Prevalence of Trypanosoma cruzi and Leishmania chagasi infection and risk factors in a Colombian indigenous population

This study was carried out in order to obtain base-line data concerning the epidemiology of American Visceral Leishmaniasis and Chagas’ Disease in an indigenous population with whom the government is starting a dwelling improvement programme. Information was collected from 242 dwellings (1,440 people), by means of house to house interviews about socio-economic and environmental factors associated with Leishmania chagasi and Trypanosoma cruzi transmission risk. A leishmanin skin test was applied to 385 people and 454 blood samples were collected on filter paper in order to detect L. chagasi antibodies by ELISA and IFAT and T. cruzi antibodies by ELISA. T. cruzi seroprevalence was 8.7% by ELISA, L. chagasi was 4.6% and 5.1% by IFAT and ELISA, respectively. ELISA sensitivity and specificity for L. chagasi antibodies were 57% and 97.5% respectively, as compared to the IFAT. Leishmanin skin test positivity was 19%. L. chagasi infection prevalence, being defined as a positive result in the three-immunodiagnostic tests, was 17.1%. Additionally, 2.7% of the population studied was positive to both L. chagasi and T. cruzi, showing a possible cross-reaction. L. chagasi and T. cruzi seropositivity increased with age, while no association with gender was observed. Age (p<0.007), number of inhabitants (p<0.05), floor material (p<0.03) and recognition of vector (p<0.01) were associated with T. cruzi infection, whilst age ( p<0.007) and dwelling improvement (p<0.02) were associated with L. chagasi infection. It is necessary to evaluate the long-term impact of the dwelling improvement programme on these parasitic infections in this community.

Persistent infections in chronic Chagas' disease patients treated with anti-Trypanosoma cruzi nitroderivatives

We used a molecular method and demonstrated that treatment of the chronic human Trypanosoma cruzi infections with nitroderivatives did not lead to parasitological cure. Seventeen treated and 17 untreated chronic Chagas' disease patients, with at least two out of three positive serologic assays for the infection, and 17 control subjects formed the study groups. PCR assays with nested sets of T. cruzi DNA primers monitored the efficacy of treatment. The amplification products were hybridized to their complementary internal sequences. Untreated and treated Chagas' disease patients yielded PCR amplification products with T. cruzi nuclear DNA primers. Competitive PCR was conducted to determine the quantity of parasites in the blood and revealed < 1 to 75 T. cruzi/ml in untreated (means 25.83 ± 26.32) and < 1 to 36 T. cruzi/ml in treated (means 6.45 ± 9.28) Chagas' disease patients. The difference between the means was not statistically significant. These findings reveal a need for precise definition of the role of treatment of chronic Chagas' disease patients with nitrofuran and nitroimidazole compounds.

Trypanosoma cruzi parasitemia observed in immunocompromised patients: the importance of the artificial xenodiagnosis

Trypanosoma cruzi parasitemia observed in immunocompromised patients (transplant or positive HIV) occurred more frequently by the artificial xenodiagnosis method (10/38) compared with hemoculture (2/38), given the same quantity of blood. Other ways of diagnosis, like mice inoculation (5/38), QBC and buffy coat (2/38), were evaluated also. This result showed the importance of the artificial xenodiagnosis. The other techniques increased only one more patient positive.

Blood-sucking lice may disseminate Trypanosoma cruzi infection in baboons

Trypanosoma cruzi (Schyzotrypanum, Chagas, 1909), and Chagas disease are endemic in captive-reared baboons at the Southwest Foundation for Biomedical Research, San Antonio, Texas. We obtained PCR amplification products from DNA extracted from sucking lice collected from the hair and skin of T. cruzi-infected baboons, with specific nested sets of primers for the protozoan kinetoplast DNA, and nuclear DNA. These products were hybridized to their complementary internal sequences. Selected sequences were cloned and sequencing established the presence of T. cruzi nuclear DNA, and minicircle kDNA. Competitive PCR with a kDNA set of primers determined the quantity of approximately 23.9 ± 18.2 T. cruzi per louse. This finding suggests that the louse may be a vector incidentally contributing to the dissemination of T. cruzi infection in the baboon colony.

Oral transmission of Chagas disease: importance of Trypanosoma cruzi biodeme in the intragastric experimental infection

Oral transmission of Trypanosoma cruzi has been suspected when epidemic episodes of acute infection were observed in areas devoid of domiciled insect vectors. Considering that the distribution of T. cruzi biodemes differs in sylvatic and domestic cycles, results of studies on biodemes can be of interest regarding oral transmission. The infectivity of T. cruzi strains of different biodemes was tested in mice subjected to infection by the digestive route (gavage). Swiss mice were infected either with the Peruvian strain (Biodeme Type I, Z2b) or the Colombian strain (Biodeme Type III, Z1, or T. cruzi I); for control, intraperitoneal inoculation was performed in a group of mice. The Colombian strain revealed a similar high infectivity and pathogenicity when either route of infection was used. However, the Peruvian strain showed contrasting levels of infectivity and pathogenicity, being high by intraperitoneal inoculation and low when the gastric route was used. The higher infectivity of the Colombian strain (Biodeme Type III) by gastric inoculation is in keeping with its role in the epidemic episodes of acute Chagas disease registered in the literature, since strains belonging to Biodeme III are most often found in sylvatic hosts.

The epidemiologic profile and prevalence of cardiopathy in Trypanosoma cruzi infected blood donor candidates, Londrina, Paraná, Brazil

To describe the epidemiologic profile and prevalence of cardiopathy in 163 Trypanosoma cruzi serum positive blood donor candidates, a descriptive study was carried out between August, 1996 and November, 1997 at the Londrina State University Chagas Disease Outpatient Clinic. The profile found was: young, average age 42.95 ± 8.62 years; male (65%); Caucasian (84%); low level of schooling; low family income; agricultural worker (26%); born in the state of Paraná (67%); from rural areas (85%); migrated to the city (85%); and the vector as the main mechanism of transmission. During the clinical characterization a chronic cardiac form was found in 38% of the patients and classified as cardiac suggestive form in 21% and little suggestive of Chagas disease in 17%. No significant difference was found among age group distribution, sex and the presence of cardiac symptoms in patients with or without cardiopathy. This study emphasizes the importance of expanding medical services to areas with a greater prevalence of infected individuals, in a hierarchical manner and aiming at decentralization.

Survival of Trypanosoma cruzi in sugar cane used to prepare juice

Chagas disease can be transmitted to man by many different means, including contact with infected triatomine feces, blood transfusion, laboratory accidents, organ transplants, and congenital or oral routes. The latter mode has received considerable attention recently. In this assay, we evaluate the survival of Trypanosoma cruzi contaminating sugar cane used to prepare juice, as well as the viability and capacity for infection by the parasite after recovery. Thirty triatomines were contaminated with T. cruzi Y strain and 45 days later pieces of sugar cane were contaminated with the intestinal contents of the insects. The pieces were ground at different intervals after contamination (time = 0, 1, 4, 6, 12 and 24 hours) and the juice extracted and analyzed. Different methods were used to show T. cruzi in the juice: direct analysis, hematocrit tube centrifugation and QBC, and experimental inoculation in 47 female BALB/c mice (five control mice and seven mice for each interval examined (five inoculated orally and two intraperitoneally). Positive results were found using the direct analysis and QBC methods for juice prepared up to 12 hours after initial contamination. However, by the centrifugation technique, positivity was found only up to four hours after contamination of the sugar cane. Inoculated animals showed parasitemia during a 14 day observation period, demonstrating the high survival rate of T. cruzi in sugar cane.

Methylene blue vital staining for Trypanosoma cruzi trypomastigotes and epimastigotes

The morphological identification of Trypanosoma cruzi is currently considered to have a high specificity, but its sensitivity, which depends on the volume of the sample examined, is rather low. Trypanosome developmental stages suspended in blood, reduviid feces, and culture media are routinely searched for by means of fresh film examination (about 2 µL). High speed centrifugation of blood samples separates the buffy coat, where most trypomastigotes concentrate. As the parasites are transparent and colorless, their detection is mostly dependent on their motility. The fluorescent vital stain acridine orange has been used to enhance image contrast, as exemplified by the QBC (Quantitative Buffy Coat) technique. Staining blood, buffy coat, reduviid feces, and culture media samples with methylene blue (also a vital dye) is a means of producing sharp, well contrasted images of motile or non-motile T. cruzi developmental stages, only standard laboratory microscopes being required. Slides previously coated with a thin layer of methylene blue are used to stain fresh blood films. Photomicrographs exemplify the results of methylene blue staining applied to living and fixed parasites.