Zoonoses
Zoonoses (zoh-ah-NO-seez) are infections that humans contract from
animals.
KEYWORDS
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Cat scratch disease
Hantavirus
Lyme disease
Plague
Psittacosis
Rabies
Toxoplasmosis
Trichinosis
What Are Zoonoses?
Zoonoses are infections caused by parasites, bacteria, or viruses that are
passed from animals to humans. Most people contract zoonotic
(zoh-uh-NAH-tik) infections from animals with which they have a lot of
contact, such as pets or farm animals. Wild animals and insects can be the
source of disease, too, particularly for diseases spread by the bite of a
tick, mosquito, or fly. Animals such as wild rodents and bats also can
carry diseases that may be harmful to humans.
Zoonoses can cause minor or serious illness. In some cases, the organisms
involved infect people, but they do not become ill. Other zoonoses can be
very dangerous to people, especially anyone with an immune system weakened
by age or illness.
Are They Contagious?
Most of these infections do not spread from person to person or do so only
in rare instances. Usually they are spread from animals to humans in the
following ways:
-
from the bite of an infected insect
-
through contact with an animal's feces
*
or urine, either through the mouth or by breathing in dust from dried
feces
-
from the bite or scratch of an infected animal
-
from eating the meat of an infected animal
*
feces
(FEE-seez) is the excreted waste from the gastrointestinal tract.
*
lymph
(LIMF)
nodes
are small, bean-shaped masses of tissue that contain immune system
cells that fight harmful microorganisms. Lymph nodes may swell during
infections.
Some Examples of Zoonoses
Cat scratch disease
A cat carrying
Bartonella henselae
(bar-tuh-NEH-luh HEN-suh-lay), the bacterium responsible for cat scratch
disease, usually does not have symptoms, but if the bacteria are passed to
a human through a scratch or bite, a person may experience skin sores,
swollen and sore lymph nodes
*
, extreme tiredness, headaches, and fever. Antibiotics may be prescribed
to treat the infection.
Psittacosis
People who have contact with birds may be at risk for psittacosis
(sih-tuh-KO-sis), also known as parrot fever. If a person inhales bird
feces or urine particles while cleaning a bird's cage, he or she
may develop symptoms of pneumonia (nu-MO-nyah, inflammation of the lung),
such as fever, coughing, or chest pain. Antibiotics are used to treat
psittacosis.
Rabies
A virus that is carried in the saliva of infected animals can cause rabies
when transmitted through a bite or, less commonly, through contact with
saliva. Symptoms include fever, difficulty swallowing, delirium
*
,
seizures
*
, and coma
*
. Death can result if the infection is not treated. Treatment includes
intensive care in a hospital. A series of vaccinations
*
started at the time of a bite from a possibly infected animal can prevent
the person from developing the disease. Many mammals, especially raccoons,
bats, and dogs, may be infected with rabies, but human rabies is rare in
the United States. According to the U.S. Centers for Disease Control and
Prevention, there were no cases of rabies in humans in the United States
in 2000. In many other countries, especially those in the developing
world, rabies is much more common.
Plague
Plague (PLAYG) is a bacterial infection caused by
Yersinia pestis
(yer-SIN-e-uh PES-tis). Plague can be transmitted to humans through the
bite of a flea that has become infected through contact with an infected
rodent, such as a rat. The disease causes such symptoms as fever and
swollen lymph nodes. In some cases the infection spreads through the blood
and can infect the lungs. If this happens, plague can spread from person
to person through coughing or sneezing. Plague was the cause of huge
epidemics
*
in Europe and Asia during the Middle Ages, and it is still seen in many
developing countries. It is seen in many developed countries too,
including the United States, although not as many cases occur. The disease
can be fatal if it is not treated with antibiotics.
Hantavirus
Rodents, such as mice and rats, may carry hantavirus (HAN-tuh-vy-rus).
This virus can spread to humans when they inhale particles from rodent
feces, saliva, or urine. People infected with hantavirus can develop
hantavirus pulmonary (PUL-mo-nar-ee) syndrome (HPS), which causes such
symptoms as fever, headaches, muscle aches, nausea (NAW-zee-uh), vomiting,
diarrhea (dye-uh-REE-uh), abdominal
*
pain, and chills. In severe cases a person may experience shortness of
breath and the lungs may fill with fluid. There is no cure for hantavirus
infection, but people who have HPS typically are hospitalized in an
intensive care unit, where they receive oxygen and other types of
supportive care.
Lyme disease
Borrelia burgdorferi
(buh-REEL-e-uh burg-DOR-fe-ree) bacteria inside an infected tick can
cause Lyme (LIME) disease in humans after a tick attaches to the skin and
feeds on a person's blood. Ticks pick up the bacterium by feeding
on the blood of infected deer and mice, which serve as reservoirs for the
organism. Lyme disease can produce a number of symptoms, such as extreme
tiredness, muscle aches, and swollen, painful joints. At the site of the
tick bite, some people develop a bull's-eye rash, a red rash
surrounded by rings that resembles a bull's-eye target. A person
with Lyme disease usually is treated with antibiotics.
*
delirium
(dih-LEER-e-um) is a condition in which a person is confused, is unable
to think clearly, and has a reduced level of consciousness.
*
seizures
(SEE-zhurs) are sudden bursts of disorganized electrical activity that
interrupt the normal functioning of the brain, often leading to
uncontrolled movements in the body and sometimes a temporary change in
consciousness.
*
coma
(KO-ma) is an unconscious state in which a person cannot be awakened
and cannot move, see, speak, or hear.
*
vaccinations
(vak-sih-NAY-shunz), also called immunizations, are the giving of doses
of vaccines, which are preparations of killed or weakened germs, or a
part of a germ or product it produces, to prevent or lessen the severity
of a disease.
*
epidemics
(eh-pih-DEH-miks) are outbreaks of diseases, especially infectious
diseases, in which the number of cases suddenly becomes far greater than
usual, Usually epidemics are outbreaks of diseases in specific regions,
whereas worldwide epidemics are called pandemics.
*
abdominal
(ab-DAH-mih-nul) refers to the area of the body below the ribs and
above the hips that contains the stomach, intestines, and other organs.
Toxoplasmosis
Eating contaminated meat or having contact with the feces of an infected
cat can put a person at risk for toxoplasmosis
(tox-o-plaz-MO-sis). This zoonosis is caused by a parasite and can
produce such symptoms as swollen lymph nodes, muscle aches, headaches, and
sore throat in a healthy person and life-threatening brain infections in
people with weakened immune systems, especially those who have HIV/AIDS
*
. If a pregnant woman becomes infected with the parasite, she can transmit
the infection to her unborn baby, which can lead to a number of health
problems in the child.
Trichinosis
If people eat meat (especially pork products, such as sausage or ham)
infected with the eggs of
Trichinella
(trih-kih-NEH-luh) worms, they can contract trichinosis
(trih-kih-NO-sis), a disease that produces such symptoms as diarrhea,
vomiting, and abdominal pain. Trichinosis can cause nerve and muscle
damage as well as heart and lung problems. It can be treated with
medication.
How Are Zoonoses Treated?
The treatment of a zoonotic infection depends on the specific disease, but
many are treatable with prescription medications, such as antibiotics.
*
AIDS
, or acquired immunodeficiency (ih-myoo-no-dih-FIH-shen-see) syndrome,
is an infection that severely weakens the immune system; it is caused by
the human immunodeficiency virus (HIV).
How Are Zoonoses Prevented?
Because household pets may carry zoonotic organisms, it is important to
keep pets healthy and vaccinated to avoid infection. Some other ways
people can protect against zoonoses include:
-
having pets regularly examined by a veterinarian
-
avoiding contact with stray, unfamiliar, or wild animals
-
cleaning litter boxes daily and animal cages frequently to prevent the
growth of bacteria and parasites
-
having someone who does not have a weakened immune system and is not
pregnant empty pet litter boxes, bathe pets, clean pet cages, and pick
up pet feces
-
cooking meat until it is no longer pink inside and the juices run clear
-
washing hands with soap and warm water after handling animals and before
eating
-
clearing brush and other areas around the house where rodents might live
-
not storing food or trash in an area where it could attract animals
-
wearing long sleeves and long pants when outdoors, especially in wooded
areas, to discourage tick and mosquito bites
-
using insect and mosquito repellent
-
examining the body and pets for ticks after spending time outside in
areas where ticks are found
