The spread of disease from animal to human is no new phenomenon; the bubonic plague spread through rat fleas, Rabies normally transfers through animal bites and Ebola has commonly been linked to bats. It’s called zoonosis: when a disease from an infected animal population spills over to humans.
But pathogens can spread both ways. Humans can pass diseases to animals, too (called anthropozoonosis).
Cryptosporidiosis, commonly called Crypto, is one such disease taking a particular toll on chimpanzees within Gombe Stream National Park in Tanzania. A thorough analysis of the epidemiology of cryptosporidium – the parasite that causes Crypto – recently published in PLOS One, reveals the complexities of disease transmission in the Gombe ecosystem. The discovery could have broader implications on wildlife and chimpanzee conservation models.
Dominic Travis, D.V.M., M.S., associate professor with the College of Veterinary Medicine collaborated with a group of researchers to study the spread of cryptosporidium in humans, domesticated animals and primates in the Gombe ecosystem. Gombe National Stream Park is where Jane Goodall conducted her primate studies. Researchers from Emory University, the Center for Disease Control and Prevention, The Jane Goodall Institute, the Institute of Parasite Disease Prevention and Control, and Franklin and Marshall College contributed to the study.
The team found three different strains of cryptosporidium in the area. The humans and half the primates infected with Crypto had the parasite strain C. hominis, most commonly associated with humans. According to Travis, researchers were unsure from which direction and environment the strain originated.
The other half of the primates tested positive for C. suis, which is linked to domesticated pigs. However, there are no domesticated pigs in the area, leading researchers to believe the strain was spread through bushpigs in a wild-wild cycle.
A third independent strain, C. xiaoi, was found in domestic goats and sheep.
“Finding two different strains of Crypto occurring in the primate population illustrates the interconnectedness of health,” Travis said. “We expected to find Crypto spreading by human interaction on the edge of the forest, but the addition of C. suis shows that there are more factors at play. This is a much messier problem.”
In humans, Crypto causes moderate to severe diarrhea, cramping, dehydration and nausea. For primates, it can be deadly.
“This is a serious concern for the chimpanzees,” Travis said. “There are only about 100 chimpanzees in this region, so a disease like Crypto could cause a perfect storm of mortality events, especially if paired with the animal equivalent of AIDS.”
Typically, wildlife conservationists only address problems brought to ecosystems by human interaction, but preservation efforts are trickier than that. This study shows both naturally occurring forces and human interactions are affecting the health of wildlife in the Gombe ecosystem.
“Health supersedes boundaries,” Travis said. “Everything is connected. We need to understand the threats to the shared sustainability of wildlife and humans in these areas in order to find a way to help both.”
Travis and his team will continue to study these risks, outcomes, and interventions through the Gombe Ecosystem Health Project, an ongoing project assessing the health of the people and wildlife in the region. With further research, he hopes to find solutions to help minimize the risk of human-related Crypto as well as other threats to the primates’ health.
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