Molecular screening for Midichloria bacteria in hard and soft ticks (Acari: Ixodida).

Ticks can harbor complex and highly variable microbial communities. Among these microorganisms,there are important pathogens of humans and animals that can be transmitted through the blood meal.Less is known about the other members of the microbial community of Ixodida, those that do not causeovert diseases. Among these, Midichloria mitochondrii, symbiont of the tick Ixodes ricinus, is the firstdescribed member of the family Midichloriaceae, order Rickettsiales. This bacterium is present in 100%females and is vertically transmitted (Sassera, 2008). The possibility of horizontal transmission issuggested by serological and molecular analyses showing positivity of mammalian blood and sera to M.mitochondrii (Mariconti, 2012; Bazzocchi, 2013). However, its role is still unknown. Recent reports areexpanding the view of this family, now including bacteria of great biological and medical interest,indicating a widespread distribution with an increasing range of hosts, with ticks being stronglyrepresented (Epis, 2008).Here we present a molecular screening of 17 tick species (for a total of 92 individuals), detecting andquantifying bacteria closely related to M. mitochondrii in seven of them, including the first report of amidichloriacea in a soft tick species, Ornithodoros maritimus. Based on sequence identity andphylogenetic analysis we propose that these bacteria could constitute the genus Midichloria. Theperformed screening highlights different prevalence levels in different tick species including one, Ixodesaulacodi, where the bacteria is present in all examined individuals, like in I. ricinus. This result promptsus to hypothesize different roles of Midichloria bacteria in different tick species

Babesia and its hosts: adaptation to long-lasting interactions as a way to achieve efficient transmission

Babesia, the causal agent of babesiosis, are tick-borne apicomplexan protozoa. True babesiae (Babesia genus sensu stricto) are biologically characterized by direct development in erythrocytes and by transovarial transmission in the tick. A large number of true Babesia species have been described in various vertebrate and tick hosts. This review presents the genus then discusses specific adaptations of Babesia spp. to their hosts to achieve efficient transmission. The main adaptations lead to long-lasting interactions which result in the induction of two reservoirs: in the vertebrate host during low long-term parasitemia and throughout the life cycle of the tick host as a result of transovarial and transstadial transmission. The molecular bases of these adaptations in vertebrate hosts are partially known but few of the tick-host interaction mechanisms have been elucidated

Reference-free detection of isolated SNPs

International audienceDetecting Single Nucleotide Polymorphisms (SNPs) between genomes is becoming a routine task with Next Generation Sequencing. Generally, SNP detection methods use a reference genome. As non-model organisms are increasingly investigated, the need for reference-free methods has been amplified. Most of the existing reference-free methods have fundamental limitations: they can only call SNPs between exactly two datasets, and/or they require a prohibitive amount of computational resources. The method we propose, DISCOSNP, detects both heterozygous and homozygous isolated SNPs from any number of read datasets, without a reference genome, and with very low memory and time footprints (billions of reads can be analyzed with a standard desktop computer). To facilitate downstream genotyping analyses, DISCOSNP ranks predictions and outputs quality and coverage per allele. Compared to finding isolated SNPs using a state-of-the-art assembly and mapping approach, DISCOSNP requires significantly less computational resources, shows similar precision/recall values, and highly ranked predictions are less likely to be false positives. An experimental validation was conducted on an arthropod species (the tick Ixodes ricinus) on which de novo sequencing was performed. Among the predicted SNPs that were tested, 96% were successfully genotyped and truly exhibited polymorphism

Colonization of Grande Comore Island by a lineage of Rhipicephalus appendiculatus ticks

<p>Abstract</p> <p>Background</p> <p>Union of the Comoros suffered a severe East Coast Fever epidemic in 2004. <it>Rhipicephalus appendiculatus </it>was probably involved in pathogen transmission as this competent tick species, although previously absent from Comoros, was sampled on 4 animals on one geographical site during the epidemic. We carried out an entomological survey on all three islands of Union of the Comoros to establish cattle tick species distribution with a special emphasis on <it>R. appendiculatus</it>. We investigated <it>R. appendiculatus </it>intraspecific diversity as this species has been previously shown to be split off into two main cytoplasmic lineages with different ecology, physiology and vectorial competence. This survey also included sampling of live cattle imported from Tanzania to investigate the possibility of tick introduction through animal trade.</p> <p>Results</p> <p>Our data show that Comoros cattle are infested with <it>Amblyomma variegatum</it>, <it>Rhipicephalus microplus </it>and <it>R. appendiculatus</it>. This latter species has established throughout Grande Comore but is absent from Anjouan and Moheli. Interestingly, 43 out of the 47 sequenced <it>R. appendiculatus </it>ticks belong to one single highly competent lineage while ticks from the other lineage where only found on imported cattle or on cattle parked at the vicinity of the harbor. At last, 2 ticks identified as <it>R. evertsi</it>, a species so far virtually absent on Comoros, were sampled on imported cattle.</p> <p>Conclusions</p> <p>This survey shows that importation of live cattle is clearly a source of vector introduction in Comoros. The wide distribution of one highly competent <it>R. appendiculatus </it>lineage on Grande Comore, together with the absence of this species on the two neighbouring islands is in accordance with the rapid and disastrous spread of East Coast Fever epidemics on Grande Comore Island only. Whether the other <it>R. appendiculatus </it>lineage as well as <it>R. evertsi </it>species will succeed in establishing permanently on Grande Comore needs to be monitored.</p

Ixodes ricinus and Its Transmitted Pathogens in Urban and Peri-Urban Areas in Europe: New Hazards and Relevance for Public Health.

Tick-borne diseases represent major public and animal health issues worldwide. Ixodes ricinus, primarily associated with deciduous and mixed forests, is the principal vector of causative agents of viral, bacterial, and protozoan zoonotic diseases in Europe. Recently, abundant tick populations have been observed in European urban green areas, which are of public health relevance due to the exposure of humans and domesticated animals to potentially infected ticks. In urban habitats, small and medium-sized mammals, birds, companion animals (dogs and cats), and larger mammals (roe deer and wild boar) play a role in maintenance of tick populations and as reservoirs of tick-borne pathogens. Presence of ticks infected with tick-borne encephalitis virus and high prevalence of ticks infected with Borrelia burgdorferi s.l., causing Lyme borreliosis, have been reported from urbanized areas in Europe. Emerging pathogens, including bacteria of the order Rickettsiales (Anaplasma phagocytophilum, "Candidatus Neoehrlichia mikurensis," Rickettsia helvetica, and R. monacensis), Borrelia miyamotoi, and protozoans (Babesia divergens, B. venatorum, and B. microti) have also been detected in urban tick populations. Understanding the ecology of ticks and their associations with hosts in a European urbanized environment is crucial to quantify parameters necessary for risk pre-assessment and identification of public health strategies for control and prevention of tick-borne diseases

Ixodes ricinus and its transmitted pathogens in urban and peri-urban areas in Europe: new hazards and relevance for public health

Tick-borne diseases represent major public and animal health issues worldwide. Ixodes ricinus, primarily associated with deciduous and mixed forests, is the principal vector of causative agents of viral, bacterial, and protozoan zoonotic diseases in Europe. Recently, abundant tick populations have been observed in European urban green areas, which are of public health relevance due to the exposure of humans and domesticated animals to potentially infected ticks. In urban habitats, small and medium-sized mammals, birds, companion animals (dogs and cats), and larger mammals (roe deer and wild boar) play a role in maintenance of tick populations and as reservoirs of tick-borne pathogens. Presence of ticks infected with tick-borne encephalitis virus and high prevalence of ticks infected with Borrelia burgdorferi s.l., causing Lyme borreliosis, have been reported from urbanized areas in Europe. Emerging pathogens, including bacteria of the order Rickettsiales (Anaplasma phagocytophilum, “Candidatus Neoehrlichia mikurensis,” Rickettsia helvetica, and R. monacensis), Borrelia miyamotoi, and protozoans (Babesia divergens, B. venatorum, and B. microti) have also been detected in urban tick populations. Understanding the ecology of ticks and their associations with hosts in a European urbanized environment is crucial to quantify parameters necessary for risk pre-assessment and identification of public health strategies for control and prevention of tick-borne diseases

High degree of mitochondrial gene heterogeneity in the bat tick species Ixodes vespertilionis, I. ariadnae and I. simplex from Eurasia

Background: Phylogeographical studies allow precise genetic comparison of specimens, which were collected over large geographical ranges and belong to the same or closely related animal species. These methods have also been used to compare ticks of veterinary-medical importance. However, relevant data are missing in the case of ixodid ticks of bats, despite (1) the vast geographical range of both Ixodes vespertilionis and Ixodes simplex, and (2) the considerable uncertainty in their taxonomy, which is currently unresolvable by morphological clues. Methods: In the present study 21 ticks were selected from collections or were freshly removed from bats or cave walls in six European and four Asian countries. The DNA was extracted and PCRs were performed to amplify part of the cytochrome oxidase I (COI), 16S and 12S rDNA genes, followed by sequencing for identification and molecular-phylogenetic comparison. Results: No morphological differences were observed between Ixodes vespertilionis specimens from Spain and from other parts of Europe, but corresponding genotypes had only 94.6 % COI sequence identity. An I. vespertilionis specimen collected in Vietnam was different both morphologically and genetically (i.e. with only 84.1 % COI sequence identity in comparison with I. vespertilionis from Europe). Two ticks (collected in Vietnam and in Japan) formed a monophyletic clade and shared morphological features with I. ariadnae, recently described and hitherto only reported in Europe. In addition, two Asiatic specimens of I. simplex were shown to differ markedly from European genotypes of the same species. Phylogenetic relationships of ticks showed similar clustering patterns with those of their associated bat host species. Conclusions: Although all three ixodid bat tick species evaluated in the present study appear to be widespread in Eurasia, they exhibit pronounced genetic differences. Data of this study also reflect that I. vespertilionis may represent a species complex

Emerging horizons for tick-borne pathogens: from the ‘one pathogen–one disease’ vision to the pathobiome paradigm

Ticks as vectors of several notorious zoonotic pathogens, represent an important and increasing threat for human, animal health in Europe. Recent application of new technology revealed the complexity of the tick microbiome that might impact upon its vectorial capacity. Appreciation of these complex systems is expanding our vision of tick-borne pathogens leading us to evolve a more integrated view that embraces the “pathobiome” representing the pathogenic agent integrated within its abiotic and biotic environments. In this review, we will explore how this new vision will revolutionize our understanding of tick-borne diseases. We will discuss the implications in terms of research approach for the future in order to efficiently prevent and control the threat posed by ticks