Epidemiology of Chagas disease in Jaguaruana, Ceará, Brazil. I. Presence of triatomines and index of Trypanosoma cruzi infection in four localities of a rural area

In order to assay the triatomine infestation and domiciliation in the rural area of Jaguaruana district, state of Ceará, Brazil, we studied, from November 2000 to April 2002, 4 localities comprising 158 domiciles as a whole, with an average of 4 inhabitants/house, who are dwelling in there for more than 7 years. Most houses have tile-covered roofs and the walls built with plaster-covered bricks (57%), followed by bricks without plaster (33%), and mud walls (7.5%). A total of 3082 triatomines were captured from different locations, according to the following capture plan: (a). intradomiciles: 238 Triatoma brasiliensis, 6 T. pseudomaculata, 9 Rhodnius nasutus, and 2 Panstrongylus lutzi; (b). peridomiciles (annexes): 2069 T. brasiliensis, 223 T. pseudomaculata, 121 R. nasutus, and 1 P. lutzi; (c). wild, in carnauba palms (Copernicia prunifera): 413 R. nasutus. From the captured triatomines, 1773 (57.5%) were examined. The natural index of Trypanosoma cruzi infection ranged from 10.8% to 30.2% (average of 17%), depending on the species and the location from where the triatomines were captured.     

Indicators of infestation, colonization and infection of Triatoma dimidiata (Latreille) (Hemiptera: Reduviidae) in Campeche, México

Triatoma dimidiata (Latreille) is considered to be one of the primary vectors of Chagas disease in Southern Mexico and Central America. The objective of the present study was to obtain ecological information on T. dimidiata in two rural communities of Campeche, Mexico, where the vector is poorly studied. Our work consisted of monthly samplings carried out during one-year time at three levels: sylvatic, peridomestic and intradomestic, in order to estimate the population abundance of this species and its rate of infection with Trypanosoma cruzi. Triatoma dimidiata was the unique vector of this disease collected in San Juan Bautista Sakcabchen (SJBS) and Crucero San Luis (CSL). The total of 145 individuals were captured in SJBS; from these, 26.9%, 20% and 53.1% were collected in the sylvatic, peridomestic and intradomestic area, respectively. In CSL captures yielded 108 individuals: 40.7% in the sylvatic area, 20.4% peridomestic and 38.9% intradomestic. We found no correlation between climatic variables and population abundance of T. dimidiata. Dataset obtained suggests that individuals from the sylvatic area exhibit a high rate of natural infection by T. cruzi, with monthly percentages up to 61.5% for SJBS and 50% for CSL. At the peri and intradomestic level, the reservoirs apparently play an important role in the transmission, as the seroprevalence in dogs was 61.5% y 65.4%, for SJBS y CSL, respectively. Based on these findings, it was concluded that inhabitants of both communities are at a high risk of Chagas disease infection.     

Mapping of the distribution of Trypanosoma cruzi infection among small wild mammals in a conservation unit and its surroundings (Northeast-Brazil)

Maps are a useful tool that permits correlation of landscapes with hotspots of parasite transmission. Here, they were used as a tool for geovisualization to evaluate variables involved in the transmission of Trypanosoma cruzi among small wild mammals in an area endemic for Chagas disease, the "Serra da Capivara" National Park (PARNA) and its surroundings in Piauí State, Northeast Brazil. The implementation of a Geographical Information System (GIS) allowed the observation that a previously noted aggregated distribution of Triatoma sordida and Triatoma brasiliensis, T. cruzi prevalence and infection pattern of small wild mammals was directly or indirectly influenced by the local relief and human action. Small mammalian species diversity was higher in mesic refugia inside the park and in its buffer zone and lower in the disturbed area by anthropic activities. Didelphis albiventris was more abundant in the areas affected by human action. Thrichomys laurentius demonstrated to be an eclectic species and a competent reservoir of T. cruzi, being infected in all study areas. Small wild mammals infected with the TCII genotype of T. cruzi were localized only in the buffer zone of PARNA while TCI infected specimens were found in both areas, inside the PARNA and its buffer zone. The impact of biodiversity loss on the transmission cycle of T. cruzi in the wild environment was discussed.     

Chemical composition and microbicidal activity of extracts from Brazilian and Bulgarian propolis

AIMS: The chemical composition of ethanol extracts from a Brazilian (Et-Bra) and a Bulgarian (Et-Blg) propolis, and their activity against the protozoan Trypanosoma cruzi, several fungi and bacteria species were determined. METHODS AND RESULTS: The chemical composition was determined by high temperature high resolution gas chromatography coupled to mass spectrometry. Microbiological activity was assayed in vitro against T. cruzi, Candida albicans, Sporothrix schenckii, Paracoccidioides brasiliensis, Neisseria meningitidis, Streptococcus pneumoniae and Staphylococcus aureus. CONCLUSIONS: Et-Bra and Et-Blg, although with totally distinct compositions, were active against T. cruzi and the three species of fungi. Et-Blg was more effective than Et-Bra against bacteria, particularly N. meningitidis and Strep. pneumoniae. SIGNIFICANCE AND IMPACT OF THE STUDY: Although with different classes of components, both propolis extracts showed microbicidal activity. For the bactericidal activity it was possible to establish a positive correlation with the high content of flavonoids of the Bulgarian extract.     

Domestic,peridomestic and wild hosts in the transmission of Trypanosoma cruzi in the Caatinga area colonised by Triatoma brasiliensis

The role played by different mammal species in the maintenance of Trypanosoma cruzi is not constant and varies in time and place. This study aimed to characterise the importance of domestic, wild and peridomestic hosts in the transmission of T. cruzi in Tauá, state of Ceará, Caatinga area, Brazil, with an emphasis on those environments colonised by Triatoma brasiliensis. Direct parasitological examinations were performed on insects and mammals, serologic tests were performed on household and outdoor mammals and multiplex polymerase chain reaction was used on wild mammals. Cytochrome b was used as a food source for wild insects. The serum prevalence in dogs was 38% (20/53), while in pigs it was 6% (2/34). The percentages of the most abundantly infected wild animals were as follows: Thrichomys laurentius 74% (83/112) and Kerodon rupestris 10% (11/112). Of the 749 triatomines collected in the household research, 49.3% (369/749) were positive for T. brasiliensis, while 6.8% were infected with T. cruzi (25/369). In captured animals, T. brasiliensis shares a natural environment with T. laurentius, K. rupestris, Didelphis albiventris, Monodelphis domestica, Galea spixii, Wiedomys pyrrhorhinos, Conepatus semistriatus and Mus musculus. In animals identified via their food source, T. brasiliensis shares a natural environment with G. spixii, K. rupestris, Capra hircus, Gallus gallus, Tropidurus oreadicus and Tupinambis merianae. The high prevalence of T. cruzi in household and peridomiciliar animals reinforces the narrow relationship between the enzootic cycle and humans in environments with T. brasiliensis and characterises it as ubiquitous.     

Antigenic make-up of Trypanosoma cruzi culture forms: identification of a specific component.

A comparison of Trypanosoma cruzi water soluble antigens with those of stercorarian and salivarian trypanosomes, and Leishmania using immunoprecipitation in gels and immunoelectrophoresis, with the aid of hyperimmune rabbit serum and heterologous adsorptions showed the following. 1) There is a high complexity of soluble antigens of T. cruzi and T. rangeli. 2) At the intraspecific level our results demonstrated the antigenic stability of T. cruzi when maintained in vitro, and that there was quantitative antigenic consistency of the culture forms of different strains of T. cruzi from diverse geographic and parasite sources. At the interspecific level, the antigenic relationships between T. cruzi and the other Trypanosomatidae were established, as follows: 6/10ths of the antigens are shared by stercorarian species (T. dionisii, T. rangeli); 4/10ths by a salivarian trypanosome (T. brucei); and 3/10ths by Leishmania (L. donovani, L. mexicana). 3) Among the 4/10ths of antigenic components specific to T. cruzi, one component was characterized by its antigenicity and immunogenicity in natural and experimental infections, and in immunization experiments; this component was specific to T. cruzi when compared to the other Trypanosomatidae antigens.     

Distribution and infection of triatomines (Hemiptera: Reduviidae) by Trypanosoma cruzi in the state of Michoacán, Mexico

An entomological study of triatomine species was carried out to assess their prevalence in 10 localities of the state of Michoacán, Mexico. Entomological indices were calculated to estimate the risk for vector-borne transmission of Trypanosoma cruzi to the human population in this area. Four triatomine species (Triatoma barberi, Triatoma dimidiata, Meccus pallidipennis and Meccus longipennis) were collected from the study area. This is the first report of M. longipennis and T. dimidiata in Michoacán. M. pallidipennis was significantly (p < 0.05) more abundant than any of the other species collected in the study area. Infection indices were greater than 50% for each of the four collected triatomine species. Significantly more triatomines were collected from intradomiciliary areas than from peridomiciliary or sylvatic areas. Infestation, crowding and density indices were low, whereas colonisation indices were high in five localities. The current vectorial conditions in the study area require continuous entomological and serological surveillance to diminish the risk of T. cruzi transmission to human populations.     

Epidemiology of Chagas disease in Guatemala: infection rate of Triatoma dimidiata,Triatoma nitida and Rhodnius prolixus (Hemiptera,Reduviidae) with Trypanosoma cruzi and Trypanosoma rangeli (Kinetoplastida,Trypanosomatidae)

A five-year domiciliary collection in the 22 departments of Guatemala showed that out of 4,128 triatomines collected, 1,675 were Triatoma dimidiata (Latreille, 1811), 2,344 were Rhodnius prolixus Stal 1859, and only 109 were T. nitida Usinger 1939. The Chagas disease parasite, Trypanosoma cruzi, was found in all three species. Their natural infection rates were similar in the first two species (20.6%; 19.1%) and slightly lower in T. nitida(13.8%). However there was no significant difference in the infection rates in the three species (p = 0.131). T. dimidiata males have higher infection rates than females (p = 0.030), whereas for R. prolixus there is no difference in infection rates between males and females (p = 0.114). The sex ratios for all three species were significantly skewed. More males than females were found inside houses for T. dimidiata (p < 0.0001) and T. nitida (p = 0.011); a different pattern was seen for R. prolixus (p = 0.037) where more females were found. Sex ratio is proposed as an index to show the mobility of T. dimidiata in different populations. T. dimidiata is widely distributed in the country, and is also the main vector in at least ten departments, but R. prolixus with higher vectorial capacity is an important vector in at least two departments.     

Genetic Heterogeneity in Trypanosoma cruzi Strains From Naturally Infected Triatomine Vectors in Northeastern Brazil: Epidemiological Implications

Eighteen Trypanosoma cruzi strains isolated from naturally infected triatomines were studied genetically. The majority of the strains were from Triatoma brasiliensis, the principal vector of Chagas disease in the northeast of Brazil. Multilocus enzyme electrophoresis (MLEE) and randomly amplified polymorphic DNA (RAPD) analyses were used to investigate the genotypic diversity and the spread of the T. cruzi genotypes in different environments. MLEE clearly distinguished two distinct isoenzyme profiles, and RAPD analysis revealed 10 different genotypes circulating in rural areas. The strains could be typed as isoenzyme variants of the T. cruzi principal zymodeme Z1 (T. cruzi I). An effective program of epidemiological vigilance is required to prevent the spread of T. cruzi I strains into human dwellings.     

New scenarios of Trypanosoma cruzi transmission in the Orinoco region of Colombia

Rhodnius prolixus, a blood-sucking triatomine with domiciliary anthropophilic habits, is the main vector of Chagas disease. The current paradigm of Trypanosoma cruzi transmission in Columbia includes a sylvatic and domiciliary cycle co-existing with domestic and sylvatic populations of reservoirs. The aim of this study is to evaluate the population densities and relative abundance of triatomines and mammals that may be involved in the sylvatic cycle of Chagas disease to clarify the epidemiological scenario in an endemic area in the province of Casanare. Insect vectors on Attalea butyracea palms were captured using both manual searches and bait traps. The capture of mammals was performed using Sherman and Tomahawk traps. We report an infestation index of 88.5% in 148 palms and an index of T. cruzi natural infection of 60.2% in 269 dissected insects and 11.9% in 160 captured mammals. High population densities of triatomines were observed in the sylvatic environment and there was a high relative abundance of reservoirs in the area, suggesting a stable enzootic cycle. We found no evidence of insect domiciliation. Taken together, these observations suggest that eco-epidemiological factors shape the transmission dynamics of T. cruzi, creating diverse scenarios of disease transmission.     

Household risk factors for Trypanosoma cruzi seropositivity in two geographic regions of Ecuador

Few studies on the relationship between environmental factors and Trypanosoma cruzi transmission have been conducted in Ecuador. We conducted a cross-sectional study of household risk factors for T. cruzi seropositivity in 2 distinct geographical regions of Ecuador. Exposure information was collected via household surveys, and subjects were tested for serological evidence of T. cruzi infection. In total, 3,286 subjects from 997 households were included. In the coastal region, factors associated with seropositivity were living in a house with a palm roof (odds ratio [OR] = 2.63, 95% confidence interval, [1.61. 4.27]), wood walls (OR = 5.75 [2.04, 16.18]), or cane walls (OR = 2.81 11.31, 6.04]), and the presence of firewood in the peridomicile (OR = 2.48 [1.54, 4.01]). Accumulation of trash outside the home was associated with a reduced risk of seropositivity (OR = 0.25 [0.12, 0.51]). In the Andean region, living in a house with adobe walls was the only factor predictive of T. cruzi seropositivity. In conclusion, risk factors for T. cruzi transmission in Ecuador varied by geographic region, probably because of differing behavior of the triatomine vector species in each region. An understanding of the transmission dynamics of T. cruzi in a particular area is necessary for the development of effective Chagas disease control strategies in those areas.     

Infection by trypanosomes in marsupials and rodents associated with human dwellings in Ecuador

Small mammals trapped in domestic and peridomestic environments of rural Ecuador were screened for trypanosome infection by direct microscopy and hemoculture. Identification of species of trypanosomes was then performed by morphological characteristics and by polymerase chain reaction (PCR) assays. Of 194 animals collected, 15 were positive for infection (7.73%). Eight (4.12%) were infected with Trypanosoma cruzi (1 of 33 Didelphis marsupialis; 7 of 61 Rattus rattus). Eleven R. rattus (18.03%) harbored T. lewisi, 5 of which presented mixed infections with T. cruzi. Additionally, 1 of 3 Oryzomys xanthaeolus was infected with T. rangeli. No trypanosome infection was detected in Philander opossum (n = 1), Mus musculus (n = 79), Rattus norvegicus (n = 8), Akodon orophilus (n = 4), Sigmodon peruanus (n = 3), or Proechimys decumanus (n = 2). Many of the isolates belong to T. cruzi, the causative agent of Chagas disease, and R. rattus had the highest prevalence. Because of its abundance in the study areas, this species is considered an important reservoir for Chagas disease. This is the first report of T. lewisi and T. rangeli in Ecuador. This study is also the first to describe natural mixed infections of T. cruzi-T. lewisi.     

Trypanosomes of non-human primates from the National Centre of Primates, Ananindeua, State of Pará, brazil

Trypanosome infections were sought in 46 non-human primates captured principally in Amazonian Brazil. Twenty-two (47.8%) were infected with four Trypanosoma species: T. cruzi, T. minasense, T. devei and T. rangeli. These preliminary results confirmed the high prevalence and diversity of natural infections with trypanosomes in primates from Brazilian Amazon and were the first formal record of simian infections with trypanosomes in the State of Acre. The presence of T. cruzi-like and T. rangeli-like parasites are recorded in four new hosts.     

Nested clade and phylogeographic analyses of the Chagas disease vector Triatoma brasiliensis in Northeast Brazil

Triatoma brasiliensis (Hemiptera: Reduviidae: Triatominae) is the most important Chagas disease vector in the semiarid areas of Northeast Brazil. We analyzed mitochondrial cytochrome b sequence variation among 136 individuals representing 16 populations from across the species' distribution. Neighbor-joining and parsimony tree-building methods were used in conjunction with nested clade analysis to describe the systematics and phylogeography of this species. Our results indicate that T. brasiliensis is composed of four genetically distinct chromatic forms (referred to as brasiliensis, macromelasoma, juazeiro, and melanica) that present inter-population divergence values (0.027-0.119, corrected K2-p) and a pattern of haplotype geographic distribution compatible with the existence of a species complex. As a consequence, such forms can be treated as isolated targets in vector control programs. We were unable to infer what is shaping the population structure of the brasiliensis form as we obtained mutually exclusive causes of structure, namely a barrier to gene flow caused by past population fragmentation, and isolation by distance between populations (which would permit gene flow). We found indication of mitochondrial DNA introgression occurring among forms in putative hybrid zones.     

Trypanosoma cruzi from the Paraguayan Chaco: isoenzyme profiles of strains isolated at Makthlawaiya

At Makthlawaiya, in the Paraguayan Chaco, the prevalence of Trypanosoma (Schizotrypanum) cruzi infection among both domestic Triatoma infestans and domestic dogs was 38%, and IgG anti-T. cruzi antibody was detected by the quantitative enzyme-linked immunosorbent assay (ELISA) in 80% (105/133) of human sera. Ninety percent (25/28) of T. cruzi strains isolated from both T. infestans and dogs showed heterozygous isoenzyme profiles for glucose phosphate isomerase, phosphoglucomutase and 6-phosphogluconate dehydrogenase. These strains appeared to be closely related to Bolivian zymodeme 2. Three Paraguayan T. cruzi strains showed homozygous isoenzyme profiles, similar to those of major Brazilian zymodemes. It was concluded that T. cruzi strains with heterozygous isoenzyme profiles predominate in domestic transmission cycles in this highly endemic area of the Paraguayan Chaco.     

Cryptic speciation and recombination in the fungus Paracoccidioides brasiliensis as revealed by gene genealogies

Paracoccidioides brasiliensis is the etiologic agent of paracoccidioidomycosis, a disease confined to Latin America and of marked importance in the endemic areas due to its frequency and severity. This species is considered to be clonal according to mycological criteria and has been shown to vary in virulence. To characterize natural genetic variation and reproductive mode in this fungus, we analyzed P. brasiliensis phylogenetically in search of cryptic species and possible recombination using concordance and nondiscordance of gene genealogies with respect to phylogenies of eight regions in five nuclear loci. Our data indicate that this fungus consists of at least three distinct, previously unrecognized species: S1 (species 1 with 38 isolates), PS2 (phylogenetic species 2 with six isolates), and PS3 (phylogenetic species 3 with 21 isolates). Genealogies of four of the regions studied strongly supported the PS2 clade, composed of five Brazilian and one Venezuelan isolate. The second clade, PS3, composed solely of 21 Colombian isolates, was strongly supported by the alpha-tubulin genealogy. The remaining 38 individuals formed S1. Two of the three lineages of P. brasiliensis, S1 and PS2, are sympatric across their range, suggesting barriers to gene flow other than geographic isolation. Our study provides the first evidence for possible sexual reproduction in P. brasiliensis S1, but does not rule it out in the other two species.     

The opossum Didelphis virginiana as a synanthropic reservoir of Trypanosoma cruzi in Dzidzilché, Yucatán,México

In México, the role of mammals in the transmission cycle of Trypanosoma cruzi is poorly known. In the State of Yucatán, an endemic area of Chagas disease, both Didelphis virginiana and D. marsupialis occur sympatrically. However, until now, only the former species had been found infected with T. cruzi. To evaluate the role of D. virginiana in a peridomestic transmission, nine periods of capture-recapture were performed around the village of Dzidzilché, Yucatán. The sex, age, reproductive status, location, and presence of infection with T. cruzi were recorded for each opossum. The chromosome morphology was used to identify the opossum species. T. cruzi was identified by the presence of pseudocysts of amastigotes in cardiac muscle fibers of Balb/c mice inoculated with strains isolated from opossums. However, xenodiagnosis was the best diagnostic method. Triatoma dimidiata, the vector, were collected in and around the opossums' nests, and human dwellings; and were checked for T. cruzi. From 102 blood samples of D. virginiana examined 55 (53.9%) were positive to T. cruzi, the only two D. marsupialis captured were negative. Significant differences were found between infection, and both sex and reproductive condition. Eight out of 14 triatomines collected in peridomestic nests (57.1%), and 32 of 197 captured inside houses (16.3%) were found infected, suggesting a peridomestic transmission. The statistically high abundance of infected opossums and triatomines during the dry season (March to May) suggested the existence of a seasonality in the peridomestic transmission of T. cruzi in Dzidzilché.     

The genetic structure of Leishmania infantum populations in Brazil and its possible association with the transmission cycle of visceral leishmaniasis

Leishmania infantum is the etiologic agent of visceral leishmaniasis (VL) in the Americas, Mediterranean basin and West and Central Asia. Although the geographic structure of L. infantum populations from the Old World have been described, few studies have addressed the population structure of this parasite in the Neotropical region. We employed 14 microsatellites to analyze the population structure of the L. infantum strains isolated from humans and dogs from most of the Brazilian states endemic for VL and from Paraguay. The results indicate a low genetic diversity, high inbreeding estimates and a depletion of heterozygotes, which together indicate a predominantly clonal breeding system, but signs of sexual events are also present. Three populations were identified from the clustering analysis, and they were well supported by F statistics inferences and partially corroborated by distance-based. POP1 (111 strains) was observed in all but one endemic area. POP2 (31 strains) is also well-dispersed, but it was the predominant population in Mato Grosso (MT). POP3 (31 strains) was less dispersed, and it was observed primarily in Mato Grosso do Sul (MS). Strains originated from an outbreak of canine VL in Southern Brazil were grouped in POP1 with those from Paraguay, which corroborates the hypothesis of dispersal from Northeastern Argentina and Paraguay. The distribution of VL in MS seems to follow the west-east construction of the Bolivia-Brazil pipeline from Corumbá municipality. This may have resulted in a strong association of POP3 and Lutzomyia cruzi, which is the main VL vector in Corumbá, and a dispersion of this population in this region that was shaped by human interference. This vector also occurs in MT and may influence the structure of POP2. This paper presents significant advances in the understanding of the population structure of L. infantum in Brazil and its association with eco-epidemiological aspects of VL.     

Triatomines involved in domestic and wild Trypanosoma cruzi transmission in Concepción, Corrientes, Argentina

An entomological and serological survey was performed in three localities of the Department of Concepción, Province of Corrientes, Argentina in 1998 and 1999, to identify triatomines species involved in domestic and wild transmission of Chagas disease. Triatomines were collected by man/hour capture in 32 houses randomly selected and 44 nearby outdoor ecotopes. Trypanosoma cruzi infection in triatomines was assessed by direct microscopic observation (400x) of feces and polymerase chain reaction. Serological techniques used for people were Indirect Hemagglutination Test and Indirect Fluorescent Test. Triatomines were collected in 28.1% of the houses and 31.8% of the wild biotopes. Triatoma infestans (Klug 1834) was exclusively found indoors and T. cruzi infected 60% of them. Triatoma sordida (St?l 1859) was mainly found in extradomestic ecotopes where trypanosome infection rate reached 12.7%. Serological study of 98 local people showed that 29.6% were seroreactive; most of their houses were closed to wild biotopes colonized by T. sordida. Results indicate that there is an active T. infestans mediated transmission of Chagas disease in this zone that yields important human prevalence and that the populations of T. sordida in wild biotopes not only sustain the wild T. cruzi cycle but also represent an actual risk for people living in the area.