By Jake Smith
The fever, general weakness, and headache that start off the infection are only harbingers of what is to come. Soon, vomiting and diarrhea set in, followed by unexplained bleeding and, in many cases, death. Ebola virus is the subject of much recent attention. The 2014-2015 outbreak of the virus, occurring largely in the African countries of Guinea, Sierra Leone, and Liberia, has infected over 28,000 people and caused over 11,000 deaths. But could the outbreak have been prevented?
As humans encroach on the territory of lemurs in Madagascar, transmission of diseases between humans and lemurs, and vice versa, can occur.
“Milne-Edwards’ sifaka (Propithecus edwardsi) in the Ranomafana National Park, Madagascar” by Brian Gratwicke is licensed under CC 2.0
Although researchers continue to investigate Ebola virus’s natural reservoir – the animal host in which the virus primarily resides – the origin of human cases can likely be attributed to contact with an infected animal, such as a bat or primate. Research by Deanna Bublitz, of Stony Brook University, in the journal American Journal of Primatology suggests that ecological disruption and land use change, specifically the breaking up of forest habitats, could potentially lead to outbreaks of infectious diseases such as several forms of diarrhea, and even Ebola, in humans. Thus, human encroachment on wildlife not only impacts nonhuman species, but humans themselves.
By determining the presence of six bacteria that commonly cause human illness in lemurs living in Madagascar’s Ranomafana National Park, Bublitz found something astonishing: the only lemurs that tested positive for those six bacteria were found in disturbed areas of the park. Lemurs in undisturbed areas showed no signs of harboring these potentially deadly germs. Thomas Gillespie, another author on the study, says, “Any time we alter a pristine natural system there are going to be unintended consequences.” In other words, we may never know when journeying into a new landscape will lead to a germ making its jump from a nonhuman species to our very own, or the other way around.
Perhaps unsurprisingly, nonhuman primates, such as lemurs, provide suitable intermediates between animal hosts and humans for bacterial and viral organisms. The genetic similarity of nonhuman primates and humans makes these primates important in the transmission of several pathogens as human-nonhuman primate interactions increase. The act of cutting down a tree may, unwittingly, cause a human infection.
Furthermore, the extent of human-mediated changes to forest habitats correlates with higher transmission rates of diseases between species. The reason is simple: humans provide a means for viruses and bacteria to spread past previous niches, and pathogens such as Ebola virus, E. coli, and the parasite causing malaria take advantage of this opportunity. We become the breeding ground for malicious microorganisms.
With the world becoming more developed as a whole, the ability of infectious diseases to spread will likely grow. If forested areas are destroyed, species of primates (and other animals) will be lost, potentially resulting in a strong pressure for parasites to infect other organisms – humans – in close proximity. Human occupation of wild areas results in the loss of local flora and fauna and replacement with an environment ripe for disease transmission.
However, several things can be done from a conservation standpoint in order to mitigate the impact of infectious illnesses on society. Protecting nonhuman primates and other species, designing housing developments such that they do not impinge on wild habitats, and restricting access to wildlife may decrease the spread of infectious illnesses, as well as protect habitat and species diversity.
Of course, encroachment on habitats is not the only cause of the introduction of infectious illnesses, and something as simple as restricting access to wildlife cannot fully limit negative human-nonhuman species interactions. Furthermore, disease outbreaks should not be used to mandate the abandonment of cultural practices or sustainable subsistence hunting. However, it is necessary to educate people in areas with particularly high risk of disease transmission about behaviors and lifestyle choices associated with developing infectious illnesses, along with the impacts of human activity on wildlife.
Conserving species diversity and the habitats that maintain these species can be of help to both our species and the various other organisms with whom we share the earth. By keeping natural environments intact – and restoring those we have destroyed – we simultaneously protect ourselves from the havoc that obscure, deadly organisms can wreak.
And we can save the lemurs from the nasty diseases that we harbor, too.
Bublitz DC, Wright PC, Rasambainarivo FT, Arrigo-Nelson SJ, Bodager JR, Gillespie TR. 2015. Pathogenic enterobacteria in lemurs associated with anthropogenic disturbance. American Journal of Primatology 77:330-337.