Scientists have confirmed the first occurrences of leprosy in wild chimpanzees, a bacterial disease that usually affects humans. Although it is unclear how the chimps contracted the virus, researchers believe the findings indicate that leprosy is considerably more prevalent in chimps and other wild animals than previously thought. The findings were published in the journal Nature by an international team of researchers from West Africa, Europe, and the United States. The findings were previously released as a preprint in November 2020, which was covered by IFLScience, but they have since been peer-reviewed and confirmed.
The leprosy cases were discovered in two wild populations of western chimps (Pan Troglodyte’s verus) in Guinea-Cantanhez Bissau’s National Park and Côte d’Ivoire’s Ta National Park, separated by 1,000 kilometers (621 miles).
The outbreaks were first discovered thanks to hidden camera traps placed throughout the Cantanhez National Park, which revealed that at least four wild chimps had developed unusual lesions on their faces, ears, hands, and feet, as well as hair loss and a loss of pigment in their faces, symptoms that were strikingly similar to those seen in humans with leprosy. Similar symptoms eventually discovered chimps from a completely different group at the Ta National Park in Côte d’Ivoire.
Surprised by these findings, scientists used genetic research to corroborate their assumptions. The researchers took stool samples and found Mycobacterium leprae, the germ that causes leprosy. The germs were also discovered in a necropsy sample taken from an adult female named Zora who was killed by a leopard in Ta National Park in 2009.
The M. leprae bacteria recovered from the excrement samples subjected to further genetic research, which yielded some interesting results. To begin with, the two epidemics had two different strains, indicating that they arose independently. Second, the genotypes of the bacterial strain responsible for both outbreaks are highly uncommon in humans, implying that the outbreak did not begin with human interaction.
Previous incidences of leprosy in captive chimps have been documented, but this is the first time the illness has been confirmed in wild chimp communities. Squirrels and armadillos are among the wild creatures that have been documented to affect them. All of this raises the question of how they contracted the sickness. “We still don’t know a lot of things! Dr. Kim Hockings, the lead study author from the University of Exeter’s Centre for Ecology and Conservation, told IFLScience, “This is very surprising considering how ancient this disease is and the decades that it has impacted people.”
Human contact with chimps is unusual in Cantanhez and Ta National Parks, according to Dr. Hockings. M. leprae is also assumed to be spread by humans with evident signs, however, no cases of leprosy have been reported among researchers or local research assistants. “Although a human source cannot be ruled out,” Dr. Hockings stated, “poor human contact combined with the rarity of the M. leprae genotype discovered in TNP [Ta National Park] chimpanzees among human groups in West Africa suggests that recent human-to-chimp transmission is improbable.”
The researchers believe the chimps were more likely to expose to germs through their mammalian prey. Alternatively, because M. leprae can survive in soil and some other mycobacteria can survive in water, it is plausible that the chimps contracted the infection in their natural habitat. It is also unclear how chimps will be affected in the end by this sickness. This is partly because leprosy is a slow-moving illness that takes a long time to manifest in its patient. In Cantanhez, for example, a female chimpanzee showed early signs of leprosy in 2013, but she is still alive and part of her chimp community.
Nonetheless, Western chimps are facing extinction owing to a variety of human-caused challenges and the last thing they need is another sickness to worry, about.
Dr. Hockings stated, “This is just one of the many stressors that wild chimps and other species are presently facing.” “It’s plausible that people who are stressed are more prone to develop leprosy, whether from human and environmental stressors in their natural surroundings or through invasive treatments in biomedical institutions, for example.” My future studies will go deeper into this.”