Parasitic Infections Diagnosis

Serological Tests for Parasitic Infections

• 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.

Malaria

• 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.

Toxoplasmosis

• 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.

Cryptosporidiosis

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

Intestinal Helminths

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

Trichinosis

• 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.

Skin Tests

• 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.

Other Parasitic Infections

• 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.