Vaccines for Conservation: Exploring the Feasibility of Protecting Wild Tigers and Other Endangered Carnivores Against Distemper
Wildlife at Risk around the Globe – Scientists Say Vaccinating Endangered Carnivores of Increasing Importance
International Experts Agree on “Top 5” Actions Needed
NEW YORK (February 12, 2015)
The Wildlife Conservation Society (WCS), Cornell University's College of Veterinary Medicine and its Feline Health Center, and the University of Glasgow's Institute of Biodiversity, Animal Health and Comparative Medicine have just co-convened the first "Vaccines for Conservation" international meeting at the Wildlife Conservation Society’s Bronx Zoo in New York City. Experts from around the world focused on the threat that canine distemper virus poses to the conservation of increasingly fragmented populations of threatened carnivores. While canine distemper has been known for many years as a problem affecting domestic dogs, the virus has been appearing in new areas and causing disease and mortality in a wide range of wildlife species, including tigers and lions. In fact, many experts agree that the virus should not be called “canine distemper” virus at all, given the diversity of species it infects.
The forum brought together many of the world's top disease ecologists, wildlife biologists, immunologists, virologists, vaccinologists, epidemiologists, wildlife veterinarians and pathologists, and policy experts to explore whether it would be appropriate and feasible to develop approaches to canine distemper vaccination to protect at-risk wild carnivore populations. The group looked at examples of distemper outbreaks around the world, including the recent case study offered by the Amur tiger population in the Russian Far East. In 2010 canine distemper virus was diagnosed in tigers that died in widely separated locations across the Amur tiger range. While it is challenging to assess the overall impact on the population of such a wide ranging and elusive big cat, the virus contributed to the decline of one well-studied sub-population, which went from 38 individuals to 9 between the years 2007 and 2012.
WCS Russia Program Director Dale Miquelle stated that “Like many large carnivores, tigers face an array of serious threats throughout their range, including poaching (of tigers themselves and of their prey), habitat loss, and conflict with local people. Addressing these very clear threats remains the top priority for the allocation of scarce tiger conservation resources. Importantly, these threats have led to tiger populations becoming smaller and more fragmented, making them much more susceptible to sudden population declines and even extinction due to disease. I therefore welcome the technical help and resources of the veterinary community to enhance our preparedness for addressing pathogens such as canine distemper virus.” In fact, additional analysis by WCS and international colleagues has shown that smaller populations of Amur tigers are more vulnerable than larger populations to extinction from distemper. Populations consisting of 25 individuals are 1.65 times more likely to disappear in the next 50 years if the virus is present. That finding is profoundly disturbing for wild tigers, given that in most sites where wild tigers persist they are limited to populations of less than 25 breeding adults.1
Previous attempts to manage the risk of infectious disease to wild carnivore conservation have mostly focused on vaccination of domestic dogs. While this approach benefits the dogs themselves (and in the case of rabies, can be crucial to protecting local people), it often fails to prevent infections in threatened species that share their environment. This seems to be due to the presence of abundant, small-bodied wild carnivores that act as an alternative reservoir of infection, and a source of canine distemper for endangered species. Cornell University’s Dr. Edward Dubovi emphasized that “The prospect of controlling an infectious disease in an abundant and wide-ranging wildlife reservoir is remote, particularly when there is no economic or public health justification for doing so. Therefore, the most logical approach for protecting threatened carnivores from canine distemper virus may be to target the vaccine on the endangered species itself.” The goal would not be to eliminate a disease like distemper from a given ecosystem, but to protect endangered species in places impacted by pathogens that have often been introduced from elsewhere, often by domestic animals.
This point was driven home by the timely release by the University of Glasgow Boyd Orr Centre for Population and Ecosystem Health of a new analysis of decades of data on the impacts of canine distemper virus on the lions of the Serengeti National Park. During an outbreak that began in 1993, more than one thousand lions disappeared in the Serengeti – a 30% decline in the lion population in the park. While the outbreak in 1993-1994 was likely due to transmission of a virus from domestic dogs, it is now clear that the routes of virus spread and maintenance are more complex. Following the 1993-1994 outbreak, vaccination has successfully reduced the level of infection in the dog population around the Serengeti. However, lion infections have increased over the last 20 years and the timing of infection peaks in lions has not always correlated with dog infection peaks. Glasgow's Dr. Mafalda Viana, who led the multi-author study with colleague Dr. Tiziana Lembo, pointed out that "These results suggest that the virus may now be maintained by a broader carnivore community, potentially involving wildlife as well as domestic dogs beyond the immediate vicinity of the Serengeti National Park. Dog vaccination programs are certainly effective at reducing virus infection in dogs and should continue. But our study has shown that, because of the complex and possibly changing pattern of infections, such programs alone might not be sufficient to fully prevent infection in other species.”
But the threat of canine distemper extends well beyond lions and tigers, and the virus has impacted a number of the world's other carnivores of conservation concern, including the highly endangered Ethiopian wolf and African wild dog, as well as the black-footed ferret in North America, to name just a few examples. "The fact that one kind of virus is affecting so many species in so many parts of the world really merits our attention now—while we can potentially do something about it—not after an extinction event has occurred," noted Dr. Steve Osofsky, WCS' Executive Director for Wildlife Health & Health Policy. "We brought a group of the world’s top experts together to map out a proactive way forward to protect the world's most endangered carnivores, and I am very pleased with the consensus that’s been reached."
The experts attending the Bronx Zoo-hosted Vaccines for Conservation: Exploring the Feasibility of Protecting Wild Tigers and Other Endangered Carnivores Against Distemper recommend the following “Top 5” actions aimed at protecting the world's wild carnivores of conservation concern from distemper and other infectious diseases:
1) Facilitate safe off-label use of existing vaccines – Support collaboration between the zoological community and conservationists in the field to determine the safety as well as efficacy of existing distemper vaccines that could be, at a minimum, administered opportunistically to endangered wild carnivores whenever they are being handled (e.g. during radio-collaring exercises or when being translocated to mitigate human-wildlife conflict).
2) Develop field-friendly rapid diagnostic capabilities – Introduce easy-to-use sample collection kits, linked to field-accessible diagnostic technologies, in order to maximize the health information gathered during rare opportunities to handle live or dead wild carnivores.
3) Enhance disease surveillance in the field – Facilitate the creation of proactive disease surveillance systems that include both domestic and wild animals, to ensure the early detection of health threats to endangered carnivores, and to develop the epidemiological understanding that is crucial to designing effective control measures.
4) Create networks that share health data – Foster sharing of health data among experts within and across wild carnivore range countries, to vastly increase our understanding of disease impacts on endangered populations, and enable proactive and reactive responses when and where they are needed most.
5) Explore new vaccine technologies – Longer term, we need to evaluate new ways to vaccinate wild carnivores for distemper, in situations wherein use of an injectable vaccine is not feasible by hand or by dart. The potential for development of both oral and aerosol vaccines, for example, merits attention.
For additional information on this consensus statement, or to speak with the scientists involved, please contact Scott Smith at 718-220-3698 or firstname.lastname@example.org.
Wildlife Conservation Society (WCS)
MISSION: WCS saves wildlife and wild places worldwide through science, conservation action, education, and inspiring people to value nature. VISION: WCS envisions a world where wildlife thrives in healthy lands and seas, valued by societies that embrace and benefit from the diversity and integrity of life on earth. To achieve our mission, WCS, based at the Bronx Zoo, harnesses the power of its Global Conservation Program in more than 60 nations and in all the world’s oceans and its five wildlife parks in New York City, visited by 4 million people annually. WCS combines its expertise in the field, zoos, and aquarium to achieve its conservation mission. The Wildlife Conservation Society was the first conservation organization with a dedicated team of wildlife veterinarians and other health specialists deployed around the world. The WCS One World, One HealthTM suite of programs focuses on problem-solving at the wildlife / domestic animal / human health and livelihoods interface, as underpinned by a foundation of environmental stewardship. Visit: www.wcs.org. Follow: @thewcs.
Cornell University's College of Veterinary Medicine
The College of Veterinary Medicine at Cornell University values its leadership position in academic veterinary medicine. Advancing veterinary medicine at the interface of discovery and application is the college's unifying conceptual framework. Discoveries identified at the molecular, cellular, organismal, and population levels ultimately inform the practice of medicine. In a parallel fashion, the organization and conduct of medicine influence the type and behavior of research. The college values scholarship across the full spectrum from molecule to medical application and demonstrates this commitment through research, educational programs and professional service. The college will continue to excel in providing education and advanced training that prepare veterinarians and scientists to serve society in critical roles in clinical and diagnostic veterinary medicine, public health, scientific inquiry, and public policy. The college strives to advance animal health through discovery-based research, the delivery of excellent clinical care, and continued vigilance against the spread of disease. The College of Veterinary Medicine at Cornell University endorses the concept of one biology in advancing the understanding of both animal and human health, encourages and fosters open collaboration across disciplines and institutional boundaries, and seeks to integrate discovery and application in order to deliver the greatest possible benefits to society. The College of Veterinary Medicine’s Cornell Feline Health Center is dedicated to improving the health and well-being of cats everywhere by promoting education, research, and outreach.
University of Glasgow's Institute of Biodiversity, Animal Health and Comparative Medicine The Institute carries out a wide range of research in biodiversity and animal health, with a key strength of working on interdisciplinary boundaries. We are distinctive in our ability to link research on animal diseases, production and welfare with ecological and evolutionary approaches. Our research addresses multiple biological levels: from research into molecules and cells, to research into individuals, populations and ecosystems. The need for a holistic approach such as this has never been more pressing, given the threat posed by rapid environmental change and human population increase. We are driven by the need to create multidisciplinary teams to address major research challenges in relation to environmental change, emerging diseases and the conservation of biodiversity. We do this by integrating empirical research with rigorous quantitative analysis, appropriate theoretical frameworks and predictive modelling.
 “Canine Distemper Virus: An Emerging Disease in Wild Endangered Amur Tigers (Panthera tigris altaica)” by Tracie Seimon et al. is available via mBio at http://mbio.asm.org/content/4/4/e00410-13.full?sid=94d4d9ac-17ab-40a1-b114-ce44db5e92a8.
 “Estimating the Potential Impact of Canine Distemper Virus on the Amur Tiger Population (Panthera tigris altaica) in Russia” by Martin Gilbert et al. is available via PLoS ONE at http://www.plosone.org/article/info%3Adoi%2F10.1371%2Fjournal.pone.0110811.
 “Dynamics of a Morbillivirus at the Domestic-Wildlife Interface: Canine Distemper Virus in Domestic Dogs and Lions,” by Mafalda Viana et al. is available online via PNAS athttp://www.pnas.org/content/early/2015/01/15/1411623112.full.pdf+html.