Rodents and bats as reservoirs of zoonoses: ecological and social determinants of human disease risk in Kenya

Recent decades have seen a growing number of dangerous diseases spreading to humans from animal populations. Nearly two-thirds of new human diseases recognized in the past three decades originally came from animals, and two types of animals ? rodents and bats ? are responsible for a disproportionately large percentage of these. Scientists are still trying to understand how these diseases behave in their natural hosts, and what causes them to spill over into human populations, with often fatal consequences. Addressing these complex questions calls for new approaches to research, and particularly for the creation of new partnerships between scientists in different fields. Under the new paradigm, doctors must work closely with veterinarians; these allied health professionals must in turn engage with wildlife ecologists, environmental scientists, and those studying human behaviour, to create novel, effective partnerships that will enable us to predict and, importantly, prevent future disease outbreaks.

For the first time in human history, more of us now live in cities than in the countryside, and this number is still growing rapidly. More and more, cities will become the new battleground where the war against emerging diseases will be fought. Nowhere is this more true than in the slums of the third world, where nearly a third of the world?s population already live in overcrowded conditions, with inadequate access to safe water, sanitation and health services. Certain species of rodents and bats are adapted to this human environment, living in houses, stores, sewers and gardens, and exchanging pathogens through excreta, parasites (fleas, mites and ticks), or direct contact, including bites. In our increasingly connected world, a new human disease which emerges from such an environment has the capacity to spread rapidly across the globe, an event we have already witnessed with the emergence of SARS from bats in south-east Asia.

This project, led by the University of Glasgow with partners in Kenya, UK and USA, aims to bring together scientists from different backgrounds, ranging from human and animal health to history and social science. Their aim will be to help understand when and why human diseases emerge from animal hosts, and what can be done to prevent future outbreaks. The strength of the project lies in the creation of new, effective partnerships to address emerging disease threats, under the new paradigm of ?One World, One Health?.

Emerging zoonotic diseases pose a growing threat to human health, but little is still known about the factors affecting pathogen dynamics in wild animal host populations or the specific drivers of emergence in humans. Of particular concern are rodent and bat species, which are disproportionately represented as hosts of human emerging zoonoses. Many rodent and bat species have adapted to and thrive in human environments, including informal urban settlements in developing countries, and pose a threat to public health by acting as reservoirs of pathogens that are capable of infecting humans. Transmission of these pathogens to humans is frequently fatal, as in the case of haemorrhagic fever viruses or plague. The current proposal aims to establish a novel, interdisciplinary research consortium to improve our understanding of the role of rodents and bats in the maintenance and spread of emerging and re-emerging infectious diseases in different human environments in a developing country, and to explore the ecological, social and cultural factors which may contribute to pathogen spill-over into human populations. Most research on the ecology of rodent and bat pathogens has been conducted in Europe, Asia and the Americas, with little known about these zoonotic pathogens in African contexts, particularly urban environments. There is also very little understanding of the social and cultural determinants of human disease risk in these settings. Specific questions which will be explored by the consortium include the effect of the natural and social environment on host community structure (species diversity and abundance); the influence of host community structure on the dynamics and infection risk for humans of a range of zoonotic pathogens; the social and cultural factors which determine if this background disease risk leads to human exposure and disease; and an examination of the historical occurrence of and response to rodent-borne zoonotic disease outbreaks in the selected study sites. These questions will be addressed through the creation of new, interdisciplinary, cross-sector partnerships encompassing teams involved in high-quality, innovative research across the spectrum of health, environmental, social and biological sciences, and involving stakeholders and end-users. Previous and ongoing research by existing medical-veterinary collaborations applying the concept of One Health in Kenya will form the nucleus of the new consortium.