Protozoa infections - Toxoplasmosis

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Immunocompetent persons with primary infection are usually asymptomatic, but latent infection can  persist  for  the  life  of  the  host.  In  immunosuppressed  patients,  especially  patients  with  AIDS,  the  parasite can reactivate and cause disease, usually when the CD4 lymphocyte count falls below 100  cells/mm3. 

Clinical presentation 

  • Altered mental status
  • Focal  neurological deficits
  • Seizures
  • Neuropsychiatric manifestations

Imaging Investigations 

  • Contrast head CT scan - demonstrates ring-enhancing lesions
  • Contrast brain MRI with diffusion weighted sequences (DWI)
  • CXR

Laboratory Investigations 

Toxoplasma serology (IgM) 

Non-pharmacological Treatment 

Similar to bacterial meningitis 

Pharmacological Treatment

For acute infection give: 

D:sulfadiazine (PO) 1g 6hourly for 6weeks 

AND 

D: pyrimethamine (PO) 100mg loading dose then 50mg /day for 6weeks 

AND 

S: folinic acid (PO) 10mg /day for 6weeks

After six weeks of treatment give maintenance treatment with 

D: sulfadiazine (PO) 500mg 6hourly 

AND  

D: pyrimethamine (PO) 25-50mg /day 

AND 

S:  folinic  acid  (PO)  10mg /day  until  CD4  counts  is  above  200cells/microlitre  and/or undetectable viral load for 3-6months 

For those allergic to sulphur replace sulfadiazine with 

S: clindamycin (PO) 450mg 6hourly for for 6weeks.