Diseases From Animals: A Primer
A is for animals, Z is for zoonoses.
Wild animals should stay that way. Enjoy them from a distance.
Even so, they're a rich source of human disease. Here are a few:
Raccoon roundworm. This is the best reason not to feed wild
raccoons. The feces of an infected raccoon carry millions of roundworm eggs.
These eggs become infectious in two to four weeks and can survive for years in
the environment. They are very difficult to kill -- the CDC recommends cleaning
contaminated decks or porches with boiling water or a propane flame gun (with
proper caution, of course).
Symptoms depend on where the roundworms travel in the body. They can include
nausea, fatigue, enlarged liver, and symptoms of brain infection (poor
coordination, inattention to one's surroundings, loss of muscle control, coma,
and/or blindness). Some infections have been fatal. Diagnosis is difficult. If
you are having symptoms after contact with raccoons, be sure to tell your
doctor. There is no specific cure, but early treatment can limit the extent of
Giardia infection. This microscopic parasite is the hiker's
bane. It's one of the main reasons why you should always purify water taken
from a stream, no matter how far from civilization you're camping. An infected
animal sheds Giardia in its feces. It can survive for a long time in
water and in soil.
Symptoms include loose or watery diarrhea, stomach cramps, and stomach upset.
People with Giardia infection are contagious and easily spread the
parasite to others. Fortunately, there are excellent curative treatments.
Hantavirus. This deadly virus is carried by some strains of mice,
especially deer mice. People get the infection by breathing dust contaminated
with mouse droppings. If you need to clean an area that's been infested with
mice, DON'T sweep it up in a big cloud of dust. Instead, put on latex gloves,
wet the area with detergent or diluted bleach, wipe with damp towels, and then
mop. Burn all contaminated materials. And be sure the mice are gone -- call an
Lymphocytic choriomeningitis (LCM). This is a virus spread by the
common house mouse. The virus can infect the linings of the brain and spinal
cord. It's a serious disease, although many people get only mild infections.
Mice shed the virus in their urine, saliva, and feces. People get infected by
eating contaminated food or by inhaling aerosolized mouse urine or feces. LCM
has two phases. The first lasts about a week and begins with fever, loss of
appetite, head and muscle aches, nausea, and/or vomiting. There may be other
symptoms as well.
The second phase happens just as the first one gets better. It may begin with
symptoms of meningitis: fever, headache, and stiff neck. It may also begin with
symptoms of encephalitis: sleepiness, confusion, and movement problems. There's
no cure, but most people recover completely with supportive treatment. However,
some people are left with permanent nerve or brain damage. About 1% of people
with LCM die.
Tularemia (rabbit fever). People usually get tularemia from direct
contact with rabbits. A person can also get it via the bite of an infected tick
or deerfly, by eating contaminated food, by drinking contaminated water, or by
breathing in F. tularensis, the bacteria that causes rabbit fever. It's
very infectious: Fewer than 10 microscopic germs can cause a lethal infection.
This is why tularemia was studied during World War II as a germ warfare
The kind of disease one gets depends on how one is infected. The inhaled form
is most severe, with a 30%-60% fatality rate in untreated cases. It causes
pneumonia with sudden fever, chills, muscle and joint aches, dry cough, and
progressive weakness. In severe cases there is bloody spit with difficulty
Equine Encephalitis and West Nile Viruses
The equine encephalitis and West Nile viruses are transmitted
from wild birds to humans -- and to horses -- by mosquitoes. We read a lot
about West Nile virus, because of its recent arrival in the U.S. and its rapid
spread across the nation. It can cause a very dangerous infection of the brain
and spinal cord. So can equine encephalitis, which has long been firmly rooted
in the U.S. In fact, eastern equine encephalitis is considered a much more
serious disease. About 30% of people who get it die, and another 30% have
lasting nerve damage.
Most years there are very few cases of equine encephalitis. But
some years are much worse than others -- and there's no way to predict in
advance when there will be an outbreak. It's too soon to know whether West Nile
virus will be the same every year or come in cycles in the U.S.