THE PHLEBOTOMINAE OF THE ETHIOPIAN EEGION.1

Molecular detection of Leishmania (Sauroleishmania) adleri (Trypanosomatida: Trypanosomatidae) in Sergentomyia sp. sand flies (Diptera: Psychodidae) in Mali and Niger

Phlebotomine sand flies of the genus Sergentomyia are considered to be of minor importance as vectors of Leishmania parasites pathogenic to humans, but are known to transmit lizard parasites of the subgenus Sauroleishmania, including L. (S.) adleri. However, knowledge on the geographic distribution of Sauroleishmania spp. and the infection rates in the vectors is very limited. Therefore, our study aimed (1) to further elucidate the distribution and prevalence of Sauroleishmania spp. in their respective vectors and (2) to assess the potential risk for occasional transmission of Leishmania parasites to international military personnel deployed in camps in Mali and Niger. A total of 1,482 wild-caught sand flies (Sergentomyia spp. and closely related Grassomyia spp.) were screened by real-time PCR for the presence of Leishmania DNA. Thirty-two sand fly pools were tested positive, with six from Mali and 26 from Niger. The DNA of four representative isolates was sequenced. The resulting sequences revealed a homology to L. adleri, which leads to the first report of this species from Mali and Niger to the best of our knowledge. The results suggest that Sergentomyia (Sintonius) clydei might be the natural sand fly vector, while Grassomyia spp. appear to be refractory. No Leishmania sp. pathogenic to humans was detected in these sand flies.

Ecological site distribution of sand fly species of Mokolo, an endemic focus of cutaneous leishmaniasis in northern Cameroon

Leishmaniasis is a vector borne disease present in two major clinical forms (cutaneous and visceral) in the northern part of Cameroon. The disease is classified as a neglected tropical disease by the World Health Organization and thus, requires more attention. The aim of this study was to correlate the previously established composition and abundance of sand fly fauna with the putative vector status and the ecological behavior in the Mokolo cutaneous leishmaniasis focus to propose fighting strategies integrating vectors control. Over a 12-month period light traps were used for sand flies' collection in urban, peri-urban and sylvatic environment found in Mokolo, an endemic focus of leishmanisis in northern Cameroon, microscope and taxonomic keys were used for their identification. Nineteen (19) species were identified belonging to the genera Sergentomyia, and Phlebotomus. The influence of human population density on sand fly's species density and composition was assessed trough the evaluation of ecological distribution of sand flies in Mokolo. It came out that, Se. coronula and Se. thomsoni mandarai are strictly wild species and Ph. duboscqi, a domestic species. The other species are generalists.The number of Se. antennata and Se. adami decreases with the increase of the density of human population while Se. distincta, Se. vorax and Ph. duboscqi increase with the density of human population in the study site. Based on its previous reports in the Leishmania transmission in West Africa, Ph. duboscqi should still be considered as the main suspected vector in Mokolo. Ph. duboscqi, Se. distincta, Se. affinis ssp. vorax and Se. schwetzi are highly represented around human dwellings.

Afrotropical sand fly-host plant relationships in a leishmaniasis endemic area, Kenya

The bioecology of phlebotomine sand flies is intimately linked to the utilization of environmental resources including plant feeding. However, plant feeding behavior of sand flies remains largely understudied for Afrotropical species. Here, using a combination of biochemical, molecular, and chemical approaches, we decipher specific plant-feeding associations in field-collected sand flies from a dry ecology endemic for leishmaniasis in Kenya. Cold-anthrone test indicative of recent plant feeding showed that fructose positivity rates were similar in both sand fly sexes and between those sampled indoors and outdoors. Analysis of derived sequences of the ribulose-1,5-bisphosphate carboxylase large subunit gene (rbcL) from fructose-positive specimens implicated mainly Acacia plants in the family Fabaceae (73%) as those readily foraged on by both sexes of Phlebotomus and Sergentomyia. Chemical analysis by high performance liquid chromatography detected fructose as the most common sugar in sand flies and leaves of selected plant species in the Fabaceae family. Analysis of similarities (ANOSIM) of the headspace volatile profiles of selected Fabaceae plants identified benzyl alcohol, (Z)-linalool oxide, (E)-β-ocimene, p-cymene, p-cresol, and m-cresol, as discriminating compounds between the plant volatiles. These results indicate selective sand fly plant feeding and suggest that the discriminating volatile organic compounds could be exploited in attractive toxic sugar- and odor- bait technologies control strategies.

Plant feeding as an essential resource of sand flies, primary vectors of Leishmania parasites, is largely understudied for Afrotropical species. Here, we combined field ecology, biochemical, molecular and chemical approaches, to decipher plant feeding associations in field-collected sand flies from a dry ecology endemic for leishmaniasis in Kenya revealing i) similar rates of plant feeding among sand fly sexes sampled from indoor and outdoor environments, ii) Acacia plants in the family Fabaceae as those readily foraged on by sand fly species in Phlebotomus and Sergentomyia, iii) fructose as the common sugar in sand flies and leaves of selected plant species in the Fabaceae family, iv) compounds namely benzyl alcohol, (Z)-linalool oxide, (E)-β-ocimene, p-cymene, p-cresol, and m-cresol, as discriminating volatile organic compounds between volatiles of selected Fabaceae plants. The findings indicate selective sand fly plant feeding and suggest that the discriminating volatile organic compounds could be exploited in attractive toxic sugar- and odor-bait technologies for sand fly control.

Exploring the influence of different habitats and their volatile chemistry in modulating sand fly population structure in a leishmaniasis endemic foci, Kenya

Phlebotomine sand flies transmit many viral protozoan and bacterial pathogens of public health importance. Knowledge of the ecologic factors influencing their distribution at local scale can provide insights into disease epidemiology and avenues for targeted control. Animal sheds, termite mounds and houses are important peri-domestic and domestic habitats utilized by different sand flies as resting or breeding habitats. However, our knowledge for selection of these habitats by sand flies remains poor. Here, we tested the hypothesis that these habitat types harbor different composition of sand fly species and differ in their volatile chemistry that could influence sand fly selection. To achieve this, we employed CDC light traps following a cross-sectional survey to investigate the distribution of sand flies in the three habitats in an endemic site for leishmaniasis in Kenya. The study was carried out during the dry season, when sand flies are optimally abundant in 2018 and 2020. Sand fly abundance did not vary between the habitats, but species-specific differences in abundance was evident. Measures of sand fly community structure (Shannon diversity and richness) were highest in animal shed, followed by termite mound and lowest inside human dwelling (house). This finding indicates broader attraction of both sexes of sand flies and females of varying physiological states to animal sheds potentially used as breeding or resting sites, but also as a signal for host presence for a blood meal. Furthermore, gas chromatography-mass spectrometric analysis of volatiles collected from represented substrates associated with these habitats viz: human foot odor on worn socks (houses indoors), cow dung (animal sheds) and termite mounds (enclosed vent), revealed a total of 47 volatile organic compounds. Of these, 26, 35 and 16 were detected in human socks, cow dung and enclosed termite vent, respectively. Of these volatiles, 1-octen-3-ol, 6-methyl-5-hepten-2-one, α-pinene, benzyl alcohol, m-cresol, p-cresol and decanal, previously known as attractants for sandflies and other blood-feeding insects, were common to the habitats. Our results suggest that habitat volatiles may contribute to the composition of sand flies and highlight their potential for use in monitoring sand fly populations.

Studies of host preferences of wild-caught Phlebotomus orientalis and Ph. papatasi vectors of leishmaniasis in Sudan

Introduction

Understanding the feeding behavior and host choice of sand flies provides valuable information on vector-host relationships and elucidates the epidemiological patterns of leishmaniasis transmission. Blood meal analysis studies are essential for estimating the efficiency of pathogen transmission, assessing the relative human disease risk, and assist in identifying the other potential hosts of leishmaniasis. In Sudan and most of East Africa, there are large remaining gaps in knowledge regarding the feeding habits of phlebotomine vectors. The study aimed to identify the blood meal sources and, therefore, the host preferences of the principal vectors Phlebotomus orientalis and Ph. papatasi in leishmaniasis endemic areas of eastern and central Sudan.

Materials and methods

Sand flies were collected from two endemic villages in eastern and central Sudan using CDC light traps and sticky traps. The phlebotomine sand flies were morphologically and then molecularly identified. The source of blood meal of the engorged females was determined using a multiplex PCR methodology and specific primers of cytochrome b gene of mitochondrial DNA for human, goat, cow, and dog. The detection of the Leishmania parasite was done using PCR.

Results

The total number of collected female phlebotomine sand flies was 180. Morphological identification revealed the abundance of Ph. orientalis 103 (57.2%), Ph. papatasi 42 (23.3%), Ph. bergeroti 31 (17.2%), Ph. rodhaini 2 (1.1%) and Ph. duboscqi 2 (1.1%) in the study sites. Out of the 180 collected, 31 (17%) were blood-fed flies. Three species were blood-fed and molecularly identified: Ph. papatasi (N = 7, 22.6%), Ph. bergeroti (N = 9, 26%), and Ph. orientalis (N = 15, 48.4%). Blood meal analysis revealed human DNA in two Ph. orientalis (6.4%), hence, the anthropophilic index was 13.3%.

Conclusions

Multiplex PCR protocol described here allowed the identification of blood meal sources of many vertebrate species simultaneously. The results indicate that wild-caught Ph. orientalis are anthropophilic in the study areas. Further studies on larger blood-fed sample size are required to validate the potential applications of this technique in designing, monitoring and evaluating control programs, particularly in investigating the potential non-human hosts of leishmaniasis.

Genetic Structure of Phlebotomus orientalis (Diptera: Psychodidae) in Leishmaniasis Endemic Foci of Sudan

BACKGROUND AND OBJECTIVE

Visceral leishmaniasis (VL) remains a major concern in many parts of Sudan. The disease is transmitted by Phlebotomus orientalis. The objective of this study was to determine genetic structure of Phlebotomus orientalis population from 5 geographical regions in Sudan.

MATERIALS AND METHODS

A total of 194 individual sand flies were collected from 5 geographic regions in Sudan. The field collected sand flies were analyzed by Random Amplified Polymorphic DNA (RAPD) using 30 primers.

RESULTS

Eight hundred and 65 bands from 4 RAPD primers were analyzed for genetic variation. A higher level of intrapopulational variability was detected in populations of P. orientalis from eastern Sudan compared to those populations from central and northern Sudan. Diagnostic bands were detected in populations of P. orientalis central Sudan. Hieratical clustering analysis showed clear clustering into 2 main populations with 1 population subdivided into 4 subpopulations. However, these populations did not show any correlation with their geographical origins. Furthermore, the low genetic differentiation among subpopulations was supported by fixation index (FST) estimated by analysis of molecular variance (AMOVA).

CONCLUSION

It is concluded that the populations of P. orientalis from the selected areas in Sudan have a low genetic differentiation. However, assessment of genetic structure of P. orientalis populations is important for understanding the patterns of transmission of VL in different endemic areas.

Inventory and taxonomy of phlebotomine sand flies of the Mokolo leishmaniasis focus, northern Cameroon, with description of new Sergentomyia taxa (Diptera: Psychodidae)

Leishmaniasis is endemic in northern Cameroon. However, the sand fly vectors have not been incriminated. A sand fly species inventory was generated by integrating a number of techniques. Miniature light traps were used for collecting sand flies in a variety of ecotopes found across the area, and a morphological and molecular identification approach for taxonomic confirmation was undertaken. In a pilot survey conducted in September 2012, we captured 687 sand flies, 259 of which were morphologically identified to species level. They represent 14 species of the genera Sergentomyia and Grassomyia. No Phlebotomus spp. were found. A second series of collections was carried out during 2013 in five different environmental setups: two urban, two peri-urban/rural and one sylvatic; 14,036 sand flies (6665 males and 7371 females) were collected. A total of 5926 females and 98 males were morphologically identified to species level, representing 19 species of the genera Sergentomyia, Grassomyia and Phlebotomus, including Ph. duboscqi, a known vector of cutaneous leishmaniasis in the region. Two new taxa were found and are described: Sergentomyia (Sintonius) thomsoni mandarai ssp. nov. and Se. coronula sp. nov. Our study is the first to report the following species in Cameroon: Se. (Sin.) thomsoni (as ssp. nov. mandarai), Se. (Ser.) cincta, Se. (Sin.) affinis ssp. vorax, Se. (Sin.) adami, Se. (Sin.) herollandi, and Se. (Sin.) christophersi. In addition, some morphologically atypical Sergentomyia specimens (combination of Ser. x Sin. traits) were recorded. A checklist of 32 species reports from Cameroon is presented.

Presence of Sergentomyia (Parrotomyia) lewisi (Diptera: Psychodidae) in Tunisia

In Tunisia, 17 phlebotomine sand fly species are reported, belonging to genera Phlebotomus and Sergentomyia. However, subsequent to faunal studies and outbreaks of leishmaniasis in different regions of the country, unrecognized sand fly species could exist. Indeed, we report in this study the presence of Sergentomyia (Parrotomyia) lewisiParrot 1948. A brief collection of phlebotomine sand flies was undertaken in August 2016 in Khbina locality, in Sidi Bouzid governorate situated in Central Tunisia, which constitutes an old focus of Zoonotic Cutaneous Leishmaniasis. Sand flies were collected, using CDC light traps that were placed overnight, in different biotopes (inside habitations, outdoors, and within animal shelters). Specimens were collected and morphologically identified. Measurements were taken with an ocular micrometer. Two female specimens of the species Se. (Parrotomyia) lewisi were collected. One specimen is here described and measured. A comparison of its taxonomic characters to the holotype from Sudan and a specimen from Algeria is also presented. This species was until now only reported from Sudan, Ethiopia, Algeria, and Morocco. It is here described for the first time in Tunisia, which raises the Tunisian sand fly fauna to seven subgenera and 18 species.

Phlebotomine sandflies of Botswana: a taxonomic review and a faunistic update with the first record of genus Phlebotomus

The first records of phlebotomine sandflies from Botswana have been published only recently, comprising of four species of genus Sergentomyia. This update presents the first record of genus Phlebotomus, namely Ph. (Anaphlebotomus) rodhaini Parrot, which is also the first detection of a putative vector of leishmaniasis in Botswana. In addition, records of the Sergentomyia "bedfordi (Newstead) group" are reviewed, and the molecular taxonomy of all taxa known from Botswana is analysed based on three mitochondrial gene fragments (mtDNA). The presence of Se. congolensis (Bequaert and Walrveus) and Se. salisburiensis (Abonnenc) is confirmed, whereas the previously mentioned Se. caliginosa Davidson and unassigned specimens of the "bedfordi group" are proposed to belong to the tentatively named Se. bedfordi "Maun" form. The mtDNA analyses confirmed the species delimitations. For the first time, portions of the ND5 gene were used for the purpose of sandfly molecular taxonomy. This gene revealed a high inter-specific variability and may thus be applied as an alternative molecular marker for future studies.

Sandflies (Diptera: Psychodidae) in a focus of visceral leishmaniasis in White Nile, Sudan

Visceral leishmaniasis (VL) has been known to occur since the 1980s on the western bank of the White Nile River (Central Sudan), 150 km south of Khartoum, and has resulted in high mortality. The most recent outbreak of the disease in this area began in 2006. Entomological surveys were carried out during May 2008, June 2010 and May and July 2011 in the White Nile area. Sandflies were collected using Centers for Disease Control light traps and sticky oil traps in the village of Kadaba and the nearby woodland. Phlebotomus females were dissected for the presence of Leishmania promastigotes. A total of 17,387 sandflies, including six species of Phlebotomus and 10 species of Sergentomyia, were identified. The Phlebotomus species recorded were Phlebotomus orientalis, Phlebotomus papatasi, Phlebotomus bergeroti, Phlebotomus duboscqi, Phlebotomus rodhaini and Phlebotomus saevus. P. orientalis was collected in both habitats. The relative abundance of P. orientalis in the woodland habitat was higher than that recorded in the village habitat. In the woodland habitat, there was a notable increase in the relative abundance of P. orientalis during the surveys conducted in 2008 and 2010 compared to 2011. None of the 311 P. orientalis females dissected were infected with Leishmania promastigotes, although relatively high parous rates were recorded in both habitats. Based on the distribution of P. orientalis recorded in this study, this species is the most likely vector of VL in the endemic focus in the White Nile area. Further investigation is required to elucidate the seasonal abundance and distribution of the vector, as well as the transmission season of VL in both habitats so that appropriate control strategies for the vector can be designed.

First report of the visceral leishmaniasis vector Phlebotomus martini (Diptera: Psychodidae) in Tanzania

Phlebotomus martini is a known vector of visceral leishmaniasis caused by Leishmania donovani in sub-Saharan Africa. The disease is known to be endemic in areas of north and south Sudan, Kenya, Ethiopia, Uganda, and Somalia but has not been reported from Tanzania. In this report we present the first documented collection of P. martini and P. vansomerenae in Tanzania. Sand flies were collected using standard dry-ice baited CDC light traps (John W. Hock Company, Gainesville, FL) from five sampling sites in the Arusha and Kilimanjaro regions from 14 to 20 July 2010. Phlebotomus martini was collected from all sites and represented 6.6% of the total identified sand flies. Phlebotomus martini ranged from 4.5 to 9.4% of the total identified catch from the four sites in the Kilimanjaro region and 17.9% of the total identified catch at the one collection site in the Arusha region. In addition, one male specimen of the sibling species, Phlebotomus vansomerenae, was found at Chemka Springs in the Kilimanjaro region. These data indicate the presence of an established population(s) of P. martini in northern Tanzania that could support L. donovani transmission in an area with no prior case history of visceral leishmaniasis.

Environmental factors underlying spatial patterns of sand flies (Diptera: Psychodidae) associated with leishmaniasis in southern Sinai, Egypt

Although Leishmania major is endemic in parts of the Sinai of Egypt, the ecology and distribution of Leishmania sand fly vectors in southern Sinai has not been well characterized. Accordingly, additional sand fly samples were obtained at 41 sites in the southern Sinai region during 1996-1997, and analyzed to improve the characterization of risk of sand fly-borne pathogens. Using a Geographic Information System (GIS), species-specific spatial distributions that might suggest zoonotic cutaneous leishmaniasis (ZCL) risk areas were determined in relation to contextual environmental factors, including geology, hydrogeology, climate variables and elevation. Southern Sinai was characterized by a diverse sand fly fauna (eight Phlebotomus species), probably attributable to highly variable landscape and environmental factors. Phlebotomus alexandri, Phlebotomus kazeruni and Phlebotomus sergenti were widespread and abundant, Phlebotomus papatasi and Phlebotomus bergeroti were less frequent, and Phlebotomus arabicus, Phlebotomus major and Phlebotomus orientalis had highly restricted distributions. Logistic regression models indicated that elevation and climatic conditions were limiting determinants for the distributions of sand flies in southern Sinai. Based on the predicted distribution of P. papatasi, a recognized vector of L. major, about one-quarter of southern Sinai may be at high risk of ZCL. Risk areas for the suspected ZCL vector P. bergeroti had a more patchy distribution. Results suggest that future studies should include other factors related to vector abundance, vector competence, human population, and parasite and reservoir host(s) to produce more comprehensive ZCL transmission risk maps, thus helping in planning effective prevention and control strategies.

Insecticide resistance in the sand fly, Phlebotomus papatasi from Khartoum State, Sudan

BACKGROUND

Phlebotomus papatasi the vector of cutaneous leishmaniasis (CL) is the most widely spread sand fly in Sudan. No data has previously been collected on insecticide susceptibility and/or resistance of this vector, and a first study to establish a baseline data is reported here.

METHODS

Sand flies were collected from Surogia village, (Khartoum State), Rahad Game Reserve (eastern Sudan) and White Nile area (Central Sudan) using light traps. Sand flies were reared in the Tropical Medicine Research Institute laboratory. The insecticide susceptibility status of first progeny (F1) of P. papatasi of each population was tested using WHO insecticide kits. Also, P. papatasi specimens from Surogia village and Rahad Game Reserve were assayed for activities of enzyme systems involved in insecticide resistance (acetylcholinesterase (AChE), non-specific carboxylesterases (EST), glutathione-S-transferases (GSTs) and cytochrome p450 monooxygenases (Cyt p450).

RESULTS

Populations of P. papatasi from White Nile and Rahad Game Reserve were sensitive to dichlorodiphenyltrichloroethane (DDT), permethrin, malathion, and propoxur. However, the P. papatasi population from Surogia village was sensitive to DDT and permethrin but highly resistant to malathion and propoxur. Furthermore, P. papatasi of Surogia village had significantly higher insecticide detoxification enzyme activity than of those of Rahad Game Reserve. The sand fly population in Surogia displayed high AChE activity and only three specimens had elevated levels for EST and GST.

CONCLUSIONS

The study provided evidence for malathion and propoxur resistance in the sand fly population of Surogia village, which probably resulted from anti-malarial control activities carried out in the area during the past 50 years.

A possible role for Phlebotomus (Anaphlebotomus) rodhaini (Parrot, 1930) in transmission of Leishmania donovani

Background

Visceral leishmaniasis (VL, kala azar), caused by Leishmania donovani is a major health problem in Sudan and other East African countries. In this region the only proven vectors of L. donovani are Phlebotomus orientalis in eastern Sudan, Ethiopia and Upper Nile areas of Southern Sudan and Phlebotomus martini in Ethiopia, Kenya and Southern Sudan. In this report, we present the first evidence that Phlebotomus rodhaini may also play a role in maintaining transmission of L. donovani between animal reservoir hosts in eastern Sudan. The study was conducted in a zoonotic focus of visceral leishmaniasis in Dinder National Park, eastern Sudan, where previous work showed high infection rates of L. donovani in P. orientalis. Sand flies, captured by CDC traps were dissected and examined for infection with Leishmania parasites. Parasite isolates were subjected to L. donovani specific PCR. Field experiments were also carried out to compare efficiency of rodent baited and un-baited CDC traps in collection of P. rodhaini and determine its man-biting rate.

Results

Three female P. rodhaini were found infected with Leishmania parasites in an astonishingly small number of flies captured in three separate field trips. Two of these isolates were typed by molecular methods as L. donovani, while the third isolate was inoculated into a hamster that was subsequently lost. Although P. rodhaini is generally considered a rare species, results obtained in this study indicate that it can readily be captured by rodent-baited traps. Results of human landing collection showed that it rarely bites humans in the area.

Conclusion

It is concluded that P. rodhaini is a possible vector of L. donovani between animal reservoir hosts but is not responsible for infecting humans. It is suggested that the role of P. rodhaini in transmission of L. donovani in other zoonotic foci of visceral leishmaniasis in Africa should be re-examined.

Phlebotomus (Paraphlebotomus) gemetchi (Diptera: Psychodidae), a new sand fly species from Ethiopia

The subgenus Paraphlebotomus of Phlebotomus includes several sand fly vectors of cutaneous and visceral leishmaniasis. A new species of the subgenus Paraphlebotomus, named Phlebotomus gemetchi is described from the volcanic blisters by the shore of lake Beseka near Metahara, Upper Awash Valley, in the Rift Valley of eastern Ethiopia. The presence of one distinct character in the male genitalia (a bifurcating 'y'-shaped spine at the middle of the style) and three characters in the female (lengths of the fourth antennal and palpal segments and labrum) easily distinguish it from the other Afrotropical species recorded in East Africa including Ethiopia. The new species is 1 of 5 species representing the subgenus in Ethiopia as well as the rest of the Afrotropical Region. The distribution and medical importance of this sand fly species requires further investigation.

Coadaptation of male aedeagal filaments and female spermathecal ducts of the old world phlebotomine sand flies (Diptera: Psychodidae)

The morphology of insect genitalia is often highly species-specific, and its variation has been suggested as an important impetus for evolution. Structural variation of the male genitalia and the female spermathecae in Phlebotomine sand flies is unique among the blood sucking Diptera. We describe the fine structures involved in mating for Phlebotomus papatasi (Scopoli). Relationships among the length of the spermathecal duct and aedeagal filament were studied in 26 species of Old World phelebotomine sand flies comprising 12 subgenera. In most taxa the aedeagal filaments were very long allowing direct insemination into the spermathecae, indicating that intrasexual competition among males occurs as sperm precedence. There was a positive correlation between the lengths of the spermathecal ducts and aedeagal filaments, indicating that an evolutionary "arms race" occurs between males and females over the control of fertilization. The pattern of genitalia variation in phlebotomine sand flies also indicated that differences in the lengths of the spermathecal ducts and aedeagal filaments are distributed unevenly among closely related species. Genital differences do not seem to occur in populations of the Phlebotomus argentipes Annandale & Brunetti complex, whereas differences showed strongly in closely related Phlebotomus papatasi and P. bergeroti Parrot, and in sympatric Phlebotomus martini Parrot and P. celiae Minter.

Influence of altitude, latitude and season of collection (Bergmann's rule) on the dimensions of Lutzomyia intermedia (Lutz & Neiva, 1912) (Diptera, Psychodidae, Phlebotominae)

The influence of altitude and latitude on some structure sizes of Lutzomyia intermedia was noted; several structures of insects collected in higher localities were greater, according to Bergmann's rule. This influence was more remarkable in two localities of the State of Espírito Santo, probably due to greater differences in altitude. Comparing insects from different latitudes, more differences were noted in comparisons of insects from low altitude localities than in those of material from higher altitudes. The small number of differences between insects collected in July and in December does not indicate a defined influence of season and temperature on the size of adults. The possible epidemiological implications of these variations are discussed.

Protective efficacy of lambdacyhalothrin-impregnated bednets against Phlebotomus orientalis, the vector of visceral leishmaniasis in Sudan

Field investigations on the sandfly Phlebotomus orientalis (Diptera: Psychodidae), the vector of Leishmania donovani causing visceral leishmaniasis (VL) in Sudan, were undertaken in two villages (Bellow and Elgamel) and Dinder National Park, to determine the protective value of bednets (polyester, 100 denier) impregnated with lambda-cyhalothrin 10 mg a.i./m2 pyrethroid insecticide. After exposure to treated netting for 30 s, P. orientalis females all died within 1 h. When field-tested in Acacia woodland, treated bednets provided complete protection from bites of the vector. Numbers of P. orientalis females landing on human collectors without bednets or using untreated bednets averaged 32.0 +/- 8.3 or 6.9 +/- 2.7 per man-night, respectively, whereas collectors using treated bednets experienced no sandfly bites during the same period (18.00-06.00 hours, 12 nights in June 1995). Socio-behavioural observations on the bed-time of people living in both study villages indicated that the use of impregnated bednets against P. orientalis would give more potential protection for women and children than for male adults. Overall the proportions of people and their durations of exposure to the risk of sandfly bites (i.e. after sunset until they went to bed) were 40% unprotected for< 1h, 50% for 1-2h and >10% for > or = 2h. Because visceral leishmaniasis in Sudan occurs mainly in children, the use of impregnated bednets (outdoors as well as indoors), and going to bed early could provide a high degree of personal protection against this zoonotic infection.

Impact of pyrethroid-impregnated curtains on Phlebotomus papatasi sandflies indoors at Khartoum, Sudan

Laboratory and field investigations were made in an endemic focus of cutaneous leishmaniasis in Khartoum State, Sudan, to evaluate the effects of permethrin-impregnated curtains on the human-biting activity, nocturnal activity and resting behaviour of the vector sandfly Phlebotomus papatasi (Diptera: Psychodidae) indoors. Laboratory bioassays showed that curtains impregnated with 0.5, 1.0 or 1.5 g/m2 permethrin all gave 100% mortality within 24h of exposure of P. papatasi for 3 min. Under natural field conditions, the biting activity indoors and the resting density of P. papatasi were significantly reduced (P<0.001 and P=0.036, respectively) in rooms provided with permethrin-impregnated curtains as compared to control rooms left without curtains or fitted with unimpregnated curtains. No significant difference was found between the numbers of nocturnally active P. papatasi collected in rooms provided with impregnated curtains and rooms left without curtains or provided with unimpregnated curtains (P=0.377). Evidently P. papatasi was not repelled by these doses of permethrin on curtains, but the survival rate of sandflies collected from test rooms provided with permethrin-impregnated curtains was significantly reduced (P=0.036). We conclude that use of permethrin-impregnated curtains may provide a good control method for P. papatasi and other endophilic and/or endophagic sandfly vectors of leishmaniasis.

Associations of Phlebotomus orientalis and other sandflies with vegetation types in the eastern Sudan focus of kala-azar

Abundances of Phlebotomus orientalis, P. papatasi (Diptera: Psychodidae) and other sandflies were investigated in relation to different types of vegetation associated with endemic foci of visceral leishmaniasis (kala-azar) in eastern Sudan. Sandfly collection sites were in Umsalala Village (Galabat Province) and Dinder National Park (Dinder Province). Sandfly species found in the area were P. orientalis, P. papatasi, Sergentomyia africana, S. antennata, S. clydei, S. schwetzi and S. squamipleuris. Among the types of trees in the Dinder area, P. orientalis was more abundant in forests dominated by Acacia seyal than where Combretum kordofanum, Balanites aegyptiaca, Hyphaena thaibaica or Ziziphus spinachristi were the dominant trees. At Umsalala, P. papatasi was more abundant in the village than at any site with dense vegetation, but P. orientalis was uncommon. Sergentomyia spp. were distributed fairly evenly amongst most types of vegetation investigated at both localities. The ecological distribution of sandflies and epidemiology of kala-azar in Sudan are discussed with emphasis on the association of P. orientalis with A. seyal woodlands.

Fructose in wild-caught Phlebotomus ariasi and the possible relevance of sugars taken by sandflies to the transmission of leishmaniasis

Cold, acidified anthrone was used to test 200 wild-caught sandflies (Phlebotomus ariasi females) for the presence of fructose. This sugar, or others with a fructose moiety, were demonstrable in 157 (79%) of the flies; proportions of flies positive in different tests ranged from 44 to 91%. Higher proportions of flies gave positive results when tested less than one hour after capture than when kept in the laboratory for more than 12 hours before testing. Similarly high percentages of flies were positive in samples collected coming to engorge on dogs and in those caught in CDC miniature light traps. These results, together with published reports of the demonstration of sugars in 25 individually tested sandflies of other species confirm that, like other biting flies, sugar is an important part of the diet of sandflies. Natural sugars may influence the development of leishmaniae in sandflies and their subsequent transmission. The anthrone test was found to be simple, rapid and suitable for field use; it is a valuable addition to indirect techniques for the study of the behaviour of sandflies.