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Papers by Alon Warburg

PLOS Neglected Tropical Diseases, 2013

Acta Tropica, 2018

Visceral Leishmaniasis (VL) is a disseminated protozoan infection caused by Leishmania donovani t... more Visceral Leishmaniasis (VL) is a disseminated protozoan infection caused by Leishmania donovani that affects almost half a million people annually. In Northern Ethiopia, VL is common in migrant agricultural laborers returning from the lowland sesame fields of Metema and Humera. Recent VL foci have emerged in resident rural populations near the town. In the current study, we evaluate multilevel entomological, epidemiological and ecological factors associated with infection and disease through fine-scale eco-epidemiological analyses in three villages. Satellite images showed that villages constructed in or close to vertisols, were likely to become endemic for VL. Vertisols or black-cotton soil, are characterized by high contents of smectitic clay minerals, which swell when hydrated and shrink upon desiccation, causing extensive deep cracking during the dry season. The population densities of Phlebotomus orientalis, the vector, were negatively correlated with distance from vertisols and persons living close to vertisols were more likely to be bitten by sand flies, as evidenced by sero-positivity to Ph. orientalis saliva. Apparent (albeit non-significant) clustering of VL cases and abundant asymptomatic infections close to vertisols, suggest anthroponotic transmission around houses located close to vertisols. Comparable rates of male and female volunteers, mostly under 15 years of age, were infected with L. donovani but a significantly higher proportion of males succumbed to VL indicating a physiological gender-linked male susceptibility. Our data suggest that the abundant infected persons with high parasitemias who remain asymptomatic, may serve as reservoir hosts for anthroponotic transmission inside villages. Only limited insights on the transmission dynamics of L. donovani were gained by the study of environmental factors such as presence of animals, house structure and vegetation cover.

PLOS Neglected Tropical Diseases, 2018

Background Phlebotomus orientalis is a vector of Leishmania donovani, the causative agent of life... more Background Phlebotomus orientalis is a vector of Leishmania donovani, the causative agent of life threatening visceral leishmaniasis spread in Eastern Africa. During blood-feeding, sand fly females salivate into the skin of the host. Sand fly saliva contains a large variety of proteins, some of which elicit specific antibody responses in the bitten hosts. To evaluate the exposure to sand fly bites in human populations from disease endemic areas, we tested the antibody reactions of volunteers' sera against recombinant P. orientalis salivary antigens. Methodology/Principal findings Recombinant proteins derived from sequence data on P. orientalis secreted salivary proteins, were produced using either bacterial (five proteins) or mammalian (four proteins) expression systems and tested as antigens applicable for detection of anti-P. orientalis IgG in human sera. Using these recombinant proteins, human sera from Sudan and Ethiopia, countries endemic for visceral leishmaniasis, were screened by ELISA and immunoblotting to identify the potential markers of exposure to P. orientalis bites. Two recombinant proteins; mAG5 and mYEL1, were identified as the most promising antigens showing high correlation coefficients as well as good specificity in comparison to the whole sand fly salivary gland homogenate. Combination of both proteins led to a further increase of correlation coefficients as well as both positive and negative predictive values of P. orientalis exposure. Conclusions/Significance This is the first report of screening human sera for anti-P. orientalis antibodies using recombinant salivary proteins. The recombinant salivary proteins mYEL1 and mAG5 proved to be

Acta tropica, Jan 13, 2017

The Leishmaniases are caused by the protozoan parasites of the genus Leishmania and are transmitt... more The Leishmaniases are caused by the protozoan parasites of the genus Leishmania and are transmitted to humans by the bite of infected female phlebotomine sand flies. Both visceral and cutaneous leishmaniases are widely distributed in different parts of Ethiopia. The aim of this study was to determine the diversity and altitudinal distribution of phlebotomine sand flies from Kafta Humera to Gondar town in northwest Ethiopia. Seven localities were selected with distinct altitudinal variations between 550m above sea level (m a.s.l) and 2300m a.s.l. In each locality, sand flies were collected using standard CDC light traps and sticky traps during the active sand fly season from December 2012 to May 2013. Shannon-Weiner species diversity index and Jaccard's coefficient were used to estimate species diversity and similarity between altitudes and localities, respectively. A total of 89,044 sand flies (41,798 males and 47, 246 females) were collected from the seven localities/towns thro...

The American Journal of Tropical Medicine and Hygiene, 2002

Fifty patients from rural areas in the Jenin district of the West Bank, Palestinian Authority, we... more Fifty patients from rural areas in the Jenin district of the West Bank, Palestinian Authority, were diagnosed with visceral leishmaniasis (VL) between 1989 and 1998. Forty-nine (98%) were younger than 6 years old, the youngest being 9 months. The yearly incident rate of VL in the Jenin district was highest in 1994 (11.8/100,000) and decreased to 1.5/100,000 in 1998; a mortality rate of 4% was recorded. Seventeen (5.5%) of 308 dogs from the Jenin and Ramallah districts of the West Bank were seropositive by enzyme-linked immunosorbent assay in a survey of canine leishmaniasis. Although all the leishmanial strains cultured from humans and dogs were identified as Leishmania infantum by a species-specific polymerase chain reaction, further genetic analysis by restriction fragment length polymorphism of kinetoplast DNA revealed patterns of polymorphism within isolates. The findings indicate that an active focus of potentially fatal VL exits in the Jenin district of the West Bank and that the parasite, vector, and reservoir host are found in this area. The epidemiology of VL in that vicinity follows the pattern of a predominantly infantile disease traditionally found in Middle Eastern countries, without a considerable involvement of immunocompromised adults infected with HIV virus as reported in other regions.

PloS one, 2017

Visceral leishmaniasis (VL) also known as kala-azar is a growing health problem in Ethiopia with ... more Visceral leishmaniasis (VL) also known as kala-azar is a growing health problem in Ethiopia with an estimated annual VL incidence between 3700 and 7400. The disease is mainly endemic in northwestern parts of the country. The aim of the current study was to determine the sand fly fauna and ecology of Phlebotomus orientalis in two endemic and ecologically distinct areas of northwestern Ethiopia. Sand flies were collected using CDC light traps, sticky traps and pyrethrum spray catches from peri-domestic, mixed forest, farm field and indoor habitats from both Libo-Kemkem (May 2011-April 2012) and Metema (October 2012-September 2013) districts. A total of 51,411 sand fly specimens were collected and identified (10,776 from highland and 40, 635 from the lowland areas). Seven species were found in the highland area: two Phlebotomus spp. (P. orientalis and P. rodhaini) and five Sergentomyia species. Whereas 19 species were found in the lowland area: six Phlebotomus (P. orientalis, P. rodhai...

The American journal of tropical medicine and hygiene, Jan 13, 2017

Reported herein is the first case of Leishmania-human immunodeficiency virus (HIV) coinfection in... more Reported herein is the first case of Leishmania-human immunodeficiency virus (HIV) coinfection in Ecuador. In Ecuador, HIV infections overlap endemic areas of leishmaniasis. Immunosuppression is a well-established risk factor for developing severe disease. This is a severe case of a 32-year-old man presenting with disseminated pleomorphic ulcers, papules, and cutaneous plaque-like lesions over his whole body. Numerous amastigotes were observed in both skin scrapings and biopsies. The sequence of the cytochrome b gene confirmed the presence of Leishmania guyanensis The patient was treated but failed to respond to meglumine antimoniate and amphotericin B. Six months later, the patient died due to bacterial septic shock.

Scientific Reports, 2016

Little is known about the feeding behavior of hematophagous insects that require plant sugar to c... more Little is known about the feeding behavior of hematophagous insects that require plant sugar to complete their life cycles. We studied plant feeding of Lutzomyia longipalpis sand flies, known vectors of Leishmania infantum/chagasi parasites, in a Brazilian city endemic with visceral leishmaniasis. The DNA barcode technique was applied to identify plant food source of wild-caught L. longipalpis using specific primers for a locus from the chloroplast genome, ribulose diphosphate carboxylase. DNA from all trees or shrubs within a 100-meter radius from the trap were collected to build a barcode reference library. While plants from the Anacardiaceae and Meliaceae families were the most abundant at the sampling site (25.4% and 12.7% of the local plant population, respectively), DNA from these plant families was found in few flies; in contrast, despite its low abundance (2.9%), DNA from the Fabaceae family was detected in 94.7% of the sand flies. The proportion of sand flies testing positi...

Parasites & Vectors, 2015

Background: Phlebotomus orientalis is the major vector of the intramacrophage protozoa, Leishmani... more Background: Phlebotomus orientalis is the major vector of the intramacrophage protozoa, Leishmania donovani, the etiological agent of visceral leishmaniasis (VL) in northern Ethiopia and Sudan. The objective of this study was to determine the nocturnal periodicity of P. orientalis in the VL endemic focus of Tahtay Adiyabo district, northern Ethiopia. Methods: Sandflies were collected using CDC light traps by changing collecting bags at an hourly interval from dusk to dawn for six months (January-June 2013) from outdoors (i.e. peri-domestic and agricultural fields). Sandfly specimens collected in the study were identified to species level and counted. Results: In total, 21,716 nocturnally active sandfly specimens, which belong to two genera (i.e., Phlebotomus and Sergentomyia) were collected and identified. In the collection, P. orientalis, the dominant species in the genus Phlebotomus, constituted 33.79% while Sergentomyia spp. comprised 65.44%. Analysis of data showed that activity of P. orientalis females increased from 18:00 to 24:00 hours, with a peak after midnight (24:00-03:00 hrs). Likewise, activity of parous P. orientalis females was found to be unimodal, peaking at 24-01:00 hrs. Conclusion: P. orientalis females had marked nocturnal activity, which peak after midnight. Similarly, the epidemiologically dangerous parous females generally were more active after midnight. Therefore, humans are at risk of L. donovani infections through the bite of P. orientalis possibly between midnight and dawn.

Parasites & Vectors, 2015

Background: Phlebotomus orientalis is the main sandfly vector of visceral leishmaniasis in the no... more Background: Phlebotomus orientalis is the main sandfly vector of visceral leishmaniasis in the north and northwest of Ethiopia. CDC light traps and sticky traps are commonly used for monitoring sandfly populations. However, their trapping efficiency is greatly influenced by various environmental factors including moonlight and lunar periodicity. In view of that, the current study assessed the effect of moonlight and lunar periodicity on the performance of light traps in collecting P. orientalis. Methods: Trapping of P. orientalis and other Phlebotomus spp. was conducted for 7 months between December 2012 and June 2013 using CDC light traps and sticky traps from peri-domestic and agricultural fields. Throughout the trapping periods, collections of sandfly specimens were carried out for 4 nights per month, totaling 28 trapping nights that coincided with the four lunar phases (viz., first quarter, third quarter, new and full moon) distributed in each month. Results: In total, 13,533 sandflies of eight Phlebotomus species (P. orientalis, P. bergeroti, P. rodhaini, P. duboscqi, P. papatasi, P. martini, P. lesleyae and P. heischi) were recorded. The predominant species was P. orientalis in both trapping sites and by both methods of collection in all lunar phases. A significant difference (P < 0.05) was observed in the mean numbers of P. orientalis and other Phlebotomus spp. caught by CDC light traps among the four lunar phases. The highest mean number (231.13 ± 36.27 flies/trap/night) of P. orientalis was collected during the new moon phases, when the moonlight is absent. Fewer sandflies were attracted to light traps during a full moon. However, the number of P. orientalis and the other Phlebotomus spp. from sticky traps did not differ in their density among the four lunar phases (P = 0.122). Conclusion: Results of the current study demonstrated that the attraction and trapping efficiency of CDC light traps is largely influenced by the presence moonlight, especially during a full moon. Therefore, sampling of sandflies using light traps to estimate population density and other epidemiological studies in the field should take the effect of moonlight and lunar periodicity into account on the trapping efficacy of light traps.

Acta tropica, 2014

We studied breeding sites of Phlebotomus orientalis (Diptera: Psychodidae) the vector of visceral... more We studied breeding sites of Phlebotomus orientalis (Diptera: Psychodidae) the vector of visceral leishmaniasis in northern Ethiopia. Although numbers were rather small, 165 sand flies were captured emerging from vertisol cracks. The most productive breeding sites were cracked vertisols, dry river banks and close to trees. No sand flies were caught emerging from sandy clay loam soils in peri-domestic habitats but a few were captured emerging from gaps in a stone wall. Abiotic parameters in vertisols close to trees and in open field from which P. orientalis had emerged, were compared. Soil pH was slightly alkaline and salinity was low. Organic matter contents were similar in both sites. Temperatures and RH remained relatively stable near trees from the end of the rainy season through mid dry season, yet fluctuated markedly at the shallower depth in the open field. During the rainy season, cracks in the soil were sealed resulting in significant lowering of the oxygen concentrations ne...

Transactions of the Royal Society of Tropical Medicine and Hygiene, 2011

This article appeared in a journal published by Elsevier. The attached copy is furnished to the a... more This article appeared in a journal published by Elsevier. The attached copy is furnished to the author for internal non-commercial research and education use, including for instruction at the authors institution and sharing with colleagues. Other uses, including reproduction and distribution, or selling or licensing copies, or posting to personal, institutional or third party websites are prohibited. In most cases authors are permitted to post their version of the article (e.g. in Word or Tex form) to their personal website or institutional repository. Authors requiring further information regarding Elsevier's archiving and manuscript policies are encouraged to visit:

Soil and Tillage Research, 2014

PLoS Neglected Tropical Diseases, 2014

Background: In East Africa, Phlebotomus orientalis serves as the main vector of Leishmania donova... more Background: In East Africa, Phlebotomus orientalis serves as the main vector of Leishmania donovani, the causative agent of visceral leishmaniasis (VL). Phlebotomus orientalis is present at two distant localities in Ethiopia; Addis Zemen where VL is endemic and Melka Werer where transmission of VL does not occur. To find out whether the difference in epidemiology of VL is due to distant compositions of P. orientalis saliva we established colonies from Addis Zemen and Melka Werer, analyzed and compared the transcriptomes, proteomes and enzymatic activity of the salivary glands. Methodology/Principal Findings: Two cDNA libraries were constructed from the female salivary glands of P. orientalis from Addis Zemen and Melka Werer. Clones of each P. orientalis library were randomly selected, sequenced and analyzed. In P. orientalis transcriptomes, we identified members of 13 main protein families. Phylogenetic analysis and multiple sequence alignments were performed to evaluate differences between the P. orientalis colonies and to show the relationship with other sand fly species from the subgenus Larroussius. To further compare both colonies, we investigated the humoral antigenicity and cross-reactivity of the salivary proteins and the activity of salivary apyrase and hyaluronidase. Conclusions: This is the first report of the salivary components of P. orientalis, an important vector sand fly. Our study expanded the knowledge of salivary gland compounds of sand fly species in the subgenus Larroussius. Based on the phylogenetic analysis, we showed that P. orientalis is closely related to Phlebotomus tobbi and Phlebotomus perniciosus, whereas Phlebotomus ariasi is evolutionarily more distinct species. We also demonstrated that there is no significant difference between the transcriptomes, proteomes or enzymatic properties of the salivary components of Addis Zemen (endemic area) and Melka Werer (non-endemic area) P. orientalis colonies. Thus, the different epidemiology of VL in these Ethiopian foci cannot be attributed to the salivary gland composition.

PLoS Neglected Tropical Diseases, 2012

Phlebotomine sand flies transmit Leishmania, phlebo-viruses and Bartonella to humans. A prominent... more Phlebotomine sand flies transmit Leishmania, phlebo-viruses and Bartonella to humans. A prominent gap in our knowledge of sand fly biology remains the ecology of their immature stages. Sand flies, unlike mosquitoes do not breed in water and only small numbers of larvae have been recovered from diverse habitats that provide stable temperatures, high humidity and decaying organic matter. We describe studies designed to identify and characterize sand fly breeding habitats in a Judean Desert focus of cutaneous leishmaniasis. To detect breeding habitats we constructed emergence traps comprising sand fly-proof netting covering defined areas or cave openings. Large size horizontal sticky traps within the confined spaces were used to trap the sand flies. Newly eclosed male sand flies were identified based on their un-rotated genitalia. Cumulative results show that Phlebotomus sergenti the vector of Leishmania tropica rests and breeds inside caves that are also home to rock hyraxes (the reservoir hosts of L. tropica) and several rodent species. Emerging sand flies were also trapped outside covered caves, probably arriving from other caves or from smaller, concealed cracks in the rocky ledges close by. Man-made support walls constructed with large boulders were also identified as breeding habitats for Ph. sergenti albeit less important than caves. Soil samples obtained from caves and burrows were rich in organic matter and salt content. In this study we developed and put into practice a generalized experimental scheme for identifying sand fly breeding habitats and for assessing the quantities of flies that emerge from them. An improved understanding of sand fly larval ecology should facilitate the implementation of effective control strategies of sand fly vectors of Leishmania.

Parasites & Vectors, 2013

Background: Visceral leishmaniasis (VL) known as Kala-Azar is a serious systemic disease caused b... more Background: Visceral leishmaniasis (VL) known as Kala-Azar is a serious systemic disease caused by Leishmania donovani parasites (Trypanosomatidae: Kinetoplastida). The disease is prevalent in the Indian Sub-continent, East Africa and Brazil. In Africa, the worst affected regions are in Sudan, with an estimated 15,000-20,000 cases annually and Ethiopia with 5,000-7,000 cases a year. The main vector of VL in Sudan and Northern Ethiopia is Phlebotomus orientalis, a sand fly frequently found in association with Acacia spp and Balanite spp woodlands. Methods: To optimize sampling of sand flies for epidemiological studies in remote areas we tested different means of attraction. Miniature suction traps employing 2AA batteries (3 V) were deployed in the up-draft orientation and baited with chemical light-sticks (Red, Yellow and Green), or bakers' yeast in sugar solution (emitting CO 2 and perhaps other attractants). These traps were compared with standard CDC incandescent light traps employing 6 V batteries. Trials were conducted during two consecutive years at different localities around Sheraro, a town in West Tigray, Northern Ethiopia. Results: The sand fly species composition was similar but not identical in the different locations tested with different Sergentomyia spp. predominating. Phlebotomus spp. comprised less than 1% of the catches during the first year trials (November-December 2011) but increased markedly during the second year trials performed later in the dry season at the height of the sand fly season in February 2012. Although there did not appear to be a species bias towards different light wavelengths , fermenting yeast in sugar solution attracted relatively more Phlebotomus spp. and Sergentomyia schwetzi. Conclusions: Although the standard 6 V CDC incandescent light traps captured more sand flies, lightweight (~350 g) 3 V suction traps baited with chemical light-sticks were shown to be effective means of monitoring sand flies. Such traps operated without light and baited with yeast in sugar solution caught relatively more Phlebotomus spp.

Medical and Veterinary Entomology, 2008

The control of phlebotomine sandflies (Diptera: Psychodidae), the vectors of leishmaniasis, is di... more The control of phlebotomine sandflies (Diptera: Psychodidae), the vectors of leishmaniasis, is directed mostly against adults as larvae develop in unknown or inaccessible habitats. In the current study we tested geraniol, a natural plant-derived pro duct, as a space repellent and the synthetic pyrethroid prallethrin as a diffusible insecticide. Geraniol was dispersed in the air using diffusers with an electric fan and prallethrin was evaporated using electrically heated evaporators. Both substances were tested in inhabited bedrooms and in tents. Geraniol failed to effect significant reductions in the numbers of either Phlebotomus papatasi Scopoli in rooms or Phlebotomus sergenti Parrot in tents. In laboratory experiments, geraniol proved ineffective in preventing sandflies from feeding. By contrast, prallethrin was highly effective in reducing the number of sandflies in rooms as well as in tents. Exposure of sandflies to prallethrin in laboratory experiments caused 97% mortality rates. Both prallethrin and, to a lesser extent, geraniol reduced the number of Culex mosquitoes captured in tents. Electric liquid-vaporizers with 1.5% prallethrin are highly effective in protecting people from sandfly bites in confined spaces and may be useful in combating cutaneous leishmaniasis.

Medical and Veterinary Entomology, 2011

Mosquitoes foraging for blood sources normally fly relatively close to the ground where wind velo... more Mosquitoes foraging for blood sources normally fly relatively close to the ground where wind velocities do not exceed their flight speed. An experiment designed to block foraging mosquitoes from reaching inhabited houses was conducted in a rural settlement flanked by agricultural fields. Mosquitoes were collected during 9 nights using 30 carbon dioxide-baited traps deployed along the external walls of six houses in the row closest to the settlement's perimeter fence. Thereafter, a deltamethrin-impregnated mesh was draped along 400 m of the perimeter fence to a height of 2 m opposite three of the monitored houses. Mosquitoes were trapped for a further 11 nights. A significant difference in the numbers of mosquitoes caught before and after the intervention was demonstrated near protected houses, whereas no significant difference was observed in catches near control houses. The percentage of Culex perexiguus (Diptera: Culicidae), an important vector of West Nile virus, was significantly lower near protected houses (13%) than around control houses (45%). By contrast, the percentage of Culex pipiens was not significantly affected (16% at experimental and 18% at control houses). Although the results presented here are preliminary, the data demonstrate the potential efficacy of vertical insecticidal barriers for mosquito control.

Journal of Vector Ecology, 2011

A number of mosquito species avoid predator-inhabited oviposition sites by detecting predator-rel... more A number of mosquito species avoid predator-inhabited oviposition sites by detecting predator-released kairomones. In the laboratory, we found that when offered de-ionized water and de-ionized water conditioned with Notonecta maculata, gravid Anopheles gambiae females preferentially oviposited into the former. We then conducted further experiments using two chemical components found in Notonecta-conditioned water, chemically pure n-tricosane and/or n-heneicosane, that was previously shown to repel oviposition by Culiseta longiareolata. These hydrocarbons failed to deter oviposition by An. gambiae females. Thus, different mosquito species may rely on distinct chemical cues to avoid predators. Identification and chemical characterization of such kairomones could facilitate innovative, environmentally sound mosquito control.

PLOS Neglected Tropical Diseases, 2013

Acta Tropica, 2018

Visceral Leishmaniasis (VL) is a disseminated protozoan infection caused by Leishmania donovani t... more Visceral Leishmaniasis (VL) is a disseminated protozoan infection caused by Leishmania donovani that affects almost half a million people annually. In Northern Ethiopia, VL is common in migrant agricultural laborers returning from the lowland sesame fields of Metema and Humera. Recent VL foci have emerged in resident rural populations near the town. In the current study, we evaluate multilevel entomological, epidemiological and ecological factors associated with infection and disease through fine-scale eco-epidemiological analyses in three villages. Satellite images showed that villages constructed in or close to vertisols, were likely to become endemic for VL. Vertisols or black-cotton soil, are characterized by high contents of smectitic clay minerals, which swell when hydrated and shrink upon desiccation, causing extensive deep cracking during the dry season. The population densities of Phlebotomus orientalis, the vector, were negatively correlated with distance from vertisols and persons living close to vertisols were more likely to be bitten by sand flies, as evidenced by sero-positivity to Ph. orientalis saliva. Apparent (albeit non-significant) clustering of VL cases and abundant asymptomatic infections close to vertisols, suggest anthroponotic transmission around houses located close to vertisols. Comparable rates of male and female volunteers, mostly under 15 years of age, were infected with L. donovani but a significantly higher proportion of males succumbed to VL indicating a physiological gender-linked male susceptibility. Our data suggest that the abundant infected persons with high parasitemias who remain asymptomatic, may serve as reservoir hosts for anthroponotic transmission inside villages. Only limited insights on the transmission dynamics of L. donovani were gained by the study of environmental factors such as presence of animals, house structure and vegetation cover.

PLOS Neglected Tropical Diseases, 2018

Background Phlebotomus orientalis is a vector of Leishmania donovani, the causative agent of life... more Background Phlebotomus orientalis is a vector of Leishmania donovani, the causative agent of life threatening visceral leishmaniasis spread in Eastern Africa. During blood-feeding, sand fly females salivate into the skin of the host. Sand fly saliva contains a large variety of proteins, some of which elicit specific antibody responses in the bitten hosts. To evaluate the exposure to sand fly bites in human populations from disease endemic areas, we tested the antibody reactions of volunteers' sera against recombinant P. orientalis salivary antigens. Methodology/Principal findings Recombinant proteins derived from sequence data on P. orientalis secreted salivary proteins, were produced using either bacterial (five proteins) or mammalian (four proteins) expression systems and tested as antigens applicable for detection of anti-P. orientalis IgG in human sera. Using these recombinant proteins, human sera from Sudan and Ethiopia, countries endemic for visceral leishmaniasis, were screened by ELISA and immunoblotting to identify the potential markers of exposure to P. orientalis bites. Two recombinant proteins; mAG5 and mYEL1, were identified as the most promising antigens showing high correlation coefficients as well as good specificity in comparison to the whole sand fly salivary gland homogenate. Combination of both proteins led to a further increase of correlation coefficients as well as both positive and negative predictive values of P. orientalis exposure. Conclusions/Significance This is the first report of screening human sera for anti-P. orientalis antibodies using recombinant salivary proteins. The recombinant salivary proteins mYEL1 and mAG5 proved to be

Acta tropica, Jan 13, 2017

The Leishmaniases are caused by the protozoan parasites of the genus Leishmania and are transmitt... more The Leishmaniases are caused by the protozoan parasites of the genus Leishmania and are transmitted to humans by the bite of infected female phlebotomine sand flies. Both visceral and cutaneous leishmaniases are widely distributed in different parts of Ethiopia. The aim of this study was to determine the diversity and altitudinal distribution of phlebotomine sand flies from Kafta Humera to Gondar town in northwest Ethiopia. Seven localities were selected with distinct altitudinal variations between 550m above sea level (m a.s.l) and 2300m a.s.l. In each locality, sand flies were collected using standard CDC light traps and sticky traps during the active sand fly season from December 2012 to May 2013. Shannon-Weiner species diversity index and Jaccard's coefficient were used to estimate species diversity and similarity between altitudes and localities, respectively. A total of 89,044 sand flies (41,798 males and 47, 246 females) were collected from the seven localities/towns thro...

The American Journal of Tropical Medicine and Hygiene, 2002

Fifty patients from rural areas in the Jenin district of the West Bank, Palestinian Authority, we... more Fifty patients from rural areas in the Jenin district of the West Bank, Palestinian Authority, were diagnosed with visceral leishmaniasis (VL) between 1989 and 1998. Forty-nine (98%) were younger than 6 years old, the youngest being 9 months. The yearly incident rate of VL in the Jenin district was highest in 1994 (11.8/100,000) and decreased to 1.5/100,000 in 1998; a mortality rate of 4% was recorded. Seventeen (5.5%) of 308 dogs from the Jenin and Ramallah districts of the West Bank were seropositive by enzyme-linked immunosorbent assay in a survey of canine leishmaniasis. Although all the leishmanial strains cultured from humans and dogs were identified as Leishmania infantum by a species-specific polymerase chain reaction, further genetic analysis by restriction fragment length polymorphism of kinetoplast DNA revealed patterns of polymorphism within isolates. The findings indicate that an active focus of potentially fatal VL exits in the Jenin district of the West Bank and that the parasite, vector, and reservoir host are found in this area. The epidemiology of VL in that vicinity follows the pattern of a predominantly infantile disease traditionally found in Middle Eastern countries, without a considerable involvement of immunocompromised adults infected with HIV virus as reported in other regions.

PloS one, 2017

Visceral leishmaniasis (VL) also known as kala-azar is a growing health problem in Ethiopia with ... more Visceral leishmaniasis (VL) also known as kala-azar is a growing health problem in Ethiopia with an estimated annual VL incidence between 3700 and 7400. The disease is mainly endemic in northwestern parts of the country. The aim of the current study was to determine the sand fly fauna and ecology of Phlebotomus orientalis in two endemic and ecologically distinct areas of northwestern Ethiopia. Sand flies were collected using CDC light traps, sticky traps and pyrethrum spray catches from peri-domestic, mixed forest, farm field and indoor habitats from both Libo-Kemkem (May 2011-April 2012) and Metema (October 2012-September 2013) districts. A total of 51,411 sand fly specimens were collected and identified (10,776 from highland and 40, 635 from the lowland areas). Seven species were found in the highland area: two Phlebotomus spp. (P. orientalis and P. rodhaini) and five Sergentomyia species. Whereas 19 species were found in the lowland area: six Phlebotomus (P. orientalis, P. rodhai...

The American journal of tropical medicine and hygiene, Jan 13, 2017

Reported herein is the first case of Leishmania-human immunodeficiency virus (HIV) coinfection in... more Reported herein is the first case of Leishmania-human immunodeficiency virus (HIV) coinfection in Ecuador. In Ecuador, HIV infections overlap endemic areas of leishmaniasis. Immunosuppression is a well-established risk factor for developing severe disease. This is a severe case of a 32-year-old man presenting with disseminated pleomorphic ulcers, papules, and cutaneous plaque-like lesions over his whole body. Numerous amastigotes were observed in both skin scrapings and biopsies. The sequence of the cytochrome b gene confirmed the presence of Leishmania guyanensis The patient was treated but failed to respond to meglumine antimoniate and amphotericin B. Six months later, the patient died due to bacterial septic shock.

Scientific Reports, 2016

Little is known about the feeding behavior of hematophagous insects that require plant sugar to c... more Little is known about the feeding behavior of hematophagous insects that require plant sugar to complete their life cycles. We studied plant feeding of Lutzomyia longipalpis sand flies, known vectors of Leishmania infantum/chagasi parasites, in a Brazilian city endemic with visceral leishmaniasis. The DNA barcode technique was applied to identify plant food source of wild-caught L. longipalpis using specific primers for a locus from the chloroplast genome, ribulose diphosphate carboxylase. DNA from all trees or shrubs within a 100-meter radius from the trap were collected to build a barcode reference library. While plants from the Anacardiaceae and Meliaceae families were the most abundant at the sampling site (25.4% and 12.7% of the local plant population, respectively), DNA from these plant families was found in few flies; in contrast, despite its low abundance (2.9%), DNA from the Fabaceae family was detected in 94.7% of the sand flies. The proportion of sand flies testing positi...

Parasites & Vectors, 2015

Background: Phlebotomus orientalis is the major vector of the intramacrophage protozoa, Leishmani... more Background: Phlebotomus orientalis is the major vector of the intramacrophage protozoa, Leishmania donovani, the etiological agent of visceral leishmaniasis (VL) in northern Ethiopia and Sudan. The objective of this study was to determine the nocturnal periodicity of P. orientalis in the VL endemic focus of Tahtay Adiyabo district, northern Ethiopia. Methods: Sandflies were collected using CDC light traps by changing collecting bags at an hourly interval from dusk to dawn for six months (January-June 2013) from outdoors (i.e. peri-domestic and agricultural fields). Sandfly specimens collected in the study were identified to species level and counted. Results: In total, 21,716 nocturnally active sandfly specimens, which belong to two genera (i.e., Phlebotomus and Sergentomyia) were collected and identified. In the collection, P. orientalis, the dominant species in the genus Phlebotomus, constituted 33.79% while Sergentomyia spp. comprised 65.44%. Analysis of data showed that activity of P. orientalis females increased from 18:00 to 24:00 hours, with a peak after midnight (24:00-03:00 hrs). Likewise, activity of parous P. orientalis females was found to be unimodal, peaking at 24-01:00 hrs. Conclusion: P. orientalis females had marked nocturnal activity, which peak after midnight. Similarly, the epidemiologically dangerous parous females generally were more active after midnight. Therefore, humans are at risk of L. donovani infections through the bite of P. orientalis possibly between midnight and dawn.

Parasites & Vectors, 2015

Background: Phlebotomus orientalis is the main sandfly vector of visceral leishmaniasis in the no... more Background: Phlebotomus orientalis is the main sandfly vector of visceral leishmaniasis in the north and northwest of Ethiopia. CDC light traps and sticky traps are commonly used for monitoring sandfly populations. However, their trapping efficiency is greatly influenced by various environmental factors including moonlight and lunar periodicity. In view of that, the current study assessed the effect of moonlight and lunar periodicity on the performance of light traps in collecting P. orientalis. Methods: Trapping of P. orientalis and other Phlebotomus spp. was conducted for 7 months between December 2012 and June 2013 using CDC light traps and sticky traps from peri-domestic and agricultural fields. Throughout the trapping periods, collections of sandfly specimens were carried out for 4 nights per month, totaling 28 trapping nights that coincided with the four lunar phases (viz., first quarter, third quarter, new and full moon) distributed in each month. Results: In total, 13,533 sandflies of eight Phlebotomus species (P. orientalis, P. bergeroti, P. rodhaini, P. duboscqi, P. papatasi, P. martini, P. lesleyae and P. heischi) were recorded. The predominant species was P. orientalis in both trapping sites and by both methods of collection in all lunar phases. A significant difference (P < 0.05) was observed in the mean numbers of P. orientalis and other Phlebotomus spp. caught by CDC light traps among the four lunar phases. The highest mean number (231.13 ± 36.27 flies/trap/night) of P. orientalis was collected during the new moon phases, when the moonlight is absent. Fewer sandflies were attracted to light traps during a full moon. However, the number of P. orientalis and the other Phlebotomus spp. from sticky traps did not differ in their density among the four lunar phases (P = 0.122). Conclusion: Results of the current study demonstrated that the attraction and trapping efficiency of CDC light traps is largely influenced by the presence moonlight, especially during a full moon. Therefore, sampling of sandflies using light traps to estimate population density and other epidemiological studies in the field should take the effect of moonlight and lunar periodicity into account on the trapping efficacy of light traps.

Acta tropica, 2014

We studied breeding sites of Phlebotomus orientalis (Diptera: Psychodidae) the vector of visceral... more We studied breeding sites of Phlebotomus orientalis (Diptera: Psychodidae) the vector of visceral leishmaniasis in northern Ethiopia. Although numbers were rather small, 165 sand flies were captured emerging from vertisol cracks. The most productive breeding sites were cracked vertisols, dry river banks and close to trees. No sand flies were caught emerging from sandy clay loam soils in peri-domestic habitats but a few were captured emerging from gaps in a stone wall. Abiotic parameters in vertisols close to trees and in open field from which P. orientalis had emerged, were compared. Soil pH was slightly alkaline and salinity was low. Organic matter contents were similar in both sites. Temperatures and RH remained relatively stable near trees from the end of the rainy season through mid dry season, yet fluctuated markedly at the shallower depth in the open field. During the rainy season, cracks in the soil were sealed resulting in significant lowering of the oxygen concentrations ne...

Transactions of the Royal Society of Tropical Medicine and Hygiene, 2011

This article appeared in a journal published by Elsevier. The attached copy is furnished to the a... more This article appeared in a journal published by Elsevier. The attached copy is furnished to the author for internal non-commercial research and education use, including for instruction at the authors institution and sharing with colleagues. Other uses, including reproduction and distribution, or selling or licensing copies, or posting to personal, institutional or third party websites are prohibited. In most cases authors are permitted to post their version of the article (e.g. in Word or Tex form) to their personal website or institutional repository. Authors requiring further information regarding Elsevier's archiving and manuscript policies are encouraged to visit:

Soil and Tillage Research, 2014

PLoS Neglected Tropical Diseases, 2014

Background: In East Africa, Phlebotomus orientalis serves as the main vector of Leishmania donova... more Background: In East Africa, Phlebotomus orientalis serves as the main vector of Leishmania donovani, the causative agent of visceral leishmaniasis (VL). Phlebotomus orientalis is present at two distant localities in Ethiopia; Addis Zemen where VL is endemic and Melka Werer where transmission of VL does not occur. To find out whether the difference in epidemiology of VL is due to distant compositions of P. orientalis saliva we established colonies from Addis Zemen and Melka Werer, analyzed and compared the transcriptomes, proteomes and enzymatic activity of the salivary glands. Methodology/Principal Findings: Two cDNA libraries were constructed from the female salivary glands of P. orientalis from Addis Zemen and Melka Werer. Clones of each P. orientalis library were randomly selected, sequenced and analyzed. In P. orientalis transcriptomes, we identified members of 13 main protein families. Phylogenetic analysis and multiple sequence alignments were performed to evaluate differences between the P. orientalis colonies and to show the relationship with other sand fly species from the subgenus Larroussius. To further compare both colonies, we investigated the humoral antigenicity and cross-reactivity of the salivary proteins and the activity of salivary apyrase and hyaluronidase. Conclusions: This is the first report of the salivary components of P. orientalis, an important vector sand fly. Our study expanded the knowledge of salivary gland compounds of sand fly species in the subgenus Larroussius. Based on the phylogenetic analysis, we showed that P. orientalis is closely related to Phlebotomus tobbi and Phlebotomus perniciosus, whereas Phlebotomus ariasi is evolutionarily more distinct species. We also demonstrated that there is no significant difference between the transcriptomes, proteomes or enzymatic properties of the salivary components of Addis Zemen (endemic area) and Melka Werer (non-endemic area) P. orientalis colonies. Thus, the different epidemiology of VL in these Ethiopian foci cannot be attributed to the salivary gland composition.

PLoS Neglected Tropical Diseases, 2012

Phlebotomine sand flies transmit Leishmania, phlebo-viruses and Bartonella to humans. A prominent... more Phlebotomine sand flies transmit Leishmania, phlebo-viruses and Bartonella to humans. A prominent gap in our knowledge of sand fly biology remains the ecology of their immature stages. Sand flies, unlike mosquitoes do not breed in water and only small numbers of larvae have been recovered from diverse habitats that provide stable temperatures, high humidity and decaying organic matter. We describe studies designed to identify and characterize sand fly breeding habitats in a Judean Desert focus of cutaneous leishmaniasis. To detect breeding habitats we constructed emergence traps comprising sand fly-proof netting covering defined areas or cave openings. Large size horizontal sticky traps within the confined spaces were used to trap the sand flies. Newly eclosed male sand flies were identified based on their un-rotated genitalia. Cumulative results show that Phlebotomus sergenti the vector of Leishmania tropica rests and breeds inside caves that are also home to rock hyraxes (the reservoir hosts of L. tropica) and several rodent species. Emerging sand flies were also trapped outside covered caves, probably arriving from other caves or from smaller, concealed cracks in the rocky ledges close by. Man-made support walls constructed with large boulders were also identified as breeding habitats for Ph. sergenti albeit less important than caves. Soil samples obtained from caves and burrows were rich in organic matter and salt content. In this study we developed and put into practice a generalized experimental scheme for identifying sand fly breeding habitats and for assessing the quantities of flies that emerge from them. An improved understanding of sand fly larval ecology should facilitate the implementation of effective control strategies of sand fly vectors of Leishmania.

Parasites & Vectors, 2013

Background: Visceral leishmaniasis (VL) known as Kala-Azar is a serious systemic disease caused b... more Background: Visceral leishmaniasis (VL) known as Kala-Azar is a serious systemic disease caused by Leishmania donovani parasites (Trypanosomatidae: Kinetoplastida). The disease is prevalent in the Indian Sub-continent, East Africa and Brazil. In Africa, the worst affected regions are in Sudan, with an estimated 15,000-20,000 cases annually and Ethiopia with 5,000-7,000 cases a year. The main vector of VL in Sudan and Northern Ethiopia is Phlebotomus orientalis, a sand fly frequently found in association with Acacia spp and Balanite spp woodlands. Methods: To optimize sampling of sand flies for epidemiological studies in remote areas we tested different means of attraction. Miniature suction traps employing 2AA batteries (3 V) were deployed in the up-draft orientation and baited with chemical light-sticks (Red, Yellow and Green), or bakers' yeast in sugar solution (emitting CO 2 and perhaps other attractants). These traps were compared with standard CDC incandescent light traps employing 6 V batteries. Trials were conducted during two consecutive years at different localities around Sheraro, a town in West Tigray, Northern Ethiopia. Results: The sand fly species composition was similar but not identical in the different locations tested with different Sergentomyia spp. predominating. Phlebotomus spp. comprised less than 1% of the catches during the first year trials (November-December 2011) but increased markedly during the second year trials performed later in the dry season at the height of the sand fly season in February 2012. Although there did not appear to be a species bias towards different light wavelengths , fermenting yeast in sugar solution attracted relatively more Phlebotomus spp. and Sergentomyia schwetzi. Conclusions: Although the standard 6 V CDC incandescent light traps captured more sand flies, lightweight (~350 g) 3 V suction traps baited with chemical light-sticks were shown to be effective means of monitoring sand flies. Such traps operated without light and baited with yeast in sugar solution caught relatively more Phlebotomus spp.

Medical and Veterinary Entomology, 2008

The control of phlebotomine sandflies (Diptera: Psychodidae), the vectors of leishmaniasis, is di... more The control of phlebotomine sandflies (Diptera: Psychodidae), the vectors of leishmaniasis, is directed mostly against adults as larvae develop in unknown or inaccessible habitats. In the current study we tested geraniol, a natural plant-derived pro duct, as a space repellent and the synthetic pyrethroid prallethrin as a diffusible insecticide. Geraniol was dispersed in the air using diffusers with an electric fan and prallethrin was evaporated using electrically heated evaporators. Both substances were tested in inhabited bedrooms and in tents. Geraniol failed to effect significant reductions in the numbers of either Phlebotomus papatasi Scopoli in rooms or Phlebotomus sergenti Parrot in tents. In laboratory experiments, geraniol proved ineffective in preventing sandflies from feeding. By contrast, prallethrin was highly effective in reducing the number of sandflies in rooms as well as in tents. Exposure of sandflies to prallethrin in laboratory experiments caused 97% mortality rates. Both prallethrin and, to a lesser extent, geraniol reduced the number of Culex mosquitoes captured in tents. Electric liquid-vaporizers with 1.5% prallethrin are highly effective in protecting people from sandfly bites in confined spaces and may be useful in combating cutaneous leishmaniasis.

Medical and Veterinary Entomology, 2011

Mosquitoes foraging for blood sources normally fly relatively close to the ground where wind velo... more Mosquitoes foraging for blood sources normally fly relatively close to the ground where wind velocities do not exceed their flight speed. An experiment designed to block foraging mosquitoes from reaching inhabited houses was conducted in a rural settlement flanked by agricultural fields. Mosquitoes were collected during 9 nights using 30 carbon dioxide-baited traps deployed along the external walls of six houses in the row closest to the settlement's perimeter fence. Thereafter, a deltamethrin-impregnated mesh was draped along 400 m of the perimeter fence to a height of 2 m opposite three of the monitored houses. Mosquitoes were trapped for a further 11 nights. A significant difference in the numbers of mosquitoes caught before and after the intervention was demonstrated near protected houses, whereas no significant difference was observed in catches near control houses. The percentage of Culex perexiguus (Diptera: Culicidae), an important vector of West Nile virus, was significantly lower near protected houses (13%) than around control houses (45%). By contrast, the percentage of Culex pipiens was not significantly affected (16% at experimental and 18% at control houses). Although the results presented here are preliminary, the data demonstrate the potential efficacy of vertical insecticidal barriers for mosquito control.

Journal of Vector Ecology, 2011

A number of mosquito species avoid predator-inhabited oviposition sites by detecting predator-rel... more A number of mosquito species avoid predator-inhabited oviposition sites by detecting predator-released kairomones. In the laboratory, we found that when offered de-ionized water and de-ionized water conditioned with Notonecta maculata, gravid Anopheles gambiae females preferentially oviposited into the former. We then conducted further experiments using two chemical components found in Notonecta-conditioned water, chemically pure n-tricosane and/or n-heneicosane, that was previously shown to repel oviposition by Culiseta longiareolata. These hydrocarbons failed to deter oviposition by An. gambiae females. Thus, different mosquito species may rely on distinct chemical cues to avoid predators. Identification and chemical characterization of such kairomones could facilitate innovative, environmentally sound mosquito control.