Diseases From Animals: A Primer
A is for animals, Z is for zoonoses.
Diseases From Cats and Dogs
By far they're our best friends. And that means cats and dogs
are common sources of disease.
Cats often carry a germ called Bartonella henselae. Some
40% of cats are infected at least once in their lives -- usually when they're
kittens -- but they don't look sick. Humans get infected only when they are
bitten or scratched by an infected animal -- cat-scratch fever
Other bacterial infections humans can get from cats and dogs
- Plague. Rodents carry the plague bacteria. Very rarely, cats get fleas from
infected rodents and pass the disease to humans.
- Q fever. People are much more likely to get Q fever from barnyard animals
than from cats. But it does happen. Half of infected people get symptoms that
include fever, headache, chest or stomach pain, diarrhea, and/or vomiting. It
can also cause temporary swelling of the heart -- a dangerous event for people
who already have heart disease.
- Campylobacter infection. Found in animal feces, this germ causes
gastrointestinal symptoms. It's usually not dangerous, but can cause severe
illness in people with weakened immune systems.
- Leptospira infection. Humans get infected via contact with water,
food, or soil containing urine from infected animals. Left untreated,
leptospirosis can be quite serious. It can lead to liver failure, trouble
breathing, kidney damage, brain and spinal cord infection, and, rarely, death.
Symptoms vary widely but can include high fever, severe headache, chills,
muscle aches, and vomiting. There may also be yellow skin and eyes, red eyes,
abdominal pain, diarrhea, or a rash.
- Salmonella infection. People get this often-severe gastrointestinal
infection via contact with animal feces. It can cause severe kidney damage to
Both cats and dogs sometimes get parasites that infect humans.
One of the most common is roundworm. Left untreated, nearly all puppies and
kittens pick up this parasite. Its egg-like form -- the oocyst -- can survive
for years in soil.
When humans ingest oocysts, tiny worms hatch in the gut and
move through the body. Symptoms include fever, coughing, asthma, and/or
pneumonia. Once in a while, the tiny worms enter the eye and scar the retina.
This results in permanent partial vision loss. "Some 750 to 1,500 kids go
blind each year with roundworm infection [of the eyes] passed from dogs through
feces to children, " Glickman says.
Other parasites of cats and dogs:
- Toxoplasmosis. See above.
- Tapeworm. A person gets infected by swallowing an infected flea -- a
relatively rare event, but it happens.
- Hookworm. Hookworms are common in tropical and subtropical areas. They
infest soil contaminated by animal feces. Humans get infected by direct
contact, usually by walking on contaminated soil. Heavy infections can be
- Cryptosporidiosis. This parasite cause mild to severe intestinal symptoms
like diarrhea. It's not usually a dangerous infection, except to people with
weakened immune systems.