The structure of the Phlebotomine sand fly community from the Venezuelan Andes was studied using ... more The structure of the Phlebotomine sand fly community from the Venezuelan Andes was studied using null-model tests. The analyses, at the living zones and altitudes scales, revealed C-scores larger than those expected by random, independently of the collection technique (P < 0.05). These results imply that sand fly species are non-aggregated at both scales. Random results for the variance of C-score and for the favored states hypothesis suggest that sand fly species belong to an unique guild. The latter is reinforced by the fact that anthropophilic and zoophilic species use in the same way a common resource (blood). Finally, we suggest additional approaches to study the role of the sand fly community structure on the genesis and dynamics of transmission of American cutaneous leishmaniasis.
Trypanosoma cruzi congenital transmission in wild bats (Molossus molossus), associated with infec... more Trypanosoma cruzi congenital transmission in wild bats (Molossus molossus), associated with infected Rhodnius prolixus in a natural habitat from a rural locality in western Venezuela, is reported. T. cruzi blood circulating trypomastigotes in a pregnant bat were detected by parasitological methods. Polymerase chain reaction (PCR) assays carried out in samples from the heart and the fetus of the same infected female, revealed the presence of T. cruzi-specific DNA in both of the tissues, demonstrating transmission of the infection from the mother to the offspring. Eighty percent of the captured bats and 100% of the examined fetuses from pregnant specimens were shown to be infected by T. cruzi, indicating that M. molossus is a very susceptible species for this parasite, and that T. cruzi congenital transmission is a common phenomenon in nature. To our knowledge, this seems to be the first report on congenital T. cruzi transmission in wild bats in Venezuela. The circulation of T. cruzi lineage I in the study area was demonstrated by typing the isolates from bats and triatomine bugs captured in the same habitat. The potential epidemiological implication of these findings in areas where Chagas disease is endemic is discussed.
We used the species specificity and repetitious nature of subtelomeric kinetoplastida sequences t... more We used the species specificity and repetitious nature of subtelomeric kinetoplastida sequences to generate a duplex PCR assay for the simultaneous detection of Trypanosoma cruzi and Trypanosoma rangeli in experimentally and naturally infected triatomine (Reduviid) bugs and in infected human subjects. The assay was species specific and was capable of detecting 1/20th of T. cruzi and 1/4th of T. rangeli cell equivalents without complementary hybridization. In addition, the PCR-based assay was robust enough for direct application to difficult biological samples such as Reduviid feces or guts and was capable of recognizing all T. cruzi and T. rangeli strains and lineages. Because the assay primers amplify entirely different target sequences, no reaction interference was observed, facilitating future adaptation of this assay to an automated format.
Inapparent infections of Trypanosoma cruzi were detected in symptomless seropositive people livin... more Inapparent infections of Trypanosoma cruzi were detected in symptomless seropositive people living in close proximity, and under the same conditions of risk, to patients with acute Chagas disease. Similar infections were also detected in sera samples of people from 25 villages of western Venezuela where Chagas disease is endemic. Seropositivity in all the 1,251 studied samples was established by use of 3 serological methods (direct agglutination test, indirect immunofluorescence antibody test, and enzyme-linked immunosorbent assay). Each seropositive sample was tested for detection of anti-T. cruzi-specific immunoglobulin (Ig) M and IgG levels and specific T. cruzi infection by molecular methodology (polymerase chain reaction assay). The combined analysis of the serologic (IgM and IgG levels), molecular (specific T. cruzi DNA), and statistical findings demonstrated the existence of a different stage of T. cruzi infection in asymptomatic patients, which is suggested to be recognized as inapparent infection. Its definition, significance, and comparison with typical Chagas disease phases are presented, and its potential epidemiological importance is discussed.
To make reliable interpretations about evolutionary relationships between Trypanosoma rangeli lin... more To make reliable interpretations about evolutionary relationships between Trypanosoma rangeli lineages and their insect vectors (triatomine bugs of the genus Rhodnius) and, thus, about the determinant factors of lineage segregation within T. rangeli, we compared phylogenies of parasite isolates and vector species. Sixty-one T. rangeli isolates from invertebrate and vertebrate hosts were initially evaluated in terms of polymorphism of the spliced-leader gene (SL). Further analysis based on SL and SSUrRNA sequences from 33 selected isolates, representative of the overall phylogenetic diversity and geographical range of T. rangeli, supported four phylogenetic lineages within this species. By comparing the phylogeny of Rhodnius species with that inferred for T. rangeli isolates and through analysis of the geographical range of the isolates, we showed that there is a very significant overlap in the distribution of Rhodnius species and T. rangeli lineages. Congruence between phylogeographical analysis of both T. rangeli lineages and complexes of Rhodnius species are consistent with the hypothesis of a long coexistence of parasites and their vectors, with lineage divergence associated with sympatric species of Rhodnius apparently without association with particular vertebrate hosts. Separation of T. rangeli isolates from vectors of distinct complexes living in sympatry favours the absence of gene flow between the lineages and suggests evolution of T. rangeli lineages in independent transmission cycles, probably associated to specific Rhodnius spp. ecotopes. A polymerase chain reaction assay based on SL intergenic sequences was developed for simultaneous identification and lineage genotyping of T. rangeli in epidemiological surveys.
... tus and Eratyrus mucronatus and are found in most of the countries in Central and South Ameri... more ... tus and Eratyrus mucronatus and are found in most of the countries in Central and South America (Tejera, 1920; Uribe, 1929;De Leon, 1965;Pañalver ... lewisi divides in the blood stream as well as in the vasa recta of the kidney of rat (Ormerod &. Killick-Kendrick, 1956), producing ...
The morphological sequence of Trypanosoma rangeli development in the body cavity of Rhodnius prol... more The morphological sequence of Trypanosoma rangeli development in the body cavity of Rhodnius prolixus is described. The metacyclic trypanosome is the product of successive division and transformation during the intra and extracellular development in the haemocoele. The significance of the early invasion of T. rangeli into the haemolymph is discussed. The epidemiological importance of the developmental pattern of T. rangeli in the vectors haemolymph and the host-response to the parasite are considered.
The structure of the Phlebotomine sand fly community from the Venezuelan Andes was studied using ... more The structure of the Phlebotomine sand fly community from the Venezuelan Andes was studied using null-model tests. The analyses, at the living zones and altitudes scales, revealed C-scores larger than those expected by random, independently of the collection technique (P < 0.05). These results imply that sand fly species are non-aggregated at both scales. Random results for the variance of C-score and for the favored states hypothesis suggest that sand fly species belong to an unique guild. The latter is reinforced by the fact that anthropophilic and zoophilic species use in the same way a common resource (blood). Finally, we suggest additional approaches to study the role of the sand fly community structure on the genesis and dynamics of transmission of American cutaneous leishmaniasis.
Trypanosoma cruzi congenital transmission in wild bats (Molossus molossus), associated with infec... more Trypanosoma cruzi congenital transmission in wild bats (Molossus molossus), associated with infected Rhodnius prolixus in a natural habitat from a rural locality in western Venezuela, is reported. T. cruzi blood circulating trypomastigotes in a pregnant bat were detected by parasitological methods. Polymerase chain reaction (PCR) assays carried out in samples from the heart and the fetus of the same infected female, revealed the presence of T. cruzi-specific DNA in both of the tissues, demonstrating transmission of the infection from the mother to the offspring. Eighty percent of the captured bats and 100% of the examined fetuses from pregnant specimens were shown to be infected by T. cruzi, indicating that M. molossus is a very susceptible species for this parasite, and that T. cruzi congenital transmission is a common phenomenon in nature. To our knowledge, this seems to be the first report on congenital T. cruzi transmission in wild bats in Venezuela. The circulation of T. cruzi lineage I in the study area was demonstrated by typing the isolates from bats and triatomine bugs captured in the same habitat. The potential epidemiological implication of these findings in areas where Chagas disease is endemic is discussed.
We used the species specificity and repetitious nature of subtelomeric kinetoplastida sequences t... more We used the species specificity and repetitious nature of subtelomeric kinetoplastida sequences to generate a duplex PCR assay for the simultaneous detection of Trypanosoma cruzi and Trypanosoma rangeli in experimentally and naturally infected triatomine (Reduviid) bugs and in infected human subjects. The assay was species specific and was capable of detecting 1/20th of T. cruzi and 1/4th of T. rangeli cell equivalents without complementary hybridization. In addition, the PCR-based assay was robust enough for direct application to difficult biological samples such as Reduviid feces or guts and was capable of recognizing all T. cruzi and T. rangeli strains and lineages. Because the assay primers amplify entirely different target sequences, no reaction interference was observed, facilitating future adaptation of this assay to an automated format.
Inapparent infections of Trypanosoma cruzi were detected in symptomless seropositive people livin... more Inapparent infections of Trypanosoma cruzi were detected in symptomless seropositive people living in close proximity, and under the same conditions of risk, to patients with acute Chagas disease. Similar infections were also detected in sera samples of people from 25 villages of western Venezuela where Chagas disease is endemic. Seropositivity in all the 1,251 studied samples was established by use of 3 serological methods (direct agglutination test, indirect immunofluorescence antibody test, and enzyme-linked immunosorbent assay). Each seropositive sample was tested for detection of anti-T. cruzi-specific immunoglobulin (Ig) M and IgG levels and specific T. cruzi infection by molecular methodology (polymerase chain reaction assay). The combined analysis of the serologic (IgM and IgG levels), molecular (specific T. cruzi DNA), and statistical findings demonstrated the existence of a different stage of T. cruzi infection in asymptomatic patients, which is suggested to be recognized as inapparent infection. Its definition, significance, and comparison with typical Chagas disease phases are presented, and its potential epidemiological importance is discussed.
To make reliable interpretations about evolutionary relationships between Trypanosoma rangeli lin... more To make reliable interpretations about evolutionary relationships between Trypanosoma rangeli lineages and their insect vectors (triatomine bugs of the genus Rhodnius) and, thus, about the determinant factors of lineage segregation within T. rangeli, we compared phylogenies of parasite isolates and vector species. Sixty-one T. rangeli isolates from invertebrate and vertebrate hosts were initially evaluated in terms of polymorphism of the spliced-leader gene (SL). Further analysis based on SL and SSUrRNA sequences from 33 selected isolates, representative of the overall phylogenetic diversity and geographical range of T. rangeli, supported four phylogenetic lineages within this species. By comparing the phylogeny of Rhodnius species with that inferred for T. rangeli isolates and through analysis of the geographical range of the isolates, we showed that there is a very significant overlap in the distribution of Rhodnius species and T. rangeli lineages. Congruence between phylogeographical analysis of both T. rangeli lineages and complexes of Rhodnius species are consistent with the hypothesis of a long coexistence of parasites and their vectors, with lineage divergence associated with sympatric species of Rhodnius apparently without association with particular vertebrate hosts. Separation of T. rangeli isolates from vectors of distinct complexes living in sympatry favours the absence of gene flow between the lineages and suggests evolution of T. rangeli lineages in independent transmission cycles, probably associated to specific Rhodnius spp. ecotopes. A polymerase chain reaction assay based on SL intergenic sequences was developed for simultaneous identification and lineage genotyping of T. rangeli in epidemiological surveys.
... tus and Eratyrus mucronatus and are found in most of the countries in Central and South Ameri... more ... tus and Eratyrus mucronatus and are found in most of the countries in Central and South America (Tejera, 1920; Uribe, 1929;De Leon, 1965;Pañalver ... lewisi divides in the blood stream as well as in the vasa recta of the kidney of rat (Ormerod &. Killick-Kendrick, 1956), producing ...
The morphological sequence of Trypanosoma rangeli development in the body cavity of Rhodnius prol... more The morphological sequence of Trypanosoma rangeli development in the body cavity of Rhodnius prolixus is described. The metacyclic trypanosome is the product of successive division and transformation during the intra and extracellular development in the haemocoele. The significance of the early invasion of T. rangeli into the haemolymph is discussed. The epidemiological importance of the developmental pattern of T. rangeli in the vectors haemolymph and the host-response to the parasite are considered.
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