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Background In Europe, the generalist tick, Ixodes ricinus , is the main vector of several tick-borne pathogens causing diseases in humans and livestock. Understanding how different species of hosts limit the tick population is crucial for management. In general, larger ectoparasites are expected to select hosts with larger body size. Consistent with this, larval and nymphal I. ricinus can feed on a wide range of different-sized vertebrates, while the adult female stage is expected to rely on a medium–large-sized host for reproduction. However, we still have a limited understanding of whether medium-sized hosts other than roe deer can serve as hosts to adult ticks, and other factors than size may also affect host selection. Methods To increase our understanding of the suitability of the different species of medium-sized hosts for adult ticks, we sampled mainly roadkill mammals from within the questing season of ticks. We counted life stages of ticks on roe deer ( Capreolus capreolus ) ( n  = 29), red fox ( Vulpes vulpes ) ( n  = 6), badger ( Meles meles ) ( n  = 14) and red squirrel ( Sciurus vulgaris ) ( n  = 17) from spatially overlapping populations in Norway, and analysed variation between species across different body parts with a mixed-effects negative binomial model (with and without zero-inflation). Results Red squirrel hosted a high density of larval and nymphal I. ricinus , but only one individual had adult female ticks. Roe deer hosted by far the largest number of adult ticks. Badgers had very few ticks, possibly due to their thick skin. Red foxes had intermediate numbers, but a high proportion of subcutaneous, dead ticks (69.3%), suggesting they are not very suitable hosts. Body mass predicted the presence of adult I. ricinus ticks. However, species was a better predictor than body mass for number of ticks, suggesting there was species variation in host suitability beyond body mass per se. Conclusions Our study provides evidence that roe deer are indeed the main suitable reproduction host to adult I. ricinus ticks, and are likely a key to host limitation of the tick population in this northern ecosystem. Graphical Abstract

The long-distance, seasonal migrations of birds make them an effective ecological bridge for the movement of ticks. The introduction of exotic tick species to new geographical regions can cause the emergence of novel tick-borne pathogens. This study examined the prevalence of exotic tick species parasitizing migratory songbirds at stopover sites along the northern Gulf of Mexico using the mitochondrial 12S rRNA gene. Overall, 421 individual ticks in the genera , , and were recorded from 28 songbird species, of which and were the most abundant tick genera and species, respectively. A high throughput 16S ribosomal RNA sequencing approach characterized the microbial communities and identified pathogenic microbes in all tick samples. Microbial profiles showed that Proteobacteria was the most abundant phylum. The most abundant pathogens were and endosymbiont , , and . Permutation multivariate analysis of variance revealed that the relative abundance of and drives microbial patterns across the tick genera. We also noted a higher percentage of positive correlations in microbe-microbe interactions among members of the microbial communities. Network analysis suggested a negative correlation between a) and and, b) and . Lastly, mapping the distributions of bird species parasitized during spring migrations highlighted geographic hotspots where migratory songbirds could disperse ticks and their pathogens at stopover sites or upon arrival to their breeding grounds, the latter showing mean dispersal distances from 421-5003 kilometers. These findings spotlight the potential role of migratory birds in the epidemiology of tick-borne pathogens.

For over a decade, export of wool accounted for 58.3% of agricultural exports from Lesotho. Even though the sheep subsector contributes significantly to the economy, its development is hampered by different constraints. One of the most important constraints of sheep production is poor animal health due to widespread diseases including those caused by ticks. This study aimed to identify tick species parasitizing sheep and to determine whether tick prevalence on sheep was influenced by agroecological zone, sheep age, and seasonality. Ticks were collected from 720 sheep in the four agroecological zones of Lesotho, namely lowlands, foothills, Senqu River Valley, and highlands, during December 2018–May 2019. Ticks were picked from their sites of attachment then taken to the laboratory for identification to species level. No ticks were found on the sheep examined from the highlands and, as a result, this agroecological zone was excluded from further analysis. The following five tick species, with their overall prevalence, were identified: Rhipicephalus evertsi evertsi (38.0%), Rhipicephalus (Boophilus) decoloratus (1.6%), Hyalomma rufipes (1.0%), Otobius megnini (1.0%), and Rhipicephalus appendiculatus (0.3%). Four of the species were hard ticks (Family Ixodidae). The only soft tick species found was O. megnini (Family Agarsidae). Tick prevalence was influenced by seasonality that varied across agroecological zones. Foothills and lowlands had highest tick prevalence in December and January, respectively, and lowest prevalence in February and May, respectively, whereas Senqu River Valley had highest tick prevalence in May and lowest in March. The age of the sheep did not significantly influence prevalence of tick infestation.

Background Ticks and tick-borne diseases are a major impediment to livestock production worldwide. Cattle trade and transnational transhumance create risks for the spread of ticks and tick-borne diseases and threaten cattle production in the absence of an effective tick control program. Few studies have been undertaken on cattle ticks in the Central African region; therefore, the need to assess the occurrence and the spatial distribution of tick vectors with the aim of establishing a baseline for monitoring future spread of tick borne-diseases in the region is urgent. Results A total of 7091 ixodid ticks were collected during a countrywide cross-sectional field survey and identified using morphological criteria. Of these, 4210 (59.4%) ticks were Amblyomma variegatum , 1112 (15.6%) Rhipicephalus ( Boophilus ) microplus , 708 (10.0%) Rhipicephalus ( Boophilus ) decoloratus , 28 (0.4%) Rhipicephalus ( Boophilus ) annulatus , 210 (3.0%) Hyalomma rufipes , 768 (10.8%) Hyalomma truncatum , and 19 (0.3%) Rhipicephalus sanguineus. Three ticks of the genus Hyalomma spp. and 33 of the genus Rhipicephalus spp. were not identified to the species level. Cytochrome c oxidase subunit 1 ( cox 1) gene sequencing supported the data from morphological examination and led to identification of three additional species, namely Hyalomma dromedarii , Rhipicephalus sulcatus and Rhipicephalus pusillus . The finding of the invasive tick species R. microplus in such large numbers and the apparent displacement of the indigenous R. decoloratus is highly significant since R. microplus is a highly efficient vector of Babesia bovis . Conclusions This study reports the occurrence and current geographical distribution of important tick vectors associated with cattle in Cameroon. It appears that R. microplus is now well established and may be displacing native Rhipicephalus ( Boophilus ) species, such as R. decoloratus . This calls for an urgent response to safeguard the livestock sector in western central Africa.

Background. Powassan virus (POWV) is a rarely diagnosed cause of encephalitis in the United States. In the Northeast, it is transmitted by Ixodes scapularis, the same vector that transmits Lyme disease. The prevalence of POWV among animal hosts and vectors has been increasing. We present 8 cases of POWV encephalitis from Massachusetts and New Hampshire in 2013–2015. Methods. We abstracted clinical and epidemiological information for patients with POWV encephalitis diagnosed at 2 hospitals in Massachusetts from 2013 to 2015. We compared their brain imaging with those in published findings from Powassan and other viral encephalitides. Results. The patients ranged in age from 21 to 82 years, were, for the most part, previously healthy, and presented with syndromes of fever, headache, and altered consciousness. Infections occurred from May to September and were often associated with known tick exposures. In all patients, cerebrospinal fluid analyses showed pleocytosis with elevated protein. In 7 of 8 patients, brain magnetic resonance imaging demonstrated deep foci of increased T2/fluid-attenuation inversion recovery signal intensity. Conclusions. We describe 8 cases of POWV encephalitis in Massachusetts and New Hampshire in 2013–2015. Prior to this, there had been only 2 cases of POWV encephalitis identified in Massachusetts. These cases may represent emergence of this virus in a region where its vector, I. scapularis, is known to be prevalent or may represent the emerging diagnosis of an underappreciated pathogen. We recommend testing for POWV in patients who present with encephalitis in the spring to fall in New England.

Northeastern China is a region of high tick abundance, multiple tick-borne pathogens and likely human infections. The spectrum of diseases caused by tick-borne pathogens has not been objectively evaluated in this region for clinical management and for comparison with other regions globally where tick-transmitted diseases are common. Based on clinical symptoms, PCR, indirect immunofluorescent assay and (or) blood smear, we identified and described tick-borne diseases from patients with recent tick bite seen at Mudanjiang Forestry Central Hospital. From May 2010 to September 2011, 42% (75/180) of patients were diagnosed with a specific tick-borne disease, including Lyme borreliosis, tick-borne encephalitis, human granulocytic anaplasmosis, human babesiosis and spotted fever group rickettsiosis. When we compared clinical and laboratory features to identify factors that might discriminate tick-transmitted infections from those lacking that evidence, we revealed that erythema migrans and neurological manifestations were statistically significantly differently presented between those with and without documented aetiologies (P < 0.001, P = 0.003). Twelve patients (6.7%, 12/180) were co-infected with two tick-borne pathogens. We demonstrated the poor ability of clinicians to identify the specific tick-borne disease. In addition, it is necessary to develop specific laboratory assays for optimal diagnosis of tick-borne diseases.

Anaplasmosis is a tick-borne disease (TBDs) caused by Anaplasma spp. In areas where TBDs are endemic, it is crucial to consider the animals’ immunological status in relation to these diseases. The true prevalence of bovine anaplasmosis, the percentage of animals with protective antibodies against this TBD, and the diagnostic characteristics of three tests (multiplex polymerase chain reaction (mPCR), competitive-inhibition enzyme-linked immunosorbent assay (cELISA), and blood smear (BS)) were estimated using a Bayesian approach. A total of 620 samples were collected in two subtropical areas of Ecuador. A significant finding of this study is that approximately 70% of cattle in those endemic areas harbored protective antibodies against Anaplasma marginale . This elevated percentage may stem from persistent exposure with a high pathogen prevalence in ticks. The decline in cELISA specificity must be attributed to cross-reactivity with protective antibodies against Anaplasma spp. It is crucial to interpret this test outcome alongside exposure history and clinical manifestations. The elevated apparent prevalence detected by cELISA and BS should be contextualized with mPCR results. The high seroprevalence and infrequent clinical outbreaks suggest that the pathogen has achieved endemic stability. This study provides valuable insights into the dynamics of anaplasmosis in endemic areas and may serve as a foundation for devising TBDs control strategies in these areas.

Russia is a country with a high incidence of tick-borne encephalitis (TBE). In northwestern regions of Russia, 110 TBE cases were registered in 2021. The largest numbers of TBE cases were registered in the Arkhangelsk region and St. Petersburg. TBEV seropositivity among healthy individuals, including the unvaccinated population in northwestern Russia, was found in 12.2% of studied samples, indicating active TBEV circulation. The prevalence of TBEV is 2.4% in the two tick species most common in northwestern regions of Russia, Ixodes ricinus and Ixodes persulcatus . However, there is still no comprehensive data on the molecular characterization and phylogenetic analysis of the circulating TBEV strains. The purpose of the study was to determine the prevalence of TBEV and to identify its subtypes in ixodid ticks collected in specific areas of northwestern Russian regions. Phylogenetic analysis of E protein sequences of ten obtained strains showed that they all belong to the Siberian subtype, which were clustered into two groups: the most numerous Baltic group, clusteron 3D; and the Vasilchenko group. However, some unique isolates may form new clusterons.

Tick-borne diseases are a growing problem in many parts of the world, and their surveillance and control touch on challenging issues in medical entomology, agricultural health, veterinary medicine, and biosecurity. Spatial approaches can be used to synthesize the data generated by integrative One Health surveillance systems, and help stakeholders, managers, and medical geographers understand the current and future distribution of risk. Here, we performed a systematic review of over 8,000 studies and identified a total of 303 scientific publications that map tick-borne diseases using data on vectors, pathogens, and hosts (including wildlife, livestock, and human cases). We find that the field is growing rapidly, with the major Ixodes-borne diseases (Lyme disease and tick-borne encephalitis in particular) giving way to monitoring efforts that encompass a broader range of threats. We find a tremendous diversity of methods used to map tick-borne disease, but also find major gaps: data on the enzootic cycle of tick-borne pathogens is severely underutilized, and mapping efforts are mostly limited to Europe and North America. We suggest that future work can readily apply available methods to track the distributions of tick-borne diseases in Africa and Asia, following a One Health approach that combines medical and veterinary surveillance for maximum impact.