Arguably one of the greatest threats to human health comes from zoonotic diseases, those that can jump between animals and humans. In fact, 75% of new human diseases identified in the last three decades are zoonotic.
The recent outbreak of Mpox, a virus that can be transmitted from rodents and primates, in South Africa, Nigeria, and the DRC, has again highlighted the crucial need for awareness. This comes swiftly after COVID-19 brought the world to a halt, a zoonotic disease thought to have originated in bats and probably spread to humans from raccoon dogs on sale as bushmeat.
Emerging infectious diseases are on the rise. Biodiversity loss, the extinction of species or a significant reduction in population sizes, has been identified as a major driver of outbreaks. A recent metaanalysis covering 1,000 studies made this clear.
Habitat loss, the degradation and destruction of natural ecosystems, while itself not linked to infectious disease outbreaks in the analysis, contributes to biodiversity loss and is caused by agricultural expansion, logging, mining, livestock grazing, and population growth. Deforestation, even of select species of trees, can have knock-on effects, as seen in Uganda, where the cutting of palm trees caused changes in animal diets.
Linus Unah, West Africa Director at Wild Africa, highlights the impact of zoonotic diseases causing 2.5 billion cases of illness and 2.7 million deaths worldwide each year. But this goes further than health, he argues.
“Zoonotic diseases, brought about by biodiversity loss and harmful practices within the bushmeat trade, have far-reaching economic consequences, too. In 2015 for example the Ebola epidemic cost countries, like Guinea, Liberia, and Sierra Leone estimated losses of US$1.6 billion in forgone economic growth, according to the World Bank.”
The public needs to better understand how these diseases can be spread. The greatest transmission risk occurs when humans and animals, both wild and domestic, interact in close proximity. Humans are at risk when exposed to infected live animals or livestock products, such as meat, milk, and eggs.
The bushmeat trade poses several risks as it can involve exposure to pathogens carried in wild animals, often in poor health from immense stress, poor diet, dehydration and poor hygiene in the transport and handling process. Widespread bushmeat trade networks can spread pathogens over large areas and habitat disruption increases the likelihood of exposure to never-before encountered pathogens.
Zoonosis infographic
While up to 200 zoonotic diseases exist, these have recently come to attention:
- Mpox: Similar to smallpox but less severe, it can be transmitted to humans from various wild animals, including rodents and primates.
- COVID-19: COVID-19 is caused by a Coronavirus, specifically SARS-CoV-2. SARS-CoV-2 is thought to have originally come from bats and possibly transmitted to civets or raccoon dogs, then to humans.
- Anthrax: Spores can be found in soil and infect herbivorous animals, including wild game, which can then transmit the bacteria to humans.
- Lassa Fever: Spread by rodents, specifically the Natal multimammate mouse, common in West Africa.
- Ebola Virus Disease: Primarily transmitted to people from wild animals, such as fruit bats, chimpanzees, gorillas, and monkeys.
- HIV/AIDS: Believed to have originated from the simian immunodeficiency virus (SIV) found in chimpanzees and sooty mangabey monkeys.
- Marburg Virus Disease: Similar to Ebola, Marburg virus is linked to fruit bats and can cause severe hemorrhagic fever.
- Yellow Fever: Transmitted by mosquitoes, it can spread from monkeys in the jungle to humans.
- Zika Virus: Also spread by mosquitoes, it can be transmitted between monkeys and humans.
- Bird Flu: As the name suggests, the highly pathogenic H5N1 bird flu comes from birds – both domestic and wild, like seagulls and cormorants.
“Collaboration across governments, NGOs, and society at large is crucial to combat new outbreaks,” continues Unah.
“Governments need to be prepared and ready for pandemics, but we also need to address the root causes of these new diseases, which is our behaviour towards nature. If we protected and respected wildlife and their habitats, the risks would be much lower. By keeping wildlife wild, we really are keeping ourselves safe. Protecting nature protects us all,” he adds.
