Parasitic Infections Diagnosis

Study Notes

Kala-azar: Indirect hemagglutination, CIEP, and DOT-ELISA are usually positive, while complement tests using WKK antigen are relatively less sensitive.
Kala-azar: Indirect fluorescent antibody test is positive early in the disease, even before symptoms appear, and becomes negative within 6 months of cure.
Kala-azar: rK39 micro ELISA test is a qualitative immunochromatographic assay for detecting antibodies to Leishmania.

Indirect immunofluorescence, ELISA, and IHA are sensitive and specific, but not useful for diagnosing acute malaria due to persisting antibodies.
A negative test may help exclude malaria.
Serological tests are useful in epidemiological surveys for malaria.
Molecular assays, such as antigen capture for HRP-2 and pLDH, have been applied for developing rapid dipstick tests.

Serological tests offer the most useful diagnostic method in toxoplasmosis.
The original Sabin-Feldman dye test is no longer in use, but IIF, IHA, and CFT were other useful diagnostic methods.
ELISA is routinely used in Toxoplasma serology, providing titers of IgM and IgG antibodies separately for better interpretation.

Indirect fluorescent antibody and ELISA using purified oocysts as antigens have been used to detect circulating antibodies specific to Cryptosporidium parvum.

Antibodies can be demonstrated in most intestinal helminthiases, but extensive cross-reactions limit their use in diagnosis.

Serology is very useful in diagnosing trichinosis.
Bentonite flocculation slide tests and CFT become positive 3-4 weeks after infection.
Indirect immunofluorescence becomes positive even earlier, and ELISA is also available.

Intradermal tests have been used in many parasitic infections, but specificity is relatively low.
Casoni's test is used for hydatid disease, but has been largely replaced by serological tests.
Leishmanin (Montenegro) test is used to measure delayed hypersensitivity in leishmaniasis.

Toxocariasis: High titers in serological tests are obtained in visceral larva migrans, but specificity is low due to cross-reactions with intestinal nematode antigens.
Filariasis: Indirect hemagglutination and bentonite flocculation tests with antigen from Dirofilaria immitis give positive reactions in patients, and high titers in tropical pulmonary eosinophilia.
Filariasis: Immunochromatographic card test (ICT) is a new and rapid filarial antigen test that detects soluble filarial antigens.