Zoonotic diseases are infectious diseases in animals that can be transmitted to humans.
Many zoonotic diseases are spread through direct or indirect contact with affected animals. Some are transmitted via vectors like fleas, ticks, and mosquitoes. Others can be food or waterborne.
Children, pregnant women, elderly people, and those with compromised immune systems are most at risk for zoonotic diseases. Animal care workers also have an increased risk of exposure.
The best way to prevent the spread of these diseases is through proper hand washing, environmental cleaning, practicing safety around animals to avoid bites and scratches, preventing insect bites, properly washing fruits and vegetables, thoroughly cooking foods, and drinking only potable water. Pet owners should take steps to keep their pets healthy and follow their vet's advice for routine tests like parasite screenings. Talk to your doctor if you or a family member develops any unusual symptoms.
There are a number of zoonotic diseases that can affect both pets and people. Some are more serious than others, but most can create a serious health threat if not controlled.
- 01 of 10
Cat Scratch Disease
Commonly called Cat Scratch Fever, this disease is caused by bacteria called Bartonella henselae. Cats typically contract the bacteria from fleas. Bartonella henselae does not generally cause illness in cats.
Humans can contract cat scratch disease after getting a cat bite or scratch that breaks the skin. They can also get it if an infected cat licks an open wound on the human. Dogs can get the disease in the same ways.
Bartonella henselae often causes swelling at the injury site along with enlargement of nearby lymph nodes. Other common signs of infection include fever, lethargy, loss of appetite, and headache. In rare cases, cat scratch disease can become very serious, affecting the eyes and other major organs. Fortunately, most people and dogs are able to make a full recovery, although antibiotics may be needed in some cases.
- 02 of 10
Giardiasis is a disease caused by Giardia, a group of microscopic single-celled parasites that can infect a number of animals, including dogs, cats, rodents, and humans. They form tough cysts that allow them to survive in harsh environments until they can infect a new host.
Infection occurs when the Giardia parasite is ingested, often causing diarrhea and sometimes vomiting. Animals most commonly become infected by walking through contaminated soil and licking it off the paws or drinking contaminated water. Although it is possible for humans to get giardiasis directly from an infected animal, it is relatively uncommon. Humans most often get giardiasis from drinking contaminated water.
Animals being treated for giardiasis should be bathed regularly. The giardia cysts are shed in the stool and can remain on the animal's body. Pick up and properly dispose of feces immediately. People coming into contact with infected animals should thoroughly wash their hands after.
Fortunately, giardiasis can be treated with appropriate medications. Severely affected patients may need supportive and symptomatic care such as anti-diarrheal medications and fluids to maintain hydration.
- 03 of 10
The hookworm is a common intestinal parasite in dogs and cats that can cause diarrhea, loss of appetite, and anemia. Puppies can get hookworms from their mothers when nursing, but any dog or cat can become infected after ingesting hookworm larvae from the environment, eating infected prey, or when hookworm larvae penetrate their skin.
Hookworm larvae can also penetrate the skin of humans, which typically leads to a localized skin reaction that is swollen and itchy. In rare cases, the larvae can penetrate deeper tissues and cause more severe problems.
Prevent accidental exposure by wearing gloves while handling soil or coming into contact with contaminated environments, then by washing your hands well. Avoid walking barefoot in areas where animals may have defecated. Make sure you screen your pets at least annually for hookworms and other parasites.
Fortunately, hookworm infections can be treated with antiparasitic drugs. Most affected animals and humans will make a full recovery.
- 04 of 10
Leptospirosis is a bacterial disease caused by bacteria of the genus Leptospira. The bacteria are often carried in the urine of rodents and other infected animals. Animals and humans coming into contact with contaminated water, mud, and soil can contract the disease. They can also get it via direct contact with the urine of an infected animal or by eating an infected animal.
Dogs, livestock, and humans are all susceptible to leptospirosis. Illness is rare in cats, but they can still carry and transmit the bacteria. While some animals and humans will fight off the bacteria and never become sick, others get very ill. Leptospirosis in people often begins with flu-like symptoms. If it progresses, it can affect the major organs, especially the liver and kidneys.
Treatment involves antibiotics and supportive care. Help prevent exposure by getting your dog vaccinated against leptospirosis. Avoid coming into contact with the urine of affected animals and with potentially contaminated bodies of water.
- 05 of 10
Rabies is a deadly viral disease that affects mammals and is one of the most dangerous zoonotic diseases known.
Rabies is primarily transmitted via saliva, most commonly after a bite or scratch from an infected animal. Any mammal can contract rabies, including dogs, cats, and humans.
Rabies often starts with flu-like symptoms that progress to neurological dysfunction. It can lead to behavior changes, disorientation, seizures, and aggression.
Humans exposed to rabies can be treated with a series of post-exposure vaccinations and human rabies immune globulin. However, it is almost always fatal once symptoms develop.
If you are bitten by an animal, it is essential that you see your doctor right away. All dogs and cats should be regularly vaccinated against rabies to prevent the spread of this fatal disease.
- 06 of 10
Despite its name, ringworm is not a worm. It is named such due to the worm-like appearance of lesions on the skin of people. Also called dermatophytosis, ringworm is a fungal infection of the skin that can affect most animals, including dogs, cats, rabbits, rodents, and humans.
Ringworm is spread by contact with an affected animal or person or with a contaminated environment. In people, the fungus often causes red, scaly, circular lesions on the skin that itch. It leads to hair loss in areas where hair normally grows.
Ringworm is fairly easy to treat with antifungal medications. Fortunately, this is not generally a serious condition. However, it can be a nuisance to get rid of once it starts spreading to animals and humans in the household. Young, elderly, and immune-compromised individuals are at the greatest risk.
- 07 of 10
The roundworm is another common intestinal parasite in dogs and cats, especially puppies and kittens. Roundworms typically cause failure to gain weight, scruffy fur, and a potbellied appearance in young animals. Dogs and cats usually get roundworms from a contaminated environment although puppies can also be infected in utero.
Humans, especially children, can also be affected by roundworms if they accidentally ingest the eggs left in the environment by infected animals. After ingestion, the larvae migrate through the body, affecting the eyes and internal organs. Fortunately, this is relatively uncommon.
Avoid exposure by wearing gloves while handling soil or coming into contact with infected animals. Always wash your hands well afterward. Be sure you screen your pets at least annually for roundworms and other parasites.
Fortunately, roundworm infections can be treated with antiparasitic drugs. Most affected animals and humans will make a full recovery. However, when the roundworms affect a human's eye, heart, or brain, for example, the disease can be more serious.
- 08 of 10
Commonly called scabies, sarcoptic mange is a skin condition caused by the Sarcoptes scabiei mite. The mites burrow into the skin and cause intense itching, thickened skin, and hair loss.
Scabies can affect most animals, including people. However, different varieties of mites are adapted to live on different species of animals. Contact with the wrong variety of mite will often lead to milder symptoms than would be seen with a full-blown infestation.
Humans can get scabies through close contact with affected animals, but the itchy rash that develops may resolve without treatment. Humans with scabies can also pass the mites to other humans. Sarcoptic mange in animals can be treated and prevented with the routine use of many types of flea and tick medications.
- 09 of 10
Ticks can carry several diseases, including Rocky Mountain Spotted Fever, Lyme Disease, and Ehrlichiosis. Many tick-borne diseases affect both humans and animals. However, these diseases are not directly transmitted from animals to humans. Instead, ticks are necessary to carry the diseases between hosts.
The signs of many tick-borne diseases can take some time to appear and vary by disease, but most cause flu-like symptoms at first. Some diseases will cause a skin rash and/or joint pain.
Diagnosis and treatment of tick-borne diseases can be complicated. Recovery depends on the disease involved and the specifics of the patient's case.
- 10 of 10
Toxoplasmosis is a disease caused by the protozoan parasite Toxoplasma gondii. This parasite can be transmitted to most animals and humans, typically through ingestion of undercooked meat or cat feces.
Toxoplasmosis is often asymptomatic in cats. Most healthy humans with the parasite are also symptom-free. However, toxoplasmosis can cause serious health problems for people with compromised immune systems. It may also cause birth defects, miscarriage or stillbirth if a woman is infected for the first time while pregnant. This is why it is so important for pregnant women to use caution around cat litter boxes and avoid undercooked or raw foods.
In the rare cases that humans are made ill by toxoplasmosis, the symptoms can be vague. Mild fever, headache, and muscle aches are the most likely initial signs. In serious cases, the parasite can damage the brain or eyes. Treatment usually involves antibiotics and supportive care.