Human Infection with Toxoplasma
<http://www.cliniciansbrief.com/index.php?p=articles&newsid=3180>
By Sandra Sawchuk
2008/10/01
People may become infected with Toxoplasma gondii from a variety of sources, the most common of which are eating
raw or improperly cooked meat infected with oocytes, exposure to contaminated soil during gardening, eating
unwashed fruits and vegetables, and of course exposure from cat feces in litter boxes. In adults and adolescents,
severity of infection depends on immune status of the person. Infections in immunocompetent people are usually
asymptomatic, but fever, malaise, and lymphadenopathy can occur. Infections can be reactivated in people that
become immunocompromised, and clinical signs can involve any of the tissues invaded by the organism. Acute
maternal infection during pregnancy can cause congenital disease in the fetus, the risk for which is lowest in the first
trimester (10% to 25%) and highest (60% to 90%) during the third trimester. However, the severity of congenital
disease is highest if infection occurs during the first trimester; clinical manifestations range from mental retardation,
seizures, and blindness to death. The "classic triad" of chorioretinitis, intracranial calcifications, and hydrocephalus
occurs in fewer than 10% of cases. Initial diagnosis is most commonly made by antibody testing; however, the rate of
false-positive results necessitates confirmatory testing before treatment is started. The Sabin-Feldman dye test is the
"gold standard." Diagnosis of intrauterine infection is made via polymerase chain reaction testing of amniotic fluid.
Testing should be done in pregnant women with HIV and when prenatal monitoring raises red flags of conditions such
as hydrocephalus. Treatment of toxoplasmosis is usually limited to pregnant women and immunosuppressed people.
Treatment during pregnancy usually involves pyrimethamine and sulfadiazine and folinic acid (leucovorin) and can
reduce fetal infection by as much as 50%. Treatment of newborns greatly reduces retinal lesions.
COMMENTARY: This is an excellent review on human toxoplasmosis. I have found human medical professionals to
be quite biased regarding cats and their role in Toxoplasma transmission. I have been told by many pregnant
cat-owning clients that they were instructed by their physicians to "get rid of your cat," so it was refreshing to read an
article published in a human medical journal that presents a nonbiased, factual account on this protozoal infection.
Keeping cats indoors, avoiding raw or undercooked meat (for both cat and human), daily litter box cleaning,
gardening with gloves, and washing fruits and vegetables are all recommended methods to prevent this zoonotic
disease.
-Sandra Sawchuk, DVM, MS
Toxoplasmosis. Tamma P. PEDIATR REV 28:470-471, 2007.
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