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Wildlife Zoonotics: Whose fault is it anyway?

Global incidences of disease outbreaks such as Ebola, SARS, Avian influenza, etc., are increasing with over sixty percent of infectious human diseases being of zoonotic or animal origin. Human infections and fatalities occur only when zoonotic pathogens spill over from animals, upon attainment of certain specific parameters. In most cases animals, including wildlife, act as reservoirs of these pathogens are are not necessarily affected by the disease. Consequently, one would feel that animals are responsible for this disease transmission. But again, are we looking into this matter in its entirety?

Wild animals have long been associated with disease transmission to humans. Ancient literatures even suggest that Alexander the Great died of encephalitis, hypothesized to have been caused by West Nile Virus spread by wild birds – ravens in this case. This essentially makes wild animals a major threat to public health. So what about the threat humans have imposed upon wildlife? Unprecedented habitat alteration, poaching, wildlife trade, consumption of illegal bushmeat top the list. By doing all these, we have unknowingly augmented our own chances of contact, and in turn, disease transmission from wildlife.

An example of human activities that led to the facilitation of disease spillover is the Hendra virus related human fatality in Australia. Studies theorize that this peculiar event occurred when breeding bats – reservoirs of Hendra virus -- moved into urban areas due to loss of natural habitat. Breeding bats are also more susceptible to diseases due to low immunity and nutritional stress. These bats, in turn, spread the disease to horses – a species highly affected by the virus. Human fatalities recorded were due to contact with horses. In the end, a chain of events triggered by humans is leading to an indiscriminate persecution of bats. Unfortunately there are other wild species including hyenas, jackals, civets, leopards and rodents that sail in the same boat.

But the question is - whose fault is it anyway?