Role of mustelids in the life-cycle of ixodid ticks and transmission cycles of four tick-borne pathogens

Circulation of Anaplasma phagocytophilum among invasive and native carnivore species living in sympatry in Poland

BACKGROUND

Anaplasma phagocytophilum is characterized by a worldwide distribution and distinguished from other Anaplasmataceae by the broadest range of mammalian hosts and high genetic diversity. The role carnivores play in the life cycle of A. phagocytophilum in Europe is uncertain. Currently, only the red fox is considered a suitable reservoir host. In this study, we focused on native and invasive medium-sized carnivore species that live in sympatry and represent the most abundant species of wild carnivores in Poland.

METHODS

A total of 275 individual spleen samples from six carnivore species (Vulpes vulpes, Meles meles, Procyon lotor, Nyctereutes procyonoides and Martes spp.) were screened combining nested PCR and sequencing for A. phagocytophilum targeting a partial groEL gene with subsequent phylogenetic analysis inferred by the maximum likelihood method.

RESULTS

The DNA of A. phagocytophilum was detected in 16 of 275 individuals (5.8%). Eight unique genetic variants of A. phagocytophilum were obtained. All detected haplotypes clustered in the clade representing European ecotype I. Three variants belonged to the subclade with European human cases together with strains from dogs, foxes, cats, and wild boars.

CONCLUSIONS

While carnivores might have a restricted role in the dissemination of A. phagocytophilum due to their relatively low to moderate infection rates, they hold significance as hosts for ticks. Consequently, they could contribute to the transmission of tick-borne infections to humans indirectly, primarily through tick infection. This underscores the potential risk of urbanization for the A. phagocytophilum life cycle, further emphasizing the need for comprehensive understanding of its ecological dynamics.

Role of invasive carnivores (Procyon lotor and Nyctereutes procyonoides) in epidemiology of vector-borne pathogens: molecular survey from the Czech Republic

BACKGROUND

Vector-borne pathogens (VBPs) are a major threat to humans, livestock and companion animals worldwide. The combined effect of climatic, socioeconomic and host composition changes favours the spread of the vectors, together with the expansion of invasive carnivores contributing to the spread of the pathogens. In Europe, the most widespread invasive species of carnivores are raccoons (Procyon lotor) and raccoon dogs (Nyctereutes procyonoides). This study focused on the detection of four major groups of VBPs namely Babesia, Hepatozoon, Anaplasma phagocytophilum and Bartonella in invasive and native carnivores in the Czech Republic, with the emphasis on the role of invasive carnivores in the eco-epidemiology of said VBPs.

METHODS

Spleen samples of 84 carnivores of eight species (Canis aureus, Canis lupus, Lynx lynx, P. lotor, Martes foina, Lutra lutra, Mustela erminea and N. procyonoides) were screened by combined nested PCR and sequencing for the above-mentioned VBPs targeting 18S rRNA and cytB in hemoprotozoa, groEL in A. phagocytophilum, and using multilocus genotyping in Bartonella spp. The species determination is supported by phylogenetic analysis inferred by the maximum likelihood method.

RESULTS

Out of 84 samples, 44% tested positive for at least one pathogen. Five different species of VBPs were detected in P. lotor, namely Bartonella canis, Hepatozoon canis, Hepatozoon martis, A. phagocytophilum and Bartonella sp. related to Bartonella washoensis. All C. lupus tested positive for H. canis and one for B. canis. Three VBPs (Hepatozoon silvestris, A. phagocytophilum and Bartonella taylorii) were detected in L. lynx for the first time. Babesia vulpes and yet undescribed species of Babesia, not previously detected in Europe, were found in N. procyonoides.

CONCLUSIONS

Wild carnivores in the Czech Republic are hosts of several VBPs with potential veterinary and public health risks. Among the studied carnivore species, the invasive raccoon is the most competent host. Raccoons are the only species in our study where all the major groups of studied pathogens were detected. None of the detected pathogen species were previously detected in these carnivores in North America, suggesting that raccoons adapted to local VBPs rather than introduced new ones. Babesia vulpes and one new, probably imported species of Babesia, were found in raccoon dogs.

Borrelia miyamotoi: A Comprehensive Review

Borrelia miyamotoi is an emerging tick-borne pathogen in the Northern Hemisphere and is the causative agent of Borrelia miyamotoi disease (BMD). Borrelia miyamotoi is vectored by the same hard-bodied ticks as Lyme disease Borrelia, yet phylogenetically groups with relapsing fever Borrelia, and thus, has been uniquely labeled a hard tick-borne relapsing fever Borrelia. Burgeoning research has uncovered new aspects of B. miyamotoi in human patients, nature, and the lab. Of particular interest are novel findings on disease pathology, prevalence, diagnostic methods, ecological maintenance, transmission, and genetic characteristics. Herein, we review recent literature on B. miyamotoi, discuss how findings adapt to current Borrelia doctrines, and briefly consider what remains unknown about B. miyamotoi.

Zoonotic ecotype-I of Anaplasma phagocytophilum in sympatric wildcat, pine marten and red squirrel - Short communication

Anaplasma phagocytophilum is the causative agent of granulocytic anaplasmosis in humans, dogs, cats, horses and tick-borne fever in ruminants. In Europe, its main vector is the tick species Ixodes ricinus. In this study, spleen and liver samples, as well as ticks from 18 wild-living mammals (belonging to seven species) were analysed for the presence of A. phagocytophilum with molecular methods. The zoonotic ecotype-I of A. phagocytophilum was identified in a European wildcat (Felis silvestris) and its tick, a European pine marten (Martes martes) and a Eurasian red squirrel (Sciurus vulgaris). All PCR-positive samples were collected in 2019 and originated in the same geographic area. These results indicate that taxonomically diverse mammalian species can maintain the local enzootic cycle of the same genotype of A. phagocytophilum. To the best of our knowledge, this is the first report of the zoonotic variant of A. phagocytophilum in the wildcat and in the European pine marten in a broad geographical context, as well as in the red squirrel in Hungary. Since all these host species are well known for their urban and peri-urban presence, the results of this study verify their role in the synanthropic enzootic cycle of granulocytic anaplasmosis and tick-borne fever.

Is composition of vertebrates an indicator of the prevalence of tick-borne pathogens?

Communities of vertebrates tend to appear together under similar ranges of environmental features. This study explores whether an explicit combination of vertebrates and their contact rates with a tick vector might constitute an indicator of the prevalence of a pathogen in the quest for ticks at the western Palearctic scale. We asked how ‘indicator’ communities could be ‘markers’ of the actual infection rates of the tick in the field of two species of Borrelia (a bacterium transmitted by the tick Ixodes ricinus). We approached an unsupervised classification of the territory to obtain clusters on the grounds of abundance of each vertebrate and contact rates with the tick. Statistical models based on Neural Networks, Random Forest, Gradient Boosting, and AdaBoost were detect the best correlation between communities’ composition and the prevalence of Borrelia afzelii and Borrelia gariniii in questing ticks. Both Gradient Boosting and AdaBoost produced the best results, predicting tick infection rates from the indicator communities. A ranking algorithm demonstrated that the prevalence of these bacteria in the tick is correlated with indicator communities of vertebrates on sites selected as a proof-of-concept. We acknowledge that our findings are supported by statistical outcomes, but they provide consistency for a framework that should be deeper explored at the large scale.

Trypanosoma (Megatrypanum) pestanai in Eurasian badgers (Meles meles) and Ixodidae ticks, Italy

Trypanosomes are haemoflagellate protozoa transmitted by blood-feeding arthropods causing infections in a wide range of mammals, including humans. Adult badgers (Meles meles, n = 2), displaying severe paralysis, ataxia and severe ectoparasite infestation, were rescued from a peri-urban area of Bari (southern Italy). Blood samples and ectoparasites were screened for Trypanosoma spp. by the combined PCR/sequencing approach, targeting a fragment of 18S rRNA gene. Smears of haemolymph, guts and salivary glands of the alive ticks were microscopically observed. No haematological alterations, except thrombocytopenia, were found. Trypomastigotes and epimastigotes were observed in the blood smears of both badgers and Trypanosoma pestanai was molecularly identified. Out of 33 ticks (i.e. n = 31 Ixodes canisuga, n = 2 Ixodes ricinus) and two fleas (Ctenocephalides felis), 11 specimens (n = 5 I. canisuga engorged nymphs, n = 4 engorged females and n = 2 I. ricinus engorged females) tested positive only for T. pestanai DNA. All smears from ticks were negative. The present study firstly revealed T. pestanai in Ixodidae and badgers from Italy, demonstrating the occurrence of the protozoan on the peninsula. Further studies are needed to clarify the occurrence of the only known vector of this parasite, Paraceras melis flea, as well as other putative arthropods involved in the transmission of T. pestanai.

Understanding potential implications for non-trophic parasite transmission based on vertebrate behavior at mesocarnivore carcass sites

High infection risk is often associated with aggregations of animals around attractive resources. Here, we explore the behavior of potential hosts of non-trophically transmitted parasites at mesocarnivore carcass sites. We used videos recorded by camera traps at 56 red fox (Vulpes vulpes) carcasses and 10 carcasses of other wild carnivore species in three areas of southeastern Spain. Scavenging species, especially wild canids, mustelids and viverrids, showed more frequent rubbing behavior at carcass sites than non-scavenging and domestic species, suggesting that they could be exposed to a higher potential infection risk. The red fox was the species that most frequently contacted carcasses and marked and rubbed carcass sites. Foxes contacted heterospecific carcasses more frequently and earlier than conspecific ones and, when close contact occurred, it was more likely to be observed at heterospecific carcasses. This suggests that foxes avoid contact with the type of carcass and time period that have the greatest risk as a source of parasites. Overall, non-trophic behaviors of higher infection risk were mainly associated with visitor-carcass contact and visitor contact with feces and urine, rather than direct contact between visitors. Moreover, contact events between scavengers and carnivore carcasses were far more frequent than consumption events, which suggests that scavenger behavior is more constrained by the risk of acquiring meat-borne parasites than non-trophically transmitted parasites. This study contributes to filling key gaps in understanding the role of carrion in the landscape of disgust, which may be especially relevant in the current global context of emerging and re-emerging pathogens.

Life Cycle and Genetic Identification of Argas persicus Infesting Domestic Fowl in Khyber Pakhtunkhwa, Pakistan

Ticks transmit numerous pathogens to animals including humans; therefore, they are parasites of health concern. Soft ticks infesting domestic fowl in Pakistan are carriers of viruses and bacteria and cause unestimated economic losses in the poultry sector. The current study was intended to identify soft ticks infesting domestic fowl and understand their spatiotemporal distribution along 1 year. A sum of 7,219 soft ticks were collected from 608 domestic fowl in 58 infested shelters; 938 (12.9%) ticks were found on the host and 6,281 (87%) in the shelters. The collected ticks comprised 3,503 (48.52%) adults including 1,547 (21.42%) males and 1,956 (27.09%) females, 3,238 (44.85%) nymphs, and 478 (6.62%) larvae. The most prevalent life stages were adults, followed by nymphs and larvae. Overall tick prevalence considering all visited shelters was 38.66% (58/150). The highest tick prevalence was found in district Lakki Marwat (50.03%) followed by Peshawar (31.08%) and Chitral (18.88%) districts. All ticks were morpho-taxonomically identified as Argas persicus. To determine their life cycle, adult A. persicus were reared in the laboratory infesting domestic fowl (Gallus gallus domesticus). The life cycle was completed in 113–132 days (egg to egg) with a mean temperature of 33 ± 3°C and relative humidity of 65 ± 5%. Individual ticks were used for DNA extraction and subjected to polymerase chain reaction (PCR) using specific primers for the amplification of a partial fragment of mitochondrial cytochrome oxidase subunit I (cox1) and 16S ribosomal RNA (16S rRNA) genes. Obtained amplicons were compared using basic local alignment search tool (BLAST) to scan for homologous sequences. Phylogenetic trees showed A. persicus from Pakistan clustering with conspecific sequences reported from Australia, Chile, China, Kenya, and the United States. This is the first study aiming to reproduce the life cycle of A. persicus and genetically identify this tick in the region. Further studies are encouraged to investigate the pathogens associated with this soft tick species in Pakistan.

Tick infestation on medium-large-sized mammalian hosts: are all equally suitable to Ixodes ricinus adults?

Background

In Europe, the generalist tick, Ixodes ricinus, is the main vector of several tick-borne pathogens causing diseases in humans and livestock. Understanding how different species of hosts limit the tick population is crucial for management. In general, larger ectoparasites are expected to select hosts with larger body size. Consistent with this, larval and nymphal I. ricinus can feed on a wide range of different-sized vertebrates, while the adult female stage is expected to rely on a medium–large-sized host for reproduction. However, we still have a limited understanding of whether medium-sized hosts other than roe deer can serve as hosts to adult ticks, and other factors than size may also affect host selection.

Methods

To increase our understanding of the suitability of the different species of medium-sized hosts for adult ticks, we sampled mainly roadkill mammals from within the questing season of ticks. We counted life stages of ticks on roe deer (Capreolus capreolus) (n = 29), red fox (Vulpes vulpes) (n = 6), badger (Meles meles) (n = 14) and red squirrel (Sciurus vulgaris) (n = 17) from spatially overlapping populations in Norway, and analysed variation between species across different body parts with a mixed-effects negative binomial model (with and without zero-inflation).

Results

Red squirrel hosted a high density of larval and nymphal I. ricinus, but only one individual had adult female ticks. Roe deer hosted by far the largest number of adult ticks. Badgers had very few ticks, possibly due to their thick skin. Red foxes had intermediate numbers, but a high proportion of subcutaneous, dead ticks (69.3%), suggesting they are not very suitable hosts. Body mass predicted the presence of adult I. ricinus ticks. However, species was a better predictor than body mass for number of ticks, suggesting there was species variation in host suitability beyond body mass per se.

Conclusions

Our study provides evidence that roe deer are indeed the main suitable reproduction host to adult I. ricinus ticks, and are likely a key to host limitation of the tick population in this northern ecosystem.

Graphic abstract

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.

What do we still need to know about Ixodes ricinus?

In spite of many decades of intensive research on Ixodes ricinus, the castor bean tick of Europe, several important aspects of its basic biology remain elusive, such as the factors determining seasonal development, tick abundance and host specificity, and the importance of water management. Additionally, there are more recent questions about the geographical diversity of tick genotypes and phenotypes, the role of migratory birds in the ecoepidemiology of I. ricinus, the importance of protective immune responses against I. ricinus, particularly in the context of vaccination, and the role of the microbiome in pathogen transmission. Without more detailed knowledge of these issues, it is difficult to assess the likely effects of changes in climate and biodiversity on tick distribution and activity, to predict potential risks arising from new and established tick populations and I. ricinus-borne pathogens, and to improve prevention and control measures. This review aims to discuss the most important outstanding questions against the backdrop of the current state of knowledge of this important tick species.

Molecular Survey on Vector-Borne Pathogens in Alpine Wild Carnivorans

In Europe, free-ranging wildlife has been linked to the emergence of several vector-borne diseases such as rodents for Borrelia burgdorferi s.l. In particular, wild carnivorans are one of the most important sources of emerging zoonotic pathogens worldwide, although little information is available regarding the epidemiology of vector-borne parasites in these animals. Thus, the aim of this paper was to investigate the prevalence of Babesia spp., Anaplasma spp., Ehrlichia spp., Hepatozoon spp. and Leishmania infantum in alpine wild canids and mustelids from Italy. For this study, spleen samples of 157 foxes (Vulpes vulpes), 45 badgers (Meles meles), and 33 wolves (Canis lupus) collected between 2009 and 2017 in Northwest Italy were examined by using conventional PCR. Logistic regression was used to identify possible risk factors for pathogen infections. DNA of any of the tested pathogens was found in more than 90% of the analyzed animals. In particular, Babesia spp. showed significantly higher prevalence in foxes (89.7%) and badgers (89.6%) than in wolves, while the latter were considerably more infected with Hepatozoon canis (75.8%) than foxes (5.1%). None of the badger tested positive for Hepatozoon spp., although they showed high prevalence of Leishmania infantum (53.3%). Sequencing results revealed the presence, among others, of Babesia vulpes, Babesia sp. isolate badger type A and B, and Anaplasma phagocytophilum. Moreover, previously unreported pathogen/host associations were observed, such as Babesia capreoli in wolves and badgers. The prevalence of vector-borne pathogens observed in the present study is one of the highest reported so far, suggesting the importance of free-ranging carnivorans in the epidemiology and maintenance of the sylvatic cycle of the pathogens. Moreover, several of these pathogens are of particular importance regarding human (A. phagocytophilum, L. infantum) and pet health (L. infantum, B. vulpes).

Molecular detection of Anaplasma phagocytophilum in wild carnivores in north-eastern Poland

Background

Anaplasma phagocytophilum is an obligate parasitic intracellular bacterium. It is the causative agent of granulocytic anaplasmosis, with effects on human and animal health. In Europe, the pathogen is mainly transmitted among a wide range of vertebrate hosts by blood-sucking arthropods. The aim of this study was to determine the presence of A. phagocytophilum in wild carnivores, viz raccoon dogs (Nyctereutes procyonoides), badgers (Meles meles), foxes (Vulpes vulpes), martens (Martes sp.) and European polecats (Mustela putorius), using molecular methods.

Methods

In the present study, 174 spleen samples were collected from adult, wild carnivores hunted in the years 2013–2016. A short fragment (383 bp) of the 16S ribosomal RNA gene partial sequence was used as a marker to identify A. phagocytophilum in spleen samples collected from carnivores using nested PCR.

Results

The prevalence of A. phagocytophilum in wild carnivores was 31.61% (55/174). Seven sequences of A. phagocytophilum were generated from two raccoon dogs, two badgers, one marten, one red fox and one European polecat. Six identical nucleotide sequences were obtained from one raccoon dog, two badgers, one marten, one red fox and one European polecat (A. phagocytophilum sequences 1: MH328205–MH328209, MH328211), and these were identical to many A. phagocytophilum sequences in the GenBank database (100% similarity). The second sequence (A. phagocytophilum sequence 2: MH328210) obtained from the raccoon dog shared 99.74% identity with A. phagocytophilum sequence 1.

Conclusions

To our knowledge, this is the first study to use molecular methods to determine the presence of A. phagocytophilum in wild carnivores, viz raccoon dog, badger, marten and European polecat, in Poland. The detected A. phagocytophilum sequences (1 and 2) were closely related with those of A. phagocytophilum occurring in a wide range of wild and domestic animals and vectors.

Anaplasma phagocytophilum evolves in geographical and biotic niches of vertebrates and ticks

Background

Anaplasma phagocytophilum is currently regarded as a single species. However, molecular studies indicate that it can be subdivided into ecotypes, each with distinct but overlapping transmission cycle. Here, we evaluate the interactions between and within clusters of haplotypes of the bacterium isolated from vertebrates and ticks, using phylogenetic and network-based methods.

Methods

The presence of A. phagocytophilum DNA was determined in ticks and vertebrate tissue samples. A fragment of the groEl gene was amplified and sequenced from qPCR-positive lysates. Additional groEl sequences from ticks and vertebrate reservoirs were obtained from GenBank and through literature searches, resulting in a dataset consisting of 1623 A. phagocytophilum field isolates. Phylogenetic analyses were used to infer clusters of haplotypes and to assess phylogenetic clustering of A. phagocytophilum in vertebrates or ticks. Network-based methods were used to resolve host-vector interactions and their relative importance in the segregating communities of haplotypes.

Results

Phylogenetic analyses resulted in 199 haplotypes within eight network-derived clusters, which were allocated to four ecotypes. The interactions of haplotypes between ticks, vertebrates and geographical origin, were visualized and quantified from networks. A high number of haplotypes were recorded in the tick Ixodes ricinus. Communities of A. phagocytophilum recorded from Korea, Japan, Far Eastern Russia, as well as those associated with rodents had no links with the larger set of isolates associated with I. ricinus, suggesting different evolutionary pressures. Rodents appeared to have a range of haplotypes associated with either Ixodes trianguliceps or Ixodes persulcatus and Ixodes pavlovskyi. Haplotypes found in rodents in Russia had low similarities with those recorded in rodents in other regions and shaped separate communities.

Conclusions

The groEl gene fragment of A. phagocytophilum provides information about spatial segregation and associations of haplotypes to particular vector-host interactions. Further research is needed to understand the circulation of this bacterium in the gap between Europe and Asia before the overview of the speciation features of this bacterium is complete. Environmental traits may also play a role in the evolution of A. phagocytophilum in ecotypes through yet unknown relationships.

Electronic supplementary material

The online version of this article (10.1186/s13071-019-3583-8) contains supplementary material, which is available to authorized users.

Can Protected Areas Mitigate Lyme Disease Risk in Fennoscandia?

This Forum article synthesizes the current evidence on the links between predator-prey interactions, protected areas and spatial variations in Lyme disease risk in Fennoscandia. I suggest key research directions to better understand the role of protected areas in promoting the persistence of diverse predator guilds. Conserving predators could help reducing host populations and Lyme disease risk in northern Europe. There is an urgent need to find possible win-win solutions for biodiversity conservation and human health in ecosystems facing rapid global environmental change.