Abundance of Lutzomyia ovallesi but not Lu. gomezi (Diptera: Psychodidae) correlated with cutaneous leishmaniasis incidence in north-central Venezuela

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.     

Vector competence of some Neotropical sandflies for the Leishmania (Viannia) braziliensis complex

Abstract. To evaluate the vector competence of some Lutzomyia spp. (Diptera: Psychodidae) for Leishmania (Viannia) spp. (Kinetoplastida: Trypanosoma-tidae), experimental infections of anthropophilic sandflies from the Colombian Pacific coast were performed, through membrane feeding and xenodiagnosis on hamsters infected with Le.(V.)braziliensis or Le.(V.)panamensis. Wild-caught or F, generation females of Lutzomyia gomezi, Lu.hartmanni, Lu.panamensis and Lu. trapidoi were allowed to feed on hamster lesions and then maintained at 26^oC and >80% r.h. on a sugar-water diet until dissection on the fifth day post-infection (p.i.).
Despite similar infection rates (range 37–44%) in both Lu.gomezi and Lu.trapidoi , infections were heavier (>100 parasites) in the latter species. Infections of Lu.trapidoi with Le.braziliensis ( n = 21) and Le.panamensis (n = 27) showed parasite migration toward the foregut, with promastigote colonization of the stomodeal valve and appearance of infective forms. In contrast, infections of Lu.gomezi with Le. braziliensis (n = 10) and Le.panamensis (n = 5) were light (<50 parasites) and usually restricted to the pylorus. In Lu.hartmanni , only a few promastigotes were found in the pylorus and midgut of 3/8 specimens infected with Le.braziliensis , and no Le.panamensis developed (n = 19). By day 5 p.i., promastigote colonization of the hind- and midgut by Le.panamensis was observed in 2/4 Lu.panamensis but not Le.braziliensis (n = 3).
It was concluded that Lu.trapidoi is a more efficient vector than Lu.gomezi for both Le.braziliensis and Le.panamensis , and that Lu.hartmanni and Lu.panamensis are of minor importance for Leishmania transmission in this endemic area.     

Multiplex-PCR for detection of natural Leishmania infection in Lutzomyia spp. captured in an endemic region for cutaneous leishmaniasis in state of Sucre, Venezuela

We studied the natural infection of Lutzomyia (Lutzomyia) sp. with Leishmania in endemic foci of cutaneous leishmaniasis in the Paria peninsula, state of Sucre, Venezuela. Sand flies were collected between March 2001 and June 2003, using Shannon light-traps and human bait. Of the 1291 insects captured, only two species of phlebotomines were identified: L. ovallesi (82.75%) and L. gomezi (17.42%). A sample of the collected sand flies (51 pools of 2-12 individuals) were analyzed by using a multiplex-PCR assay for simultaneous detection of New Word Leishmaniaand Viannia subgenera. The results showed a total of 8 pools (15.68%) infected; of these, 7 were L. ovallesi naturally infected with L. braziliensis (2 pools) and L. mexicana (5 pools) and 1 pool of L. gomezi infected by L. braziliensis.     

Phlebotomine sandflies and leishmaniasis risks in Colombian coffee plantations under two systems of cultivation

The phlebotomine sandfly fauna of traditional (shaded) and intensified (unshaded) coffee plantations in Colombia was sampled by a variety of methods and the species composition and density under the two systems compared. Twenty species of Lutzomyia sandflies (Diptera: Psychodidae: Phlebotominae) were collected, of which eight were found only in the 'Coffee Axis' ('Eje Cafetero') of the departments of Caldas, Risaralda and Quindio, six were exclusive to the department of Norte de Santander and six occurred in both regions. Four species were collected only in traditional plantations and two exclusively in intensified ones. At least 13 species occurred in both plantation types. Fifteen species are opportunistic man-biters and eight are suspected vectors of leishmaniasis caused by Le. braziliensis, Le. panamensis or Le. mexicana. Seven species were collected inside houses and may be involved in intradomiciliary transmission of Leishmania. The dominant species in Norte de Santander was Lu. spinicrassa, which made up 93.8% of all the sandflies collected in this department. This species was absent from the Eje Cafetero and a number of others among the 15 recorded there might be responsible for Leishmania transmission in this region, including Lu. trapidoi, Lu. yuilli, Lu. gomezi, L. hartmanni and Lu. ovallesi. Sandfly population densities were significantly higher in traditional plantations than in intensified ones. Residents of traditional plantations were able to describe sandflies in significantly more detail than those of intensified plantations, based on seven basic characteristics related to the appearance and biting behaviour of the insects.     

Ecology of phlebotomine sand flies (Diptera: Psychodidae) in a focus of Leishmania (Viannia) braziliensis in northeastern Colombia.

The phlebotomine sand fly fauna of two coffee plantations in a Leishmania-endemic area of Norte de Santander, Colombia was studied. Regular insect collections using a variety of methods were made for three and a half years. Information was obtained on diurnal resting sites, host range and seasonal abundance for 17 species, of which five (Lutzomyia spinicrassa, Lu. serrana, Lu. shannoni, Lu. ovallesi and Lu. gomezi) were far more numerous than the others, anthropophilic and present throughout the year. The behaviour of these and the remaining 12 species is discussed in relation to their potential role in transmission of Leishmania (Viannia) braziliensis in the area.     

Isolation of Leishmania (Viannia) braziliensis from Lutzomyia spinicrassa (species group Verrucarum) Morales Osorno Mesa, Osorno and Hoyos 1969, in the Venezuelan Andean region

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 11.6%) 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.     

Distribution of sand flies (Diptera: Psychodidae) at different altitudes in an endemic region of American cutaneous leishmaniasis in the State of Espírito Santo, Brazil.

The involvement of different sand fly species in the transmission of American cutaneous leishmaniasis (ACL) at different altitudes was evaluated in the municipality of Afonso Cláudio in the State of Espírito Santo, Brazil, from November 1995 to February 1997. CDC light traps and Shannon traps baited with human volunteers were hung simultaneously at three altitudes of a river valley: (a) 650-750 m in an area of active ACL transmission; (b) 750-850 m in a transitional area; and (c) 850-950 m in an area where no ACL transmission occurred. A total of 13,363 specimens belonging to 28 species was collected. The five most abundant man-biting species were Lutzomyia intermedia, which constituted 24.3% of the total, Lu. migonei (22.3%), Lu. whitmani (15.4%), Lu. fischeri (14.9%) and Lu. monticola (5.8%). Analysis of the distribution of these species at the three altitudes provided evidence that Lu. fischeri and Lu. monticola were not involved in ACL transmission, whereas Lu. migonei and Lu. whitmani might act as secondary vectors of Leishmania (Viannia) braziliensis and Lu. intermedia was probably the principal vector of the parasite. These results reinforce those published in the existing literature, which indicate that Lu. intermedia is the main vector of Le. (V.) braziliensis in Southeast Brazil, while Lu. migonei and Lu. whitmani are of secondary importance.     

Leishmaniasis in Brazil. XXV. Sandfly vectors of Leishmania in Pará State, Brazil

Leishmania of the braziliensis complex were isolated from various members of the squamiventris series sandflies, including Psychodopygus chagasi (Costa Lima), P.s.maripaensis (Ready et al.), P.s.squamiventris (Lutz & Neiva), and also P.ayrozai (Barreto & Coutinho) and Lutzomyia umbratilis Ward & Fraiha. Three different serodemes of Le.b.guyanensis Floch were isolated from Lu.anduzei Rozeboom, Lu.umbratilis and Lu.whitmani Antunes & Coutinho, simultaneously captured in the same area. Unidentified Leishmania were isolated from P.claustrei Abonnenc et al., and trypanosomes from Lu.pinottii Damasceno & Arouck and an unidentified species of Lutzomyia. A naturally infected female P.s.maripaensis transmitted a braziliensis complex Leishmania, by bite, to a hamster.     

Ecology of sandflies (Diptera:Psychodidae) in a restricted focus of cutaneous leishmaniasis in northern Venezuela. II. Species composition in relation to habitat, catching method and hour of catching

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.     

Cotton rats (Sigmodon hispidus) and black rats (Rattus rattus) as possible reservoirs of Leishmania spp. in Lara State,Venezuela

A total of 519 wild animals belonging to eleven species were collected during a two year study in a cutaneous leishmaniasis endemic area in Venezuela (La Matica, Lara State). The animals were captured in home-made Tomahawk-like traps baited with maize, bananas or other available local fruits, and parasites were isolated from 27 specimens. Two different species were found naturally infected with flagellates, i.e., cotton rats (Sigmodon hispidus) and black rats (Rattus rattus). Characterization of the parasites using PCR, kDNA restriction pattern and hybridization with species-specific probes revealed the presence of Leishmania (L.) mexicana in three of the black rats and Leishmania (V.) braziliensis in two others. The latter species was also identified in the single positive specimen of S. hispidus. The results suggested both species of animals as possible reservoirs of Leishmania sp.     

Epidemiological characteristics of American cutaneous leishmaniasis in an endemic region of the State of Bahia. III. Phlebotomine fauna

The phlebotomine fauna is highly varied in Três Bra?os, an endemic area of american cutaneous leishmaniasis, situated in the cacao growing region in the southeast of Bahia State, Brazil. Thirty spécies of the Lutzomyia genus were identified in 13,535 specimens collected between 1976 and 1984. Lutzomyia whitmani was the dominant species accounting for 99% of flies in the peridomicile and 97.5% of those caught in homes. In the forest the predominant species were Lu. ayrozai and Lu. yuilli. Lu. whitmani accounted for only 1.0% of the specimens examined. Lu. flaviscutellata, the proven vector of Leishmania mexicana amazonensis, was also collected in small numbers. Lu. wellcomei, a known vector of L. braziliensis braziliensis in the Serra dos Carajás, Pará, Brazil was not encountered in the Três Bra?os region where the parasite causing human infections is usually L.b. braziliensis. Although we have not encountered a natural infection with leishmanial promastigotes in 1,832 females of the various species examined, we discuss the probability that Lu. whitmani is the vector of L.b. braziliensis in the region maintaining transmission in dogs and man.     

Ecology of sandflies (Diptera:Psychodidae) in a restricted focus of cutaneous leishmaniasis in northern Venezuela. III. Seasonal fluctuation

A one year-long study (March 1979-March 1980) was carried out at San Esteban, an endemic focus of cutaneous leishmaniasis in Northern Venezuela, with the aim of observing the seasonal fluctuation of the local phlebotomine sandflies species. The influence of climatic factors (temperature, relative humidity and rainfall) on population dynamics was analyzed in three collecting sites--a house, a peridomestic area and a sylvatic region. Among anthropophilic species, L. panamensis behaved as a wetseason species, the mean minimum relative humidity being the critical factor influencing the total number of individuals. When the population density of this fly decreased, it was successfully replaced by L. ovallesi, a dry-season species. On the other hand, seasonal variations of L. gomezi were more strongly affected by the temperature.     

Phlebotomine sandflies associated with a focus of cutaneous leishmaniasis in Valle del Cauca, Colombia

Abstract. A survey was made of the phlebotomine sandfly fauna of La Guaira, a village with coffee plantations near Cali, Colombia, from which cases of American cutaneous leishmaniasis had been reported due to Leishmania (Viannia) panamensis and Le. ( V. ) braziliensis. Among six species of sandfly collected on human bait, Lutzomyia youngi was most important in terms of biting nuisance. Lu. columbiana, Lu. lichyi and Lu. scorzai as well as Lu. youngi adults occurred throughout the year. Sandfly man-biting activity occurred throughout the night and was highest within 2 h of sunset. Despite its abundance in nocturnal samples, Lu. youngi was rarely taken in diurnal resting site collections. In contrast, Lu. lichyi was collected on tree-trunks during the day in large numbers and was the only species biting in daylight. The implications of these and other findings for leishmaniasis control measures in La Guaira are considered.     

Ootaxonomic investigation of five Lutzomyia species (Diptera, Psychodidae) from Venezuela

The eggshell fine structure of five sand fly species from Venezuela belonging to the genus Lutzomyia (L. migonei, L. ovallesi, L. absonodonta, L. gomezi and L. panamensis) was examined by scanning electron microscopy. The chorionic sculpturing of L. migonei, L. ovallesi, L. absonodonta and L. gomezi was characterized by series of columns arranged in palisade to form sinuous ridges. In inter-ridge areas, the basal layer was covered with fibrous material. The outer chorion of L. panamensis had a pattern known as "mountain- or volcano-like". The morphology of the posterior pole and aeropyle had a common structure in the five species, with some species-specific characters. The eggshell features of the five species are compared with those of other phlebotomine sand flies.     

Contribution to the sand fly fauna (Diptera: Phlebotominae) of Rio Grande do Sul, Brazil and Leishmania (Viannia) infections.

American cutaneous leishmaniasis (ACL) is endemic in the State of Rio Grande do Sul, Brazil. As reports of nearby hospitals suggest, the Parque Estadual do Turvo seems to serve as a source for the disease. During three months from November 1996 to February 1997 we collected, in this park, 2,228 sandflies (10 Lutzomyia species and 2 6species). We applied the polymerase chain reaction to 920 females which belong to the following species: Lutzomyia migonei, Lu. pessoai, Lu. fischeri, Lu. misionensis, Lu. lanei, Lu. neivai, Lu. shannoni, and Lu. monticola, in an attempt to verify natural infection by Leishmania (Viannia), the causative agent of ACL. Le. (Viannia) infections were demonstrated by DNA amplification from two Lu. pessoai and one Lu. misionensis female. Lu. pessoai have been found with leptomonas in the gut believed to be Le. (V.) braziliensis in other endemic areas of northeastern and southeastern Brazil. However, Lu. misionensis has never been found carrying a natural infection of Le. (Viannia).     

Study of an outbreak of cutaneous leishmaniasis in Venezuela. The role of domestic animals

During an outbreak of cutaneous leishmaniasis in a locality (Las Rosas, Cojedes State, Venezuela) previously non-endemic, 12.9% of humans, 7% of dogs and 21.4% of donkeys (Equus asinus) had lesions with parasites. The agent in the three hosts was identified as Leishmania braziliensis, subspecies braziliensis at least in man and donkey. The probable vector was Lutzomyia panamensis. No infection was found in a small sample of wild mammals examined. The outbreak was apparently linked with the importation of donkeys with ulcers, from endemic areas. The authors call attention to the fact that not only in the foci of "uta", but also in areas of the other forms of American cutaneous leishmaniasis, dogs are frequently found infected. They emphasize the necessity of searching for the infection in donkeys and of performing hemocultures and xenodiagnosis with sandflies in human, canine and equine cases, to verify their possible role as sources of infection, and not merely as dead ends in the epidemiological chain of the disease.     

Leishmaniasis vector potential of Lutzomyia spp. in Colombian coffee plantations

Potential vectors of Leishmania braziliensis Vianna were assessed at four study sites in the mountainous Valle del Cauca, western Colombia, from March to June 1989. In an active focus of transmission at 1450 m altitude, a coffee plantation at Versalles, there were high densities of antropophilic phlebotomines: Lutzomyia columbiana (Ritorcelli & Van Ty) and Lu.townsendi (Ortiz), both in the verrucarum species group, and of Lu.pia (Fairchild & Hertig). At a comparable altitude in a forest reserve at Yotoco where leishmaniasis is unknown, Lu.pia was the prevalent species and Lu.townsendi was absent. In two localities at 1150 m altitude, there were plentiful Lu.lichyi (Floch & Abonnenc) plus both species in the verrucarum group, but Lu.pia was absent. One of these localities, a coffee plantation at Villa Hermosa where a leishmaniasis outbreak occurred in 1986, was compared with a leishmaniasis-free, partly wooded nature reserve at Mateguadua. No natural infections of Leishmania were found in a total of 1896 wild-caught female phlebotomines belonging to at least seven species. It remains unclear why Leishmaniasis transmission is associated with coffee plantations in this part of Colombia. Laboratory-bred Lu.lichyi females were invariably autogenous, and blood-seeking females of this species were always parous. Parity rates in wild-caught females of other species were 55% Lu.pia, 24% Lu.columbiana and 14% Lu.townsendi. Female Lutzomyia infected artificially with Le.braziliensis promastigotes developed peripylarian infections. Higher proportions of Lu.townsendi (96%) and Lu.columbiana (78%) became infected but these species developed lower rates of stomodaeal infections (P less than 0.1) than Lu.lichyi (37%) or Lu.pia (44%).(ABSTRACT TRUNCATED AT 250 WORDS)     

Leishmaniasis in Bolivia. II. The involvement of Psychodopygus yucumensis and Psychodopygus llanosmartinsi in the selvatic transmission cycle of Leishmania braziliensis braziliensis in a lowland subandean region

An epidemiological survey of the vectors of cutaneous leishmaniasis ("espúndia" type) was carried out in the Alto Beni region of Bolivia, an area of Andean foothills at the Eastern limit of the Amazonian lowlands. The climate is typical wet tropical (15 degrees S latitude). Anthropophilic phlebotomine sandfly species were sampled at 20 sites, all forested. The importance of species from the Psychodopygus group, already suspected as a vector in the transmission of Leishmania from the braziliensis complex, was confirmed by: the aggressiveness and diversity of the species encountered (83% of catches, nine species), the discovery of a new anthropophilic species, P. yucumensis and the isolation of a strain of Leishmania braziliensis braziliensis indistinguishable from human strains from the same area, from two species, P. llanosmartinsi and P. yucumensis.     

Ecology of sandflies (Diptera: Psychodidae) in a restricted focus of cutaneous leishmaniasis in northern Venezuela. I. Description of the study area, catching methods and species composition

A study on the ecology of phlebotomine sandfly fauna in a restricted focus of cutaneous leishmaniasis in northern Venezuela was undertaken in order to investigate the species responsible for the transmission. The study area and catching methods for phlebotomine sandflies are described. A total of 9,061 females and 1,662 males were collected during a year-term study. 12 species of Lutzomya and 1 species of Brumptomya sp. were identified. Absolute and relative abundance and occurrence for each species were determined. The relative occurrence allowed to distinguish the common species, viz. L. panamensis, L. ovallesi, L. gomezi, L. trinidadensis, L. atroclavata, L. cayennensis, L. shannoni and L. olmeca bicolor from the rare species vis., L. punctigeniculata, L. rangeliana, L. evansi and L. dubitans. General comments on the species composition of the sandfly fauna in this locality are made.     

Entomological surveys of Lutzomyia flaviscutellata and other vectors of cutaneous leishmaniasis in municipalities with records of Leishmania amazonensis within the Bragança region of Pará State,Brazil

In southeast Amazon, Lutzomyia (Nyssomyia) flaviscutellata is the incriminated vector of Leishmania (Leishmania) amazonensis, a causative agent of zoonotic cutaneous leishmaniasis (CL). The optimal methods for surveying Lu. flaviscutellata were investigated in the Bragança region, northeast Pará State, Brazil, selected for the presence of Le. amazonensis. The performances of modified Disney traps and CDC light traps were compared in four ecotopes within and around four village transects during the wet and dry seasons. The physiological age of female sand flies was estimated and natural infection by flagellates was evaluated by dissection. Disney traps were better for detecting the presence of Lu. flaviscutellata, while CDC traps performed well for detecting Lutzomyia (Nyssomyia) antunesi, suspected vector of Leishmania lindenbergi. The former was more abundant during the wet season, when female flies were naturally infected with Le. amazonensis. These findings identified the environments of local transmission. In order to improve surveys of Lu. flaviscutellata as part of integrated epidemiological surveillance of CL, our recommendations include focusing vector surveys with Disney traps on forest fragments where people work, during the seasonal peak of the vector. Further field studies are required to make model‐based predictions of seasonal variations in the vectorial capacity of vector populations.