Diseases that can jump species are an increasingly concerning issue.
Arguably one of the greatest threats to human health comes from zoonotic diseases – those that can jump between animals and humans. Some 75% of new human diseases identified in the last three decades are zoonotic.
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 meta-analysis 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 agriculture, logging, mining, livestock grazing, and population growth.
Zoonotic diseases cause 2.5 billion cases of illness and 2.7 million deaths worldwide annually. But this goes further than health. 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 an estimated R21 billion in 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.
Ones to Watch
While up to 200 zoonotic diseases exist, the following 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: Caused by the coronavirus SARS-CoV-2, which 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: The highly pathogenic H5N1 bird flu comes from birds – both domestic and wild.
Text | Linus Unah
Photography | PERO studio
Linus Unah is West Africa Director at Wild Africa. For more information, go to wildafrica.org.
