Hi cmo,
Let?s address the issue of getting toxoplasmosis twice, first. No, you
don?t get toxoplasmosis twice. Once you are exposed to Toxoplasma
gondii, your body produces antibodies to the parasite. These
antibodies protect you for life against a recurrence (recrudescence)
of T.gondii infection. You will be immune forever. The caveat is, if
you should become immuno-compromised later in life, by being on
chemotherapy, or developing HIV, you may be prone to developing
encephalitis (brain infection of T. gondii)
http://www.drjick.com/toxo2.php
Your doctor is correct, if you have a positive antibody test now, it
may indeed mean you had the infection previously. Depending on which
test you had, it may also mean you have it now, and something else
previously! Generally though, the titer rises during current
infection, and lowers during recovery. There is a good algorithm for
the antibody test on the page that is linked at the end of the next
paragraph.
If you are currently infected, your results will show: IgG positive
and IgM positive, with low IgG avidity. If you were previously
infected, your results would show IgG positive, and IgM negative, and
a high IgG avidity. (Avidity describes how strong the antibody binds
to the T.gondii organism)
http://www.dpd.cdc.gov/dpdx/HTML/Toxoplasmosis.asp?body=Frames/S-Z/Toxoplasmosis/body_Toxoplasmosis_serol1.htm
?After you're infected with T. gondii, the parasite forms cysts that
can affect almost any organ but that most often affect your brain,
skeleton and heart muscle. If you're generally healthy, your immune
system keeps the parasites at bay, and they remain in your body in an
inactive state for life. This provides immunity so that you can't
become infected with the parasite again. But if your resistance is
weakened by disease or certain medications, the infection can be
reactivated, leading to serious complications.?
http://www.cnn.com/HEALTH/library/DS/00510.html
T. gondii is an interesting parasitic infection, affecting about 30%
of Americans and British, and up to 65% of the French (due to eating
more uncooked and undercooked meat). T. gondii is something most
people never think of, yet is is a serious concern to pregnant women
and those with a compromised immune system. Should a pregnant woman
contract T.gondii, she can suffer miscarriage, or give birth to a
child with mental retardation, cerebral palsy, and/or serious eye and
ear problems. The good news, if you can call it that, is T.gondii is
not transmitted human to human.
T.gondii reproduces in the intestines of cats, and is shed in cat
feces, turning up in yard soil, and kitty litter boxes. Most people do
not exhibit any symptoms, and if one is asymptomatic, need no therapy.
If symptoms present, the patient is usually treated with pyrimethamine
and either trisulfapyrimidines or sulfadiazine. Some times clindamycin
is given, as an alternative drug. Pregnant women are treated with
spiramycin.
T.gondii is diagnosed in several ways:
Blood tests to detect the T.gondii antibody is the most common
method. The test should not be drawn until about 3 weeks following
exposure/symptoms. If the blood is drawn too early, the quantity of
blood antibodies present is too small to be detected, and may give a
false negative.The most accurate way to get a good set of results it
to have one sample drawn at 3 weeks post infection. This sample should
be processed and frozen, until the second sample is drawn, 2-3 weeks
later. Then BOTH samples should be sent to the lab and run together.
This eliminates testing variances in labs, reagents, method, humidity,
and technical bias. Some labs have a newer test that detects the
presence of the organism itself, and not just the antibody. The PCR
test, sometimes used to test for T. gondii, can?t distinguish between
current and past infection, and this may be the kind you had.
If you are seriously interested in having your blood tested, suggest
that your doctor order a TSP (Toxoplasma Serological Profile) With
this panel, you?ll get what we used to call ?The Works?! ?Recently,
several tests for avidity of toxoplasma IgG antibodies have been
introduced to help discriminate between recently acquired and distant
infection. Studies of the kinetics of the avidity of IgG in pregnant
women who have seroconverted during gestation have shown that women
with high avidity test results were infected with T. gondii at least 3
to 5 months earlier (time to conversion from low to high avidity
antibodies varies with the method used). Because low avidity
antibodies may persist for many months, their presence does not
necessarily indicate recently acquired infection.?
http://www.pamf.org/serology/clinicianguide.html#toxosero
A tissue biopsy or spinal fluid culture can find the organism, but are
more painful methods, and not as sensitive as the blood tests. Often
these methods are used at autopsy.
A needle biopsy can be employed for T.gondii. The needle has a bore
width adequate to take a ?plug? of muscle, which is examined under a
microscope for parasites. To collect CSF (cerebral spinal fluid) for
culture, a lumbar puncture (spinal tap) will be performed.
http://www.nlm.nih.gov/medlineplus/ency/article/003924.htm
Diagnostic imaging, such as MRI, CAT, ultrasound or X-rays can
visualize if any parasites have made their way to the brain, heart or
organs.
http://my.webmd.com/hw/hiv_aids/hw5932.asp
?A positive antibody test, on the other hand, doesn't necessarily mean
you're actively infected. In many cases, it's a sign that you were
infected at some time in your life and are now immune to the disease.
Further tests can help determine when the infection occurred, based on
the types of antibodies in your blood, and whether the levels of these
antibodies are rising or falling. This is especially important if
you're pregnant or living with HIV/AIDS.?
http://www.ecureme.com/emyhealth/data/Toxoplasmosis.asp
?The most common method of detecting Toxoplasma infection is through
antibody testing. Blood tests detect the presence of antibodies to the
Toxoplasma parasite called IgG or IgM. Positive IgG indicates past
exposure and is evidence of immunity. Positive IgM is supposed to
indicate current infection, but there have been problems with
commercial testing for IgM resulting in a high level of
false-positives. Universal screening is not practiced in the U.S.?
http://www.drjick.com/toxo2.php
This page has several pictures of T.gondii. Click the thumbnail
picture to see the enlarged version. The tachyzoites are particularly
cute, and somewhat resemble malarial parasites!
http://www.dpd.cdc.gov/dpdx/HTML/ImageLibrary/Toxoplasmosis_il.htm
I wish I had found this site first, and not last. It covers ALL your
questions! You can also see the life cycle of T.gondii parasites.
(Warning-there is a graphic picture of a baby born with hydrocephalus
caused by T.gondii.)
http://www.modares.ac.ir/elearning/Dalimi/Proto/Lectures/week10.htm
Additional information:
http://www.intelihealth.com/IH/ihtIH/WSIHW000/9339/24704.html
I hope this has answered your questions. If not, or if I have
duplicated information you already had, please request an Answer
Clarification, before rating. This will enable me to assist you
further, if possible.
Regards,
crabcakes
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