Factors in the Emergence of Viral Zoonoses (Essay Sample)

Factors in the Emergence of Viral Zoonoses
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Factors in the Emergence of Viral Zoonoses
A great number of studies and literature show that zoonotic infections are the leading cause of emerging infectious diseases in humans. The potential threat to health posed by zoonotic diseases range from mild to fatal, with grave economic impact due to the widespread nature of such infections. Emerging diseases are not new to humans, and are described by the World Health Organization as caused by pathogens appearing in a population for the first time, or existing previously but with increased incidence or increase in geographic range (WHO 2004). The concept of emerging diseases may however also refer to reemerging diseases that initially had reducing incidence or spread but currently show an increase in incidence due to factors such as poor public health measures or growing resistance to antimicrobials. From an array of literature concerning zonooses, it is believed that approximately an eighth of all known human pathogens are emerging while about 75% of these are considered zoonotic. The emergence of viral zoonoses is influenced by constantly changing environmental factors associated with the causative pathogens and their reservoir hosts (Calisher et al. 2006, p.540; Wang, Walker, & Poon 2011, p.7).
While zoonotic infections are not new, there are great risks of new strains of these infections emerging in humans. The number of emerging infectious diseases has risen considerably over the last 30 years with over three quarters of the number being zoonotic (Wang & Crameri 2014, p.569). The most common over the years have been diseases such as anthrax, influenza, yellow fever, tuberculosis, and plague, all of which originate from livestock, poultry, and other domestic animals (Keesing et al. 2010, p.647). Changes in environment and human activities have however been a significant contributor to the emergence of infections from wild animals. Such changes include the modernization of farming practices, principally in developing countries, destruction of natural habitat through human encroachment, and climate change. The contact between humans and wild game through these changes remains the chief cause of emerging infections among humans. There are agricultural factors that drive the emergence of viral zoonoses, which as aforementioned include changes in agricultural practices, particularly the modernization, and the intensification of farming practices (Jones 2013, p.8401). The effect of human encroachment into wild reserves for the purpose of acquiring more land for farming and grazing is the overlapping of livestock and wildlife territories. This facilitates the transmission of novel agents causing infections in naïve species. Bush meat is one particular causative agent of emerging infections among cultures that practice hunting as a source of food. The risk of transmission is even further increased if this meat is shipped to centralized markets (Marsh et al. 2011, p.S805; Morse 2006, p.8).
Climate and changes in habitat are the other factors that contribute to the emergence of viral zoonoses. These factors have a significant effect on vector distribution. Change in climate has the effect of necessitating change in habitat, which implies the introduction of previously geographically limited pathogens to venture into naïve and susceptible populations of humans and animals. Emergent viral zoonoses under such settings are the West Nile virus (WNV), dengue virus, and the chikungunya virus (CHIKV), all of which have increased their geographical ranges into new established habitat, causing the interaction of initially isolated vectors and introducing agents to the new vectors (Wang & Crameri 2014, p.570; Suthar, Diamond, & Gale 2013, p.117). The risk of emergence of the zoonotic agents therefore depends on the diversity of wildlife microbes in a specific region (the zoonotic pool), the impact of environmental change on the incidence of pathogens amongst wild populations, and the frequency and extent of contact between, humans and domestic animals with wildlife habitat with potential zoonoses (Wolfe et al. 2005, p.1822).
The poster is a representation of the likely causative agents of zoonotic infections, both from wild animals and domesticated one. It then provides a list of selected viruses and the factors that influence their spread and emergence in populations. A connection in the diagram is made between humans and animals through vectors. The poster may therefore be an easy form of education to enlighten people about the full scale if emergent diseases.
List of References
Calisher, C. H., Childs, J. E., Field, H. E., Holmes, K. V., & Schountz, T., 2006, Bats: Important Reservoir Hosts of Emerging Viruses. Clinical Microbiology Reviews, vol. 19(3) 531–545.
Jones B. A., Grace, D., Kock, R., Alonso, S., Rushton, J., Said, M. Y., McKeever, D., Mutua, F., Young, J...