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MANAGEMENT
OF OPPORTUNISTIC INFECTIONS
IN
HIV-POSITIV PATIENTS
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FACT
SHEETS
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Toxoplasmosis
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A Protozoal
Infection
Causative organism
Toxoplasma gondii
Symptoms of active infection
Encephalitis
Toxoplasmosis in HIV-infected patients may commonly present
as encephalitis, pneumonitis or chorioretinitis. Encephalitis
is most common, with clinical features usually similar
to those associated with an intracranial lesion, such
as severe headache, focal neurologic deficits, fever or
confusion. Altered consciousness, seizures or abnormal
behaviour may also be present.
Pneumonitis
Cough, shortness of breath and a reticulonodular radiograph
pattern are the most common features of interstitial pneumonitis
caused by Toxoplasma gondii.
Chorioretinitis
Common features of chorioretinitis are eye pain, photophobia
and visual loss. Multiple necrotizing nodular white infiltrates
are seen on the retina. Unlike CMV retinitis, vasculitis
is not present. Most patients with AIDS in whom chorioretinitis
is diagnosed also have encephalitis and the treatment
is the same.
Diagnostic procedures
Most patients with cerebral toxoplasmosis have multiple
space-occupying lesions throughout the brain substance
which can be visualized on a MRI scan with gadolinium
contrast, or CT scan with double contrast. The brain lesion
in AIDS patients most often confused with toxoplasmosis
is that of a CNS lymphoma. |
 CT
scan post Multiple granulomas (arrows)surrounded
by minimal vasogenic edema. Presence of multiple
lesions with a target sing and positive toxoplasma
titre suggest toxoplasmosis |
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A presumptive diagnosis may be considered in patients
with CD4 counts < 200 cells/ l, anti-Toxoplasma IgG
antibody in the serum and consistent clinical features
that most often relate to the CNS, supported by characteristic
neuroimaging studies.
Treatment
Treatment of choice is sulfadiazine 1 gm orally q 6
hours plus pyrimethamine 200 mg oral loading dose, followed
by 50 to 75 mg orally o.d., and folinic acid 10-20 mg
o.d. to protect the bone marrow from the megaloblastic
effect of pyrimethamine. (Dannemann et al Ann Intern
Med 1992; 116: 33) Treatment should continue for at
least 4 to 6 weeks or longer before consideration is
given to reducing drug dosages and adopting lifelong
maintenance therapy. Maintenance therapy is required
because relapse can occur in up to 80% of patients who
have recovered from an episode of toxoplasmosis.
Clindamycin 600 mg I.V. q 6 hours, combined with the
same doses of pyrimethamine and folinic acid described
above, is as effective as sulfadiazine for the short
term treatment of toxoplasmosis. (Dannemann et al Ann
Intern Med 1992; 116: 33; Luft et al N Engl J Med 1993;
321: 995).
Trimethoprim-sulfamethoxazole in PCP doses as well as
azithromycin, have been used to treat toxoplasmosis
with success rates inferior to sulfadiazine-pyrimethamine.
Prophylaxis
Primary prophylaxis
HIV-infected persons at risk for toxoplasmosis should
receive prophylaxis as a high priority. Prophylaxis
is indicated for persons having positive T gondii serology
(IgG) and CD4 count of less than 100 cells/µl.
Data indicate that sulpha-containing regimes such as
those used for PCP prophylaxis are also effective for
prevention of toxoplasmosis.
Preferred for primary prophylaxis of toxoplasmosis
- One trimethoprim - sulfamethoxazole double
strength tablet/day
- One trimethoprim - sulfamethoxazole single
strength tablet/day
- One trimethoprim - sulfamethoxazole double
strength tablet 3 times/week
Secondary prophylaxis
After induction therapy for toxoplasmosis, life-long
maintenance (secondary prophylaxis) is recommended to
prevent relapse.
Pyrimethamine 25-50 mg o.d. orally plus sulphadiazine
1 gm b.i.d. or 500 mg q.i.d. orally plus folinic acid
10-20 mg/day orally is the preferred regime.
Drug interactions
Pyrimethamine may not be well absorbed with didanosine.
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