Toxoplasmosis

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"

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 -