Researchers Use Komodo Dragons to Better Understand the Microbial Health of Captive Animals

Humans and animals continue to evolve as their environments change. In recent years, more humans and animals are spending much of their time in enclosed artificial environments, and thus, limiting the amount of exposure to microbial organisms that they had previously been exposed to in more natural spaces. Given these environmental changes, the microbial organisms living on and inside the bodies of both humans and animals are undergoing changes as well, and scientists want to know what kind of health implications these changes may have.

A team of researchers from the University of California—San Diego, the University of Colorado–Boulder, the University of Chicago, and the US Department of Energy’s (DOE’s) Argonne National Laboratory recently came together to learn more about the potential health implications. In the first and largest study of its kind, researchers used captive Komodo dragons, the largest lizards in the world, to examine and make note of any similarities between how these dragons share microbes with their environment and how humans and their pets share microbes with their environment, according to a press release.

In the study, the researchers took saliva, skin, and feces samples from 37 Komodo dragons from 12 zoos across the United States, and environmental samples from 2 of the 12 enclosures. Through statistical analysis, the researchers compared the data taken from the dragon samples with the data from the environmental samples. In addition, they compared these new data with similar data from past studies of humans and their pets. In their analysis, the researchers found that, not only do captive Komodo dragons contribute microbes and other bacteria to their environment, but this “exchange” is “circular in nature.” This means that, the dragons contribute microbes into their enclosures and without any external sources to transfer any new microbes, the dragons receive the same microbes back from their environment, and then the cycle begins anew. This process is much like the way humans and pets interact with their own household environment.

In the press release, study author Jack Gilbert, PhD, director of The Microbiome Center, a joint Argonne, University of Chicago, and Marine Biological Laboratory program, commented, “Regardless of whether you’re in a closed or open environment, there’s always a constant exchange of microbes between a host and their environment, and that constant exposure has impacts on health; for example, it can lead to changes in a host’s immune system that help the host stave off pathogens.” He continued, “The problem is that the degree of exposure becomes limited when you put a host in captivity, and this change has unknown consequences on health, which is exactly why we’re trying to learn more about it.”

A number of past studies have also suggested this “hygiene hypothesis”—that an increase in autoimmune and allergic diseases in Westernized nations can be attributed to reduced exposure to microbes— according to the press release. The authors cite a study on desert woodrats as an example. When the woodrats were brought into captivity, and thus, an enclosed space with less external microbes, in just 6 months, they ended up losing 24% of their natural microbes. In another study with Atlantic cod, when given an artificial diet, researchers found the cod’s gut microbiome became less diverse than when they were fed their natural diet.

Much like with humans, without exposure to the variety of microbes that can be found in a more natural space, captive animals may actually be more prone to contract diseases that they otherwise may have developed immunity to if they were not living in such enclosed environments. Although they could have acquired some of these diseases in their natural habitats, due to captivity, the effects of these diseases may be more serious.

In the press release, Embriette Hyde, PhD, an assistant project scientist, project manager of the American Gut Project, and lead author of the study explained, “For some animals there are diseases that affect them but don’t affect their wild counterparts, or don’t affect their counterparts as severely, so it makes sense that people, as they spend less time outdoors, would be affected in the same ways.”

According to Dr. Gilbert, the research doesn’t end here; researchers are working on exploring this further in other animal models. In the press release, Dr. Gilbert said, “Since it’s quite difficult to track microbial exposure on a daily basis, especially with humans—who move around a lot—we’re exploring new animal models to see if we can ask the same questions we would about humans and get answers in more rigorous, controlled ways.”

With these findings, researchers hope to not only learn more about the microbial health of humans and captive animals, but also improve animal husbandry practices as well.