Microsporidia |
Light microscopy, TEM, PCR, real-time PCR, IFAT, DAT |
Light microscopy is cheap and applicable to any clinical specimen; however, differentiation of species may be difficult by light microscopy; transmission electron microscopy may be useful for differentiation of species, although it can be expensive; several PCR and real-time PCR assays have been developed for detection of various species, although PCR requires a special apparatus; real-time PCR can be more rapid than conventional PCR, as it does not require agarose gel electrophoresis; generally, real-time PCR is more sensitive than conventional PCR; sequencing of PCR products may be necessary for species differentiation; indirect fluorescent antibody tests and DAT are available for some species only |
Leishmania |
Conventional and real-time PCR, light microscopy, culture systems, serological techniques, DAT, rK39 dipstick test, latex agglutination test, QBC tube technique |
Staining of blood films followed by light microscopy is definitive but is less sensitive than molecular techniques; real-time PCR can also be used to monitor patients' responses to therapy but requires a special apparatus; sequencing of PCR products can also allow differentiation of species; culture systems are useful but may be impractical; in Ethiopia DAT is preferred for diagnosis of L. donovani infection, as it is cheap, rapid, and sensitive; the rK39 dipstick test is cheap, rapid, and sensitive for diagnosis in ICT patients; however, the rK39 test demonstrated low sensitivities of ∼20% in European VL patients infected with HIV; the latex agglutination test is sensitive and noninvasive (applied to urine specimens); enzyme-linked immunosorbent assay and other serological techniques may be of limited use in IC patients, as circulating antibodies may not be detected during an active infection; the QBC tube technique is useful for the diagnosis of VL |
Trypanosoma cruzi |
Light microscopy, real-time PCR, PCR, ELISA, IFAT, QBC tube technique |
Light microscopy is definitive; trypanosomes are more readily observed in peripheral blood specimens in the acute stage and in IC patients; the blood stains are useful for blood stages, and hematoxylin and eosin stains are used for diagnosis of the intracellular stages, as seen in solid tissues; live, motile trypanosomes may be observed microscopically in the buffy coat or CSF (if CNS involvement is apparent); PCR and real-time PCR are sensitive but require a special apparatus; PCR can also be useful for monitoring treatment efficacy; the QBC tube technique is useful for diagnosis during the acute phase of Chagas' disease but is less useful during the chronic phase of the disease |
Trypanosoma brucei rhodesiense, Trypanosoma brucei gambiense
|
Light microscopy, PCR, real-time PCR, ELISA, CATT, QBC tube technique |
The blood stains are useful for light microscopic diagnosis when applied to blood or CSF; the microhematocrit centrifugation technique also enables the visualization of live motile trypanosomes microscopically; several PCRs and real-time PCRs are also available; PCR is sensitive and can allow differentiation of T. brucei subtypes; enzyme-linked immunosorbent assay is also useful; the CATT is available for T. b. gambiense sleeping sickness and is the most widely used technique in areas of endemicity, as it is cheap, rapid, and sensitive; a CSF white blood cell count is useful to predict the stage of sleeping sickness; the QBC tube technique has demonstrated greater sensitivity for detection of African trypanosomes than the microhematocrit centrifugation technique |
Non-human-infecting Trypanosoma
|
Light microscopy, various molecular techniques |
No specific diagnostics are available, as human infections are rare; infections are typically diagnosed by a combination of light microscopy and various molecular techniques |
Lower trypanosomatids |
TEM, light microscopy, various molecular techniques |
As with the non-human-infecting Trypanosoma spp., no specific diagnostics are available, as human infections are rare; infections were typically diagnosed by a combination of light microscopy and various molecular techniques; transmission electron microscopy was used in 1 case |
Toxoplasma gondii |
Light microscopy, PCR, real-time PCR, ELISA, IgG avidity test for pregnancy |
Observation of live free tachyzoites in stained smears of blood or CSF is diagnostic of an active infection; enzyme-linked immunosorbent assay can be useful but fails to differentiate between active and benign infections; PCR performed on peripheral blood is also diagnostic for an active Toxoplasma infection; real-time PCR assays are available, which are extremely sensitive and specific. The IgG avidity test is useful in pregnancy to predict the risk that a Toxoplasma infection poses to the fetus; however, the results of serological tests can be complex and difficult to interpret for pregnant woman and neonates |
Neospora caninum |
Serology, PCR |
Tachyzoites of Neospora are virtually indistinguishable from those of Toxoplasma; as such, light microscopy cannot differentiate the two; few diagnostics are available for human infections, as human neosporosis has never been reported; however, various serological techniques and PCR assays have been developed, which show good sensitivity and specificity |
Babesia |
Light microscopy, PCR, laboratory rodent inoculation, ELISA, IFAT, QBC tube technique |
Microscopic analysis of stained blood smears is useful for diagnosis in the early stages of infection or in IC patients; live-rodent inoculation is sensitive and was once used for diagnosis but has been abandoned due to practicality issues; PCR can be applied to blood specimens and is sensitive and extremely useful for the characterization of new isolates; enzyme-linked immunosorbent assay and IFAT may be useful for diagnosis of B. microti infections but are less applicable to B. divergens infections; for definitive confirmation of Babesia infection at the species level, amplification of the SSU rDNA genes by Babesia-specific PCR followed by sequencing of the PCR product can be performed; the QBC tube technique can also be used for the microscopic diagnosis of Babesia infection |
Acanthamoeba (GAE) |
Light microscopy, cultivation, IFAT, PCR |
Acanthamoeba spp. can be identified in Gram or Giemsa stains of CSF; calcofluor white can also be used for microscopic detection of Acanthamoeba; cultivation of trophozoites from CSF or tissue lesions by inoculation of the specimen onto neomycin-nalidixic acid agar plates seeded with a layer of Escherichia coli or Enterobacter aerogenes cells is a useful diagnostic tool; cultivation of Acanthamoeba can also provide the material for downstream molecular characterization; indirect fluorescent antibody techniques and PCR are also available; PCR is probably the most sensitive technique available for diagnosis of Acanthamoeba infection |
Balamuthia (BAE) |
Light microscopy, PCR, IFAT, electron microscopy |
Several stains are useful for light microscopic diagnosis, although the hematoxylin and eosin stain is usually applied to fixed tissue sections; however, Balamuthia trophozoites may be difficult to see; the use of an immunofluorescent antibody technique is a sensitive and specific alternative to light microscopy and is the gold standard for diagnosis of Balamuthia infection; PCR is also useful for diagnosis, as it is sensitive; some PCR assays can distinguish between Balamuthia and other free-living amoebae; electron microscopy is useful, although it is expensive |
Naegleria fowleri (PAM) |
Light microscopy, PCR, real-time PCR, cultivation |
As the onset of PAM is rapid, live, motile trophozoites can be readily observed in wet mounts of patient CSF; light microscopy of fixed, stained tissue smears is also useful. PCR and real-time PCR are available; cultivation of Naegleria from CSF enables downstream molecular analysis of isolates |
Sappinia pedata |
Light microscopy, PCR |
Only 1 reported case, which was diagnosed by light microscopy; recently, 3 real-time PCR assays were also developed for Sappinia spp. |