Browsing by Autor "Dujardin, JP"

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Cryptic speciation in Lutzomyia (Nyssomyia) Trapidoi (Fairchild & Hertic) (Diptera: Psychodidae) detected by multilocus enzyme electrophoresis
(Facultad de Medicina, Enfermería, Nutrición y Tecnología Médica, 1996) Dujardin, JP
Abstract Lutzomyia trapidoi is the major vector of cutaneous leishmaniasis in Ecuador. In the framework of an epidemiologic study, female Lu. trapidoi sand flies were captured on human bait in La Tablada and Paraiso Escondido. Some coloration heterogeneity among the specimens caught led us to look for the existence of cryptic species using multilocus enzyme electrophoresis. In 196 specimens studied, five of seven enzyme loci proved to be variable, making it possible to check for departures from panmixia both by Hardy-Weinberg statistics and linkage disequilibrium analysis. Two discrete groups were clearly distinguished, which could be differentiated by the diagnostic locus glycerophosphate dehydrogenase. The two groups occurred in sympatry within each locality. Genetic distances measured between these two groups were consistent with values usually found between distinct species. These results suggest the existence of a least two sibling species in Paraiso Escondido as well as La Tablada. The epidemiologic relevance of these results is discussed.
Étude de 11 enzymes et données de génétique formelle pour 19 loci enzymatiques chez Triatoma infestans (Hemiptera: Reduviidae)
(Facultad de Medicina, Enfermería, Nutrición y Tecnología Médica, 1985) Dujardin, JP
Résumé. Onze enzymes ont été analysées par électrophorèse sur acétate de cellulose chez Triatoma infestans (Klug. 1834), vecteur principal de la maladie de Chagas. Ces onze enzymes correspondent au moins á 19 loci, dont trois seulement sont variables: la phosphoglucomutase (PGM, 2.7.5.1), la 6 phosphogluconate déshydrogénase (6PGDH, 1.1.1.44) et I' alpha-glycérophosphate déshydrogénase (αGDH, 1.1.1.8). Les études de croisement révèlent qu'il s'agit de trois loci dialléliques, et les images d'hétérozygotie plaident pour des protéines dimériques dans le cas de la 6PGDH et de I' αGDH, monomèrique dans le cas de la PGM. Trois loci variables sur 19 représentent une variabilité génétique faible comparée à celle des arthropodes étudiés par des techniques similaires: chez T. infestans, le taux de polymorphisme est de 15,7% et I'hétérozygotie moyenne de 0,04. Ces valeurs trois fois plus basses que les valeurs moyennes suggèrent que l'expansion territoriale de ce vecteur en Amérique du Sud a pu se produire à une date à une date récente à partir d'une population de petite taille (effet fondateur).
Isozyme evidence of lack of speciation between wild and domestic triatoma infestans (Heteroptera: reduviidae) in Bolivia
(Facultad de Medicina, Enfermería, Nutrición y Tecnología Médica, 1987) Dujardin, JP
Abstract . Wild and domestic Triatoma infestans from the Cochabamba region of Bolivia were virtually identical at l9 gene loci coding for enzymes. No allele was distinctive of either the wild or the domestic populations. Hence, there is no evidence that the 2 populations are different species. Domestic populations separated by 20 km showed statistically significant differences in allelic frequencies; this is compatible with the hypothesis of other authors that migrations of T. infestans are limited when feeding conditions are satisfactory. Fifteen trypanosomatid stocks isolated from wild T. infestans were shown by isozyme analysis to be Trypanosonta cruzi. This provides evidence that wild T infestans are involved in the Chagas' disease cycle. The T. cruzi isozymic strains from wild T. infestans were genetically similar to those isolated from domestic T. infestans in the same region. This supports the hypothesis that there is no speciation between wild and domestic T. infestans, and that wild and domestic T. cruzi cycles may overlap in this region. Among T. cruzi vectors , Triatoma infestans (Klug) is the best adapted to human habitats (Lent & Wygodzinsky 1979). Its wide distribution in South America may be due to the recent spread of human populations on that continent. Before it adapted to human habitats, T. infestans probably fed on wild animals (Usinger et al. 1966) and was less numerous and less widespread than at present. Wild T. infestans populations occur in the Cochabamba Valley of Bolivia, where they live in rocky habitats associated with, wild guinea pigs (Fig. 1). Wild T. infestans are morphologically indistinguishable from domestic specimens. To clarify the taxonomic and evolutionary relationships between wild and domestic T. infestans , we compared them genetically by means of isozyme analysis and similarly compared the Trypanosoma cruzi isozymic strains isolated from them. The results bear on the important question of whether wild T. infestans might be involved in the domestic cycle of Chagas' disease.
Metric differences between silvatic and domestic Triatoma infestans (Heteroptera: Reduviidae) in Bolivia
(Facultad de Medicina, Enfermería, Nutrición y Tecnología Médica, 1997) Dujardin, JP
Abstract. One hundred and fifty-seven specimens of Bolivian Triatoma infestans (Klug 1834), including 44 from the silvatic focus at Cochabamba (Bolivia), were compared using morphometric characters of the head capsule. From these specimens, 10 silvatic and 28 domestic adults were also compared using additional morphometric characters of the membranous part of the hemelytra. Nonparametric univariate comparisons between specimens from silvatic and domestic ecotopes indicated the importance of the postocular region as a possible diagnostic character for nymphs and adults from the different ecotopes, and they detected wing differences in males. Populations became more distinct entities when head or wing characters were considered jointly in canonical variate analysis. Regardless of whether size variation was considered, canonical variate analysis generally showed greater significance for wing than for head features. These morphological differences between silvatic and domestic bugs, particularly unrelated to size differences, are interpreted to indicate incipient separation between silvatic and domestic populations that had not been detected by previous isoenzyme analyses, and suggest a reinterpretation of the epidemiological significance of silvatic populations of T. infestans in Bolivia.
Morphometrics of domestic Panstrongylus rufotuberculatus in Bolivia
(Facultad de Medicina, Enfermería, Nutrición y Tecnología Médica, 1998) Dujardin, JP
The trend to domesticity in Triatominae may represent a transitionary phase towards increasing vectorial importance in the transmission of Chagas disease to humans, and requires sustained entomological surveillance. Although generally considered a sylvatic species. Panstrongylus rufotuberculatus has been recently captured inside human dwellings in the provinces of Nor Yungas and Muñecas in the Departament of La Paz, Bolivia, providing evidence of this species’ ability to colonise domestic habitats. The results of previous research on domestic and sylvatic specimens of other species of Triatominae indicate that morphometrics could be used to monitor this adaptive process. The most likely cause of differences seen in the size and shape of bugs from domestic colonies of P. rufotuberculatus from two neighbouring villages in Bolivia is probably genetic drift rather than environmental influences. Comparison with allopatric sylvatic specimens, including the holotype of P. rufotuberculatus, showed a general reduction in size from sylvatic to domestic specimens.
Population structure of Andean Triatoma infestans : allozyme frequencies and their epidemiological relevance
(Facultad de Medicina, Enfermería, Nutrición y Tecnología Médica, 1998) Dujardin, JP
Abstract. Triatoma infestans (Hemiptera: Reduviidae) from 22 Andean localities in Bolivia (n = 968) and Peru (n=37) were analysed by multi-locus enzyme electrophoresis. Among 12 gene-enzyme systems analysed, GPD, 6GPD and PGM were polymorphic, ACON, G6PD, GPI, 1DH, LAP, MDH, ME, PEP-A and PEP-B were monomorphic. Allozyme frequencies were analysed in relation to geographical and climatic factors, and the presence or absence of Trypanosoma cruzi infection. At one locality (Vallegrande, Bolivia), the frequency of 6Pgd-1 was significantly higher in infected (41% of 85) than in uninfected (17% of 83) adult T. infestans, although no such difference was found among nymphs (n = 347). From other localities, only insects infected with T. cruzi were subjected to isozyme analysis. Populations of T. infestans within villages showed panmixia, while genetic differentiation of T. infestans between villages was correlated with the distance between them. The genetic structure of T. infestans natural populations followed an “isolation by distance” model, involving a series of founder effects followed by genetic drift, rather than adaptation in response to differential selection pressures. This conforms with circumstantial evidence that T. infestans spread, mainly in association with recent human migrations, from a source, probably in southern Bolivia. Isoenzyme characterization of populations of T. infestans could be used to infer sources of re-infestation during the surveillance phase of control programs.
The origin of Rhodnius prolixus in Central America
(Facultad de Medicina, Enfermería, Nutrición y Tecnología Médica, 1998) Dujardin, JP
Rhodnius prolixus Stal (Hemiptera, Reduviidae) is the main domestic vector of Chagas disease in Venezuela and Colombia, and also in parts of Central América (El Salvador, Guatemala, Honduras and Nicaragua). In Central America it seems to be confined entirely to domestic and peridomestic habitats, whereas sylvatic populations have been recognized in various parts of Venezuela and Colombia, mainly in palm tree crowns, which are assumed to represent the original ecotope of this species (e.g. Gamboa, 1963).
The use of morphometrics in entomological surveillance of sylvatic foci of Triatoma infestans in Bolivia
(Facultad de Medicina, Enfermería, Nutrición y Tecnología Médica, 1997) Dujardin, JP
Abstract Jamach'uma (Cochabamba, Bolivia) is a small village surrounded by sylvatic foci of Triatoma infestans. Houses in the village were also infested with T. infestans, and were sprayed in December 1992 as part of a Chagas disease vector control trial. Ten months later the houses were found to be again infested with a few fifth instar nymphs of T. infestans. These nymphs were compared by seven head measurements with 36 fifth instar nymphs collected from houses in Jamach'uma before treatment, and with two sets of nymphs originating from the surrounding sylvatic foci: eight specimens collected in 1992 and nine specimens collected in 1995. The results are discussed in relation to the possible mechanisms of the apparent reinfestation: recrudescence of a residual domestic population or reinvasion of the houses from surrounding sylvatic foci. Quantitative comparisons support the former hypothesis.