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Jose L. Guzman III
Toxoplasmosis Fact Sheet:
Description/Etiology:
Toxoplasmosis is an infection caused by the protozoan parasite
caused by Toxoplasma gondii. It can affect most warm blood animals,
including humans. Toxoplasmosis can affect the fetus while the mother is
pregnant (called congenital Toxoplasmosis) and people who have
weakened immune systems.
Humans become infected by ingesting uncooked meat with the
parasite, touching food, or water contaminated with cat feces.
Transmission can also be from transplacental transmission, or via blood
transfusion or organ transplantation. The main 2 routes of infection are oral
and congenital.
The parasite has 3 stages 1) tachyzoites: rapidly
multiplying, 2) bradyzoites: slowly multiplying and
leading to dormacy, and 3) oocysts:which are
excreted by infected cats in their feces.
Cats are the only definitive hosts for T. gondii in all
3 stages, and are the main reservoirs of infection.
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Facts & Figures:
Toxoplasmosis is one of the most common causes of human parasitic
infections worldwide, with 22.5% of all persons over the age 12 in the US
having antibodies to the parasite.
Congenital toxoplasmosis (infection transmitted in utero) occurs in 1 in
3000 to 1 in 10,000 live births in the US.
Risk Factors:
Risk factors for T. gondii infection include eating raw or undercooked
pork, mutton, lamb, beef, mince meat products, mince meat products, or
wild game meat, cleaning the cat litter box, contact with soil (gardening
and yard work), and eating raw or unwashed vegetables or fruits.
Clinical Presentation/ Signs & Symptoms:
Toxoplasmosis can be categorized in 4 groups.
a). acquired in the immunocompetent host (i.e. HIV patient), b). acquired
or reactivated in the immunosuppressed host (i.e. chemotherapy patient),
c). congenital infection (obtained in utero), and d). ocular toxoplasmosis
disease.
With congenital infection, the rate of transmission to the fetus and
severity of the disease in the baby depends according to when in the
pregnancy the woman acquires the infection. Getting toxoplasmosis in
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the first trimester leads to congenital infection 10-20% of the time, with
symptoms including: severe microcephaly (small head), or
hydrocephalous (big head), severe chorioretinitis (an inflammation of the
choroid ,thin pigmented vascular coat of the eye and retina of the eye.),
hearing loss, and mental retardation.
Getting toxoplasmosis in the last trimester results in 80-90% congenital
infection to the baby, usually asymptomatic at birth. Many of these
children will acquire ocular toxoplasmosis disease later.
Ocular toxoplasmosis disease is an important cause of chorioretinitis in
the US, and can result from congenital or acquired toxoplasmosis
infection. These patients can present with unilateral or bilaterally disease.
Typical findings of ocular toxoplasmosis disease include white lesions with
an overlying and intense vitreal inflammatory reaction.
The disease can affect the brain, lung, heart, eyes, or liver. Symptoms
in persons with otherwise healthy immune systems: enlarged lymph nodes
in the head and neck, headache, mild illness with fever, similar to
mononucleosis, muscle pain, and sore throat.
Symptoms in immunosuppressed persons: confusion, fever, headache,
retinal inflammation that causes blurred vision
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Diagnosis:
Tests to determine infection or to find cysts: include brain biopsy, cranial,
CT scan, MRI of head, serologic titers for toxoplasmosis, and patent signs
of toxoplasmosis.
Treatment:
Treatment depends on when the patient obtained the infection.
Immunocompetent patients are not treated unless symptomatic. If
symptoms are severe, they are treated with medications for 2-4 weeks.
Medications to treat the infection include an antimalarial drug and
antibiotics. AIDS patients should continue treatment for as long as their
immune system is weak to prevent the disease from reactivating.
If the patient is pregnant while obtaining infection, she will receive
antitoxoplasma treatment with folic acid, for 4 weeks, this will result in less
disease to the infant. Hydrocephalous (extremely large head) of infant on
ultrasound, has been used as indication for termination of pregnancy.
Patients with ocular toxoplasmosis will depend on severity of
inflammatory response, proximity of retinal lesions to the optic disk.
Chorioretinitis can be self-limiting, or may require treatment with
antibiotics for upto 3 weeks.
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References:
Freeman, K., Hooi, K., Andrea, P., et al. (2008). Predictors of
retinochorioiditis in children with congenital toxoplasmosis: Europe,
prospective study. Downloaded 6/30/09 at
http://www.pediatrics.org/cgi/content/full/121/5/31215
McAuley, J. (2008). Toxoplasmosis in children. The Pediatric Infectious
Disease Journal, 27: 161-163.
McCance, K., Huether, S. Pathophysiology: The Biologic Basis for Disease in
Adults and Children, 6th ed. ST. Louis, MO: Mosby, 2006: 579.
Montoya, J. & Liesenfeld, O. (2004). Toxoplasmosis. The Lance, 363: 196576.
Wallon, M., Kodjikian, L., Binquet, C. et al, (2004). Long-term ocular
prognosis in 327 children with congenital toxoplasmosis. Pediatrics,
(113)6:1567-1572.
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