Zoonotic Diseases

What are zoonotic diseases?

Zoonotic diseases, or zoonoses, are infectious diseases that can spread between animals (vertebrates) and humans. Vertebrates are animals with a backbone, like cows, sheep, rats, dogs, cats, bats and birds. The way their bodies work is similar enough to ours that pathogens (germs) can sometimes adjust to live in both.

Some zoonotic diseases only spread from animals to humans and don’t spread from person to person. Others, like Ebola, spread from animals to humans and continue to spread in humans, causing periodic outbreaks of illness. Still others spread to humans and then mutate to only infect humans, like HIV and COVID-19. Once they only spread in humans, they’re no longer considered zoonotic (but other forms of the disease can still exist in animals).

What are the symptoms of zoonotic diseases?

Symptoms of zoonotic diseases vary depending on the specific illness. Some common symptoms include:

• Fever.
• Tiredness (fatigue).
• Headache.
• Body aches.
• Rash.
• Diarrhea.
• Vomiting.

What causes zoonotic diseases?

Many different pathogens can cause zoonoses. These include:

• Bacteria.
• Parasites (protozoa or parasitic worms).
• Viruses.
• Fungi.
• Prions.

Many pathogens only infect one specific type of organism — humans, specific animals, plants or even other germs. But zoonotic diseases have the ability to infect both humans and other vertebrates. Or at one time, they infected only specific animals, but mutations allowed them to “jump” to humans and cause an infection.

Most zoonotic illnesses are bacterial, parasitic or viral. Other zoonoses include ringworm (a fungal infection) and variant Creutzfeldt-Jakob disease (vCJD, commonly called “mad cow disease”), a form of prion disease.

Bacterial zoonoses

Bacteria are small, single-celled organisms that often release toxins that can make you sick. Examples of bacterial zoonoses include:

• Anthrax.
• Brucellosis.
• Cat scratch disease.
• Lyme disease.
• Mycoplasma pneumoniae.
• Plague.
• Psittacosis.
• Q fever.
• Salmonella.
• Tularemia.
• Tuberculosis.

Parasitic zoonoses

Parasites can be parasitic worms, protozoa (single-celled organisms) or ectoparasites, like lice and mites. Examples of parasitic zoonoses include:

• Cryptosporidiosis.
• Echinococcosis, like hydatid disease.
• Giardiasis
• Liver fluke.
• Malaria.
• Taeniasis (a type of tapeworm you can get from pork or beef).
• Toxoplasmosis.
• Trichinosis.

Viral zoonoses

Viruses are small pieces of genetic information in a container that use our cells to make more copies of themselves. Examples of viral zoonoses include:

• Avian influenza (bird flu).
• Ebola.
• Nipah virus.
• Marburg virus disease.
• Mpox.
• Rabies.

How do you get zoonotic diseases?

Zoonotic illness can spread through:

• Contact with the body fluids (like blood, pee, poop and saliva) of infected animals.
• Bites and sometimes scratches from infected animals.
• Bites from insects, like ticks, mosquitos or fleas.
• Eating undercooked meat.
• Drinking contaminated water (or eating foods washed with contaminated water).

What animals carry zoonotic diseases?

Almost any animal can carry zoonotic illnesses. Examples include:

• Bats.
• Birds.
• Cats.
• Deer.
• Dogs.
• Livestock, like cows, pigs and sheep.
• Non-human primates, like monkeys, apes and chimpanzees.
• Rodents, like rats, mice, moles and voles.

Who is at risk for zoonotic diseases?

You might be at higher risk for zoonotic infections if you:

• Work with animals as part of your job or hobbies (like in a veterinary office or on a farm).
• Hunt, prepare or eat wild animal meat.
• Have a weakened immune system.

How are zoonotic diseases diagnosed?

Healthcare providers usually diagnose zoonotic diseases with a sample of tissue or body fluid, including:

• Blood.
• Stool (poop).
• Sputum (mucus coughed up from your lungs).
• Mucus swabbed from your nose or throat.

Depending on your symptoms, you may also need imaging tests, like a chest X-ray or CT scan.

How are zoonotic illnesses treated?

Treatment for zoonotic illness depends on the infection. Not all zoonotic diseases have specific medications that get rid of the infection. Treatment might include:

• Antibiotics. Providers can treat most bacterial infections with antibiotics, especially if caught early.
• Antivirals. Providers can treat some zoonotic viruses with antiviral medications.
• Antifungals. Ringworm is easily treated with antifungal creams or lotions.
• Antiparasitic medications. Providers can treat most parasitic zoonoses with antiparasitic medications.
• Monoclonal antibodies. Providers can treat some hard-to-treat zoonotic diseases, like Ebola, with monoclonal antibodies.
• Surgery. Some parasites cause cysts that providers remove with surgery.
• Vaccination and immune globin. If an animal with suspected rabies bites or scratches you, your provider doesn’t wait for symptoms. They vaccinate you and treat your wound with human rabies immune globulin (HRIG) to prevent an infection.

Can you prevent zoonotic diseases?

Ways you can reduce your risk of infection with a zoonotic disease include:

• Stay up-to-date on vaccinations. If you’re at risk for certain zoonotic illnesses, like mpox, rabies or Ebola, you can get vaccinated to help protect you from infection. Many zoonotic illnesses don’t have vaccines.
• Protect yourself from bug bites. Wear long sleeves and long pants, use bug spray with DEET, check yourself and your pets for ticks after being outside, and ask your veterinarian how to prevent ticks and fleas on your pets.
• Wear gloves when handling animals (living or dead). Never pick up a wild animal with your bare hands. Wash your hands thoroughly after handling animals, even if you wear gloves.
• Follow safe food prep practices. Cook meat to safe temperatures. Always wash your hands, surfaces and utensils after preparing food. Don’t drink or prepare food with untreated water. Don’t drink unpasteurized milk or eat foods made with unpasteurized milk.
• Avoid contact with infected body fluids. For some serious illnesses (like Ebola), this means using protective equipment (such as a mask, goggles, apron and gloves) when caring for someone with an infection. Avoid touching any of their body fluids and wash your hands after contact, even if you wear gloves. Avoid contact with anything that may have touched infected body fluids.
• Don’t eat bush meat (the meat of wild animals).
• Try to avoid animal bites and scratches. See a healthcare provider if an animal that could have rabies (usually bats in the U.S.) bites or scratches you.

Are zoonotic diseases fatal?

Yes, some zoonotic diseases can be very serious and even fatal. Viral hemorrhagic fevers (like Ebola virus and Marburg virus) have a high mortality (death) rate. Rabies is always fatal once symptoms start. Most other zoonotic illnesses are treatable and are rarely fatal.

When should I see my healthcare provider?

Talk to your healthcare provider if you work with animals or are at higher risk for zoonoses. They can help you reduce your risk and know what symptoms to look out for.

When should I go to the ER?

Go to the emergency room if you have signs of serious illness, including:

• High fever (over 103 degrees Fahrenheit/40 degrees Celsius).
• Severe vomiting or diarrhea.
• Confusion or other mental changes.
• Unusual bleeding.
• Severe headache.
• Chest or abdominal pain.