Sand Fly Vector Research Articles

A comprehensive review of biological and genetic control approaches for leishmaniasis vector sand flies; emphasis towards promoting tools for integrated vector management.

Leishmaniasis is a health problem in many regions with poor health and poor life resources. According to the World Health Organization (WHO), an estimated 700,000-1 million new cases arise annually. Effective control of sand fly vector populations is crucial for reducing the transmission of this disease. Therefore, this review aims to comprehensively examine and evaluate the current methods for controlling sand fly populations, focusing on biological and gene drive techniques. A detailed, comprehensive literature search was carried out using databases including Google Scholar, PubMed, ScienceDirect, and the National Library of Medicine (NIH). These searches were done using specific keywords related to the field of study. This current review identified several promising methods, including genetically modified sand flies, using transgenic approaches by taking advanced gene editing tools like Clustered Regularly Interspaced Short Palindromic Repeats (CRISPR/Cas9) and genetic modification of symbiotic microorganisms for controlling sand fly populations, which appeared to be proven under laboratory and field settings. Genetic control approaches have many benefits over chemical control, including long-lasting effects on targets, high specificity, and less environmental impact. Advances in genetic engineering technologies, particularly CRISPR/Cas9, sterile insect techniques, and gene drive insect modification, offer new avenues for precise and efficient sand fly management. Future research should prioritize optimizing rearing and sterilization techniques, conducting controlled field trials, and fostering collaboration across disciplines to realize the potential of genetic control strategies in combating leishmaniasis.

Management of Canine Leishmaniasis and the Treatment Trends of Veterinarians in Aegean Region of Türkiye: A Questionnaire-based Survey.

Canine leishmaniasis (CanL) is an important veterinary and public health problem in Mediterranean countries. Although CanL and vector sandflies are widespread in the study area, there are no standardized diagnostic and treatment methods followed by private clinics. This study aimed to survey (i) the treatment, diagnosis, and control measures preferred by veterinarians, (ii) compare the differences in the first-step diagnostic tests applied, and (iii) identify differences in the guidance for CanL. This study was conducted between August 2017 and 2019, and an accessible weblink was distributed to veterinary clinics that were registered with the Veterinary Affairs of İzmir. The questionnaire was prepared by following published guidelines and several CanL guidelines and comprised 13 questions. A total of 103 veterinarians voluntarily participated in the study and completed the questionnaire. Most of the clinicians (n=99; 96.1%) reported that localized alopecia was one of the most common clinical findings in the suspicion of CanL, while only four clinician did not consider this finding in the suspicion of CanL. According to the answers received, 41 clinician (39.8%) frequently observed this finding in CanL-suspected cases, 49 clinician (47.6%) observed it occasionally, and nine clinician (8.7%) rarely observed this finding. The findings of the study indicate that a minority of clinicians employ advanced diagnostic techniques. The results demonstrate that veterinarians play a unifying role in the fight against CanL. However, the preference for less advanced diagnostic methods over those employed by their European counterparts may result in insufficient detection of particularly asymptomatic patients. It is therefore necessary to validate rapid diagnostic tests, which are the most used method for diagnosing the disease. Furthermore, there is a need to increase awareness of the disease among patient owners and veterinarians in regions where it is endemic, and to recognise it as a notifiable disease in Türkiye.

Land use and cover changes and sand fly (Diptera: Psychodidae) assemblages in an emerging focus of leishmaniasis.

Land use and cover changes lead to fragmentation of the natural habitats of sand flies and modify the epidemiological profile of leishmaniasis. This process contributes to the infestation of adjacent rural settlements by vector sand fly species with different degrees of adaptation, promoting leishmaniasis outbreaks. This study aimed to assess land use and cover changes over a 12-year period and investigate the diversity and abundance of sand fly assemblages in the rural area of Codó, Maranhão State, Brazil. Temporal analysis of land use and cover changes was conducted using Sentinel-2 satellite imagery treated in QGIS software (free version 3.10) and classified using Orfeo Toolbox. Sand flies were sampled in alternate months between August 2022 and June 2023 using Centers for Disease Control and Prevention (CDC) light traps and white and black Shannon traps installed in peridomestic and extradomestic environments. Map images showed that the predominant land covers in 2012 and 2014 were dense and sparse vegetation, with few buildings. In 2021 and 2023, areas of sparse and dense vegetation were fragmented as new settlements were established. The entomological survey resulted in the capture of 3375 sand flies (CDC = 856, white Shannon = 650, black Shannon = 1969) belonging to 20 species. The most abundant species were Psychodopygus wellcomei Fraiha, Shaw & Lainson, 1971 (78.19%), followed by Nyssomyia whitmani (Antunes & Coutinho, 1939) (7.53%). Additionally, Ny. whitmani was the most abundant species (84.97%) in peridomestic environments, whereas Ps. wellcomei was the most abundant species (96.51%) in extradomestic environments. The sand fly assemblage was highly diverse, with a high abundance of competent vectors of Leishmania spp. These findings can promote community participation in surveillance and control efforts to prevent leishmaniasis cases.

Wing geometric morphometrics is effective to separate sand fly species (Diptera, Psychodidae, Phlebotominae) related with leishmaniasis transmission in Mexico.

Nearly 32% of sand fly species recorded in Mexico are related to Leishmania transmission. A correct morphological identification of sand flies is essential to improve epidemiological and control strategies. Wing geometric morphometrics (GM) has proven to be a complementary tool for classical taxonomy, allowing us to explore variations in structure and shape between species. This study evaluated whether the use of wing morphometric traits aids to identify vector sand fly species independently of their geographic distribution. The specimens were identified morphologically using specialized keys, and the right wings were analyzed using 17 landmarks. Principal Component Analysis, Canonical Variate Analysis, and Mahalanobis distances were calculated to quantify morphological differentiation. A total of 305 specimens from nine species were analyzed. Procrustes ANOVA showed significant differences (P<0.0001) in shape and size for species, as well as significant differences across their distribution between populations of Lutzomyia cruciata (P<0.0001) and Psathyromyia shannoni (P<0.0001), respectively. The use of GM tools was effective to separate species at interspecific and intraspecific level, evidencing population differences in vector sand fly species that could favor the transmission of Leishmania.

Single-cell atlas of Leishmania development in sandflies reveals the heterogeneity of transmitted parasites and their role in infection

Sandfly vectors transmit Leishmania through egestion of parasites into the host skin. The transmissible dose is shaped by Leishmania development in the sandfly gut, described as a sequential differentiation of promastigote morphotypes. Apart from isolated mammal-infective metacyclic promastigotes, little is known about the transcriptional programs and molecular markers for other stages coinhabiting the midgut in mature infections and cotransmitted by the sandfly bite. Here, we elucidate the single-cell transcriptomic complexity of Leishmania major colonizing its natural vector Phlebotomus duboscqi at early and late infection, providing markers for three transmissible stages. Contrary to prevailing models, our analyses indicate a nonlinear developmental progression, with bifurcation into either replicating early metacyclics or attached and detached haptomonads. We demonstrate that haptomonads constitute a key component of the transmitted inoculum and, along with nondividing late metacyclics, are infectious to and exacerbate the pathology in mice. Our single-cell analysis and validated markers will facilitate further studies on the Leishmania life cycle and its implications for vector-to-host transmission dynamics.

An Epidemiological Analysis of Leishmaniasis in Dhamar Governorate (2011–2013), Northern of Yemen

Over the past few years,Dhamar Governorate in North Yemen has seen an increase in leishmaniasis cases.The current study aims to assess the epidemiological profile, namely the spatiotemporal tracking of all leishmaniasis cases,and provides an epidemiological overview of the local population.This review focuses on leishmaniasis cases that were documented from 2011 to 2013. To analyze the data, Excele software (version 20) was utilized.There were 759 instances of leishmaniasis over a three-year period, from 2011 to 2013, with 94.99% of cases being cutaneous and 5.01% being mucocutaneous. There are between 0.97564276 and 0.05818674 cases of leishmaniasis in the Governorate of Dhamar. For every type of leishmaniasis, the male sex was more affected than the female sex.Cutaneous leishmaniasis had a major effect on all age groups: patients aged 0–10 made up 54.94% of cases, while those aged 11–20 made up 28.15%.Mucocutaneous leishmaniasis has primarily affected aged [0–10] with 86.84% of cases.Geographically,the Anss region recorded the highest number of leishmaniasis cases (107 cases), followed by Maghrib Ans (29 cases) and Utmah (53 cases).Thus, leishmaniasis is a major health risk in Dhamar Governorate. To stop the disease's spread, all concerned parties must move fast to set up a regional control program. and additional research on the dynamics and ecology of sandfly vectors.

A systematic review and meta-analysis of the prevalence of Leishmania infantum in sandflies in Iran

Objective: To determine the overall and pooled prevalence of Leishmania (L.) infantum in sandfly vectors in Iran. Methods: The present research conducted a systematic review and meta-analysis and searched regional databases such as PubMed, Scopus, Web of Science (WoS), Embase, PAHO Iris, LILACS, WHO Iris, and local databases named: SID, Magiran, Civilica, and also grey literatures. The current research included studies that were conducted in Iran and examined L. infantum in different sandfly vectors. The studies’ quality assessment/risk of bias assessment was evaluated by the Joanna Briggs Institute Critical Appraisal Checklist for prevalence data studies, and the data were analyzed by Stata 14 software. In addition, we examined 22 primary studies to estimate the overall prevalence of L. infantum among various vectors of visceral leishmaniasis. Results: According to the meta-analysis, the pooled prevalence of Phlebotomus (Ph.) tobbi, Ph. alexandri, Ph. kandelaki, Ph. perfiliewi, Ph. major, Ph. keshishiani were 5.34%, 4.36%, 2.23%, 1.79%, 4.37% and 1.18%. Ph. tobbi has the highest infection rate (25.00%) of L. infantum among the sandfly vectors. Conclusions: Visceral leishmaniasis is widespread in Fars, Ardebil, and East-Azerbaijan provinces, which are the most important endemic regions in Iran.

Cutaneous leishmaniasis in British troops following jungle training in Belize: Cumulative incidence and potential risk practices

BackgroundBritish soldiers undergoing jungle training in Belize typically experience a relatively low risk of developing cutaneous leishmaniasis. However, an uncharacteristically large outbreak of cutaneous leishmaniasis occurred in 2022. This study aimed to determine the cumulative incidence of the disease and highlight potential shortcomings in personal protective measures to mitigate exposure to sand fly vector bites. MethodsA retrospective analysis was conducted on medical records of cutaneous leishmaniasis cases between 2005 and 2022, as well as on questionnaire responses regarding personal protective measures administered to cutaneous leishmaniasis cases in 2022. Data were sourced from Defence Public Health Unit, Military Environmental Health Department and British Army Training Support Unit Belize. ResultsEighty-one confirmed clinical cutaneous leishmaniasis cases were recorded between 2005 and 2022, with a substantial peak (38 cases) in 2022. Most cases occurred during the wet season. Pre-2022, the median cumulative incidence per 8-week deployment was 0.90 % (Q1–Q3: 0.34 %–1.34 %), with an annual variation of 0.2 % to 2.0 %. In 2022, the cumulative incidence spiked to 4.22 %, associated with a risk ratio of 5.3 (95 % C.I.s, 3.41, 8.16), and rising to a cumulative incidence of 7.3 % in a single unit of 450 men (33 cases) in late 2022. These values are significantly higher than the median cumulative incidence of all previous years, and to published reports for other cutaneous leishmaniasis -endemic regions. Troop responses identified limitations in the supply of optimal equipment, and in sand fly bite and leishmaniasis risk avoidance information provided by the pre-deployment health education programme. Compliance with health education advise was also suboptimal, with irregular use of insect repellents, protective clothing / head netting, and insecticide-treated hammocks. ConclusionsThe reasons behind the unusually high numbers of cutaneous leishmaniasis cases and cumulative incidence in 2022 remain unclear, emphasising the need to improve personal protective measures provision and implement a comprehensive health education programme for troops undergoing jungle training in Belize.

Toscana virus - an emerging Mediterranean arbovirus transmitted by sand flies.

Toscana virus (TOSV) is an emerging arthropod-borne virus (arbovirus) of medical importance that is increasing its range across much of the Mediterranean Basin, Europe and the Middle East. Transmitted by Phlebotomus spp. sand flies, it is the most clinically relevant sand fly-borne phlebovirus. Initially isolated in the Tuscany region of Central Italy, it has now been detected in multiple countries that surround this geographical area. Infection of the vertebrate host can cause fever and neurological disease, following the dissemination of the virus to the brain. The prevalence is high in some regions, with a notable percentage of individuals showing seroconversion. TOSV can be a leading cause of acute meningitis and encephalitis (AME) during the summer months. In this comprehensive review, we will focus on several key topics. We discuss how TOSV has spread to establish outbreaks of infection in both humans and animals around the Mediterranean and the wider region. Clinical aspects of TOSV infection in humans are described, along with the best standards in diagnosis. Finally, we focus our discussion on the role of the sand fly vector, describing their biology, vector competency, implications for putative vertebrate reservoirs, the effect of the climate emergency on sand fly distribution and the putative role that sand fly-derived salivary factors may have on modulating host susceptibility to TOSV infection.

Leishmaniasis in Humans and Animals: A One Health Approach for Surveillance, Prevention and Control in a Changing World.

Leishmaniasis is classified as a neglected tropical disease (NTD), caused by protozoan parasites of the genus Leishmania, which are transmitted to humans and other animals through the bite of infected female phlebotomine sandflies. There are three forms of the disease: cutaneous leishmaniasis (CL) manifested by ulcers and scars; systemic or visceral leishmaniasis (VL), which can lead to life-threatening complications if left untreated; and mucocutaneous leishmaniasis (MCL), which can destroy the mucous membranes of the nose, mouth and throat. Human leishmaniasis is endemic in many countries across Africa, Asia, Southern Europe, the Middle East, and Central and South America. The interconnection of environmental, animal and human health underlies the spread of the Leishmania parasite. Environmental disruptions, such as climate change, deforestation or urbanisation, but also globalisation and migration, significantly affect the distribution and abundance of sand fly vectors and reservoir hosts. Climate change alters the breeding patterns of sandflies and expands their geographic range; deforestation and misuse of large areas disrupt ecosystems, leading to increased human-vector contact; and urbanisation increases the potential for contact between parties, particularly in densely populated areas. Migration of humans and animals, either through natural migration or, for example, the pet trade and breeding, can facilitate the spread of Leishmania parasites. In addition, socio-economic factors, including poverty and lack of access to healthcare, increase the burden of leishmaniasis in vulnerable populations. Due to this multitude of reasons, the geographic distribution of sandflies has expanded to higher latitudes and altitudes in recent years, with a consequent increase in disease burden. Indeed, despite ongoing challenges in the surveillance systems, data from the last available year have shown an increase in many cases in both humans and dogs. This perspective explores the interconnected factors influencing the spread of leishmaniasis worldwide and the epidemiology of the disease. In addition, it illustrates the importance of integrated strategies in a One Health approach: surveillance, prevention and control of vectors, animals and humans.

Comparative Proteogenomic Approaches for Mapping the Global Proteome of the Unsequenced Leishmania Vector Phlebotomus papatasi.

The rapid improvements in next-generation sequencing technologies have made it possible to quickly access in-depth genome sequence data. This has resulted in a flurry of genome sequences of various organisms being published and made publicly available in the last two decades. However, not all organisms have genome sequence data available. Various factors play a role, such as the importance of the organism, either medically or economically, and the genome complexity of the organisms. Phlebotomus papatasi is the sandfly vector for the Leishmania parasite, which is the causative agent for leishmaniasis. P. papatasi is a hematophagous vector, and the female flies feed on human blood to complete their reproductive cycle. The P. papatasi genome is currently being sequenced as part of a multicentric consortium, and the genome sequence is not published to date. Hence, efforts to map its global proteome are hindered in P. papatasi. In such cases, comparative proteogenomic approaches can help map the global proteome of an unsequenced organism using homology-based methods.

Stability and suitability of housekeeping genes in phlebotomine sand flies

We investigated gene expression patterns in Lutzomyia and Phlebotomus sand fly vectors of leishmaniases. Using quantitative PCR, we assessed the expression stability of potential endogenous control genes commonly used in dipterans. We analyzed Lutzomyia longipalpis and Phlebotomus papatasi samples from L3 and L4 larval stages, adult sand flies of different sexes, diets, dsRNA injection, and Leishmania infection. Six genes were evaluated: actin, α-tubulin, GAPDH, 60 S ribosomal proteins L8 and L32 (RiboL8 and RiboL32), and elongation factor 1-α (EF1-α). EF1-α was among the most stably expressed along with RiboL8 in L. longipalpis larvae and RiboL32 in adults. In P. papatasi, EF1-α and RiboL32 were the top in larvae, while EF1-α and actin were the most stable in adults. RiboL8 and actin were the most stable genes in dissected tissues and infected guts. Additionally, five primer pairs designed for L. longipalpis or P. papatasi were effective in PCR with Lutzomyia migonei, Phlebotomus duboscqi, Phlebotomus perniciosus, and Sergentomyia schwetzi cDNA. Furthermore, L. longipalpis RiboL32 and P. papatasi α-tubulin primers were suitable for qPCR with cDNA from the other four species. Our research provides tools to enhance relative gene expression studies in sand flies, facilitating the selection of endogenous control for qPCR.

Co-Infection of Cytomegalovirus and Leishmania without Splenomegaly Resulting in Immunosuppression in an Hiv-Negative Patient.

Leishmaniasis is caused by the parasite Leishmania donovani and transmitted by the bite of the sand fly vector Phlebotomus. This disease is endemic in the Bihar region of India. There are three common forms of the disease - cutaneous, mucosal and visceral leishmaniasis. The most common presentation of this disease is prolonged unexplained fever with hepatosplenomegaly. We report an unusual case of pyrexia of unknown origin (PUO) in a patient who was extensively worked up for PUO. She was found to have low CD4 counts even though serial samples were negative for HIV. Workup for PUO revealed a positive result for cytomegalovirus (CMV) IgM and polymerase chain reaction (PCR), fundoscopy suggestive of CMV retinitis and bone marrow biopsy suggestive of visceral leishmaniasis. Interestingly, there was no evidence of hepatosplenomegaly. She was diagnosed as a case of CMV infection and visceral leishmaniasis resulting in immunosuppression and was managed with parenteral ganciclovir followed by oral valganciclovir and amphotericin respectively. She had a dramatic response to the treatment and was discharged after two months of in hospital management. Co-infection of CMV and Leishmania in an immunocompromised patient with HIV-negative status without hepatosplenomegaly posed a diagnostic dilemma and is a rare presentation. This report shows the importance of diagnosis of this co-infectious state, which upon management with ganciclovir and amphotericin lead to resolution of symptoms and pancytopenia. Clinicians should be aware of the unusual presentation to avoid missing the diagnosis of this potentially life-threatening treatable condition. Visceral leishmaniasis without splenomegaly is a rare presentation.Other aetiologies for low CD4 counts in an HIV-negative patient such as cytomegalovirus (CMV) should be considered.Co-infection of CMV and Leishmania resulting in immunosuppression in an HIV-negative patient is rare and poses a diagnostic dilemma.

The spatial relationship between leishmaniases and sand flies in Europe and neighboring countries

BackgroundLeishmania infantum is endemic in Europe (and elsewhere) while L. donovani s.s., L. tropica and L. major are not but are present in neighboring countries in North Africa, the Middle East, (the Asian part of) Turkey and the Southern Caucasus. Lists of sand fly vector species in the scientific literature vary with the criteria for vector incrimination, and criteria vary because, for some, evidence is difficult to generate. With minimal criteria, about 20 sand fly species are proven or suspected vectors of L. infantum in Europe and neighboring countries, while for L. tropica and L. major, there are seven and four proven or suspected vector species, respectively, in this area. For L. donovani s.s., present in Cyprus, the Middle East and (the Asian part of) Turkey, no local vectors have been incriminated so far. The aim was to assess the degree of spatial agreement between Leishmania spp. and various vectors species and their relative contribution to the explained variation.MethodsWe used multivariate regression modeling to analyze the spatial relationship between autochthonous Leishmania spp. and clinical forms in humans and animals and 14 Phlebotomus spp. in Europe and neighboring countries.ResultsThere was only fair agreement between parasite and vector distributions. The most parsimonious models describing the distribution of Leishmania spp. and clinical forms included three to six sand fly species and explained between 12% (L. infantum) and 37% (L. donovani) of the observed variation. Selected models included confirmed and suspected vector species as well as unexpected species.ConclusionsThe relatively low agreement between Leishmania and vector distributions highlights the need to improve leishmaniasis reporting and vector surveillance in areas where no information is available, both for a better understanding of the epidemiology of infection in endemic areas and to monitor possible spread of infection into non-endemic areas. While some of the unexpected sand fly-Leishmania spp. statistical associations might be spurious, for others, the existence of sporadic or recent reports of infections warrants further vector competence studies that consider strain variation.Graphical

Feline leishmaniosis in the Mediterranean Basin: a multicenter study

BackgroundCats are now recognized as competent hosts for Leishmania infantum and a blood source for sand fly vectors. Although canine leishmaniosis (CanL) is endemic in Mediterranean Basin countries, large-scale epidemiological studies are lacking for feline leishmaniosis (FeL). This study aimed to assess the prevalence of L. infantum infections, associated risk factors, clinical signs, and clinicopathological abnormalities in domestic cat populations from six Mediterranean Basin countries.MethodsFrom 2019 to 2022, blood and serum samples of cats (n = 2067) living in Italy (n = 300), Greece (n = 297), Portugal (n = 295), France (n = 231), Israel (n = 313), and Spain (n = 631) were collected along with animal data (i.e., age, sex, breed, housing conditions, and geographical origin), clinical signs, and laboratory blood test parameters. Cats were grouped according to their age as kittens (up to 1 year), young (older than 1 and younger than 7 years), mature (between 7 and 10 years), and senior (older than 10 years). Serum samples were tested for L. infantum by immunofluorescence antibody test (IFAT) and enzyme-linked immunosorbent assay (ELISA), and blood samples of seropositive cats were tested for L. infantum kinetoplast deoxyribonucleic acid (kDNA). Viral infection by feline immunodeficiency virus (FIV) and feline leukemia virus (FeLV) was molecularly addressed in all cats enrolled. Statistical analysis was performed to evaluate the association between the risk of L. infantum infection and independent variables, and among co-infection of L. infantum with FIV and/or FeLV, clinical signs, and clinicopathological abnormalities.ResultsOverall, 17.3% (358/2067) of cats scored positive for L. infantum by serological tests. Specifically, 24.7% were from Portugal, 23.2% from Greece, 16.6% from Israel, 15% from Spain, 13.3% from France, and 12.6% from Italy. Leishmania infantum DNA was detected in 15 seropositive animals. Housing condition and FIV infection proved to be risk factors for FeL. Leishmania seropositivity was significantly associated with weight loss, lymphadenomegaly, gingivostomatitis, and oral ulcers, as well as with reduced albumin and albumin/globulin ratio, increased total globulins and total proteins, leukocytosis, and thrombocytosis.ConclusionsThis study provides, for the first time, a large-scale epidemiological survey on FeL and its clinical presentation, revealing that L. infantum circulates among domestic cats, especially shelter/free-roaming and FIV-infected animals, living in CanL endemic countries of the Mediterranean Basin.Graphical

Discovery of essential kinetoplastid-insect adhesion proteins and their function in Leishmania-sand fly interactions

Leishmania species, members of the kinetoplastid parasites, cause leishmaniasis, a neglected tropical disease, in millions of people worldwide. Leishmania has a complex life cycle with multiple developmental forms, as it cycles between a sand fly vector and a mammalian host; understanding their life cycle is critical to understanding disease spread. One of the key life cycle stages is the haptomonad form, which attaches to insect tissues through its flagellum. This adhesion, conserved across kinetoplastid parasites, is implicated in having an important function within their life cycles and hence in disease transmission. Here, we discover the kinetoplastid-insect adhesion proteins (KIAPs), which localise in the attached Leishmania flagellum. Deletion of these KIAPs impairs cell adhesion in vitro and prevents Leishmania from colonising the stomodeal valve in the sand fly, without affecting cell growth. Additionally, loss of parasite adhesion in the sand fly results in reduced physiological changes to the fly, with no observable damage of the stomodeal valve and reduced midgut swelling. These results provide important insights into a comprehensive understanding of the Leishmania life cycle, which will be critical for developing transmission-blocking strategies.

Risk factors of visceral leishmaniasis in the world: a review

Visceral leishmaniasis is a zoonotic parasitic disease caused by viscerotropic Leishmania species and transmitted by bites of infected phlebotomine sandflies, which is predominantly prevalent in the Indian subcontinent, eastern Africa and South America. Currently, visceral leishmaniasis is the second most fatal parasitic disease in the world. Because of climate changes, urban development and individual conditions, there are changes in the density of visceral leishmaniasis vector sandflies and the likelihood of contact with humans, resulting in a visceral leishmaniasis transmission risk. The review summarizes natural, social and biological factors affecting the transmission of visceral leishmaniasis, so as to provide insights into formulation of targeted control measures for visceral leishmaniasis.

Trypanosoma infection and bloodmeal analysis in post-feeding sand flies across Thailand

Phlebotomine sand flies are recognized as a primary vector of Leishmania and are also suspected vectors of Trypanosoma. The transmission cycle of these parasites relies on the distribution of sand fly vectors, parasites, and reservoir animals. This study aimed to detect Leishmania and Trypanosoma DNA and identify the sources of bloodmeals in post-feeding sand flies captured across Thailand. A total of 42,911 field female sand flies were collected from 11 provinces across Thailand using CDC light traps. Among these, 253 post-feeding sand flies were selected for analysis. The predominant species in this study was Sergentomyia khawi (33.60 %). The DNA was extracted from individual female sand flies. Polymerase chain reaction (PCR), specific to the internal transcribed spacer 1 (ITS1) and the small subunit ribosomal RNA (SSU rRNA) gene regions were used to detect the presence of Leishmania and Trypanosoma DNA, respectively. Additionally, cytochrome c oxidase subunit I (COI) gene region was utilized to identify the sources of host bloodmeals. Leishmania DNA was not detected in any specimens. The analysis of SSU rRNA sequences revealed the presence of Trypanosoma DNA (11.46 %, 29/253) in sand fly samples. Among these samples, T. noyesi (1.58 %, 4/253) was identified in Idiophlebotomus longiforceps and Phlebotomus asperulus, Trypanosoma Anura01+02/Frog2 (1.18 %, 3/253) in Se. khawi, and Trypanosoma Anura04/Frog1 (8.70 %, 22/253) in Se. khawi, Se. hivernus and Grossomyia indica. Bloodmeal analysis utilizing the COI gene revealed a diverse range of vertebrate hosts’ blood, including bird, bat, frog and sun skink. Our findings confirm the presence of Trypanosoma DNA and identify the sources of bloodmeals from vertebrate hosts in various sand fly species, suggesting their potential as possible vectors for Trypanosoma in Thailand. Furthermore, our study is the first to provide molecular evidence using the COI gene to identify frogs as a host blood source for sand flies in Thailand. Further studies focusing on the isolation of live parasites in sand flies to confirm vector potential and examining the role of animal reservoirs will enhance our understanding of the host-parasite relationship and enable more efficient control for disease transmission.

Distribution and seasonal fluctuation of visceral leishmaniasis vectors sandflie in Lüliang City of Shanxi Province in 2023

To investigate the distribution and seasonal fluctuations of visceral leishmaniasis vectors sandflies in Lüliang City, Shanxi Province, so as to provide insights into assessment of the visceral leishmaniasis transmission risk and formulation of visceral leishmaniasis control measures. A total of 12 natural villages were sampled from Shilou County, Lishi District, Lanxian County, Linxian County and Wenshui County in Lüliang City, Shanxi Province from June to September, 2023, and sandflies were captured using light traps from 7 breeding habitats, including farmers' houses, sheep pens, cattle pens, chicken coops, pig pens, mule and horse pens, and loess-cave dwellings. Following morphological identification of the sandfly species, the distribution of sandflies and the seasonal fluctuations of the sandfly density were analyzed. In addition, the Leishmania was detected in sandflies using a real-time fluorescence quantitative PCR assay. A total of 2 831 sandflies were captured with 156 light traps in Lüliang City from June to September, 2023, including 2 638 female sandflies (93.18%) and 193 male sandflies (6.82%), and the average density was 16.91 sandflies/(light-night). The seasonal fluctuations of the sandfly density all appeared a unimodal distribution in all survey sites, and the sandfly density peaked in July and then declined rapidly. Among all types of breeding habitats, the greatest sandfly density was found in sheep pens [39.04 sandflies/(light-night)]. In addition, 4.08% (2/49) of the sandfly samples were tested positive for Leishmania nucleic acid as revealed by the real-time fluorescence quantitative PCR assay. Sandflies were widely distributed in Lüliang City, Shanxi Province in 2023, and the peak of the sandfly density was observed in July, which had a visceral leishmaniasis transmission risk. Intensified surveillance of visceral leishmaniasis and sandfly vectors is required and targeted vector control is recommended.

Comparative Analysis of Phlebotomus argentipes Vector of Leishmaniasis in India and Sri Lanka.

Phlebotomus argentipes is the predominant sandfly vector of leishmaniasis in the Indian subcontinent. India and Sri Lanka primarily report visceral and cutaneous leishmaniasis caused by Leishmania donovani. We compared Ph. argentipes from two locations, focusing on its morphological, molecular, and salivary protein characteristics. Sandflies were captured using CDC light traps and cattle-baited net traps. Species identification and morphological comparisons were carried out using standard taxonomic keys. DNA extracted from 12 Sri Lankan sandfly samples was PCR-amplified and sequenced for the variable region of Cytochrome oxidase subunit I. Existing DNA sequences of India from GenBank were utilized for a phylogenetic analysis between Sri Lanka and India. Salivary protein profiles were studied using SDS-PAGE, Western blot, and electrospray ionization/LC/MS/MS. The morphological similarities observed between female Ph. argentipes from India and Sri Lanka suggest the presence of Ph. argentipes var. glaucus. A phylogenetic analysis showed genetic divergence between Ph. argentipes populations, but both shared a similar salivary protein profile. A common, strong 30 kDa immunogenic band comprised PagSP05, PagSP06, and PagSP17 proteins of Ph. argentipes. The similarity between the immunogenic salivary proteins suggests their potential use as common markers for vector exposure or immune response stimulants across regions. The use of multiple samples for each category of serum would improve the comprehensiveness of the immunogenic profiles obtained.