conservation medicine

7 Days at Alcedo Volcano

A second blog of our July 2018 trip of a lifetime. This one written and illustrated by trip photographer, Joshua Vela Fonesca. Joshua shares his artistic vision as the Galapagos Tortoise Movement Ecology Programme team (well - not the whole team. Steve and Anne were back on Santa Cruz Island!) works for tortoise conservation.

Joshua’s photography and words capture this magical week!


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An Inconvenient Truth – Zoonotic Pathogens

An Inconvenience Truth - Zoonotic Pathogens.png


Animal to Human Pathogen Transmission

Most likely in the last year you have heard of at least one disease event caused by a  pathogen “spillover” from animals to humans. I would even venture if you have not heard of any zoonotic disease, you probably live in a bunker in Indiana. Coverage of these disease events has increased greatly in recent years as the frequency and types of human and animal intersections continue to escalate. Zoonotic diseases—those infectious diseases shared between human and non-human animals—are often significant and costly, in both the loss of human lives and impacts to the global economy. There are so many zoonoses that I could spend the rest of this blog playing “name that zoonotic disease” as I write out the 1,600 or so diseases that humans share with animals: many of which are emerging within human populations.

I might start the list with diseases like avian influenza and swine flu. Then I could mention the zoonotic viruses Ebola and monkeypox. These two viruses are extremely important, but for some reason feel exotic to people in the United States, even though people have tested positive to both while on US soil. One person even died of Ebola in a hospital in Texas in 2014. I might then list the oldest known zoonotic disease—rabies—and consider the fear it instills with the recent reminder following the tragic rabies related death of a child in Florida. Other zoonoses on the list may include West Nile virus, Sudden Acute Respiratory Syndrome (SARS), Middle Eastern Respiratory Syndrome (MERS), Zika virus, Q fever, and toxoplasmosis. The list would go on and on. In our globally connected world, any one of these diseases could show up anywhere on the planet, from Alabama to Zimbabwe. The often-cited statistics that 75% of human emerging infectious diseases (EIDs) are zoonotic and that 70% of these have a wildlife reservoir should be of interest to anyone that cares about human health. But, what about the other side of the equation? Do animals get infected with pathogens transmitted from people?

Human to Animal Pathogen Transmission

The simple answer is yes. Humans can and do transmit pathogens to non-human animals. Some call these diseases anthropozoonoses to reflect the human (anthro) to animal (zoonosis) direction of the transmission. However, I am much more comfortable to call these diseases zoonoses. The term zoonotic should include the diseases from non-human animals to humans AND from humans to non-human animals. Zoonoses may be bi-directional. However, even with all the current news on human EIDs and their zoonotic link, we rarely hear about pathogens that humans transmit to non-human animals.  

In a recent study ( ), we looked at the other side of the zoonoses equation and sought to determine if humans transmit pathogens to our great ape relatives. In the paper entitled “Pathogen Transmission From Humans to Great Apes is a Growing Threat to Primate Conservation” we provide data from a meta-analysis (a review!) of the scientific literature on great ape infectious diseases acquired from humans. We looked at great apes living in captivity, semi-free living conditions (such as great apes habituated for ecotourism) and free-living. We found 33 individual occurrences of probable or confirmed pathogen transmission from humans to great apes during the period 1964-2012. Occurrences were found in great apes in captive (n = 7), semi-free-living (n = 25), and free-living (n = 3) conditions, with two occurrences affecting populations in both semi-free-living and free living conditions. The majority of occurrences involved chimpanzees (Pan troglodytes) (n = 23) and mountain gorillas (Gorilla beringei beringei) (n = 8). This may reflect a larger amount of research with these species or possibly higher human to chimp and human to mountain gorilla contact.


One thing is for sure, these 33 events are just the tip of the iceberg since we know many disease events in great apes go undocumented and never reach the scientific literature. For example, I am personally aware of two zoonotic disease outbreaks: chickenpox from a keeper to gorillas in a zoo in the U.K. and polio in chimps at a zoo in the Republic of Congo. You will not find either of these events reported in the literature, but there is no doubt that both were caused by human to non-human great ape pathogen transmission. How many more stories like this are out there?


Six great ape species are endangered or critically endangered as determined by the International Union for the Conservation of Nature (IUCN). All six are experiencing decreasing population trends. (In fact, Homo sapiens [yes - us!] is the only species of the seven within the Hominidae family that is having population increases and is not endangered.) Our review shows that zoonotic pathogens transmitted from humans to our non-human Hominidae relatives may be a significant, but unappreciated, issue. We must work to better understand these zoonoses if we are to prevent human caused disease events from further threatening our closest living relatives.  

Work Cited

Dunay, E, Apakupakul, K, Leard, S, Palmer, JL, Deem, SL. 2018. Pathogen Transmission From Humans to Great Apes is a Growing Threat to Primate Conservation. EcoHealth. 1-15.

A Piece of Pie

This past week the family and I drove to Washington DC for our yearly Thanksgiving pilgrimage.  Of course this year it was difficult to turn the radio on without finding any news not covering some horrible thing going on around the globe.  Listening, we pondered the suffering of the people in Aleppo to pipelines being laid in the USA to various political shenanigans: all seemly moving the dial further away from a healthy and happy planet.  But during all these stories, my thoughts largely focused on food.  I suppose that wasn’t so different from most people in America this time of year as we consider how to prepare, serve, and store food; as well as how not to eat too much of it.  But my thoughts on food may have been slightly different.  I kept coming back to the link that food has to the many conservation and public health challenges of today. 

Conservation and public health

As our species, Homo sapiens, approaches 7.6 billion with approximately 150,000 additional humans added each day, it is worth considering how to feed all of us.  (To more closely consider these numbers and if you really want a scare, check out the website  Even though most of us realize we haven’t figured out how to feed all 7.6 billion of us well, with many of us not getting enough calories and an increasing number getting too many calories; both presenting significant public health challenges, we need to ask what the costs are to the planet as we attempt to feed our species.

With 38% of the arable land on Earth used to produce food for one species—humans—we see there is little real estate left for the other animals that share our world.  And this 38% is just the land dedicated to agriculture and does not factor in the amount of animal protein we harvest from the oceans.  It is now thought that 70% of the world fisheries are fully exploited, over exploited, or significantly depleted.  Further, to add insult to injury, we also know that the illegal and legal trade in wildlife has become a worldwide enterprise with numbers hard to quantify, and frankly harder to comprehend.  For example, it is estimated that animals taken from the forests of the Congo Basin of Africa (just this one area) and used to feed Homo sapiens equates to 5 million tons of bushmeat!  This number is a conservation and public health double whammy crisis.  These 5 million tons represent both declining wildlife populations and a disease threat for all life since the animals may act as “pathogen packages” as they, and all the microbes they harbor, are sliced and diced and shipped around the globe. 

So who shares the planet?

If one considers the changing composition of the vertebrate biomass (the total mass of organisms that have backbones) during recent history, we can start to understand why food, conservation, and public health fit together in one blog.  Let’s begin 10,000 years ago when humans were just starting to be successful in both domesticating animals and in getting pretty darn serious about going forth to multiple.  For the first time we convinced that wolf to sit down next to the village campfire or that wild bovine to become more sedentary and hang out in our fields.   If we think of it as a pie, what does it look like?  The pie of 10,000 years ago had a 2% slice which held all the humans a live at that time (< 10 million) and the few animals we had just domesticated.  The other 98% of the pie would be all those other vertebrate species we think of as wild creatures: the lions and tigers and bears…  Now if we look at that same pie today, the slices flip flop with 2% representing all the “other animals” that are categorized as neither humans nor domestic animals.  The humans and domestic animals now take up the other 98% of the pie.  Wow!   That 98% has the 7.6 billion humans along with all the dogs and cats and other companion animals we invite into our homes.  It also contains the 19 billion chickens; 2 billion pigs; 1 billion sheep; 990 million cattle; 450 million goats; and15 million camels alive on Earth today and waiting to become human food.  Of course these numbers do not reflect the same individuals for many days as the animals come and go quickly to help feed our increasingly hungry human population.  

What about that other 2% of the pie in 2016?  In Saint Louis, Missouri where I currently live, we have the Busch Stadium: home of the St Louis Cardinal Baseball team.   This one stadium in this one small-ish town, seats roughly 44,000 people and the baseball team itself has about 44 players.  These are the same numbers of all the Asian elephants—44,000—and all the Amur leopards—44—that remain on Earth today.  And elephants and leopards are just two examples of the thousands and thousands of animal species threatened with extinction.      

What can you do? 

I had a great Thanksgiving week with family and friends and a great deal of food and drink.  I enjoyed myself immensely and must admit I did not hold back too much.  But, I also was thankful while thinking of both the people in Aleppo and the elephants in Asia and what they did, or did not have to eat this past week.  It got me thinking about the resources necessary to keep our very successful species well-fed and healthy, without eating ourselves sick or our planet-mates into extinction.   

Every day we have the power to make the right food choices.  The foods we eat, both quantity and quality, do have real-world impacts on the planet.  Cows, and not cars, may now be one of the biggest contributors to our climate worries!  For each pound of beef we consume, it takes 2,500 gallons of water, 12 pounds of grain, and 35 pounds of topsoil to produce it.  We also know that on average each cow on the planet will produce 150 – 265 pounds of methane (a top green-house gas).  If we simply cut back on animal protein consumption and ate lower on the food chain, it would help.  Or maybe we should minimize the distance food travels to get to our plates.  The CO2 cost from the transport of food from points A to B to C exerts a high price on planetary health.  Why not eat foods produced closer to home?  And with the obesity epidemic now one of the biggest public health challenges of today, just slowing down on how many groceries “go in” would do a world of good for your health and the health of the planet.  We can all still enjoy a piece of pie now and again, but maybe we should be thinking just a little bit more about the food on our plates and the ripple effects it has on our health and the health of the planet.