The disparate geographical distribution of severe Chagas' disease as well as the variable response to treatment and diverse biological behaviour in mammals and triatomine bugs have led to the ...assumption that T cruzi might not be a single entity but a heterogeneous complex of organisms.1 Both biochemical comparisons (phenotyping) and DNA comparisons (genotyping) have shown that T cruzi is a remarkably diverse species.
Lutzomyia longipalpis (Lutz & Neiva) is the primary vector of visceral leishmaniasis in Venezuela. An analysis of alleles at seven enzyme-encoding loci among four populations from different ...geographic and epidemiological regions revealed strong genetic substructuring. Isozyme analysis indicated that L. longipalpis in Venezuela is a complex of at least two subspecies. Possible differences in population size during their evolutionary histories, varying colonization histories and geological events may explain discrepancies in the patterns of variation observed at genetic markers between these four populations.
The ecology of phlebotomine sandflies in an endemic focus of cutaneous leishmaniasis in Northern Venezuela (San Esteban, Carabobo State) was investigated through a year-term study. Three different ...habitats: viz. a house, a peridomestic area and a sylvatic area, were covered and the species composition, the abundance and occurrence of each species were analyzed in relation to the habitats, catching methods and hour of catching. L. panamensis, L. gomezi and L. ovallesi are the species which bite man, although almost exclusively at night. All of them hide by day and are common in the sylvatic area. Moreover, L. panamensis and L. gomezi successfully approach the house and seem to settle in the peridomestic area. L. shannoni and L. olmeca bicolor also approach and accidentally bite man. L. trinidadensis, L. atroclavata and L. cayennensis are the common non-anthropophilic species in the area.
A field population of Lutzomyia longipalpis from La Rinconada, Lara State, an endemic focus of visceral leishmaniasis in Venezuela, was tested for susceptibility to organochlorine (DDT 2%), carbamate ...(propoxur 0.01%), organophosphate (malathion 2%, fenitrothion 1%, and pirimiphos methyl 1%), and pyrethroid (deltamethrin 0.06%, lambdacyhalothrin 0.06%, and permethrin 0.2%) insecticides. Susceptibility to the insecticides tested was evaluated in the field population of L. longipalpis and compared with a laboratory reference strain. The (LT95) to propoxur and malathion insecticides for the field population was lower than the LT95 for the laboratory reference strain, demonstrating high susceptibility to these compounds. A low level of resistance at LT50 (< 3-fold) was found for fenitrothion, pirimiphos methyl, and permethrin insecticides, but no resistance was detected at LT95. No significant resistance at the LT50 and LT95 was detected for the pyrethroids deltamethrin and lambdacyhalothrin. The susceptibility levels of L. longipalpis to the insecticides tested are discussed in view of a future control program against endophilic vectors of leishmaniases based on the use of pesticides.
An entomological survey was undertaken from January 1991 to February 1992 in El Ingenio, Miranda State, Venezuela, an endemic area of cutaneous leishmaniasis: prevalence of 10.7 cases per 100,000 ...inhabitants. A total of 4863 female sandflies (Phlebotominae) of fourteen species were collected in Shannon traps, then dissected and examined for leishmanial infections. Lutzomyia ovallesi (85.4%) and Lu. gomezi (11.2%) were the predominant anthropophilic species of sandfly. Fifty-one (1.19%) Lu.ovallesi and two (0.47%) Lu.gomezi had natural infection with Leishmania promastigotes. Identification of the parasites was done by using the polymerase chain reaction (PCR) and DNA hybridization. Two isolates from Lu.gomezi and forty-nine from Lu.ovallesi were typed as Leishmania braziliensis and three of the latter reacted with Le.mexicana also. This is the first report of Lu.gomezi with parasites typed as Le.braziliensis. We concluded that Lu.ovallesi is the primary vector of cutaneous leishmaniasis in the north-central area of Venezuela and Lu.gomezi should be regarded as an additional vector.
The ultrastructure of the egg chorionic sculpturing of eight neotropical sand fly species (Lutzomyia townsendi (Ortiz, 1959), L. youngi Feliciangeli and Murillo, 1987, L. spinicrassa Osorno, Morales, ...Osorno, and Hoyos, 1969, L. evansi Nunez Tovar 1924, L. lichyi, Floch and Abonnenc, 1950, L. trinidadensis Newstead, 1922, L. venezuelensis Floch and Abonnenc, 1948, and L. olmeca bicolor, Fairchild and Theodor, 1971) was studied using scanning electron microscopy, (SEM). A next, pattern, ellipses bound by fine longitudinal ridges, was observed in L. venezuelensis. Moreover, the chorionic ultrastructure was useful for separating three isomorphic species (L. townsendi, L. youngi, and L. spinicrassa), of which L. youngi and L. spinicrassa are sympatric in some endemic foci of Tachira State, Venezuela
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