Biology of Phlebotomus papatasi (Diptera: Psychodidae) in the laboratory

Details on the productivity and developmental times of a colony of Phlebotomus papatasi Scopoli (Diptera: Psychodidae) over 14 generations are reported and compared with findings of previous studies. The average productivity (percentage of eggs laid that were reared to adults) over six generations at 26-27 and at 29 -30 degrees C was 44.08 and 59.53%, respectively. The maximum productivity was 69.5%. The average developmental time over six generations at 26-27 and at 29 -30 degrees C was 35 and 26 d, respectively. The minimum developmental time from egg to adults was 25 d. The Tunisian strain of P. papatasi can reproduce autogenously or anautogenously, depending on the availability of a suitable bloodmeal source.     

Morphological and anatomical variations among Phlebotomus (Phlebotomus) papatasi sensu lato (Diptera: Psychodidae)

Phlebotomus (Phlebotomus) papatasi (Scopoli) collected in human dwellings from an agricultural villages Chaura, located in Gaya district, Bihar, India, showed morphological and anatomical variations. Male sand flies of this species exhibited variations in the genital structures, while females showed differences in the spermathecae and antenna segment three (A3). When the mitochondrial DNA of both male and female P. (P.) papatasi sensu lato population subjected to DNA barcoding, both the sexes of P. (P.) papatasi variants were found to be associated. The differences in the morphometric characteristics clearly constitutes preliminary evidence for infraspecific variation in P. (P.) papatasi s.1. population in India.     

Effect of temperature on metabolism of Phlebotomus papatasi (Diptera: Psychodidae)

Phlebotomus papatasi (Scopoli) (Diptera: Psychodidae) is the most important vector of Leishmania major, and previous experiments revealed that Leishmania development in the sand fly midgut is significantly affected by temperature. Therefore, we maintained blood-fed P. papatasi females at 23 or 28 degrees C to understand the effect of temperature on bloodmeal digestion and developmental times of this sand fly. At the lower temperature, the metabolic processes were slower and developmental times were longer: defecation, oviposition, and egg hatch started later and took longer to complete. Also, the mortality of blood-fed females was significantly lower. The defecation of bloodmeal remains was delayed for 12-36 h at 23 degrees C compared with the group maintained at 28 degrees C. Such delay would provide more time for Leishmania to establish the midgut infection and could partially explain the increased susceptibility of P. papatasi to Leishmania major at 23 degrees C. In both experimental groups, blood-fed females laid similar numbers of eggs (mean 60 and 70, maximum 104 and 115 per female). Egg numbers were positively correlated with the amount of hematin excreted in feces of ovipositing females. In parallel experiments, autogeny was recorded in 8% of females. The autogenous egg batches were smaller (mean, 12; range, 1-39), but they all produced viable larvae.     

Photosynthesis modulates the plant feeding of Phlebotomus papatasi (Diptera: Psychodidae)

Phlebotomus papatasi (Scopoli), the vector of Leishmania major (Yakimoff & Schokhor), feeds on plants in desert habitats in the Jordan Valley. At the end of the dry summer, the life span of sand flies is short and the amount of sugars in their guts is small. In this season the plants are under the stress of heat and dehydration. This stress arrests the photosynthesis and decreases the amounts of the main end products, sucrose and starch. We presumed that the paucity of sugars in the sand fly plant tissue diet resulted from the arrest of photosynthesis. To test this assumption, we compared the feeding of sand flies on branches of Capparis spinosa (L.) that had been kept for 24 h in darkness and on branches cut after a normal day of photosynthesis. In darkness, the branches had lost more than half of their sugar content. Afterward they were fed upon overnight by 45.2% of female and 14.3% of male sand flies. A higher proportion of 81.0% females and 38.7% males fed on branches from natural conditions and these fed flies were significantly heavier. Laboratory experiments also showed that plant tissue meals of P. papatasi often include starch grains. Such grains were found also in 50% of field-caught males and females. The nutritive potential of plant tissues was demonstrated by the 33-d median survival of P. papatasi series that had been maintained on fresh C. spinosa branches and water.     

Isoenzymatic characterization of Phlebotomus papatasi (Diptera: Psychodidae) of the Marrakech area, Morocco

This study reports the genetic characterization of urban and rural populations of Phlebotomus (Phlebotomus) papatasi Scopoli (Diptera: Psychodidae) in Marrakech, Morocco. Using isoenzymatic analysis, four Moroccan populations were compared with other Mediterranean basin populations from Spain, Cyprus, and Syria. Morphological anomalies were noted in the male genitalia of 5.3% of the specimens collected from Marrakech area. Qualitative analysis of zymogram profiles revealed nine polymorphic enzymes (HK, PGM, PGI, 6PGD, MDH1, MDH2, ICD2, FUM, and ACO) and three monomorphic enzymes (ME, ICD1, and alphaGPDH). Genetic distances clearly separated the populations of western Mediterranean countries (Morocco and Spain) from eastern countries (Syria and Cyprus), but they could not be used to differentiate between urban and rural populations in Marrakech area.     

Expression of heterologous promoters in Lutzomyia longipalpis and Phlebotomus papatasi (Diptera: Psychodidae) cell lines

To establish a transient expression system for genes introduced into sand fly cell lines, we tested the expression of the luciferase reporter gene under control of different promoters. Towards this end, we lipofected cell lines obtained from New and Old World sand flies, LL-5 from Lutzomyia longipalpis Lutz & Neiva and PP-9 from Phlebotomus papatasi Scopoli, respectively. The relative levels of luciferase expression were studied under control of Drosophila melanogaster Meigen heat shock protein 70 (hsp70), human cytomegalovirus, simian virus 40 or Junonia coenia (Hübner) densovirus (P9) promoters. The Drosophila heat shock protein 70 promoter, originating from insect genes, functioned as a strong promoter in both cell lines. Promoters from the different virus genes also were capable of driving transgene expression in both cell lines.     

Electrophoretic comparison of the Leishmania vectors Phlebotomus papatasi and P. langeroni (Diptera: Psychodidae)

Cellulose acetate electrophoresis was employed to detect 22 different enzyme systems in laboratory-reared populations of the sympatric Leishmania vectors, Phlebotomus papatasi (Scopoli) and P. langeroni Nitzulescu. Electrophoretic conditions sensitive enough to permit as many as eight separate enzyme assays to be performed on individual specimens were developed. Under these conditions, 18 enzymes were detected with high resolution and regularity. Evidence was obtained which suggested that a number of enzymes in both species are under multilocus genetic control. Polymorphism was observed in 14 of 25 (56%) loci detected in P. papatasi and in eight of 24 (33%) loci detected in P. langeroni. Differences in electrophoretic profiles of malic enzyme, 6-phosphogluconate dehydrogenase, and fumarate hydratase were considered to be genetically fixed in both sexes of P. papatasi and P. langeroni. Their detection may permit an accurate and more rapid separation of these vectors in field collections.     

The potential distribution of Phlebotomus papatasi (Diptera: Psychodidae) in Libya based on ecological niche model

The increased cases of cutaneous leishmaniasis vectored by Phlebotomus papatasi (Scopoli) in Libya have driven considerable effort to develop a predictive model for the potential geographical distribution of this disease. We collected adult P. papatasi from 17 sites in Musrata and Yefern regions of Libya using four different attraction traps. Our trap results and literature records describing the distribution of P. papatasi were incorporated into a MaxEnt algorithm prediction model that used 22 environmental variables. The model showed a high performance (AUC = 0.992 and 0.990 for training and test data, respectively). High suitability for P. papatasi was predicted to be largely confined to the coast at altitudes <600 m. Regions south of 300 degrees N latitude were calculated as unsuitable for this species. Jackknife analysis identified precipitation as having the most significant predictive power, while temperature and elevation variables were less influential. The National Leishmaniasis Control Program in Libya may find this information useful in their efforts to control zoonotic cutaneous leishmaniasis. Existing records are strongly biased toward a few geographical regions, and therefore, further sand fly collections are warranted that should include documentation of such factors as soil texture and humidity, land cover, and normalized difference vegetation index (NDVI) data to increase the model's predictive power.     

Behavioral evidence for the presence of a sex pheromone in male Phlebotomus papatasi scopoli (Diptera: Psychodidae)

Phlebotomus papatasi (Diptera: Psychodidae) is the Old World sand fly vector of zoonotic cutaneous leishmaniasis caused by Leishmania major (Trypanosomatidae: Kinetoplastida), a debilitating and disfiguring protist parasitic disease prevalent throughout southern Mediterranean countries, the Middle East, as well as southern and eastern European countries, where it is regarded as a serious public health problem. Little is known of the mating ecology of P. papatasi, and, in particular, the role (if any) of pheromones is not known. In this laboratory- and field-based study, we have shown that a male-produced sex pheromone exists in P. papatasi. Young female P. papatasi are attracted to the headspace volatiles of small groups of males, males and females together, but not females alone. Males were not attracted to males, females, or mixed groups of males and females in the laboratory. Larger groups of males or males and females together were repellent in the laboratory study. Field experiments showed that Centers for Disease Control (CDC) light traps baited with small groups of males and females together were attractive to females, but not males. CDC traps baited with large groups of males and females together caught significantly fewer females and males than the control traps; however, the proportion of females caught compared with males overall was much higher than with CDC traps baited with small numbers of males and females. These results suggest that females may be attracted in preference to males to the vicinity of the baited traps and are highly sensitive to the concentration of male pheromone. It also suggests that P. papatasi mating behavior is fundamentally different from that of Lutzomyia longipalpis, where large mating aggregations of males and females occur.     

Enzyme electrophoresis as an alternative method for separating the sympatric Leishmania vectors Phlebotomus papatasi and Phlebotomus langeroni (Diptera: Psychodidae)

Trials were conducted to determine the accuracy of separating the sympatric sand fly species Phlebotomus papatasi (Scopoli) and P. langeroni Nitzulescu by means of cellulose acetate enzyme electrophoresis. Malic enzyme, phosphoglucomutase, 6-phosphogluconate dehydrogenase, and fumarate hydratase were each evaluated in laboratory-reared and field-collected populations of the two species. Each of the four enzyme-based identifications was highly sensitive (greater than 97%) and specific (greater than 93%). Identifications based upon fumarate hydratase were in perfect agreement with morphological identifications, and evidence was obtained which indicates that this enzyme may be the most stable of the four enzymes tested. The application of enzyme-based vector identification is discussed in relation to classical and novel survey procedures for Leishmania promastigote detection in sand flies.     

Laboratory transmission of Rift Valley fever virus by Phlebotomus duboscqi, Phlebotomus papatasi, Phlebotomus sergenti, and Sergentomyia schwetzi (Diptera: Psychodidae)

We examined the potential for Phlebotomus papatasi (Scopoli), Phlebotomus duboscqi (Neveu-Lemarie), Phlebotomus sergenti (Parrot), and Sergentomyia schwetzi (Adler, Theodor, & Parrot) to transmit Rift Valley fever (RVF) virus. After feeding on hamsters that had been inoculated with RVF virus, P. papatasi, P. sergenti, and S. schwetzi became infected and developed disseminated infections. All P. papatasi and P. duboscqi inoculated with RVF virus developed high-titer infections. In contrast, only 41% of the inoculated S. schwetzi contained detectable virus, and infected individuals contained significantly less virus than the two Phlebotomus species. Although 50% of the inoculated P. duboscqi transmitted RVF virus to hamsters, only 14% of P. papatasi and none of the S. schwetzi transmitted this virus. Additional studies are needed to determine the role of sand flies as vectors of RVF virus.     

Development of Leishmania major in the phlebotomine sandflies, Phlebotomus papatasi (Scopoli) and Phlebotomus langeroni (Nitzulescu)

Laboratory bred Phlebolomus papatasi and P. langeroni were examined for their susceptibility to develop Leishmania major promastigotes under laboratory conditions. Promastigotes were demonstrated in the gut of both species when they were given sugar 24 hr before or after an infective blood meal and in flies offered only an infective blood. The overall infection rate was slightly higher in P. langeroni than P. papatasi. Head promastigotes were detected in P. papatasi provided with sugar 24 hr before or after an infective blood meal. No head promastigotes were seen in flies offered only infective blood. In P. langeroni, head promastigotes were only seen in flies fed on sugar before or after an infective blood and maintained at 18 degrees C. Results indicate that sugar plays a major role in the migration of parasites from the gut to the head. Temperature may have a marginal effect on the migration process. Attempts to transmit L. major to hamster by the bite of infected P. papatasi were not successful.     

Phenology of Phlebotomus papatasi (Diptera: Psychodidae) relative to the seasonal prevalence of zoonotic cutaneous leishmaniasis in central Tunisia

The population density of Phlebotomus papatasi Scopoli (Diptera: Psychodidae), vector of Leishmania major Yakimoff & Schokhor (Kinetoplastida: Trypanosomatidae), the etiologic agent of zoonotic cutaneous leishmaniasis (ZCL), was assessed May-November 2005 in central Tunisia by using sticky traps. The densities of P. papatasi were found to peak in early spring and again in the autumn. The lowest densities were observed in August. Prevalence of ZCL in the governorate of Sidi Bouzid peaks in December, 3 to 3.5 mo after the fall sand fly population peak, suggesting a close temporal association with the abundance of P. papatasi.