“One Health is the collaborative efforts of multiple disciplines working locally, nationally, and globally to attain optimal health for people, animals, plants and our environment.”
“One Health implementation will help protect and/or save untold millions of lives in our generation and for those to come.”
“Between animal and human medicine there are no dividing lines--nor should there be.” Rudolf Virchow, MD (the father of cellular pathology)
A significant One Health issue...
NOTE: The Ebola virus vaccine topic has been widely disseminated in national and international news reports today and yesterday:
Conquest of Ebola in Humans and Animals
Provided to the One Health Initiative website December 23, 2016 by:
*Thomas P. Monath, MD
Chief Scientific & Chief Operating Officer
BioProtection Systems/NewLink Genetics Corp.
94 Jackson Rd. Suite 108
Devens, MA 01434
Henao-Restrepo et al. report the final results of a large efficacy trial of a novel, live attenuated vaccine against Ebola conducted in 2015 in the Republic of Guinea (Lancet, Published online December 22, 2016 http://dx.doi.org/10.1016/S0140-6736(16)32621-6). A single inoculation of the vaccine proved 100% effective in preventing Ebola virus disease. The trial was conducted under the leadership of the World Health Organization, in difficult circumstances during the large West African epidemic underway at the time and utilized a ring vaccination strategy which is described in detail in the publication. The vaccine tested is a recombinant virus composed of vesicular stomatitis virus Indiana (VSV-I) in which the envelope glycoprotein of VSV has been replaced by the corresponding envelope protein of Zaire ebolavirus (ZEBOV). The use of VSV, a virus causing infection and disease in animals (cattle, horses, and pigs), as the backbone for construction of a human vaccine is certainly noteworthy in the context of One Health, although there are analogous examples (e.g. vaccinia). The recombinant VSV-ZEBOV vaccine (rVSV-ZEBOV) was originally developed by the Public Health Agency of Canada and then licensed to and further developed by NewLink Genetics Corp. In 2014 the technology was exclusively licensed by NewLink to Merck, which is advancing development towards regulatory approval in the next 1-2 years.
It is expected that the availability of this vaccine will lead to the rapid control of future outbreaks of Ebola virus disease so that horrific events like the West African epidemic (2013-16) which caused over 28,000 cases and 11,000 deaths, will never be seen again.
Ebola outbreaks arise when the virus spills over from primary or secondary wild animal hosts. Like other zoonoses this disease exemplifies many principles of One Health. The primary reservoir hosts of ebolavirus are fruit bats, and direct contact with these animals or with fomites contaminated by bats are a probable source of human infection. Fruit bats are valued as a food source and are hunted and sold as bushmeat. Other animals including chimpanzees, bonobos, gorillas, monkeys, forest antelope and porcupines may be secondarily infected, are also hunted as bushmeat, and serve as a source of human infections. It is a continuing challenge to educate local populations about the role of these animals in disease transmission when they are valued as food in subsistence economies.
The great apes are highly susceptible to ebolavirus and develop lethal infections similar to humans. Human outbreaks have been directly caused by transmission from ape carcasses contaminated with the virus. The great apes are already threatened by habitat loss and have a low reproductive rate, and ebolavirus further threatens their survival. In 2003-2004 an epizootic of Zaire ebolavirus is believed to have killed over 90% of the western lowland gorillas in the Lossi Sanctuary and in Odzala-Kokoua National Park in the Republic of Congo (Brazzaville). By some estimates, over 50,000 great apes have died in ebolavirus outbreaks in Central Africa in the last 10-15 years. This is a concern for conservation in general, for ecotourism which supports local economies, and for public health.
Given the advances in vaccine development, an obvious question is: How to use vaccines to prevent disease and deaths in wild animals, particularly the great apes? The result could not only reduce the treat to these endangered species, but also potentially reduce the risk of virus transmission to humans. The problem is vaccine delivery rather than vaccine development. The rVSV-ZEBOV vaccine is safe and highly effective in preventing ebola in monkeys and almost certainly would be also safe and effective in apes. A non-replicating, recombinant virus-like particle vaccine was used successfully to immunize captive chimpanzees (Warfield KL et al., PNAS 2014;111:8873-6). Use of these injected vaccines in the wild might be limited to darting small numbers of habituated animals in reserves. Delivery of rVSV-ZEBOV in oral bait may be considered as the vaccine appears to work by the oral route in monkeys. More promising is recent work on recombinant cytomegaloviruses (CMV) expressing ebola glycoprotein (Marzi A et al. Sci Rep. 2016;6:21674). CMV is transmissible and causes persistent infections, so that once introduced the vaccine virus might spread within the ape population, thus avoiding the need to immunize individuals.
Now that the control of human Ebola virus disease appears to be close at hand through the use of a vaccine, extension to animal species affected by this disease is the next horizon. Reaching that goal will require close collaboration across the medical and veterinary fields, ecologists, conservation scientists, and others in the One Health community.
*Dr. Monath http://www.onehealthinitiative.com/publications/Tom%20Monath%20Biography%20January2014%20(2015%20update).pdf, a physician and eminent internationally recognized medical virologist, is a co-founder of the One Health Initiative Autonomous pro bono team and the One Health Initiative website www.onehealthinitiative.com.