Spatial and temporal patterns of occurrence of Lutzomyia sand fly species in an endemic area for cutaneous leishmaniasis in the Atlantic Forest region of northeast Brazil

Sand fly populations of different ecological niches in the Amaraji endemic American Cutaneous Leishmaniasis (ACL) focus of the Pernambuco Atlantic Forest region of northeastern Brazil were monitored spatiotemporally. Lutzomyia whitmani was dominant in all niches but occurred in smaller numbers in forested locations. L. whitmani was significantly less seasonal than the other species, being present throughout the year while other species were more abundant between February and April. These results suggest that L. whitmani may potentially be the principal vector of ACL in the region, even though the sand fly fauna was diverse: 88% were L.whitmani and 12% belonged to 11 other species. Two other species, L. complexa (1.3%) and L. migonei (0.8%), considered to be ACL vectors in other regions, were also present. This detailed picture of the sand fly population's abundance and spatiotemporal distribution provides a basis for future modeling studies of forecasting sand fly activity patterns and ACL occurrence.

Seasonal and spatial changes of sand fly species in a canyon in the Carmel Mountains

Altogether, 4,008 sand flies belonging to seven species were collected over a period of one year in the micro-habitats of a single canyon in the Carmel Mountain ridge. The three most abundant were P. arabicus, P. tobbi, and P. simici. Our results suggest that none of the seven sand fly species was indifferent to the heterogeneity of the microenvironment inside the canyon. Apart from the rare P. perfiliewi, which was only collected on the upper part of the south-facing slope, and P. tobbi, which clustered on the north-facing slope, the bulk of the other sand flies were caught on the bottom of the canyon. During the summer, the catches of all sand fly species increased to reach their maximum number in August and September. In April and May, there was lush vegetation and humidity, so species were distributed evenly throughout their habitats. With the onset of summer dryness, the sand flies concentrated in the humid habitats. The rate of concentration was essentially higher for males than for females, and this variation may result from differences in the behavior of the two sexes. During our study, none of the 2,318 dissected female sand flies were positive for Leishmania promastigotes.

Imidacloprid as a potential agent for the systemic control of sand flies

Our goal was to study the effectiveness of the insecticide imidacloprid as a systemic control agent. First, to evaluate the blood-feeding effect, we fed adult female Phlebotomus papatasi with imidacloprid-treated rabbit blood and monitored blood-feeding success and survival. Second, to evaluate the feed-through effectiveness of this insecticide, we fed laboratory rats and sand rats with insecticide-treated food and evaluated the survival of sand fly larvae feeding on rodents' feces. In the blood-feeding experiment, 89.8% mortality was observed with the higher dose (5 mg/ml) and 81.3% with the lower dose (1 mg/ml). In the larvicide experiments, both sand fly species demonstrated a typical dose-response curve with the strongest lethal effect for the 250 ppm samples. Lutzomyia longipalpis larvae, however, were less sensitive. In all experiments, 1(st) instar larvae were more sensitive than the older stages. First instar P. papatasi larvae feeding on sand rat feces passed the larvicidal threshold of 90% mortality at doses higher than 50 ppm. In comparison, in older stages 90% mortality was obtained with a dose of only 250 ppm. Overall, results support the feasibility of imidacloprid as a systemic control agent that takes advantage of the tight ecological association between the reservoir host and the sand fly vector.

Distribution and ecological aspects of sand fly (Diptera: Psychodidae) species in Sri Lanka

Human indigenous cutaneous leishmaniasis caused by Leishmania donovani complex is endemic in Sri Lanka. We performed an entomological survey to determine the distribution of probable vector species. Sand flies were collected in districts in the dry zone, in the wet zone highlands, and in the wet zone coastal belt of Sri Lanka using CDC light traps, sticky traps and cattle-baited net traps during July, 2005. The survey was reconducted in February, 2006. Overall, 584 sand flies belonging to Phlebotomus (266 specimens, 2 species) and Sergentomyia (318 specimens, 8 species) genera were collected. A total of 266 Phlebotomus was identified as P. argentipes (258/266; 97%) and P. stantoni (8/266; 3%) . The identification studies of Sergentomyia specimens showed that there are at least 8 species in Sri Lanka. Higher number of Phlebotomus sand flies (76/266) were caught in the southern part of the country compared to the other parts probably due to different ecological aspects. P. argentipes were widely distributed throughout the island whereas P. stantoni were collected only in four districts. Since P. argentipes is known to be the vector of L. donovani responsible of visceral leishmaniasis in India, this species may be incriminated as the most possible vector of human cutaneous leishmaniasis in Sri Lanka.

Ecology and control of the sand fly vectors of Leishmania donovani in East Africa, with special emphasis on Phlebotomus orientalis

A literature review is provided on the state of knowledge of the ecology and control of the sand fly vectors of Leishmania donovani in East Africa, with a special emphasis on Phlebotomus orientalis. Visceral leishmaniasis caused by L. donovani is a major health problem in several areas in East Africa. Studies conducted in the past 70 years identified P. orientalis Parrot and P. martini Parrot as the principal vectors of L. donovani in Sudan, Ethiopia and Kenya and P. celiae Minter as the secondary vector of the parasite in one focus in Ethiopia. Findings on sand fly fauna and other circumstantial evidence indicate that P. martini is also responsible for transmission of L. donovani in VL endemic foci of Somalia and Uganda. Several studies showed that P. orientalis occupy distinct habitat characterized by black cotton soil and Acacia seyal-Balanites aegyptiaca vegetation, whereas P. martini and P. celiae are associated with termite mounds. Little knowledge exists on effective control measures of sand fly vectors of L. donovani in East Africa. However, recent evidence showed that use of insecticide impregnated bednets and insect repellents may reduce exposure to the bites of P. orientalis.

Seasonal dynamics and altitudinal distributions of sand fly (Diptera: Psychodidae) populations in a cutaneous leishmaniasis endemic area of the Cukurova region of Turkey

This paper presents the results of an entomological survey in an endemic focus of cutaneous leishmaniasis in the Cukurova region of Turkey. A total of 8,927 specimens belonging to eight Phlebotomus and two Sergentomyia species were captured with sticky papers and CDC light traps from 52 stations. Phlebotomus tobbi Adler, was found to be the most abundant species. Sand fly activity started in May and ended in October. Abundance was highest in August. According to the frequency distributions among certain temperature intervals the observed number of individuals was significantly different from the expected values between 22-24° C and 28-30° C. There was no significant correlation between the abundance of sand flies and altitude. However, sand fly species showed great aggregation at the 100-199 m and 200-299 m altitude intervals. The Shannon-Weinner index indicated no difference between the diversity and abundance of sand flies at different altitudes. Diversity and evenness reached maximum values at 500 m. Jaccard's coefficient indicated that similarity was the highest between 0-99 and 300-399, 0-99 and 500-599 and 100-199 and 200-299 m and lowest between 100-199 and 300-399 and 100-199 and 500-599 m.

Studies of phlebotomine sand fly (Diptera: Psychodidae) populations in limestone areas and caves of western Malaysia

Phlebotomine sand flies were collected using CO2 baited CDC light trap in 2000 and 2001 in limestone areas and caves of western Malaysia. A total of 1,548 specimens were collected comprising 18 species from two genera: Phlebotomus (6 spp) and Sergentomyia (12 spp). Phlebotomus major major (38.9%) was the predominant species followed by Sergentomyia perturbans (20.1%), P. stantoni (15.3%) and others. Biting activity of the sand flies at the Gua Senyum caves, Gua Kota Gelanggi, Batu caves and Gua Kelam were observed using the bare leg landing catch (BLC) technique. Four Phlebotomus spp at Gua Senyum were found to bite humans with a unimodal biting peak (between 01:00 and 04:00 AM). At Gua Kota Gelanggi P. major major was observed to bite humans, but at Batu Caves and Gua Kelam no sand flies were observed to bite humans. Sergentomyia spp did not feed on humans even though high numbers were caught in light traps. The populations of phleobotomine sand flies fluctuated, with several peaks especially among P. major major which peaked in December and was low in February and August. Phlebotomus stantoni was abundant throughout 2001. Most species populations were weakly related to rainfall because they inhabited caves.

Phlebotomine sand fly population dynamics in a leishmaniasis endemic peri-urban area in southern Italy

A 2-year survey was carried out from May to November 2008 and 2009 to study the sand fly species composition, its seasonal phenology and density in Apulia region (southern, Italy). The study was conducted in a dog shelter located in a new residential urban district where Leishmania infantum is endemic. Sand flies were collected using sticky traps from May to November, at about 7-day intervals. Temperature and relative humidity were recorded daily. In December 2008, general environmental improvements (e.g., the ground was covered with gravel and the vegetation present inside the cages was removed to facilitate cleaning) were made in the study area. The most diffused species during the whole study period were Phlebotomus perniciosus (2008, n=248, 49.4%; 2009, n=254, 50.6%) followed by Phlebotomus neglectus (2008, n=76, 39.8%; 2009, n=115, 60.2%) and Phlebotomus papatasi (2008, n=5, 50.0%; 2009, n=5, 50.0%). Four specimens of Phlebotomus perfiliewi were collected only in the first year. The number of Sergentomyia minuta specimens collected increased considerably in the second (n=548, 86.2%) in comparison to the first year (n=88, 13.8%). The highest number of phlebotomine sand flies was collected in July and August when a mean temperature from 27.09 to 28.02°C and mean relative humidity from 47.28 to 56.36% were recorded. The variations in phlebotomine sand fly species diversity and abundance recorded in this study were related to climatic and environmental factors. Data here presented confirm that sand flies easily adapt to the urban environments and that the may represent a public health concern for L. infantum and other pathogen transmission also in similar urban environment of southern Europe.

Colonization of Lutzomyia shannoni (Diptera: Psychodidae) utilizing an artificial blood feeding technique

Laboratory colonization of hematophagous insects must include an efficient method of blood feeding, preferably by artificial means. Strict rules for obtaining animal use permits, extensive animal maintenance costs, and indirect anesthesia effects on animal health warrant the development of an artificial membrane feeding technique for sand fly colonization in laboratories. An attempt was made to colonize Lutzomyia shannoni using an artificial blood feeding membrane to replace the use of live animals commonly used for sand fly blood-feeding purposes. Lutzomyia shannoni readily fed through a pig intestine membrane exposed at an angle of 45°. However, it did not feed through a chicken skin membrane. Olfactory attractants were unable to improve blood-feeding efficiency. Plaster of Paris was the most suitable oviposition substrate. Female L. shannoni adults laid no eggs on moist sand substrate. Sand fly adults held in groups of ten or more laid higher numbers of eggs than did individually maintained sand flies. Inclusion of the L. longipalpis oviposition hormone dodecanoic acid or the presence of previously laid eggs did not stimulate L. shannoni oviposition. The average L. shannoni egg, larval, and pupal duration were 9.3, 36.7, and 17.8 days, respectively. The addition of a 20% sugar solution improved adult female longevity. Females survived longer (14.8 days) than males (11.9 days). Lutzomyia shannoni was successfully colonized in the laboratory for up to four generations using this artificial membrane technique.

Seasonal trends and spatial relations between environmental/meteorological factors and leishmaniosis sand fly vector abundances in Central Spain

This paper reports on an entomological survey performed over the period 2006-2008 in Central Spain (mainly in the Madrid province) where canine leishmaniosis (CanL) is endemic. The study area was selected on the grounds of its wide altitude range, which determines both broad climate and vegetation ranges that could affect sand fly distributions. This area was surveyed from NE to SW across its mountain range (Sistema Central) and plateau area using sticky traps mainly on embankments. In 2006 and 2007, 123 sites were sampled (9557 sand flies captured) to establish possible relations between environmental or meteorological factors and vector densities (Phlebotomus perniciosus and Phlebotomus ariasi). The factors correlated with higher vector densities were: a sample site between villages or at the edge of a village, the lack of a paved road, a rural habitat, an east or south-facing wall or wall sheltered from the wind, the presence of livestock or birds, a holm-oak wood vegetation, a lower summer mean temperature and lower annual mean precipitation. This study was followed by a seasonal survey conducted at 16 selected sites (14,353 sand flies) sampled them monthly from May to November 2008. P. perniciosus showed a diphasic seasonal trend with two abundance peaks in July and September whereas P. ariasi showed a monophasic trend with one peak in August. Comparing with data from studies performed in 1991 in the same area, vector densities are significantly higher. A possible explanation for this is that the vectors (mainly P. ariasi) are moving towards higher altitudes perhaps because of global change. This increasing trend could have an impact on CanL and its geographical distribution.

Comparative study of kala-azar vector control measures in eastern Nepal

This study was conducted to explore the most effective vector control tool among indoor residual spraying (IRS), long lasting insecticidal nets (LLINs) and ecological vector management (EVM) as a part of the regional visceral leishmaniasis elimination initiative. Alpha-cypermethrin as IRS, PermaNet as LLINs and plastering the inner walls of houses with lime as EVM were the interventions. One baseline and three follow-up entomological surveys were carried out in all arms using CDC miniature light traps (LT) and mouth aspirators. Comparisons were made between intervention arms and control arms with pre-intervention and post-intervention vector densities. Light traps were found more efficient in the collection of Phlebotomus argentipes in comparison with aspiration. Vector densities were significantly low in both IRS arm (p=0.009 in LT and p<0.001 in aspirator collections) and LLIN arm (p=0.019 in LT and p=0.023 in aspirator collections) in comparison with control arm. However, in EVM arm, there was no significant difference in P. argentipes sand fly density in comparison with control arm (p=0.785) in LT collections in follow-up surveys. Hence, IRS was found most effective control measure to decrease vector density. LLINs were also found effective and can be considered as a promising alternative vector control tool in VL elimination initiative.

Effect of fruit and leaves of Meliaceae plants (Azadirachta indica and Melia azedarach) on the development of Lutzomyia longipalpis larvae (Diptera: Psychodidae: Phlebotominae) under experimental conditions

This no-choice, laboratory study focuses on the feeding of dried, ground, homogeneous powdered, unprocessed fruit and leaves of Azadirachta indica and Melia azedarach to Lutzomyia longipalpis larvae to determine the effects on their mortality and metamorphosis. A. indica and M. azedarach fruit and leaves significantly increased larval mortality in comparison to larvae fed the untreated, standard diet. A. indica fruit and leaves blocked the molting of the larvae to the fourth instar, resulting in them remaining as third instars until the end of the experiment. M. azedarach fruit also blocked the molting of larvae, which remained permanently in the fourth instar. Feeding M. azedarach leaves resulted in greater molt inhibition. All insects in this group stopped their development as second-instar larvae. No antifeedant effect was detected for any experimental treatment. The results indicate that nontoxic, unprocessed materials obtained from A. indica and M. azedarach are potent development inhibitors of L. longipalpis larvae.

Life cycle differences among Brazilian sandflies of the Lutzomyia longipalpis sibling species complex

The developmental cycles of five Brazilian populations of the Lutzomyia longipalpis Lutz & Neiva species complex (Diptera: Psychodidae) were compared under laboratory conditions. Three of the populations were derived from insects collected in allopatric sites at Natal (Rio Grande do Norte State), Jacobina (Bahia State) and Lapinha Cave (Minas Gerais State). The other two originated from Sobral (Ceará State), where the males of two sympatric species can be distinguished by the presence of one (1S) or two (2S) pairs of abdominal spots. The results of the present study clearly show that all three populations whose males produce C16 pheromones and use pulse-type copulation songs (Jacobina, Lapinha Cave and Sobral 1S) are more easily adapted to the colonization conditions used in our laboratory, producing larger egg batches, with higher survival and an overall faster developmental cycle. This contrasts with populations producing C20 male pheromones and using burst-type copulation songs (Natal and Sobral 2S) that produce smaller egg batches, have higher oviposition mortality and a slower rate of development under identical laboratory conditions. In conclusion, these phenological differences are a further indication of the differentiation of the siblings within the Lu. longipalpis species complex.

Knowledge about sandflies in relation to public and domestic control activities of kala-azar in rural endemic areas of Bihar

Visceral Leishmaniasis (VL) control is a global cause of concern. To identify the gaps in People's knowledge/awareness about sand flies and control activities of kala-azar in rural endemic areas of Bihar, this study consisting of 450 respondents with 288 male and 162 female was carried out. The result showed that 95% respondents had heard about the disease up to some extent, but majority respondents were neither aware about the vector of kala-azar, nor they had any idea about transmission of the disease. About 61% had wrong impression that mosquitoes were causing kala-azar. Regarding knowledge about breeding and resting sites of vectors, 20% reported cattle shed, 16% crevices in the household followed by 15% damp dark places. The attitude of respondents towards vector control programme was poor, as 99% lost faith in the DDT spraying because of ineffectiveness, like no reduction in mosquito nuisance. Bed net was considered the best protection method against sand fly or mosquito nuisance but the cost was considered the major constraint in its use. Proper health education programme in Simple and local language along with visual demonstration should be promoted to enhance the awareness and co-operation at community level.

Survival, population size, and gonotrophic cycle duration of Nyssomyia neivai (Diptera: Psychodidae) at an endemic area of American cutaneous leishmaniasis in southeastern Brazil

The survival, absolute population size, gonotrophic cycle duration, and temporal and spatial abundance of Nyssomyia neivai (Pinto) were studied in a rural area endemic for American cutaneous leishmaniasis (ACL) in Conchal, São Paulo State, southeastern Brazil, using mark-release-recapture techniques and by monitoring population fluctuation. The monthly abundance exhibited a unimodal pattern, with forest and domicile habitats having the highest relative abundances. A total of 1,873 males and 3,557 females were marked and released during the six experiments, of which 4.1-13.0% of males and 4.1-11.8% of females were recaptured. Daily survivorship estimated from the decline in recaptures per day was 0.681 for males and 0.667 for females. Gonotrophic cycle duration was estimated to be 4.0 d. Absolute population size was calculated using the Lincoln Index and ranged from 861 to 4,612 males and from 2,187 to 19,739 females. The low proportion of females that reach the age when they are potentially infective suggests that N. neivai has a low biological capacity to serve as a vector and that factors such as high biting rates and opportunistic feeding behavior would be needed to enable Leishmania (Viannia) braziliensis Vianna transmission. This agreed with the epidemiological pattern of ACL in southeastern Brazil that is characterized by low incidence, with isolated cases acquired principally within domiciliary habitats.

Leishmaniasis emergence and climate change

Spatio-temporal modelling of the distributions of the leishmaniases and their sandfly vectors is reviewed in relation to climate change. Many leishmaniases are rural zoonoses, and so there is a foundation of descriptive ecology and qualitative risk assessment. Dogs are widespread reservoir hosts of veterinary importance. Recent statistical modelling has not always produced novel general conclusions, exemplifying the difficulty of applying models outside the original geographical region. Case studies are given for transmission cycles involving both cutaneous and visceral leishmaniasis in the Old World and the Americas. An important challenge is to integrate statistical spatial models based mainly on climate with more explanatory biological models. Ecological niche models pose difficulties because of the number of assumptions. A positive association has been reported between the El Niño cycle and the annual incidence of visceral leishmaniasis in Brazil, but more basic research is needed before tackling other climate-change scenarios, including leishmaniasis emergence in northern Europe.

Gene silencing in phlebotomine sand flies: Xanthine dehydrogenase knock down by dsRNA microinjections

Lutzomyia longipalpis are vectors of medically important visceral leishmaniasis in South America. Blood-fed adult females digest large amounts of protein, and xanthine dehydrogenase is thought to be a key enzyme involved in protein catabolism through the production of urate. Large amounts of heme are also released during digestion with potentially damaging consequences, as heme can generate oxygen radicals that damage lipids, proteins and nucleic acids. However, urate is an antioxidant that may prevent such oxidative damage produced by heme. We investigated xanthine dehydrogenase by developing the RNAi technique for sand flies and used this technique to knock down the Lu. longipalpis xanthine dehydrogenase gene to evaluate its role in survival of adult females after blood feeding. The gene sequence of Lu. longipalpis xanthine dehydrogenase is described together with expression in different life cycle stages and RNAi knock down. Semi-quantitative RT-PCR of xanthine dehydrogenase expression showed a significant increase in expression after bloodmeal ingestion. Microinjection of dsRNA via the thorax of 1-day-old adult female sand flies resulted in approximately 40% reduction of xanthine dehydrogenase gene expression in comparison to flies injected with a control dsRNA. A significant reduction of urate in the whole body and excretions of Lu. longipalpis was observed after dsRNA xanthine dehydrogenase microinjection and feeding 96h later on rabbit blood. Sand flies injected with XDH dsRNA also exhibit significantly reduced life span in comparison with the mock-injected group when fed on sucrose or when rabbit blood fed, showing that urate could be indeed an important free radical scavenger in Lu. longipalpis. The demonstration of xanthine dehydrogenase knock down by dsRNA microinjection, low mortality of microinjected insects and the successful bloodfeeding of injected insects demonstrated the utility of RNAi as a tool for functional analysis of genes in phlebotomine sand flies.

Entomological survey of phlebotomine sand flies (Diptera: Psychodidae) in a focus of visceral leishmaniasis in central Iran

BACKGROUND & OBJECTIVES

Visceral leishmaniasis (VL) is a major vector-borne disease in Iran. A focus of VL is present in Shahreza county, Isfahan province, central Iran. The main objective of this study was to determine the probable vectors in this area.

METHODS

Sand flies were collected biweekly using sticky paper traps, CDC light-traps, and aspirators from outdoors as well as indoors. All female sand flies were dissected and identified. Promastigotes were inoculated to hamsters and detected by Nested PCR. Approximately 7528 sand flies representing 12 species were collected from April 2003 to October 2004. Phlebotomus (Phlebotomus) papatasi Scopoli, Phlebotomus (Larroussious) major Annandale and Sergentomyia (Sergentomyia) sintoni Pringle were the predominant species. Two percent of P. major was found with natural promastigote infections.

INTERPRETATION & CONCLUSION

This is the first report of natural promastigote infection in P. major in central Iran. The activity of P. major started from April and ended in October with a peak in September. The parasites were identified as Leishmania infantum using standard PCR. P. major is a possible vector of leishmaniasis and is susceptible to DDT in this area.

Seasonal variation of cave-dwelling phlebotomine sandflies (Diptera:Psychodidae) in Phra Phothisat Cave, Saraburi Province, Thailand

Phlebotomine sandflies are widely distributed in Thailand. In view of recent occurrence of indigenous cases of leishmaniasis in Thailand, a bionomic study of sandflies was undertaken in Phra Phothisat cave, Saraburi Province, Thailand from August 2005 to July 2006. The insects were collected monthly by CDC light traps between 06:00 PM and 06:00 AM. They were preserved in 80% alcohol and mounted with Hoyer's medium for species identification. A total of 5,514 sandflies were collected with a female:male ratio of 2.5:1. The collected sandflies belong to 13 species in the genera Phlebotomus and Sergentomyia, namely S. silvatica (43.5%), S. anodontis (31.5%), S. dentata (15.3%), S. barraudi (3.3%), P. argentipes (2.0%), P. philippinensis gouldi (1.0%), P. stantoni (0.5%), S. gemmea (0.5%), P. major major (0.1%), S. perturbans (0.1%), S. iyengari (0.1%), S. bailyi (0.1%), and P. teshi (0.1%). The results revealed seasonal variation in sandflies with the highest peak in July (436 sandflies/trap-night). Some of the sandflies could not be identified and were assumed to be new species. Soil samples inside the cave were analyzed for chemical characteristics. The soil was characterized by moderate acidity (pH 5.8) with various amount of chemicals and nutrients.

Evaluation of novaluron as a feed-through insecticide for control of immature sand flies (Diptera: Psychodidae)

The development and survival of sand fly Phlebotomus papatasi Scopoli (Diptera: Psychodidae) larvae fed feces of Syrian hamsters, Mesocricetus auratus, that had been fed a diet containing novaluron were evaluated. In total, six larval diets were used in sand fly larval bioassays. Four groups of larvae were fed feces of hamsters that had been maintained on a diet containing either 0, 9.88, 98.8, or 988 ppm novaluron. Two additional groups were fed a larval diet composed of equal parts composted rabbit feces and rabbit chow containing either 0 or 988 ppm novaluron. No pupation, hence no adult emergence, occurred when larvae were fed feces of hamsters that were fed diets containing novaluron. The mortality of sand flies fed feces of treated hamsters occurred during larval molts. The results of this study suggest that a control strategy using rodent baits containing novaluron to control phlebotomine sand flies and zoonotic cutaneous leishmaniasis may be possible.

Mapping the main Leishmania phlebotomine vector in the endemic focus of the Mt. Vesuvius in southern Italy

Geographical information systems and remote sensing were used to analyze the distribution of the Leishmania infantum-Phlebotomus perniciosus parasite-vector system in relation to environmental features of two opposite sides (coastal and Apennine) of Mt. Vesuvius, an area of intense transmission of human and canine leishmaniasis in southern Italy. Weekly phlebotomine collections were carried out during two consecutive warm seasons (2004- 2005) in 24 and 25 sites of the coastal and Apennine sides, respectively. Sandflies were caught using over one-thousand and seven hundred 20 x 20 cm-sticky traps placed in different environments. A total of 873 sandflies were collected, of which 284 (32.5%) were identified as P. perniciosus. The cumulative density (number of specimens/m2 of sticky trap/two nights) of this vector species was 3.9. P. perniciosus was significantly more abundant in the coastal side (5.8) as compared to the Apennine side (1.4). The main environmental differences between the two sides were the aspect (south-west for the coastal and north-east for the Apennine side) and land use. The predominance of green vegetated environments (forest, semi-natural and agricultural areas) in the coastal side, in contrast with the predominance of artificial surfaces (namely urban environment) in the Apennine side, could be responsible for the different P. perniciosus densities between the two surveyed areas.

Ecological niche modeling for visceral leishmaniasis in the state of Bahia, Brazil, using genetic algorithm for rule-set prediction and growing degree day-water budget analysis

Two predictive models were developed within a geographic information system using Genetic Algorithm Rule-Set Prediction (GARP) and the growing degree day (GDD)-water budget (WB) concept to predict the distribution and potential risk of visceral leishmaniasis (VL) in the State of Bahia, Brazil. The objective was to define the environmental suitability of the disease as well as to obtain a deeper understanding of the eco-epidemiology of VL by associating environmental and climatic variables with disease prevalence. Both the GARP model and the GDDWB model, using different analysis approaches and with the same human prevalence database, predicted similar distribution and abundance patterns for the Lutzomyia longipalpis-Leishmania chagasi system in Bahia. High and moderate prevalence sites for VL were significantly related to areas of high and moderate risk prediction by: (i) the area predicted by the GARP model, depending on the number of pixels that overlapped among eleven annual model years, and (ii) the number of potential generations per year that could be completed by the Lu. longipalpis-L. chagasi system by GDD-WB analysis. When applied to the ecological zones of Bahia, both the GARP and the GDD-WB prediction models suggest that the highest VL risk is in the interior region of the state, characterized by a semi-arid and hot climate known as Caatinga, while the risk in the Bahia interior forest and the Cerrado ecological regions is lower. The Bahia coastal forest was predicted to be a low-risk area due to the unsuitable conditions for the vector and VL transmission.

Phlebotominae (Diptera: Psychodidae) of human leishmaniosis sites in Tunisia

In order to identify the phlebotomine sandfly populations in Tunisian leishmaniosis foci, an entomological survey was carried out through three entomological seasons (2002-2003-2004) in 19 visceral and cutaneous leishmaniosis areas, located in six bioclimatic zones. Sandfly collections were based on light and sticky traps placed around human leishmaniosis cases. 8,722 phlebotomine sandflies belonging to 12 species were collected. The dominance of subgenus Larroussius species in northern foci, Phlebotomus papatasi in south-western foci and their co-dominance in the centre of the country is in accordance with the distribution of Leishmania infantum and L. major in Tunisia. The low density found in the historical zoonotic cutaneous leishmaniosis focus of Metlaoui in the south-west may indicate the high competence of the local populations. Studied phlebotomine settlements have showed a low specific diversity in most of the studied sites. In L. infantum areas, the dominant species were respectively: P. perfiliewi in the cutaneous leishmaniosis site of the humid bioclimatic stage, P. perniciosus in the cutaneous and visceral leishmaniosis foci of semi-arid and arid bioclimatic stages and P. longicuspis in the visceral leishmaniosis focus of saharan bioclimate. In the zoonotic cutaneous leishmaniosis foci, P. papatasi was a dominant species. In the well-known south-eastern foci of cutaneous leishmaniosis due to L. killicki, P. sergenti was a dominant species with P. perniciosus. In the central emerging foci of L. killicki, P. perniciosus was a dominant species in some sites whereas it was very rare in others. In these sites, the subgenus Paraphlebotomus was always present with a higher abundance of P. alexandri than P. sergenti.

Effects of azadirachtin on the development and mortality of Lutzomyia longipalpis larvae (Diptera: Psychodidae: Phlebotominae)

The effects of azadirachtin A added to the standard diet on the development, mortality, and metamorphosis of Lutzomyia longipalpis Lutz & Neiva, 1912 were studied. Concentrations of 0.1, 1.0, and 10.0 microg of azadirachtin/mg of diet significantly increased larval mortality in comparison with nontreated insects. Concentrations 0.1 and 1.0 microg blocked the molt of larvae, which remained as third instars until the end of the experiment. The 10 microg/mg concentration resulted in greater molt inhibition. In this group, all insects stopped their development as second instars. Simultaneous addition of ecdysone (1 microg/mg) to the standard diet containing azadirachtin counteracted the effects of azadirachtin on mortality and inhibition of ecdysis. These results indicate that azadirachtin is a potent growth inhibitor of L. longipalpis.

Comparative biology of two populations of Lutzomyia umbratilis (Diptera: Psychodidae) of Central Amazonia, Brazil, under laboratory conditions

Lutzomyia umbratilis is the main vector of cutaneous leishmaniasis due to Leishmania guyanensis in northern South America. It has been found naturally infected with this species of Leishmania only east of the Rio Negro and north of the Rio Amazonas. However, populations of this sand fly species are also present in areas south of the Amazon river system, which may act as a geographical barrier to the Leishmania guyanensis cycle. With the aim of looking for possible biological differences between populations of L. umbratilis from each side of this river system, their biology in the laboratory was investigated. Progenitors collected on tree bases in Manaus and Manacapuru (east and west, respectively, of the Rio Negro) were reared in the laboratory. Results from observations of the life cycle, fecundity, fertility, and adult longevity at 27 degrees C and 92% RH were analyzed by descriptive statistics and z, t, U, and chi2 tests. Although the Manaus and Manacapuru colonies showed a longer developmental time than most Lutzomyia species reared at similar temperatures, length of time of egg and 4th instar larva of the two populations differed significantly (p < 0.01). Females of the latter retained significantly (p < 0.001) less mature oocytes, and the general productivity (% adults from a known number of eggs) of the colony was significantly (p < 0.01) higher than that of the former. These results show that the L. umbratilis population of Manaus is more productive, and thus a better candidate for future mass-rearing attempts. The two populations differ in their life cycle, fecundity, fertility, adult longevity, and emergence. These differences may reflect some divergence of intrinsic biological features evolved as a result of their geographical isolation by the Rio Negro. It is expected that further investigations on morphometry, cuticular hydrocarbon, isoenzyme, molecular and chromossomal analyses, infection, and cross-mating experiments with these and other allopatric populations of both margins of the Amazon river system will help reveal whether or not L. umbratilis has genetically diverged into two or more reproductively isolated populations of vectors or non-vectors of Leishmania guyanensis.