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.

Human Health Care Providers and Veterinarians Need to Communicate

It is not uncommon for patients to ask me whether an illness in a pet could be related to symptoms they are experiencing. For example, a patient suffering from allergies caused by mold in her house told me about her dog that was being treated by a veterinary allergist. Was it possible that human and dog were dealing with the same problem?

What are physicians or other health care providers supposed to do with such questions and information? Physicians receive no training in veterinary diseases and are not taught how to appropriately respond to these issues. Should a doctor ask more questions about the dog’s illness? Ask to speak to the veterinarian? Is this a useful line of inquiry or mere frivolous waste of time?

Over 60% of U.S. households include at least one pet (Hoff1999), and this proportion is increasing. Often the degree of medical care that the pets are receiving equals or exceeds the medical care happening for humans in the household. There is a basic rule that veterinarians are not allowed to treat human patients (but veterinarians tell me that their clients often ask for medical advice about zoonotic diseases and other conditions). Physicians, for their part, are not supposed to diagnose or treat animals (but tell that to the rural family doctor I met this week who is regularly asked to take care of goats and cows and dogs). At the same time, there are growing similarities between veterinary medicine and human medicine. (Rabinowitz and Conti 2010) Both disciplines use similar blood tests, urine test, and radiological studies to diagnose disease. Both use similar (but not always identical) medications to treat infections, diabetes, and even mental illness. And there can be value in seeing the numerous similarities between medical conditions that manifest in an animal and a human, as physicians such as Barbara Natterson have noted (see her zoobiquity website http://www.zoobiquity.com )

There are a number of specific reasons why physicians and veterinarians need to communicate and collaborate. Contact with pets or other animals can increase the risk of zoonotic (animal to human) disease transmission, especially for children and immunocompromised individuals (Pickering et al 2008, Kaplan et al 2009, NASPHV 2011), and veterinarians can contribute to effective prevention of such transmission. Veterinarians can also work with clients to reduce the risk of animal bites from pets. Beyond the risk of infections and injuries, people may share chronic health problems such as obesity with their companion animals, and be willing to engage in joint preventive behaviors such as exercise programs (Kushner et al 2006). The strength of the human-animal bond may affect psychosocial health, as well as access to medical care (for example; a patient unwilling to leave pets at home to go to the hospital). Drug-seeking patients may request pain medication and other controlled medications from veterinarians on the pretense that it is needed for their pets (LeBourgeois et al 2002).

In addition, illness in an animal may be a “sentinel event” indicating environmental risk for humans (see the Canary database www.canarydatabase.org for more information on this). An example would be allergies due to a common allergen in the environment, or a dog that is diagnosed with a tick-borne disease giving warning about risk to humans who walk  in the same suburban areas as the dog.

Despite all of these apparently obvious reasons for communication and collaboration between veterinarians and human health care providers, real life examples appear to be rare. The practice of medicine is increasingly evidence-based (as it should be), and the lack of published studies documenting the benefit of such encounters between professionals makes it hard to change current practice patterns. At the same time, there are also no studies showing a lack of benefit of such teamwork! In other words, these ideas, however obvious and promising, remain virtually untested.

What are needed are good pilot projects and studies to begin documenting proof of concept of collaboration between human and animal health professionals. These studies could test the acceptability and effectiveness of clinical protocols and materials such as templates for referrals between veterinarians and their human health counterparts. As information begins to flow between the disciplines, the evidence will be able to point future practice patterns in the correct direction. I (and many others) will welcome that day.

References:

Hoff GL, Brawley J, Johnson K. Companion animal issues and the physician. South Med J. 1999; 92:651-9.

Kaplan JE, Benson C, Holmes KH, Brooks JT, Pau A, Masur H. Guidelines for prevention and treatment of opportunistic infections in HIV-infected adults and adolescents. MMWR Recomm Rep. 2009;58(RR-4):1-207.

Kushner RF, Blatner DJ, Jewell DE, Rudloff K. The PPET Study: people and pets exercising together. Obesity 2006;14:1762-70.

LeBourgeois HW 3rd, Foreman TA, Thompson JW Jr. Novel cases: malingering by animal proxy. J Am Acad Psychiatry Law. 2002;30:520-4.

National Association of State Public Health Veterinarians, Inc. (NASPHV); Centers for Disease Control and Prevention (CDC).Compendium of measures to prevent disease associated with animals in public settings, 2011: MMWR Recomm Rep. 2011 May 6;60(RR-04):1-24.

Pickering LK, Marano N, Bocchini JA, Angulo FJ. Exposure to nontraditional pets at home and to animals in public settings: risks to children. Pediatrics. 2008; 122:876-86.

Rabinowitz PM, Conti LA. Human Animal Medicine: Clinical Approaches to Zoonoses, Toxicants and other Shared Health Risks. Elsevier 2010; 432 pp.

One Health, Ethics, and Controlling Zoonoses

Recently, a commentary on the practice of culling animals to reduce the risk of zoonotic diseases (Johansen and Penrith 2009; ) caught my attention. The authors were making note of a study in China by Xianget al reporting on an intervention to control a parasitic disease (cystic hydatiddisease) caused by the dog tapeworm Echinococcus granulosus. The lifecycle of Echinococcus granulosus is fairly complex (interested readers can see a nice diagram at the CDC website) but in short, dogs can serve as the definitive host for the tapeworm, which they get by eating the carcasses of sheep or other infected animals. Infected dogs then pass eggs in their feces which can be ingested by and infect humans or other animals. In humans, the tapeworm can develop and cause expanding cysts in the liver, brain, lung and other tissues which can be associated with serious illness (hydatid disease) including abdominal pain and seizures.

At any rate, the goal of the Chinese researchers was to reduce the rate of hydatid disease in two Chinese counties. In these counties, with a combined human population of about 255,000 ,  the annual rate of hydatid disease was estimated at about 44/100,000, or roughly 112 cases per year, of which as significant percentage required surgery to remove cysts. The researchers’ disease control strategy was to stop the dogs in the area from eliminating the parasite eggs into the environment through their feces. To do this, the research team attempted to treat all the registered dogs in the study area each month with praziquantel, an antiparasitic medication that could eliminate the worm. At the same time,  they captured and “humanely” killed stray and unwanted dogs in the two study counties. According to the report, 10,575 dogs were killed as part of the intervention. (The authors noted that there were more stray dogs in one of the counties with a higher proportion of Muslims, who avoid eating dogs as meat, in the other, largely non-Muslim, county, dogs were a source of food for humans and there were fewer strays). A small fee charged to dog owners paid for the treatment and culling of the dogs.

The study reported that the intervention strategy successfully reduced the prevalence of hydatid disease in sheep to virtually zero, and also reduced the rate of infection in dogs (who usually have few symptoms from the infection).

In their commentary about the study, Johansen and Penrith state that “culling animals has been used in many parts of the world as a highly effective way to control and eliminate various infectious diseases of both veterinary and human health importance” (culling of poultry has been a major tactic in the effort to control outbreaks of avian influenza)  but that such culling programs raise “ dilemmas regarding ethics, validity of the research, and research ethical questions”. In particular, Johansen and Penrith argue, the evidence supporting the use of culling should be carefully considered, as should the social, economic, and cultural impact on local populations. 

The concept of “One Health” , which has received a lot of attention recently (see Kaplan et al 2009) may also provide some new perspective to debates over the culling of animals to control zoonotic disease. While definitions vary, One Health has been described as:  

“The collaborative effort of multiple health science professions, together with their related disciplines and institutions – working locally, nationally, and globally – to attain optimal health for people, domestic animals, wildlife, plants, and our environment.”

Following the One Health line of reasoning, what does it truly mean to “attain optimal health for people, domestic animals, wildlife, plants, and our environment.”?  There appears to be an implicit assumption that this can be a win-win situation all around, and that what is good for the people can also be good for the animals, plants, and the environment.

While this is a very attractive proposition, the methodology of the Xiang study suggests that the reality ‘on the ground’ is not all win-win. Their hydatid disease control strategy (which has now been replicated in other parts of China) appears to have been good for humans, sheep, and registered dogs, and also perhaps good for the environment (less contamination by dog tapeworms), but it was decidedly not good for the stray and unwanted dogs. I wonder, however, how often this has been tested in reality. If one wants to control a disease like cystic hydatid disease, what is the way to do it that maximizes the health of people, animals, and the environment? If there are tradeoffs to be made, how are those judged? The Xiang study provides some hard numbers for the choices made in one case: 10,575 dogs culled to prevent a several hundred human cases of a parasitic disease.

I have previously discussed culling as one of the aspects of the  “us vs. them” attitude that human health professionals may take toward when faced with potential health risks of zoonotic or other animal-associated diseases. (See Rabinowitz et al 2008) . In that paper, we argue that it may be useful to move from the “us vs. them” approach toward a model of “shared risk” between humans and animals facing increased disease threats from the environment. The “shared risk” approach requires an examination of the changing environment and whether it could be driving disease risk in both animals and humans. In the case of Echinococcus-caused hydatid disease, for example, have there been changes in the density of sheep, dogs, and humans that make the disease risk more intense? If so, could environmental measures, such as better fencing or other measures to keep dogs away from sheep carcasses, play a role in disease control? Are there other ways to deal with stray dogs besides culling (such as spay/neuter programs). It is interesting to note, that for rabies, another dog-associated zoonosis, researchers have proposed that in China, immunization may replace culling as an effective control strategy (see Zhang et al ) . In short, are there alternative ways to maximize the health of the humans, animals, and the environment in order to achieve the closest thing to a win-win situation? There may be tradeoffs between short term and long term successes, and what works in the short term (culling dogs) may not necessarily address some long term environmental issues that are driving disease risks.

These cases suggest the need to examine the ethics underlying a One Health approach to zoonotic disease control and other diseases at the human-animal- environment interface. They also indicate that we have to strive to better understand the complex interactions that lead to emerging infectious diseases, and the tradeoffs required to control and prevent such diseases in the future. 

“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.

High altitude cattle and comparative medicine

A recent article in the New York Times is a reminder of the potential for new approaches to comparative medicine outside of the typical research laboratory. For years, veterinary researchers have studied the effect of high altitude on cattle grazing in mountainous areas of New Mexico and elsewhere. These studies have revealed important findings about the chronic effect of hypoxia on the cardiovascular system, including insight into the condition of hypoxic pulmonary hypertension that is an important disease in humans. The researchers have also been able to study the effect of genetic susceptibility on these physiologic responses, and to develop clinical approaches for early diagnosis of altitude illness. The recent research reported in the Times actually builds on studies of high altitude cattle in Colorado and other parts of the Southwestern US that have gone on over the past 100 years. And while we have learned a lot about human pulmonary hypertension (a disease that develops in individuals with sleep apnea and other hypoxic conditions) from “Brisket disease” in cattle, there are also preventive lessons to learn from animals that are evolutionarily adapted to high altitude, such as certain types of llamas, rodents, and yaks. These adaptations can involve not only much thinner blood vessels in the lungs, but also a lack of the response to low oxygen that is seen in cows and persons who develop pulmonary hypertension.  These findings reinforce the fact that there is much to learn from studies of naturally occurring animal populations that can influence both human medicine, veterinary medicine, and our understanding of the effects of environmental factors on health.  

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.

Welcome to the Yale Human Animal Medicine Project blog!

We are excited to welcome you to the Yale Human Animal Medicine Project blog.  We hope to bring you informative and interesting posts on our current projects, new journal articles, and news in the world of zoonotic research. 

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