Insect vector
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Host infectiousness to insect vectors is a crucial parameter for understanding the transmission dynamics of insect-borne infectious diseases such as leishmaniases. Despite their importance, critical factors influencing the outwards transmission of Leishmania major, including parasite distribution within the host body and the minimum number of skin amastigotes required for vector infection, remain poorly characterized. To address these gaps, we studied these parameters in the natural North African reservoir host Meriones shawi and in BALB/c mice infected with a low parasite dose. Using qPCR, we quantified Leishmania loads in different zones (regions) of infected ear pinnae, whereas microscale infectiousness was evaluated via microbiopsies and fluorescence microscopy. The amastigote distribution within infected ears was heterogeneous, with pronounced differences between the lesion center, lesion margin, and visually unaffected surrounding skin. Phlebotomus papatasi females that fed in areas where no amastigotes were detected via microscopy did not become infected. In M. shawi, lesion margins have emerged as the most effective source of infection. The number of amastigotes at bite sites where sand fly females became infected ranged from 4--500, with as few as 2--10 amastigotes sufficient to initiate vector infection. This low infection threshold was confirmed by experiments in which P. papatasi was fed through a chick-skin membrane. In contrast, the BALB/c mouse model showed only minor differences in infectiousness between lesion centers and margins. The minimum infectious dose in BALB/c mice was approximately 100 times greater than that in M. shawi, with successful infections occurring at sites containing 1,500-10,000 amastigotes. These findings advance our understanding of Leishmania transmission by addressing critical knowledge gaps and enabling more accurate modelling of cutaneous leishmaniasis epidemiology. Moreover, this study highlights the importance of incorporating natural host models in research, as the dynamics of disease progression and transmission parameters can differ significantly between natural hosts and standard laboratory models.
- MeSH
- Gerbillinae * parazitologie MeSH
- hmyz - vektory * parazitologie MeSH
- kůže parazitologie MeSH
- Leishmania major * fyziologie patogenita MeSH
- leishmanióza kožní * přenos parazitologie MeSH
- modely nemocí na zvířatech MeSH
- myši inbrední BALB C MeSH
- myši MeSH
- parazitární zátěž MeSH
- Phlebotomus * parazitologie MeSH
- zdroje nemoci * parazitologie MeSH
- zvířata MeSH
- Check Tag
- myši MeSH
- ženské pohlaví MeSH
- zvířata MeSH
- Publikační typ
- časopisecké články MeSH
Zoonózy se každoročně v České republice významně podílejí na počtu hlášených infekčních onemocnění. Stoupající tendence výskytu zoonotických virů, jako je virus zika virus, virus horečky dengue, virus chikungunyi a virus západonilské horečky, přenášených invazivními tropickými druhy komárů, je v první řadě důsledkem dlouhodobého, postupného a prakticky nezastavitelného šíření tohoto hmyzu po evropském kontinentu, včetně severských států. Evropa nyní již pravidelně zažívá opakované každoroční vlny veder, stejně jako časté záplavy. Navyšuje se nejen počet letních dnů s tropickými teplotami, ale období léta jako takového se významně prodlužuje. Stírají se jarní a podzimní období, rychlost nástupu letních teplot po období zim je často až drastická. Tento proces navozuje příznivé životní podmínky pro etablování tropických druhů komárů na našem území. Například ještě v roce 2013 se invazivní druh komára Aedes albopictus, původem z Asie, vyskytoval „pouze" v osmi evropských zemích a zasaženo bylo 114 regionů. O pouhých deset let později byl jeho výskyt potvrzen již ve třinácti zemích a 337 oblastech, včetně České republiky. Tento trend bude pokračovat, je proto nutné očekávat nárůsty autochtonních infekcí, včetně komplikovaných průběhů infekcí a úmrtí, obzvláště v rizikových skupinách rychle stárnoucí evropské populace. Kromě nutnosti hledat nové způsoby kontroly populací komárů, vývoje nových desinsekčních a larvicidních chemikálií je třeba zásadně posilovat programy surveillance napříč spolupracující Evropou, prosazovat používání osobních ochranných pomůcek a jednoznačně posílit výzkum a vývoj specifických antivirotik a nových očkovacích látek.
Zoonoses contribute significantly to the number of reported infectious diseases in the Czech Republic each year. The rising trend in zoonotic viruses such as Zika virus, dengue virus, Chikungunya virus, West Nile virus, transmitted by invasive tropical mosquito species, is primarily due to the long-term, gradual and virtually unstoppable spread of these insects across the European continent, including the Nordic countries. Europe now regularly experiences recurrent annual heat waves as well as frequent flooding. Not only are the number of summer days with tropical temperatures increasing, but the summer period itself is being significantly extended. The spring and autumn seasons are becoming shorter, and the speed of the onset of summer temperatures after winter is often drastic. This process creates favorable living conditions for the establishment of tropical mosquito species in our territory. For example, as recently as 2013, the invasive mosquito species Aedes albopictus, native to Asia, was present in "only" eight European countries and 114 regions were affected. In 2023, its presence has already been confirmed in thirteen countries and 337 regions, including the Czech Republic. This trend is set to continue, so increases in autochthonous infections, including complicated infection patterns and deaths, are to be expected, especially in at-risk groups of the rapidly ageing European population. In addition to the need to find new ways of controlling mosquito populations, the development of new disinsecticidal and larvicidal chemicals, surveillance programs across a cooperating Europe need to be substantially strengthened, the use of personal protective equipment needs to be promoted, and research and development of specific antivirals and new vaccines needs to be clearly stepped up.
- Klíčová slova
- tropičtí komáři,
- MeSH
- Culicidae MeSH
- infekce virem zika epidemiologie přenos terapie MeSH
- komáří přenašeči * MeSH
- lidé MeSH
- virus zika * izolace a purifikace účinky léků MeSH
- zoonózy * epidemiologie přenos terapie MeSH
- Check Tag
- lidé MeSH
- Publikační typ
- práce podpořená grantem MeSH
- Geografické názvy
- Evropa MeSH
Toscana virus (TOSV) is an emerging but neglected human pathogen currently circulating around the Mediterranean basin including North Africa. Human illness ranges from asymptomatic or mild flu-like syndromes to severe neurological diseases such as meningitis or meningoencephalitis. Despite its significant impact, understanding of TOSV transmission and epidemiology remains limited. Sand flies (Diptera: Phlebotominae), specifically Phlebotomus perniciosus and Phlebotomus perfiliewi, are believed to be the primary vectors of TOSV. However, the spread of TOSV to new geographical areas and its detection in other sand fly species suggest that additional species play a role in the circulation and transmission of this virus. This study investigated the vector competence of four sand fly species - P. tobbi, P. sergenti, P. papatasi, and Sergentomyia schwetzi - for two TOSV strains: 1500590 (TOSV A lineage) and MRS20104319501 (TOSV B lineage). Sand flies were orally challenged with TOSV via bloodmeals. None of the tested species showed susceptibility to the TOSV A strain. However, for TOSV B strain, P. tobbi demonstrated a high potential as a new vector, exhibiting high infection and dissemination rates. P. sergenti also showed some susceptibility to TOSV B, with the virus dissemination observed in all infected females. These finding suggests that P. tobbi and P. sergenti are new potential vectors for TOSV B. Given that P. tobbi and P. sergenti are the primary vectors of human leishmaniases in the Balkans, Turkey and Middle East, their susceptibility to TOSV could have significant epidemiological consequences. On the other hand, P. papatasi and S. schwetzi appeared refractory to TOSV B infection. Refractoriness of P. papatasi, a highly anthropophilic species distributed from the Mediterranean to the Middle East and India, suggests that this species does not contribute to TOSV circulation.
Phlebotomine sand flies (Diptera: Psychodidae: Phlebotominae) are the principal vectors of Leishmania spp. (Kinetoplastida: Trypanosomatidae) worldwide. The subgenus Adlerius is taxonomically challenging and currently comprises about 20 species with a wide geographic distribution from eastern Asia to southeastern Europe. Some species are confirmed or suspected vectors of Leishmania donovani/infantum, L. major, and L. tropica, and are thus of high medical and veterinary relevance. A single record of Phlebotomus (Adlerius) simici in Austria from 2018 marks its sporadic northernmost and westernmost occurrence, with the origin of its appearance remaining unclear. To better understand Adlerius diversification and particularly post-glacial spread of Ph. simici to northern parts of Europe, we combined phylogenetic analyses with climatic suitability modelling. Divergence time estimates well supported the currently observed geographic distribution of the studied species and revealed several taxonomic challenges in the subgenus. We clearly delineated three distinct genetic and geographic Ph. simici lineages and phylogeographically assessed diversification that were well supported by climatic models. This study provides a comprehensive phylogenetic analysis of the subgenus Adlerius, enhancing our understanding of the diversification in relation to changing climate of this understudied group, and we present new insights into the post-glacial spread of Ph. simici, a suspected vector of L. infantum.
- MeSH
- fylogeneze * MeSH
- fylogeografie * MeSH
- hmyz - vektory genetika klasifikace MeSH
- Phlebotomus * klasifikace genetika MeSH
- podnebí MeSH
- zvířata MeSH
- Check Tag
- zvířata MeSH
- Publikační typ
- časopisecké články MeSH
- Geografické názvy
- Evropa MeSH
The olfactory response of insect vectors such as phlebotomine sand flies is a key facet for investigating their interactions with vertebrate hosts and associated vector-borne pathogens. Such studies are mainly performed by assessing the electrophysiological response and the olfactory behaviour of these arthropods towards volatile organic compounds (VOCs) produced by hosts. Nonetheless, few studies are available for species of the subgenera Lutzomyia and Nyssomyia in South America, leaving a void for Old World sand fly species of the genus Phlebotomus. In this study, we evaluated the olfactory responses of Phlebotomus perniciosus, one of the most important vectors of Leishmania infantum in the Old World. To test the P. perniciosus behavioural response to VOCs, 28 compounds isolated from humans and dogs were assessed using electrophysiological (i.e., electroantennogram, EAG) and behavioural assays (i.e., Y-tube olfactometer). In the EAG trials, 14 compounds (i.e., acetic acid, nonanoic acid, 2-propanol, 2-butanol, pentanal, hexanal, nonanal, trans-2-nonenal, decanal, myrcene, p-cymene, verbenone, 2-ethyl-1-hexanol, and acetonitrile) elicited high antennal responses (i.e., ≥ 0.30 mV) in female sand flies, being those VOCs selected for the behavioural assays. From the 14 compounds tested in the Y-tube olfactometer, nonanal was significantly attractive for P. perniciosus females, whereas myrcene and p-cymene were significantly repellents (p < 0.05). The attraction indexes varied from 0.53 for nonanal (i.e., most attractive) to -0.47 to p-cymene (i.e., most repellent). Overall, our results shed light on the role of olfactory cues routing host seeking behaviour in P. perniciosus, with implications to develop sustainable sand fly monitoring as well as control in leishmaniasis endemic areas.
- MeSH
- chování zvířat účinky léků MeSH
- hmyz - vektory fyziologie účinky léků MeSH
- Leishmania infantum účinky léků fyziologie MeSH
- lidé MeSH
- Phlebotomus * fyziologie účinky léků MeSH
- psi MeSH
- těkavé organické sloučeniny * farmakologie chemie analýza MeSH
- zvířata MeSH
- Check Tag
- lidé MeSH
- mužské pohlaví MeSH
- psi MeSH
- ženské pohlaví MeSH
- zvířata MeSH
- Publikační typ
- časopisecké články MeSH
BACKGROUND: Several new species of Leishmania have recently emerged in Europe, probably as the result of global changes and increased human migration from endemic areas. In this study, we tested whether two sand fly species, the Western Mediterranean Phlebotomus perniciosus and the Eastern Mediterranean P. tobbi, are competent vectors of L. donovani, L. major and L. martiniquensis. METHODOLOGY/PRINCIPAL FINDINGS: Sand flies were infected through the chick skin membrane using Leishmania species and strains of various geographical origins. Leishmania infections were evaluated by light microscopy and qPCR, and the representation of morphological forms was assessed from Giemsa-stained gut smears. Neither P. perniciosus nor P. tobbi supported the development of L. martiniquensis, but L. major and L. donovani in both species survived defecation of blood meal remnants, colonized the stomodeal valve and produced metacyclic stages. The results with L donovani have shown that infection rates in sand flies can be strain-specific; therefore, to determine vector competence or refractoriness, it is optimal to test at least two strains of Leishmania. CONCLUSIONS, SIGNIFICANCE: Both sand fly species tested are potential vectors of L. donovani and L. major in Mediterranean area. However, further studies will be needed to identify European vectors of L. martiniquensis and to test the ability of other European sand fly species to transmit L. major, L. donovani, L. tropica and L. infantum.
- MeSH
- hmyz - vektory * parazitologie fyziologie MeSH
- kur domácí parazitologie MeSH
- Leishmania * fyziologie klasifikace genetika MeSH
- leishmanióza přenos parazitologie MeSH
- lidé MeSH
- Phlebotomus * parazitologie fyziologie MeSH
- zvířata MeSH
- Check Tag
- lidé MeSH
- ženské pohlaví MeSH
- zvířata MeSH
- Publikační typ
- časopisecké články MeSH
- Geografické názvy
- Evropa MeSH
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.
- MeSH
- esenciální geny * MeSH
- hmyz - vektory genetika MeSH
- hmyzí geny MeSH
- larva genetika MeSH
- Leishmania genetika MeSH
- Phlebotomus * genetika MeSH
- Psychodidae genetika MeSH
- stanovení celkové genové exprese metody MeSH
- zvířata MeSH
- Check Tag
- mužské pohlaví MeSH
- ženské pohlaví MeSH
- zvířata MeSH
- Publikační typ
- časopisecké články MeSH
Sand flies (Diptera: Psychodidae: Phlebotominae) are blood-feeding insects that transmit the protozoan parasites Leishmania spp. and various arboviruses. The Balkan region, including the Republic of Kosovo, harbours a diverse sand fly fauna. Vector species of Leishmania infantum as well as phleboviruses are endemic; however, recent data are scarce. We performed a cross-sectional study to update the current sand fly distribution in Kosovo and assess biological as well as environmental factors associated with sand fly presence. CDC light trapping was conducted at 46 locations in 2022 and 2023, specifically targeting understudied regions in Kosovo. Individual morphological species identification was supported by molecular barcoding. The occurrence data of sand flies was used to create distribution maps and perform environmental analyses, taking elevation, wind speed and climate-related factors into account. In addition, PCR-based blood meal analysis and pathogen screening were conducted. Overall, 303 specimens of six sand fly species were trapped, predominated by Phlebotomus neglectus (97%). Barcodes from eight of nine known endemic sand fly species were obtained. Combining our data with previous surveys, we mapped the currently known sand fly distribution based on more than 4000 specimens at 177 data points, identifying Ph. neglectus and Ph. perfiliewi as the predominant species. Environmental analyses depicted two geographical groups of sand flies in Kosovo, with notable differences between the species. In total, 223 blood meals of five sand fly species were analysed. Of seven identified host species, the predominant blood meal source was observed to be cattle, but the DNA of dogs and humans, among others, was also detected. This study assessed biological as well as ecological factors of sand fly occurrence, which should help better understand and evaluate potential hot spots of disease transmission in Kosovo.
- MeSH
- hmyz - vektory * fyziologie parazitologie MeSH
- Leishmania infantum fyziologie MeSH
- Phlebotomus * klasifikace fyziologie parazitologie MeSH
- průřezové studie MeSH
- psi MeSH
- Psychodidae fyziologie parazitologie MeSH
- rozšíření zvířat * MeSH
- zvířata MeSH
- Check Tag
- mužské pohlaví MeSH
- psi MeSH
- ženské pohlaví MeSH
- zvířata MeSH
- Publikační typ
- časopisecké články MeSH
- Geografické názvy
- Kosovo MeSH
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.
- MeSH
- buněčná adheze MeSH
- flagella * metabolismus MeSH
- hmyz - vektory parazitologie MeSH
- hmyzí proteiny metabolismus genetika MeSH
- interakce hostitele a parazita MeSH
- Leishmania * fyziologie genetika metabolismus MeSH
- leishmanióza parazitologie přenos MeSH
- protozoální proteiny metabolismus genetika MeSH
- Psychodidae * parazitologie MeSH
- stadia vývoje MeSH
- zvířata MeSH
- Check Tag
- ženské pohlaví MeSH
- zvířata MeSH
- Publikační typ
- časopisecké články MeSH
