Geographical distribution and prevalence of tick‐borne encephalitis virus in questing Ixodes ricinus ticks and phylogeographic structure of the Ixodes ricinus vector in Norway

The tick‐borne encephalitis virus (TBEV), a zoonotic flaviviral infection, is endemic in large parts of Norway and Eurasia. Humans are mainly infected with TBEV via bites from infected ticks. In Norway, the main geographical distribution of ticks is along the Norwegian coastline from southeast (~59°N) and up to the southern parts of Nordland County (~65°N). In this study, we collected ticks by flagging along the coast from Østfold County to Nordland County. By whole‐genome sequencing of the mitochondrial genome of Ixodes ricinus, the phylogenetic tree suggests that there is limited phylogeographic structure both in Norway and in Europe. The overall TBEV prevalence is 0.3% for nymphs and 4.3% for adults. The highest estimated TBEV prevalence in adult ticks was detected in Rogaland and Vestfold County, while for nymphs it is highest in Vestfold, Vest‐Agder and Rogaland. The present work is one of the largest studies on distribution and prevalence of TBEV in ticks in Scandinavia, showing that the virus is wider distributed in Norway than previously anticipated.     

A Vegetation Index qualifying pasture edges is related to Ixodes ricinus density and to Babesia divergens seroprevalence in dairy cattle herds

Babesia divergens, transmitted by the tick Ixodes ricinus, is the main agent of bovine piroplasmosis in France. This Apicomplexa often is present in asymptomatic carriers; however, clinical cases are rare. While numerous factors are known to influence tick density, no risk factor of contact with B. divergens has been identified for cattle. Our study aimed to explore whether a Vegetation Index could serve as an indirect indicator of within-herd B. divergens seroprevalence. In February 2007, blood samples were taken from all of the cows in 19 dairy cattle herds in Western France and IFAT serology was performed individually to measure B. divergens seroprevalence. The following spring, I. ricinus nymphs were collected by drag sampling along transects on the vegetation of each farm's pasture perimeters. Tick density was related significantly to a Vegetation Index (V.I., ranging from 1 to 5) that took into account the abundance of trees and bushes on the edge of pastures: most ticks (57%) were found in transects with the highest V.I. (covering 15% of the explored surface in the study area). At the farm level, the proportion of transects presenting I. ricinus nymphs was significantly related to B. divergens seroprevalence: the farms with more than 15% of transects with I. ricinus had a significantly higher risk of high seroprevalence. The proportion of pasture perimeters where the V.I.=5 also was significantly related to B. divergens seroprevalence: the farms where more than 20% of transects had a V.I.=5 had a significantly higher risk of high seroprevalence. Given that the Vegetation Index is a steady indicator of the potential I. ricinus density in the biotope, we recommend that the risk of high B. divergens seroprevalence in cows be evaluated using this tool rather than drag samplings.     

Resistance of sheep to laboratory infestations of the tick, Ixodes ricinus

The development of tick resistance was studied in three one-year-old female Galway cross ewes which received up to three staggered infestations of 100 adult pairs of Ixodes ricinus. Sheep acquired resistance after the first infestation and the ticks showed suppressed feeding and oviposition success. The histology of tick-bite lesions revealed a cellular infiltrate consisting predominantly of neutrophils and this was followed by the infiltration and degranulation of basophils. Mononuclear cells accompanied basophil infiltration and then dominated the cellular infiltrate. Eosinophils infiltrated tick-bite lesions in considerable numbers especially in the tertiary infestation, in which degranulation of mast cells and basophils was also most rapid.     

First detection of Ixodes ricinus on beef cattle in Israel

This is the first report of the presence of Ixodes ricinus on beef cattle in Israel. Up to now, in the Middle East this tick was considered to be confined to Turkey and northern Iran. In the present study, tick samples collected from field-grazing beef cattle in western Galilee (northern Israel) were first examined morphologically for species-specific taxonomical features and then by molecular characterization. Ticks identified morphologically as I. ricinus were then examined by PCR with four different molecular markers: 12S rRNA, 16S rRNA, COX1 and cytochrome B. The PCR products were sequenced and compared with annotated I. ricinus sequences in GenBank? and the analyzed sequences from the collected samples shared 98–99% identity with reported I. ricinus sequences. In contrast, sequences from the collected ticks shared identity of 91% or less with annotated sequences from other Ixodes species. Multiple alignments and neighbor-joining analyses performed for each of the four markers reinforced the results obtained from pairwise alignments. These findings demonstrated for the first time the presence in Israel of the tick species I. ricinus – with results confirmed by a combination of morphological examination and molecular analyses.     

An electron microscopic study of Cytoecetes phagocytophila infection in Ixodes ricinus

Tick-borne fever, caused by a rickettsia-like organism, Cytoecetes phagocytophila, is transmitted by the sheep tick Ixodes ricinus. An electron microscopic technique was developed to examine I ricinus for C phagocytophila infection. Infected and uninfected ticks were obtained from a laboratory maintained tick culture. All stages of I ricinus collected from one field site were examined; 44 per cent of nymphae and 32 per cent of adults were infected with C phagocytophila, but larvae were uninfected. This supports the previously held theory of transtadial, but not transovarial transmission of tick-borne fever.     

Evidence of Bartonella sp. in questing adult and nymphal Ixodes ricinus ticks from France and co-infection with Borrelia burgdorferi sensu lato and Babesia sp

Ticks are known vectors for a wide range of pathogenic microorganisms. Their role in the transmission of some others is so far only suspected. Ticks can transmit multiple pathogens, however, little is known about the co-existence of these pathogens within questing ticks. We looked for the presence of DNA from three micro-organisms, Bartonella sp., Borrelia burgdorferi sensu lato and Babesia sp. which are known or suspected tick-borne pathogens, using a cohort of 92 questing Ixodes ricinus ticks collected from pastures in northern France. DNA was extracted from each individual tick and the presence of the three pathogens was investigated using Polymerase Chain Reaction (PCR) amplification. Nine among 92 samples (9.8%) demonstrated PCR products using Bartonella specific primers, 3 among 92 (3.3%) using Borrelia burgdorferi sensu lato specific primers and 19 among 92 (20.6%) using Babesia specific primers. Seven among 92 samples (7.6%) were PCR positive for at least two of the pathogens and one sample was positive for all three. Adult ticks (12/18; 67%) showed significantly higher infection rates compared to nymphs (11/74; 15%) for all three pathogens (P < 0.001). This study is the demonstration of the simultaneous presence of Bartonella sp., Borrelia burgdorferi sensu lato and Babesia sp. in questing Ixodes ricinus ticks.     

Distribution of Neoehrlichia mikurensis in Ixodes ricinus ticks along the coast of Norway: The western seaboard is a low‐prevalence region

Neoehrlichia mikurensis is a tick‐borne pathogen widespread among ticks and rodents in Europe and Asia. A previous study on Ixodes ricinus ticks in Norway suggested that N. mikurensis was scarce or absent on the south‐west coast of Norway, but abundant elsewhere. The aim of this study was to further investigate the prevalence and distribution of N. mikurensis along the western seaboard of Norway in comparison with more eastern and northern areas. The second aim of the study was to examine seasonal variation of the bacterium in one specific location in the south‐eastern part of Norway. Questing I. ricinus were collected from 13 locations along the coast of Norway, from Brønnøysund in Nordland County to Spjærøy in Østfold County. In total, 11,113 nymphs in 1,113 pools and 718 individual adult ticks were analysed for N. mikurensis by real‐time PCR. The mean prevalence of N. mikurensis in adult ticks was 7.9% while the estimated pooled prevalence in nymphs was 3.5%. The prevalence ranged from 0% to 25.5%, with the highest prevalence in the southernmost and the northernmost locations. The pathogen was absent, or present only at low prevalence (<5%), at eight locations, all located in the west, from 58.9°N to 64.9°N. The prevalence of N. mikurensis was significantly different between counties (p < .0001). No significant seasonal variation of N. mikurensis prevalence was observed in the period May to October 2015. Our results confirm earlier findings of a low prevalence of N. mikurensis in the western seaboard of Norway.     

Temporal distribution of Ixodes ricinus, Dermacentor reticulatus and Haemaphysalis concinna in Hungary

A survey was carried out over a 4-year period to describe the temporal distribution of three 'anthropophilic' tick species, Ixodes ricinus, Dermacentor reticulatus and Haemaphysalis concinna in Hungary. Altogether 4658 adult ticks belonging to the three species were collected from 1931 red foxes (Vulpes vulpes) killed in an area of about 70,000 km(2) representing all major climatic areas of the country. The seasonal activity of the three species was different. I. ricinus ticks were most active between April and June with an activity peak in May. A less marked increase of activity was also observed in September and October. The highest activity of D. reticulatus ticks was seen between September and November with an activity peak in October, nevertheless, a marked increase of activity could also be observed in April. Small number of I. ricinus and D. reticulatus were collected in all other months. H. concinna ticks were active from May to July with an activity peak in June and completely disappeared between October and March. The temporal distribution of the three tick species might be used for predictions on the seasonality of tick-borne diseases in Hungary.     

Characterization of avipoxviruses from wild birds in Norway

Avipoxviruses from different geographic regions of the world have been characterized to study their genetic and biological properties, but so far, no such work has been performed on Norwegian isolates. Lesions suggestive of avian pox, found on a Norwegian wild sparrow (Passer domesticus) and wood pigeon (Palumbus palumbus), were obtained in 1972 and 1996, respectively. Histologically, these lesions were demonstrated to be characteristic of poxvirus infections and the poxvirus was observed using an electron microscope. The resulting viruses were propagated in chicken embryo fibroblast cells. Restriction fragment length polymorphism of genomes from 2 Norwegian isolates and fowl pox vaccine strain, generated by BamHI, revealed a high degree of heterogeneity among the isolates. The profiles of avipoxviruses isolated from wild birds were clearly distinct from each other and also to the fowl poxvirus strain. Furthermore, chickens experimentally infected with pigeon poxvirus had higher antibody titers and extensive lesions compared to other isolates. This may suggest that pigeon poxvirus is more virulent than the other isolates.     

Experimental in vitro transmission of Babesia sp. (EU1) by Ixodes ricinus

Babesia sp. (EU1), first characterized in 2003, has been implicated in human cases of babesiosis in Italy, Austria and Germany. It has been identified in roe deer and in its suspected tick vector, Ixodes ricinus, in several European countries. The aim of the present study was to validate the competence of I. ricinus as a vector of Babesia sp. (EU1) via experimental infections. For this purpose, a parasite strain isolated from roe deer was cloned in sheep erythrocytes. After experimental infections, parasite DNA was successfully amplified by PCR in both eggs and larvae originating from infected I. ricinus females and in the salivary glands of females exposed to Babesia sp. (EU1) as nymphs. We also demonstrate that infected females were able to transmit parasite DNA during a new blood meal. Together with previous epidemiological studies, these results validate I. ricinus as a competent vector for Babesia sp. (EU1).     

Efficacy of a collar impregnated with amitraz and pyriproxyfen for prevention of experimental tick infestations by Rhipicephalus sanguineus, Ixodes ricinus, and Ixodes scapularis in dogs

OBJECTIVE: To compare the efficacy of collars impregnated with 9% amitraz or 9% amitraz and 0.5% pyriproxyfen (PPF) for control of newly established tick infestations by Rhipicephalus sanguineus, Ixodes ricinus, and Ixodes scapularis in dogs and determine whether egg production by surviving female ticks was decreased. DESIGN: Prospective study. ANIMALS: 72 dogs. PROCEDURE: Dogs were fitted with 1 of 3 test collars impregnated with amitraz, amitraz and PPF, or only excipients (untreated controls). In 3 trials corresponding to each of the 3 tick species, dogs were infested with 150 unfed adult ticks on days 8, 10, 13, and 18. The number of feeding female ticks was recorded on days 10, 13, 18, and 28. Surviving females were weighed and permitted to oviposit under controlled conditions. RESULTS: Collars impregnated with amitraz and PPF decreased tick loads as efficiently as collars containing amitraz alone. Inclusion of PPF into the collar did not significantly decrease the efficacy of amitraz. The few female ticks that survived after feeding on dogs treated with collars containing PPF were unable to oviposit. CONCLUSIONS AND CLINICAL RELEVANCE: Collars impregnated with amitraz were efficient in preventing tick infestations in dogs but did not inhibit oviposition in the few surviving female ticks. Incorporation of PPF into the amitraz-impregnated collar resulted in impairment of the reproductive ability of ticks.