Occurrence of Thelazia callipaeda and its vector Phortica variegata in Austria and South Tyrol, Italy, and a global comparison by phylogenetic network analysis.

The zoonotic nematode Thelazia callipaeda infects the eyes of domestic and wild animals and uses canids as primary hosts. It was originally described in Asia, but in the last 20 years it has been reported in many European countries, where it is mainly transmitted by the drosophilid fruit fly Phortica variegata. We report the autochthonous occurrence of T. callipaeda and its vector P. variegata in Austria. Nematodes were collected from clinical cases and fruit flies were caught using traps, netting, and from the conjunctival sac of one dog. Fruit flies and nematodes were morphologically identified and a section of the mitochondrial cytochrome c oxidase subunit I gene (COI) was analysed. A DNA haplotype network was calculated to visualize the relation of the obtained COI sequences to published sequences. Additionally, Phortica spp. were screened for the presence of DNA of T. callipaeda by polymerase chain reaction. Thelazia callipaeda and P. variegata were identified in Burgenland, Lower Austria, and Styria. Thelazia callipaeda was also documented in Vienna and P. variegata in Upper Austria and South Tyrol, Italy. All T. callipaeda corresponded to haplotype 1. Twenty-two different haplotypes of P. variegata were identified in the fruit flies. One sequence was distinctly different from those of Phortica variegata and was more closely related to those of Phortica chi and Phortica okadai. Thelazia callipaeda could not be detected in any of the Phortica specimens.

Hyalomma spp. in Austria-The Tick, the Climate, the Diseases and the Risk for Humans and Animals.

Recently, ticks of Hyalomma spp. have been found more often in areas previously lacking this tick species. Due to their important role as a vector of different diseases, such as Crimean-Congo-hemorrhagic fever (CCHF), the occurrence and potential spread of this tick species is of major concern. So far, eight Hyalomma sp. ticks were found between 2018 and 2021 in Austria. A serological investigation on antibodies against the CCHF virus in 897 cattle as indicator animals displayed no positive case. During observation of climatic factors, especially in the period from April to September, the year 2018 displayed an extraordinary event in terms of higher temperature and dryness. To estimate the risk for humans to come in contact with Hyalomma sp. in Austria, many parameters have to be considered, such as the resting place of birds, availability of large livestock hosts, climate, density of human population, etc.

A potential zoonotic threat: First detection of Baylisascaris procyonis in a wild raccoon from Austria.

Baylisascaris procyonis is a common gastrointestinal parasite of raccoons (Procyon lotor) in their native range, and both have been introduced to Europe. Humans may ingest ascarid eggs shed via the racoons' faeces, and this could lead to severe infections affecting the central nervous system. Here, we report the first occurrence of B. procyonis in Austria. The parasite was detected in a two-year-old male raccoon that was road-killed in November 2019 near Hittisau (Vorarlberg). Genetic profiling provided strong evidence that the raccoon (and its parasite) originated from the nearest German raccoon population. The first finding in Austria highlights the need for monitoring the parasite and information of the public and practitioners.

Zoonotic Pathogens in Ticks from Migratory Birds, Italy.

Migratory birds can transport infected ticks across continents. We evaluated pathogens in ticks collected from migratory birds in Italy. We found DNA from Rickettsia aeschlimannii, R. africae, and R. raoultii bacteria, all of which can cause disease in humans. Bird migrations might facilitate the spread of these pathogens into new areas.

Infection with Toxocara canis Inhibits the Production of IgE Antibodies to α-Gal in Humans: Towards a Conceptual Framework of the Hygiene Hypothesis?

α-Gal syndrome (AGS) is a type of anaphylactic reaction to mammalian meat characterized by an immunoglobulin (Ig)E immune response to the oligosaccharide α-Gal (Galα1-3Galß1-4GlcNAc-R). Tick bites seems to be a prerequisite for the onset of the allergic disease in humans, but the implication of non-tick parasites in α-Gal sensitization has also been deliberated. In the present study, we therefore evaluated the capacity of helminths (Toxocara canis, Ascaris suum, Schistosoma mansoni), protozoa (Toxoplasma gondii), and parasitic fungi (Aspergillus fumigatus) to induce an immune response to α-Gal. For this, different developmental stages of the infectious agents were tested for the presence of α-Gal. Next, the potential correlation between immune responses to α-Gal and the parasite infections was investigated by testing sera collected from patients with AGS and those infected with the parasites. Our results showed that S. mansoni and A. fumigatus produce the terminal α-Gal moieties, but they were not able to induce the production of specific antibodies. By contrast, T. canis, A. suum and T. gondii lack the α-Gal epitope. Furthermore, the patients with T. canis infection had significantly decreased anti-α-Gal IgE levels when compared to the healthy controls, suggesting the potential role of this nematode parasite in suppressing the allergic response to the glycan molecule. This rather intriguing observation is discussed in the context of the 'hygiene hypothesis'. Taken together, our study provides new insights into the relationships between immune responses to α-Gal and parasitic infections. However, further investigations should be undertaken to identify T. canis components with potent immunomodulatory properties and to assess their potential to be used in immunotherapy and control of AGS.

Molecular survey of tick-borne pathogens reveals a high prevalence and low genetic variability of Hepatozoon canis in free-ranging grey wolves (Canis lupus) in Germany.

Wild carnivores are important hosts for ixodid ticks and presumed reservoirs for several tick-borne pathogens (TBPs) of medical and veterinary importance. However, little is known about the role that the European grey wolf (Canis lupus) plays in the enzootic cycle of TBPs. The recent recolonization of Central European lowland, including some regions in Germany, by the grey wolf, opened up an excellent opportunity for studying the impact of the wolf population on pathogen diversity and transmission dynamics. Therefore, in the present study, we investigated spleen samples collected from 276 grey wolves in 11 federal states in Germany for common TBPs by molecular methods. In total, 127 grey wolves (46.0 %) were found to be positive for Hepatozoon canis. Only two genetic variants of this protozoan parasite (herein designated as G1 and G2) were found to circulate among the grey wolves, which can be potentially shared between populations of domestic and other wild carnivores in the country. Two grey wolves were positive for Anaplasma phagocytophilum (0.7 %), and both were co-infected with H. canis G1 genotype. The presence of other pathogens could not be confirmed by PCR and sequencing. This study represents the first one reporting H. canis in a grey wolf population worldwide, and it provides highly relevant information, which may contribute to a better understanding of the epidemiology of TBPs and the pathogen transmission dynamics among the reintroduced population of grey wolves and other carnivores.

Population structure of Borrelia turcica from Greece and Turkey.

Borrelia turcica, a member of the reptile-associated Borrelia clade, is vectored by Hyalomma aegyptium. The only suggested reservoir hosts of B. turcica are tortoises of the genus Testudo. Borrelia turcica has been described to occur in several Southeastern European countries including Turkey, Romania, Bulgaria and Greece but so far nothing is known about the relationship of these populations and whether or how they are structured. Using multilocus sequence typing (MLST) on eight chromosomally located housekeeping loci (clpA, clpX, nifS, pepX, pyrG, recG, rplB and uvrA) we analyzed 43 B. turcica isolates from Serres, Greece (n = 15) collected in 2017 and Izmir, Turkey (n = 28) collected in 2018. To understand their relationship a maximum-likelihood phylogenetic tree and goeBURST analysis were done based on MLST sequence data and allelic profiles, respectively. The data we generated confirmed that the samples of B. turcica investigated here were divergent from Lyme disease (LD) and relapsing fever (RF) species. Within the B. turcica clade, samples of different geographic origin (Greece, Turkey) clustered together in terminal branches; no obvious differences between the Greek and Turkish samples were noticeable. A goeBURST analysis using triple-locus variants revealed very few clonal complexes with the majority of samples appearing as singletons. Minor clonal complexes (consisting of two sequence types) comprised only Greek isolates, only Turkish isolates or both, so no pattern of clustering of isolates from the two geographical regions was observed. Interestingly, very little population structure was discerned in our study. This was surprising in view of the large geographic distance between collection sites of B. turcica and raises questions about the evolution or spatial spread of this species.

Survey on tick-borne pathogens in ticks removed from humans in Northwestern Italy.

Ticks are able to transmit several pathogens to the host while feeding, and thus are considered the most important vectors of infectious agents together with mosquitos. The global incidence of tick-borne diseases (TBDs) is rising, due to increased interactions between pathogens, hosts and vectors, linked to global changes. Given that information about the prevalence of tick-borne pathogens in ticks removed from humans in Italy are scarce, the aim of the present study was to identify the species of ticks biting humans in Northwestern Italy and tick-borne pathogens they harbour. An overall number of 128 ticks from 92 patients were collected from April to October 2018, almost 98% of which belonging to the Ixodes ricinus species. Molecular analysis showed the presence of Babesia spp. in 29 out of 93 analysed tick pools, with a Minimum Infection Rate (MIR) of 31.18% (29/93; CI95% 22.67-41.19%), while 1 out of 93 pools tested positive for SFG Rickettsiae (MIR = 1.08%; CI95% 0.19-5.84%). No samples tested positive for A. phagocytophilum and Borrelia spp. Sequencing revealed the presence of Babesia venatorum (28 pools), Theileria buffeli/orientalis complex (1 pool) and Rickettsia monacensis. Among these, B. venatorum and R. monacensis are zoonotic pathogens able to cause from moderate to severe infections in humans. These data highlight the importance of passive surveillance to assess the epidemiology of TBDs that pose a threat to human health.

Tick Bites Induce Anti-α-Gal Antibodies in Dogs.

Due to the functional inactivation of the gene encoding for the enzyme that is involved in the oligosaccharide galactose-α-1,3-galactose (α-Gal) synthesis, humans and Old-World primates are able to produce a large amount of antibodies against the glycan epitope. Apart from being involved in the hyperacute organ rejection in humans, anti-α-Gal antibodies have shown a protective effect against some pathogenic agents and an implication in the recently recognized tick-induced mammalian meat allergy. Conversely, non-primate mammals, including dogs, have the ability to synthetize α-Gal and, thus, their immune system is not expected to naturally generate the antibodies toward this self-antigen molecule. However, in the current study, we detected specific IgG, IgM, and IgE antibodies to α-Gal in sera of clinically healthy dogs by an indirect enzyme-linked immunosorbent assay (ELISA) for the first time. Furthermore, in a tick infestation experiment, we showed that bites of Ixodes ricinus induce the immune response to α-Gal in dogs and that the resulting antibodies (IgM) might be protective against Anaplasma phagocytophilum. These findings may help lead to a better understanding of the underlying mechanisms involved in mammalian meat allergy and tick-host-pathogen interactions, but they also open up the question about the possibility that dogs could develop an allergy to mammalian meat after tick bites, similar to that in humans.

Environmental and Molecular Drivers of the α-Gal Syndrome.

The α-Gal syndrome (AGS) is a type of allergy characterized by an IgE antibody (Ab) response against the carbohydrate Galα1-3Galß1-4GlcNAc-R (α-Gal), which is present in glycoproteins from tick saliva and tissues of non-catarrhine mammals. Recurrent tick bites induce high levels of anti-α-Gal IgE Abs that mediate delayed hypersensitivity to consumed red meat products in humans. This was the first evidence that tick glycoproteins play a major role in allergy development with the potential to cause fatal delayed anaphylaxis to α-Gal-containing foods and drugs and immediate anaphylaxis to tick bites. Initially, it was thought that the origin of tick-derived α-Gal was either residual blood meal mammalian glycoproteins containing α-Gal or tick gut bacteria producing this glycan. However, recently tick galactosyltransferases were shown to be involved in α-Gal synthesis with a role in tick and tick-borne pathogen life cycles. The tick-borne pathogen Anaplasma phagocytophilum increases the level of tick α-Gal, which potentially increases the risk of developing AGS after a bite by a pathogen-infected tick. Two mechanisms might explain the production of anti-α-Gal IgE Abs after tick bites. The first mechanism proposes that the α-Gal antigen on tick salivary proteins is presented to antigen-presenting cells and B-lymphocytes in the context of Th2 cell-mediated immunity induced by tick saliva. The second mechanism is based on the possibility that tick salivary prostaglandin E2 triggers Immunoglobulin class switching to anti-α-Gal IgE-producing B cells from preexisting mature B cells clones producing anti-α-Gal IgM and/or IgG. Importantly, blood group antigens influence the capacity of the immune system to produce anti-α-Gal Abs which in turn impacts individual susceptibility to AGS. The presence of blood type B reduces the capacity of the immune system to produce anti-α-Gal Abs, presumably due to tolerance to α-Gal, which is very similar in structure to blood group B antigen. Therefore, individuals with blood group B and reduced levels of anti-α-Gal Abs have lower risk to develop AGS. Specific immunity to tick α-Gal is linked to host immunity to tick bites. Basophil activation and release of histamine have been implicated in IgE-mediated acquired protective immunity to tick infestations and chronic itch. Basophil reactivity was also found to be higher in patients with AGS when compared to asymptomatic α-Gal sensitized individuals. In addition, host resistance to tick infestation is associated with resistance to tick-borne pathogen infection. Anti-α-Gal IgM and IgG Abs protect humans against vector-borne pathogens and blood group B individuals seem to be more susceptible to vector-borne diseases. The link between blood groups and anti-α-Gal immunity which in turn affects resistance to vector-borne pathogens and susceptibility to AGS, suggests a trade-off between susceptibility to AGS and protection to some infectious diseases. The understanding of the environmental and molecular drivers of the immune mechanisms involved in AGS is essential to developing tools for the diagnosis, control, and prevention of this growing health problem.

Fatal visceral leishmaniosis in a dog caused by Leishmania infantum in Bosnia and Herzegovina: A case report.

Canine leishmaniosis (CanL) caused by Leishmania infantum, is a zoonotic vector-borne disease endemic in the Mediterranean region. Here, we report a molecularly confirmed case of fatal CanL caused by L. infantum in the south of Bosnia and Herzegovina where epidemiology data are scarce. A 2.5-year-old, male golden retriever presented with a history of lethargy, prostration, and anorexia. Clinical examination revealed pale mucosae membranes, reduced capillary refill time, anuria, and ulcerated oral mucosae and skin of the legs. Complete blood count discovered severe non-regenerative, normocytic and normochromic anemia. Biochemistry profile showed hyperglycemia, hypoalbuminemia, hypercholesterolemia, increased potassium, and considerably elevated creatinine, urea, and phosphorus. Rapid Leishmania SNAP test was negative, as well as the serum neutralization test for leptospirosis. At necropsy, mildly enlarged and firm yellow to tan kidneys were the most prominent lesions. Macrophages laden with amastigotes in bone marrow, liver, spleen, kidneys, lymph nodes and the skin were seen in histopathology. Molecular testing by PCR and sequencing (cpb gene) confirmed and identified the pathogen as L. infantum. This study highlights the lack of key measures necessary to undertake the proper control of this important zoonosis in the country. Nationwide epidemiologic study on CanL and its vector(s), along with adoption and establishment of proper diagnostic approach with quantitative serologic and molecular methods in place are warranted.

The first autochthonous case of feline ocular thelaziosis in Austria.

Over the last 30 years, Thelazia callipaeda (Spirurida: Thelaziidae) has increasingly been reported as an agent of ocular infections in animals and humans throughout Europe. Following the cases of canine ocular thelaziosis recently recorded in Austria for the first time, in the present paper, we describe the first case of T. callipaeda infection in an Austrian cat with no history of traveling abroad. This finding further supports the occurrence of the parasite's autochthonous transmission cycle in the country. The cat showed serous ocular discharge, conjunctival hyperemia, and mild conjunctival edema in the right eye. Mechanical removal of the parasite from the cat's eye, in combination with milbemycin oxime/praziquantel oral treatment and topical use of tobramycin/dexamethasone eye drops led to complete resolution of the clinical signs within 2 weeks. Results presented in the current study are of great importance for the local veterinarians who seemed largely unaware of this zoonotic parasite. Therefore, increased awareness of medical and veterinary communities is imperative for preventing further infections in both animals and humans.

Some aspects on tick species in Mongolia and their potential role in the transmission of equine piroplasms, Anaplasma phagocytophilum and Borrelia burgdorferi L.

Ticks are cosmopolitan vectors of numerous diseases, and detection of various pathogens in ticks can help to assess their distribution. In the current study, 528 adult ticks were collected from grazing animals or the ground in ten different Mongolian provinces. Dermacentor nuttalli constituted 76.1% of them and was found in all ecozones except the eastern desert. Dermacentor marginatus (8.3%), Dermacentor silvarum (1.1%) and Ixodes persulcatus (3.0%) were found in the northern forest areas and Hyalomma asiaticum (11.4%) only in the southern (semi-)desert. Of these, 359 ticks were subjected to DNA extraction and PCR was carried out to detect various pathogens. Anaplasma spp. was found in D. marginatus and D. nuttalli (2.5% positive each), including flagged specimen and identified as Anaplasma phagocytophilum. Borrelia spp. were found in 2.5% of the ticks (mostly in I. persulcatus) and identified as Borrelia garinii. Babesia spp. (40%) identified as Babesia caballi were detected in all five tick species including flagged Dermacentor spp. and I. persulcatus, and 3.5% of the ticks (all species except D. silvarum) were positive for Theileria spp. identified as Theileria equi. The piroplasms were found in all provinces. Tick-borne encephalitis virus was not detected. The results highlight the high risk of equine piroplasmosis in Mongolia, which is a concern for both the nomadic population who rely on horses for transport and for conservation of Przewalski's horses in Mongolia. In addition, zoonotic agents such as the avian B. garinii and A. phagocytophilum were also detected, outlining a high risk for exposed humans.

Echinococcus ortleppi, the cattle strain in a crested porcupine (Hystrix cristata): A new host record.

Echinococcus granulosus sensu lato, a dog tapeworm is a species complex causing cystic echinococcosis or hydatid disease in a great variety of mammalian intermediate hosts, including humans. This complex comprises five species including Echinococcus ortleppi (G5 genotype or cattle strain). In the present paper, we report the first case of infection with the larval stage of latter cestode in a captive crested porcupine (Hystrix cristata), molecularly confirmed by PCR and sequencing of the cox1 and nad1 genes. The food contaminated with the parasite's eggs is the most likely source of the infection. Our data broaden the knowledge on the host range and geographical distribution of this rarely reported species of Echinococcus in Europe.

Bartonella henselae and Rickettsia felis Detected in Cat Fleas (Ctenocephalides felis) Derived from Eastern Austrian Cats.

Cats and cat fleas (Ctenocephalides felis) are vectors of the zoonotic bacterial pathogens Bartonella henselae and Rickettsia felis, which are the causative agents of "cat scratch disease" and "cat flea typhus," respectively. In the surroundings of Vienna (Austria), we identified 11 (10.5%; n = 105) B. henselae-positive fleas originating from 8 cats (20.5%; n = 39). One flea was positive for R. felis. There should be high levels of awareness among veterinarians and animal keepers as to the handling of cats, especially if free roaming, stray, or feral.

High diversity of blood-associated parasites and bacteria in European wild cats in Bosnia and Herzegovina: A molecular study.

Wild felids may play a significant role in the transmission of various pathogens to domestic cats, in particular, but also to other animals and humans. However, since data on the occurrence of blood-borne organisms in European wild cats (Felis silvestris silvestris) are scarce, the present study aimed to provide an insight into the genetic diversity of the agents carried by this sylvatic species in Bosnia and Herzegovina and to elucidate their pathogenic impact. Tissue samples from 18 adult wild cats were collected and examined by PCR and histopathology. Five species of apicomplexan parasites belonging to three genera (Babesia sp., Cytauxzoon sp., Hepatozoon silvestris, H. felis, Hepatozoon sp.), as well as two different sequence types of undescribed hemotropic mycoplasmas (designated as type A and type B), were identified in 15 animals (83%). Histopathology revealed no relevant lesions associated with any of the agents detected. The results clearly showed that European wild cats can harbour a broad range of blood-associated parasites and bacteria. However, further studies are required to investigate the possible implication of hematophagous arthropod vectors in their transmission and to clarify the true pathogenic significance of these organisms. Direct transmission of the agents by bites should also be considered as an alternative, non-vectorial route of transmission in wild cats.

Adult Hyalomma marginatum tick positive for Rickettsia aeschlimannii in Austria, October 2018.

We report on a non-indigenous adult Hyalomma marginatum tick in Austria carrying the human pathogenic Rickettsia aeschlimannii; presumably introduced as a nymph via migratory birds and completed the moulting within the same year. It was negative for Crimean-Congo haemorrhagic fever virus, but the finding of R. aeschlimannii represents a potential threat for humans due to its zoonotic character. Awareness of invasive tick species and carried pathogens should be improved in central and northern Europe.

Contributions to the phylogeny of Ixodes (Pholeoixodes) canisuga, I. (Ph.) kaiseri, I. (Ph.) hexagonus and a simple pictorial key for the identification of their females.

BACKGROUND: In Europe, hard ticks of the subgenus Pholeoixodes (Ixodidae: Ixodes) are usually associated with burrow-dwelling mammals and terrestrial birds. Reports of Pholeoixodes spp. from carnivores are frequently contradictory, and their identification is not based on key diagnostic characters. Therefore, the aims of the present study were to identify ticks collected from dogs, foxes and badgers in several European countries, and to reassess their systematic status with molecular analyses using two mitochondrial markers. RESULTS: Between 2003 and 2017, 144 Pholeoixodes spp. ticks were collected in nine European countries. From accurate descriptions and comparison with type-materials, a simple illustrated identification key was compiled for adult females, by focusing on the shape of the anterior surface of basis capituli. Based on this key, 71 female ticks were identified as I. canisuga, 21 as I. kaiseri and 21 as I. hexagonus. DNA was extracted from these 113 female ticks, and from further 31 specimens. Fragments of two mitochondrial genes, cox1 (cytochrome c oxidase subunit 1) and 16S rRNA, were amplified and sequenced. Ixodes kaiseri had nine unique cox1 haplotypes, which showed 99.2-100% sequence identity, whereas I. canisuga and I. hexagonus had eleven and five cox1 haplotypes, respectively, with 99.5-100% sequence identity. The distribution of cox1 haplotypes reflected a geographical pattern. Pholeoixodes spp. ticks had fewer 16S rRNA haplotypes, with a lower degree of intraspecific divergence (99.5-100% sequence identity) and no geographical clustering. Phylogenetic analyses were in agreement with morphology: I. kaiseri and I. hexagonus (with the similar shape of the anterior surface of basis capituli) were genetically more closely related to each other than to I. canisuga. Phylogenetic analyses also showed that the subgenus Eschatocephalus (bat ticks) clustered within the subgenus Pholeoixodes. CONCLUSIONS: A simple, illustrated identification key is provided for female Pholeoixodes ticks of carnivores (including I. hexagonus and I. rugicollis) to prevent future misidentification of these species. It is also shown that I. kaiseri is more widespread in Europe than previously thought. Phylogenetic analyses suggest that the subgenus Pholeoixodes is not monophyletic: either the subgenus Eschatocephalus should be included in Pholeoixodes, or the latter subgenus should be divided, which is a task for future studies.

Eurasian golden jackal as host of canine vector-borne protists.

BACKGROUND: Jackals are medium-sized canids from the wolf-like clade, exhibiting a unique combination of ancestral morphotypes, broad trophic niches, and close phylogenetic relationships with the wolf and dog. Thus, they represent a potential host of several pathogens with diverse transmission routes. Recently, populations of the Eurasian golden jackal Canis aureus have expanded into the Western Palaearctic, including most of Europe. The aim of our study was to examine Eurasian golden jackals from Romania, Czech Republic and Austria for a wide spectrum of vector-borne protists and to evaluate the role of this species as a reservoir of disease for domestic dogs and/or humans. RESULTS: Diagnostic polymerase chain reaction (PCR) DNA amplifications revealed 70% of jackals to be positive for Hepatozoon, 12.5% positive for piroplasms, and one individual positive for Leishmania infantum. Phylogenetic analyses of partial 18S rDNA sequences invariably placed sequenced isolates of Hepatozoon into the H. canis clade. For piroplasms, both the 18S and cox1 sequences obtained confirmed the presence of Babesia canis and "Theileria annae" in 5 and 2 individuals, respectively, providing the first records of these two piroplasmids in Eurasian golden jackals. A single animal from Dolj County (Romania) was PCR-positive for L. infantum, as confirmed also by sequencing of ITS1-5.8S. CONCLUSIONS: Apparently, expanding populations of jackals can play a significant role in spreading and maintaining new Babesia canis foci in Central Europe. The role of jackals in the epidemiology of "Theileria annae" and H. canis is probably similar to that of red foxes and should be taken into account in further research on these parasites. Also the presence of L. infantum deserves attention. Our study confirms that once established, the populations of Eurasian golden jackals constitute natural reservoirs for many canine vector-borne diseases, analogous to the role of the coyotes in North America.

Tick abundance: a one year study on the impact of flood events along the banks of the river Danube, Austria.

The abundance of questing ticks depends on various factors. In this study, the impact of a major flood event on tick abundance and activity was observed. Ticks were collected on a weekly basis in two approximately 2 km2 large floodplain areas on the inner and the outer bank of the river Danube north of Vienna, Austria. In 2013 before a 200 year flood event, an average of 55 ticks per hour was collected in the area on the outer bank and 21 ticks per hour in the area on the inner bank. After the flood event the tick activity was massively reduced, with 12 ticks per hour on the outer bank and 1.1 ticks per hour on the inner bank. The most distinctive factor between the two areas was the level of sediment after the flooding, with almost no sediment in the outer bank, whereas on the inner bank the average height of sediment was 270 mm. Our data indicate the residual sediment has a greater impact on tick abundance and activity than the flooding itself. Besides the direct effect of ticks being buried under the sediment, there may be important indirect effects of the sediment on the habitat of the ticks and/or the host animals. We assume that this is the reason for the generally significantly lower numbers of questing ticks in this area on the inner bank of the Danube in this region, with periodical flood events.