Effect of mouse antisera targeting the Phlebotomus papatasi midgut chitinase PpChit1 on sandfly physiology and fitness

In sandflies, the absence of the peritrophic matrix (PM) affects the rate of blood digestion. Also, the kinetics of PM secretion varies according to species. We previously characterised PpChit1, a midgut-specific chitinase secreted in Phlebotomus papatasi (PPIS) that is involved in the maturation of the PM and showed that antibodies against PpChit1 reduce the chitinolytic activity in the midgut of several sandfly species. Here, sandflies were fed on red blood cells reconstituted with naïve or anti-PpChit1 sera and assessed for fitness parameters that included blood digestion, oviposition onset, number of eggs laid, egg bouts, average number of eggs per bout and survival. In PPIS, anti-PpChit1 led to a one-day delay in the onset of egg laying, with flies surviving three days longer compared to the control group. Anti-PpChit1 also had a negative effect on overall ability of flies to lay eggs, as several gravid females from all three species were unable to lay any eggs despite having lived longer than control flies. Whereas the longer survival might be associated with improved haeme scavenging ability by the PM, the inability of females to lay eggs is possibly linked to changes in PM permeability affecting nutrient absorption.

A comparative evaluation of end-emic and non-endemic region of visceral leishmaniasis (Kala-azar) in India with ground survey and space technology

In visceral leishmaniasis, phlebotomine vectors are targets for control measures. Understanding the ecosystem of the vectors is a prerequisite for creating these control measures. This study endeavours to delineate the suitable locations of Phlebotomus argentipes with relation to environmental characteristics between endemic and non-endemic districts in India. A cross-sectional survey was conducted on 25 villages in each district. Environmental data were obtained through remote sensing images and vector density was measured using a CDC light trap. Simple linear regression analysis was used to measure the association between climatic parameters and vector density. Using factor analysis, the relationship between land cover classes and P. argentipes density among the villages in both districts was investigated. The results of the regression analysis indicated that indoor temperature and relative humidity are the best predictors for P. argentipes distribution. Factor analysis confirmed breeding preferences for P. argentipes by landscape element. Minimum Normalised Difference Vegetation Index, marshy land and orchard/settlement produced high loading in an endemic region, whereas water bodies and dense forest were preferred in non-endemic sites. Soil properties between the two districts were studied and indicated that soil pH and moisture content is higher in endemic sites compared to non-endemic sites. The present study should be utilised to make critical decisions for vector surveillance and controlling Kala-azar disease vectors.

Effect of untreated bed nets on blood-fed Phlebotomus argentipes in kala-azar endemic foci in Nepal and India

Observational studies in the Indian subcontinent have shown that untreated nets may be protective against visceral leishmaniasis (VL). In this study, we evaluated the effect of untreated nets on the blood feeding rates of Phlebotomus argentipes as well as the human blood index (HBI) in VL endemic villages in India and Nepal. The study had a "before and after intervention" design in 58 households in six clusters. The use of untreated nets reduced the blood feeding rate by 85 percent (95 percent CI 76.5-91.1 percent) and the HBI by 42.2 percent (95 percent CI 11.1-62.5 percent). These results provide circumstantial evidence that untreated nets may provide some degree of personal protection against sand fly bites.

Proven and putative vectors of American cutaneous leishmaniasis in Brazil: aspects of their biology and vectorial competence

The aim of the present review is to give relevant information on aspects of the biology and ecology, including the vectorial competence of Lutzomyia sand fly species suggested as vectors of American cutaneous leishmaniasis in Brazil. The disease, due to Leishmania (Viannia) braziliensis, has been registered in most municipalities in all the Brazilian states and its transmission is associated with more than one sand fly species in each geographical region. A variety of Leishmania species can be found in the Amazon basin, where different epidemiological chains have been detected with the participation of different phlebotomine vectors. Finally, a discussion is presented on some sand fly species found naturally infected by Leishmania, but for which there is as yet no evidence regarding their epidemiological importance.

Preferência alimentar sanguínea de flebotomíneos da Amazônia do Maranhão, Brasil / Feeding preference of sand flies in the Amazon, Maranhão State, Brazil

O objetivo deste estudo foi determinar as fontes alimentares sanguíneas de flebotomíneos por meio da reação da precipitina, em Buriticupu, na Amazônia maranhense, Brasil, de julho de 2002 a junho de 2004. Foram detectadas reações simples (87,6 por cento), duplas (8 por cento) e não reagentes (4,4 por cento). A presença de flebotomíneos alimentados com sangue humano (6,7 por cento) e de possíveis reservatórios de Leishmania no peridomicílio ajuda a explicar a ocorrência de casos autóctones de leishmaniose tegumentar no Município de Buriticupu.

The objective of this study was to determine the blood feeding sources for sand flies based on the precipitin test in Buriticupu, Amazon Region, Maranhão State, Brazil, from July 2002 to June 2004. Single (87.6 percent) and double (8 percent) reactions and non-reactive samples (4.4 percent) were found. The presence of sand flies fed on human blood (6.7 percent) and blood of animals that are possible peridomiciliary Leishmania reservoirs helps explain the reporting of autochthonous tegumentary leishmaniasis cases in Buriticupu.

Transmision de la leishmaniasis tegumentaria en la Argentina / Transmission of tegumentary leishmaniasis in Argentina

La leishmaniasis tegumentaria ha experimentado en Argentina, desde 1985, un incremento de casos totales, de la frecuencia, intensidad y distribución de brotes epidémicos, y de la incidencia relativa en mujeres y en niños. Es necesario caracterizar los nuevas circunstancias de transmisión generadas en las últimas décadas para el diseño de estrategias apropiadas de control. Con dicho objeto, basados en indicadores epidemiológicos, entomológicos y en el análisis cualitativo de imágenes satelitales, se describen cuatro brotes epidémicos tomados como casos de estudio: Urugua-í (2004), Esperanza (1998), Alberdi (2003) y Monteros-Simoca (2004). A partir de dichas descripciones se caracterizaron cuatro ciclos: a) silvestre con transmisión en vegetación primaria o residual; b) silvestre con transmisión eventual peridoméstica por alteración deparches de vegetación residual; c) silvestre con transmisión peridoméstica por contigüidad con vegetación residual; d) peridoméstico en ambientes rurales, periurbano ruralizado o interfase urbano-rural. Todos los brotes epidémicos ocurridos desde 1985 se correspondieron con uno de estos ciclos, demostrando ser hasta el momento una tipificación abarcativa de la transmisión de leishmaniasis tegumentaria en la Argentina. De esta manera se categorizaron cuatro patrones epidémicos en el país, destacando a su vez la utilidad del análisis cualitativo, de datos de terreno e imágenes satelitales, como herramientas para comprender la epidemiología de la enfermedad y poder desarrollar medidas adecuadas de prevención y control.

The total cases of tegumentary leishmaniasis in Argentina increased since 1985, as the frequency, intensity and geographic distribution of the epidemic outbreaks, and the relative incidence in women and children. The characterization of the new scenarios of transmission generated in the last decades is needed for the design of appropriate control measures. With this aim, four outbreaks were described as case studies, based on epidemiological and entomological data together with the qualitative analysis of satellite imaginery: Urugua-í (2004), Esperanza (1998), Alberdi (2003) and Monteros-Simoca (2004). These descriptions allowed to define four scenarios of transmission according to a cycle: a) sylvatic with transmission in primary or residual vegetation; b) sylvatic with eventual peridomestic transmission due to changes within patches of residual vegetation; c) sylvatic with peridomestic transmission in domiciles contiguous with the residual vegetation; and d) peridomestic in rural, ruralized periurban or urban-rural interfase environment. All the epidemic outbreaks since 1985 were consistent with the scenarios characterized here, indicating that the tipification is comprehensive of the transmission of tegumentary leishmaniasis in Argentina up to now. In conclusion, four scenarios of epidemic outbreaks were defined for Argentina, while it is highlighted the qualitative analysis of field and remote sensing data as a tool to understand the epidemiology of the disease, and so to develop adequate measures for prevention and control.

Sexing sand fly pupae (Diptera: Psychodidade: Phlebotominae)

We describe a technique to separate male and female pupae of sand flies. This has reduced the labour to separate flies after emergence and also allows the isolation of unmated adults for behavioural and physiological studies.

Breeding habitats of vector sandflies and their control in India.

In India Phlebotomus argentipes and Phlebotomus papatasi are the proven and suspected vectors of visceral leishmaniasis respectively. In the past, only a few samples from the field yielded sandfly immatures though there were many adults in the vicinity. This might be because of dearth of information on the various factors influencing the oviposition of the gravid females as well as survival and development of immatures. Therefore, available information on these aspects has been reviewed so as to highlight the imperative of undertaking further studies on the ecology of immatures in field conditions.

Redescription of Lutzomyia (Lutzomyia) souzalopesi Martins, Silva & Falcäo, 1970 (Diptera, Psychodidae, Phlebotominae)

Redescribe the male and the female of Lutzomyia (Lutzomyia) souzalopesi Martins, Silva & Falcäo, 1970. Taxonomic remarks, geographic distribution and drawings are presented.

Report on a collection of Lutzomyia sand flies (Diptera: Psychodidae) from the Middle Solimoes (Amazonas, Brazil)

Fifty-two species of Lutzomyia sand flies were identified in contemporaneous samples totalling only 1875 individuals, collected at the same site in tall primary terra-firme rainforest, near the south bank of the Solimoes River. The most abundant species belonged to the subgenera Trichophoromyia and Nyssomyia. The subgenera Psathyromyia, Nyssomyia and Psychodopygus represented the greatest number of species. A new, aberrant species of the subgenus Psathyromyia (L. cutellata) and the female of Lu. souzacastroi are described. The Phlebotominae are proposed as a suitable indicator group for biogeographic and diversity studies.

Response of gravid Phlebotmus papatasi females to an oviposition attractant/stimulant associated with conspecific eggs.

Oviposition response of gravid P. papatasi females to conspecific eggs was studied in laboratory colonized sandflies. It was observed that significantly higher number of eggs were laid in the vicinity of conspecific eggs. However, a certain minimum number of eggs were required to be placed on the substratum to influence the rate of oviposition. The fecundity of females (mean = 56.5 +/- 4.9 eggs) exposed to conspecific eggs was significantly higher (P < 0.05) than that of blank control group. Perhaps, the chemical substances/pheromone of egg origin stimulated the oviposition rate. In an attempt to isolate the active ingredient, solvent washing of the conspecific eggs were tested. No increase in the rate of oviposition was noticed when the test site was treated with distilled water extract, whereas, significantly larger number of eggs were laid at the site treated with di-ethyl ether extract. This indicated that the oviposition attractant associated with the eggs dissolved in the organic solvent, but not in water. The possible application of this attractant for wild sandflies in nature and for regulating the site of oviposition on the substratum in the laboratory colonized sandflies needs to be explored.

Biting rhythm & biting activity of phlebotomid sandflies.

The biting behaviour of Phlebotomid sandflies was studied in a rural village of Pondicherry through all night collections for a period of one year, using human volunteers and cattle as baits. Phlebotomus papatasi was caught only on human bait, showing anthropophily while Ph. argentipes was caught on cattle baits, showing zoophily. The biting activity was seen throughout the night, reaching a peak of 0100 h in Ph. papatasi and 0200 h in Ph. argentipes.

Identification of bloodmeals of phlebotomine sandflies using the agarose gel diffusion method.

The source of blood meal of wild caught Phlebotomid sandflies collected in areas around Pondicherry was identified using an agarose gel diffusion method. A total of 497 blood samples obtained from freshly engorged Phlebotomid sandflies were tested. Of these 66.8% were positive to human antisera, 29.2% to bovine antisera and the remaining 4.0% to avain antisera. The human blood indices of P. papatasi and P. argentipes were 0.91 and 0.04, respectively.

Seasonal abundance, natural survival & resting behaviour of Phlebotomus papatasi (Diptera: Phlebotomidae) in Pondicherry.

A study was carried out on the seasonal abundance, natural survival and resting behaviour of Ph. papatasi in four ecologically different areas of Pondicherry. The average indoor resting density ranged from 2.25 (May 1989) to 16.70/man hour (October 1989). Ph. papatasi was observed to be predominantly endophilic in its resting behaviour. A significant positive correlation was observed between rainfall and relative density. The daily survival of adult population ranged from 0.893 to 0.949 and showed significant positive correlation with relative humidity. Examination of the abdomen of indoor resting females showed that the entire period of gonotrophic cycle was spent indoors.

Longitudinal study on distribution of Phlebotomus argentipes sandflies at different heights in cattleshed.

Distribution of Ph. argentipes at three levels (level I, 0-0.91 m; level II, 0.91-1.82 m; and level III 1.82-2.74 m) above the ground in 6 cattlesheds was studied during July 1989 to June 1990. Of the 8044 Ph. argentipes caught, 3151 (39.2%), 3936 (48.9%) and 957 (11.9%) were from levels I, II, and III respectively. Both male and fed, half-fed, gravid and unfed female sandflies were found at all the three levels and in all the three seasons viz., rainy, winter and summer, of the year. The maximum height of occurrence of sandflies was 2.51 m (8.3 ft) above the ground level.

Blood meal analysis of Phlebotomus argentipes in eight districts of West Bengal.

Eight districts of West Bengal (India) were surveyed for the biting habit of Phlebotomus argentipes using agar gel diffusion method. Blood meal indices were found different in the two biotopes, human dwellings and cowsheds. A total of 395 blood meals were analyzed. The blood meal indices in the human dwellings were human 68.8 per cent, cow 38.9 per cent, both human and cow 10.2 per cent, others 2.5 per cent and in the cowsheds: human 19.7 per cent, cow 91.6 per cent, human and cow 13.9 per cent and others 2.5 per cent. These indicated that P. argentipes did not show preference to any blood meal.

Epidemiologia de la leishmaniasis tegumentaria en merida, Venezuela. I. Diversidade y dispersion de especies flebotominas en tres pisos altitudinales y su possible rôle en la transmission de enfermedad

Como parte de un estudio epidemiológico sobre leishmaniasis en el Estado Mérida, Venezuela, se presenta la diversidad y dispersión de las especies flebotominas identificadas en 15 localidades ubicadas en 3 pisos altitudinales entre los 175 y los 1.960 m.s.n.m. De 7.126 espécimes capturados (5.132 hombres y 1.994 femenino) se registran 24 especies de Lutzomyia, reconociéndose 10 de las llmadas antropofílicas. Se detalla la distribución de las especies en cada piso altitudinal y en el domicilio humano, el peridomicilio y el ambiente silvestre. Se discute el posible papel que juegan las diferentes especies en la transmisión de la leishmaniasis tegumentaria en cada piso altitudinal en particular y en la región andino-venezolana, en general