Protozoan parasite of human importance

Disease : Toxoplasmosis Agent : Toxoplasma gondii

Diverse routes of transmission

Tissue-inhabiting Apicomplexan. Zoonosis. At

risk groups.

Life cycle of Toxoplasma

Toxoplasma life cycle stages

Toxoplasma gondii : Modes of

transmission

• Ingestion of cyst-containing meat (carnivores)

• Ingestion of oocysts (environmental contamination)

• Congenital infection• Transfusion (rare)• Raw goat’s milk,

lambing, transplantation

Percentage of Toxoplasma infection associated with type of meat consumed

Country Beef (%)

Pork (%)

Lamb (%)

Salami (%)

Belgium 6 2 10 10Denmark 27 2 8 4Italy 12.5 3 0.5 12.5Norway 19 3 21 3Switz. 8 13 10 5

Adapted from Sukthana, 2006

Seropositivity rates

Continents and countries Seropositivity (%)

EuropeSpainAustriaFranceNorwayUKPoland

28.6%43%up to 75%10.9%57-93%46.4-58.5%

USA 16-40%

Central and South AmericaCosta RicaArgentina

76%72%

S.E. AsiaIndonesiaThailand

58%2.3-21.9%

Symptomatology : Toxoplasma

• Most infections benign• Rarely severe

– hepatitis, encephalomyelitis, myocarditis

• Few cases of retinochoroiditis which can progress to blindness

• At risk groups (see over)

Intra-uterine infections

• Severe clinical picture : retinochoroiditis, encephalomyelitis, hydrocephalus, microcephaly

• Most infections result in blindness, severe visual impairment and/or mental retardation

• Estimates 50-70 seriously affected births UK ; approx 3000 congenital cases USA

Toxoplasma in the immunocompromise

d host

• Immunosuppression, malignancy, AIDS, organ transplantation

• Neurological complications - meningoencephalitis or cerebral mass lesions : cerebral toxoplasmosis

• Headache, confusion, ataxia, hemiparesis, retinochoroiditis

• Endogenous versus exogenous infection

Cerebral toxoplasmosis : Centre for Disease Control (CDC) criteria for

diagnosis

• Recent onset of focal neurological abnormality consistent with intercranial disease or reduced consciousness

• Evidence from brain imaging of a lesion (CT or MRI)

• Positive serum antibody to T. gondii or response to treatment

Diagnostic tests for Toxoplasma

• Sabin-Feldman dye test (DT)• Enzyme immunoassay for T. gondii

specific IgM (EIA)• Immunsorbent agglutination assay

(ISAGA)• Enzyme immunoassay for IgG avidity• Isolation and culture of parasite • Direct detection by microscopy and PCR

Differential Diagnosis

• Immunocompetent adults (DT, IgM EIA)

• Pregnant women (maternal serum DT, IgM EIA, IgG avidity; Amniotic fluid culture or PCR)

• Neonates (DT, EIA, ISAGA for IgM, IgA)

• Organ transplantation (DT, IgM EIA)

• Immunodeficiency (serum and CSF : DT, EIA, ISAGA for IgM and IgA; PCR, culture, microscopy)

Prevention and control

• Avoid consumption of raw or undercooked meat

• Litterpans should be changed daily

• Wash hands after handling raw meat, litter pans & soil

• Pregnant women should avoid contact with cats

• Issue of prenatal screening

Program for mass screening and prophylactic treatment of pregnant women for T. gondii

Test 1 Test 2 Test 3 Group

IgG +veIgM -ve

No testNo treat

No testNo treat

Infection before pregnancy no risk

IgG +veIgM +ve

Repeat IgG after 3 wksTreat if high or rising

Possible infection soon after conceptionslight risk

IgG -veIgM -ve

Treat if IgG +ve

Treat if IgG +ve

No previous infection, if seroconver. high risk

Treatment : toxoplasmosis

• Only accepted treatment pyrimethamine with trisulfapyrimines for 1 month

• Intravenous clindamycin used to treat encephalitis in AIDS patients

• In France spiramycin has been used to treat toxoplasmosis in pregnancy

• Spiramycin is available in the US on a case-by-case basis

Seroprevalence of Toxoplasmosis by county of

maternal residance

0

5

10

15

20

25

30

35

40

45

L W K M D D

Seroprev %

Toxoplasma gondii and Schizophrenia

E. Fuller Torrey & Robert H. Yolken (2003)

Emerging Infectious Diseases 9 (11) 1375-1380