Modelling the potential spread of Hyalomma marginatum ticks in Europe by migratory birds

Nation-wide surveillance of ticks (Acari: Ixodidae) on birds in Singapore

Surveillance programs focused on bird ticks are often challenging owing to the difficulty in capturing and screening birds as well as the fact that ticks on avian hosts frequently occur at a low prevalence. Nonetheless, elucidating the diversity and host preferences of avian ticks is critical for understanding public health risks posed by both migratory and resident birds. The first nation-wide surveillance program of avian ticks was initiated to examine bird-tick interactions in Singapore, a key juncture along the East Asian-Australasian flyway. Two tick species were detected, namely Haemaphysalis wellingtoni and Rhipicephalus linnaei, while five bird species were found to host ticks in Singapore, namely Columba livia, Gallus gallus, Ixobrychus flavicollis, Lanius cristatus, and Pitta moluccensis. The threats posed to public health by the human-biting tick H. wellingtoni are discussed along with the potential for migratory birds and ticks to transport tick-borne pathogens into, and through, Singapore.

Crimean-Congo Hemorrhagic Fever Virus in Ticks Collected from Cattle, Corsica, France, 2023

We report the detection of Crimean-Congo hemorrhagic fever virus (CCHFV) in Corsica, France. We identified CCHFV African genotype I in ticks collected from cattle at 2 different sites in southeastern and central-western Corsica, indicating an established CCHFV circulation. Healthcare professionals and at-risk groups should be alerted to CCHFV circulation in Corsica.

Molting incidents of Hyalomma spp. carrying human pathogens in Germany under different weather conditions

BACKGROUND

Hyalomma marginatum and H. rufipes are two-host tick species, which are mainly distributed in southern Europe, Africa to central Asia but may also be found in Central and Northern Europe through introduction by migratory birds.

METHODS

Ticks were collected while feeding or crawling on animals and humans, or from the environment, in different regions in Germany, between 2019 and 2021 in a citizen science study and from 2022 to 2023 in the wake of this study.

RESULTS

From 2019 to 2023, a total of 212 Hyalomma adult ticks were detected in Germany. This included 132 H. marginatum and 43 H. rufipes ticks sent to research institutions and 37 photographic records that were only identified to genus level. The number of detected ticks varied over the years, with the highest number of 119 specimens recorded in 2019, followed by 57 in 2020. Most of the specimens were collected from horses, while some were collected from other animals, humans or found crawling on human clothes or other objects inside or outside houses. The screening of 175 specimens for Crimean-Congo hemorrhagic fever virus and of 132 specimens for Babesia/Theileria spp. by PCR gave negative results, while human-pathogenic Rickettsia were detected in 44% (77/175) of the total samples. Subsequent amplicon sequencing and phylogenetic analysis of representative samples determined the species of 41 Rickettsia aeschlimannii and one R. slovaca sequences.

CONCLUSIONS

Analysis of climatic factors indicated a significantly higher probability of Hyalomma occurrence at locations with higher average spring temperature during the years 2019 and 2020 compared to randomly generated pseudo-absence locations. Dry and hot conditions probably facilitated Hyalomma nymphs' survival and molting into adults during these years.

Transboundary determinants of avian zoonotic infectious diseases: challenges for strengthening research capacity and connecting surveillance networks

As the climate changes, global systems have become increasingly unstable and unpredictable. This is particularly true for many disease systems, including subtypes of highly pathogenic avian influenzas (HPAIs) that are circulating the world. Ecological patterns once thought stable are changing, bringing new populations and organisms into contact with one another. Wild birds continue to be hosts and reservoirs for numerous zoonotic pathogens, and strains of HPAI and other pathogens have been introduced into new regions via migrating birds and transboundary trade of wild birds. With these expanding environmental changes, it is even more crucial that regions or counties that previously did not have surveillance programs develop the appropriate skills to sample wild birds and add to the understanding of pathogens in migratory and breeding birds through research. For example, little is known about wild bird infectious diseases and migration along the Mediterranean and Black Sea Flyway (MBSF), which connects Europe, Asia, and Africa. Focusing on avian influenza and the microbiome in migratory wild birds along the MBSF, this project seeks to understand the determinants of transboundary disease propagation and coinfection in regions that are connected by this flyway. Through the creation of a threat reduction network for avian diseases (Avian Zoonotic Disease Network, AZDN) in three countries along the MBSF (Georgia, Ukraine, and Jordan), this project is strengthening capacities for disease diagnostics; microbiomes; ecoimmunology; field biosafety; proper wildlife capture and handling; experimental design; statistical analysis; and vector sampling and biology. Here, we cover what is required to build a wild bird infectious disease research and surveillance program, which includes learning skills in proper bird capture and handling; biosafety and biosecurity; permits; next generation sequencing; leading-edge bioinformatics and statistical analyses; and vector and environmental sampling. Creating connected networks for avian influenzas and other pathogen surveillance will increase coordination and strengthen biosurveillance globally in wild birds.

Exploring the diversity of tick-borne pathogens: The case of bacteria (Anaplasma, Rickettsia, Coxiella and Borrelia) protozoa (Babesia and Theileria) and viruses (Orthonairovirus, tick-borne encephalitis virus and louping ill virus) in the European continent

Ticks are the main vectors for the transmission of bacterial, protist and viral pathogens in Europe affecting wildlife and domestic animals. However, some of them are zoonotic and can cause serious, sometimes fatal, problems in human health. A systematic review in PubMed/MEDLINE database was conducted to determine the spatial distribution and host and tick species ranges of a selection of tick-borne bacteria (Anaplasma spp., Borrelia spp., Coxiella spp., and Rickettsia spp.), protists (Babesia spp. and Theileria spp.), and viruses (Orthonairovirus, and flaviviruses tick-borne encephalitis virus and louping ill virus) on the European continent in a five-year period (November 2017 - November 2022). Only studies using PCR methods were selected, retrieving a total of 429 articles. Overall, up to 85 species of the selected tick-borne pathogens were reported from 36 European countries, and Anaplasma spp. was described in 37% (159/429) of the articles, followed by Babesia spp. (34%, 148/429), Borrelia spp. (34%, 147/429), Rickettsia spp. (33%, 142/429), Theileria spp. (11%, 47/429), tick-borne flaviviruses (9%, 37/429), Orthonairovirus (7%, 28/429) and Coxiella spp. (5%, 20/429). Host and tick ranges included 97 and 50 species, respectively. The highest tick-borne pathogen diversity was detected in domestic animals, and 12 species were shared between humans, wildlife, and domestic hosts, highlighting the following zoonotic species: Anaplasma phagocytophilum, Babesia divergens, Babesia microti, Borrelia afzelii, Borrelia burgdorferi s.s., Borrelia garinii, Borrelia miyamotoi, Crimean-Congo hemorrhagic fever virus, Coxiella burnetii, Rickettsia monacensis and tick-borne encephalitis virus. These results contribute to the implementation of effective interventions for the surveillance and control of tick-borne diseases.

Rickettsial Infection in the COVID-19 Era: The Correlation between the Detection of Rickettsia aeschlimannii in Ticks and Storytelling Photography of a Presumable Human Rickettsiosis Case

Rickettsia aeschlimannii infection is an emerging human tick-borne disease with only a few recorded cases. We reported a presumable autochthonous case of rickettsiosis in an Italian cattle breeder associated with a Hyalomma marginatum bite. Rickettsia aeschlimannii DNA was detected in both the tick specimen from the patient and the grazing cattle close to his farm.

Genetic analysis challenges the presence of Ixodes inopinatus in Central Europe: development of a multiplex PCR to distinguish I. inopinatus from I. ricinus

BACKGROUND

Ixodes ricinus is an important vector of several pathogens, primarily in Europe. Recently, Ixodes inopinatus was described from Spain, Portugal, and North Africa and then reported from several European countries. In this study, a multiplex polymerase chain reaction (PCR) was developed to distinguish I. ricinus from I. inopinatus and used in the surveillance of I. inopinatus in Algeria (ALG) and three regions in the Czech Republic (CZ).

METHODS

A multiplex PCR on TROSPA and sequencing of several mitochondrial (16S rDNA, COI) and nuclear markers (TROSPA, ITS2, calreticulin) were used to differentiate these two species and for a subsequent phylogenetic analysis.

RESULTS

Sequencing of TROSPA, COI, and ITS2 separated these two species into two subclades, while 16S rDNA and calreticulin could not distinguish I. ricinus from I. inopinatus. Interestingly, 23 nucleotide positions in the TROSPA gene had consistently double peaks in a subset of ticks from CZ. Cloning of these PCR products led to a clear separation of I. ricinus and I. inopinatus indicating hybridization and introgression between these two tick taxa. Based on a multiplex PCR of TROSPA and analysis of sequences of TROSPA, COI, and ITS2, the majority of ticks in CZ were I. ricinus, no I. inopinatus ticks were found, and 10 specimens showed signs of hybridization. In contrast, most ticks in ALG were I. inopinatus, four ticks were I. ricinus, and no signs of hybridization and introgression were detected.

CONCLUSIONS

We developed a multiplex PCR method based on the TROSPA gene to differentiate I. ricinus and I. inopinatus. We demonstrate the lack of evidence for the presence of I. inopinatus in Central Europe and propose that previous studies be re-examined. Mitochondrial markers are not suitable for distinguishing I. inopinatus from I. ricinus. Furthermore, our data indicate that I. inopinatus and I. ricinus can hybridize, and the hybrids can survive in Europe.

Modelling the current and future temperature suitability of the UK for the vector Hyalomma marginatum (Acari: Ixodidae)

Hyalomma marginatum is the main vector of Crimean-Congo haemorrhagic fever virus (CCHFV) and spotted fever rickettsiae in Europe. The distribution of H. marginatum is currently restricted to parts of southern Europe, northern Africa and Asia, and one of the drivers limiting distribution is climate, particularly temperature. As temperatures rise with climate change, parts of northern Europe currently considered too cold for H. marginatum to be able to survive may become suitable, including the United Kingdom (UK), presenting a potential public health concern. Here we use a series of modelling methodologies to understand whether mean air temperatures across the UK during 2000-2019 were sufficient for H. marginatum nymphs to moult into adult stages and be able to overwinter in the UK if they were introduced on migratory birds. We then used UK-specific climate projections (UKCP18) to determine whether predicted temperatures would be sufficient to allow survival in future. We found that spring temperatures in parts of the UK during 2000-2019 were warm enough for predicted moulting to occur, but in all years except 2006, temperatures during September to December were too cold for overwintering to occur. Our analysis of the projections data suggests that whilst temperatures in the UK during September to December will increase in future, they are likely to remain below the threshold required for H. marginatum populations to become established.

Tick Infestation in Migratory Birds of the Vistula River Valley, Poland

Migratory birds play an important role in the eco-epidemiology of tick-borne diseases due to their ability to carry ticks for long distances. The aim of the present study was to investigate the prevalence and factors influencing the intensity of tick infestation in migratory birds. The study was conducted in a locality situated in the Vistula River valley, eastern Poland, during autumn, when the high migratory activity of birds is registered in the region. The birds were captured using ornithological nets and identified at the species level. In the next step, they were carefully inspected for attached ticks. Tick infestation was observed in 4.43% of the captured birds. The highest mean intensity of tick infestation was observed in birds foraging on the ground or in low shrubs and by long- and medium-distance migrants, i.e., Turdus merula (2.73), T. philomelos (2.04), and Erithacus rubecula (1.58). Ixodes ricinus was found to infest the birds most frequently. However, other tick species, i.e., I. trianguliceps, I. crenulatus (synonym I. canisuga), and I. apronophorus, rarely found in eastern Poland, were also found parasitizing birds. The occurrence of I. persulcatus, I. frontalis, and I. acuminatus (synonym I. redikorzevi) was confirmed in the region for the first time. The results of the study suggest that captured bird species are susceptible to tick infestation and could play an important role in the circulation of some tick-borne pathogens. They also play a significant role in the spread of ticks. The ecology and ethology of birds, including their foraging styles and migratory habits, are factors determining the risk of exposure of birds to tick attacks.

Emergence of Hyalomma marginatum and Hyalomma rufipes adults revealed by citizen science tick monitoring in Hungary

Hyalomma ticks are important vectors of Crimean-Congo haemorrhagic fever virus (CCHFV) and other pathogens. They are frequently carried as immatures from Africa, the Middle East and Mediterranean areas to temperate Europe via migratory birds and emergence of adults has been reported in many countries where it has so far been considered non-endemic. This study aimed to implement the first steps of the DAMA (Document, Assess, Monitor, Act) protocol by monitoring the potential arrival of adult Hyalomma ticks in Hungary applying citizen-science methods. Ticks were collected from April to December 2021 by asking volunteer participants through a self-made website to look for large, quickly moving, striped-legged hard ticks on themselves, their pets and livestock. Owing to an intensive media campaign, the project website had more than 31,000 visitors within 7 months; 137 specimens and several hundred photos of hard ticks were submitted by citizen scientists from all over the country. Beside Ixodes ricinus, Dermacentor reticulatus, Dermacentor marginatus and Haemaphysalis inermis, a specimen from a dog was morphologically identified as a male Hyalomma marginatum and another removed from a cow as a male Hyalomma rufipes. The dog and the cow had never been abroad, lived approximately 280 km apart, so the two Hyalomma observations can be considered separate introductions. Amplification of the partial mitochondrial cytochrome C oxidase subunit I gene was successfully run for both specimens. Sequencing confirmed the morphological identification for both ticks. Based on the phylogenetic analyses, the Hy. marginatum individual most likely belongs to the Eurasian population and the Hy. rufipes tick to a clade of mixed sequences from Europe and Africa. We summarize the scattered historical reports about the occurrence of Hyalomma ticks and CCHFV in Hungary. Our data highlight the effectiveness of citizens science programmes in the monitoring and risk assessment of CCHFV emergence and preparedness in the study area.

Vector Surveillance and Pathogen Detection in the Working Areas of Military Working Dogs in Eastern Austria

Vector-borne diseases play a major role in human and veterinary medicine worldwide. A previous study detected asymptomatic vector-borne pathogens in military working dogs stationed at a military base in eastern Austria, and a follow-up survey of potential arthropod vectors was conducted in spring 2019 and 2020 in the vicinity of the base to evaluate the presence of vectors and their carrier status for a range of canine and zoonotic pathogens. A total of 1324 ticks (nymphs and adults of Ixodes ricinus, comprising 92.9% of the collected specimens, and adults of Haemaphysalis inermis, a tick previously only rarely described in Austria, Haemaphysalis concinna, and Dermacentor reticulatus) were collected by flagging. In 44.1% (125/284) of all pools (n = 284), one infectious agent was found; in 27.8% (79/284) and in 1.1% (3/284), two and three different agents, respectively, could be identified. Overall, 72.9% of the pools contained at least one pathogen (Borrelia spp., Rickettsia spp., Bartonella spp., and Babesia microti). Borrelia mijamotoi, B. lustinaniae, and B. microti were previously only described in single cases in Austria. Mosquitoes were collected with BG-Sentinel traps monthly during the summer of 2019. A total of 71 individuals from 11 species were collected. No filarioid DNA was detected in the mosquito sample pools, although Dirofilaria repens had been present in the dogs from the military site. In conclusion, vector surveillance should be combined with the surveillance of an exposed population whenever possible to estimate the infection risks for dogs and their handlers.

Ticks on the Run: A Mathematical Model of Crimean-Congo Haemorrhagic Fever (CCHF)-Key Factors for Transmission

Crimean-Congo haemorrhagic fever (CCHF) is a zoonotic disease caused by the Crimean-Congo hemorrhagic fever virus (CCHFV). Ticks of the genus Hyalomma are the main vectors and represent a reservoir for the virus. CCHF is maintained in nature in an endemic vertebrate-tick-vertebrate cycle. The disease is prevalent in wide geographical areas including Asia, Africa, South-Eastern Europe and the Middle East. It is of great importance for the public health given its occasionally high case/fatality ratio of CCHFV in humans. Climate change and the detection of possible CCHFV vectors in Central Europe suggest that the establishment of the transmission in Central Europe may be possible in future. We have developed a compartment-based nonlinear Ordinary Differential Equation (ODE) system to model the disease transmission cycle including blood sucking ticks, livestock and human. Sensitivity analysis of the basic reproduction number R0 shows that decreasing the tick survival time is an efficient method to control the disease. The model supports us in understanding the influence of different model parameters on the spread of CCHFV. Tick-to-tick transmission through co-feeding and the CCHFV circulation through transstadial and transovarial transmission are important factors to sustain the disease cycle. The proposed model dynamics are calibrated through an empirical multi-country analysis and multidimensional plot reveals that the disease-parameter sets of different countries burdened with CCHF are different. This information may help decision makers to select efficient control strategies.

Climate change impacts on ticks and tick-borne infections

Evidence climate change is impacting ticks and tick-borne infections is generally lacking. This is primarily because, in most parts of the world, there are no long-term and replicated data on the distribution and abundance of tick populations, and the prevalence and incidence of tick-borne infections. Notable exceptions exist, as in Canada where the northeastern advance of Ixodes scapularis and Lyme borreliosis in the USA prompted the establishment of tick and associated disease surveillance. As a result, the past 30 years recorded the encroachment and spread of I. scapularis and Lyme borreliosis across much of Canada concomitant with a 2-3 °C increase in land surface temperature. A similar northerly advance of I. ricinus [and associated Lyme borreliosis and tick-borne encephalitis (TBE)] has been recorded in northern Europe together with expansion of this species’ range to higher altitudes in Central Europe and the Greater Alpine Region, again concomitant with rising temperatures. Changes in tick species composition are being recorded, with increases in more heat tolerant phenotypes (such as Rhipicephalus microplus in Africa), while exotic species, such as Haemaphysalis longicornis and Hyalomma marginatum, are becoming established in the USA and Southern Europe, respectively. In the next 50 years these trends are likely to continue, whereas, at the southern extremities of temperate species’ ranges, diseases such as Lyme borreliosis and TBE may become less prevalent. Where socioeconomic conditions link livestock with livelihoods, as in Pakistan and much of Africa, a One Health approach is needed to tackling ticks and tick-borne infections under the increasing challenges presented by climate change.

Red deer reveal spatial risks of Crimean-Congo haemorrhagic fever virus infection

Crimean-Congo haemorrhagic fever virus (CCHFV) continues to cause new human cases in Iberia while its spatial distribution and ecological determinants remain unknown. The virus remains active in a silent tick-animal cycle to which animals contribute maintaining the tick populations and the virus itself. Wild ungulates, in particular red deer, are essential hosts for Hyalomma ticks in Iberia, which are the principal competent vector of CCHFV. Red deer could be an excellent model to understand the ecological determinants of CCHFV as well as to predict infection risks for humans because it is large, gregarious, abundant and the principal host for Hyalomma lusitanicum. We designed a cross-sectional study, analysed the presence of CCHFV antibodies in 1444 deer from 82 populations, and statistically modelled exposure risk with host and environmental predictors. The best-fitted statistical model was projected for peninsular Spain to map infection risks. Fifty out of 82 deer populations were seropositive, with individual population prevalence as high as 88%. The highest prevalence of exposure to CCHFV occurred in the southwest of the Iberian Peninsula. Climate and ungulate abundance were the most influential predictors of the risk of exposure to the virus. The highest risk regions were those where H. lusitanicum is most abundant. Eight of the nine primary human cases occurred in or bordering these regions, demonstrating that the model predicts human infection risk accurately. A recent human case of CCHF occurred in northwestern Spain, a region that the model predicted as low risk, pointing out that it needs improvement to capture all determinants of the CCHFV infection risk. In this study, we have been able to identify the main ecological determinants of CCHFV, and we have also managed to create an accurate model to assess the risk of CCHFV infection.

Crimean-Congo Hemorrhagic Fever Virus in Asia, Africa and Europe

The global spread of ticks and various tick-borne viruses (TBVs) suggests the possibility of new tick-borne diseases emerging. Crimean-Congo hemorrhagic fever virus (CCHFV) is an emerging TBV of the Nairoviridae family that causes serious disease that can be fatal in humans. CCHFV endemic foci can be found in Africa, Asia, the Middle East, and South-Eastern Europe, and has spread to previously unaffected regions and nations, such as Spain, over the last two decades. In this review, we discuss the current situation of CCHFV in Asia, Africa and Europe based on existing knowledge, and we discuss driving factors in the distribution and transmission of the virus, such as the spread of tick vector species and host reservoirs.

Efficacy of a single administration of afoxolaner (NexGard®) or fipronil plus permethrin (Frontline® Tri-Act) against Hyalomma marginatum ticks in dogs

This study was conducted to assess the acaricidal efficacy of afoxolaner (NexGard®, Boehringer Ingelheim), and fipronil - permethrin (Frontline® Tri-Act, Boehringer Ingelheim) administered once to dogs experimentally infested with Hyalomma marginatum ticks. Twenty-four Beagle dogs were randomly allocated based on a pre-treatment H. marginatum infestation to an untreated control group, a NexGard® or a Frontline® Tri-Act treated groups. Treatments were administered once on Day 0 as per the products' labels. For the efficacy evaluation, dogs were experimentally infested with 30 adult H. marginatum ticks on Days -2, 7, 28 and 36. In-situ counts were performed at 48 h post-treatment on Day 2 and post-infestations on Days 9, 30 and 38. Ticks were removed and counted at 72 h post-treatment on Day 3 and after each tick infestation on Days 10, 31 and 39. The numbers of live ticks counted in the treated groups were significantly different than in the control group at all time-points (p ≤ 0.0006). The efficacy was at least 97% after 48 h, and at least 99% after 72 h for both treatments. In this study both afoxolaner and fipronil/permethrin formulations demonstrated a high efficacy against adult H. marginatum ticks in treated dogs for at least five weeks.

Epidemiological Aspects of Crimean-Congo Hemorrhagic Fever in Western Europe: What about the Future?

Crimean-Congo hemorrhagic fever virus (CCHFV) is an arthropod-borne virus (arbovirus), mainly transmitted by ticks, belonging to the genus Orthonairovirus (family Nairoviridae, order Bunyavirales). CCHFV causes a potentially severe, or even fatal, human disease, and it is widely distributed in Africa, Asia, eastern Europe and, more recently, in South-western Europe. Until a few years ago, no cases of Crimean-Congo hemorrhagic fever (CCHF) had been reported in western Europe, with the exception of several travel-associated cases. In 2010, the CCHFV was reported for the first time in South-western Europe when viral RNA was obtained from Hyalomma lusitanicum ticks collected from deer in Cáceres (Spain). Migratory birds from Africa harboring CCHFV-infected ticks and flying to Spain appear to have contributed to the establishment of the virus (genotype III, Africa-3) in this country. In addition, the recent findings in a patient and in ticks from deer and wild boar of viral sequences similar to those from eastern Europe (genotype V, Europe-1), raise the possibility of the introduction of CCHFV into Spain through the animal trade, although the arrival by bird routes cannot be ruled out (Africa-4 has been also recently detected). The seropositive rates of animals detected in regions of South-western Spain suggest an established cycle of tick-host-tick in certain areas, and the segment reassortment detected in the sequenced virus from one patient evidences a high ability to adaptation of the virus. Different ixodid tick genera can be vectors and reservoirs of the virus, although Hyalomma spp. are particularly relevant for its maintenance. This tick genus is common in Mediterranean region but it is currently spreading to new areas, partly due to the climate change and movement of livestock or wild animals. Although to a lesser extent, travels with our pets (and their ticks) may be also a factor to be considered. As a consequence, the virus is expanding from the Balkan region to Central Europe and, more recently, to Western Europe where different genotypes are circulating. Thus, seven human cases confirmed by molecular methods have been reported in Spain from 2016 to August 2020, three of them with a fatal outcome. A One Health approach is essential for the surveillance of fauna and vector populations to assess the risk for humans and animals. We discuss the risk of CCHFV causing epidemic outbreaks in Western Europe.