Blog post by Senay Yitbarek
What has the working group been doing?
The coinfection group is focused on incorporating vector behavior into multiple pathogen dynamics across plants, animals, and human systems. Our group has been working to identify relevant traits from the empirical literature that can help explain coinfection patterns in vector populations. The vector traits of interest have primarily focused on arthropod vectors including mosquitos, ticks, and aphids. For each vector group (~ 5 member/per group), we have appointed a group leader that is responsible for disseminating progress and updates to the general working group body. Furthermore, we have been working on a general theoretical framework that explores the consequences of vector traits for the epidemiology of vector-borne diseases. A separate working group is currently working on a vector borne model.
Any progress made?
The vector groups have recently completed a literature survey on relevant traits pertaining to coinfection dynamics. In the aphid group, seasonality and life stages have been found to play a key role in transmission events. For instance, the wingless-aphid morphs transmit at higher rates early in the season. Aphid preferences for infected and uninfected plants can also affect transmission efficiency of multiple viruses. In the tick group, we focused on two major species and found that ticks are likely to acquire pathogens at each life stage resulting in higher coinfection rates in adults. However, it takes ticks up to 3 years to complete a life cycle requiring hosts at each stage without which they die. Depending on the specific pathogen involved, seasonality generally increases transmission risk. However, transmission risk varies considerably with some pathogens showing annual stability while others peak during the summer months. In the mosquito group, we have examined the role of vector competence in transmitting arboviruses. While A. aegypti mosquitos are highly susceptible to multiple pathogens, vector competence shows preferential transmission to vertebrae hosts. For instance, A. aegypti mosquitos are highly permissive and competent for mono-infection and coinfection with Zika and Dengue, including co-transmission. However, Zika grows to higher titers and more efficiently infects hosts. Thus, vector competence in mosquitos is a critical component that needs to be accounted for in coinfection dynamics. With this in mind, the modeling group is developing a general coinfection model that incorporates vector traits. We are currently expanding on a classical vector-borne disease model by incorporating multiple pathogens and vector traits such as density, fecundity, searching efficiency, handling time, and life-stages. We will explore the effects of vector traits on the basic reproduction ratio of pathogens.
Future goals of this group?
We plan on submitting a manuscript in the form of a review paper that addresses our current knowledge and challenges in understanding the drivers of vector behavior and their consequences for coinfection dynamics. Several groups leaders from our working group will be attending the Vectorbite conference in Asilomar, California. As part of the workshop training, we hope to utilize the population dynamics database to fit some of the vector parameters to our coinfection model. Following the Vectorbite conference, we will reconvene a meeting on the UC Berkeley campus with several group members.