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Toxoplasmosis
Toxoplasmosis Definition ?
Toxoplasmosis is an infectious disease caused by the one-celled
protozoan parasite Toxoplasma gondii. Although most individuals do not
experience any symptoms, the disease can be very serious, and even
fatal, in individuals with weakened immune systems.
Description
Toxoplasmosis is caused by a one-celled protozoan parasite known as
Toxoplasma gondii. Cats, the primary carriers of the organism, become
infected by eating rodents and birds infected with the organism. Once
ingested, the organism reproduces in the intestines of cats, producing
millions of eggs known as oocysts, which are excreted in cat feces daily
for approximately two weeks. In the United States, it is estimated that
approximately 30% of cats have been infected by T. gondii. Oocysts are
not capable of producing infection until approximately 24 hours after
being excreted, but they remain infective in water or moist soil for
approximately one year. When cattle, sheep, or other livestock forage
through areas with contaminated cat feces, these animals become carriers
of the disease. Fruits and vegetables can also become contaminated when
irrigated with untreated water that has been contaminated with cat
feces. In humans and other animals, the organisms produce thick-walled,
dormant structures called cysts in the muscle and other tissues of the
body.
Most humans contract toxoplasmosis by eating cyst-contaminated raw or
undercooked meat, vegetables, or milk products. Humans can also become
infected when they come into contact with the T. gondii eggs while
cleaning a cat's litter box, gardening, or playing in a sand-box, for
instance. Once infected, an individual is immune to re-infection. The
incubation period or period between infection and the start of the
disease ranges from several days to months.
Anyone can be infected by T. gondii, but usually only those individuals
with weakened immune systems (immunocompromised) develop symptoms of the
disease. For them, toxoplasmosis can be severe, debilitating, and fatal.
Immunocompromised individuals at risk include those with AIDS, cancer,
or other chronic illnesses.
There is no person-to-person transmission, except from an infected
mother to her child in the womb. Approximately six out of 1,000 women
contract toxoplasmosis during pregnancy. Nearly half of these maternal
infections are passed on to the fetus. Known as congenital
toxoplasmosis, this form of the disease is acquired at birth by
approximately 3,300 infants in the United States every year. The risk of
fetal infection is estimated to be between one in 1,000 to one in
10,000. In children born with toxoplasmosis, symptoms may be severe and
quickly fatal, or may not appear until several months or even years
after birth.
What factors increase the risk of this infections ?
The following situations potentially expose a person to the toxoplasma
parasite and increase the risk of acquiring toxoplasmosis:
1. touching your hands to your mouth after gardening, cleaning a cat's
litter box, or anything that came into contact with cat feces
2. eating raw or partly cooked meat, especially pork, lamb, or venison
3. touching your hands to your mouth after contact with raw or undercooked
meat
4. organ transplantation or transfusion (this is rare)
If a woman is pregnant when she is infected with toxoplasmosis, the
infection can be transmitted from her to the baby with sometimes
catastrophic consequences.
What are the "Symptoms of Toxoplasmosis"
Most often, you won't know that you've contracted toxoplasmosis,
although some people may develop toxoplasmosis symptoms similar to those
of the flu or mononucleosis, such as:
1.
Body aches
2.
Swollen lymph nodes
3.
Headache
4.
Fever
5.
Fatigue
6.
Occasionally, a sore throat
If you are living with HIV/AIDS, are receiving chemotherapy or have
recently had an organ transplant, you're more likely to develop signs
and symptoms of severe toxoplasmosis infection, including:
1. Headache
2. Confusion
3. Poor coordination
4. Seizures
5. Lung problems that may resemble tuberculosis or Pneumocystis carinii
pneumonia, a common opportunistic infection that occurs in people with
AIDS
6. Blurred vision caused by severe inflammation of your retina (ocular
toxoplasmosis)
Signs in babies
Most pregnant women with toxoplasmosis don't have signs or symptoms of
the disease, but if you become infected for the first time just before
or during your pregnancy, you have about a 30 percent chance of passing
the infection to your baby (congenital toxoplasmosis), even if you
aren't having signs and symptoms yourself.
The risk and severity of your baby's infection often depend on when in
your pregnancy you were infected. Your baby is most at risk of
contracting toxoplasmosis if you become infected in the third trimester
and least at risk if you become infected during the first trimester. On
the other hand, the earlier in your pregnancy infection occurs, the more
serious the outcome for your baby. Many early infections end in
stillbirth or miscarriage, and children who do survive are likely to be
born with serious problems, such as:
1. Seizures
2. An enlarged liver and spleen
3. Yellowing of the skin and whites of the eyes (jaundice)
4. Severe eye infections
Only a small number of babies who have toxoplasmosis show signs of the
disease at birth. Instead, many infected newborns don't develop signs
and symptoms of the disease until they're in their teens or later. Those
signs and symptoms include:
1. Hearing loss
2. Mental retardation
3. Serious eye infections that may lead to blindness.
Why do some people develop severe problems from toxoplasmosis ?
Few people with toxo develop symptoms because the immune system usually
keeps the parasite from causing illness. However, anyone with a
compromised immune system is at risk for serious problems from toxo. These
individuals include those undergoing chemotherapy, people with HIV/AIDS or
other immune disorders, and recent organ-transplant recipients.
In these people, an infection that occurred anytime during life can
reactivate and cause the severe symptoms of toxoplasmosis such as damage
to the eye, brain, or other organs.
Ocular toxoplasmosis, which damages the eyes, can lead to reduced vision,
blurred vision, pain (often with bright light), redness of the eye, and
sometimes tearing, according to the CDC.
Can this infections develop into a more serious illness in babies ?
Yes, the immune system in infants is not fully mature until after birth.
The babies of women who were exposed to toxo within a few months of
becoming pregnant or during pregnancy are at an increased risk for
developing a severe case of toxo. According to the NIH (U.S. National
Institutes of Health), pregnant women who newly contract the toxoplasmosis
parasite have a 40% chance of transmitting it to their unborn child. Women
who were first exposed to toxo more than six months before becoming
pregnant are not likely to pass the infection to their children.
Most infants have no symptoms at birth, but a small percentage may be born
with eye or brain damage. Unfortunately, the signs and symptoms of the
disease often appear a few months after birth.
What is meant by a baby developing "a more severe case of
toxoplasmosis" ?
Children born with toxoplasmosis can be afflicted with mental retardation,
convulsions, spasticity, cerebral palsy, deafness, and severely impaired
vision. The infant's head may be abnormally small (microcephaly) or
abnormally large due to increased pressure on the brain (hydrocephalus).
How is " toxoplasmosis diagnosis " Performed ?
The diagnosis of toxoplasmosis can be done using
a variety of methods. The difficulty lies in determining whether the
infection is acute or chronic. Acute infection can best be verified by
isolating T. gondii or T. gondii DNA from the patient's blood or finding
tachyzoites in tissue or bodily fluids. Congenital infection of fetuses
can be identified by the presence of cysts in the placenta or fetus.
The isolation of T. gondii tissue cysts is not sufficient to determine
whether the infection is still active or has entered the latent phase.
To differentiate the two, patients are subjected to several serological
exams, the specific combination of which depends on clinical category of
the patient. These exams include the Sabin-Feldman dye test, which tests
for IgG antibodies; ELISAs targeted at IgM, IgA and IgE; differential
agglutination tests and IgG avidity tests.
Of particular interest is determining acute infection in pregnant women,
due to the risk of congenital toxoplasmosis. This is complicated by the
fact that many women have existing IgG and IgM antibodies to T. gondii
from infection in the past. There are effective diagnostic techniques
that monitor changes in the mother's antibody expression over time, but
quick diagnosis is greatly preferred because fetuses often rapidly
become infected.
Driven by this need, Cynthia Press, Jose Montoya and Jack Remington at
the Palo Alto Medical Foundation identified a series of tests that are
effective at determining very early infection from a single sample of
maternal serum. This is based on the finding that VIDAS IgG avidity
tests usually fail during early infection because IgG titers are too
low. The recommended diagnostic procedure consists of looking for
positive results from the Sabin-Feldman dye test and an IgM ELISA, in
conjunction with a negative VIDAS IgG avidity test. This was determined
to be an effective set of criteria for diagnosing early acute infection,
which can then be followed up with early treatment to minimize the risk
of congenital infection.
How can toxoplasmosis be prevented ?
Since toxo usually causes mild to no symptoms, and a healthy immune system
prevents any remaining parasites in the body from causing further
symptoms, most people don't need to worry about getting this disease.
However, if you have a weakened immune system or are pregnant, there are
several steps you should take to prevent exposure to toxoplasmosis.
* If you have a weakened immune system, get a blood test for
toxoplasmosis. If your test is positive, your doctor can tell you if and
when you need to take medicine to prevent the infection from reactivating. * If you are planning on becoming pregnant, you may consider being tested
for toxo. If the test is positive, there is no need to worry about passing
the infection to your baby (since you should have immunity against the
parasite). * If you are already pregnant, you should discuss your risk of
toxoplasmosis with your doctor who may order a blood sample for testing. * Wear gloves when you garden or do anything outdoors that involves
handling soil since cats often use gardens and sandboxes as litter boxes.
Wash your hands well with soap and warm water after outdoor activities,
especially before you eat or prepare food. * Have someone else handle raw meat for you. If this is not possible, wear
clean latex gloves and thoroughly wash with soap and hot water any cutting
boards, sinks, knives, and other utensils that might have touched the raw
meat. Wash your hands well with soap and warm water afterward. * Cook all meat thoroughly, especially pork or veal.
Am I able to keep my cat ?
Yes, but if you have a weakened immune system or are pregnant, there are
some steps to take to avoid being exposed to toxo according to the Cornell
College of Veterinary Medicine.
Most importantly, you can help prevent your cats from getting infected
with toxoplasmosis. Feed them dry or canned cat food and keep them
indoors. Cats can become infected by eating or being fed raw or
undercooked meat that is infected with the parasite, or by eating infected
prey such as birds or rodents. Any cat that is allowed access to outdoors
should be kept off beds, pillows, or other furniture that you also use.
Don't bring a new cat into your house that might have been an outdoor cat
or might have been fed raw meat. Avoid handling stray cats and kittens.
Have your cat tested for the parasite. Your vet can answer any other
questions you may have regarding your cat and the risk for toxoplasmosis.
Have someone who is healthy and not pregnant change your cat's litter box.
If this is not possible, wear gloves and clean the litter box daily (the
parasite found in cat feces needs a few days after being passed to become
infectious). Wash your hands well with soap and warm water afterward.
Once infected with toxo, is my cat always able to spread the infection
to me ?
No, cats can only spread toxo in their feces for a few weeks after they
are first infected with the parasite. Like humans, cats rarely have
symptoms when first infected, so most people don't know if their cat has
been exposed to toxo. In fact, most infected cats appear healthy. There
are no good tests available to determine if your cat is passing toxo in
its feces.
Toxoplasmosis necessary Treatment -
Treatment is not necessary in case of toxoplasmosis
infection in a health person. Symptoms usually disappear within a period
of few weeks.
For pregnant women or persons who have weakened immune systems,
medications are available to treat toxoplasmosis.
In case of an infected pregnant woman the disease has to be treated with
utmost care. Research has shown that treating the mother can help
decrease the severity of the disease in the infant but does not
necessarily decrease the transmission of the infection from mother to
child. Infection in the pregnant mother can be treated with an
antibiotic called spiramycin
Kids with weakened immune systems often need to be hospitalized when
they develop toxoplasmosis, and those with AIDS may need to take
anti-toxoplasmosis medication for life.
Children born with congenital toxoplasmosis are treated with different
combinations of anti-toxoplasmosis medications, usually for 1 year after
birth. Treatment of congenital toxoplasmosis typically includes
pyrimethamine, sulfadiazine, and leucovorin for one year. Infants are
also sometimes given steroids if their vision is threatened or if the
protein level in the spinal fluid is high.
Medications to treat the infection in general are pyrimethamine,
sulfonamide drugs, folinic acid, clindamycin, and
trimethoprim-sulfamethoxazole..
Toxoplasmosis At A Glance
- Toxoplasmosis (toxo) is a disease caused by a parasite.
- Toxo is acquired from contact with cats and their feces.
- Toxo is also acquired from eating or touching raw or partly cooked meat.
- Symptoms can range from none to very severe.
- A woman who contracts toxo right before or during pregnancy can transmit
it to her baby with catastrophic consequences.
- People with immune deficiencies are at high risk for developing severe
signs and symptoms of toxo.
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