Monkeys, bats and a menagerie of other critters can spread Ebola. Mosquitoes are behind outbreaks of West Nile, deer mice were to blame for Yosemite campers’ hantavirus a while back and pigs have infected many people with swine flu.
It’s as if the animals are plotting a revolution to overthrow us.
But it’s nothing new. Plague, yellow fever and cholera have been around for ages, as well as a host of other zoonoses, or diseases that can be transmitted from animals to humans.
There are a minimum of 39 important diseases that people catch directly from animals, 42 important diseases that people get by eating or touching food or water contaminated with animal feces, and at least 48 important diseases that humans can get from the bite of bugs that feasted on an infected animal. It’s a rough world out there in nature.
And it’s not just tropical insects and woodland wildlife that can make us sick. In fact, our own beloved pets may play host to a long list of diseases and parasites that are easily transmittable to humans, even dogs have been implicated in potentially spreading the dreaded Ebola. At least one major study found that dogs can be infected with Ebola without having symptoms (although how likely they are to spread it to people remains unclear).
Although the numerous health benefits of pets far outweigh the risks, it can’t hurt to know what to watch out for:
1. Lyme disease
Those who cruise the woods and dunes know to perform a tick check upon their return. But if your pets are doing the cruising, they can bring infected ticks to you even if you haven’t left home. You can’t get Lyme disease directly from your pet, but they can pick up an infected tick and pass it on to you.
2. Psittacosis (Parrot Fever)
Not just for pirates! Psittacosis is an infection caused by Chlamydia psittaci, a type of bacteria found in the droppings of birds — including parakeets, macaws and cockatiels — which is spread to humans. Birds often don’t show symptoms. In humans, symptoms include blood-tinged sputum, dry cough, fatigue, fever and chills, headache, joint aches, muscle aches and shortness of breath.
3. Cat scratch fever
Commonly known as cat scratch disease, the bacterial disease made famous by Ted Nugent is caused by Bartonella henselae. Cat scratch disease usually follows a bite or scratch from a cat, with a mild infection where the wound is. Symptoms include swollen lymph nodes, fever, headache, fatigue and diminished appetite. Rare complications of B. henselae infection are possible.
Really? Although plague no longer causes massive epidemics that wipe out large sections of the population with symptoms fit for horror movies, it still exists. It’s rare in the United States, but does occur in parts of California, Arizona, Colorado and New Mexico. On average, 10 human plague cases are reported each year in the United States. Plague is generally associated with rats, but as the U.S.. National Library of Medicine points out, "risk factors for plague include a recent flea bite and exposure to rodents, especially rabbits, squirrels or prairie dogs, or scratches or bites from infected domestic cats." The presentation of plague in cats is most commonly bubonic plague. Cats with bubonic plague typically present with fever, anorexia, lethargy and an enlarged lymph node that may be abscessed and draining, according to the Merck Veterinary Manual.
5. Q fever
The bacteria Coxiella burnetii is the culprit behind the curiously named Q fever. Cattle, sheep and goats are the primary targets, although a variety of species may be infected, including house pets. The organism is found in the milk, urine and feces of infected animals, and since it is extremely hardy and resistant to heat and many common disinfectants, it is able to survive for long periods in the environment. Infection of humans usually occurs by inhalation of these organisms, as well as through tick bites or consuming unpasteurized dairy products.
As for the name: The Q stands for "query" due to the unknown etiology of the mystery disease when it was first recognized.
Rabies is a viral disease of mammals generally transmitted through the bite of an infected (crazy-eyed, foaming-at-the-mouth) animal. Most rabies cases reported to the Centers for Disease Control and Prevention each year occur in woodland scamperers like raccoons, skunks, bats, and foxes, but domestic species accounted for 8 percent of all rabid animals reported in the United States in 2010.
The rabies virus attacks the central nervous system, ultimately causing disease in the brain followed by death. The early symptoms of rabies in people are similar to that of many other illnesses, including fever, headache, and general weakness or discomfort. As the disease progresses, more specific symptoms appear and may include insomnia, anxiety, confusion, slight or partial paralysis, excitation, hallucinations, agitation, hyper-salivation, difficulty swallowing and hydrophobia. The simple workaround? Keep your pet's rabies vaccination up to date.
Caused by the Campylobacter bacterium, most cases of campylobacteriosis are associated with eating raw or undercooked poultry or meat, or from cross-contamination of other foods by these items. It is one of the most common causes of diarrheal illness in the United States. Pets can also become infected, and people can get sick from contact with the stool of an ill dog or cat. Most people recover quickly, but more severe infection can occur.
Leptospirosis is a bacterial disease that your pet can get when it comes into contact with the bacteria in the environment (drinking, swimming or walking through contaminated water) or when exposed to infected animals. In humans, it may produce no symptoms, or it may come with many, including high fever, headache, chills, aches, vomiting, jaundice, abdominal pain, diarrhea and rash.
Without treatment, Leptospirosis can lead to kidney damage, meningitis liver failure, respiratory distress and death.
We commonly hear about the bacteria known as Salmonella from outbreaks of contaminated food and eating raw eggs. Most people infected with Salmonella develop diarrhea, fever and abdominal cramps within 12 to 72 hours after infection. But people can get it from pets as well, usually through contact with the pet’s feces. Reptiles such as lizards, snakes, and turtles are likely sources of this infection, as well as chicks and ducklings. Dogs, cats, birds and horses may also carry it.
Toxoplasma gondii is a protozoa that most often infects cats, but will also take up in other warm-blooded animals. Humans can get the nasty parasite from contact with cat feces, or by eating undercooked meat or unwashed vegetables. Once ingested, T. gondii can invade the brain and muscle tissues, and reside within cysts that are resistant to attacks by the host's defense system. The infection may also be passed from an infected mother to her baby through the placenta, creating serious complications — which is why moms-to-be should be relieved from cat-box duty.
This fungal infection forms a ring-shaped rash on the skin or a bald patch on the scalp. It is transmitted easily from pets to people, and from people to people, who can get it from direct contact with an infected animal.
Left untreated, nearly all puppies and kittens get roundworm. Distributed by pet feces, the egg form (the oocyst) can survive in the soil for years. If a human accidentally eats an oocyst, small worms hatch in the gut and move through the body. Nice. The larvae can also enter directly through the skin. Symptoms include fever, coughing, asthma, and/or pneumonia. Unfortunately, the worms can also enter the eye and cause Ocular toxocariasis, which though rare, causes blindness in seven out of 10 of those affected by it.
Most human tapeworm infections are the result of eating raw or undercooked meat of infected animals, especially pork and beef. (Sayonara, steak tartare.) But children can pick up tapeworm parasites from cats and dogs by inadvertently swallowing a flea infected with tapeworm larvae — which may sound unlikely, but it happens. In the human intestine, the larva develops into the adult tapeworm. A tapeworm can grow to longer than 12 feet and can live for years — almost like a new pet!
These intestinal parasites are commonly found in dogs and cats, especially young ones. The worms’ eggs or larvae are passed from pets through stool and infest soil. People get infected by direct contact when they walk barefoot over contaminated soil. A young child might also accidentally eat the worm eggs. Hookworm infection can cause painful and itchy skin infections or abdominal symptoms.
This bacteria lives inside the mouths of dogs and cats but doesn't make them sick. However, Capnocytophaga can spread to humans through licks, bites, scratches and close contact. The bacteria will rarely make humans sick except for people with weakened immune systems. Symptoms of an infection include blisters, swelling, fever, diarrhea, vomiting, headache and muscle/joint pain.
To protect yourself from diseases carried by house pets, follow these tips from WebMD:
- Wash your hands with soap and running water after touching feces.
- Take your pet to the vet on a regular basis and keep up with all vaccinations recommended for your area.
- Avoid rough play with cats.
- If your cat or dog bites you, wash the area with soap and water right away.
- Wash your hands after handling your pet — especially before eating or preparing food.
- People with weakened immune systems should take special precautions. These include never letting pets lick them on the face or on an open cut or wound, never touching animal feces, and never handling an animal that has diarrhea.
- Don't let your pet drink from toilet bowls or eat feces.
Editor's note: This article has been updated since it was originally published in September 2012.