Triatominae (Hemiptera, Reduviidae) in the Pantanal region: association with Trypanosoma cruzi, different habitats and vertebrate hosts

ABSTRACTINTRODUCTION: The transmission cycle of Trypanosoma cruzi in the Brazilian Pantanal region has been studied during the last decade. Although considerable knowledge is available regarding the mammalian hosts infected by T. cruzi in this wetland, no studies have investigated its vectors in this region. This study aimed to investigate the presence of sylvatic triatomine species in different habitats of the Brazilian Pantanal region and to correlate their presence with the occurrences of vertebrate hosts and T. cruzi infection.METHODS: The fieldwork involved passive search by using light traps and Noireau traps and active search by visual inspection. The light traps were placed at five selected points along forested areas for seven nights during each of the nine excursions. At each point where a light trap was set, eight Noireau traps were placed in palm trees and bromeliads.RESULTS: In all, 88 triatomine bugs were collected: two and one individuals from light traps and Noireau traps, respectively; three from peridomestic areas; 23 in coati nests; and 59 in thornbird nests. In this study, active search in microhabitats showed higher efficiency than passive search, since 95% of the triatomine bugs were caught in nests. Further, triatomine bugs were only found to be infected by T. cruzi in coati nests.CONCLUSIONS: Coati nests might act as a point of convergence and dispersion for triatomine bugs and mammal hosts infected by T. cruzi, thereby playing an important role in the sylvatic cycle of T. cruziin the Pantanal region.

Cloning and Characterization of a Schistosoma mansoni cDNA Clone with a Specific Antigenic Expression during Development in a Vertebrate Host

Approximately 2.0 x 10 cDNA clones of an Schistosoma mansoni lgt11 cDNA library were screened in duplicate with serum from infected mice corresponding to distinct phases of infection. A cDNA clone (7/1) was isolated and recognized only by seven week serum. The clone was subcloned in pGEX-2T and Western-blot studies showed a specific antigenic expression confirming that only serum from the chronic phase is capable of recognizing this antigen. Dot-hybridization with RNA from different developmental phases of the parasite showed that the corresponding 7/1 RNA is expressed in all phases of parasite development in vertebrate hosts

Influence of temperature on development of Schistosoma mansoni female cercariae in Biomphalaria glabrata

In these experiments the ratio of male to female S. mansoni larvae in D. glabrata from Belo Horizonte and Ribeirão das Neves Minas Gerais, Brazil, either reared in laboratoty or collected in the field, varied from 1:1 to 1:1.3 or 1.4:1. Cercariae of LE strain of Schistosoma mansoni, shed by 39 snails maintained at 25±0.5ºC were used to infect mice on a weekly basis. Subsequent perfusion resulted in 76.6% male and 23.4% female worms. The cercariac produced by 32 infected snails maintained at 27+0.5°C were inoculated into mice and produced 43.4% male and 56.6% female worms (p<0.05). Cercariae eliminated by snails collected in Barreiro and Ressaca, Belo Horizonte, during hot months, produced 45.7 to 47.7% male and 52.3 to 54.3% female worms. A lower number of cercariae shed by snails collected in Gorduras, Belo Horizonte, at 20+3.0°C, produced 51.6% male and 48.4% female worms. Thus, in this region the infection of vertebrate hosts with S. mansoni cercariae would be more severe in the summer due to the higher level of parasites and the number of eggs.

Amastigotes forms of Trypanosoma cruzi detected in a renal allograft

Trypanosoma cruzi, the causative agent of Chagas’disease assumes two distinct forms in vertebrate hosts: circulating trypomastigote and tissular amastigote. This latter form infects predominantly the myocardium, smooth and skeletal muscle, and central nervous system. The present work describes for the first time the detection of amastigote forms of T. cruzi in the renal parenchyma of a kidney graft recipient one month after transplantation. The patient was serologically negative for Chagas’disease and received no blood transfusion prior to transplant. The cadaver donor was from an endemic area for Chagas’disease. The recipient developed the acute form of the disease with detection of amastigote forms of T. cruzi in the renal allograft biopsy and circulating trypomastigote forms. The present report demonstrates that T. cruzi can infect the renal parenchyma. This mode of transmission warrants in endemic areas of Chagas’disease

UNA virus: first report of human infection in Argentina

Una virus (UNAV), Togaviridae family, is widely distributed in South America, where infections have been detected in mosquitoes and vertebrate hosts (humans, birds and horses). We analyzed human sera from Córdoba inhabitants aged 44 to 89 years and using a neutralization test, we found a prevalence of UNAV antibodies of 3.8% (3/79). The low titers detected suggest past infections probably acquired in rural areas of the Province of Córdoba (central Argentina). None sera were found positive for MAYV neutralizing antibodies. This is the first report of human infections by UNAV in Argentina.

Detection of Trypanosoma cruzi and Trypanosoma rangeli infection in triatomine vectors by amplification of the histone H2A/SIRE and the sno-RNA-C11 genes

Trypanosoma rangeli is non pathogenic for humans but of important medical and epidemiological interest because it shares vertebrate hosts, insect vectors, reservoirs and geographic areas with T. cruzi, the etiological agent of Chagas disease. Therefore, in this work, we set up two PCR reactions, TcH2AF/R and TrFR2, to distinguish T. cruzi from T. rangeli in mixed infections of vectors based on amplification of the histone H2A/SIRE and the small nucleolar RNA Cl1 genes, respectively. Both PCRs were able to appropriately detect all T. cruzi or T. rangeli experimentally infected-triatomines, as well as the S35/S36 PCR which amplifies the variable region of minicircle kDNA of T. cruzi. In mixed infections, whereas T. cruzi DNA was amplified in 100% of samples with TcH2AF/R and S35/S36 PCRs, T. rangeli was detected in 71% with TrF/R2 and in 6% with S35/S36. In a group of Rhodnius colombiensis collected from Coyaima (Colombia), T. cruzi was identified in 100% with both PCRs and T. rangeli in 14% with TrF/R2 and 10% with S35/S36 PCR. These results show that TcH2AF/R and TrF/R2 PCRs which are capable of recognizing all T. cruzi and T. rangeli strains and lineages could be useful for diagnosis as well as for epidemiological field studies of T. cruzi and T. rangeli vector infections.

Susceptibility and morbidity between male and female Swiss mice infected with Angiostrongylus costaricensis: Susceptibilidade e morbidade entre camundongos Swiss machos e fêmeas infectados com Angiostrongylus costaricensis

The gender of vertebrate hosts may affect the outcome of parasitic infections. An experimental murine infection with Angiostrongylus costaricensis was followed with determinations of body weight, fecal larval elimination, number and length of adult worms, number of macroscopic intestinal lesions, and mortality. Groups of male and female Swiss mice were infected with 10 3rd-stage A. costaricensis larvae per animal. The results indicate there are no significant differences related to gender of the host, except for higher length of worms developed in male mice.

Biodemes and zymodemes of Trypanosoma cruzi strains: correlations with clinical data and experimental pathology

With the objective of establishing biological and biochemical characteristics of a significant number of Trypanosoma cruzi strains from different geographical areas, 138 strains isolated from naturally infected humans, triatomine or vertebrate hosts were studied; 120 were isolated from different areas of Brazil and 18 from other South and Central American countries. Inocula from triatomine or culture forms were injected into suckling Swiss mice, followed by passages into mice 10 to 12 g. Biological characters and histopathological study permitted the inclusion of the strains into three Types or biodemes: I, II, III. Isoenzymic analysis confirmed a correspondence between the biodemes and zymodemes : Type I and Z2b, Type II and Z2, Type III and Z1. Results showed the ubiquitary distribution of the several types of strains. The predominance of the same Type and zymodeme in one geographical area was confirmed : Type II strains among the human cases from eastern Bahia and east of Goiás; Type III strains from humans of north Brazil and Central America and from silvatic vectors or vertebrates from other geographical areas. The biological types of strains correlate with different histopathological lesions considering cardiac involvement and neuronal lesions. These findings suggest that the biological behavior together with isoenzymes patterns and pathological pictures in the vertebrate host can be an important tool for establishing correlations between strains behavior and clinico-pathological manifestations of Chagas' disease in different geographical areas.

Seroepidemiological monitoring in sentinel animals and vectors as part of arbovirus surveillance in the state of Mato Grosso do Sul, Brazil

INTRODUCTION: From February-September 2010, seroepidemiological surveys were conducted on non-human primates and transmitter vector capture was used to investigate the possible circulation of arboviruses in the municipalities of Bonito, Campo Grande, and Jardim, State of Mato Grosso do Sul, Brazil. METHODS: A total of 65 primates from the wild and captivity were used, and potential vectors were captured using Castro and dip nets. Serum samples were tested at the Instituto Evandro Chagas, State of Pará, using the hemagglutination inhibition test to detect total antibodies against 19 different arboviruses. Virus isolation was attempted from serum samples and arthropod suspensions using newborn mice and the C6/36 cell line clone. In addition, identification of the vector species was conducted. RESULTS: From the 19 serum samples from Campo Grande, 1 sample had a 1:20 titer for Flavivirus. From the 35 samples collected in Bonito, 17 samples had antibodies to arboviruses, 4 (11.4%) were positive for Alphavirus, and 5 (14.2%) were positive for Flavivirus. Monotypic reactions were observed for the Mayaro (n = 10) and Oropouche (n = 5) viruses, and 6 (17.1%) samples had titers for >1 virus. We captured 120 Culicidae individuals that were potential arbovirus transmitters in Jardim; however, all the samples were negative for the viruses. CONCLUSIONS: Mato Grosso do Sul has a variety of vertebrate hosts and transmission vectors, thereby providing ideal conditions for the emergence or reemergence of arboviruses, including some pathogenic to human beings.

Immunological aspects of host-schistosome relationships

The complex immunological relationships between schistosomes and their vertebrate hosts are considered to be conveniently divisible into four distinct, though interrelated categories: the parasite's vulnerability to, its evasion of, and its exploitation of the host's immune response, and its stimulation of the host's immune response to produce immunopathology. Some significant recent advances in the first three categories are discussed, as well as their relationships to the fourth category of immunopathology.

An Investigation on the Ecology of Triatoma vitticeps (Stal, 1859) and its Possible Role in the Transmission of Trypanosoma cruzi, in the Locality of Triunfo, Santa Maria Madalena Municipal District, State of Rio de Janeiro, Brazil

From January 1989 to April 1995, 465 specimens of Triatoma vitticeps were collected in the locality of Triunfo, 2nd District of Santa Maria Madalena municipal district, State of Rio de Janeiro. The bugs were found indoors by local residents with predominance of adults. The flight activity was high in hot months when the incidence in the domicile also increased. Two hundred and two bugs (111 alive and 91 dead) were examined for Trypanosoma cruzi infection. This was detected in 31 of the dead bugs (34%) and 88 (79%) of the live bugs examined. With a view to investigate the possible vertebrate hosts of the T. cruzi isolates, the blood of 122 mammals was examined through Giemsa-stained smears, hemocultures and xenodiagnosis. T. cruzi was detected in three specimens of Didelphis marsupialis and T. (M.) theileri was detected in one specimen of Bos taurus. The parasites were isolated from triatomine feces, xenoculture and hemoculture. No evidence of human infection was detected in 58 inhabitants examined, as evaluated by indirect imunofluorescence technique using T. cruzi epimastigotes as antigens. These results show that T. vitticeps is still a sylvatic species although nymphs have been found inside the domicile. Thus, an epidemiological vigilance is necessary to know the behaviour of this species following the continuous modifications promoted by the presence of man.

Genetic markers between Biomphalaria glabrata snails susceptible and resistant to Schistosoma mansoni infection

The analysis of the genetic variability related to susceptibility to Schistosoma mansoni infection in the vector of the genus Biomphalaria is important in terms of a better understanding of the epidemiology of schistosomiasis itself, the possible pathological implications of this interaction in vertebrate hosts, and the formulation of new strategies and approaches for disease control. In the present study, the genetic variability of B. glabrata strains found to be resistant or susceptible to S. mansoni infection was investigated using DNA amplification by random amplified polymorphic DNA-polymerase chain reaction (RAPD-PCR). The amplification products were analyzed on 8% polyacrylamide gel and stained with silver. We selected 10 primers, since they have previously been useful to detect polymorphism among B. glabrata and/or B. tenagophila. The results showed polymorphisms with 5 primers. Polymorphic bands observed only in the susceptible strain. The RAPD-PCR methodology represents an adequate approach for the analysis of genetic polymorphisms. The understanding of the genetic polymorphisms associated to resistance may contribute to the future identification of genomic sequences related to the resistance/susceptibility of Biomphalaria to the larval forms of S. mansoni and to the development of new strategies for the control of schistosomiasis.

Trypanosoma (Herpetosoma) rangeli Tejera, 1920: an updated review

Trypanosoma rangeli, a parasite generally considered non-pathogenic for man, is the second species of human trypanosome to be reported from the New World. The geographical distribution of T. rangeli often overlaps with that of T. cruzi, the same vertebrate and invertebrate hosts being infected. Their differentiation thus becomes of real, practical importance, particularly as they share approximately half the antigenic determinants recognized by the humoral response. Little is known about the life cycle of T. rangeli in the vertebrate host, although thousands of human and wild animal infections have been reported. Recent studies have revealed 2 major phylogenetic lineages in T. rangeli having different characteristics, thus leading to better understanding of the epidemiology and interactions with this parasite's vertebrate hosts and triatomine vectors. Based on further genetic characterization analysis, the authors have proposed 2 alternative hypotheses and consider that T. rangeli could have had clonal evolution or have been subjected to speciation processes.