We present evidence for the putative role of Rhodnius robustus as extradomestic vector of Chagas disease in Western Venezuela. First, we assessed the validity of this triatomine species by genetic ...characterization in relation with some other species of the prolixus group. Random amplified polymorphic DNA data showed a clear separation between this species and R. prolixus and indicated a probable genetic heterogeneity within R. robustus. Faeces and gut contents were microscopically examined in 54 of 137 R. robustus collected in palm trees. According to this morphological examination, 18% were positive for Trypanosoma cruzi, 11% harboured T. rangeli and 11% showed mixed infection. Five of the seven samples examined gave a polymerase chain reaction major band of 270 bp specific of T. cruzi. The hybridization probes showed that R. robustus may transmit clones 20 and 39 (or genetically related ones) in Venezuela. Such a transmission might occur when, in absence of domestic R. prolixus and attracted by artificial light, R. robustus enters houses and feeds on humans, or when people are bitten outdoors. The lack of bugs inside houses could mean that the insects leave houses after feeding, or die without reproducing there.
In north‐central Venezuela Lutzomyia gomezi and Lu. ovallesi are the main endophilic/anthropophilic species of phlebotomine sandflies implicated as vectors of cutaneous leishmaniasis (CL). Lutzomyia ...ovallesi has been found infected with Leishmania braziliensis (1.2%) and less often with Le. mexicana (0.07%), while Le. braziliensis infections have also been found in Lu. gomezi (0.47%). We investigated population densities of these sandflies using two sampling methods with four series of collections between January 1991 and March 1995 at El Ingenio, Miranda State. All‐night outdoor collections from a Shannon trap were correlated with indoor collections from CDC light–traps by linear regression, which proved to be statistically significant for both species. Estimated numbers of female sandflies per house per night were found to be proportional to monthly precipitation (i.e. rainfall), with a lag time of seven months for Lu. ovallesi and of six months for Lu. gomezi. Predominance of Lu. ovallesi over Lu. gomezi (c. 10 :1 ) was observed throughout the year, with the number of infected females estimated as 0.043 ± 0.047 Lu. ovallesi and 0.0085 ± 0.0124 Lu. gomezi per CDC trap per house per night (ratio ∼ 5:1). The mean rate of new CL cases per house per year and sandfly abundance were correlated by linear regression, showing a statistically significant relationship for Lu. ovallesi but not for Lu. gomezi. The negative intercept indicated that, on average, the CDC trap density exceeds 800 Lu. ovallesi females/house/year before new CL cases occur at El Ingenio.
Triatoma sordida is widely distributed throughout the Chaco and the Eastern Region of Paraguay. It is associated to palm trees and artificial ecotopes located in peridomestic environments. The aim of ...this work was to determine genetic and morphometric variability and feeding behavior among population of T. sordida captured in domicile and peridomicile areas of Paraguay. Feeding contents and levels of genetic and morphometric variation were determined in 124 T. sordida from domicile and peridomicile populations of San Pedro and Paraguarí departments of the Eastern Region and Boquerón and Presidente Hayes departments of the Western region using Double Diffusion Gel, random amplified polymorphic DNA (RAPD), and head and wings morphometry. Morphometric analysis revealed isolation of populations by geographic region and larger size in triatomine populations from the Western Region. RAPD showed no specific patterns for domicile and peridomicile populations. The estimator of diversity (F ST; 0.08) and high gene flow obtained (N m; 5.7) did not allow the establishment of genetic differentiation within the same region. The blood meal source showed that poultry feeding was 38% of host preferences, and human blood was the second feeding preference (24%) in the insects from the Eastern Region while poultry feeding was predominant in those from the Western Region (30%). This work showed homogeneity between T. sordida populations of the same region and between domicile and peridomicile. The genetic diversity was determined among T. sordida populations of both geographical regions suggesting differentiation associated to eco-geographical isolation by distance. It is important to notice that pattern feedings were different between the two regions. Further studies should be focused on how phenetic and genetic variations could be related to the adaptation capacity of these triatomine populations to domicile, increasing their vector potentiality in the transmission of Chagas disease.
Lutzomyia pseudolongipalpis Arrivillaga & Feliciangeli is the first new sand fly species in the L. longipalpis species complex that has been formally described since it was separated by genetic as ...well as by morphological characters. It is the putative vector of the American visceral leishmaniasis in La Rinconada, Curarigua, a restricted focus in central western Venezuela. We investigated the feeding behavior of this species. The blood meals from 210 of 429 (48.9%) engorged females caught by CDC light traps were identified by a dot enzyme-linked immuno-absorbent assay using antisera against humans and common domestic animals. We propose a new index, the host selectivity index, which is the number of sand flies fed on a given host relative to the available biomass of that host, as an indicator of the feeding behavior of this phlebotomine sand fly. The host selectivity index is compared with the forage ratio, which is the percentage of sand flies fed on a given host by the percentage which that host represented in the total census of available animals and humans. The most attractive animal for L. pseudolongipalpis in Curarigua was the dog, whereas humans were shown to be relatively unattractive. However, not only selectivity or biomass, but also the accessibility to this host may have influenced these results. The low population density of dogs and the low accessibility of L. pseudolongipalpis to humans in relation to domestic animals might help to explain the sporadic transmission of visceral leishmaniasis in this focus.
Summary
The incidence of the American visceral leishmaniasis (AVL) in the Island of Margarita, a major tourist centre in Venezuela, has been increasing between 1998 and 2001. Lutzomyia longipalpis ...s.l. is the recognized vector, which was found naturally infected with Leishmania spp, indistinguishable from the parasites recovered from dogs and children. In 1999–2000, we conducted a control trial in Santa Ana del Valle and Las Cabreras, which have similar epidemiological and ecological conditions. The trial was based on intradomestic residual spraying of λ‐cyhalotrin, E.C., 25 mg/m2 and spatial fogging of fenitrothion around the houses at 30 g/ha. Sandfly abundance was recorded using Centers for Disease Control (CDC) traps indoors and outdoors. We found significantly reduced sandfly populations in the target locality. Wall bioassays showed that the residual effect of the insecticide lasts for about 3 months. We believe that indoor spraying with λ‐cyhalotrin three times a year, at a dose slightly greater than 25 mg/m2, might reduce the L. longipalpis s.l. population to a level low enough for achieving a significant reduction of the indoor transmission, thus protecting small children from the disease.
Lutzomyia pseudolongipalpis, the first new sand fly species within the longipalpis complex, is described based on females and males from La Rinconada, Curarigua, Lara State, Venezuela. Similar to ...Lutzomyia longipalpis sensu lato, females of the new species show spermathecae with 8–10 annulations and cibarial armature with 8–12 horizontal teeth. However, L. pseudolongipalpis females show conspicuous vertical cibarial teeth, large stipites and wing vein sections, round cerci, and short and broad valvifers that separate them from L. longipalpiss. l. females. L. pseudolongipalpis and L. longipalpis s. l. males are isomorphic, both having parameres with two curved setae on a simple tubercle. The analysis of morphometric characters and their diagnostic value is in progress.
The morphology of the spiracles of fourth instar larva in eight sandfly
species were examined by light and scanning electron microscopy.
Species studied were: Lutzomyia longipalpis (Lutz & Neiva), L.
...ovallesi (Ortiz), L. youngi Feliciangeli & Murillo, L. evansi
(Nunez-Tovar), L. trinidadensis (Newstead), L. migonei (Franca), L.
absonodonta Feliciangeli, and L. venezuelensis (Floch & Abonnenc).
In larvae of all eight species both thoracic and abdominal spiracles
are located at the top of a globular bulge. Their structure consists of
a spiracular plate with a sclerotized central portion and a rose-like
peripheral portion. The latter has circularly arranged papillae,
separated from each other by elongated septa. Each papilla is
longitudinally crossed by a fine cleft dividing it into two identical
parts. The taxonomic and adaptative value of spiracular morphology is
discussed.
Natural infection with Leishmania spp. in phlebotomine sandflies was searched for during a longitudinal study carried out from July 1997 to July 1998 in the village Catarnica, Municipality ...Independencia, Táchira State. This hamlet is an old endemic focus of cutaneous leishmaniasis in the Venezuelan Andean region, which lies close to the Colombian border at 1,300 m a.s.l., in an agricultural area mainly used for cultivating coffee. Phlebotomine sandflies were collected using Shannon traps placed in the peridomestic habitat from 19:00 to 21:00 hs. Males were stored in alcohol 70% while females were kept in Nunc vials with 10% DMSO and cryopreserved in liquid nitrogen for subsequent dissection and identification. The most abundant anthropophilic species was Lutzomyia spinicrassa with 3,032 males and 4,290 females (85.4%). Among 1,633 (38%) females of Lu. spinicrassa dissected, 26 (1.6%) were infected with promastigotes, while no natural infection was found in 209 females of other species. The flagellates were identified as Leishmania braziliensis braziliensis using PCR with species specific primers derived from nuclear DNA and hybridization using species specific probe labelled with digoxigenin. This parasite had been previously isolated from patients with cutaneous leishmaniasis from the same area. These results show Lu. spinicrassa as a new proven vector of Leishmania braziliensis in the Andean region of Venezuela.
L’infestation naturelle des phlébotomes par Leishmania spp. a été l’objet d’une étude longitudinale menée de juillet 1997 à juillet 1998 dans le village de Catarnica, municipalité d’Independencia, État de Táchira. Ce hameau est connu de longue date pour être un foyer de leishmaniose cutanée dans cette région andine du Venezuela à la frontière avec la Colombie, à une altitude moyenne de 1300 m, et où l’on cultive principalement le café. Les phlébotomes ont été capturés avec des pièges de Shannon placés en zone péridomestique de 19 à 21 heures. Les mâles ont été conservés dans de l’alcool à 70%, tandis que les femelles ont été placées dans des ampoules de Nunc avec 10% de DMSO et conservées dans de l’azote liquide pour les dissections et identifications ultérieures. L’espèce anthropophile la plus souvent capturée a été Lutzomyia spinicrassa : 3032 mâles; 4290 femelles (85,4%). Sur les 1633 femelles (38%) de Lu. spinicrassa disséquées, 26 (1,6%) étaient porteuses de promastigotes, tandis qu’aucune infestation naturelle n’était observée chez les 209 femelles d’autres espèces. Par PCR, ces flagellés ont été identifiés comme étant Leishmania braziliensis braziliensis. Ce parasite avait été isolé précédemment chez des personnes atteintes de leishmaniose cutanée dans la même région. Les résultats prouvent que Lu. spinicrassa est un nouveau vecteur de Leishmania braziliensis dans la région andine du Venezuela.
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