Every year, tens of thousands of Canadians will get sick from a disease they caught from a bug or other animal. These are known as zoonotic diseases.
What is Zoonotic Disease?
Zoonotic disease, also called zoonosis, are a group of diseases that can be transmitted to humans by nonhuman vertebrate animals, such as mammals, birds, reptiles, amphibians, and fish. A large number of domestic and wild animals are sources of zoonotic disease, and there are numerous means of transmission.
Zoonotic diseases can be caused by viruses, bacteria, parasites, and fungi. These diseases are very common. Research indicates that between one third and one half of all human infectious diseases have a zoonotic origin, that is, they are transmitted from animals. About 75% of the new diseases that have affected humans over the past 10 years (such as the West Nile Virus) have originated from animals or products of animal origin.
These diseases can enter a person’s body through a number of ways including broken skin, eyes, mouth and lungs. Even animal bites can result in transfer of zoonotic diseases such as rabies.
Zoonotic diseases also can be classified according to their life cycle. Diseases that are transmitted directly (e.g., through direct contact or a mechanical vector) and that are maintained in nature in a single vertebrate host species are known as orthozoonoses; an example is rabies, which is maintained by canids. Cyclozoonoses, such as echinococcosis, require more than one vertebrate host for development. Metazoonoses require both a vertebrate host and an invertebrate host; an example istrypanosomiasis. Zoonotic diseases that require a vertebrate host and another type of environmental reservoir (e.g., food or soil) are known as saprozoonoses. Listeriosis and histoplasmosis are examples of saprozoonoses.
Zoonoses have been recognized for many centuries, and over 200 have been described.
Some of the most common Zoonotic diseases to know about include:
- Lyme disease and Rocky Mountain spotted fever, which you can get from a tick bite.
- West Nile virus, which you can get from a mosquito bite.
- Dengue, malaria, and chikungunya, which you can get if you travel to areas where these diseases are common, such as the Caribbean, and are bitten by an infected mosquito.
- Salmonella infection, which you can get after handling a baby chick, chicken, duck, turtle, or snake
- coli infection, which you can catch if you touch areas in a petting zoo or animal exhibit where some of the animals are infected. You can also catch E. coli infection if you work at a dairy because cows can have E. coli germs on their udders.
How Does Zoonotic Disease Spread?
Many people interact with animals in their daily lives, either for business or pleasure. Some raise animals for food, others keep them in our homes as pets .You might come into close contact with animals at a fair or petting zoo or encounter wildlife when we clear wooded land for new construction.
Because of these interactions, it’s important to be aware of the different ways people can get zoonotic diseases. These can include:
- Coming into contact with the saliva, blood, urine, or feces of an infected animal
- Being bitten by a tick or mosquito (often called a “vector”)
- Eating or drinking something unsafe (such as unpasteurized milk, undercooked meat, or unwashed fruits and vegetables that are contaminated with feces from an infected animal)
Who is most at risk?
The risk of becoming infected with a zoonotic disease is increased in persons affected by immunosuppression from a preexisting disease or medication. For example, cryptosporidiosis caused by Cryptosporidium parvum, which is transmitted to humans following contact with calves, their manure, or manure-contaminated objects or food, can occur as a coinfection with acquired immunodeficiency syndrome
- Children under the age of 5 years
- Pregnant women
- Adults over the age of 65 years
- Anyone with a weakened immune system – for example, someone with HIV or a cancer patient undergoing chemotherapy
Places where you might come into contact with an infected bug or animal
- Nature parks of any type—fields, woods, beaches, deserts
- Wooded and bushy area
- Animal displays, petting zoos, and pet stores
- Fairs and festivals
Always wash your hands after being around animals
- It’s not always convenient to wash your hands or your children’s hands, but it’s important.
- After you are around an animal, wash your hands for 20 seconds.
Protect yourself from bug bites, day and night
- Use bug repellent on skin not covered by clothes or shoes.
- Look for repellents that contain 20% or more DEET.
- Remember that repellents only last for a few hours, so reapply! Follow the instructions on the label.
- Spray your clothing and gear—including boots, pants, socks, bed nets, and tents—with products containing permethrin, which repels and kills ticks, mosquitoes, and other arthropods.
- Get rid of any standing water. Check buckets, flower pots, old tires, and even litter. Mosquitoes breed in standing water, so get rid of the water in these areas outside your home
- Check for ticks after you’ve been outdoors
- Check your body and your children’s bodies for ticks, and once you find a tick, remove it right away.
- Use fine-tipped tweezers to grasp the tick as close to the skin’s surface as possible.
- Pull upward with steady, even pressure. Don’t twist or jerk the tick. This can cause the mouthparts to break off and remain in the skin. If this happens, remove the mouthparts with tweezers. If you are unable to remove the mouth easily with clean tweezers, leave it alone and let the skin heal.
- After removing the tick, thoroughly clean the bite area and your hands with rubbing alcohol, an iodine scrub, or soap and water.
- Never crush a tick with your fingers.
- Dispose of a live tick by flushing it down the toilet, submerging it in alcohol, placing it in a sealed bag/ container, or wrapping it tightly in tape.
- Don’t “paint” the tick with nail polish or petroleum jelly.
- Don’t use heat to make the tick detach from the skin. These methods will NOT work
- Check your dogs and cats for tickets
- To avoid ticks while you’re hiking, walk in the center of trails. Avoid wooded and bushy areas with high grass and leaf litter.
Controlling Zoonotic Diseases
Zoonotic diseases are difficult to control, particularly because of their animal reservoirs. Indeed, unlike diseases such as smallpox and polio, most zoonotic diseases cannot be eradicated through intensive human vaccination campaigns. Their successful control relies instead on strategies aimed at reducing the burden of disease among wild animals. In the case of rabies, for example, the distribution of baits containing oral rabies vaccine has led to the near-elimination or eradication of variant rabies (e.g., the Arctic fox and red fox variants) from regional wildlife reservoirs (e.g., foxes and raccoons).
Zoonotic disease risk is increased when humans live in close proximity to domestic animals such as poultry and livestock.
Limiting contact between humans and wild animals is critical to reducing the risk of zoonotic disease transmission.
Because zoonotic disease agents can be found in humans, animals, the environment, and vectors, management requires the collaboration of many types of health and disease-control specialists. Disease control may include vector-control programs for ticks, fleas, or mosquitoes, and environmental cleanup or protection may be required to address disease agents that remain viable from days to years on surfaces, in soils, or in the water. In most state health agencies, public health veterinarians are available to assist in disease-control coordination.