Vector competence of Culex quinquefasciatus say from different regions of Brazil to Dirofilaria immitis

The vector competence of Culex quinquefasciatus from five localities in Brazil to Dirofilaria immitis was evaluated experimentally. Females from each locality were fed on an infected dog (~ 6 microfilariae/µl blood). A sample of blood fed mosquitoes were dissected approximately 1 h after blood meal. These results demonstrated that all had ingested microfilariae (mean, 4.8 to 24.6 microfilariae/mosquito). Fifteen days after the infected blood meal, the infection and infective rates were low in all populations of Cx. quinquefasciatus. The mean number of infective larvae detected in the head and proboscis of these mosquitoes was 1-1.5. The vector efficiency, the number of microfilariae ingested/number of infective larvae, was low for all populations of Cx. quinquefasciatus. However, the survival rate for all populations was high (range 50-75%). The survival rate of Aedes aegypti assayed simultaneously for comparison was low (24.7%), while the vector efficiency was much higher than for Cx. quinquefasciatus. These data suggest that the vector competence of all assayed populations of Cx. quinquefasciatus to D. immitis in Brazil is similar and that this species is a secondary vector due to its low susceptibility. Nevertheless, vector capacity may vary between populations due to differences in biting frequency on dogs that has been reported in Brazil.

IS6110 fingerprinting of sensitive and resistant strains (1991-1992) of Mycobacterium tuberculosis in Colombia

The standardized method to study the polymorphism of IS 6110 was used to characterize 53 isolates of Mycobacterium tuberculosis obtained during 1991-1992 from 14 regions in Colombia. In Valle region cluster rate was 25% (4/16). The mean number of IS6110 band was 10 ± 3. Similarity between strains was of 60% in 81% of strains and this tended to be correlated with geographic origin. For the first time M. tuberculosis without IS6110 bands in restriction fragment length polymorphism analysis was found in Colombia. Additional studies are necessaries in order to best characterize the situation in relation to human immunodeficiency virus epidemic and recent changes in tuberculosis control program.

Geographic distribution and morphometric differentiation of Triatoma nitida usinger 1939 (Hemiptera: Reduviidae: Triatominae) in Guatemala

Triatoma nitida was found in 14 (0.4%) out of 3,726 houses located in six departments across Guatemala, which were surveyed from 1994 to 1998 by the man-hour collection method. Compared to previous information, the distribution of T. nitida in Guatemala has increased from five to nine departments; the species is present in mild climates at altitudes from 960 to 1,500 m. Fourteen percent of the intradomestic T. nitida were infected with Trypanosoma cruzi. The species was often found in conjunction with other triatomines (T. dimidiata and Rhodnius prolixus). The domestic and peridomestic presence of T. nitida in Guatemala was rare, but occasionally this species was colonizing human-made constructions. T. nitida appears to have a low importance as Chagas disease vector in Guatemala, as indicated by its scarce presence in the domestic habitats and defecation patterns. However, it clearly has potential to become a Chagas vector so we recommend an on-going study of the intradomestic presence of T. nitida following the control programs in Guatemala. Morphometric analysis of 47 T. nitida males from three localities showed quantitative differences between the populations, which indicates that geographic distance is an important factor in the structuring of T. nitida populations.

Electrocardiographic findings in Mexican chagasic subjects living in high and low endemic regions of Trypanosoma cruzi infection

In México the first human chronic chagasic case was recognized in 1940. In spite of an increasing number of cases detected since that time, Chagas disease in México has been poorly documented. In the present work we studied 617 volunteers subjects living in high and low endemic regions of Trypanosoma cruzi infection with seroprevalence of 22% and 4% respectively. Hemoculture performed in those seropositive subjects failed to demonstrate circulating parasites, however polymerase chain reaction identified up to 60% of them as positives. A higher level of anti-T. cruzi antibodies was observed in seropositive residents in high endemic region, in spite of similar parasite persistence (p < 0.05). On standard 12 leads electrocardiogram (ECG) 20% to 22% seropositive individuals from either region showed right bundle branch block or ventricular extrasystoles which were more prevalent in seropositive than in seronegative individuals (p < 0.05). In conclusion, the frequency or type of ECG abnormality was influenced by serologic status but not by endemicity or parasite persistence. Furthermore, Mexican indeterminate patients have a similar ECG pattern to those reported in South America.

Presence of Wolbachia endosymbionts in microfilariae of Wuchereria bancrofti (Spirurida: Onchocercidae) from different geographical regions in India

In view of the recent discovery of rickettsial endosymbionts, Wolbachia in lymphatic filarial parasites, Wuchereria bancrofti and Brugia malayi and subsequently of their vital role in the survival and development of the latter, antibiotics such as tetracycline are being suggested for the treatment of lymphatic filariasis, by way of eliminating the endosymbiont. But, it is essential to assess their presence in parasites from areas endemic for lymphatic filariasis before such a new control tool is employed. In the present communication, we report the detection of Wolbachia endosymbionts in microfilariae of W. bancrofti parasites collected from geographically distant locations of India, such as Pondicherry (Union Territory), Calicut (Kerala), Jagadalpur (Madhya Pradesh), Thirukoilur (TamilNadu), Chinnanergunam (TamilNadu), Rajahmundry (Andhra Pradesh), and Varanasi (Uttar Pradesh), using Wolbachia specific 16S rDNA polymerase chain reaction.

Trypanosoma rangeli sialidase: lack of activity in stocks from Panama and other regions

A total of 33 crude and cloned Trypanosoma rangeli stocks found as natural infections in human from Panama and other endemic areas of Central and South America were evaluated as producers of sialidase (SA) activity through the MU-NANA fluorescence test. Negative results were observed in 6 of the isolates: Panama (4), Honduras (1), and Brazil (1). In addition, an immunoblotting analysis confirm the presence of the SA antigen in these stocks without enzymatic activity. These findings must be considered in the interpretation of the biological significance of T. rangeli SA and in the proper characterization and identification of this parasite.

Epidemiology of visceral leishmaniasis through spatial analysis, in Belo Horizonte municipality, state of Minas Gerais, Brazil

The geographic information system approach has permitted integration between demographic, socio-economic and environmental data, providing correlation between information from several data banks. In the current work, occurrence of human and canine visceral leishmaniases and insect vectors (Lutzomyia longipalpis) as well as biogeographic information related to 9 areas that comprise the city of Belo Horizonte, Brazil, between April 2001 and March 2002 were correlated and georeferenced. By using this technique it was possible to define concentration loci of canine leishmaniasis in the following regions: East; Northeast; Northwest; West; and Venda Nova. However, as for human leishmaniasis, it was not possible to perform the same analysis. Data analysis has also shown that 84.2% of the human leishmaniasis cases were related with canine leishmaniasis cases. Concerning biogeographic (altitude, area of vegetation influence, hydrographic, and areas of poverty) analysis, only altitude showed to influence emergence of leishmaniasis cases. A number of 4673 canine leishmaniasis cases and 64 human leishmaniasis cases were georeferenced, of which 67.5 and 71.9%, respectively, were living between 780 and 880 m above the sea level. At these same altitudes, a large number of phlebotomine sand flies were collected. Therefore, we suggest control measures for leishmaniasis in the city of Belo Horizonte, giving priority to canine leishmaniasis foci and regions at altitudes between 780 and 880 m.

The untranslated regions of genes from Trypanosoma cruzi: perspectives for functional characterization of strains and isolates

The sequencing of Trypanosoma cruzi genome has been completed and a great deal of information is now available. However, the organization of protozoa genomes is somewhat elusive and much effort must be applied to reveal all the information coded in the nucleotide sequences. Among the DNA segments that needs further investigation are the untranslated regions of genes. Many of the T. cruzi genes that were revealed by the genome sequencing lack information about the untranslated regions. In this paper, some features of these untranslated segments as well as their applications in T. cruzi populations are discussed.

Chromosome variability in the Chagas disease vector Rhodnius pallescens (Hemiptera, Reduviidae, Rhodniini)

Rhodnius pallescens is the main vector of Trypanosoma cruzi in Panama and one of the most relevant secondary vectors in Colombia. Despite the importance of this species, there is limited knowledge about the genetic variability along its geographical distribution. In order to evaluate the degree of karyotype variability we analyzed the meiotic behavior and banding pattern of the chromosomes of 112 males of R. pallescens coming from different regions of Colombia and Panama. Using the C-banding technique we identified two chromosomal patterns or cytotypes characterized by differences in the amount, size and distribution of constitutive heterochromatic regions in the chromosome complement (2n = 20 autosomes plus XY in males). The individuals can be easily classified in each cytotype by the analysis of the chromosomes during first meiotic prophase. The frequencies of the cytotypes are variable according to the geographic origin of the populations. This chromosomal divergence together with morphological data supports the existence of three genetically different populations of R. pallescens and provides new information to understand the distribution dynamics of this species.

Survey to identify Mycobacterium leprae-infected household contacts of patients from prevalent regions of leprosy in Colombia

Leprosy in Colombia is in the post-elimination phase; nevertheless, there are regions of this country where the incidence is still around 3-4/100,000. Early detection of leprosy patients is a priority for achieving control and elimination of leprosy; however, the clinical exam is not very sensitive and thus, the majority of patients are diagnosed only when they demonstrate lesions, and damage to the nerves and skin has already occurred. The goal of the present study was to identify Mycobacterium leprae infection and immune responses in household contacts (HHC) of leprosy patients from three prevalent regions of Colombia. Clinical examination, the Mitsuda test, evaluation of IgM anti-PGL-I in the serum, the bacillar index (BI), and polymerase chain reaction (PCR) from nasal swabs (NS) were performed for 402 HHC of 104 leprosy patients during a cross-sectional survey. Positive titers for IgM anti-PGL1 were found for 54 HHC, and PCR-positive NS for 22. The Mitsuda reaction was negative for 38 HHC, although three were positive for IgM anti-PGL-1 titers. The data document that leprosy transmission among HHC is still occurring in a non-endemic country.

Regional pattern of the molecular types of Cryptococcus neoformans and Cryptococcus gattii in Brazil

The molecular types of 443 Brazilian isolates of Cryptococcus neoformans and Cryptococcus gattii were analyzed to determine their geographic distribution within Brazil and their underlying host conditions. The following data, imported from previous epidemiological studies as well as two culture collections, were analyzed for: place of isolation, source (clinical or environmental), host risk factors, species, serotype, mating type, and molecular type. Molecular typing by PCR-fingerprinting using primers for the minisatellite-specific core sequence of the wild-type phage M13 or microsatellites [(GACA)4, (GTG)5], restriction fragment length polymorphism of URA5 gene analysis, and/or amplified fragment length polymorphism (AFLP) identified eight major genotypes: VNI/AFLP1, VNII/AFLP1A, VNIII/AFLP2, and VNIV/AFLP3 for C. neoformans, and VGI/AFLP4, VGII/AFLP6, VGIII/AFLP5, and VGIV/AFLP7 for C. gattii. The most common molecular type found in Brazil was VNI (64%), followed by VGII (21%), VNII (5%), VGIII (4%), VGI and VNIV (3% each), and VNIII (< 1%). Primary cryptococcosis caused by the molecular type VGII (serotype B, MAT) prevails in immunocompetent hosts in the North and Northeast regions, disclosing an endemic regional pattern for this specific molecular type in the Northern Brazil.

Genetic variability in the 5' UTR and NS5A regions of hepatitis C virus RNA isolated from non-responding and responding patients with chronic HCV genotype 1 infection

Sequence variation among different hepatitis C virus (HCV) isolates has adaptive significance and reflects the modes and intensities of selection mechanisms operating on the virus. In this work, we sought to investigate using classical population genetics parameters, the genetic variability of HCV genotype 1 using the 5' UTR and NS5A regions from treatment non-responding and responding groups of patients. Both regions showed low genetic varia-bility and the 5' UTR showed neutral deviation. No differences were observed in the nonsynonymous/synonymous nucleotide substitution ratio among groups for NS5A. The analysis of molecular variance test of the 5' UTR region showed an 11.94% variation among groups. Phylogenetic analysis showed no correlation between sequence variations and therapeutic responses.

Population structure and diversity of the pathogenic fungus Aspergillus fumigatus isolated from different sources and geographic origins

Fifty-five clinical and environmental Aspergillus fumigatus isolates from Mexico, Argentina, France and Peru were analyzed to determine their genetic variability, reproductive system and level of differentiation using amplified fragment length polymorphism markers. The level of genetic variability was assessed by measuring the percentage of polymorphic loci, number of effective alleles, expected heterozygocity and by performing an association index test (I A). The degree of genetic differentiation and variation was determined using analysis of molecular variance at three levels. Using the paired genetic distances, a dendrogram was built to detect the genetic relationship among alleles. Finally, a network of haplotypes was constructed to determine the geographic relationship among them. The results indicate that the clinical isolates have greater genetic variability than the environmental isolates. The I A of the clinical and environmental isolates suggests a recombining population structure. The genetic differentiation among isolates and the dendrogram suggest that the groups of isolates are different. The network of haplotypes demonstrates that the majority of the isolates are grouped according to geographic origin.

Karyotypic variation and geographic distribution of Anopheles campestris-like (Diptera: Culicidae) in Thailand

Seventy-one isolines of Anopheles campestris-like were established from wild-caught females collected from human-biting and animal-biting traps at 12 locations in Thailand. All isolines had an average branch summation of seta 2-VI pupal skins ranging from 20.3-30.0 branches, which is in the range of An. campestris (17-58 branches). They showed three different karyotypes based on the amount of extra heterochromatin in the sex chromosomes, namely Forms B (X2, Y2), E (X1, X2, X3, Y5) and a new karyotypic Form F (X2, X3, Y6). Form B has been found only in Chaing Mai and Kamphaeng Phet populations, while Forms E and F are widely distributed throughout the species range. Genetic crosses between the 12 isolines, which were arbitrarily selected as representatives of An. campestris-like Forms B, E and F, revealed genetic compatibility that provided viable progeny through F2 generations, suggesting a conspecific nature of these karyotypic forms. These results are supported by the very low intraspecies variation (genetic distance < 0.005) of ITS2, COI and COII from genomic DNA of the three karyotypic forms.