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Experimental animal models and vectors of Leishmania (Mundinia)
Bečvář, Tomáš ; Sádlová, Jovana (advisor) ; Courtenay, Orin (referee) ; Soares Maia, Carla Alexandra (referee)
Leishmania are vector-borne dixenous protozoan parasites of vertebrates causing diseases collectively called leishmaniases, which threaten more than 1 billion people mainly in tropical and subtropical regions. These parasites are divided into four subgenera: Leishmania, Viannia, Sauroleishmania, and Mundinia. The last named are geographically widely dispersed and their distribution covers all continents except Antarctica. Although their medical and veterinary importance is increasing, there is currently almost no information on natural reservoir hosts, vector species, and experimental research options due to the very limited range of model animals. This thesis summarizes our efforts to unravel possible vectors and laboratory models for this subgenus. In the first three studies, we focused on potential models; therefore, we experimentally infected guinea pigs (Cavia porcellus), BALB/c mice, Chinese hamsters (Cricetulus griseus), and steppe lemmings (Lagurus lagurus) with five species of Mundinia and we also tested reservoir potential of African grass rat (Arvicanthis niloticus) and Natal multimammate mouse (Mastomys natalensis) to Leishmania chancei. The second part focused on potential vectors of the parasites. We experimentally infected biting midges Culicoides sonorensis and sand flies sharing...
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Sex chromosomes of Nematocera
Ryšan, Tadeáš ; Volf, Petr (advisor) ; Šťáhlavský, František (referee)
The paraphyletic group Nematocera is highly diversified in both body morphology and life strategies. Based on sex chromosome morphology, it can be divided into four groups defined as early as the mid- 20th century. All these systems are based on the presence of the XY/XX sex chromosomes or the loss of the Y chromosome. The different groups are distinguished based on whether the chromosomes are differentiated, whether chiasmata are present and whether the Y chromosome is retained. However, later research has shown much higher sex chromosome diversity, mostly in groups with homomorphic gonosomes. Even though most representatives of this group do not have differentiated sex chromosomes, we find the recurrence of differentiated gonosomes and even the X1X2Y1Y2/ X1X1X2X2 and ZW/ZZ sex systems, which are less typical for Diptera. These findings suggest that the form of sex chromosomes in Diptera may not be as stable as previously thought. The recently discovered non- homology of gonosomes across the Diptera, including several representatives of Nematocera, supports this idea. Multiple independent gonosome formation could also explain the diversity of primary sex- determining factors in those groups where these factors are known. Key words: Nematocera, Phlebotomus, Lutzomyia, sex chromosomes, sex determination
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Immunity in hosts repeatedly exposed to sand fies and the effect on pathogen transmission
Pohanková, Lucia ; Kolářová, Iva (advisor) ; Fialová, Anna (referee)
6 Abstrakt During the feeding of infected sand flies are inoculate into the host also sand fly saliva, which can strongly modulate the response of the immune system. If the host is naive, the course of infection is usually worse. In cutaneous leishmaniasis, the lesions developed early, are more destructive and persist longer. The hosts living in endemic areas of leishamniasis and their vector hosts are often exposed to feeding uninfected sand flies. For host are the saliva antigenic and induces specific cellular and antibody responses. This responses induce the protection against leishmania infection and differ for different hosts, attempts were made most frequently in murine and canine models. In humans, as hosts is difficult to monitor developments leishmania infection after previous exposure, because in humans mainly monitors the levels of antibodies, by which we can determine the degree of sand fly bites and the risk of transmission of leishmaniasis. Keywords: Lutzomyia, Phlebotomus, DTH, antibody, IgG,
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Macrophages in leishmania - sand fly - host interaction
Kratochvílová, Tereza ; Kolářová, Iva (advisor) ; Fialová, Anna (referee)
Sand flies (order Diptera) are vectors of Leishmania parasites (Trypanosomatida), which are inoculated into the host skin together with the vector saliva. Sand fly saliva plays the important role in the Leishmania transmission; in naive host it supresses the host immune response assisting Leishmania to establish the infection, while in repeatedly bitten host it elicits a protective immune response. The submitted thesis focuses on the effect of sand fly saliva on macrophages, the key cells in the infection control. In the first part of the thesis we established a laboratory model L. major - P. papatasi - Balb/c to describe the protective effect of saliva immunization on Leishmania infection development. Immunized mice were protected against Leishmania infection which was reflected in the ear lesion size, parasite load in the ear dermis and draining lymph nodes but also in cytokine production. On the contrary, produced lower amount of nitric oxide, while arginase activity was comparable with nonimmunized group. The IgG antibodies against saliva served as a marker of exposure to sandflies while IgG antibodies against Leishmania antigens served as a marker of infection severity. The experiments were aimed on the possibility of cross-protectivity in Balb/c mice against L. major between closely related...
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Chemical and biological control of phlebotominae sand flies
Pružinová, Kateřina ; Volf, Petr (advisor) ; Král, David (referee)
Phlebotominae sand flies (Diptera: Phlebotominae) are important vectors of leishmaniasis. Control measures are complicated by the fact that sand fly breeding sites and resting places are generally hard to find. Measures used to control adult sand flies include the use of chemical insecticides for insecticide-treated bednets or curtains, residual spraying of dwellings, eventually the space-spraying. Domestic dogs as reservoir host of visceral leishmaniosis can be protected by dog-collars impregnated with insecticides or by spot on application of insecticides. Chemical insecticides may be toxic for non-target organisms and the increase of insecticide-resistance of some sand flies populations is possible. Therefore, new methods of biological control should be tested; entomopathogenic organisms (Bacillus sphaericus, B. thuringiensis, Beauveria bassiana), pheromone-baited traps and noxious plants could be used. Hormone TMOF, inhibitor of trypsin biosynthesis, was successfully tested in mosquitos. Based on similarity of mosquitos and sand flies, the effect of this peptide on blood digestion and egg development is tested in Phlebotomus and Lutzomyia species.
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Effect of abiotic and biotic factors on Leishmania development in sand fly vectors
Hlaváčová, Jana ; Volf, Petr (advisor) ; Alten, Bülent (referee) ; Traub-Cseko, Yara Maria (referee)
The thesis deals with Leishmania development in sand flies focusing on factors that could affect the vectorial part of their lifecycle. First, we examined an effect of temperature on Leishmania development in sand flies since the global warming was suggested to be one of the most important factors affecting dissemination of leishmaniasis. Development of three Leishmania species were studied at two different temperatures (20 and 26řC); L. infantum in natural vectors Lutzomyia longipalpis and Phlebotomus perniciosus, and two closely related Viannia species L. braziliensis and L. peruviana in Lu. longipalpis. Leishmania peruviana thrived well only at the lower temperature tested. At the higher temperature, most of infections were lost between days 2 and 8 post feeding, i.e. time of blood-meal remnants defecation. This suggests that this Andean species is adapted to slower metabolism of vectors living at lower temperatures. On the other hand, L. infantum and L. braziliensis successfully developed in sand flies at both temperatures tested, which might be substantial for their further spread to new areas. Next, an impact of gregarine Psychodiella sergenti on L. tropica in Phlebotomus sergenti was studied. Gregarines are commonly found in sand flies, and in mosquitoes, they can affect development of other...
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Effect of abiotic and biotic factors on Leishmania development in sand fly vectors
Hlaváčová, Jana
The thesis deals with Leishmania development in sand flies focusing on factors that could affect the vectorial part of their lifecycle. First, we examined an effect of temperature on Leishmania development in sand flies since the global warming was suggested to be one of the most important factors affecting dissemination of leishmaniasis. Development of three Leishmania species were studied at two different temperatures (20 and 26řC); L. infantum in natural vectors Lutzomyia longipalpis and Phlebotomus perniciosus, and two closely related Viannia species L. braziliensis and L. peruviana in Lu. longipalpis. Leishmania peruviana thrived well only at the lower temperature tested. At the higher temperature, most of infections were lost between days 2 and 8 post feeding, i.e. time of blood-meal remnants defecation. This suggests that this Andean species is adapted to slower metabolism of vectors living at lower temperatures. On the other hand, L. infantum and L. braziliensis successfully developed in sand flies at both temperatures tested, which might be substantial for their further spread to new areas. Next, an impact of gregarine Psychodiella sergenti on L. tropica in Phlebotomus sergenti was studied. Gregarines are commonly found in sand flies, and in mosquitoes, they can affect development of other...
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Role of catalase and chitinase in the life cycle of Leishmania parasites
Glanzová, Kristýna ; Sádlová, Jovana (advisor) ; Kodym, Petr (referee)
Leishmaniasis is an infectious disease caused by protozoa of the genus Leishmania (Kinetoplastida: Trypanosomatidae) which are transmitted by phlebotomine sand flies (Diptera: Phlebotominae). For the dixenous life cycle, leishmania parasites are equipped with enzymes that facilitate survival in both insect vectors and mammalian hosts. Gene for the enzyme catalase which protects cells from reactive oxygen species by the elimination of H2O2 and is present in related monoxenous trypanosomatids is, however, missing in Leishmania genome. Chitinase can be involved in the interaction of leishmania parasites with chitin-containing structures in sand flies (peritrophic matrix, stomodeal valve). The expression of the enzyme in amastigotes suggests its significant function also in the mammalian host. I tested the role of these enzymes in the life cycle of leishmania by direct comparison of L. mexicana mutants (i) with inserted catalase gene and (ii) with deleted chitinase gene with control groups. I conducted experimental infections of Lu. longipalpis including transmission of leishmania to the hosts by bite, tested the survival of leishmania in macrophages and performed experimental infections of BALB/c mice followed by xenodiagnoses. The experiments confirmed that the presence of catalase in leishmania does...
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Bacteria genus Asaia and Wolbachia in sandflies
Sovová, Kristina ; Volf, Petr (advisor) ; Bilej, Martin (referee)
Phlebotomine sand flies are proven vectors of many pathogens including parasites of genus Leishmania. Leishmania develop in sand fly midgut which is colonized also by many others microorganisms, creating rich community known as gut microbiota. The presence and composition of gut microbiota affect sand fly mortality, but also development of transmitted pathogens. In contrast to mosquitoes, sand fly gut microbiota is not well studied. This thesis focuses on bacteria of the genera Asaia and Wolbachia and their potential impact on Leishmania in sand fly midgut. Thesis reports the first finding of Asaia sp. and Wolbachia sp. in sand flies from Balkan penninsula - hotspot for visceral leishmaniasis and phleboviruses. In 273 individuals from subgenera Larroussius were Asaia sp. and Wolbachia sp. detected with infection prevalence 2,5 % and 8,4 %, respectively. In addition, laboratory-reared sand flies were tested for presence of these bacteria: from twelve studied colonies, only Phlebotomus perniciosus was infected by Wolbachia sp. Then, we focussed on elimination of Wolbachia sp. from this laboratory colony with the aim to use Wolbachia-negative sand flies in future experiments with Leishmania. The final part of the thesis was dedicated to bacteria of the genus Asaia (specifically A. krungthepensis),...
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Microbiota and protists in the gut of sand flies and mosquitoes
Sovová, Kristina ; Volf, Petr (advisor) ; Jančářová, Magdaléna (referee)
Sand flies and mosquitoes are vectors of leishmania and plasmodium, which are parasitic protists, that cause malaria and leishmaniasis. Mosquitoes and sand flies are exposed to a wide range of micro-organisms, which enter their bodies when they get in contact with the surrounding environment, when they intake food or via a transfer from individual to individual.The larvae acquire micro-organisms from breeding sites microhabitat, the adults from the sugary food and blood. The vast majority of the bacteria found in the mesenteron of adult vectors belongs to a group of gram negative. During the larval stages, however, the ratio of gram positive bacteria in the gut increases. In the gut, the bacteria can encounter parasitic protists and influence their development, directly or indirectly. Direct influence can be caused, for example, by the production of secondary bacterial metabolites. Indirectly, the bacteria can modulate the vector's competence over its immune system. Key words: Phlebotomus, Lutzomyia, Leishmania, microbiom
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