Determinación del grado de infestación e infección de vectores de la enfermedad de Chagas en la comunidad de Huayhuasi (Mecapaca) / Determination of the degree of infestation and infection of vectors of Chagas disease in the community of Huayhuasi (Mecapaca)

Los trabajos realizados de trampeo y captura de triatominos (que son los insectos vectores de la enfermedad de Chagas) en zonas silvestres de los alrededores de la localidad de Huayhuasi, municipio de Mecapaca en el departamento de La Paz. Se colocaron 50 trampas en lugares estratégicos escogidos de acuerdo a las características del área de estudio. De las 50 trampas, en 9 trampas se lograron atrapar a los triatominos, lo que representa el 4.5% de infestación de la zona de estudio. Se capturaron a 13 insectos (7 ninfas de diferentes estadíos y 6 adultos). Las características morfológicas de los insectos fueron las típicas del Triatoma infestans. En el examen en fresco de las deyecciones de los 6 especímenes adultos capturados, en 4 de ellos se detectó presencia del parásito Trypanosoma cruzi, lo cual demuestra un 67% de infección, porcentaje bastante significativo en consideración a la cercanía de estos lugares infestados a las zonas urbanas del municipio de Mecapaca. Los parásitos que los especímenes portaban, fueron aislados y cultivados en medio de cultivo LIT (Liver Infusion Tryptose) suplementado con 10% de suero bovino fetal e incubados en estufa a 26°C. El análisis del ADN extraído de los parásitos, ha revelado la DTU (Discrete Typing Unit) correspondiente al linaje TcI.

Trapping and capture of triatomines (which are the insect's vectors of Chagas' disease) were carried out in wild areas around the town of Huayhuasi, municipality of Mecapaca, in the department of La Paz. 50 traps were placed in strategic places chosen according to the characteristics already established. Of the 50 traps, nine traps managed to trap the triatomines, representing 4.5% of infestation in the study area. 13 insects (7 nymphs of different stages and 6 adults) were captured. The morphological characteristics of the insects were typical of Triatoma infestans. In the fresh examination of the excrement of the six captured adult specimens, in 4 of them the presence of the parasite Trypanosoma cruzi was detected, which shows a 67% infection, a very significant percentage considering the proximity of these infested places to the Urban areas of the municipality of Mecapaca. The parasites that the specimens carried were isolated and cultured in LIT (Liver Infusion Triptose) medium supplemented with 10% fetal bovine serum and incubated in an oven at 26 °C. Analysis of the DNA extracted from the parasites has revealed the DTU corresponding to the Tc I lineage.

Trypanosoma cruzi: impact of clonal evolution of the parasite on its biological and medical properties.

Trypanosoma cruzi populations are subdivided into natural clones that can exhibit considerable genetic differences. It has been proposed that T. cruzi clonal structure has a major impact on this parasite's biological properties. The present work aims at testing this hypothesis. Twenty-one stocks isolated from various ecological cycles, places, and hosts were characterized by multilocus enzyme electrophoresis (MLEE) with 22 genetic loci and random amplification of polymorphic DNA (RAPD) with 10 primers on the one hand and by 14 different biological parameters on the other hand. These parameters were related to: (i) growth kinetics of epimastigotes and amastigotes; (ii) infection of culture cells by amastigotes; (iii) viability of extracellular trypomastigotes; or (iv) sensitivity of epimastigotes, trypomastigotes, and amastigotes to Benznidazole and Nifurtimox. MLEE and RAPD results exhibited parity to each other, as previously noted (M. Tibayrenc, K. Neubauer, C. Barnabé, F. Guerrini, D. Skarecky, and F. J. Ayala, 1993, Proceedings of the National Academy of Sciences of the USA 90, 1335-1339), and showed that the 21 stocks were distributed into three main genetic groups, 19/20, 32, and 39, corresponding to the major clones 19, 20, 32, and 39 previously described on the basis of 15 isozyme loci. Most biological parameters showed a strong correlation to the genetic distances evaluated from either MLEE or RAPD, which favors the working hypothesis. The only exception came from drug sensitivity estimated on trypomastigote forms. The overall results made it possible to firmly reject the null hypothesis that there is no relationships between evolutionary distances and biological differences in T. cruzi natural clones.

Isoenzyme characterization of Leishmania braziliensis braziliensis isolates obtained from Bolivian and Peruvian patients.

Thirty-four Leishmania isolates obtained from Bolivian and Peruvian patients infected with mucocutaneous leishmaniasis were characterized by isoenzyme electrophoresis using 10 enzymatic markers; all belonged to the subspecies L.b. braziliensis. Three isolates showed marked variation compared with the reference strain with respect to 5 or 6 enzymes. These variant isolates originated from patients with forms of the disease which were unresponsive to treatment.

Direct identification of Trypanosoma cruzi natural clones in vectors and mammalian hosts by polymerase chain reaction amplification.

The polymerase chain reaction was used to amplify the highly variable region of the kinetoplast minicircle of Trypanosoma cruzi directly in biological samples (feces of infected Triatomine bugs, blood samples of experimentally infected mice, and artificially infected human blood samples). Hybridization of the amplified DNAs with reference stocks representing different genotypes (natural clones) enabled us to characterize the stocks infecting the biological samples under study. The main interest of this new approach is the diagnosis of T. cruzi infection and simultaneous direct identification of the different natural clones circulating in vectors and mammalian blood without isolation of the stocks. The suitability of this technique for epidemiologic studies is also discussed.

[A new case of autochthonous visceral leishmaniasis in Bolivia]. / Nouveau cas autochtone de leishmaniose viscérale en Bolivie.

A sixth autochthonous case of visceral leishmaniasis is reported in Bolivia. It is also the fourth case detected in the Yungas Valley (Department of La Paz) confirming the long-term existence of the disease in this area where cases of canine leishmaniasis and natural infestation of the phlebotomine sandfly, Lutzomyia longipalpis, were previously reported.

Parasitological diagnosis of mucocutaneous leishmaniasis due to Leishmania b. braziliensis in Bolivia.

Parasitological diagnosis, using stained smears, culture and pathological examination of biopsy, was studied in 146 patients infected with mucocutaneous leishmaniasis, in Bolivia and Peru. The most efficient parasite detecting technique appeared to be the smear examination in cutaneous lesions (33% positive) and the pathology in case of mucous lesions (28% positive). In both, cutaneous and mucous lesions, the parasites were found most frequently in old lesions.

Prevalence of Trypanosoma cruzi infection in blood banks of seven departments of Bolivia.

Trypanosoma cruzi infection was studied in 1,298 sera samples of blood banks from 7 capital departments of Bolivia, using the immunofluorescence test (IFI) and Enzyme Linked Immunosorbent Assay (ELISA). The percentages of positivity in these 7 departments have an average of 28% and are distributed as follows: Sta. Cruz 51%, Tarija 45%, Cochabamba 28%, Sucre 39%, La Paz 4.9%, Oruro 6% and Potosi 24%. The prevalence is related with the altitude levels of the different departments. However in Potosi (3,945 m) we found a 24% of prevalence, probably due to the proximity of endemic valleys to the city. The authors suggest a strict control in blood donors since there exists a great risk of infection.

Chagas' disease in Bolivia: clinical and epidemiological features and zymodeme variability of Trypanosoma cruzi strains isolated from patients.

We performed serological and pathological studies on 495 patients with Chagas' disease from different areas of Bolivia. Eighty-nine Trypanosoma cruzi strains, isolated by xenodiagnosis, were characterized by 12 isoenzyme loci and were related to the presence of cardiac changes and enteric disease with megacolon. There was a high heterogeneity of human zymodemes, presenting evidence of 2 predominant zymodemes genetically dissimilar from each other and ubiquitous in Bolivia. The frequencies of these predominant zymodemes among strains from patients were compared to strains from triatomine bugs previously studied. We observed mixtures of different zymodemes within the same patient, a phenomenon seen previously in Bolivian patients. There was no apparent difference of pathogenicity between the 2 more frequent zymodemes isolated from humans.