10 Horrible Diseases Your Pet May Expose You To

Anna M. van Heeckeren, DVM
Updated: February 15, 2021
Published: January 25, 2016
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Top 10 Nasty Zoonoses

By Anna M. van Heeckeren, DVM

What is a zoonoses? It's the plural of zoonosis, which is a disease that can be passed from an animal to a person (and sometimes the other way around). Zoonoses can be caused by any number of different germs, like viruses, bacteria, parasites, fungi, and even strange proteins called prions.


There are too many zoonoses out there for all of them to make this top ten list. For instance, there are fifty-four listed as zoonotic diseases of importance in the U.S., according to one recent article in the Journal of the American Veterinary Medical Association. In that list, there are twenty-three that can be passed from dogs to people; twelve of which have caused human deaths, and another five that rarely cause human death. There are twenty listed that can be passed from cats to people (some are the same as those from dogs); ten of those can cause human deaths, and another five that rarely cause human death.


This list of nasty zoonoses can be passed to people from dogs or cats and range from the mildly annoying to the incapacitating to the deadly…

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1. Tapeworm

This parasite can be transmitted from accidentally ingesting a flea from your dog or cat. Symptoms, if infected with a flea tapeworm, include stomach aches, diarrhea, and an itchy butt.

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2. Ringworm

This is often confused with another zoonosis called roundworm (see below). Ringworm is a fungus that is fairly common in dogs and cats. It is often found in shelters, and can be passed to people who pet an infected animal. It usually leaves people with a skin rash that's uncomfortable.

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3. Roundworm

This is a parasite found in almost every puppy and kitten. They usually get it from their mothers before they're born or from drinking mother's milk. They spread this disease through their poop. People can accidentally ingest them if they handle dirt (or poop) containing these nasty roundworm eggs and forget to wash their hands before eating. Fortunately, most people don’t get horrible symptoms, but for those that do, they include stomach problems, vision problems, and seizures; rarely does it lead to death.

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4. Hookworm

This is another parasite that, like roundworm, can be spread through animal poop. But it can also infect people through direct skin contact, like when walking in bare feet outside on contaminated dirt. Symptoms range from no symptoms to as severe as blood loss leading to stunted growth and mental retardation in children, and rarely death.

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5. Cat Scratch Disease

This is caused by bacteria found in the claws of some cats, though some people report a cat bite can also cause this. Usually there’s a mild infection where the injury occurs, but can lead to swollen lymph nodes, fever, headache, and a poor appetite. Rarely does it lead to other complications.

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6. Leptospira

This is a bacteria that can be found in the urine (pee) of dogs. People can develop many symptoms similar to that of a cold (fever, chills, headache, muscle aches, vomiting, diarrhea), after which they feel better and then get sick again with severe kidney or liver disease, or infection of the brain (Weil’s disease). It can also lead to death.

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7. Toxoplasma

This is caused by a bacteria that most people have heard about (Toxoplasma gondii) that can be found in contaminated kitty litter. It can also be found elsewhere, such as in undercooked meats or unwashed vegetables, so you can’t always blame the cat for this one. Symptoms can include swollen glands and muscle aches as if you have the "flu." Pregnant women should be especially careful because this disease can infect the developing baby and cause deformity or miscarriage.

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8. Plague

While you may think this is no longer a real fear, it’s still around in some parts of the world. This is caused by a bacterium (Yersinia pestis) that infects fleas. If an infected flea bites you, you can get infected too. This can lead to death if not treated.

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9. Rabies

This virus should be well known by the public. It is caused by a bite from an infected animal, like a dog or cat. Thankfully, this is not common in dogs or cats, because of successful rabies vaccination programs.

10. Lyme Disease

Lyme disease, so called because it was originally discovered in Old Lyme, CT, is one of the most common tick-transmitted diseases in the world.


While it is technically not a zoonosis, Lyme disease is one of the most common tick-transmitted diseases and can be passed onto you or your dog. It is caused by the bite of a tick infected by the bacterium Borrelia burgdorferi. Clinical signs of Lyme disease include red, expanding rash, fatigue, chills, fever, joint aches, and swollen lymph nodes. If left untreated, it can lead to facial palsy, heart palpitations, and even meningitis.

How Do I Prevent Myself from Contracting These Diseases

So, while scary, the good news is that you can easily prevent getting diseases from dogs and cats (and other animals) by remembering these three easy steps:


1. Vet up

Take your pet to a veterinarian at least once a year to get the vaccines and medications needed. For example, preventatives can help protect against flea and tick infestations.


2. Pick up

Pick up animal poop daily and throw it in the trash, and keep your home neat and clean (and your yard, if you have one).


3. Wash up

Wash your hands frequently, especially before mealtime.


If you’re scared enough that you want to know if you or your pet is infected, go to your doctor or veterinarian. It’s as simple as that.


Dr. Anna M. van Heeckeren is the founder of the One Health Organization, whose mission is to develop, sustain, and nurture healthy bonds between vulnerable populations and animals living together initially by increasing the number of dogs and cats owned by older adults and the disabled that receive essential veterinary and other pet care services.