What’s New About “Zoobiquity”?

 I just finished reading my copy of the new book Zoobiquity: What Animals Can Teach us about Health and the Science of Healing, by Barbara Natterson-Horowitz and Kathryn Bowers. It is a ground-breaking book and essential reading for anyone interested in the connections between human and animal medicine. The authors illustrate, through a large number of side by side comparisons, the striking parallels between clinical conditions in animals and humans, and what these similarities can suggest about the root causes of disease (including evolution and environment) and how best to treat them. Readers familiar with “One Health” concepts will find in the book vivid examples of the convergence of human, animal, and environmental health in emerging infectious diseases and animals as sentinels of toxic and infectious hazards in the environment. Yet, it is worth focusing on some of the truly innovative aspects of this book. First, Zoobiquity boldly asserts that by neglecting its comparative medicine roots, clinical medicine itself has gone astray and the medical profession needs to use the perspective of clinical science that spans different species to get back on track. We need to understand mental health problems such as addiction and self-destructive behaviors in the context of evolution and environment, just as naturalists and veterinarians strive to do, and use this perspective to design new treatment and prevention approaches. Similarly, we need to use the same tools of evolutionary and environmental understanding to rethink our approaches to chronic diseases such as obesity and cancer. Second, Zoobiquity builds the strongest case to date for greater development of clinical knowledge of animal health using techniques that are driving evidence based medicine such as randomized trials and large observational cohorts followed over time in order to glean important information useful for both animal and human health. Third, the concepts in Zoobiquity are presented so clearly and documented so extensively that they appear to have struck a chord in both the general population (see Oprah’s 2012 summer reading list) and the medical community that propels the discussion of human animal medicine linkages to a whole new level. Overall, Zoobiquity throws a gauntlet out to the biomedical scientific and clinical community, urging it not to delay further, but instead to set up an effective research and development infrastructure to pilot and test new hypotheses and clinical approaches using this enhanced comparative model It will be fascinating to see who comes forward to accept this challenge.

“Contagion” and Emerging Infectious Diseases from an Occupational and Environmental Medicine Perspective.

The past two decades have seen some remarkable emergence of new and deadly pathogens, from SARS to avian influenza H5N1 and the novel 2009 H1N1influenza strain. It is often pointed out that a majority of recent emerging infections are “zoonotic” (transmitted from animals to people) in origin. The movie “Contagion” follows on this theme by depicting a novel virus sweeping the globe. About halfway through the movie, we learn that the virus has genetic sequences from both bats and pigs, implying that at some point “the wrong bat met up with the wrong pig”.

At the end of the movie, there is a montage that hints at the origin of the new lethal virus. Fruit bats in disturbed rain forest are seen flying and having contact with pigs in a large barn. The montage follows the pigs and presumably the virus as the pigs go to market and slaughter and into a restaurant in Asia where blood on the chef’s hands and apron appears to infect the business traveler character played by Gwyneth Paltrow, who then becomes the “index” patient spreading the epidemic from person to person around the globe.

This bat-to-pig-to-human scenario hearkens back to the real emergence of a novel virus called "Nipah virus" from a fruit bat reservoir in Malaysia into pig farms located close to areas of recently logged rain forest (see review by Chua 2003 ) . In 1999, Nipah virus caused a new and fatal encephalitis in Malaysian pig workers and a milder disease in pigs. It is thought that the movement of sick pigs spread the disease to other parts of the country, often infecting other pig workers.

The Nipah outbreak in Malaysia is a reminder about how often it is the people working closely with animals or their products who first experience disease from a viral or bacterial pathogen crossing from animals to humans.

Similarly, with SARS, while we now think that the virus may have emerged from a natural reservoir in bats and spread to humans via intermediate host animals such as civets, the initial animal to human transmission events may have involved workers in animal markets, who have been found to have elevated rates of antibodies to the virus, suggesting that they had become infected through their work with animals (CDC MMWR 2003).

With avian influenza, the majority of human case have been among people performing tasks associated with poultry production, trade, and consumption, such as working on farms, in animal markets, or butchering and preparing poultry for consumption.

 

And with the 2009 H1N1 virus, while the emergence events remain unknown there is a suspicion that one of the key events was zoonotic transmission from swine influenza viruses to humans working closely with the animals.

So, what if emerging infectious diseases can be seen as a problem of animal workers? It might lead us to pay greater attention to these workers than we do currently.

Agricultural animal workers work worldwide across a large spectrum of activities, from backyard farms to large industrialized facilities, to large and small slaughter facilities to animal markets. They deal on a daily basis with a wide range of hazards, from injuries, to inhalation of dusts, to the possibility of infection from the animals.  Regardless of whether these animal workers are members of the “informal work sector”  (such as workers on family farms), or salaried employees in large mechanized facilities, in general, in contrast to, say, factory workers, there are no regular programs to monitor or foster their health and safety. Their health and safety concerns, including their risk of occupational infections, are ‘off the radar’ of most physicians who practice the specialty “occupational and environmental medicine” (the diagnosis, treatment, and prevention of diseases caused by exposure to hazards at work and in the environment). In addition, due to their often marginal economic status,  they may also not be receiving medical care benefits or have access to regular basic medical care.

In the U.S., many agricultural animal workers are recent immigrants who may be less aware of their health and safety conditions, and due to language and cultural barriers less likely to access such information if it is provided by the employer or others.

What is needed is more awareness of the work these people do and better ways to help them do it in a healthy way that reduces the risk of disease transmission. Ironically, doing so may be also be better for animal health, since we have seen that “zoonotic” pathogens can sometimes move in both directions, from animal to human or from human to animal (‘humanosis’ or ‘reverse zoonosis’). An example is H1N1 influenza, which, as it spread globally, demonstrated many more instances of humans apparently infecting animals (pigs, cats, etc.) than the other way around. So keeping animal workers healthy may help keep animals healthy as well!

In addition to the occupational medicine aspects of emerging zoonotic infections, it is also important to look at the environmental aspects. When Nipah virus emerged in Malaysia, it was related to the way that the farms were impacting the forest ecosystem. And many of the recent episodes of food safety problems seem to be caused by persistence of  pathogens in the environment related to the way that animal waste and human waste are handled.

Perhaps in the future there can be greater emphasis on a “One Health” approach to animal agriculture, one that brings together experts in agriculture, veterinary medicine, environmental health, and human occupational health, and that emphasizes the value of healthy workers and healthy animals, and the need to raise animals in such a way that the environment is enhanced. It would seem that to take our attention off of any of these three issues (the health of animals, animal workers, and the environment), and their interrelationships, in our push as a society to produce greater amounts of animal protein to feed a growing human population is to risk big problems in the long run.

The Need for Evidence

Over the past decade, human medicine has become more “evidence based.” Under this paradigm, recommended clinical policies regarding prevention, diagnosis, and treatment of diseases should be based on explicit evidence of the value of a particular approach. For example, whether or not a patient should be started on a daily aspirin for prevention of heart disease should be based on studies of such an intervention, and a weighing of the reported benefit of the intervention versus both the risk and cost of the intervention. The push for evidence based recommendations has resulted in certain traditional treatment approaches being abandoned and new ones adopted.

When it comes to human-animal medicine issues, including the use of animals as sentinels for human environmental health hazards, the use of animal assisted therapy for certain medical conditions, measures to prevent zoonotic disease in animal workers, and even the potential impact of adopting a “One Health” approach to disease prevention in the developing world, the truth is that there is a relative lack of “high quality”  evidence (such as controlled studies) either supporting or not supporting such interventions. This of course does not mean that such approaches are not worthwhile or do not hold potential for enhanced treatment and diagnosis of disease affecting both humans and animals (there is abundant anecdotal evidence that it may). Rather it means that there is a real need for research to test and rigorously evaluate such approaches. The Canary Database is an attempt to bring together published evidence about animals as sentinels of human environmental health hazards. Users can see “summary screens” that provide preliminary summaries of the strength of evidence that for a particular environmental hazard, particular species of animals may be either more susceptible, show shorter latency between exposure and disease onset, or have greater environmental exposure compared to humans. Advocates of “One Health” should be willing to see the concept tested objectively, and use the results to better hone future efforts to integrate human, animal, and environmental health.  Conducting studies that search for such evidence will better justify the commitment of health care resources in a human-animal medicine direction.