emergence of zoonotic diseases is often associated with environmental changes or ecological disturbances, such as agricultural intensification and human settlement, or encroachments into forests and other habitats.5
Zoonoses are
also opportunistic and tend to affect hosts that are already stressed by environmental, social, or economic conditions.6
Zoonoses threaten economic development, animal and human well-being, and ecosystem integrity. Over the last few years, several emerging zoonotic diseases made world headlines as they caused, or threatened to cause, major pandemics. These include Ebola, bird flu, Middle East respiratory syndrome (MERS), Rift Valley fever, sudden acute respiratory syndrome (SARS), West Nile virus, and Zika virus disease. The pathogens causing these diseases have wildlife reservoirs that serve as their long-term hosts. In the last two decades, emerging diseases have had direct costs of more than US$100 billion; if these outbreaks had become human pandemics, the losses would have amounted to several trillion dollars.7
Pathogen flow at the wildlife–livestock–human interface Pathogen flow at the wildlife–livestock–human interface
Another important group of zoonotic diseases are caused by foodborne pathogens such as Salmonella and Listeria bacteria that are passed from animal to humans. In 2015, the first global assessment of foodborne disease found the overall burden of foodborne disease was comparable to malaria or tuberculosis.8
Emerging zoonotic disease
Emerging zoonotic diseases are those that newly appear in a population or have existed previously but are now rapidly increasing in incidence or geographical range. Fortunately, most new diseases are not highly lethal and most do not spread widely. But some emerging diseases have enormous impacts. Human immune deficiency virus (HIV and AIDS), highly pathogenic avian influenza (bird flu), bovine spongiform encephalopathy (mad cow disease), and Ebola are well-known examples of particularly harmful emerging zoonoses.
Epidemic zoonoses Biosphere Wildlife
Outbreaks of epidemic zoonoses typically occur intermittently. Epidemic zoonoses are often triggered by events such as climate changes, flooding and other climate events, and famines. Their overall health burden is much less than that of endemic zoonoses but because they cause ‘shocks’ to food production and other systems, they can reduce the resilience of the affected communities. Examples are anthrax, rabies, Rift Valley fever, and leishmaniasis.
Peri-domestic Wildlife
Neglected zoonotic diseases Humans Livestock Domestic landscape Source: Jones et al. (2013)5
Neglected zoonotic diseases are continually present to a greater or lesser degree in certain populations, but are often marginalised by health systems at national and international levels. Examples are anthrax, brucellosis, cysticercosis (pig tapeworm), echinococcosis (hydatid disease), Japanese encephalitis, leishmaniasis, leptospirosis, Q fever, rabies, foodborne trematodiases, trypanosomiasis and cattle tuberculosis.
Source: Jones et al. (2013)5 19
UNEP FRONTIERS 2016 REPORT
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