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PubMed1991

Sodium azide: ineffective as a faecal preservative for parasitological diagnosis.

Sodium azide was compared with 10% formalin to evaluate sodium azide's effectiveness as a faecal preservative for intestinal helminths and protozoa. Faecal specimens collected from Haiti were preserved in sodium azide and in 10% formalin and analysed after 1.5, 6.5 and 11.5 weeks by examining direct wet-mount preparations. Sodium azide did not preserve the morphology of either helminths or protozoa as well as 10% formalin did. However, sodium azide prevented embryogenesis of helminth eggs, while some helminth eggs in 10% formalin contained living larvae. Biosafety guidelines regarding the toxicity, reactivity, and disposal of sodium azide were strictly followed. Use of 10% formalin is a significantly better choice than sodium azide for preserving parasites when accurate identification of parasites and biosafety are the main concerns.

Adolescent↗
PubMed1983

Comparison of polyvinyl alcohol- and formalin-preserved fecal specimens in the formalin-ether sedimentation technique for parasitological examination.

A total of 965 paired fecal specimens preserved in polyvinyl alcohol fixative and Formalin were processed by the Formalin-ether sedimentation technique. The effectiveness of the concentration procedures with material from each preservative was determined by comparing both diagnostic efficiency (percent identified) and quantitative egg and semiquantitative cyst counts. Of the 319 infections, 69.5% were detected in concentrates from both preservatives, 6.9% from polyvinyl alcohol only, and 23.5% from Formalin only. The egg and cyst counts were consistently higher from the specimens preserved in Formalin for most of the species of organisms recovered. These findings strongly support the use of Formalin-fixed specimens for the Formalin-ether concentration technique.

Ether↗
PubMed1990

Evaluation of direct wet mount parasitological examination of preserved fecal specimens.

A retrospective study covering a 12-year period was performed to determine the contribution of the direct wet mount microscopic examination to the identification of intestinal parasites in preserved fecal material. It was determined that each of 898 specimens contained at least one parasite when processed by the direct wet mount, concentration, and trichrome staining procedures. Of these procedures, the direct wet mount examination was solely responsible for the identification of 45 (2.9%) of 1,581 parasites identified. This is in contrast to the 15.1 and 12.5% which were found exclusively by the concentration and trichrome methods, respectively. These percentages may vary, depending on the prevalence of parasites and the stages present in the stool specimen.

Animals↗
PubMed1999

Evaluation of Streck tissue fixative, a nonformalin fixative for preservation of stool samples and subsequent parasitologic examination.

We undertook a study to evaluate Streck tissue fixative (STF) as a substitute for formalin and polyvinyl alcohol (PVA) in fecal preservation. A comparison of formalin, PVA, (mercuric chloride based), and STF was done by aliquoting fecal samples into each fixative. Stool specimens were collected in Haiti, and parasites included Cyclospora cayetanensis, Giardia intestinalis, Entamoeba coli, Iodamoeba butschlii, Endolimax nana, Ascaris lumbricoides, Trichuris trichiura, Strongyloides stercoralis, and Necator americanus. Preserved stools were examined at various predetermined times (1 week, 1 month, and 3 months) to establish the quality of the initial preservation as well as the suitability of the fixative for long-term storage. At each time point, stool samples in fixatives were examined microscopically as follows: (i) in wet mounts (with bright-field and epifluorescence microscopy), (ii) in modified acid-fast-, trichrome-, and safranin-stained smears, and (iii) with two commercial test kits. At the time points examined, morphologic features remained comparable for samples fixed with 10% formalin and STF. For comparisons of STF- and 10% formalin-fixed samples, specific findings showed that Cyclospora oocysts retained full fluorescence, modified acid-fast- and safranin-stained smears of Cryptosporidium and Cyclospora oocysts were equal in staining quality, and results were comparable in the immunofluorescence assay and enzyme immunoassay commercial kits. Stool fixed in STF and stained with trichrome showed less-than-acceptable staining quality compared with stool fixed in PVA. STF provides an excellent substitute for formalin as a fixative in routine examination of stool samples for parasites. However, modifications to the trichrome staining procedures will be necessary to improve the staining quality for protozoal cysts fixed in STF to a level comparable to that with PVA.

Animals↗
PubMed1999

Chagas' disease diagnosis: comparative analysis of parasitologic, molecular, and serologic methods.

During the course of chronic chagasic infection, low parasitemia levels prevent parasite detection by current techniques such as hemoculture and xenodiagnosis. Since serologic tests have sensitivity but lack specificity, molecular assays based on the polymerase chain reaction (PCR) have been proposed as alternative tools for parasite detection in individuals with chronic Chagas' disease. A variable degree of PCR efficiency has been reported in the literature and illustrates the need for further evaluation of large numbers of chagasic patients. In this study, we compared an optimized PCR technique with hemoculture and complement-mediated lysis (CoML) in 113 individuals from or living in endemic areas of Brazil who had conventional serologic results that were either positive, negative, or inconclusive. The PCR amplification yielded positive results in 83.5% (66 of 79) of individuals with positive serology, 47.6% (10 of 21) with negative serology, and 46.2% (6 of 13) with inconclusive serology. Of 10 patients with negative serology and positive PCR result, eight (80%) had positive CoML, indicating that they could have been chagasic but were not mounting immune responses. The PCR results were also positive for all individuals who had positive hemoculture, for 37 individuals with negative hemoculture and positive serology, and for two of six individuals with inconclusive serology and negative hemoculture. Thirteen individuals living in nonendemic areas who had negative serology were used as a negative control group: 100% had negative PCR results. Our results show that the optimized PCR protocol used here was very sensitive in detecting the presence of Trypanosoma cruzi in chronic chagasic patients. The PCR and CoML results were well correlated in all of the groups studied, which suggests that our PCR protocol may be effective in the evaluation of cure in patients who receive anti-parasite treatment.

Animals↗
PubMed1998

[Familial eosinophilia: contribution of parasitology to its diagnosis].

It has been observed, at the turn of the century, that members of some families showed a peripheral blood hypereosinophilia. Despite all possible investigations at that time, it was not possible to link it up with a known and well established disease. It was named "family acquired eosinophilia" by Di Guglielmo. nowadays, it has been established that some congenital defects such as the Omenn syndrome and the Wiskott-Aldrich syndrome are associated with hypereosinophilia. Eosinophilia is well known as a sign of allergy, but contaminations with helminths are an important cause of familial hypereosinophilia. In a case of familial distomatosis by Fasciola hepatica, several members of the same family were infected after eating wild cress. An epidemiological study was carried out on 22 families whose several members in a same family had an hypereosinophilia, a parasitosis was serologically diagnosed using such methods as immunoelectrophoresis, Elisa or Western blot. Among these 22 families, 10 had contracted fascioliasis and 4 who had eaten contaminated horse meat contracted trichinosis. For some other families, eosinophilia was not well documented, it concerned cysticercosis for 3 couples after eating meat of raw pork, one family with intestinal distomatosis to F. buski after consumption of aquatic plants and lastly toxocarosis, zoonosis whose contamination is acquired by geophagy but also by eating raw vegetables (salad), fruit (strawberries) and by drinking contaminated water, affected 5 families. In one family, anisakiasis with hypereosinophilia had been contracted by eating raw fish. In another one, trichostrongyloidiasis was contracted by eating raw vegetables from the family garden. The diagnosis is often oriented, for the members of a same family, who are asymptomatic or pauci-symptomatic, by the blood cell count that shows an hypereosinophilia. Furthermore, a collective outbreak of strongyloidiasis epidemic among 115 individuals by oral route is reported, showing that such a way of transmission is possible.

Adolescent↗