UP researchers call for the urgent protection of bat-inhabited caves

University of Pretoria researchers Dr Mariëtte Pretorius and Professor Wanda Markotter have published a study which shows that land around important bat-inhabited caves are changing and that natural habitats are being destroyed. 

Changes to natural habitats are bringing previously unencountered animal populations into contact with humans. This is especially true of bats, which are considered to be significant zoonotic transmission vectors; zoonotic diseases are illnesses that transfer from animals to humans. 

The study also notes that caves and cave-dwelling bats are under-represented in conservation plans. The researchers detailed this shortfall by observing about 50 bat roosts. “The study found an overall 4% decrease in natural woody vegetation (trees) within 5km buffer zones of all roost sites, with a 10% decrease detected at the co-roosting sites alone,” Dr Pretorius says. “As human populations grow, we are requiring more food – we found that agricultural land cover increased the most near roost sites, followed by plantations and urban land cover.”

Dr Pretorius explains that in South Africa, at least two cave-dwelling species are of interest as potential zoonotic hosts: the Natal long-fingered bat (Miniopterus natalensis) and the Egyptian fruit bat (Rousettus aegyptiacus). “This is because of their large population sizes and widespread abundance. Very little information is available about the pressures that humans place on species like bats and specifically around the habitats for their roosts.” 

The researchers also found that the distances of habitats where roosts were found were decreasing as urban areas expanded. “According to the South African National Biodiversity Institute’s ecosystem threat status assessment, which we used in our analyses, 72% of cave roosts fall outside of well-protected ecosystems,” Dr Pretorius says. “As humans encroach on the territories of animals, we are putting ourselves at greater risks of severe pandemics because of how we are changing the use of our land. 

“Our study calls for the urgent and formal protection of bat-inhabited caves to safeguard both bats and humans. Bats are vital to our ecosystem as they are one of nature’s most effective pollinators and seed dispersers. They also help to keep insect populations in balance and they help with our food security.” 

“This study is critical in our understanding of One Health because of the interplay of three facets: the health of animals, humans and the environment,” says Prof Markotter, Head of UP’s Centre for Viral Zoonoses which leads in the One Health initiative to investigate zoonotic diseases. One Health refers to the interaction and intersection of the health of humans, animals and the environment.

Click on the video in the sidebar to learn more about why bats are so important to our ecosystem. For a few interesting facts about bats, click on the infographic. To view pictures of bats from the study, click on the gallery.

Dr Mariette Pretorius and Prof Wanda Markotter

April 17, 2022

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Researchers
  • Dr Mariëtte Pretorius
    Dr Mariëtte Pretorius completed her undergraduate studies, honours degree and MSc in Zoology and Ecology at the University of the Witwatersrand between 2012 and 2017.
    She joined the University of Pretoria (UP) in 2018 when she began her PhD studies with Dr Mark Keith at the Mammal Research Institute. Dr Pretorius completed her PhD, which focused on bat research, in 2020 before embarking on a postdoctoral fellowship with Professor Wanda Markotter at the Centre for Viral Zoonoses in March 2021.

    Dr Pretorius is part of a multidisciplinary research team at the Biosurveillance and Ecology of Emerging Zoonoses group at UP’s Centre for Viral Zoonoses. Their work focuses on virological and ecological surveillance of various bat species. “My work specifically involves determining the effect of the landscape on bat health,” Dr Pretorius explains. “I am looking at how different levels of human influence – such as in urban versus natural areas – affect bats by researching metrics like body mass, ectoparasite loads and pesticide exposure from blood work.”

    She also uses various landscape factors to create hotspot maps of potential zoonotic spillover by determining human-livestock-bat interfaces. She is also focusing on improving and promoting bat conservation in southern Africa.

    Because her research spans both zoonotic and ecological aspects, her postdoctoral work is a collaboration between the Centre for Viral Zoonoses with Prof Markotter and the Mammal Research Institute, with Dr Keith.

    “We have been living through a global pandemic, which likely originated from wildlife,” says Dr Pretorius in reply to why her research matters. “As human populations grow and more natural areas are lost, there is an increased risk of more these events. My work is contributing towards understanding how potential zoonotic spillover from bats could originate, identifying high-risk areas and planning to prevent such future outbreak scenarios.”

    A recent highlight in her career was the publication of her paper, on the land use change around important bat-inhabited caves, in a high-ranking scientific journal. The work is a crucial step towards improving conservation actions for cave-dwelling bats in South Africa. “I also wrote a press article about this work, which led to several radio interviews, creating awareness among the public about the conservation of bats,” Dr Pretorius says. “Raising awareness is a very important part of our jobs as scientists.”

    From a young age, Dr Pretorius was taken by her parents to nature reserves such as the Kruger National Park; this exposure, she says, inspired her passion for the natural world. “I also loved David Attenborough’s shows and learning about animals, so I guess it was easy for me to choose zoology and ecology as a career.”

    She describes herself as having been really lucky to have worked with several great researchers during her academic training. “My honours and MSc supervisor, Prof Neville Pillay, was instrumental in making me the scientist that I am today,” she says. “He has been a mentor and friend since 2016, and his calm nature and relaxed teaching style turned a wide-eyed undergraduate student into a confident scientist.”

    Dr Pretorius hopes that her research will be impactful and useful in improving the relationship between humans, the natural environment and bats. Her research matters, she says, because bats are historically understudied and generally misunderstood. “I hope that my work can inspire more people to notice and appreciate bats for their important roles in our world.”

    Her advice to learners and undergraduate students who may be interested in her field of research is to be realistic about their expectations as a career in this field is not always glamorous. “We work with a lot of animal body fluids,” Dr Pretorius says. Also, it requires determination, hard work, long hours in the field and weeks spent away from home. “But for someone like me, who enjoys the science and working with the animals, it is extremely rewarding and feels more like an adventure than a job,” she adds.

    In her free time, she enjoys reading sci-fi books, doing pencil sketches and attempting wildlife photography.
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  • Professor Wanda Markotter
    Professor Wanda Markotter is a virologist who began her academic career at the University of Pretoria (UP) in 2004 and is currently the Director of its Centre for Viral Zoonoses in the Department of Medical Virology at the University’s Faculty of Health Sciences.

    In January 2016, the DSI-NRF South African Research Chairs (SARChI) Initiative awarded her the Chair in Animal Infectious Diseases (Zoonoses). Prof Markotter has been involved in a transdisciplinary research programme on disease ecology in bat species in South Africa and other African countries since 2005. Her research includes extensive fieldwork that focuses on bats and potential spillover hosts, virological testing, bat biology, ecological investigations and human behaviour studies. The focus is not only to detect viruses but to understand the factors involved in spillover and to develop mitigation strategies. More than 40 postgraduate students have graduated under her supervision, and she has mentored several postdoctoral fellows and emerging researchers.

    Prof Markotter has published more than 70 scientific publications and several book chapters, and regularly contributes to public media forums. Her research is supported by several multi-collaborative international viral surveillance programmes and institutions, including the Global Disease Detection Programme, the Centres for Disease Control and Prevention, and the Defence and Threat Reduction Agency in the USA. She also plays a leading role in several governmental committees, including the National Rabies Advisory Group and the National One Health Forum.

    What got you interested in virology?

    Viruses are not considered alive, and are so small, you cannot see them with the naked eye or even with a normal light microscope. You need a special electron microscope. However, they’re responsible for the world deadliest diseases. It has always fascinated me that an organism so small can infect you without you even knowing it happened. It then uses the infected host’s machinery to amplify and cause damage. To understand their mechanisms of action and how to prevent and treat infections is something I want to understand.

    What’s the most fascinating thing you’ve learnt about bats?

    Bats have adapted to carry deadly viruses without these viruses causing any harm to the animal itself. The “flight as fever” hypothesis states that bats have developed unique mitochondrial and DNA repair pathways – flight leads to higher metabolic rates and higher body temperatures, which the adaptations help the animal to deal with. The same adaptations also assist in controlling viral replication. The higher body temperature simulates a fever that also assists in viral control. Other hosts, like humans, can’t control these viruses when they spillover. However, there isn’t good experimental evidence yet for this theory. More studies on the immune system of bats are now being done, but there is no conclusive evidence on whether they have a unique immune system that assists in controlling these viruses.

    What do think COVID-19 has taught the world?

    We should never be complacent; emerging novel diseases can be introduced into the human population at any time. There are many reasons for this, but most of them have to do with the pressures on the environment. We are causing these introductions by our actions, and I think COVID-19 has taught us to really think about how we should responsibly interact with our environment and animals. We need to prevent spillover. There will be another disease and another opportunity for spillover. To react only when it is already a disease transmitted between humans is too late and extremely costly, both in human lives and economic impact. It requires a holistic approach among scientists, communities, governments and NGOs focused on developing mitigation strategies that are practical for high-risk communities to prevent spillover.

    Many people believe that COVID-19 might be around for quite some time. What does the research around coronaviruses show us?

    Time will tell. COVID-19 is a mild disease among a high majority of people, making it difficult to identify infections. This was different for MERS and SARS, which caused severe disease; infected people were then isolated and the spread prevented. This has led to the theory that COVID-19 could become seasonal, like influenza. Several factors might play a role in this, including how long infected people stay immune. If there is only short immunity, in the absence of a vaccine, it’s more likely that we will see annual outbreaks. It will also depend on the degree to which the weather affects the virus; this will become clearer as some countries approach a different season.

    Was the global spread of COVID-19 something that you anticipated would happen in our lifetime?

    If we look at the history of emerging diseases, it’s something that could have been expected. However, I do not think we anticipated the “when”, “how” and the impact of COVID-19. Previous outbreaks like SARS did not have the global impact that COVID-19 has had, as those outbreaks were more geographically restricted. I never imagined that we would experience a pandemic that involved lockdown for extended periods and us wearing masks for months.

    If people have bats on their property, is it something to be concerned about? At what point do bats become pests and how does one safely remove them?

    Bats are a very important part of our ecological system and are all around us. Frugivorous bats play a role in seed dispersal and pollination of flowers. Insectivorous bats eat insects including mosquitoes. Removing bats will cause an imbalance in the ecosystem, which will cause other problems. However, it does become a problem if there is contact with their excretions, such as urine and faecal matter. This is typically a problem when they move into the roofs of buildings and populations increase. Bats are protected and you are not allowed to exterminate them. Safe removal will depend on the situation; the best thing to do is to contact a bat interest group for advice (http://batsgauteng.org.za). Also, do not handle bats without the necessary protections, to avoid bites or scratches or any contact with bodily fluids.

    How well placed is South Africa to lead research initiatives into coronaviruses like Ebola, SARS, COVID-19 and MERS?

    We are well placed to do this sort of research. Historically speaking, South African scientists were leading Ebola and Marburg virus research; this has expanded to include other potential zoonotic viruses, including coronaviruses. Knowing the diversity of pathogens in bats, and when and where they can be transmitted is important. Routes of transmission must be clearly understood; it can be different depending on the virus or it could be seasonal. This is the basic information needed to start with, but this alone will not stop outbreaks. We need to understand contact with people and other animals, and the risk of transmission. This cannot be extrapolated globally and could be geographic specific due to cultural practices and social needs. Being on the African continent with significant expertise and infrastructure enables South African researchers to play a leading role and perform long-term studies that can provide answers on reasons for spillover. We need to go beyond just testing bats for viruses.

    We have the expertise to take a transdisciplinary approach. Studying these viruses also requires high biocontainment facilities – UP has biosafety level 3 facilities, and through our collaboration with the National Institute for Communicable Diseases, we also have biosafety level 4 capabilities, the only one in Africa. South Africa is therefore playing a leading role in the African region.

    If you are a researcher who would like to work with UP’s CVZ, email Prof Markotter at [email protected]
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