Page 110 - AIDSBK23C

Page 110

inflammation, the greater the likelihood of finding cysts. Larger areas of inflammation are
usually accompanied by some cellular necrosis.[475]
Sometimes, cysts may be difficult to distinguish from cytomegalic cells that have
intracytoplasmic basophilic inclusions in which the plane of sectioning has missed the nucleus.
Cytomegalovirus basophilic bodies tend to be more pleomorphic than bradyzoites, and T gondii
cyst walls are thicker than cytomegalic cell borders. Macrophages containing Histoplasma
capsulatum tend to be more irregular in outline with fewer yeasts than the rounded pseudocysts
of toxoplasmosis with many small bradyzoites.
Patients with HIV infection who lack antibody to Toxoplasma may avoid infection by not
eating raw or undercooked meat, by hand washing after contact with raw meat or soil, by
washing raw fruits and vegetables before eating them, and by reducing or avoiding contact with
cat litter boxes. In the advanced stages of AIDS when the CD4 lymphocyte count is <100/µL
and when there is serologic evidence for Toxoplasma infection, patients may receive
prophylaxis. Trimethoprim-sulfamethoxazole (TMP-SMZ) used for prophylaxis against
Pneumocystis jiroveci (carinii) pneumonia (PCP) is also effective for prevention of
toxoplasmosis and should be considered for patients with anti-toxoplasma antibodies who have a
CD4 count <100/microlier. The alternative prophylactic regimen consists of sulfadiazine plus
pyrimethamine and leucovorin.[208]
Pyrimethamine-sulfadiazine with folinic acid therapy for cerebral toxoplasmosis is often
successful for treating diagnosed infections. A response to therapy occurs in about two thirds of
cases.[477] Death from toxoplasmosis occurs in slightly less than half of AIDS patients infected
with T gondii at autopsy. Of these, central nervous system involvement is responsible for death
in virtually all instances. Toxoplasma myocarditis causing patient demise occurs
sporadically.[396,476]