VBiTE 2017 Working Groups

VectorBiTE 2017 working groups:

1. Open-access vector science: Data acquisition and use

Proposed activities/objectives:

1) WRITE: Follow up from the American Mosquito Control Association meeting. Write an opinion piece on the pros and cons of data sharing.
2) WORK: Getting data online: Some group members have significant pots of data and are in various stages of getting deposited. We will work to facilitate this. Other have influence with those who have large pots of data, and we will work to help them free up that data.
3) PLAN: Plan for using NEON project data and samples. Mosquito data from NEON sites across the US are coming online slower than expected, however they have now started coming online. We will develop plans for use of both abundance data and the use of samples generated (including viral
and insecticide resistance screens)

Open or Closed Enrollment?
Open. We propose anyone can join – especially if they can demonstrate they have access to large datasets that they wish to make public and/or have resources to utilize NEON data. No one was excluded from original group – original members not listed did not respond to emails/ said they could not come

2. Environmental Influences Across Stages

Group progress update

During the 2016 VectorBiTE meeting, our group outlined a systematic review article to summarize the existing literature on covariates of the larval environment (e.g., temperature, density, predators, competitors, food quality and availability, water chemistry, habitat type) that may alter key adult vector traits (e.g., survival, growth, longevity, fitness, size, host preferences, insecticide resistance, competence, vectorial capacity). Since our last meeting, we have designed and implemented a literature search strategy to pull relevant papers from Web of Science (>3,500 articles). We then divided these articles amongst group members for screening, with the abstract of each article being screened by two different group members for suitability of inclusion (yes, no, maybe) in our review. We anticipate having to review approximately 300 articles in depth to determine suitability for inclusion. Our current goal is to review these articles between January-June 2017.

Proposed activities

Our objective for the 2017 VectorBiTE meeting is to have an intensive writing retreat with the goal of producing a full first draft of our review paper. We will split into groups of 2-3 people with each group responsible for writing a section of the review article on a specific sub-topic, such as pesticide resistance, water chemistry, or competition. We have developed a “score sheet,” similar to what one would use for a meta-analysis, with which we will document each paper we read this spring, including what factor(s) of the larval environment are manipulated and what adult trait(s) are considered in each paper. Condensing this information prior to the meeting will allow for rapid synthesis of each sub-topic.

Open/closed enrollment: Given that our group has made substantial progress towards producing a review article, we request that enrollment in our working group be closed for this meeting.

3. A meta-analysis of the effect of mosquito body size on life history and vectorial capacity traits

Proposed activities/objectives:

Following the VectorBite meeting in Clearwater last year, we started working on a meta-analysis to explore how variation in vector body size correlates with variation in traits related to vector life history and vectorial capacity (e.g., larval development rate, larval survival, adult longevity, fecundity, biting rates, vector competence and the extrinsic incubation period) and whether these putative relations are consistent across key environmental parameters (e.g., temperature, larval competition, sugar access) and species or genera. While individual studies on vector body size go back decades, this meta-analysis would provide the first formal synthesis of the evidence and potentially facilitate the inclusion of body size as a factor in future vector-borne disease models. To date, we have performed a systematic literature search on the topic, gathered PDFs, and are approximately halfway through screening the literature. Our aim is to have finished the screening step by the time of the workshop and bring together a number of the group members to work on data extraction and analysis, and, if time allows, work on the outline for a manuscript.

Open or Closed Enrollment? 

With a significant amount of work remaining, new members would still be welcomed. We are most interested in adding a graduate student or two to the group, preferably people with prior knowledge of, or an interest in becoming acquainted with formal meta-analytic methods.

4. Assessing the power of rate summation to predict performance in a thermally fluctuating environment

Proposed activities/objectives:

Using a combination of empirical and modeling approaches, we want to assess the power of rate summation to predict how disease transmission will vary in a fluctuating environment (using temperature as an example) across a diversity of organisms, including insect vectors. Rate summation may vary in its capacity to predict trait performance in fluctuating environments across diverse organisms due to variation in body size, which can result in different rates of acclimation to changes in temperature. Researchers involved in this aim will explore the predictive capability of rate summation across a diversity of organisms, and whether rate summation models that are not performing optimally can be rescued by including body size acclimation models that incorporate the appropriate biological lags. (Directed by Courtney Murdock, Erin Mordecai, and Jason Rohr; others involved: Zachary Batz, Cynthia Lord, Marta Shocket, and Jeremy Cohen).
Thus far our group has met and discussed rate summation and where it breaks down, particularly when varying temperatures exceed the critical thermal maximum. In addition to within our group, we have had discussions on this with Van Savage and Matt Thomas. One approach is to incorporate acclimation time as it relates to body size, which Jason and Tony Dell have worked on. Another approach is to incorporate the irreversible effects of exceeding CTmax by including a threshold time spent above CTmax. We agreed to start reviewing the literature, with Courtney focusing on mosquitoes and vectors, Erin focusing on thermal response theory, and Jason focusing on pests and vertebrates, and talking to Tony Dell. In addition to a literature review, Murdock’s group has begun an empirical project in the Anopheles -malaria system that will directly compare a thermal performance curve derived from rate summation on a constant temperature curve for R0 with a curve empirically derived under fluctuating conditions to validate mechanistic models that incorporate rate summation approaches, or highlight the areas where these models need improvement and quantify how they break down. Mordecai’s group has also been validating mechanistic temperature transmission models using rate summation approaches on mosquito and pathogen traits quantified under constant temperature conditions in the arbovirus – Aedes system.

Open or Closed Enrollment? With a significant amount of work remaining, new members would still be welcomed. We are most interested in adding graduate students and post-docs to the group, as well as PIs with systems outside of mosquitoes.

5. Species interactions in transmission (SpIT)

Background At the 2016 RCN, we identified a list of vector interactions and vector traits to study and have started researching the interaction of predation. We have two subgroups currently: a meta-analysis group that works with the whole group, and a small group of modelers who have developed a modeling framework and are modifying it based on group feedback and literature results. The meta-analysis group is leading the efforts to search and screen the literature for predation influence on vector traits (survival, fecundity, development rate, host preference & biting rate (behavior), dispersal, phenology (seasonal /daily), competence, transmission mode, and immunology/resistance/susceptibility). The modelers have developed a general framework model for predation effects on vector-borne disease transmission and completed sensitivity analysis of the model. Parameter values will be extracted from the literature to supply to the model, and we will apply the model to vector systems (mosquito, tick, aphid, triatoma) as case studies. Lastly, our group is working to identify gaps in the literature and suggest areas for future experimentation in vector predation research (including SMASHs). We plan to use the model and our literature search to answer the following specific questions: What evidence is there that vector populations of any stage are regulated by predators? What are the direct and indirect effects of predators on vector traits and transmission? What life history and vector traits determine whether vector population regulation by predators exists? Do these predator prey interactions lead to selection on the vector trait?
Our Proposed 2017 RCN Activities & Objectives 
Activity 1: Bring to meeting a first draft manuscript of a general model framework for predation and vectorborne disease transmission to carry out intensive writing edits on. Review all analyses. The goal is to produce a polished working draft by end of RCN.
Activity 2: Bring to meeting a first draft outline of a meta-analysis study of the literature used to parameterize the predation and vectorborne disease transmission model to carry out intensive writing edits on and check analysis methods. The goal is to produce a polished working draft by end of RCN.
Activity 3: Sketch out model framework for next interaction (among: coinfections (vectored or not), parasitoids / vector pathogen (hosts, non hosts), vector competition, microbiome, endosymbiont/mutualisms, and hosts) and disease transmission.
Activity 4: Design a SMASH to address predation model parameters that were lacking in the literature and that can accommodate not only the general framework but different vector systems (mosquito, tick, triatoma, aphid, etc).
Open/Closed Enrollment: We currently have approximately 10-12 active group members. We are open to new additions.

6. What traits determine host range in bird malaria?
Background. Pathogens infect a wide range of hosts: some are complete specialists, while others infect a diversity of species. Vector-borne diseases also range in the breadth of hosts that are involved in transmission cycles, but little is known about the traits that determine these host ranges. This working group will bring together a theoretical ecologist, experimental evolutionary biologists, and avian specialists to examine the role of specific traits in determining avian Plasmodium host range. We choose avian malaria because its diversity rivals anything that has been found in other vertebrate malaria groups (here are currently around 600 mitochondrial cytochrome b lineages described of avian Plasmodium). Some of these lineages seem to have a limited host range, while others infect dozens of bird species in a wide range of taxons). This diversity has been compiled in a large database (MalAvi).
Proposed objectives for Silwood. We anticipate using the time at Silwood to develop a theoretical framework for the study. Additionally, we will begin to analyze a databases that incorporate host range through MalAvi with respect to pathogen traits (e.g., receptor binding proteins, virulence, replication rate, number of infected red blood cells (RBCs), total RBCs) and vector characteristics (i.e. feeding behavior, lifespan, genera). A RBC database has been curated by CF and vector traits will be in a cleaned database ready for analysis during the Silwood meeting.
Open/Closed Enrollment: New members would be welcome to join the project.

7. Toward a better understanding of EIP

The extrinsic incubation period (EIP) for vector-borne pathogens is an important parameter in
evaluating transmission. Our working group focuses on identifying best practices for consistently
characterizing parasite EIP across systems and studies.
Proposed activities/objectives We propose to use a VectorBiTE RCN meeting to write a
perspective piece wherein we (1) evaluate the current approaches to estimating EIP (2)
develop a framework which would improve our approach to measuring EIP, and (3) compare
transmission (i.e. vectorial capacity) estimates from using different methods to measure EIP
to identify best practices. We expect that in some transmission settings, accounting for
variation in EIP will improve transmission estimates and in other settings, it may do little to
improve our understanding of transmission. We hope to identify these situations and develop
a more coherent view of how to characterize EIP in vector-pathogen systems.
Open or Closed Enrollment? We are open to having additional members join our group.

8. Vector behavior and co-infection dynamics in spatially structured populations

Proposed objectives This working group will examine the effects of spatial structure on co-infection dynamics in host communities and how these processes are mediated by vector behavior. Co-infections are ubiquitous in nature, yet studies of parasite dynamics typically focus on single parasites interacting with single hosts. Co-infection dynamics can alter pathogen dynamics by increasing transmission, host mortality, and virulence. While co-infection dynamics can be mediated by within-host processes, other factors operating at larger spatial scales can influence the occurrence and prevalence of co-infections in host communities. Here, we seek to determine how spatially structured multi-host populations influence the prevalence of vector transmitted pathogens and co- infection rates. The role of vector behavior is especially relevant in our understanding of infectious disease dynamics in both plants and animals. For instance, vector preference can be an important driver of co-infection rates in hosts across spatial scales. Some degree of spatial structure is ubiquitous and this has been shown to influence both ecological and evolutionary dynamics, but we currently lack theoretical understanding on how spatial structure impacts multiple pathogen host interactions.
Proposed activities 
A. Develop theoretical models of spatial structure and co-infections as mediated by vector behavior. Spatial network models:
– Review existing models of co-infection and spatial structure
– Build general spatial co-infection model
– Interrogate model with data from natural field populations
– Identify areas where data is currently lacking
B. Identify key vector traits from the literature to construct and parameterize models
Vector traits: Dispersal/ movement, seasonality, competence, feeding preference, biting rate, age, composition and distribution.
Enrollment: Our membership will be open to new members. We especially encourage women, minorities, and persons with disabilities. All participants are welcome.