70 Human Factors

Throughout history, humans have evolved to better suit our environment. Like all other species, individuals with favorable traits survived to pass on their genetic traits to future generations, using selection to drive changes across our population. Only recently, advancements in communication, accumulation of knowledge, and innovation of new technologies have allowed us to flip the known process of evolution. We no longer change to fit into the environment that surrounds us – we change our environment to make our lives easier and more comfortable, prioritizing our short-term needs and overlooking potential long-term consequences. (NC)

Two of the effects of human advancement on the prevalence of vector borne disease have already been discussed – increasing human population and the resultant need for space and resources have caused human populations to encroach on wild places and increase exposure to disease-carrying animals, and climate change, a direct result of human industrial activity, has increased the population and distribution of disease-carrying vectors. (NC)

The technological innovation of society has also allowed us to be closer to one another than ever before. Phones allow us to call friends and family on the other side of the country, social media lets us connect with strangers, and airplanes and cargo ships allow materials to be transported across the globe, from country to country. This increased interconnectedness brings benefits to our societies, allowing us to obtain materials we cannot efficiently produce or natural resources that we simply don’t have in our own countries. It can also pose risks to the global population, allowing the transport of diseases or disease-carrying species between countries. (NC)

The import of wild and livestock animals is a great example of the trade-off between economic benefits and potential health risks we accept when we choose to trade living organisms. Every year, the United States, the world’s largest importer of wild animals, receives tens of millions of live animal shipments (Nijman, 2021). Between 2000 and 2004, the US imported over one billion individual animals (Pavlin et. al. 2009). These animals are mostly destined for commercial use (pet stores, livestock, etc.) or for biomedical research. Imported animals from a wide variety of species are capable of carrying risk zoonoses. Infected animals can endanger workers who encounter them during export, shipping, and import. Disease carrying individuals can also infect animals they encounter at their final destination, including livestock on farms or pets in pet stores. This contact can have serious economic and health consequences in the country that receives the diseased animals. Shipping can keep high densities of animals in unnatural groupsings, providing opportunities for disease mutation and cross-species transmission, further increasing the risks associated with animal transport (Pavlin et. al., 2009). (NC)

These risks can also be found in wildlife markets. Markets, both legal and illegal, often contain a lack of hygienic conditions, such as hand washing, sanitation, and separation of wildlife and their parts. While illegal markets can often contain animals with higher chances of carrying zoonotic diseases, legal markets make up a significantly larger proportion of the global wildlife trade. Thus, both provide avenues for diseases to be transmitted across the world (Nijman, 2021). (NC)

Between 2000 and 2005, rabies, anthrax, and tuberculosis were the most commonly identified risk zoonoses imported into the United States (Pavlin et. al., 2009). With high potential for these pathogens to cause outbreaks from wild animal import, it is important to have high levels of surveillance for zoonotic diseases at vulnerable trading points. Unfortunately, the United States has no laws specifically requiring disease surveillance for imported wildlife (Nijman, 2021). Because of this, detection of zoonotic disease may not be reported properly, and infected animals, animals that they came into contact with, and animals at the origin point may not be properly dealt with. Currently, quarantine is required only for wild birds, primates, and some hoofed mammal species upon import to the United States. Mandatory testing only exists for a select few diseases, including avian influenza (Pavlin et. al., 2009). Even if regulations were to become more stringent to protect against zoonotic spread during wild animal trade, it is uncertain that current agencies could conduct the testing necessary to protect Americans. Of the tens of millions of live animal shipments imported into the US, only about 150,000 were inspected by the US Fish and Wildlife Service. The majority of these inspections came at the suspicion of violation of the endangered species act and were not an action towards preventative zoonotic surveillance (Pavlin et. al., 2009). Although the wild animal trade can be beneficial to our society, more needs to be done to ensure that the risks of zoonotic disease transmission are mitigated. (NC)