Zoonotic Pathogens in Ticks from Migratory Birds, Italy

Amblyomma sparsum Neumann 1899 on migratory birds from Africa: First records in Italy

Migratory birds play an important role in transporting ixodid ticks and tick-borne pathogens between continents. During the Boreal spring, migratory birds reach Europe, mainly from sub-Saharan Africa or from northern African countries but not much is known about the diversity and ecology of the ticks they spread. From 2017 to 2022, in the framework of two consecutive projects focused on sampling migratory birds from Africa to Europe, a total of 27 immature Amblyomma ticks were collected from migratory birds, belonging to 8 species, captured on the Island of Ventotene, an important stop-over site in the Mediterranean Sea. In the absence of adult specimens, morphological identification was limited to assigning these ticks to the Amblyomma genus. In this study, sequencing and comparative analysis of three mitochondrial molecular markers (12S rDNA, 16S rDNA, COI) were performed to achieve taxonomic identification. Sequences obtained from Ventotene specimens matched at 100% identity with Amblyomma sparsum. In conclusion, this study documented that immature stages of this species belonging to the Amblyomma marmoreum complex reached the Pontine Islands for six consecutive years. The entry of alien tick species and their potentially transmitted pathogens deserves further study, also in light of the globally ongoing climate change.

Molecular Survey on the Occurrence of Tick-Borne Bacteria in Wild Birds from Central Italy

Birds are known to be carriers of ticks infected by tick-borne pathogens, including bacteria. However, not many studies have been carried out on avian tissues to detect these agents. The aim of the present survey was to investigate, using PCR, the presence of Anaplasma phagocytophilum, Bartonella spp., Borrelia burgdorferi sensu lato, Chlamydia psittaci, Coxiella burnetii, Ehrlichia canis, Francisella tularensis, and Rickettsia spp. in the spleens collected from 300 wild birds of different orders and species from Central Italy. A total of 53 (17.67%) samples were PCR positive for at least one investigated pathogen. One (0.33%) bird was positive for Bartonella spp., five (1.67%) birds were positive for C. burnetii, eleven (3.67%) for B. burgdorferi s.l., and thirty-six (12%) for C. psittaci. No coinfection was detected. All samples were negative for A. phagocytophilum, E. canis, F. tularensis, and Rickettsia spp. The findings showed that wild birds may harbor different zoonotic tick-borne bacteria; therefore, they can contribute to the diffusion of these agents.

New insights into the systematics of the afrotropical Amblyomma marmoreum complex (Acari: Ixodidae) and the genome of a novel Rickettsia africae strain using morphological and metagenomic approaches

The Amblyomma marmoreum complex includes afrotropical species, such as Amblyomma sparsum, a three-host tick that parasitizes reptiles, birds, and mammals, and is a recognized vector of Ehrlichia ruminantium. However, the lack of morphological, genetic and ecological data on A. sparsum has caused considerable confusion in its identification. In this study, we used microscopy and metagenomic approaches to analyze A. sparsum ticks collected from a puff adder snake (Bitis arietans) in southwest Senegal (an endemic rickettsioses area) in order to supplement previous morphological descriptions, provide novel genomic data for the A. marmoreum complex, and describe the genome of a novel spotted fever group Rickettsia strain. Based on stereoscope and scanning electron microscopy (SEM) morphological evaluations, we provide high-quality images and new insights about punctation and enameling in the adult male of A. sparsum to facilitate identification for future studies. The metagenomic approach allowed us assembly the complete mitochondrial genome of A. sparsum, as well as the nearly entire chromosome and complete plasmid sequences of a novel Rickettsia africae strain. Phylogenomic analyses demonstrated a close relationship between A. sparsum and Amblyomma nuttalli for the first time and confirmed the position of A. sparsum within the A. marmoreum complex. Our results provide new insights into the systematics of A. sparsum and A. marmoreum complex, as well as the genetic diversity of R. africae in the Afrotropical region. Future studies should consider the possibility that A. sparsum may be a vector for R. africae.

Long term evaluation of factors influencing the association of ixodid ticks with birds in Central Europe, Hungary

Birds play a crucial role in disseminating ticks that carry pathogens of high veterinary-medical importance. The aim of this study was to analyze data of a long-term tick collection from birds at a single stop-over site in Central Europe, Hungary. Over eight years (2015-2022) 5833 ticks (ten species) were collected from 2395 tick-infested birds. The most abundant species were Ixodes ricinus (n = 3971) and Haemaphysalis concinna (n = 1706). Ixodes ricinus nymphs and larvae were the most frequently occurring on resident and short-distance migratory birds with forest habitat but Ha. concinna was the most abundant species on reed-associated, long-distance migrants. Haemaphysalis concinna occurred mostly on birds feeding above the ground level, while I. ricinus predominated on ground feeding birds. Infestation with I. ricinus nymphs always peaked in the first half of the year, in contrast to larvae which were more abundant on avian hosts in the autumn. At the same time, Ha. concinna larvae and nymphs had their peak numbers in the summer. This is the first long-term study on the tick infestation of birds in Central Europe. The study shows that, migration distance, habitat type, and typical feeding level of birds, as well as characteristics of tick life cycle are all key factors in the role of birds as tick disseminators. It was revealed that Savi's Warbler (Locustella luscinioides) is the most frequent hosts of Ha. concinna in Central Hungary.

First report of spotted fever group Rickettsia aeschlimannii in Hyalomma turanicum, Haemaphysalis bispinosa, and Haemaphysalis montgomeryi infesting domestic animals: updates on the epidemiology of tick-borne Rickettsia aeschlimannii

Tick-borne Rickettsia spp. have long been known as causative agents for zoonotic diseases. We have previously characterized Rickettsia spp. in different ticks infesting a broad range of hosts in Pakistan; however, knowledge regarding Rickettsia aeschlimannii in Haemaphysalis and Hyalomma ticks is missing. This study aimed to obtain a better understanding about R. aeschlimannii in Pakistan and update the knowledge about its worldwide epidemiology. Among 369 examined domestic animals, 247 (66%) were infested by 872 ticks. Collected ticks were morphologically delineated into three genera, namely, Rhipicephalus, Hyalomma, and Haemaphysalis. Adult females were the most prevalent (number ₌ 376, 43.1%), followed by nymphs (303, 34.74%) and males (193, 22.13%). Overall, genomic DNA samples of 223 tick were isolated and screened for Rickettsia spp. by the amplification of rickettsial gltA, ompA, and ompB partial genes using conventional PCR. Rickettsial DNA was detected in 8 of 223 (3.58%) ticks including nymphs (5 of 122, 4.0%) and adult females (3 of 86, 3.48%). The rickettsial gltA, ompA, and ompB sequences were detected in Hyalomma turanicum (2 nymphs and 1 adult female), Haemaphysalis bispinosa (1 nymph and 1 adult female), and Haemaphysalis montgomeryi (2 nymphs and 1 adult female). These rickettsial sequences showed 99.71-100% identity with R. aeschlimannii and phylogenetically clustered with the same species. None of the tested Rhipicephalus microplus, Hyalomma isaaci, Hyalomma scupense, Rhipicephalus turanicus, Hyalomma anatolicum, Rhipicephalus haemaphysaloides, Rhipicephalus sanguineus, Haemaphysalis cornupunctata, and Haemaphysalis sulcata ticks were found positive for rickettsial DNA. Comprehensive surveillance studies should be adopted to update the knowledge regarding tick-borne zoonotic Rickettsia species, evaluate their risks to humans and livestock, and investigate the unexamined cases of illness after tick bite among livestock holders in the country.

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.

Tick Species Diversity and Molecular Identification of Spotted Fever Group Rickettsiae Collected from Migratory Birds Arriving from Africa

The role of migratory birds in the spread of ticks and tick-borne pathogens along their routes from Africa to Europe is increasingly emerging. Wild birds can host several tick species, often infected by bacteria responsible for zoonoses. The aim of the study is to assess the possible introduction of exotic ticks carried by migratory birds into Italy from Africa and to detect the presence of Rickettsia species and Coxiella burnetii they may harbor. During a two-year survey, we collected ticks from migratory birds captured during their short stop-over on Ventotene Island. Specimens were first identified by morphology or sequencing molecular targets when needed, and then tested by real-time PCR for the presence of selected pathogens. A total of 91% of the collection consisted of sub-Saharan ticks, more than 50% of which were infected by Rickettsia species belonging to the spotted fever group, mainly represented by R. aeschlimannii. In contrast, the suspected C. burnetii detected in two soft ticks were confirmed as Coxiella-like endosymbionts and not the pathogen. Although there are still gaps in the knowledge of this dispersal process, our findings confirm the role of migratory birds in the spread of ticks and tick-borne pathogens, suggesting the need for a continuous surveillance to monitor the potential emergence of new diseases in Europe.

Detection of Pathogens and Ticks on Sedentary and Migratory Birds in Two Corsican Wetlands (France, Mediterranean Area)

Birds are one of the most species-diverse vertebrate groups and are susceptible to numerous hematophagous ectoparasites. Migratory birds likely contribute to the circulation of these ectoparasites and their associated pathogens. One of the many migration paths crosses the Mediterranean islands including Corsica and its wetlands, which are migration stopovers. In our study, we collected blood samples and hematophagous ectoparasites in migratory and sedentary bird populations in two coastal lagoons: Biguglia and Gradugine. A total of 1377 birds were captured from which 762 blood samples, 37 louse flies, and 44 ticks were collected. All the louse flies were identified as Ornithomya biloba and all the ticks were from the Ixodes genus: Ixodes sp. (8.5%), I. accuminatus/ventalloi (2.9%), I. arboricola/lividus (14.3%), I. frontalis (5.7%) and I. ricinus (68.6%). Five pathogens were detected: Anaplasma phagocytophilum, Erhlichia chaffeensis, and Rickettsia helvetica in ticks, and Trypanosoma sp. in louse flies. Ehrlichia chaffeensis and the West Nile virus were both detected in bird blood samples in Corsica. This is the first report of these tick, louse fly and pathogen species isolated on the bird population in Corsica. Our finding highlights the importance of bird populations in the presence of arthropod-borne pathogens in Corsican wetlands.

Multisectoral Perspectives on Global Warming and Vector-borne Diseases: a Focus on Southern Europe

Purpose of Review

The climate change (CC) or global warming (GW) modifies environment that favors vectors' abundance, growth, and reproduction, and consequently, the rate of development of pathogens within the vectors. This review highlights the threats of GW-induced vector-borne diseases (VBDs) in Southern Europe (SE) and the need for mitigation efforts to prevent potential global health catastrophe.

Recent Findings

Reports showed astronomical surges in the incidences of CC-induced VBDs in the SE. The recently (2022) reported first cases of African swine fever in Northern Italy and West Nile fever in SE are linked to the CC-modified environmental conditions that support vectors and pathogens' growth and development, and disease transmission.

Summary

VBDs endemic to the tropics are increasingly becoming a major health challenge in the SE, a temperate region, due to the favorable environmental conditions caused by CC/GW that support vectors and pathogens' biology in the previously non-endemic temperate regions.

A Systematic Review of the Distribution of Tick-Borne Pathogens in Wild Animals and Their Ticks in the Mediterranean Rim between 2000 and 2021

Tick-borne pathogens (TBPs) can be divided into three groups: bacteria, parasites, and viruses. They are transmitted by a wide range of tick species and cause a variety of human, animal, and zoonotic diseases. A total of 148 publications were found on tick-borne pathogens in wild animals, reporting on 85 species of pathogens from 35 tick species and 17 wild animal hosts between 2000 and February 2021. The main TBPs reported were of bacterial origin, including Anaplasma spp. and Rickettsia spp. A total of 72.2% of the TBPs came from infected ticks collected from wild animals. The main tick genus positive for TBPs was Ixodes. This genus was mainly reported in Western Europe, which was the focus of most of the publications (66.9%). It was followed by the Hyalomma genus, which was mainly reported in other areas of the Mediterranean Rim. These TBPs and TBP-positive tick genera were reported to have come from a total of 17 wild animal hosts. The main hosts reported were game mammals such as red deer and wild boars, but small vertebrates such as birds and rodents were also found to be infected. Of the 148 publications, 12.8% investigated publications on Mediterranean islands, and 36.8% of all the TBPs were reported in seven tick genera and 11 wild animal hosts there. The main TBP-positive wild animals and tick genera reported on these islands were birds and Hyalomma spp. Despite the small percentage of publications focusing on ticks, they reveal the importance of islands when monitoring TBPs in wild animals. This is especially true for wild birds, which may disseminate their ticks and TBPs along their migration path.

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.

Hard ticks (Acari: Ixodidae) associated with birds in Europe: Review of literature data

Hard ticks (Acari: Ixodidae) are considered the most important transmitters of pathogens in the temperate zone that covers most of Europe. In the era of climate change tick-borne diseases are predicted to undergo geographical range expansion toward the north through regions that are connected to southern areas of the continent by bird migration. This alone would justify the importance of synthesized knowledge on the association of tick species with avian hosts, yet birds also represent the most taxonomically and ecologically diverse part of urban vertebrate fauna. Birds frequently occur in gardens and near animal keeping facilities, thus playing a significant role in the dispersal of ticks and tick-borne pathogens in synanthropic environments. The primary aim of this review is to provide a comprehensive reference source (baseline data) for future studies, particularly in the context of discovering new tick-host associations after comparison with already published data. The records on the ixodid tick infestations of birds were assessed from nearly 200 papers published since 1952. In this period, 37 hard tick species were reported from 16 orders of avian hosts in Europe. Here we compile a list of these tick species, followed by the English and Latin name of all reported infested bird species, as well as the tick developmental stage and country of origin whenever this information was available. These data allowed a first-hand analysis of general trends regarding how and at which developmental stage of ticks tend to infest avian hosts. Five tick species that were frequently reported from birds and show a broad geographical distribution in the Western Palearctic (Ixodes arboricola, I. frontalis, I. ricinus, Haemaphysalis concinna and Hyalomma marginatum) were also selected for statistical comparisons. Differences were demonstrated between these tick species regarding their association with bird species that typically feed from the ground and those that rarely occur at the soil level. The ecology of these five bird-infesting tick species is also illustrated here according to avian orders, taking into account the ecology (habitat type) and activity (circadian rhythm and feeding level) of most bird species that represent a certain order.

Molecular Detection of Zoonotic and Non-Zoonotic Pathogens from Wild Boars and Their Ticks in the Corsican Wetlands

Corsica is the main French island in the Mediterranean Sea and has high levels of human and animal population movement. Among the local animal species, the wild boar is highly prevalent in the Corsican landscape and in the island’s traditions. Wild boars are the most commonly hunted animals on this island, and can be responsible for the transmission and circulation of pathogens and their vectors. In this study, wild boar samples and ticks were collected in 17 municipalities near wetlands on the Corsican coast. A total of 158 hunted wild boars were sampled (523 samples). Of these samples, 113 were ticks: 96.4% were Dermacentor marginatus, and the remainder were Hyalomma marginatum, Hyalomma scupense and Rhipicephalus sanguineus s.l. Of the wild boar samples, only three blood samples were found to be positive for Babesia spp. Of the tick samples, 90 were found to be positive for tick-borne pathogens (rickettsial species). These results confirm the importance of the wild boar as a host for ticks carrying diseases such as rickettsiosis near wetlands and recreational sites. Our findings also show that the wild boar is a potential carrier of babesiosis in Corsica, a pathogen detected for the first time in wild boars on the island.

Imported Hyalomma ticks in the Netherlands 2018-2020

BACKGROUND

Ticks of the genus Hyalomma, which are vectors for several tick-borne diseases, are occasionally found in areas outside their endemic range including northern parts of Europe. The objective of this study was to analyse adult Hyalomma ticks that were recently found in the Netherlands.

METHODS

Hyalomma ticks were morphologically identified. Cluster analysis, based upon sequence data (cox1 barcoding) for molecular identification, and pathogen detection were performed. Additionally, a cross-sectional survey of horses was conducted to actively search for Hyalomma ticks in summer 2019. Analysis of temperature was done to assess the possibility of (i) introduced engorged nymphs moulting to adults and (ii) establishment of populations in the Netherlands.

RESULTS

Seventeen adult Hyalomma ticks (one in 2018, eleven in 2019, five in 2020) were found by citizens and reported. Fifteen ticks were detected on horses and two on humans. Twelve were identified as H. marginatum, one as H. rufipes and four, of which only photographic images were available, as Hyalomma sp. No Crimean-Congo haemorrhagic fever virus or Babesia/Theileria parasites were detected. One adult tick tested positive for Rickettsia aeschlimannii. In the cross-sectional horse survey, no Hyalomma ticks were found. Analysis of temperatures showed that engorged nymphs arriving on migratory birds in spring were able to moult to adults in 2019 and 2020, and that cumulative daily temperatures in the Netherlands were lower than in areas with established H. marginatum populations.

CONCLUSIONS

Our results show that Hyalomma ticks are regularly introduced in the Netherlands as nymphs. Under the Dutch weather conditions, these nymphs are able to develop to the adult stage, which can be sighted by vigilant citizens. Only one human pathogen, Rickettsia aeschlimannii, was found in one of the ticks. The risk of introduction of tick-borne diseases via Hyalomma ticks on migratory birds is considered to be low. Establishment of permanent Hyalomma populations is considered unlikely under the current Dutch climatic conditions.

Rickettsiales in Italy

There is no updated information on the spread of Rickettsiales in Italy. The purpose of our study is to take stock of the situation on Rickettsiales in Italy by focusing attention on the species identified by molecular methods in humans, in bloodsucking arthropods that could potentially attack humans, and in animals, possible hosts of these Rickettsiales. A computerized search without language restriction was conducted using PubMed updated as of December 31, 2020. The Preferred Reporting Items for Systematic Reviews and Meta-Analyses (PRISMA) methodology was followed. Overall, 36 species of microorganisms belonging to Rickettsiales were found. The only species identified in human tissues were Anaplasma phagocytophilum,Rickettsia conorii, R. conorii subsp. israelensis, R. monacensis, R. massiliae, and R. slovaca. Microorganisms transmissible by bloodsucking arthropods could cause humans pathologies not yet well characterized. It should become routine to study the pathogens present in ticks that have bitten a man and at the same time that molecular studies for the search for Rickettsiales can be performed routinely in people who have suffered bites from bloodsucking arthropods.