Studies on Trypanosoma rangeli Tejera 1920: VI. Developmental pattern in the haemolymph of Rhodnius prolixus

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 changing pattern of pathology due to Schistosoma mansoni infection

A survey of the autopsy data on hepatosplenic schistosomiasis during periods, before and after the advent of new chemotherapeutic drugs, revealed that: a) the pathological presentation was the same for the two periods; b) the number of cases in the last five years is progressively decreasing; c) hepatosplenic disease due to schistosomiasis is becoming rare in young people. These data represent a change in the pattern of pathology in schistosomiasis, probably related to new chemotherapy.

Parasite and egg burden, hepatic collagen and histologic pattern of liver granulomas in selection III high and low antibody responder mice infected with Schistosoma mansoni

Selection III mice have particular immunological characteristics: they are high (H III) or low (L III) antibody producer animals, yet both lines display similar T cell responses and macrophage activities. We submittedthese mice to infection with Schistosoma mansoni to assess in vivo parasite and egg burden, hepatic collagen and cellular composition of granulomas in both lines. Titration of anti-Schistosoma IgG by ELISA showed remarkably higher values inH III line, at both studied periods (8th and 12th weeks post-infection). Nevertheless, the number of adult worms recovered from the portal system was similar inboth lines, being not associated with anti-Schistosoma antibody levels. There isan increase in hepatic collagen from the 8th to the 12th weeks post-infection, which is paralleled by an increase in the number of eggs in the liver. This association apparently occurs at the same radio in H III and L III animals. The most important difference found between the two lines was the outstanding contrast interms of volume and eosinophil counts in the granulomas, with lesions from H IIImice clearly being larger and containing more of these cells than LIII lesions.

Daily pattern of flight activity of Aedes albifasciatus in Central Argentina

Aedes albifasciatus is an important common mosquito in Central Argentina. Its a confirmed vector of the Western Equine Encephalitis and is responsible for loss of milk production in dairy cattle during peak populations. This paper reports the flight activity pattern of Ae. albifasciatus for different seasons, in the southern coast of the Mar Chiquita Lake (Central Argentina). Data were collected by sampling two sites between 1992 and 1993 with CDC traps and human-bait captures. Adult mosquito population density, estimated by CDC trapping and human-bait, were highly correlated. However, when compared to other species, the proportion of Ae. albifasciatus was higher in human-bait collections. Adult female populations were active only when temperature were higher than 6§C. Two daily biting peaks were observed (dusk and dawn) during the spring, summer and autumn, and only one peak during winter (around 15:00 pm). Adult abundance was significantly correlated (R²= 0.71; p<0.01) with temperature and illumination.

V3 peptide binding pattern and HIV-1 transmission route in Rio de Janeiro

To characterize antibody binding to a panel of V3 loop peptides representing diverse HIV-1 neutralization epitopes, 149 HIV-1 infected individuals from Rio de Janeiro (RJ) were investigated. Results were analyzed with respect to risk factors for infection and other epidemiological and clinical data. Peptide reactivity was not associated with sex, clinical status, CD4 counts, antigenemia or ß2-microglobulin serum level. A segregation of peptide reactivity according to route of infection was encountered. This finding suggests that more then one viral strain may be circulating in RJ, in subjects with different risk factors for HIV-1 infection. An investigation of prevalent HIV-1 genotypes, serotypes and immunotypes may be of importance for the design and selection of potential vaccines to be used in Brazil as well as for the selection of populations to be included in future vaccine efficacy trials.

Serotypes of Vibrio cholerae Non-O1 Isolated from Water Supplies for Human Consumption in Campeche, México and their Antibiotic Susceptibility Pattern

The presence of Vibrio cholerae non-O1 in water supplies for human consumption in the city of Campeche and rural locality of Bécal was investigated. V. cholerae non-O1 was detected in 5.9% of the samples obtained in deep pools of Campeche. Studies conducted in Bécal and neighbourhood of Morelos in Campeche indicated that collected samples harbored V. cholerae non-O1 in 31.5% and 8.7% respectively. There was a particular pattern of distribution of V. cholerae non-O1 serotypes among different studied regions. Accordingly, V. cholerae non-O1 serotype O14 predominated in the deep pools of Campeche and together with V. cholerae non-O1, O155 were preferentially founds in samples taken from intradomiciliary faucets in the neighbourhood of Morelos. Samples from Bécal predominantly presented the serotype O112. 60% and 53.8% of all studied strains of V. cholerae non-O1 proved to be resistant to ampicillin and carbenicillin. 3.1%, 7.7% and 6.2% presented resistant to doxycycline, trimethoprim-sulfamethoxazole and erythromycin respectively. The study showed the necessity of performing a strong epidemiologic surveillance for emergence and distribution of V. cholerae non-O1

Estimation of Genetic Divergence and Gene Flow between Culex pipiens and Culex quinquefasciatus (Diptera: Culicidae) in Argentina

Allele frequencies at seven polymorphic loci controlling the synthesis of enzymes were analyzed in six populations of Culex pipiens L. and Cx. quinquefasciatus Say. Sampling sites were situated along a north-south line of about 2,000 km in Argentina. The predominant alleles at Mdh, Idh, Gpdh and Gpi loci presented similar frequencies in all the samples. Frequencies at the Pgm locus were similar for populations pairs sharing the same geographic area. The loci Cat and Hk-1 presented significant geographic variation. The latter showed a marked latitudinal cline, with a frequency for allele b ranging from 0.99 in the northernmost point to 0.04 in the southernmost one, a pattern that may be explained by natural selection (FST = 0.46; p < 0.0001) on heat sensitive alleles. The average value of FST (0.088) and Nm (61.12) indicated a high gene flow between adjacent populations. A high correlation was found between genetic and geographic distance (r = 0.83; p < 0.001). The highest genetic identity (IN = 0.988) corresponded to the geographically closest samples from the central area. In one of these localities Cx. quinquefasciatus was predominant and hybrid individuals were detected, while in the other, almost all the specimens were identified as Cx. pipiens. To verify the fertility between Cx. pipiens and Cx. quinquefasciatus from the northern- and southernmost populations, experimental crosses were performed. Viable egg rafts were obtained from both reciprocal crosses. Hatching ranged from 76.5 to 100%. The hybrid progenies were fertile through two subsequent generations

Protective immunity induced in mice by F8.1 and F8.2 antigens purified from Schistosoma mansoni eggs

Schistosoma mansoni soluble egg antigens (SEA) were fractionated by isoelectric focusing, resulting in 20 components, characterized by pH, absorbance and protein concentration. The higher absorbance fractions were submitted to electrophoresis, and fraction 8 (F8) presented a specific pattern of bands on its isoelectric point. Protein 3 was observed only on F8, and so, it was utilized to rabbit immunization, in order to evaluate its capacity of inducing protective immunity. IgG antibodies from rabbit anti-F8 serum were coupled to Sepharose, and used to obtain the specific antigen by affinity chromatography. This antigen, submitted to electrophoresis, presented two proteic bands (F8.1 and F8.2), which were transferred to nitrocellulose membrane (PVDF) and sequenciated. The homology of F8.2 to known proteins was determined using the Basic Local Alignment Search Tool program (BLASTp). Significant homologies were obtained for the rabbit cytosolic Ca2+ uptake inhibitor, and for the bird a1-proteinase inhibitor. Immunization of mice with F8.1 and F8.2, in the presence of Corynebacterium parvum and Al(OH)3 as adjuvant, induced a significant protection degree against challenge infection, as observed by the decrease on worm burden recovered from portal system.

Differential gene expression during Trypanosoma cruzi metacyclogenesis

The transformation of epimastigotes into metacyclic trypomastigotes involves changes in the pattern of expressed genes, resulting in important morphological and functional differences between these developmental forms of Trypanosoma cruzi. In order to identify and characterize genes involved in triggering the metacyclogenesis process and in conferring to metacyclic trypomastigotes their stage specific biological properties, we have developed a method allowing the isolation of genes specifically expressed when comparing two close related cell populations (representation of differential expression or RDE). The method is based on the PCR amplification of gene sequences selected by hybridizing and subtracting the populations in such a way that after some cycles of hybridization-amplification genes specific to a given population are highly enriched. The use of this method in the analysis of differential gene expression during T. cruzi metacyclogenesis (6 hr and 24 hr of differentiation and metacyclic trypomastigotes) resulted in the isolation of several clones from each time point. Northern blot analysis showed that some genes are transiently expressed (6 hr and 24 hr differentiating cells), while others are present in differentiating cells and in metacyclic trypomastigotes. Nucleotide sequencing of six clones characterized so far showed that they do not display any homology to gene sequences available in the GeneBank.

Mepraia spinolai in the Southeastern Pacific Ocean Coast (Chile) - First insular record and feeding pattern on the Pan de Azúcar Island

In a field collection performed at Pan de Azúcar Island in Northern Chile, 95 specimens representing all instars of Mepraia spinolai were collected. The intestinal contents of 55 specimens were examined for Trypanosoma cruzi infection and were found to be negative. This is the first record of an insular habitat for M. spinolai, where the insects had fed mainly on seabirds (78%), some on marine mammals (5%), and some on reptiles (7%).

Description of immature stages of Culex ocossa Dyar & Knab, Culex delpontei Duret and Culex pereyrai Duret of the Melanoconion subgenus (Diptera: Culicidae)

The larva and pupa of Culex (Melanoconion) ocossa Dyar & Knab are redescribed and those of Culex (Melanoconion) delpontei Duret and Culex (Melanoconion) pereyrai Duret are described from specimens collected in the states of São Paulo and Paraná, Brazil. The pupa of Cx. ocossa differs from those of the other two species in having seta 5-IV-VI dark with strongly aciculated branches, and caudolateral angle of segment VIII produced into sharp point, and seta 1-P present; Cx. delpontei can be distinguished from Cx. pereyrai in possessing paddle lightly tanned, trumpet flared, and wing and leg cases lightly tanned, without pattern of dark spots; Cx. pereyrai can be recognized by having wing case with pattern of dark, discontinuously pigmented, longitudinal lines, and trumpet cylindrical, not flared. The larvae of the three species share the presence of seta 2-C placed medially to seta 1-C.

Genetic epidemiology of fecal egg excretion during Schistosoma mansoni infection in an endemic area in Minas Gerais, Brazil

There is considerable variation in the level of fecal egg excretion during Schistosoma mansoni infections. Within a single endemic area, the distribution of egg counts is typically overdispersed, with the majority of eggs excreted coming from a minority of residents. The purpose of this study was to quantify the influence of genetic factors on patterns of fecal egg excretion in a rural study sample in Brazil. Individual fecal egg excretions, expressed in eggs per gram of feces, were determined by the Kato-Katz method on stool samples collected on three different days. Detailed genealogic information was gathered at the time of sampling, which allowed assignment of 461 individuals to 14 pedigrees containing between 3 and 422 individuals. Using a maximum likelihood variance decomposition approach, we performed quantitative genetic analyses to determine if genetic factors could partially account for the observed pattern of fecal egg excretion. The quantitative genetic analysis indicated that between 21-37% of the variation in S. mansoni egg counts was attributable to additive genetic factors and that shared environment, as assessed by common household, accounted for a further 12-21% of the observed variation. A maximum likelihood heritability (h²) estimate of 0.44 ± 0.14 (mean ± SE) was found for the 9,604 second- and higher-degree pairwise relationships in the study sample, which is consistent with the upper limit (37%) of the genetic factor determined in the variance decomposition analysis. These analyses point to the significant influence of additive host genes on the pattern of S. mansoni fecal egg excretion in this endemic area.

Relationship between antennal sensilla pattern and habitat in six species of Triatominae

In order to determine if habitat similarity is correlated with a similarity of sensilla pattern, we analyzed six species of Triatominae present in two biogeographic regions of Brazil: the "caatinga" and the "cerrado". In broad terms Triatoma infestans (cerrado) and T. brasiliensis (caatinga) are found in human domiciles, T. sordida (cerrado) and T. pseudomaculata (caatinga) colonize peridomestic habitats, and Rhodnius neglectus (cerrado) and R. nasutus (caatinga) inhabit palm tree crowns. The number and distribution of four sensilla types (bristles, thin and thick walled trichoidea, and basiconica) were compared in these species. Sexual dimorphism of sensilla patterns was noted in T. sordida, T. brasiliensis and T. pseudomaculata. A principal component analysis showed three main groups: (i) species that live in the palms, (ii) domiciliated species and (iii) those living in the peridomestic habitat. T. infestans almost exclusively domestic, was placed at the centre of the canonical map and some individuals of other species overlapped there. These results support the idea that the patterns of antennal sensilla are sensitive indicators of adaptive process in Triatominae. We propose that those species that inhabit less stable habitats possess more types of sensilla on the pedicel, and higher number of antennal sensilla.