Susceptibility and resistance to deltamethrin of wild and domestic populations of Triatoma infestans (Reduviidae: Triatominae) in Bolivia: new discoveries

Bolivia is a high-endemic country for Chagas disease, for which the principal vector is Triatoma infestans (Triatominae). This is a mainly domestic species that is also found in the wild environment. Recently, an increasing number of studies have shown the importance of Triatominae resistance to insecticides, especially in Bolivia. Data regarding the susceptibility/resistance of wild and domestic populations of T. infestans to deltamethrin are presented. For the first time, domestic populations of the department of Santa Cruz were tested, showing low resistance. Although most of the wild populations were found to be susceptible to deltamethrin, three populations from three departments showed a mortality rate of less than 100%. This result is emphasised here.

Conocimiento epidemiológico y situación actual de la enfermedad de Chagas en el estado de Jalisco, México / Epidemiologic knowledge and current situation of Chagas disease in the state of Jalisco, Mexico

La enfermedad de Chagas en el estado de Jalisco, México, apareció por primera vez en 1967, aunque su conocimiento ha seguido un proceso lento. Entre los años de 1967 y 2006 se describió la enfermedad en sus formas agudas y crónicas; se identificaron las especies de vectores y se aisló el parásito Trypanosoma cruzi, que luego se caracterizó en el plano genético. La magnitud de la infección en el hombre se determinó con estudios serológicos en diversas poblaciones, así como en donadores de sangre. En la actualización presente del conocimiento de la enfermedad en el estado de Jalisco se mostró la necesidad de incrementar las investigaciones sobre la epidemiología de la enfermedad de Chagas, así como los estudios clínicos para determinar la salud de los individuos y las poblaciones.

Chagas disease in the state of Jalisco, Mexico was described for the first time in 1967; however, knowledge on the disease remains in a slow process. Between 1967 and 2006, the disease was described in its acute and chronic forms. The vector species have been identified, and the parasite Trypanosoma cruzi has been isolated and genetically characterized. Also, the magnitude of the infection in humans has been determined through serological studies of different populations as well as of blood donors. The up-to-dateness of knowledge of the disease in the state of Jalisco, unveils a necessity of increased research on the epidemiology of Chagas disease as well as on clinical studies to assess the health of individuals and the populations.

Preliminary results of random amplification of polymorphic DNA among Triatominae of the phyllosoma complex (Hemiptera, Reduviidae)

In Mexico, Triatoma longipennis (Usinger), Triatoma picturata (Usinger), and Triatoma pallidipennis (Stal), primary Chagas disease vector species of the phyllosoma complex, were analyzed by randomly amplified polymorphic DNA (RAPD). Sixteen decametric primers resolved individual profiles not identical, but partially discriminative between species. Analysis based on pairwise presence/absence comparisons between the three species was performed using three primers and two outgroup species Triatoma infestans (Klug) and Triatoma barberi (Usinger). Fifty-three bands in total were scored, although only two bands were constant among the three phyllosoma complex species. Two other bands were constant only for T. longipennis and T. picturata together, and not present in T. pallidipennis. Neighbor Joining tree and the multiple correspondence analysis discriminated T. pallidipennis clearly from the other two species, although there was overlap between T. longipennis and T. picturata. The results indicate a close relationship between the studied species and support the hypothesis of their recent evolution. The suitability of RAPD to discern populations within the species is discussed.

Isoenzyme profiles of Trypanosoma cruzi stocks from different areas of Paraguay

Twenty one Trypanosoma cruzi stocks from humans, domiciliary triatomines and one sylvatic animal of different areas of Paraguay were subjected to isoenzyme analysis. Thirteen enzyme systems (15 loci in total) were studied. MN cl2 (clonets 39) and SO34 cl4 (clonets 20) were used as references. Relationships between stocks were depicted by an UPGMA dendrogram constructed using the JaccardÝs distances matrix. Among the Paraguayan stocks 14 zymodemes were identified (Par1 to Par14), Par 5 being the most frequent. Polymorphism rate and clonal diversity were 0.73 and 0.93, respectively. Average number of alleles per polymorphic locus was 2.5 (range 2-4). These measurements show a high diversity, which is confirmed by the dendrogram topology. All stocks belong to the same lineage, as MN cl2 reference strain (T. cruzi II). Moreover three distinct subgroups were identified and two of them correspond to Brazilian and Bolivian zymodemes, respectively. The third subgroup, the most common in Paraguay, is related to Tulahuen stock. The large geographical distribution of some zymodemes agrees with the hypothesis of clonality for T. cruzi populations. However sample size was not adequate to detect genetic recombination in any single locality

Selection of Trypanosoma cruzi clonal genotypes (clonet 20 and 39) isolated from Bolivian triatomines following subculture in liquid medium

Previous studies showed that two groups of Trypanosoma cruzi clonal genotypes named clonet 20 and clonet 39 were predominant in Triatoma infestans, the unique vector of Chagas disease in Bolivia. These groups of clones correspond to distinct genetic clusters. These clonets were detected in T. infestans and Rhodnius pictipes fecal samples before isolation and after culture by kDNA PCR (polymerase chain rreaction) and hybridization of the amplified products with clonet specific kDNA probes named 20 and 39 as previously reported. Forty eight T. infestans and three R. pictipes infected insects captured at random in different Bolivian departments were proceeded. As previously reported the direct identification of the two major clonets in fecal samples allowed the detection of abundant mixed infections: 41 percent in the original sample, however after culture, only 6 percent of mixed infections were detected. Among the 21 parasite stocks isolated from digestive tracts where mixed infections were initially detected (clonet 20 + 39) clonet 20 alone was detected in 81 percent of them. This result clearly showed that the culture step selected clonet 20 parasites over those belonging to clonet 39. The taxonomic status of the isolated stocks was also confirmed by isoenzyme typing, and correlation was observed between clustering topology and hybridization patterns with the probes 20 and 39.

Mexican Trypanosoma cruzi stocks: analysis of minicircle kDNA homologies by cross-hybridization

Homologies of minicircle kDNA of 27 Mexican stocks were studied by cross-hybridization with four kDNA probes derived from three reference stocks belonging to groups Trypanosoma cruzi I (SO34 cl4 and Silvio) and T. cruzi II (MN) and one Mexican stock. High homologies were only observed with Silvio (six stocks) and Mexican probes (11 stocks). After 30 min exposure (low homology) additional stocks were recognized with SO34 cl4 (three stocks) and Silvio (six stocks) probes; with the Mexican probe only five stocks remained non-reactive. All the stocks were typed by isoenzyme (16 loci) and Mexican stocks belonged to T. cruzi I. Hybridization patterns were not strictly correlated with the observed clustering and cross-hybridization of kDNA minicircles is not available to distinct Mexican stocks.

Caracterizacion Isoenzimatica de cepas de Trypanosoma Cruzi / Isoenzyme characterization of Trypanosoma Cruzi Strains / Annual Reports 1997

En este trabajo, 21 cepas de T. Cruzi aisladas de humanos , triatominos y mamíferos de losd Dptos de Pte. Hayes, Paraguarí, San Pedro, Caaguazú y Central, fueron sometidos al análisis isoenzimático. Se estudiaro 13 sistemas enzimáticos (15 loci en total) y como cepas de referencia se emplearon las cepas MN y SO34. Se encontraron 14 zimodemas (Z) diferentes, coincidieron con estdios previos de caracterización de cepas paraguayas de T. cruzi. No hubo asociación directa entre el tipo de zimodema y la procedencia. El caracter ubicuo mostrado por los zimodemas Z1 y Z5 en este estudio, apoya el criterio de clonalidad mencionado por otros autores

Immune response to Trypanosoma cruzi shed acute phase antigen in children from an endemic area for Chagas' disease in Bolivia

A field study of the immune response to the shed acute phase antigen (SAPA) of Trypanosoma cruzi was carried out in the locality of Mizque, Cochabamba department, Bolivia. Schoolchildren (266), with an average of 8.6ñ3.6 years, were surveyed for parasitological and serological diagnosis, as well as antibodies directed against SAPA using the corresponding recombinant protein in ELISA. The antibodies against SAPA were shown in 82 per cent of patients presenting positive serological diagnosis (IgG specific antibodies). The positive and negative predictive values were 0.88. Antibodies anti-SAPA were shown in 80.8 per cent of the chagasic patients in the initial stage of the infection (positive IgM serology and/or positive buffy coat (BC) test) and in 81.4 per cent of the patients in the indeterminate stage of the infection (positive IgG serology with negative BC and IgM tests). These results show that the anti-SAPA response is not only present during the initial stage of the infection (few months) but extends some years after infection.

Genetic variability and microdistribution of Triatoma infestans genotypes and Trypanosoma cruzi clones in Arequipa region (Peru)

Genetic varibility of Triatoma infestans and Trypanosoma cruzi populations was studied by isoenzyme analysis in two distinct areas of Arequipa province (Peru); one, Santa Rita de Siguas, being an endemic area for Chagas' disease, the second Arequipa, recently infected. Analysis of T. infestans genetic variability indicates, (i) temporal stability of genotypes found in Santa Rita de Siguas, (ii) high genetic differences between Arequipa and Santa Rita de Siguas populations suggesting minor contact between them, (iii) multiple origin of the T. infestans population in Arequipa, and (iv) poor dispersal capacity of T. infestans: the panmictic unit could be reduce to a house. Parasite isoenzyme analysis was performed in 29 Peruvian stocks of T. cruzi, mainly isolated from bugs taken in a single locality, Santa Rita de Siguas. The results show, (i) a high genetic polymorphism, (ii) nine different multilocus genotypes were detected and clustered in two different clades, (iii) most of the parasite isolates pertained to one of the clade and were genetically similar to those analyzed 12 years before. This sample allowed the study of the mating system of T. cruzi in strict sympatic conditions and gave more strength to the hypothesis of the clonal structure of T. cruzi populations.

Trypanosoma cruzi: expression of antigenic component 5 among 35 laboratory clones obtained from 18 different isozymic variants

Dois anticorpos monoclonais anticomponente 5 de Trypanosoma cruzi (I-35/115 e II-190/30) foram testados respectivamente em IFA e ELISA sobre 35 clones de T.cruzi isolados no laboratório. Entre estes 35 clones testados, 18 perfís isoenzimícos diferentes puderam ser detectados. Todos os clones foram reconhecidos exceto um clone que näo reagiu com o anticorpo monoclonal II-190/30. Estes resultados säo a favor da expressäo constante do componente 5 no meio do taxón T. cruzi

Specific humoral depression in chronic patients infected by Trypanosoma cruzi.

Realizamos um estudo comparativo entre o xenodiagnostico e os testes sorologicos para doenca de Chagas. Cento e cincoenta pacientes de algumas areas endemicas foram estudados. Quatro deles pareceram revelar um estado particular com um xenodiagnostico positivo e uma sorologia negativa, esta realizada com quatro diferentes tecnicas classicas (teste de inmunofluorescencia, ELISA: Enzyme Linked Immunosorbent Assay, teste de fixacao do complemento e teste de immuno-eletroforese). O soro de um dos pacientes que apresentou depressao humoral especifica mostra elevada quantidade de antigenos circulantes comprovada pela tecnica da immuno-eletroforese.Os autores sugerem o uso de um teste sorologico para detectar a presenca de antigenos circulantes de T. cruzi, alem da utilizacao de testes sorologicos classicos. Isto permitiria o diagnostico da doenca de Chagas em pacientes com uma baixa (ou mesmo inexistente) producao de anticorpos especificos