There are specific infections that can be transmitted between animals and humans which may cause disease; these are known as ‘zoonotic diseases’ or zoonoses. Any animal can potentially be involved in transmitting or can potentially be infected by a human with a zoonotic infection, including companion animals, farm animals, and wildlife, as well as species susceptibility to specific diseases varies. Further information on specific zoonotic diseases can be found in the linked articles at the end of this page.
Examples of infections which can be transmitted from animals to humans include Hendra virus and psittacosis.
Examples of infections which can be transmitted from humans to animals (sometimes called ‘reverse zoonoses’) include: tuberculosis, and antibiotic resistant bacterial infections (e.g., methicillin resistant Staphylococcus aureus or MRSA).
SARS-CoV-2 or COVID-19 can be transmitted from humans to animals, however it is thought that animals do not play a significant role in infection of humans. More information on COVID-19 and animals can be found in the linked articles at the end of this page.
Many zoonotic infections can be transmitted both ways (from humans to animals and from animals to humans) including dermatophytosis (commonly known as ringworm).
Zoonotic diseases can be caused by viruses, bacteria, parasites, fungi and prions (also called infectious agents).
People should make sure that they are aware of the different types of zoonotic diseases potentially present in animals that they live with, handle or work with, how these diseases can be transmitted, and how to reduce the risk of disease transmission. People should also make sure that they are aware of reverse zoonotic infections that they may transmit to the animals with which they are in contact.
How are zoonotic diseases transmitted?
Infections that can affect both humans and animals can be transmitted in a number of ways including through:
- Direct contact between a human and an animal.
- Sharing a common area where infection can be transmitted via aerosols (small droplets that can suspend in the air).
- Indirect contact through interaction with an area or object that the infected individual has been in contact with and which has been contaminated by the infectious agent. This can include animal enclosures, bedding, equipment, clothes, and soil.
- Foodborne infections are transmitted through the consumption of animal products from an infected animal or consumption of food/water that has been contaminated by an infectious agent. Eating undercooked meat or unpasteurised milk, handling raw meat and eating without washing your hands thoroughly are all examples of how a foodborne infection can be transmitted.
- Vector-borne infections are transmitted through a second animal (known as the vector), most commonly an insect, that carries the disease usually from the animal to the human.
What increases the risk that a human will be infected by a zoonotic disease?
It is possible for any person to be affected by a zoonotic disease. However, there are certain people who are at greater risk of contracting infectious disease (including zoonotic disease) because their immune system is not functioning normally and is unable to effectively resist or fight infections. People who may not have a normally functioning immune system include young children (under five years of age), older people (over 65 years of age), people on medication that supresses their immune system (for example, chemotherapy drugs or steroids), pregnant women, and people with diseases that can suppress their immune system (for example, cancer or HIV infection).
People at greater risk of contracting infectious disease, or who may have a higher risk of suffering serious illness from zoonotic diseases, should be careful around animals and take the precautions explained below. They should also talk to their doctor about any particular precautions they should take related to their specific condition.
Minimising the risk of disease transmission from animals to humans, and from humans to animals
The risk of contracting a zoonotic disease is low if you are healthy, use common sense and good hygiene, and keep your animals healthy.
The following steps will minimise the risk of a zoonotic disease being transmitted from an animal to a person:
- Hygiene: hands should be washed after being near animals, whether you touched them or not.
- Keep animals healthy: regular veterinary checks and good preventative health care (for example, regular effective parasite control) will help reduce the risk that an animal will carry a zoonotic infection.
- Avoid being licked by animals, especially on/near the face.
- Do not share food with animals.
- Teach children that they should not put their mouths on an animal and should not put any part of an animal’s body in their mouth.
- Prevent children from playing in soil which may be contaminated with animal faeces.
- Avoid animal bites and scratches. If you do get bitten or scratched by an animal, promptly contact and/or visit your doctor for assistance.
- Prevent bites from insects that may transmit infections such as mosquitoes, ticks, and fleas.
- Be aware of zoonotic diseases that may be present in the species of animals with which you come into contact. Animals do not always show symptoms of disease so the simple precautions above should be always be taken.
People should also be aware of human infections that can be transmitted to animals. If you know that you have an infection that could be transmitted to an animal, take precautions to reduce the risk of infecting animals with which you come into contact (for example, your pets, wildlife, or farm animals). Specific details should be discussed with your doctor and a veterinarian.
How can human behaviour and climate change alter the risk of zoonoses?
With humans now living in more semi-urban areas and adjacent to native animal habitat in Australia and overseas, there is an increased risk of exposure of humans to disease from animals through increased contact (direct and indirect) between humans and wild animals.
Climate change can impact the survival of certain infectious agents and insect vectors to allow for easier spread of disease from animals to humans. Increasing temperatures and higher incidence of extreme weather events (e.g., floods) can increase insect numbers to result in greater transmission of disease from animals to humans (e.g., Japanese Encephalitis Virus).
For more information on the longer-term effects of human behaviour and climate change on both humans and our animals, see the links below.