Transstadial and transovarial persistence of Babesia divergens DNA in Ixodes ricinus ticks fed on infected blood in a new skin-feeding technique

Pathogens transmitted by Ixodes ricinus

Ixodes ricinus is the most important tick vector in central and western Europe and one of the most researched parasites. However, in the published literature on the tick and the pathogens it transmits, conjecture about specific transmission cycles and the clinical significance of certain microbes is not always clearly separated from confirmed facts. This article aims to present up-to-date, evidence-based information about the well-researched human pathogens tick-borne encephalitis virus, louping-ill virus, Anaplasma phagocytophilum, Borrelia burgdorferi sensu lato and several Babesia species, with a focus on their development in the tick, transmission dynamics and the competent reservoir hosts that support their circulation in the environment. Borrelia miyamotoi, Neoehrlichia mikurensis, Rickettsia helvetica and Rickettsia monacensis, which are much less common causes of disease but may affect immunocompromised patients, are also briefly discussed. Finally, the possible role of I. ricinus in the transmission of Coxiella burnetii, Francisella tularensis, Bartonella spp. and Spiroplasma ixodetis is reviewed.

Challenges for ticks and tick-borne diseases research in Southeast Asia: Insight from the first international symposium in Cambodia

BACKGROUND

Ticks, as critical vectors of a variety of pathogens, pose a significant public health challenge globally. In Southeast Asia (SEA), ticks are responsible for transmitting a diverse array of pathogens affecting humans and animals. The geographical and ecological diversity of SEA provides a unique environment that supports a wide range of tick species, which complicates the management and study of tick-borne diseases (TBDs).

METHODOLOGY/PRINCIPAL FINDINGS

This article synthesizes findings from the first international symposium on ticks and TBDs in Southeast Asia, held in Phnom Penh on June 22 and 23, 2023. It highlights regional efforts to understand tick ecology and pathogen transmission. This paper proposes to present a summary of the various presentations given during the symposium following 3 main parts. The first one is devoted to the state of knowledge regarding ticks and TBDs in SEA countries, with presentations from 6 different countries, namely Cambodia, Indonesia, Laos, Malaysia, Thailand, and Vietnam. The second part focuses on the development of new research approaches on tick-borne pathogens (TBPs) and TBDs. The last part is a summary of the round table discussion held on the final day, with the aim of defining the most important challenges and recommendations for researches on TBP and TBD in the SEA region.

CONCLUSIONS/SIGNIFICANCE

Key topics discussed include advancements in diagnostic tools, such as MALDI-TOF MS and proteomics, and the development of sustainable strategies for tick management and disease prevention. The symposium facilitated the exchange of knowledge and collaborative networks among experts from various disciplines, promoting a unified approach to tackling TBDs in the region. The symposium underscored the need for enhanced surveillance, diagnostics, and inter-regional cooperation to manage the threat of TBDs effectively. Recommendations include the establishment of a regional database for tick identification and the expansion of vector competence studies. These initiatives are crucial for developing targeted interventions and understanding the broader implications of climate change and urbanization on the prevalence of TBDs.

Coinfection of Babesia and Borrelia in the Tick Ixodes ricinus-A Neglected Public Health Issue in Europe?

Ixodes ricinus nymphs and adults removed from humans, and larvae and nymphs from birds, have been analysed for infection with Babesia species and Borrelia species previously in separately published studies. Here, we use the same data set to explore the coinfection pattern of Babesia and Borrelia species in the ticks. We also provide an overview of the ecology and potential public health importance in Sweden of I. ricinus infected both with zoonotic Babesia and Borrelia species. Among 1952 nymphs and adult ticks removed from humans, 3.1% were PCR-positive for Babesia spp. Of these Babesia-positive ticks, 43% were simultaneously Borrelia-positive. Among 1046 immatures of I. ricinus removed from birds, 2.5% were Babesia-positive, of which 38% were coinfected with Borrelia species. This study shows that in I. ricinus infesting humans or birds in Sweden, potentially zoonotic Babesia protozoa sometimes co-occur with human-pathogenic Borrelia spp. Diagnostic tests for Babesia spp. infection are rarely performed in Europe, and the medical significance of this pathogen in Europe could be underestimated.

Tick-borne pathogens in questing adults Dermacentor reticulatus from the Eastern European population (north-eastern Poland)

Dermacentor reticulatus is tick species with an expanding geographical range in Europe, which creates the possibility of spreading microorganisms of significant veterinary and medical importance. The study aimed to investigate the prevalence and genetic diversity of Rickettsia spp., Babesia spp., Borrelia spp. and Anaplasma phagocytophilum in adult D. reticulatus ticks from the Eastern European population in the urban and the natural biotopes of north-eastern Poland. Microorganisms were detected by PCR and identified by DNA sequencing. The overall infection rate of at least one of the pathogens was 29.6%. The predominantly was Rickettsia spp. (27.1%) (with R. raoultii-9.1%) followed by Babesia spp. (2.4%) with B. canis (1.5%) as the most frequent. Based on 18S rRNA gene sequence, three B. canis genotypes were revealed. The prevalence of R. raoultii and B. canis was significantly higher in ticks from natural biotopes. The infection rates of B. afzelii and A. phagocytophilum were determined at 0.9% and 0.3%, respectively. Co-infections were detected in 3.8% of infected ticks. In diagnosing tick-borne diseases in humans, tick-borne lymphadenopathy should not be excluded. The prevalence of different genotypes of B. canis suggests differences in the clinical picture of canine babesiosis in the area.

Simultaneous targeted amplicon deep sequencing and library preparation for a time and cost-effective universal parasite diagnostic sequencing approach

We recently described a targeted amplicon deep sequencing (TADS) strategy that utilizes a nested PCR targeting the 18S rDNA gene of blood-borne parasites. The assay facilitates selective digestion of host DNA by targeting enzyme restriction sites present in vertebrates but absent in parasites. This enriching of parasite-derived amplicon drastically reduces the proportion of host-derived reads during sequencing and results in the sensitive detection of several clinically important blood parasites including Plasmodium spp., Babesia spp., kinetoplastids, and filarial nematodes. Despite these promising results, high costs and the laborious nature of metagenomics sequencing are prohibitive to the routine use of this assay in most laboratories. We describe and evaluate a new metagenomic approach that utilizes a set of primers modified from our original assay that incorporates Illumina barcodes and adapters during the PCR steps. This modification makes amplicons immediately compatible with sequencing on the Illumina MiSeq platform, removing the need for a separate library preparation, which is expensive and time-consuming. We compared this modified assay to our previous nested TADS assay in terms of preparation speed, limit of detection (LOD), and cost. Our modifications reduced assay turnaround times from 7 to 5 days. The cost decreased from approximately $40 per sample to $11 per sample. The modified assay displayed comparable performance in the detection and differentiation of human-infecting Plasmodium spp., Babesia spp., kinetoplastids, and filarial nematodes in clinical samples. The LOD of this modified approach was determined for malaria parasites and remained similar to that previously reported for our earlier assay (0.58 Plasmodium falciparum parasites/µL of blood). These modifications markedly reduced costs and turnaround times, making the assay more amenable to routine diagnostic applications.

Differential associations of horizontally and vertically transmitted symbionts on Ixodes ricinus behaviour and physiology

BACKGROUND

Ixodes ricinus ticks are infected with a large diversity of vertically and horizontally transmitted symbionts. While horizontally transmitted symbionts rely on a vertebrate host for their transmission, vertically transmitted symbionts rely more on the survival of their invertebrate host for transmission. We therefore hypothesized horizontally transmitted symbionts to be associated with increased tick activity to increase host contact rate and vertically transmitted symbionts to be associated with higher tick weight and lipid fraction to promote tick survival.

METHODS

We used a behavioural assay to record the questing activity of I. ricinus ticks. In addition, we measured weight and lipid fraction and determined the presence of ten symbiont species in these ticks using qPCR, of which six were vertically transmitted and four horizontally transmitted.

RESULTS

Vertically transmitted symbionts (e.g. Midichloria mitochondrii) were associated with an increase in tick weight, whereas horizontally transmitted symbionts (e.g. Borrelia burgdorferi sensu lato) were often associated with lower weight and lipid fraction of ticks. Moreover, horizontally transmitted symbionts (e.g. B. burgdorferi s.l.) were associated with increased tick activity, which may benefit pathogen transmission and increases tick-borne disease hazard.

CONCLUSIONS

Our study shows that horizontally and vertically transmitted symbionts differentially influence the behaviour and physiology of I. ricinus and warrants future research to study the underlying mechanisms and effects on transmission dynamics of tick-borne pathogens.

Transfusion-transmitted Babesia spp.: a changing landscape of epidemiology, regulation, and risk mitigation

Babesia spp. are tick-borne parasites with a global distribution and diversity of vertebrate hosts. Over the next several decades, climate change is expected to impact humans, vectors, and vertebrate hosts and change the epidemiology of Babesia. Although humans are dead-end hosts for tick-transmitted Babesia, human-to-human transmission of Babesia spp. from transfusion of red blood cells and whole blood-derived platelet concentrates has been reported. In most patients, transfusion-transmitted Babesia (TTB) results in a moderate-to-severe illness. Currently, in North America, most cases of TTB have been described in the United States. TTB cases outside North America are rare, but case numbers may change over time with increased recognition of babesiosis and as the epidemiology of Babesia is impacted by climate change. Therefore, TTB is a concern of microbiologists working in blood operator settings, as well as in clinical settings where transfusion occurs. Microbiologists play an important role in deploying blood donor screening assays in Babesia endemic regions, identifying changing risks for Babesia in non-endemic areas, investigating recipients of blood products for TTB, and drafting TTB policies and guidelines. In this review, we provide an overview of the clinical presentation and epidemiology of TTB. We identify approaches and technologies to reduce the risk of collecting blood products from Babesia-infected donors and describe how investigations of TTB are undertaken. We also describe how microbiologists in Babesia non-endemic regions can assess for changing risks of TTB and decide when to focus on laboratory-test-based approaches or pathogen reduction to reduce TTB risk.

Honey Bee Larval Hemolymph as a Source of Key Nutrients and Proteins Offers a Promising Medium for Varroa destructor Artificial Rearing

Varroa destructor, a major ectoparasite of the Western honey bee Apis mellifera, is a widespread pest that damages colonies in the Northern Hemisphere. Throughout their lifecycle, V. destructor females feed on almost every developmental stage of their host, from the last larval instar to the adult. The parasite is thought to feed on hemolymph and fat body, although its exact diet and nutritional requirements are poorly known. Using artificial Parafilm™ dummies, we explored the nutrition of V. destructor females and assessed their survival when fed on hemolymph from bee larvae, pupae, or adults. We compared the results with mites fed on synthetic solutions or filtered larval hemolymph. The results showed that the parasites could survive for several days or weeks on different diets. Bee larval hemolymph yielded the highest survival rates, and filtered larval plasma was sufficient to maintain the mites for 14 days or more. This cell-free solution therefore theoretically contains all the necessary nutrients for mite survival. Because some bee proteins are known to be hijacked without being digested by the parasite, we decided to run a proteomic analysis of larval honey bee plasma to highlight the most common proteins in our samples. A list of 54 proteins was compiled, including several energy metabolism proteins such as Vitellogenin, Hexamerin, or Transferrins. These molecules represent key nutrient candidates that could be crucial for V. destructor survival.

Pathogenic Rickettsia, Anaplasma, and Ehrlichia in Rhipicephalus microplus ticks collected from cattle and laboratory hatched tick larvae

BACKGROUND

The order Rickettsiales contains a group of vector-borne gram-negative obligate intracellular bacteria, which often cause human emerging infectious diseases and economic losses for dairy and meat industries. The purpose of this study is to investigate the distribution of the pathogens including Rickettsia spp., Anaplasma spp., and Ehrlichia spp. in the order Rickettsiales in ticks from Yueyang, a prefecture-level city of Hunan Province in Sothern China, and assess the potentiality of transovarial transmission of these rickettsial organisms.

METHODS

Ticks were collected from cattle in a farm in Yueyang City and the tick DNA was used as template to amplify the htrA, rrs, gltA, ompA and ompB genes of Rickettsia as well as rrs and groEL genes of Anaplasma and Ehrlichia.

RESULTS

All ticks (465) collected were the cattle tick, Rhipicephalus microplus. PCR showed the minimum infection rate (MIR) was 1.5% (7/465) for Candidatus Rickettsia xinyangensis, 1.9% (9/465) for C. Anaplasma boleense, 1.3% (6/465) for Anaplasma platys, 0.6% (3/465) for A. marginale, and 1.17% (2/465) for each of A. bovis, Ehrlichia minasensis, and a non-classified Ehrlichia sp. A human pathogen, C. Rickettsia xinyangensis and A. platys were detected in 100% (3/3) and 33.3% (2/6) laboratory-hatched larval pools from infected females respectively.

CONCLUSION

Our study revealed a diversity of pathogenic rickettsial species in R. microplus ticks from Hunan Province suggesting a threat to people and animals in China. This study also provided the first molecular evidence for the potential transovarial transmission of C. Rickettsia xinyangensis and A. platys in R. microplus, indicating that R. microplus may act as the host of these two pathogens.

Molecular survey of Cytauxzoon spp. and Hepatozoon spp. in felids using a novel real-time PCR approach

Tick-transmitted apicomplexans of the genera Cytauxzoon and Hepatozoon affect a wide range of felids worldwide, but little is known about them. Recently, several studies addressed the species circulating in Europe, their distribution, and their hosts. Molecular assays are the method of choice for their detection. Unfortunately, conventional PCRs already described are time- and cost-consuming and specific for either Hepatozoon or Cytauxzoon detection. This study was developed to evaluate (i) the occurrence of Cytauxzoon and Hepatozoon in felids using a fast and cost-saving real-time PCR capable of detecting both protozoa simultaneously, (ii) the distribution of Cytauxzoon and Hepatozoon species in north-eastern Italy, and (iii) the involvement of other susceptible felid hosts in the same area. An SYBR^® Green-based real-time PCR with primers targeting the 18S-rRNA was validated and applied to 237 felid samples, i.e., whole blood from 206 domestic cats and 12 captive exotic felids, and tissues from 19 wildcats. Positive results were obtained by melting temperature curve analysis due to the specific melting peak (i.e., 81°C Cytauxzoon spp.; 78-78.5°C Hepatozoon spp.). Positive samples were subjected to conventional PCR, followed by sequencing for species identification. Phylogenetic analyses were performed to assess relatedness among European isolates. Data on domestic cats (age class, sex, origin, management, and lifestyle) were recorded, and statistical analyses were performed to identify potential risk factors. A total of 31 (15%) domestic cats were positive for Hepatozoon spp. (i.e., 12 for H. felis, 19 for H. silvestris), while six (2.9%) for C. europaeus. The prevalence of Hepatozoon felis was significantly (p < 0.05) higher in domestic cats, while H. silvestris was higher in strays and animals from the Eastern region (i.e., Friuli-Venezia Giulia). Cytauxzoon europaeus was detected only in stray cats from Friuli-Venezia Giulia (province of Trieste). Among captive felids, one tiger was infected with H. felis and another with H. silvestris; eight out of 19 (42%) wildcats were positive for Hepatozoon spp. (i.e., six with H. felis, two with H. silvestris) and four out of 19 (21%) for Cytauxzoon europaeus. Outdoor lifestyle and origin (i.e., Friuli-Venezia Giulia region) were the most relevant risk factors for H. silvestris and C. europeus infections. Conversely, H. felis was most frequently isolated from domestic cats, suggesting different modes of transmission.

In vitro feeding of Hyalomma excavatum and Hyalomma marginatum tick species

The rearing of ticks is an important technique for studies aiming to elucidate the course and pathogenesis of tick-borne diseases (TBDs). TBDs caused by protozoans (Theileria, Babesia) and bacteria (Anaplasma/Ehrlichia) impose a serious constraint upon livestock health and production in tropical and sub-tropical regions where the distributions of host, pathogen, and vector overlap. This study focuses on Hyalomma marginatum, one of the most important Hyalomma species in the Mediterranean region, being a vector of the virus that causes Crimean-Congo haemorrhagic fever in humans, together with H. excavatum, a vector of Theileria annulata, an important protozoan of cattle. The adaptation of ticks to feeding on artificial membranes allows the creation of model systems that can be put to use examining the underlying mechanisms of pathogen transmission by ticks. Silicone membranes, in particular, offer researchers the flexibility to adjust membrane thickness and content during artificial feeding. The aim of the present study was to develop an artificial feeding technique using silicone-based membranes for all developmental stages of H. excavatum and H. marginatum ticks. Attachment rates after feeding on silicone membranes for females H. marginatum and H. excavatum were 8.33% (8/96) and 7.95% (7/88), respectively. The use of cow hair as a stimulant increased the attachment rate of H. marginatum adults in comparison to other stimulants. The engorgement of H. marginatum and H. excavatum females took 20.5 and 23 days with average weights of 307.85 and 260.64 mg, respectively. Although both tick species could complete egg-laying, and this was followed by hatching of larvae; their larvae and nymphs could not be fed artificially. Taken together, the results of the present study clearly indicate that silicone membranes are suitable for feeding of H. excavatum and H. marginatum adult ticks, supporting engorgement, laying of eggs, and hatching of the larvae. They thus represent a versatile tool for studying transmission mechanisms of tick-borne pathogens. Further studies are warranted to examine attachment and feeding behaviours in order to increase the success of artificial feeding of larvae and nymphal stages.

Transovarial transmission of pathogenic protozoa and rickettsial organisms in ticks

Transovarial transmission (TOT) is an efficient vertical transmission of pathogens that is observed in many arthropod vectors. This method seems to be an evolutionarily unique development observed only in Babesia sensu stricto (clade VI) and Rickettsia spp., whereas transstadial transmission is the common/default way of transmission. Transovarial transmission does not necessarily contribute to the amplification of tick-borne pathogens but does contribute to the maintenance of disease in the environment. This review aims to provide an updated summary of previous reports on TOT of tick-borne pathogens.

Apicomplexan haemoparasites in domestic cats in Romania

BACKGROUND

Apicomplexan haemoparasites are protozoans that infect a variety of domestic and wild animal species, as well as humans. Data regarding haemoprotozoans in domestic cats are limited; therefore, the aim of this study was to assess the occurrence of Babesia spp., Cytauxzoon spp., and Hepatozoon spp. in domestic cats in Romania using molecular tools.

METHODS

Blood samples from 371 domestic cats were screened for the presence of piroplasmids. All samples that yielded a visible band in agarose gels were subsequently tested by specific assays targeting the 18S rDNA of Babesia spp., Cytauxzoon spp., and Hepatozoon spp. Moreover, nested PCR assays targeting mitochondrial genes of Babesia spp. were used for screening of all Babesia spp. 18S rDNA-positive samples.

RESULTS

From the total number of sampled cats, 19.4% were positive in the PCR assay targeting piroplasmids. Babesia spp. were identified in 15.1% of cats, while 0.5% were positive for Hepatozoon spp. Molecular analyses confirmed the presence of Babesia canis. No samples were positive for Cytauxzoon spp.

CONCLUSIONS

The high infection rates of domestic cats with Babesia spp. and the need for species differentiation highlight the importance of mitochondrial genes as targets for molecular protocols.

Description of a novel Babesia sp. genotype from a naturally infected Eurasian lynx (Lynx lynx) in Anatolia, Turkey, with remarks on its morphology and phylogenetic relation to other piroplasmid species

There are very limited data on Babesia species infecting lynx species worldwide, and almost nothing is known about babesias in the Eurasian lynx, the most widely distributed wild feline species in the Palearctic geography. This study describes a novel Babesia sp. genotype in a free-living Eurasian lynx in Turkey, named tentatively as 'Babesia sp. lynx', and its integrated genetic and morphological features. Phylogenetic analyses of piroplasmids with the novel Babesia sp. genotype in the current study indicated that this genotype falls into the 'carnivore clade A' of Babesia sensu stricto (true babesias), at the level of different genes (mainly 18S rRNA, ITS1, ITS2, and cyt b) and is monophyletic with the Babesia sp. Ankara genotype, previously observed in Turkey. Additionally, the constructed phylogenetic trees showed that the Babesia sp. lynx genotype infecting the Eurasian lynx is closely related to certain domestic and wild carnivore babesias, mainly Babesia rossi, Babesia presentii, and Babesia pisicii, at the level of different genes. This study also genetically barcoded the lynx infected with the Babesia sp. lynx and Haemaphysalis erinacei, and specimens collected from the animal revealed significant genetic variations between the sample Ha. erinacei and Babesia sp. Ankara-related Ha. erinacei that persists with sympatric populations in Central Anatolia. The lynx infected with the Babesia sp. lynx genotype was also found to be coinfected with Hepatozoon felis, an adeleorinid tick-borne protozoan parasite infecting wild and domestic felids, confirming for the first time its presence in a lynx species. Therefore, this study is the first to describe a potential novel Babesia sp. using its both morphological and phylogenetic characteristics in a lynx species. Adding the Babesia sp. lynx genotype to the phylogeny of feline piroplasmids significantly expands our knowledge of feline babesias in the Palearctic geography and their putative coevolution with their vertebrate hosts.

Evaluation of Vector Competence of Ixodes Ticks for Kemerovo Virus

Tick-borne viruses are responsible for various symptoms in humans and animals, ranging from simple fever to neurological disorders or haemorrhagic fevers. The Kemerovo virus (KEMV) is a tick-borne orbivirus, and it has been suspected to be responsible for human encephalitis cases in Russia and central Europe. It has been isolated from Ixodes persulcatus and Ixodes ricinus ticks. In a previous study, we assessed the vector competence of I. ricinus larvae from Slovakia for KEMV, using an artificial feeding system. In the current study, we used the same system to infect different tick population/species, including I. ricinus larvae from France and nymphs from Slovakia, and I. persulcatus larvae from Russia. We successfully confirmed the first two criteria of vector competence, namely, virus acquisition and trans-stadial transmission, for both tick species that we tested. The estimated infection rates of engorged and moulted ticks suggest specificities between viral strains and tick species/developmental stages.

Tick-Borne Pathogens, Babesia spp. and Borrelia burgdorferi s.l., in Sled and Companion Dogs from Central and North-Eastern Europe

Ticks are important vectors of numerous pathogens of medical and veterinary significance. The aim of the current study was to determine the prevalence of Babesia spp. and Borrelia burgdorferi s.l. in sled and pet dogs from Central and North-Eastern Europe. Neither Babesia spp. nor Borrelia burgdorferi s.l. infections were detected in sled dogs from seven countries (Poland, Lithuania, Latvia, Estonia, Belarus, Russia and Finland). The DNA of Babesia spp. was detected in 100% of symptomatic and 5.4% of asymptomatic pet dogs from Poland. Similarly, the DNA of Babesia spp. was identified in 82% of symptomatic and 3.8% of asymptomatic pet dogs from Ukraine. The DNA of Borrelia burgdorferi s.l. was detected in 4.4% of pet dogs. Molecular typing confirmed the presence of Babesia canis and Borrelia burgdorferi sensu stricto (s.s.) in selected samples. Four dogs were co-infected by B. canis and Borrelia burgdorferi s.l. Tick-borne pathogens constitute a serious health threat to pet dogs in Central and South-Eastern Europe, but were not observed among sled dogs from the same region of Europe nor in the Baltic countries.

Evaluation of two artificial infection methods of live ticks as tools for studying interactions between tick-borne viruses and their tick vectors

Up to 170 tick-borne viruses (TBVs) have been identified to date. However, there is a paucity of information regarding TBVs and their interaction with respective vectors, limiting the development of new effective and urgently needed control methods. To overcome this gap of knowledge, it is essential to reproduce transmission cycles under controlled laboratory conditions. In this study we assessed an artificial feeding system (AFS) and an immersion technique (IT) to infect Ixodes ricinus ticks with tick-borne encephalitis (TBE) and Kemerovo (KEM) virus, both known to be transmitted predominantly by ixodid ticks. Both methods permitted TBEV acquisition by ticks and we further confirmed virus trans-stadial transmission and onward transmission to a vertebrate host. However, only artificial feeding system allowed to demonstrate both acquisition by ticks and trans-stadial transmission for KEMV. Yet we did not observe transmission of KEMV to mice (IFNAR^-/- or BALB/c). Artificial infection methods of ticks are important tools to study tick-virus interactions. When optimally used under laboratory settings, they provide important insights into tick-borne virus transmission cycles.

Investigation of Transovarial Transmission of Bartonella henselae in Rhipicephalus sanguineus sensu lato Ticks Using Artificial Feeding

Bartonella henselae is a slow-growing, Gram-negative bacterium that causes cat scratch disease in humans. A transstadial transmission of the bacteria from larvae to nymphs of Rhipicephalus sanguineus sensu lato (s.l.) ticks, suspected to be a potential vector of the bacteria, has been previously demonstrated. The present study aims to investigate transovarial transmission of B. henselae from R. sanguineus s.l. adults to their instars. Adult ticks (25 males and 25 females) were fed through an artificial feeding system on B. henselae-infected goat blood for 14 days, and 300 larvae derived from the experimentally B. henselae-infected females were fed on noninfected goat blood for 7 days. Nested PCR and culture were used to detect and isolate B. henselae in ticks and blood samples. Bartonella henselae DNA was detected in midguts, salivary glands, and carcasses of the semi-engorged adults and pooled tick feces (during feeding and post-feeding periods). After the oviposition period, B. henselae DNA was detected in salivary glands of females (33.3%), but not in pooled eggs or larvae derived from the infected females. However, B. henselae DNA was detected by nested PCR from the blood sample during larval feeding, while no viable B. henselae was isolated by culture. According to our findings, following infected blood meal, B. henselae could remain in the tick midguts, move to other tissues including salivary glands, and then be shed through tick feces with limited persistency. The presence of bacterial DNA in the blood during larval feeding shows the possibility of transovarial transmission of B. henselae in R. sanguineus s.l. ticks.

Infection rates, species diversity, and distribution of zoonotic Babesia parasites in ticks: a global systematic review and meta-analysis

Zoonotic Babesia species are emerging public health threats globally, and are the cause of a mild to severe malaria-like disease which may be life threatening in immunocompromised individuals. In this study, we determine the global infection rate, distribution, and the diversity of zoonotic Babesia species in tick vectors using a systematic review and meta-analysis. We used the random-effects model to pool data and determined quality of individual studies using the Joanna Briggs Institute critical appraisal instrument for prevalence studies, heterogeneity using Cochran's Q test, and across study bias using Egger's regression test. Herein, we reported a 2.16% (3915/175345, 95% CI: 1.76-2.66) global infection rate of zoonotic Babesia species (B. divergens, B. microti, and B. venatorum) in tick vectors across 36 countries and 4 continents. Sub-group infection rates ranged between 0.65% (95% CI: 0.09-4.49) and 3.70% (95% CI: 2.61-5.21). B. microti was the most prevalent (1.79%, 95% CI: 1.38-2.31) species reported in ticks, while Ixodes scapularis recorded the highest infection rate (3.92%, 95% CI: 2.55-5.99). Larvae 4.18% (95% CI: 2.15-7.97) and females 4.08% (95% CI: 2.56-6.43) were the tick stage and sex with the highest infection rates. The presence of B. divergens, B. microti, and B. venatorum in tick vectors as revealed by the present study suggests possible risk of transmission of these pathogens to humans, especially occupationally exposed population. The control of tick vectors through chemical and biological methods as well as the use of repellants and appropriate clothing by occupationally exposed population are suggested to curtail the epidemiologic, economic, and public health threats associated with this emerging public health crisis.

Experimental Infection of Ticks: An Essential Tool for the Analysis of Babesia Species Biology and Transmission

Babesiosis is one of the most important tick-borne diseases in veterinary health, impacting mainly cattle, equidae, and canidae, and limiting the development of livestock industries worldwide. In humans, babesiosis is considered to be an emerging disease mostly due to Babesia divergens in Europe and Babesia microti in America. Despite this importance, our knowledge of Babesia sp. transmission by ticks is incomplete. The complexity of vectorial systems involving the vector, vertebrate host, and pathogen, as well as the complex feeding biology of ticks, may be part of the reason for the existing gaps in our knowledge. Indeed, this complexity renders the implementation of experimental systems that are as close as possible to natural conditions and allowing the study of tick-host-parasite interactions, quite difficult. However, it is unlikely that the development of more effective and sustainable control measures against babesiosis will emerge unless significant progress can be made in understanding this tripartite relationship. The various methods used to date to achieve tick transmission of Babesia spp. of medical and veterinary importance under experimental conditions are reviewed and discussed here.

The raccoon dog (Nyctereutes procyonoides) as a reservoir of zoonotic diseases in Denmark

Raccoon dogs have successfully invaded Europe, including Denmark. Raccoon dogs are potential vectors and reservoir hosts of several zoonotic pathogens and thus have the potential for posing a threat to both human and animal health. This study includes analysis of four zoonotic parasites, 16 tick-borne pathogens and two pathogen groups from 292 raccoon dogs collected from January 2018 to December 2018. The raccoon dogs were received as a part of the Danish national wildlife surveillance program and were hunted, found dead or road killed. The raccoon dogs were screened for Alaria alata and Echinococcus multilocularis eggs in faeces by microscopy and PCR, respectively, Trichinella spp. larvae in muscles by digestion, antibodies against Toxoplasma gondii by ELISA and screening of ticks for pathogens by fluidigm real-time PCR. All raccoon dogs tested negative for E. multilocularis and Trichinella spp., while 32.9% excreted A. alata eggs and 42.7% were T. gondii sero-positive. Five tick-borne pathogens were identified in ticks collected from 15 raccoon dogs, namely Anaplasma phagocytophilum (20.0%), Babesia venatorum (6.7%), Borrelia miyamotoi (6.7%), Neoehrlichia mikurensis (6.7%) and Rickettsia helvetica (60.0%). We identified raccoon dogs from Denmark as an important reservoir of T. gondii and A. alata infection to other hosts, including humans, while raccoon dogs appear as a negligible reservoir of E. multilocularis and Trichinella spp. infections. Our results suggest that raccoon dogs may be a reservoir of A. phagocytophilum.

Ticks and their epidemiological role in Slovakia: from the past till present

In Slovakia, 22 tick species have been found to occur to date. Among them, Ixodes ricinus, Dermacentor reticulatus, D. marginatus and marginally Haemaphysalis concinna, H. inermis and H. punctata have been identified as the species of public health relevance. Ticks in Slovakia were found to harbour and transmit zoonotic and/or potentially zoonotic agents such as tick-borne encephalitis virus (TBEV), spirochaetes of the Borrelia burgdorferi sensu lato (s.l.) complex, the relapsing fever sprirochaete Borrelia miyamotoi, bacteria belonging to the orders Rickettsiales (Rickettsia spp., Anaplasma phagocytophilum, Neoehrlichia mikurensis), Legionellales (Coxiella burnetii), and Thiotrichales (Francisella tularensis), and Babesia spp. parasites (order Piroplasmida). Ixodes ricinus is the principal vector of the largest variety of microorganisms including viruses, bacteria and piroplasms. TBEV, B. burgdorferi s.l., rickettsiae of the spotted fever group, C. burnetii and F. tularensis have been found to cause serious diseases in humans, whereas B. miyamotoi, A. phagocytophilum, N. mikurensis, Babesia microti, and B. venatorum pose lower or potential risk to humans. Distribution of TBEV has a focal character. During the last few decades, new tick-borne encephalitis (TBE) foci and their spread to new areas have been registered and TBE incidence rates have increased. Moreover, Slovakia reports the highest rates of alimentary TBE infections among the European countries. Lyme borreliosis (LB) spirochaetes are spread throughout the distribution range of I. ricinus. Incidence rates of LB have shown a slightly increasing trend since 2010. Only a few sporadic cases of human rickettsiosis, anaplasmosis and babesiosis have been confirmed thus far in Slovakia. The latest large outbreaks of Q fever and tularaemia were recorded in 1993 and 1967, respectively. Since then, a few human cases of Q fever have been reported almost each year. Changes in the epidemiological characteristics and clinical forms of tularaemia have been observed during the last few decades. Global changes and development of modern molecular tools led to the discovery and identification of emerging or new tick-borne microorganisms and symbionts with unknown zoonotic potential. In this review, we provide a historical overview of research on ticks and tick-borne pathogens in Slovakia with the most important milestones and recent findings, and outline future directions in the investigation of ticks as ectoparasites and vectors of zoonotic agents and in the study of tick-borne diseases.

Theileria equi and Babesia caballi in horses in the Czech Republic

Theileria equi and Babesia caballi are protozoan agents causing equine piroplasmosis, endemic in countries all over the world. The aim of this study was to detect antibodies to T. equi and B. caballi in horses in the Czech Republic and to investigate the origin of the infection. Blood sera from 711 horses were examined with competitive enzyme-linked immunosorbent assay; positive samples were verified with indirect fluorescence immunoassay. Antibodies to T. equi and B. caballi were detected in eight (1.1%) and three (0.4%) horses, respectively. Infection with T. equi was confirmed by PCR and sequencing in the blood of five serologically positive horses. An autochthonous origin of T. equi infection could not be excluded in two (0.3%) horses. Intensive movement of horses across European countries and the expanding occurrence of competent tick vector Dermacentor reticulatus in the Czech Republic create an increasing risk of establishing active foci of equine piroplasmosis in the country.

Prevalence of Babesia canis DNA in Ixodes ricinus ticks collected in forest and urban ecosystems in west-central Poland

Babesia canis, a widely distributed European tick-borne protozoan haemoparasite, causes canine babesiosis, the most important tick-borne disease afflicting dogs worldwide. The meadow tick, Dermacentor reticulatus, is considered to be the primary vector of this parasite in central Europe. Females of the more broadly distributed and medically important castor bean tick, Ixodes ricinus, also commonly feed upon dogs, but their role in the enzootic transmission cycle of B. canis is unclear. Here, we screened 1,598 host-seeking I. ricinus ticks collected from two different ecosystems, forest stands vs. urban recreational forests, for the presence of B. canis DNA. Ticks were sampled during their two seasonal peaks of activity, spring (May/June) and late summer (September). Babesia species were identified by amplification and sequencing of a hypervariable 18S rRNA gene fragment. Babesia canis was the only piroplasm detected in 13% of 200 larvae and 8.2% of 324 nymphs in the forest ecosystems. In urban recreational areas, B. canis DNA was found in 1.5% of 460 nymphs, 3.5% of 289 females and 3.2% of 280 males. Additionally, three samples, including one female, one male, and one nymph, were co-infected with B. venatorum and one nymph with B. divergens or B. capreoli. Our findings implicate that B. canis can be transmitted transovarially and maintained transstadially within populations of I. ricinus, but the vector competence of I. ricinus for transmitting B. canis remains to be investigated.

Of fungi and ticks: Morphological and molecular characterization of fungal contaminants of a laboratory-reared Ixodes ricinus colony

Establishing and maintaining tick colonies in the laboratory is essential for studying their biology and pathogen transmission, or for the development of new tick control methods. Due to their requirement for very high humidity, these laboratory-bred colonies are frequently subject to fungal contamination. In the present study, we aimed to identify the fungal species that contaminated a laboratory-reared colony of Ixodes ricinus through microscopic observation and molecular identification. We identified three different taxa isolated from the ticks: Aspergillus parasiticus, Penicillium steckii, and Scopulariopsis brevicaulis. These three species are usually regarded as environmental saprophytic molds but both direct and indirect evidence suggest that they could also be considered as entomopathogenic fungi. Although we do not have any direct evidence that the fungi isolated from I. ricinus in this study could cause lethal infections in ticks, we observed that once infected, heavy fungal growth coupled with very high mortality rates suggest that studying the entomopathogenic potential of these fungi could be relevant to biological tick control.

Evaluating Transmission Paths for Three Different Bartonella spp. in Ixodes ricinus Ticks Using Artificial Feeding

Bartonellae are facultative intracellular alpha-proteobacteria often transmitted by arthropods. Ixodes ricinus is the most important vector for arthropod-borne pathogens in Europe. However, its vector competence for Bartonella spp. is still unclear. This study aimed to experimentally compare its vector competence for three Bartonella species: B. henselae, B. grahamii, and B. schoenbuchensis. A total of 1333 ticks (1021 nymphs and 312 adults) were separated into four groups, one for each pathogen and a negative control group. Ticks were fed artificially with bovine blood spiked with the respective Bartonella species. DNA was extracted from selected ticks to verify Bartonella-infection by PCR. DNA of Bartonella spp. was detected in 34% of nymphs and females after feeding. The best engorgement results were obtained by ticks fed with B. henselae-spiked blood (65.3%) and B. schoenbuchensis (61.6%). Significantly more nymphs fed on infected blood (37.3%) molted into adults compared to the control group (11.4%). Bartonella DNA was found in 22% of eggs laid by previously infected females and in 8.6% of adults molted from infected nymphs. The transovarial and transstadial transmission of bartonellae suggest that I. ricinus could be a potential vector for three bacteria.

Artificial Feeding of All Consecutive Life Stages of Ixodes ricinus

The hard tick Ixodes ricinus is an obligate hematophagous arthropod and the main vector for several zoonotic diseases. The life cycle of this three-host tick species was completed for the first time in vitro by feeding all consecutive life stages using an artificial tick feeding system (ATFS) on heparinized bovine blood supplemented with glucose, adenosine triphosphate, and gentamicin. Relevant physiological parameters were compared to ticks fed on cattle (in vivo). All in vitro feedings lasted significantly longer and the mean engorgement weight of F₀ adults and F₁ larvae and nymphs was significantly lower compared to ticks fed in vivo. The proportions of engorged ticks were significantly lower for in vitro fed adults and nymphs as well, but higher for in vitro fed larvae. F₁-females fed on blood supplemented with vitamin B had a higher detachment proportion and engorgement weight compared to F₁-females fed on blood without vitamin B, suggesting that vitamin B supplementation is essential in the artificial feeding of I. ricinus ticks previously exposed to gentamicin.

Three Babesia species in Ixodes ricinus ticks from migratory birds in Sweden

Background

Migratory birds can cross geographical and environmental barriers and are thereby able to facilitate transmission of tick-borne pathogens both as carriers of infected ticks and as reservoirs of pathogenic microorganisms. Ixodes ricinus is one of the most abundant tick species in the Northern Hemisphere and a main vector of several Babesia species, some which pose a potential threat to human and animal health. At present only two cases of overt babesiosis in humans have so far been reported in Sweden. To better understand the potential role of birds as disseminators of zoonotic Babesia protozoan parasites, we investigated the presence of Babesia species in ticks removed from migratory birds.

Methods

Ticks were collected from birds captured at Ottenby Bird Observatory, south-eastern Sweden, from March to November 2009. Ticks were molecularly identified to species, and morphologically to developmental stage, and the presence of Babesia protozoan parasites was determined by real-time PCR.

Results

In total, 4601 migratory birds of 65 species were examined for tick infestation. Ticks removed from these birds have previously been investigated for the presence of Borrelia bacteria and the tick-borne encephalitis virus. In the present study, a total of 1102 ticks were available for molecular analysis of Babesia protozoan parasites. We found that 2.4% of the ticks examined, all I. ricinus, were positive for mammal-associated Babesia species. Out of all Babesia-positive samples, Babesia venatorum was the most prevalent (58%) species, followed by Babesia microti (38%) and Babesia capreoli (4.0%). B. venatorum and B. capreoli were detected in I. ricinus larvae, whereas B. microti was only present in I. ricinus nymphs. This supports the view that the two first-mentioned species are vertically (transovarially) transmitted in the tick population, in contrast to B. microti. The largest number of Babesia-infected ticks was removed from the common redstart (Phoenicurus phoenicurus) and European robin (Erithacus rubecula).

Conclusions

This study reveals that Babesia protozoan parasites are present in ticks infesting migratory birds in south-eastern Sweden, which could potentially lead to the dissemination of these tick-borne microorganisms into new areas, thus posing a threat to humans and other mammals.

Supplementary Information

The online version contains supplementary material available at 10.1186/s13071-021-04684-8.

Circulation of Babesia Species and Their Exposure to Humans through Ixodes Ricinus

Human babesiosis in Europe has been attributed to infection with Babesia divergens and, to a lesser extent, with Babesia venatorum and Babesia microti, which are all transmitted to humans through a bite of Ixodes ricinus. These Babesia species circulate in the Netherlands, but autochthonous human babesiosis cases have not been reported so far. To gain more insight into the natural sources of these Babesia species, their presence in reservoir hosts and in I. ricinus was examined. Moreover, part of the ticks were tested for co-infections with other tick borne pathogens. In a cross-sectional study, qPCR-detection was used to determine the presence of Babesia species in 4611 tissue samples from 27 mammalian species and 13 bird species. Reverse line blotting (RLB) and qPCR detection of Babesia species were used to test 25,849 questing I. ricinus. Fragments of the 18S rDNA and cytochrome c oxidase subunit I (COI) gene from PCR-positive isolates were sequenced for confirmation and species identification and species-specific PCR reactions were performed on samples with suspected mixed infections. Babesia microti was found in two widespread rodent species: Myodes glareolus and Apodemus sylvaticus, whereas B. divergens was detected in the geographically restricted Cervus elaphus and Bison bonasus, and occasionally in free-ranging Ovis aries. B. venatorum was detected in the ubiquitous Capreolus capreolus, and occasionally in free-ranging O. aries. Species-specific PCR revealed co-infections in C. capreolus and C. elaphus, resulting in higher prevalence of B. venatorum and B. divergens than disclosed by qPCR detection, followed by 18S rDNA and COI sequencing. The non-zoonotic Babesia species found were Babesia capreoli, Babesia vulpes, Babesia sp. deer clade, and badger-associated Babesia species. The infection rate of zoonotic Babesia species in questing I. ricinus ticks was higher for Babesia clade I (2.6%) than Babesia clade X (1.9%). Co-infection of B. microti with Borrelia burgdorferi sensu lato and Neoehrlichia mikurensis in questing nymphs occurred more than expected, which reflects their mutual reservoir hosts, and suggests the possibility of co-transmission of these three pathogens to humans during a tick bite. The ubiquitous spread and abundance of B. microti and B. venatorum in their reservoir hosts and questing ticks imply some level of human exposure through tick bites. The restricted distribution of the wild reservoir hosts for B. divergens and its low infection rate in ticks might contribute to the absence of reported autochthonous cases of human babesiosis in the Netherlands.

Symbiont dynamics during the blood meal of Ixodes ricinus nymphs differ according to their sex

Ticks harbour rich and diverse microbiota and, among the microorganisms associated with them, endosymbionts are the subject of a growing interest due to their crucial role in the biology of their arthropod host. Midichloria mitochondrii is the main endosymbiont of the European tick Ixodes ricinus and is found in abundance in all I. ricinus females, while at a much lower density in males, where it is even absent in 56 % of the individuals. This endosymbiont is also known to increase in numbers after the blood meal of larvae, nymphs or females. Because of this difference in the prevalence of M. mitochondrii between the two sexes, surveying the density of these bacteria in nymphs that will become either females or males could help to understand the behaviour of Midichloria in its arthropod host. To this aim, we have set up an experimental design by building 3 groups of unfed nymphs based on their scutum and hypostome lengths. After engorgement, weighing and moulting of a subset of the nymphs, a significant difference in sex-ratio among the 3 groups was observed. In parallel, Midichloria load in individual nymphs was quantified by qPCR both before and after engorgement. No difference in either body mass or Midichloria load was observed at the unfed stage, but following engorgement, both features were significantly different between each size group. Our results demonstrate that symbiont dynamics during nymphal engorgement is different between the two sexes, resulting in a significantly higher Midichloria load in nymphs that will become females. The consequences of those findings on our understanding of the interplay between the endosymbiont and its arthropod host are discussed.

Applications of artificial membrane feeding for ixodid ticks

Ticks are obligatory hematophagous ectoparasites that feed on a large variety of vertebrates. In the laboratory, animals (mainly mice and rabbits) are used to maintain tick colonies. However, the use of animals to rear ticks can be expensive and requires dedicated animal facilities. In addition, research institutions are committed to the principle of 3Rs (Replacement, Reduction and Refinement), which encourages the use of alternatives to animals when possible. The development of artificial membrane systems has provided an alternative to animals, at least for some tick species. Over the years, different modifications in artificial feeding systems have led to new applications, including acaricide testing, tick-pathogen interaction, and novel approaches to study tick physiology. Although artificial membrane feeding still has some limitations, the method can provide numerous advantages, including the standardization of acaricide treatments under controlled conditions, an alternative to animals for tick rearing, and reduction of cost associated with animals and animal housing facilities. In this review, we summarized the evolution of tick feeding membranes and their applications over time, explaining the modifications incorporated to study tick physiology, tick-pathogen interactions, and acaricide testing.

Challenges in Tick-Borne Pathogen Detection: The Case for Babesia spp. Identification in the Tick Vector

The causative agents of Babesiosis are intraerythrocytic protozoa of the genus Babesia. Babesia parasites are present around the world, affecting several mammals including humans, pets and livestock, hence its medical and veterinary relevance. Babesia spp. detection in its invertebrate host is a main point in understanding the biology of the parasite to acquire more knowledge on the host–Babesia–vector interactions, as increasing knowledge of the Babesia lifecycle and babesiosis epidemiology can help prevent babesiosis outbreaks in susceptible mammals. The aim of the present review is to highlight the newest findings in this field, based on a bibliographic compilation of research studies recently carried out for the detection of the main Babesia species found in tick vectors affecting mammalian hosts, including the different tick stages such as adult ticks, larvae, nymphs and eggs, as well as the detection method implemented: microscopic tools for parasite identification and molecular tools for parasite DNA detection by conventional PCR, nested-PCR, PCR-RFLP, PCR-RLB hybridization, real time-PCR, LAMP and RAP assays. Although molecular identification of Babesia parasites has been achieved in several tick species and tissue samples, it is still necessary to carry out transmission experiments through biological models to confirm the vectorial capacity of various tick species.

Sensitive universal detection of blood parasites by selective pathogen-DNA enrichment and deep amplicon sequencing

BACKGROUND

Targeted amplicon deep sequencing (TADS) has enabled characterization of diverse bacterial communities, yet the application of TADS to communities of parasites has been relatively slow to advance. The greatest obstacle to this has been the genetic diversity of parasitic agents, which include helminths, protozoa, arthropods, and some acanthocephalans. Meanwhile, universal amplification of conserved loci from all parasites without amplifying host DNA has proven challenging. Pan-eukaryotic PCRs preferentially amplify the more abundant host DNA, obscuring parasite-derived reads following TADS. Flaherty et al. (2018) described a pan-parasitic TADS method involving amplification of eukaryotic 18S rDNA regions possessing restriction sites only in vertebrates. Using this method, host DNA in total DNA extracts could be selectively digested prior to PCR using restriction enzymes, thereby increasing the number of parasite-derived reads obtained following NGS. This approach showed promise though was only as sensitive as conventional PCR.

RESULTS

Here, we expand on this work by designing a second set of pan-eukaryotic primers flanking the priming sites already described, enabling nested PCR amplification of the established 18S rDNA target. This nested approach facilitated introduction of a second restriction digestion between the first and second PCR, reducing the proportional mass of amplifiable host-derived DNA while increasing the number of PCR amplification cycles. We applied this method to blood specimens containing Babesia, Plasmodium, various kinetoplastids, and filarial nematodes and confirmed its limit of detection (LOD) to be approximately 10-fold lower than previously described, falling within the range of most qPCR methods.

CONCLUSIONS

The assay detects and differentiates the major malaria parasites of humans, along with several other clinically important blood parasites. This represents an important step towards a TADS-based universal parasite diagnostic (UPDx) test with a sufficient LOD for routine applications. Video Abstract.

Vector competence of Rhipicephalus sanguineus sensu stricto for Anaplasma platys

Anaplasma platys is a Gram-negative, obligate intracellular bacteria that causes canine infectious cyclic thrombocytopenia in dogs. The brown dog tick Rhipicephalus sanguineus sensu lato is presumed to be the vector of A. platys based on the overlap in distribution of R. sanguineus and A. platys infections, detection of A. platys DNA in both flat and engorged field-collected R. sanguineus, and the fact that dogs are primary hosts of both brown dog ticks and A. platys. However, the only study evaluating the vector competence of R. sanguineus for A. platys under controlled laboratory conditions reported an apparent inability of ticks to acquire or maintain the pathogen. In 2016, engorged female Rhipicephalus sanguineus sensu stricto ticks were collected off dogs to start a laboratory tick colony. After one generation of colony maintenance on tick-naïve and pathogen-free New Zealand White rabbits, a rabbit used to feed F1 adults seroconverted to Anaplasma phagocytophilum antigen. PCR and subsequent DNA sequencing identified the presence of A. platys in both the adult ticks fed on this rabbit and their resulting F2 progenies. Retrospective testing of all previous (P and F1) life stages of this colony demonstrated that the infection originated from one field-collected A. platys-infected female whose progeny was propagated in the laboratory and produced the PCR-positive F1 adults. Over the following (F2-F4) generations, the prevalence of A. platys in this colony reached 90-100 % indicating highly efficient transovarial and horizontal transmission, as well as transstadial maintenance, of this pathogen by R. sanguineus s.s.

Multiple Antigenic Peptide-Based Vaccines Targeting Ixodes ricinus Neuropeptides Induce a Specific Antibody Response but Do Not Impact Tick Infestation

Synthetic peptide vaccines were designed to target the neuropeptides innervating Ixodes ricinus salivary glands and hindgut and they were tested for their capacity to afford protective immunity against nymphs or larvae and Anaplasma phagocytophilum-infected nymph infestation, in mice and sheep, respectively. In both models, the assembly of SIFamide (SIFa) or myoinhibitory peptide (MIP) neuropeptides into multiple antigenic peptide constructs (MAPs) elicited a robust IgG antibody response following immunization. Nevertheless, no observable detrimental impact on nymphs was evidenced in mice, and, unfortunately, the number of engorged nymphs on sheep was insufficient for firm conclusions to be drawn, including for bacterial transmission. Regarding larvae, while vaccination of the sheep did not globally diminish tick feeding success or development, analyses of animals at the individual level revealed a negative correlation between anti-SIFa and MIP antibody levels and larva-to-nymph molting success for both antigens. Our results provide a proof of principle and precedent for the use of MAPs for the induction of immunity against tick peptide molecules. Although the present study did not provide the expected level of protection, it inaugurates a new strategy for protection against ticks based on the immunological targeting of key components of their nervous system.

Transmission of Bartonella henselae within Rhipicephalus sanguineus: Data on the Potential Vector Role of the Tick

Bartonella henselae is a fastidious intraerythrocytic, gram-negative bacteria that causes cat scratch disease in humans. Ixodes ricinus has been confirmed to be a competent vector of B. henselae, and some indirect evidences from clinical cases and epidemiological studies also suggested that some other tick species, including Rhipicephalus sanguineus, may transmit the bacteria. B. henselae has been detected in R. sanguineus but no experimental investigations have been performed to evaluate the vector competency of this tick species regarding B. henselae transmission. To this end, this work aimed to assess the transstadial transmission of B. henselae between larvae and nymphs of R. sanguineus as well as transmission by nymphs infected at the larval stage. Four hundred B. henselae negative larvae were fed with B. henselae-infected blood by using an artificial membrane feeding system. After five days of feeding, B. henselae was detected by PCR in 57.1% (8/14) of engorged larval pools, 66.7% (4/6) of semi-engorged larval pools, and 66.7% (2/3) of larval feces pools. After molting, B. henselae DNA was also detected in 10% (1/10) of nymph pools, but not in tick feces. After a pre-fed step of nymphs infected at the larval stage on non-infected blood meal, B. henselae was detected by PCR in blood sample from the feeder, but no Bartonella colonies could be obtained from culture. These findings showed that B. henselae could be transstadial transmitted from R. sanguineus larvae to nymphs, and also suggest that these nymphs may retransmitted the bacteria through the saliva during their blood meal. This is the first study that validated the artificial membrane feeding system for maintaining R. sanguineus tick colony. It shows the possibility of transstadial transmission of B. henselae from R. sanguineus larvae to nymphs.

B. henselae is gram-negative bacteria that infects red blood cells of humans and companion animals and causes cat scratch disease in humans. Ticks were considered to be potential vectors of B. henselae for a long time until it was finally experimentally demonstrated for Ixodes ricinus. Since then, no evidence on B. henselae transmission by other tick species was reported. This study was performed 1) to validate the use of artificial membrane system to feed and infect R. sanguineus ticks and 2) to determine the possibility of B. henselae transmission by R. sanguineus, a world-widely distributed ticks. Our results show that the artificial membrane feeding system can be used to maintain R. sanguineus colony in the laboratory, and that B. henselae can be acquired by R. sanguineus during a blood meal on artificial membrane feeding system and can be transmitted from larvae to nymphs that were able to inject bacterial DNA to blood during a new blood meal. However, further investigations are still needed to confirm the viability of bacteria transmitted to blood by nymphs infected at the larval stage in order to validate B. henselae transmission by R. sanguineus.

Detection of Babesia odocoilei in Ixodes scapularis Ticks Collected from Songbirds in Ontario and Quebec, Canada

Songbirds widely disperse ticks that carry a diversity of pathogens, some of which are pathogenic to humans. Among ticks commonly removed from songbirds, the blacklegged tick, Ixodes scapularis, can harbor any combination of nine zoonotic pathogens, including Babesia species. From May through September 2019, a total 157 ticks were collected from 93 songbirds of 29 species in the Canadian provinces of Ontario and Québec. PCR testing for the 18S gene of Babesia species detected Babesia odocoilei in 12.63% of I. scapularis nymphs parasitizing songbirds in Ontario and Québec; none of the relatively small numbers of Ixodes muris, Ixodes brunneus, or Haemaphysalis leporispalustris were PCR-positive. For ticks at each site, the prevalence of B. odocoilei was 16.67% in Ontario and 8.89% and 5.26% in Québec. Of 31 live, engorged I. scapularis larvae and nymphs held to molt, 25 ticks completed the molt; five of these molted ticks were positive for B. odocoilei. PCR-positive ticks were collected from six bird species—namely, Common Yellowthroat, Swainson’s Thrush, Veery, House Wren, Baltimore Oriole, and American Robin. Phylogenetic analysis documented the close relationship of B. odocoilei to Babesia canis canis and Babesia divergens, the latter a known pathogen to humans. For the first time in Canada, we confirm the transstadial passage of B. odocoilei in I. scapularis molting from larvae to nymphs. A novel host record reveals I. scapularis on a Palm Warbler. Our findings show that B. odocoilei is present in all mobile life stages of I. scapularis, and it is widely dispersed by songbirds in Ontario and Québec.

The red fox (Vulpes vulpes), a possible reservoir of Babesia vulpes, B. canis and Hepatozoon canis and its association with the tick Dermacentor reticulatus occurrence

The red fox (Vulpes vulpes) is known to be a reservoir host of various vector-borne protozoan parasites. Yet, the impact of these parasitic infections on the health status of the red fox is unknown. In this study, we compared the prevalence of haemoprotozoa in juvenile and adult foxes from four regions in Poland. The abundance of questing adult Dermacentor reticulatus ticks was shown to differ between regions and include a tick-endemic and non-endemic region, as well as two zones in which D. reticulatus recently expanded: an eastern and a western zone. Spleen and kidney enlargement indices were compared between infected, co-infected and non-infected foxes to evaluate pathogenic output of parasitic infections. Blood samples were collected from 383 necropsied red foxes and 25 live-trapped red fox cubs. The weights of spleens, kidneys and bodies were recorded for each necropsied individual. Blood and spleen DNA samples were screened by PCR to detect 18S rRNA and cox1 gene fragments of Babesia spp., and 18S rRNA of Hepatozoon spp. Prevalence of infection and mean organ weight indices were compared in relation to fox age and sex, origin (zone) and infection status. Hepatozoon canis (174/381; 45.7%) and Babesia vulpes (117/381; 30.7%) were the dominant pathogens infecting adult foxes. Babesia canis DNA was detected in 9 (2.4%) individuals. Two fox cubs from Western Poland were infected with B. vulpes (2/14; 14%), while H. canis infection (16/25; 59%) was detected in cubs from all three regions where trapping was carried out. Infection with B. vulpes was associated with significantly higher weights of spleens and kidneys. Spleen weight/ body weight and mean kidney weight/ body weight indices were shown as relevant in evaluating changes occurring during infection with B. vulpes. Babesia and Hepatozoon spp. infections differed in red foxes from D. reticulatus-endemic, non-endemic and newly inhabited areas. The prevalence of B. canis in foxes from four regions of Poland reflects the prevalence recorded in questing adult D. reticulatus collected in these areas. This finding suggests a contribution of red foxes to the establishment of new foci of B. canis-infected D. reticulatus ticks in areas recently invaded by this tick species. Spleen and kidney enlargement was identified in foxes infected with B. vulpes, particularly in individuals co-infected with B. vulpes and H. canis.

Failed Disruption of Tick Feeding, Viability, and Molting after Immunization of Mice and Sheep with Recombinant Ixodes ricinus Salivary Proteins IrSPI and IrLip1

To identify potential vaccine candidates against Ixodes ricinus and tick-borne pathogen transmission, we have previously sequenced the salivary gland transcriptomes of female ticks infected or not with Bartonella henselae. The hypothesized potential of both IrSPI (I. ricinus serine protease inhibitor) and IrLip1 (I. ricinus lipocalin 1) as protective antigens decreasing tick feeding and/or the transmission of tick-borne pathogens was based on their presumed involvement in dampening the host immune response to tick feeding. Vaccine endpoints included tick larval and nymphal mortality, feeding, and molting in mice and sheep. Whether the antigens were administered individually or in combination, the vaccination of mice or sheep elicited a potent antigen-specific antibody response. However, and contrary to our expectations, vaccination failed to afford protection against the infestation of mice and sheep by I. ricinus nymphs and larvae, respectively. Rather, vaccination with IrSPI and IrLip1 appeared to enhance tick engorgement and molting and decrease tick mortality. To the best of our knowledge, these observations represent the first report of induction of vaccine-mediated enhancement in relation to anti-tick vaccination.

Clinical/serological outcome in humans bitten by Babesia species positive Ixodes ricinus ticks in Sweden and on the Åland Islands

The risk of contracting babesiosis after a tick bite in Sweden and on the Åland Islands, Finland, is unknown. We investigated clinical and serological outcomes in people bitten by Ixodes ricinus ticks positive for Babesia species. Ticks, blood and questionnaires were obtained from study participants in Sweden and on the Åland Islands. Sixty-five of 2098 (3.1 %) ticks were positive by real-time PCR. Three Babesia species were detected, Babesia microti (n = 33), B. venatorum (n = 27) and B. capreoli (n = 5), the latter species not known to cause human infection. Half (46 %) of the Babesia PCR-positive ticks also contained Borrelia spp. Fifty-three participants bitten by a Babesia PCR-positive tick and a control group bitten by a Babesia PCR-negative tick were tested for B. microti IgG antibodies by IFA. The overall seroprevalence was 4.4 %, but there was no significant difference between the groups. None of the participants seroconverted and no participant with a Babesia PCR-positive tick sought medical care or reported symptoms suggestive of babesiosis. Given the prevalence of Babesia in I. ricinus ticks in southern Sweden and on the Åland Islands, babesiosis should be considered a possible diagnosis in symptomatic residents who seek medical care following tick exposure.

Upscaling the Surveillance of Tick-borne Pathogens in the French Caribbean Islands

Despite the high burden of vector-borne disease in (sub)tropical areas, few information are available regarding the diversity of tick and tick-borne pathogens circulating in the Caribbean. Management and control of vector-borne disease require actual epidemiological data to better assess and anticipate the risk of (re)emergence of tick-borne diseases in the region. To simplify and reduce the costs of such large-scale surveys, we implemented a high-throughput microfluidic real-time PCR system suitable for the screening of the main bacterial and parasitic genera involved in tick-borne disease and potentially circulating in the area. We used the new screening tool to perform an exploratory epidemiological study on 132 adult specimens of Amblyomma variegatum and 446 of Rhipicephalus microplus collected in Guadeloupe and Martinique. Not only the system was able to detect the main pathogens of the area-Ehrlichia ruminantium, Rickettsia africae, Anaplasma marginale, Babesia bigemina and Babesia bovis-but the system also provided evidence of unsuspected microorganisms in Caribbean ticks, belonging to the Anaplasma, Ehrlichia, Borrelia and Leishmania genera. Our study demonstrated how high-throughput microfluidic real-time PCR technology can assist large-scale epidemiological studies, providing a rapid overview of tick-borne pathogen and microorganism diversity, and opening up new research perspectives for the epidemiology of tick-borne pathogens.

Experimental Ixodes ricinus-Sheep Cycle of Anaplasma phagocytophilum NV2Os Propagated in Tick Cell Cultures

The causative agent of tick-borne fever and human granulocytic anaplasmosis, Anaplasma phagocytophilum, is transmitted by Ixodes ricinus, and is currently considered an emerging disease throughout Europe. In this study, we established a model of A. phagocytophilum sheep infection and I. ricinus transmission using the European Norway variant 2 ovine strain (NV2Os) propagated in both IDE8 and ISE6 tick cells. Two sheep were inoculated with IDE8 tick cells infected with NV2Os. Both sheep developed A. phagocytophilum infection as determined by qPCR and PCR, the presence of fever 4 days post inoculation (dpi), the observation of morulae in granulocytes at 6 dpi, and the detection of A. phagocytophilum antibodies at 14 dpi. A. phagocytophilum was detected by PCR in skin, lung, small intestine, liver, spleen, uterus, bone marrow, and mesenteric lymph node from necropsies performed at 14 and 15 dpi. One sheep was infested during the acute phase of infection with I. ricinus nymphs from a pathogen-free colony. After molting, A. phagocytophilum transstadial transmission in ticks was validated with qPCR positive bacterial detection in 80% of salivary glands and 90% of midguts from female adults. Infected sheep blood collected at 14 dpi was demonstrated to be able to infect ISE6 tick cells, thus enabling the infection of two additional naive sheep, which then went on to develop similar clinical signs to the sheep infected previously. One of the sheep remained persistently infected until 115 dpi when it was euthanized, and transmitted bacteria to 70 and 2.7% of nymphs engorged as larvae during the acute and persistent infection stages, respectively. We then demonstrated that these infected nymphs were able to transmit the bacteria to one of two other naive infested sheep. As expected, when I. ricinus females were engorged during the acute phase of infection, no A. phagocytophilum transovarial transmission was detected. The development of this new experimental model will facilitate future research on this tick-borne bacterium of increasing importance, and enable the evaluation of any new tick/transmission control strategies.

A three-years assessment of Ixodes ricinus-borne pathogens in a French peri-urban forest

BACKGROUND

Ixodes ricinus is the predominant tick species in Europe and the primary pathogen vector for both humans and animals. These ticks are frequently involved in the transmission of Borrelia burgdorferi (sensu lato), the causative agents of Lyme borreliosis. While much more is known about I. ricinus tick-borne pathogen composition, information about temporal tick-borne pathogen patterns remain scarce. These data are crucial for predicting seasonal/annual patterns which could improve understanding and prevent tick-borne diseases.

METHODS

We examined tick-borne pathogen (TBP) dynamics in I. ricinus collected monthly in a peri-urban forest over three consecutive years. In total, 998 nymphs were screened for 31 pathogenic species using high-throughput microfluidic real-time PCR.

RESULTS

We detected DNA from Anaplasma phagocytophilum (5.3%), Rickettsia helvetica (4.5%), Borrelia burgdorferi (s.l.) (3.7%), Borrelia miyamotoi (1.2%), Babesia venatorum (1.5%) and Rickettsia felis (0.1%). Among all analysed ticks, 15.9% were infected by at least one of these microorganisms, and 1.3% were co-infected. Co-infections with B. afzeli/B. garinii and B. garinii/B. spielmanii were significantly over-represented. Moreover, significant variations in seasonal and/or inter-annual prevalence were observed for several pathogens (R. helvetica, B. burgdorferi (s.l.), B. miyamotoi and A. phagocytophilum).

CONCLUSIONS

Analysing TBP prevalence in monthly sampled tick over three years allowed us to assess seasonal and inter-annual fluctuations of the prevalence of TBPs known to circulate in the sampled area, but also to detect less common species. All these data emphasize that sporadic tick samplings are not sufficient to determine TBP prevalence and that regular monitoring is necessary.

The Immunomodulatory Effect of IrSPI, a Tick Salivary Gland Serine Protease Inhibitor Involved in Ixodes ricinus Tick Feeding

Ticks are the most important vectors of pathogens affecting both domestic and wild animals worldwide. Hard tick feeding is a slow process—taking up to several days—and necessitates extended control over the host response. The success of the feeding process depends upon injection of tick saliva, which not only controls host hemostasis and wound healing, but also subverts the host immune response to avoid tick rejection that creates a favorable niche for the survival and propagation of diverse tick-borne pathogens. Here, we report on the molecular and biochemical features and functions of an Ixodes ricinus serine protease inhibitor (IrSPI). We characterize IrSPI as a Kunitz elastase inhibitor that is overexpressed in several tick organs—especially salivary glands—during blood-feeding. We also demonstrated that when IrSPI is injected into the host through saliva, it had no impact on tissue factor pathway-induced coagulation, fibrinolysis, endothelial cell angiogenesis or apoptosis, but the protein exhibits immunomodulatory activity. In particular, IrSPI represses proliferation of CD4⁺ T lymphocytes and proinflammatory cytokine secretion from both splenocytes and macrophages. Our study contributes valuable knowledge to tick-host interactions and provides insights that could be further exploited to design anti-tick vaccines targeting this immunomodulator implicated in I. ricinus feeding.

Epidemiological Survey of Babesia divergens Asia Lineage in Wild Sika Deer (Cervus nippon) by Using Direct PCR in Japan

Babesia divergens is the major causal agent of zoonotic human babesiosis across Europe. Previously, we reported the detection of a B. divergens Asia lineage in wild sika deer (Cervus nippon) in Japan which was genetically closely related to the European B. divergens. To further elucidate its etiology, we conducted a large epidemiological survey by combining lineage-specific PCR system and blood direct PCR. The infection rate of the Asia lineage was 6.6% (116/1,747) throughout Japan, where Hokkaido (45%), Nagano (17%), Iwate (12%), Gunma (11%), and Yamanashi (11%) were highly enzootic (> 10%) among the 30 prefectures examined. European B. divergens was not detected. A geographical information system (GIS) map revealed dense populations of PCR-positive deer in the mountains including the Japanese Alps in eastern Honshu, and Hokkaido. These areas markedly overlapped with the major habitats of Ixodes persulcatus, a principal tick vector responsible for the transmission of the Asia lineage. Other areas in southern Japan including Miyazaki, Kagoshima, and Shimane Prefectures, where positive sika deer were sporadically detected, may be habitats for other tick species involved in the enzootic cycle as I. persulcatus were scarce. The rise in human babesiosis cases is occasionally attributed to healthy blood donors who were unaware of tick bites and Babesia infection. Therefore, there is an urgent need to investigate whether infections in humans have occurred in Japan.

Diagnostic Tools for the Identification of Babesia sp. in Persistently Infected Cattle

Bovine babesiosis is a tick-borne disease of cattle caused by the protozoan parasites of the genus Babesia. Babesia bovis, Babesia bigemina and Babesia divergens are considered by International health authorities (OIE) as the principal species of Babesia that cause bovine babesiosis. Animals that recover from a babesial primo infection may remain as persistent carriers with no clinical signs of disease and can be the source of infection for ticks that are able to acquire Babesia parasites from infected cattle and to transmit Babesia parasites to susceptible cattle. Several procedures that have been developed for parasite detection and diagnosis of this infectious carrier state constitute the basis for this review: A brief description of the direct microscopic detection of Babesia-infected erytrocytes; PCR-based diagnostic assays, which are very sensitive particularly in detecting Babesia in carrier cattle; in-vitro culture methods, used to demonstrate presence of carrier infections of Babesia sp.; animal inoculation, particularly for B. divergens isolation are discussed. Alternatively, persistently infected animals can be tested for specific antibabesial antibodies by using indirect serological assays. Serological procedures are not necessarily consistent in identifying persistently infected animals and have the disadvantage of presenting with cross reactions between antibodies to Babesia sp.

The role of juvenile Dermacentor reticulatus ticks as vectors of microorganisms and the problem of 'meal contamination'

Juvenile Dermacentor reticulatus ticks inhabit nests and burrows of their rodent hosts and cannot be collected from vegetation. To detect vertical transmission of Babesia canis in D. reticulatus, we studied larvae and nymphs collected from rodents. However, the molecular techniques used for detection of pathogen DNA are sensitive enough to detect not only pathogens vectored by ticks but also those taken up with current or previous blood meals ('meal contamination') or just present in the environment and on the tick or host surface ('environmental contaminations'). Thus, an additional aim of our study was to evaluate the extent of such contamination while studying feeding ticks collected from rodents. Juvenile D. reticulatus were collected from 140 rodents: 91 bank voles trapped in two forest sites in the Mazury Lake District and 49 rodents (Apodemus and Microtus spp.) from an open habitat near the town of Białobrzegi in Central Poland. Altogether 504 D. reticulatus ticks, comprising 266 individually evaluated nymphs and 238 larvae assigned to 50 larval pools, were studied for the presence of Babesia, Bartonella and Rickettsia spp. DNA. Statistical analyses were conducted to (1) evaluate the effect of rodent host factors (species, sex and age) on prevalence of infection in ticks, and (2) to compare the frequency of positive samples between groups of pathogen-positive and pathogen-negative rodent hosts. To complete the last aim, blood samples obtained from 49 rodents from Białobrzegi were studied for the presence of Babesia and Bartonella DNA. Infestation of rodent hosts with juvenile ticks ranged between 46 and 78%, with a mean abundance of 3.6 ticks/rodent for D. reticulatus and 4.8 ticks/rodent for Ixodes ricinus. The highest prevalence of PCR-positive D. reticulatus samples was obtained for Rickettsia spp. (28%) and R. raoultii was identified in 22 sequenced PCR products. Babesia DNA was detected in 20 (7.5%), including B. microti in 18 (6.8%) and B. canis in two (0.8%) of 266 D. reticulatus nymphs that were analyzed. Babesia microti DNA was also detected in four pools of D. reticulatus larvae (4/50 pools = 8%). The detection success of B. microti in D. reticulatus was associated with the species of the rodent hosts of the ticks (much higher for typical B. microti-host-species such as Microtus spp. than for Apodemus spp.) and host age (3 × higher in ticks collected from adult hosts in comparison to juvenile ones). Moreover, the DNA of B. microti was detected in 68% of D. reticulatus nymphs collected from B. microti-positive rodents in comparison to only 1.6% of nymphs collected from B. microti-negative rodents. Bartonella DNA was detected in 18% of D. reticulatus tick samples (38% of larval pools, 14% of nymphs). Again, host factors played important roles for 'tick positivity'-the highest prevalence of positive ticks was on Apodemus spp., which are regarded as Bartonella reservoirs. Bartonella DNA was detected in 42% of nymphs and 57% of larval pools collected from Bartonella-positive rodents in comparison to 28% of nymphs and 11% of larvae collected from Bartonella-negative rodents. Vertical transmission of B. canis in D. reticulatus ticks was confirmed in the field. Additionally, we demonstrated that 'meal contamination' generates a confounding signal in molecular detection of pathogen DNA extracted from ticks collected from infected hosts and must be taken into account in evaluating the competence of tick species as vectors.