Parasites detection

Figure 8.2 Sample preparation protocols, currently employed in malaria parasite detection by LDMS. Both protocols require less than 50pl blood, obtained by either finger-stick or phlebotomy.

Jacobson DJ et al. Persistent, systemic, asymptomatic infections oJAlbugo Candida, an oomycete parasite, detected in three wild crucifer species. Can J Bot 76 739-750, 1998. 

The usual diagnostic methods, both skin tests and specific IgE with whole Anisakis extract, have a good sensitivity but a low specificity to such a degree that in 22% of blood donors specific IgE to the parasite is detected [40] and at least 20% of patients with acute urticaria have positive skin prick tests with whole Anisakis extract [41 ]. As for BAT with whole Anisakis extract, Gonzalez-Munoz et al. [42] report a sensitivity of 96% with a specificity of 96%, which are clearly higher values than those from specific IgE. 

Simplest method of diagnosis is detection of oocysts by modified acid-fast staining of a stool specimen. Standard ova and parasite test does not include Cryptosporidium. 

The limit of detection of the assay was estimated to be 200 parasites/ml of blood. The detection limit is well within the range of sensitivity needed to diagnosis trypanosomiasis, as the parasitemia may vary from 5000 to 1,500,000 parasites/ml (Vickerman, 1974). The bDNA assay was compared with buffy coat microscopy for detection of T brucei in 56 blood samples (36 buffy coat positive and 20 buffy coat negative by microscopy). There was complete concordance between the results of the two tests in terms of identifying specimens as positive of negative. However, the numbers of parasites observed by microscopy were lower overall than those calculated with the bDNA assay. The authors suggested that the excess of leukocytes in the buffy coat could interfere with the microscopic detection of typanosomes, resulting in lower apparent parasitemia than the true value. 

Detection by LDMS and structural elucidation of other secondary metabolite products, generated in the host during the onset of the parasite disease, is discussed. These molecules may serve as additional biomarkers for rapid malaria diagnosis by LDMS. For instance, choline phosphate (CP) is identified as the source of several low-mass ions observed in parasite-infected blood samples in addition to heme biomarker ions. The CP levels track the sample parasitemia levels. This biomarker can provide additional specificity and sensitivity when compared to malaria detection based on heme ion signals alone. Furthermore the observed elevated CP levels are discussed in the context of Plasmodium metabolism during its intra-erythrocytic life cycle. These data can... 

Figure 8.3 Positive ion LD TOF mass spectrum of blood from a P. vivax infected human patient (only asexual parasites have been observed by microscopy estimated parasitemia approximately 72 parasites/pl). Protocol C is used for sample preparation estimated number of parasites deposited per well is approximately 90. A commercial TOF system is used laser wavelength 337 nm. All one hundred single laser shot spectra, obtained from hnear scanning of an individual well, are averaged (no data smoothing). The characteristic fingerprint ions of detected heme are denoted.

In the first LDMS-based detection of malaria in human subjects (unpublished), lOOpl P. falciparum or P. v/vax-infected blood samples, grouped into three different parasitemia ranges—low (10-150 parasites/pl), mid (2 x 103 parasites/pl), and high (25 x 103-60 x 103 parasites/pl)—have been examined using both sample preparation protocols. Parasitemia levels in these samples were previously determined independently for each sample by optical microscopy examination of blood smears. The LDMS data clearly indicate that... 

Demirev, P. A. Feldman, A. B. Kongkasuriyachai, D. Scholl, P. Sullivan, D. J. Kumar, N. Detection of malaria parasites by laser desorption mass spectrometry. 

Most immunodiagnostic tests used today for parasitic infections detect antibody. In recent years, the sensitivity and specificity of many such tests have improved. A number of antigen detection tests have recently been described and show promise, but none of these tests are currently available commercially. 

The direct wet mount made from unconcentrated fresh feces is most useful for the detection of the motile trophozoites of intestinal protozoa and the motile larvae of Strongyloides spp. It is also useful for the detection of protozoan cysts and helminth eggs. For fixed feces, the direct wet mount may allow the detection of parasites which do not concentrate well. This method is also useful for the examination of specific portions of feces, such as flecks of blood or mucus. 

The Baermann concentration technique has greater sensitivity for the detection of strongyloides larvae than do the standard concentration techniques described above. This technique is useful clinically for the diagnosis and monitoring of therapy of strongyloides infections, and it is useful epidemiologically for the examination of soil for the larvae of nematode parasites. 

Sironi et al, 1995). In surveys of the human parasite B. malayi, Wolbachia was detected by PCR in all females and in 25% of males (Taylor et al, 1999). Re-analysis of male worms using a nested PCR revealed that all individual male worms were infected (Taylor et al, 2000). 

Masui, S., Kamoda, S., Sasaki, T. and Ishikawa, H. (1999) The first detection of the insertion sequence ISW1 in the intracellular reproductive parasite Wolbachia. Plasmid 42, 13-19. 

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