Zoonoses Are Diseases That Jump from Animals to Humans
- A zoonosis is an infectious disease that can be transmitted from animals to humans.
- These diseases are not rare.
- In fact, over 60% of infectious diseases in humans are zoonotic.
- These diseases originate in wild or domesticated animals and can spread to humans through direct contact, contaminated food or water, insect bites, or respiratory droplets.
Definition
Zoonoses
Zoonoses are infectious diseases that are naturally transmitted between animals and humans.
How Zoonoses Spread
Zoonotic diseases can spread through various pathways, including:
- Direct Contact: Touching an infected animal or its bodily fluids (e.g., saliva, blood).
- Indirect Contact: Exposure to contaminated environments, such as soil or water.
- Vector-Borne Transmission: Being bitten by an insect (e.g., mosquito, tick) that carries the pathogen.
- Foodborne Transmission: Consuming contaminated food or water.
1. Tuberculosis (TB)
- Pathogen: Mycobacterium tuberculosis (human TB), Mycobacterium bovis (bovine TB)
- Animal Hosts: Cattle, deer
- Transmission:
- Inhalation of infected droplets from cows
- Consumption of unpasteurized milk
- Contact with infected animals
Pasteurization of milk has significantly reduced TB transmission in many countries.
2. Rabies
- Pathogen: Lyssavirus
- Animal Hosts: Dogs, bats, raccoons
- Transmission to Humans:
- Bites or scratches from infected animals
- Contact with saliva through eyes, mouth, or open wounds
- Rabies is almost always fatal once symptoms appear.
- Immediate vaccination after exposure is critical.
3. Japanese Encephalitis
- Pathogen: Japanese encephalitis virus (JEV)
- Animal Hosts: Pigs, birds
- Transmission to Humans:
- Mosquito bites (mosquitoes become infected by biting animals like pigs)
Vaccination is the most effective way to prevent Japanese encephalitis, especially in endemic areas.
4. COVID-19
- Pathogen: SARS-CoV-2
- Animal Hosts: Likely originated in bats, with an intermediate host (e.g., pangolins)
- Transmission to Humans:
- Respiratory droplets and aerosols
- Direct or indirect contact with infected surfaces
- The first cases were linked to a wildlife market in Wuhan, China with over 6 million deaths globally (as of 2023).
- Rapid human-to-human transmission led to a global pandemic.
- How did the interconnectedness of global travel and trade amplify the spread of COVID-19?
- Consider the role of human behavior in zoonotic pandemics.
Why Are Zoonoses So Prevalent?
- Close Contact with Animals: Farming, hunting, and pet ownership increase exposure.
- Environmental Changes: Deforestation and urbanization disrupt wildlife habitats, forcing animals into closer contact with humans.
- Globalization: Trade and travel facilitate the rapid spread of diseases across borders.
- Climate Change: Alters ecosystems, expanding the range of vectors like mosquitoes.
- How do cultural practices, such as wet markets or traditional medicine, influence the emergence of zoonotic diseases?
- Should these practices be regulated or preserved?
- How is tuberculosis transmitted from animals to humans?
- Which animals are reservoirs for Japanese encephalitis?
