Research

Research Bio

Rebekah J White (she/her) is an evolutionary biology and genetics PhD researcher in the College of Life and Environmental Sciences at the University of Exeter. Her current project involves exploring the genetic basis of ageing, late-life disease, and lifespan extension in nematode worms, using a range of laboratory-based techniques. Her previous work has included emerging zoonotic diseases and transmissible cancers. Rebekah has a passion for communicating research both to the public and to researchers in other fields through many mediums, including podcasts, social media, public speaking, and interdisciplinary conferences.

Emerging zoonotic diseases originating in mammals: a systematic review of effects of anthropogenic land-use change

Published June 2020 in Mammal Review doi: 10.1111/mam.12201

Zoonotic pathogens and parasites that are transmitted from vertebrates to humans are a major public health risk with high associated global economic costs. The spread of these pathogens and risk of transmission accelerate with recent anthropogenic land-use changes (LUC) such as deforestation, urbanisation, and agricultural intensification, factors that are expected to increase in the future due to human population expansion and increasing demand for resources.

We systematically review the literature on anthropogenic LUC and zoonotic diseases, highlighting the most prominent mammalian reservoirs and pathogens, and identifying avenues for future research. Research into specific animal reservoirs has improved our understanding of how the spread of zoonotic diseases is affected by LUC. The behaviour of hosts can be altered when their habitats are changed, impacting the pathogens they carry and the probability of disease spreading to humans. Understanding this has enabled the identification of factors that alter the risk of emergence (such as virulence, pathogen diversity, and ease of transmission). Yet, many pathogens and impacts of LUC other than urbanisation have been understudied.

Predicting how zoonotic diseases emerge and spread in response to anthropogenic LUC requires more empirical and data synthesis studies that link host ecology and responses with pathogen ecology and disease spread. The link between anthropogenic impacts on the natural environment and the recent COVID-19 pandemic highlights the urgent need to understand how anthropogenic LUC affects the risk of spillover to humans and spread of zoonotic diseases originating in mammals.

For more information, you can find the University of Exeter's article about the paper here.

Rattus norvegicus can spread multiple zoonotic diseases
A monoculture of green crops in the sun a few trees throughout
Deforestation in Asia (Peter Wright)

Evolution and Genetics of a Late-Life Disease in Pristionchus Nematodes

University of Exeter, Sep 2019 - Present

In evolutionary theory, it is generally accepted that senescence (ageing) has no adaptive value to the individual. Yet, in life, there are many examples where senescent traits have evolved, leading to late-life disease and reduced lifespan.

In this research, nematode worms from the Pristionchus genus are used to explore if certain forms of senescence are ultimately a result of weak selection in older individuals, or a by-product of a process that is adaptive earlier in development. Interventions to extend lifespan, such as drugs and dietary restriction, are tested and the genetic basis for lifespan extension in each case explored.

Research into the evolution and genetics of ageing could help answer evolutionary biology questions into why seemingly maladaptive late-life traits frequently persist in lineages.

This work is supported by a Royal Society Enhancement Award to Dr. Cameron Weadick.

A tiny nematode worm under a microscope
A Pristionchus nematode
In the lab

Evolution of Transmissibility in Devil Facial Tumour Disease 2 through classical MHC class I Expression in an Endangered Marsupial, the Tasmanian Devil

University of Southampton, Jan 2019 - Aug 2019

Transmissible cancers the Tasmanian Devil (Sarcophilus harrisii) pose a huge threat to the population. There are two genetically distinct contagious cancers found in this species, Devil Facial Tumour Disease (DFT1) and Devil Facial Tumour Disease 2 (DFT2). Research into immunity gene loci have been integral to our understanding of how these cancers are able to spread and proliferate, especially in regard to the expression of classical MHC class I molecules. DFT1 is able to evade the immune system and achieve transmissibility as it has evolved classical MHC class I loss. Alternatively, DFT2 still expresses these molecules, mimicking that of the host’s antigen presenting cells. Due to the specificity of this method of immune escape, this second cancer is only found in hosts from a sub-population residing on an isolated peninsula.

Previous studies have suggested DFT2 may also be evolving classical MHC class I loss, which likely has higher adaptive value, meaning it will lose this restriction and be able to spread as relentlessly as DFT1. In this study, immunohistochemical staining of DFT2 biopsies from naturally infected male Tasmanian Devils has indicated the presence of MHC class I negativity in more recent biopsies and intratumour heterogeneity. I have also designed and optimised a new primer pair to allow more informative sequencing of Saha-UA/-UB/-UC. This will allow future researchers to identify mutations and better understand the evolutionary patterns of classical MHC class I-associated immune evasion, with the ultimate goal of conserving the species.

Healthy Tasmanian Devil

Pilot Investigation into the Relationship between Body Size and Sea Entry in a Vulnerable Reptile, the Marine Iguana

University of Southampton, Sep 2018

The Galapagos Islands provide a habitat for many unusual endemic species, including the Marine Iguanas (Amblyrhynchus cristatus), which are the only species of lizard to take to the sea. This is necessary for algae foraging in the intertidal zone. However, in a trade off, the cool sea lowers their body temperature. If an iguana enters the sea at a higher tide, their foraging time is maximised, but they must swim for a longer duration to reach the algae, meaning they spend more time in the cool water.

Previous studies have found that lizards with a smaller body size lose heat more rapidly, limiting their foraging time, yet there is evidence of larger iguanas opting to spend longer on land to maximise their rewarming time. These contradicting ideas have not been studied before in this species. Therefore, this pilot study evaluates potential research methods and provides baseline results, allowing further research to examine the relationship between Marine Iguana body size and the time of entering the sea, corresponding to the tide level.

Two Marine Iguanas and orange Sally Lightfoot crabs at the bottom of a jetty, looking out into a calm blue sea
My view whilst conducting the Marine Iguana study. Two medium-sized iguanas consider taking to the ocean, while Sally Lightfoot crabs scuttle around nearby.
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