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Chapter: Medicine Study Notes : Infectious Diseases

Toxoplasmosis - Parasitology

Main source: cysts in meat. Also kitten faeces (eg cyst in garden – pregnant gardeners should wear gloves).

Parasitology

 

Toxoplasmosis

 

·        A protozoa/parasite

 

·        Main source: cysts in meat. Also kitten faeces (eg cyst in garden – pregnant gardeners should wear gloves)


·        Presentation:

o  Immunocompetent:

§  Lymphadenopathy (eg unilateral)

§  Maybe: fever, myalgia, acute pharyngitis, hepatosplenomegaly, atypical mononucleosis

§  Usually self-limiting – may take months to settle 

§  If persistent/recurrent lymphadenopathy ® ?Need for treatment

o  Immunodeficient:

§  Acquired or reactivated 

§  AIDS most common: CNS involvement (solitary space occupying lesion, encephalitis), also myocarditis, hepatitis

§  Less common in transplants and encephalitis 

o  Ocular toxoplasmosis: most cases in adolescents and adults ® reactivation infection. ® Blurred vision, photophobia, multiple retinal lesions 

o  Congential Toxoplasmosis:

§  29% fetal infection if mother has primary CMV infection

§  Highest risk in 3rd trimester (1st trimester may miscarry)

§  Complications: spontaneous abortion, premature, still birth

§  Surviving neonates: bilateral choroido-retinitis.  In severe cases, TORCH type symptoms


·        Lab diagnosis:

o  PCR test for toxoplasmosis: amniotic fluid, CSF (AIDS patients) 

o  Lymph node biopsy ® characteristic histology

o  Serology:

§  IgM antibody after 5 – 14 days, peaks at 2 – 4 weeks, traces for up to a year

§  IgG: high levels for up to 6 months, declines slowly over years

§  Avidity test: can differentiate between acute phase „immature‟ IgG and „mature‟ IgG


·        Treatment: 

o  Pyrimethamine (Gold standard, but gives bone marrow suppression + give folate) + sulphadiazine (not available in NZ)

o  Pyrimethamine + clindamycin (gives C. difficile diarrhoea)


·        Spiramycin (only one safe in pregnancy)

 

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