Zoonotic Spillover in an Era of Rapid Deforestation of Tropical Areas and Unprecedented Wildlife Trafficking: Into the Wild

Abstract

Rapid deforestation and unprecedented wildlife trafficking are important factors triggering the rate of zoonotic spillover from animals to humans. Consequently, this leads to the emergence and re-emergence of zoonotic infectious diseases among the human population. Deforestation is an important ecological disruption that leads to the loss of biodiversity. The loss of biodiversity results in the persistence of highest-quality hosts of zoonotic pathogens dominating the low-diversity communities, a process termed the dilution effect. Activities like intensive farming and logging that resulted in deforestation bring vulnerable people in close contact with these highest-quality reservoir hosts (wildlife). As a result of this vulnerability, there is an increased risk of spillover, leading to zoonotic infection in humans and eventually disease outbreaks during human–human transmission. One prominent example of a disease of wildlife origin is the ongoing SARS-CoV-2 (Severe Acute Respiratory Syndrome-Coronavirus 2), even though the original source has not been found. Another important factor facilitating the risk of spillover and emergence of zoonotic infectious diseases is wildlife trafficking. This involves illegal hunting and trading of wildlife and their products, which increases the risk of spillover as a result of exchange of bodily fluids and bloodmeals between humans and wildlife during the hunting and butchering of animals’ carcasses. Consequently, little or no hygiene protocol and poor handling practices during the wildlife-trade chain expose poachers, consumers, and local market sellers to the risk of zoonotic diseases. Despite the interventions on deforestation-induced spillover and wildlife trafficking-associated spillover, there are still knowledge and research gaps that need to be addressed towards preventing the outbreaks of future zoonotic infectious diseases. In response to this, there is a need for interdisciplinary and intersectoral collaborations among researchers from various fields as well as sectors in minimizing the risk of zoonotic spillover driven by deforestation and wildlife trafficking at the human–animal–environmental nexus. In addition, there is a need for integrated and unified evidence-based policy formulation that puts an end to deforestation and wildlife trafficking, especially in tropical areas such as Africa and Asia.