Head morphometry and isoenzymatic profile of two Triatoma infestans Klug, 1834 (Hemiptera, Reduviidae) populations.

The triatomine bug Triatoma infestans was probably originated in Bolivia and dispersed passively over large areas of South America, where it is the major vector of Trypanosoma cruzi. In its probable origin area this species shows two different patterns of behaviour, being found both in sylvatic and human related habitats. Such behaviour is not observed in other areas of its distribution, where it is exclusive to human related habitats. The main objective of the present study was to evaluate head morphometry characters and isoenzymes patterns of two T. infestans populations, one collected in Minas Gerais (Brazil) and other in the Cochabamba Valley (Bolivia), in order to elucidate the factors that could have an implication with the different colonization behaviour. The two populations presented differences in both morphometric (head size) and isoenzymes (specially PGM enzyme profile). The insects from the colonies reared for several years in laboratory conditions, showed reduction in head size starting from the third generation, maintaining this same size in all generations after, until 10 years after generation. The laboratory rearing conditions could be similar to human associated habitats, inducing certain level of genetic homogeneity. Our results showed increase of genetic homogeneity in Brazilian and laboratory-reared colonies from Bolivia, that may be due to a selection process due to passive dispersion, followed by several founder effects episodes and genetic drift.

Phlebotomine sand flies (Diptera: Psychodidae) and Leishmania infection in Gafanhoto Park, Divinópolis, Brazil.

The potential of Gafanhoto Park as an American cutaneous leishmaniasis (ACL) focus was evaluated by examination of sand fly vectors of the Leishmania parasite. This forest remnant is located in a periurban area of Divin6polis, Brazil, where autochthonous cases of ACL have been reported. Sand fly populations were monitored over a 2-yr period (2006-2008) by using light traps (HP and Shannon). During systematic collections with HP traps, 824 specimens in total (342 males and 482 females) of 21 species were captured. Most prevalent species were as follows: Brumptomyia brumpti (Larrouse), Lutzomyia aragaoi (Costa Lima), Lutzomyia lutziana (Costa Lima), Lutzomyia sordellii (Shannon & Del Ponte), and Lutzomyia whitmani (Antunes & Coutinho). Using Shannon traps, 257 specimens representing 15 species were collected (159 females and 98 males), with a high prevalence of L. whitmani and Lutzomyia neivai (Pinto), both vectors of Leishmania braziliensis (Vianna). To ascertain the level of natural infection, a sample of females captured in Shannon traps was assayed for the presence of Leishmania by using polymerase chain reaction-restriction fragment length polymorphism, where 39% of insects were positive. The most infected species was L. whitmani (29 sand flies; 18.2%), followed by L. neivai (21; 13.2%), Lutzomyia christenseni (Young & Duncan) (five; 3.1%), Lutzomyia pessoai (Coutinho & Barreto) (three; 1.9%), L. aragaoi (one; 0.6%), Lutzomyia fischeri (Pinto) (one; 0.6%), Lutzomyia lenti (Mangabeira) (one; 0.6%), L. lutziana (one; 0.6%), and Lutzomyia monticula (Costa Lima) (one; 0.6%). The finding of potential and incriminated vectors naturally infected with Leishmania reinforces the need of epidemiologic surveillance in the area.

Influence of the long-term Trypanosoma cruzi infection in vertebrate host on the genetic and biological diversity of the parasite.

The influence of the long-term Trypanosoma cruzi infection in vertebrate host on the biological and genetic properties of the parasite was evaluated. Four T. cruzi isolates obtained from different chronic chagasic dogs infected with Berenice-78 T. cruzi strain during 2 and 7 years were comparatively analyzed. The long-term T. cruzi infection has led to alterations in parasitemia, virulence and pathogenicity of Be-78 strain for mice. These biological parameters varied from low to high in realation to the parental strain. Randomly amplified polymorphic DNA and isoenzyme profiles detected two distinct genetic groups of parasites. The first group included the parental strain and two T. cruzi isolates, and the second group the two other isolates. Interestingly, the isolates of the second group showed a reversibility of the genetic profile to the parental strain after 25 passages in mice. No correlation between the genetic groups and biological properties of the isolates was observed. Our findings confirmed the population heterogeneity of the Be-78 strain, and showed how differently it responds to the long-term infection in the same vertebrate hosts.

Genetic studies of Psammolestes tertius (hemiptera: reduviidae: triatominae) using male genital morphology, morphometry, isoenzymes, and random amplified polymorphic DNA.

Two Brazilian populations of Psammolestes tertius (Ceará and Minas Gerais) collected from thornbird nests (Furnariidae) were compared by male genital morphology, morphometry, isoenzymes, and random amplified polymorphic DNA (RAPD). Male genitalia showed no difference between the populations. In contrast, morphometry, isoenzyme, and RAPD clearly distinguished the two populations. Possible mechanisms of dispersal and the origin of Psammolestes are discussed.

Genetic variability of Triatoma brasiliensis (Hemiptera: Reduviidae) populations.

Isoenzymes, random amplified polymorphic DNA (RAPD), and morphometry were used to compare genetic variability within and between three populations of Triatoma brasiliensis Neiva, 1911 from northeast Brazil. The isoenzyme profiles were identical for the three populations, whereas the complex RAPD patterns allowed clear discrimination between the three. Morphometric analysis, using characters of the head capsule, also showed discrimination between the three populations but only in comparisons of males, not females. The results show considerable genetic heterogeneity in T. brasiliensis, with an indication of geographic structuring possibly resulting from a recent series of domestication events.

[Use of random amplified polymorphic DNA (RAPD) in the populational study of Triatoma brasiliensis Neiva, 1911]. / Uso do Random Amplified Polymorphic DNA (RAPD) no estudo populacional do Triatoma brasiliensis Neiva, 1911.

We evaluated the genetic variability of Triatoma brasiliensis, the main vector of Chagas disease in Northeast Brazil, using specimens from three populations. Regions of genomic DNA were amplified by RAPD (Random Amplified Polimorphic DNA), using two primers. The products were visualized after polyacrylamide gel electrophoresis followed by silver staining. A dendrogram constructed through the Dice similarity coefficient allowed for separation of the tested specimens into three distinct groups. The populations captured in areas from Ceará State showed similar profiles, but different from that captured in Piauí State. Our results indicate that RAPD can be used successfully in triatomine studies and suggest the presence of genetic variability between different populations of T. brasiliensis.