William B. Karesh

Wildlife Trade and Global Disease Emergence

The global trade in wildlife provides disease transmission mechanisms that not only cause human disease outbreaks but also threaten livestock, international trade, rural livelihoods, native wildlife populations, and the health of ecosystems. Outbreaks resulting from wildlife trade have caused hundreds of billions of dollars of economic damage globally. Rather than attempting to eradicate pathogens or the wild species that may harbor them, a practical approach would include decreasing the contact rate among species, including humans, at the interface created by the wildlife trade. Since wildlife marketing functions as a system of scale-free networks with major hubs, these points provide control opportunities to maximize the effects of regulatory efforts.

Prediction and prevention of the next pandemic zoonosis

Summary Most pandemics—eg, HIV/AIDS, severe acute respiratory syndrome, pandemic influenza—originate in animals, are caused by viruses, and are driven to emerge by ecological, behavioural, or socioeconomic changes. Despite their substantial effects on global public health and growing understanding of the process by which they emerge, no pandemic has been predicted before infecting human beings. We review what is known about the pathogens that emerge, the hosts that they originate in, and the factors that drive their emergence. We discuss challenges to their control and new efforts to predict pandemics, target surveillance to the most crucial interfaces, and identify prevention strategies. New mathematical modelling, diagnostic, communications, and informatics technologies can identify and report hitherto unknown microbes in other species, and thus new risk assessment approaches are needed to identify microbes most likely to cause human disease. We lay out a series of research and surveillance opportunities and goals that could help to overcome these challenges and move the global pandemic strategy from response to pre-emption.

Ecology of zoonoses: natural and unnatural histories

Summary More than 60% of human infectious diseases are caused by pathogens shared with wild or domestic animals. Zoonotic disease organisms include those that are endemic in human populations or enzootic in animal populations with frequent cross-species transmission to people. Some of these diseases have only emerged recently. Together, these organisms are responsible for a substantial burden of disease, with endemic and enzootic zoonoses causing about a billion cases of illness in people and millions of deaths every year. Emerging zoonoses are a growing threat to global health and have caused hundreds of billions of US dollars of economic damage in the past 20 years. We aimed to review how zoonotic diseases result from natural pathogen ecology, and how other circumstances, such as animal production, extraction of natural resources, and antimicrobial application change the dynamics of disease exposure to human beings. In view of present anthropogenic trends, a more effective approach to zoonotic disease prevention and control will require a broad view of medicine that emphasises evidence-based decision making and integrates ecological and evolutionary principles of animal, human, and environmental factors. This broad view is essential for the successful development of policies and practices that reduce probability of future zoonotic emergence, targeted surveillance and strategic prevention, and engagement of partners outside the medical community to help improve health outcomes and reduce disease threats.

Middle East Respiratory Syndrome Coronavirus Infection in Dromedary Camels in Saudi Arabia

ABSTRACT The Middle East respiratory syndrome (MERS) is proposed to be a zoonotic disease; however, the reservoir and mechanism for transmission of the causative agent, the MERS coronavirus, are unknown. Dromedary camels have been implicated through reports that some victims have been exposed to camels, camels in areas where the disease has emerged have antibodies to the virus, and viral sequences have been recovered from camels in association with outbreaks of the disease among humans. Nonetheless, whether camels mediate transmission to humans is unresolved. Here we provide evidence from a geographic and temporal survey of camels in the Kingdom of Saudi Arabia that MERS coronaviruses have been circulating in camels since at least 1992, are distributed countrywide, and can be phylogenetically classified into clades that correlate with outbreaks of the disease among humans. We found no evidence of infection in domestic sheep or domestic goats. IMPORTANCE This study was undertaken to determine the historical and current prevalence of Middle East respiratory syndrome (MERS) coronavirus infection in dromedary camels and other livestock in the Kingdom of Saudi Arabia, where the index case and the majority of cases of MERS have been reported. This study was undertaken to determine the historical and current prevalence of Middle East respiratory syndrome (MERS) coronavirus infection in dromedary camels and other livestock in the Kingdom of Saudi Arabia, where the index case and the majority of cases of MERS have been reported.

Wild Animal Mortality Monitoring and Human Ebola Outbreaks, Gabon and Republic of Congo, 2001-2003

An animal mortality monitoring network in Gabon and the Republic of Congo has demonstrated potential to predict and possibly prevent human Ebola outbreaks.

A Strategy To Estimate Unknown Viral Diversity in Mammals

ABSTRACT The majority of emerging zoonoses originate in wildlife, and many are caused by viruses. However, there are no rigorous estimates of total viral diversity (here termed “virodiversity”) for any wildlife species, despite the utility of this to future surveillance and control of emerging zoonoses. In this case study, we repeatedly sampled a mammalian wildlife host known to harbor emerging zoonotic pathogens (the Indian Flying Fox, Pteropus giganteus) and used PCR with degenerate viral family-level primers to discover and analyze the occurrence patterns of 55 viruses from nine viral families. We then adapted statistical techniques used to estimate biodiversity in vertebrates and plants and estimated the total viral richness of these nine families in P. giganteus to be 58 viruses. Our analyses demonstrate proof-of-concept of a strategy for estimating viral richness and provide the first statistically supported estimate of the number of undiscovered viruses in a mammalian host. We used a simple extrapolation to estimate that there are a minimum of 320,000 mammalian viruses awaiting discovery within these nine families, assuming all species harbor a similar number of viruses, with minimal turnover between host species. We estimate the cost of discovering these viruses to be ~

Habituating the great apes: the disease risks

6.3 billion (or ~

Roadless Wilderness Area Determines Forest Elephant Movements in the Congo Basin

1.4 billion for 85% of the total diversity), which if annualized over a 10-year study time frame would represent a small fraction of the cost of many pandemic zoonoses. IMPORTANCE Recent years have seen a dramatic increase in viral discovery efforts. However, most lack rigorous systematic design, which limits our ability to understand viral diversity and its ecological drivers and reduces their value to public health intervention. Here, we present a new framework for the discovery of novel viruses in wildlife and use it to make the first-ever estimate of the number of viruses that exist in a mammalian host. As pathogens continue to emerge from wildlife, this estimate allows us to put preliminary bounds around the potential size of the total zoonotic pool and facilitates a better understanding of where best to allocate resources for the subsequent discovery of global viral diversity. Recent years have seen a dramatic increase in viral discovery efforts. However, most lack rigorous systematic design, which limits our ability to understand viral diversity and its ecological drivers and reduces their value to public health intervention. Here, we present a new framework for the discovery of novel viruses in wildlife and use it to make the first-ever estimate of the number of viruses that exist in a mammalian host. As pathogens continue to emerge from wildlife, this estimate allows us to put preliminary bounds around the potential size of the total zoonotic pool and facilitates a better understanding of where best to allocate resources for the subsequent discovery of global viral diversity.

Movements and location at sea of South American sea lions (Otaria flavescens)

All six great apes, gorillas Gorilla gorilla and G. beringei , chimpanzees Pan troglodytes and P. paniscus , and orang-utans Pongo pygmaeus and P. abelii , are categorized as Endangered on the 2000 IUCN Red List and face many threats to their continued existence in the wild. These threats include loss of habitat to settlement, logging and agriculture, illegal hunting for bushmeat and traditional medicine, the live ape trade, civil unrest and infectious diseases. The great apes are highly susceptible to many human diseases, some of which can be fatal while others can cause marked morbidity. There is increasing evidence that diseases can be transmitted from humans to free-living habituated apes, sometimes with serious consequences. If protective measures are not improved, ape populations that are frequently in close contact with people will eventually be affected by the inadvertent transmission of human diseases. This paper describes the risks, sources and circumstances of infectious disease transmission from humans to great apes during and consequent upon habituation for tourism and research. A major problem is that the regulations that protect habituated apes from the transmission of disease from people are often poorly enforced. Suggestions are made for improving the enforcement of existing regulations governing ape-based tourism, and for minimizing the risk of disease transmission between humans, both local people and international visitors, and the great apes.

Middle East Respiratory Syndrome Coronavirus Quasispecies That Include Homologues of Human Isolates Revealed through Whole-Genome Analysis and Virus Cultured from Dromedary Camels in Saudi Arabia

A dramatic expansion of road building is underway in the Congo Basin fuelled by private enterprise, international aid, and government aspirations. Among the great wilderness areas on earth, the Congo Basin is outstanding for its high biodiversity, particularly mobile megafauna including forest elephants (Loxodonta africana cyclotis). The abundance of many mammal species in the Basin increases with distance from roads due to hunting pressure, but the impacts of road proliferation on the movements of individuals are unknown. We investigated the ranging behaviour of forest elephants in relation to roads and roadless wilderness by fitting GPS telemetry collars onto a sample of 28 forest elephants living in six priority conservation areas. We show that the size of roadless wilderness is a strong determinant of home range size in this species. Though our study sites included the largest wilderness areas in central African forests, none of 4 home range metrics we calculated, including core area, tended toward an asymptote with increasing wilderness size, suggesting that uninhibited ranging in forest elephants no longer exists. Furthermore we show that roads outside protected areas which are not protected from hunting are a formidable barrier to movement while roads inside protected areas are not. Only 1 elephant from our sample crossed an unprotected road. During crossings her mean speed increased 14-fold compared to normal movements. Forest elephants are increasingly confined and constrained by roads across the Congo Basin which is reducing effective habitat availability and isolating populations, significantly threatening long term conservation efforts. If the current road development trajectory continues, forest wildernesses and the forest elephants they contain will collapse.