On the potential roles of ticks and migrating birds in the ecology of West Nile virus

The Scenario of Ticks and Tick-Borne Pathogens of Sheep on a Mediterranean Island

Ticks and transmitted pathogens constitute a major concern for livestock health/welfare and productivity for the Mediterranean region, often posing an important zoonotic threat. The aim of this study was to investigate the presence, infection intensity, and seasonality of ticks and tick-borne pathogens on the island of Lesvos in Greece, which was selected as a potential hotspot for their circulation. To this end, 101 sheep farms were visited over a tick activity season, and ticks, blood samples, and questionnaire data were collected. Ticks were identified by species, and DNA from both ticks and blood samples was further investigated using the polymerase chain reaction–reverse line blot (PCR–RLB) technique. In 72.3% of the farms, sheep were found to be infected by 9 ixodid species, with Rhipicephalus turanicus being the most common during the spring/early summer period. As regards tick-borne pathogens (TBPs), 84.9% of the animals were found to be infected with at least one pathogen, the most common being genera of Anaplasma and Theileria, alone or in co-infections. To further characterize the Anaplasma species found, selected samples were sequenced, revealing isolates of A. ovis, A. capra, A. marginale, and A. phagocytophilum. Of the 169 female R. turanicus ticks analyzed by PCR–RLB, 89.9% were harboring at least one TBP belonging to the genera Anaplasma, Ehrlichia, Babesia, Theileria, or Rickettsia. Overall, the data presented in this study revealed a high burden of ticks and TBPs in sheep, including zoonotic species, stressing the need for applying effective monitoring and control programs using a more holistic One Health approach.

Detection of tick-borne pathogens in wild birds and their ticks in Western Siberia and high level of their mismatch

The Tomsk region located in the south of Western Siberia is one of the most high-risk areas for tick-borne diseases due to elevated incidence of tick-borne encephalitis and Lyme disease in humans. Wild birds may be considered as one of the reservoirs for tick-borne pathogens and hosts for infected ticks. A high mobility of wild birds leads to unpredictable possibilities for the dissemination of tick-borne pathogens into new geographical regions. The primary goal of this study was to evaluate the prevalence of tick-borne pathogens in wild birds and ticks that feed on them as well as to determine the role of different species of birds in maintaining the tick-borne infectious foci. We analysed the samples of 443 wild birds (60 species) and 378 ticks belonging to the genus Ixodes Latraille, 1795 collected from the wild birds, for detecting occurrence of eight tick-borne pathogens, the namely tick-borne encephalitis virus (TBEV), West Nile virus (WNV), and species of Borrelia, Rickettsia, Ehrlichia, Anaplasma, Bartonella and Babesia Starcovici, 1893, using RT-PCR/or PCR and enzyme immunoassay. One or more tick-borne infection markers were detected in 43 species of birds. All markers were detected in samples collected from fieldfare Turdus pilaris Linnaeus, Blyth's reed warbler Acrocephalus dumetorum Blyth, common redstart Phoenicurus phoenicurus (Linnaeus), and common chaffinch Fringilla coelebs Linnaeus. Although all pathogens have been identified in birds and ticks, we found that in the majority of cases (75.5 %), there were mismatches of pathogens in birds and ticks collected from them. Wild birds and their ticks may play an extremely important role in the dissemination of tick-borne pathogens into different geographical regions.

A divergent Anaplasma phagocytophilum variant in an Ixodes tick from a migratory bird; Mediterranean basin

Anaplasma phagocytophilum (AP) has vast geographical and host ranges and causes disease in humans and domesticated animals. We investigated the role of northward migratory birds in the dispersal of tick-borne AP in the African-Western Palearctic.

Ticks were collected from northward migratory birds trapped during spring migration of 2010 at two localities in the central Mediterranean Sea. AP DNA was detected by PCR (gltA and 16S rRNA) and variant determination was performed using ankA sequences.

In total, 358 ticks were collected. One of 19 ticks determined as Ixodes was confirmed positive for AP DNA. The tick was collected from a woodchat shrike (Lanius senator senator) trapped in Greece, and molecularly determined to belong to the I. ricinus complex and sharing highest (95%) 16S RNA sequence identity to I. gibbosus. The ankA AP sequence exhibited highest similarity to sequences from rodents and shrews (82%) and ruminants (80%). Phylogenetic analyses placed it convincingly outside other clades, suggesting that it represents a novel AP variant.

The divergent Ixodes species harboring a novel AP variant could either indicate an enzootic cycle involving co-evolution with birds, or dissemination from other regions by avian migration. None of the 331 Hyalomma marginatum sensu lato ticks, all immature stages, were positive for AP DNA, lending no evidence for the involvement of Hyalomma ticks transported by birds in the ecology of AP.

Hyalomma rufipes on an untraveled horse: Is this the first evidence of Hyalomma nymphs successfully moulting in the United Kingdom?

During September 2018, a tick was submitted to Public Health England's Tick Surveillance Scheme for identification. The tick was sent from a veterinarian who removed it from a horse in Dorset, England, with no history of overseas travel. The tick was identified as a male Hyalomma rufipes using morphological and molecular methods and then tested for a range of tick-borne pathogens including; Alkhurma virus, Anaplasma, Babesia, Bhanja virus, Crimean-Congo Haemorrhagic fever virus, Rickettsia and Theileria. The tick tested positive for Rickettsia aeschlimannii, a spotted fever group rickettsia linked to a number of human cases in Africa and Europe. This is the first time H. rufipes has been reported in the United Kingdom (UK), and the lack of travel by the horse (or any in-contact horses) suggests that this could also be the first evidence of successful moulting of a Hyalomma nymph in the UK. It is postulated that the tick was imported into the UK on a migratory bird as an engorged nymph which was able to complete its moult to the adult stage and find a host. This highlights that passive tick surveillance remains an important method for the detection of unusual species that may present a threat to public health in the UK. Horses are important hosts of Hyalomma sp. adults in their native range, therefore, further surveillance studies should be conducted to check horses for ticks in the months following spring bird migration; when imported nymphs may have had time to drop off their avian host and moult to adults. The potential human and animal health risks of such events occurring more regularly are discussed.

Mosquito-borne epornitic flaviviruses: an update and review

West Nile Virus, Usutu virus, Bagaza virus, Israel turkey encephalitis virus and Tembusu virus currently constitute the five flaviviruses transmitted by mosquito bites with a marked pathogenicity for birds. They have been identified as the causative agents of severe neurological symptoms, drop in egg production and/or mortalities among avian hosts. They have also recently shown an expansion of their geographic distribution and/or a rise in cases of human infection. This paper is the first up-to-date review of the pathology of these flaviviruses in birds, with a special emphasis on the difference in susceptibility among avian species, in order to understand the specificity of the host spectrum of each of these viruses. Furthermore, given the lack of a clear prophylactic approach against these viruses in birds, a meta-analysis of vaccination trials conducted to date on these animals is given to constitute a solid platform from which designing future studies.

Tick infestation in birds and prevalence of pathogens in ticks collected from different places in Germany

The importance of ticks and tick-borne pathogens for human and animal health has been increasing over the past decades. For their transportation and dissemination, birds may play a more important role than wingless hosts. In this study, tick infestation of birds in Germany was examined. Eight hundred ninety-two captured birds were infested with ticks and belonged to 48 different species, of which blackbirds (Turdus merula) and song thrushes (Turdus philomelos) were most strongly infested. Ground feeders were more strongly infested than non-ground feeders, sedentary birds more strongly than migratory birds, and short-distance migratory birds more strongly than long-distance migratory birds. Mean tick infestation per bird ranged between 2 (long-distance migratory bird) and 4.7 (sedentary bird), in some single cases up to 55 ticks per bird were found. With the exception of three nymphs of Haemaphysalis spp., all ticks belonged to Ixodes spp., the most frequently detected tick species was Ixodes ricinus. Birds were mostly infested by nymphs (65.1 %), followed by larvae (32.96 %). Additionally, ticks collected from birds were examined for several pathogens: Tick-borne encephalitis virus (TBEV) and Sindbisvirus with real-time RT-PCR, Flaviviruses, Simbuviruses and Lyssaviruses with broad-range standard RT-PCR-assays, and Borrelia spp. with a Pan-Borrelia real-time PCR. Interestingly, no viral pathogens could be detected, but Borrelia spp. positive ticks were collected from 76 birds. Borrelia (B.) garinii, B. valaisiaina, B. burgdorferi s.s. and B. afzelii were determined. The screening of ticks and birds for viral pathogens with broad range PCR-assays was tested and the use as an “early warning system” is discussed.

Ticks and tick-borne pathogens in wild birds in Greece

Wild birds are common hosts of ticks and can transport them for long distances, contributing to the spreading of tick-borne pathogens. The information about ticks on birds and tick-borne pathogens in Greece is limited. The present study aimed to evaluate the prevalence and species of ticks infesting wild resident birds (mostly small passerines) in Greece, and to assess Borrelia and Rickettsia infection in the collected ticks. Detection of Borrelia burgdorferi s.l. was performed by nested PCR targeting the flaB gene. Rickettsia spp. were detected by PCR targeting the gltA and ompA genes. Seven (2 %) out of 403 birds examined in northern Greece in 2013 were infested with 15 ticks, identified as Ixodes frontalis, Ixodes acuminatus, Hyalomma marginatum, Hyalomma aegyptium and Hyalomma sp. All ticks were negative for Borrelia spp. while four of them were positive for rickettsiae (Rickettsia aeschlimannii in H. aegyptium and Rickettsia sp. in I. frontalis, H. aegyptium and H. marginatum). Ixodes acuminatus is reported for the first time in Greece and Sylvia borin is reported as a new host record for I. acuminatus.

Ticks (Acari: Ixodida) parasitizing humans in Corum and Yozgat provinces, Turkey

In order to identify ticks infesting humans in Corum and Yozgat provinces in Turkey, a total of 2110 ticks representing 14 species were collected on humans, between June and September 2009. Of those, 1551 (687♂, 450♀, 407 nymphs, 7 larvae) were collected from Corum and 559 (330♂, 180♀, 49 nymphs) were collected from Yozgat. The majority of ticks (n = 1121, 53.1 %) was Hyalomma marginatum. Other common ticks infesting humans were Dermacentor marginatus (n = 209, 9.9 %) and Rhipicephalus turanicus sensu lato (n = 145, 6.9 %) in the study area. In addition, a total of 386 immature Hyalomma were found on humans in Corum (335 nymphs, 7 larvae) and Yozgat (44 nymphs). Ixodes laguri and Haemaphysalis erinacei taurica were recorded for the first time in Corum. To the best of our knowledge, this study is the first detailed investigation on ticks infesting humans in Corum and Yozgat, except individual or incidental records. The present study provides useful information for those concerned with ticks and tick-borne diseases in Turkey.

The complete sequence of a West Nile virus lineage 2 strain detected in a Hyalomma marginatum marginatum tick collected from a song thrush (Turdus philomelos) in eastern Romania in 2013 revealed closest genetic relationship to strain Volgograd 2007

In this study the first complete sequence of the West Nile virus (WNV) lineage 2 strain currently circulating in Romania was determined. The virus was detected in a Hyalomma marginatum marginatum tick collected from a juvenile song thrush (Turdus philomelos) in the Romanian Danube Delta close to the city of Tulcea, end of August 2013. Our finding emphasizes the role of ticks in introduction and maintenance of WNV infections. Sequence analyses revealed close genetic relationship of the Romanian WNV strain to strain Reb_Volgograd_07_H, which was isolated from human brain tissue during an outbreak of West Nile neuroinvasive disease (WNND) in Russia in 2007. In 2010 the Eastern European lineage 2 WNV caused an outbreak of human WNND in Romania. Partial sequences from subsequent years demonstrated that this WNV strain became endemic in Eastern Europe and has been causing outbreaks of varying sizes in southern Russia since 2007 and in Romania since 2010.