Zoonosis, C3.2.15

• What does it mean that pathogens are specialised?

  Pathogens are often highly specialised, as they have a narrow range of hosts.

  Humans are the only known organisms that are susceptible to the pathogens that cause polio, syphilis and measles.

  However, some pathogens can use more than one species as a host. For example, mycobacterium bovis causes tuberculosis in cattle and also badgers. The milk produced by infected cattle may contain live cells of mycobacterium bovis, which can cause tuberculosis in humans.
• What are the main routes of pathogen transmission?

  - Direct contact: Touching infected people or animals (e.g., skin infections, STIs).

  Indirect contact: Touching contaminated surfaces or objects (fomites).

  - Droplet transmission: Sneezing or coughing releases droplets that carry pathogens (e.g., flu).

  - Airborne transmission: Pathogens travel in air as small particles (e.g., TB).

  - Vector-borne transmission: Carried by animals like mosquitoes or ticks (e.g., malaria, Lyme disease).

  - Food and water: Eating or drinking contaminated food/water (e.g., cholera, salmonella).
• What is zoonosis?


  Zoonosis is a disease that can be transmitted to humans from other animals in natural circumstances.
• What are some examples of zoonosis?

  - Tuberculosis- via the bacterium mycobacterium bovis which is transmitted from cattle through the drinking of unpasteurised infected milk or the inhalation of droplets from coughing infected cows

  - Rabies- via the pathogen lyssaviruses which is transmitted from mainly dogs when an infected dog bites or scratches a human, or when a human's eye, moth or nose contacts the saliva of an infected dog

  - Japanese encephalitis- via the Japanese encephalitis virus, which is transmitted from pigs or birds, through mosquito bites.
• What are some factors that contribute to zoonosis?

  Zoonosis is a large global health concern. A major factor that contributes towards zoonosis is humans living in close contact to livestock. Another factor is the displacement of wild animals when their habitats are disrupted by the spread of human populations.