogens and misidentifications have serious implications for management practices. Additional genes need to be used in future molecular studies to differentiate species.
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