Macro-parasites and micro-parasites co-exist in rodent communities but are associated with different community-level parameters.

Wildlife species are often heavily parasitized by multiple infections simultaneously. Yet research on sylvatic transmission cycles, tend to focus on host interactions with a single parasite and neglects the influence of co-infections by other pathogens and parasites. Co-infections between macro-parasites and micro-parasites can alter mechanisms that regulate pathogenesis and are important for understanding disease emergence and dynamics. Wildlife rodent hosts in the Lyme disease system are infected with macro-parasites (i.e., ticks and helminths) and micro-parasites (i.e., Borrelia spp.), however, there has not been a study that investigates the interaction of all three parasites (i.e., I. pacificus, Borrelia spp., and helminths) and how these co-infections impact prevalence of micro-parasites. We live-trapped rodents in ten sites in northern California to collect feces, blood, ear tissue, and attached ticks. These samples were used to test for infection status of Borrelia species (i.e., micro-parasite), and describe the burden of ticks and helminths (i.e., macro-parasites). We found that some rodent hosts were co-infected with all three parasites, however, the burden or presence of concurrent macro-parasites were not associated with Borrelia infections. For macro-parasites, we found that tick burdens were positively associated with rodent Shannon diversity while negatively associated with predator diversity, whereas helminth burdens were not significantly associated with any host community metric. Ticks and tick-borne pathogens are associated with rodent host diversity, predator diversity, and abiotic factors. However, it is still unknown what factors helminths are associated with on the community level. Understanding the mechanisms that influence co-infections of multiple types of parasites within and across hosts is an increasingly critical component of characterizing zoonotic disease transmission and maintenance.

Worldwide host associations of the tick genus Ixodes suggest relationships based on environmental sharing rather than on co-phylogenetic events.

BACKGROUND: This study aims to capture how ticks of the genus Ixodes gained their hosts using network constructs. We propose two alternative hypotheses, namely, an ecological background (ticks and hosts sharing environmentally available conditions) and a phylogenetic one, in which both partners co-evolved, adapting to existing environmental conditions after the association took place. METHODS: We used network constructs linking all the known pairs of associations between each species and stage of ticks with families and orders of hosts. Faith's phylogenetic diversity was used to evaluate the phylogenetic distance of the hosts of each species and changes occurring in the ontogenetic switch between consecutive stages of each species (or the extent of the changes in phylogenetic diversity of hosts for consecutive stages of the same species). RESULTS: We report highly clustered associations among Ixodes ticks and hosts, supporting the influence of the ecological adaptation and coexistence, demonstrating a lack of strict tick-host coevolution in most cases, except for a few species. Keystone hosts do not exist in the relationships between Ixodes and vertebrates because of the high redundancy of the networks, further supporting an ecological relationship between both types of partners. The ontogenetic switch of hosts is high for species with enough data, which is another potential clue supporting the ecological hypothesis. Other results suggest that the networks displaying tick-host associations are different according to the biogeographical realms. Data for the Afrotropical region reveal a lack of extensive surveys, while results for the Australasian region are suggestive of a mass extinction of vertebrates. The Palearctic network is well developed, with many links demonstrating a highly modular set of relationships. CONCLUSIONS: With the obvious exceptions of Ixodes species restricted to one or a few hosts, the results point to an ecological adaptation. Even results on species linked to groups of ticks (such as Ixodes uriae and the pelagic birds or the bat-tick species) are suggestive of a previous action of environmental forces.

Subcutaneous Ticks in Wild Carnivores: Any Host-Related Differences?

Ticks under the skin have been shown in different canid species such as red fox, domestic dog, and raccoon dog. Despite being increasingly reported in Europe in the last decade, the biological mechanisms associated to subcutaneous ticks (SCT), as well as the predisposing factors, are not yet clear. The main goal of this study was to investigate the presence of SCT in wild carnivores in Northwestern Italy. Sixty-three wild carnivores were examined, and SCT were submitted to histological examination or stored in ethanol for morphological and molecular identification. A portion of the cox1 gene and 16S rDNA were amplified, and positive PCR products were sequenced. Fifty-one small brown-coloured nodules of about 2 × 3 mm containing ticks in different decomposition stages were observed in 11 out of 30 foxes. Seven ticks were classified as Ixodes ricinus, while 14 ticks were determined only at the genus level (Ixodes spp.), and in two ticks no morphological key was applicable due to the advanced degradation status. By PCR, the rDNA fragment of six ticks (26.1%, 95% CI: 12.6-46.5%) was amplified, and BLAST analysis revealed a 99-100% nucleotide similarity to I. ricinus. At the histological examination, the inflammatory response varied from a mild to a moderate mixed infiltrate, primarily composed by neutrophils and lymphocytes. The results of this study confirm foxes as the main wild reservoir for SCT. The absence of SCT in other carnivores (badgers and martens) is in accordance with other studies. Ixodes ricinus is the most frequently reported tick species, corroborating the idea that longirostral ticks might be more frequently associated to SC embedment than brevirostral ticks.

A 15-year monitoring of Rickettsiales (Anaplasma phagocytophilum and Rickettsia spp.) in questing ticks in the city of Hanover, Germany.

Rickettsiales (Anaplasma phagocytophilum and Rickettsia spp.) are regarded as potentially emerging tick-borne pathogens and may change in abundance in response to global climate change. However, continuous monitoring on their prevalence in questing ticks is only available for the northern German city of Hanover. In the presented follow-up of this long-term study, 2100 questing ticks of the Ixodes ricinus/Ixodes inopinatus-complex collected from April to October 2020 at ten different recreation sites in Hanover were individually analysed for Rickettsia and A. phagocytophilum infection by quantitative real-time PCR. Together with previous results from years 2005, 2010 and 2015, the current study allows to assess potential changes in tick infection rates with Rickettsiales over a 15-year monitoring period. In 2020, 3.0% (63/2100) of ticks were infected with A. phagocytophilum, 36.0% (756/2100) with Rickettsia spp. and 1.2% (26/2100) with both pathogens. Regarding the different developmental tick stages, nymphs showed a significantly lower A. phagocytophilum prevalence of 0.5% (5/1050) than adult ticks (5.5% [58/1050]) as well as compared to females (5.4% [38/700]) and males (5.7% [20/350]). For Rickettsia spp., nymphs also showed a lower prevalence of 33.2% (349/1050) with a significant difference to adult ticks (38.8% [407/1050]) and female ticks (40.7% [285/700]), while males had a Rickettsia infection rate of 34.9% (122/350). Comparison with previous years indicated a stable A. phagocytophilum prevalence over the 15-year monitoring period. In contrast, fluctuating Rickettsia prevalences were observed, with a peak in 2015 in all developmental stages, but similar infection rates in 2005 and 2020. Therefore, epidemiological changes in response to climate change are not (yet) evident. Nevertheless, the long-term monitoring study will be continued in the future, as climatic impacts on tick and reservoir host populations may have a delayed effect on pathogen prevalence and, consequently, transmission to humans and domestic animals.

Prevalence and distribution of Anaplasma phagocytophilum in ticks collected from dogs in the United Kingdom.

BACKGROUND: Anaplasma phagocytophilum is the etiological agent of canine granulocytic anaplasmosis in dogs and causes human granulocytic anaplasmosis (HGA). Tick-borne anaplasmosis has been recognised as an emerging zoonotic health concern worldwide. The aim of the present study was to determine the prevalence of A. phagocytophilum in ticks collected from dogs in the UK and map its distribution. Routine surveillance of tick-borne disease is essential as part of a "One Health" approach to infectious disease management. METHODS: Tick DNA samples collected in 2015 as part of a large-scale tick surveillance programme were analysed using a previously validated diagnostic quantitative PCR for A. phagocytophilum. RESULTS: PCR analysis indicated that 138 out of 2994 tick DNA samples analysed were positive for A. phagocytophilum, a prevalence of 4.6% (95% CI: 3.89-5.42). Among these 138 tick DNA samples, 131 were from Ixodes ricinus, six were from Ixodes hexagonus and one was from Ixodes canisuga. Three of the I. ricinus tick DNA samples positive for A. phagocytophilum DNA were also positive for Borrelia spp. DNA and one was positive for Babesia spp. DNA, indicating co-infection. The ticks positive for the pathogen DNA were found widely distributed throughout the UK. CONCLUSIONS: These data provide important information on the prevalence and wide distribution of A. phagocytophilum in ticks infesting dogs within the UK.

Anti-tick and pathogen transmission blocking vaccines.

Ticks and tick-borne diseases are a challenge for medical and veterinary public health and often controlled through the use of repellents and acaricides. Research on vaccination strategies to protect humans, companion animals, and livestock from ticks and tick-transmitted pathogens has accelerated through the use of proteomic and transcriptomic analyses. Comparative analyses of unfed versus engorged and uninfected versus infected ticks have provided valuable insights into candidates for anti-tick and pathogen transmission blocking vaccines. An intricate interplay between tick saliva and the host's immune system has revealed potential antigens to be used in vaccination strategies. Immunization of hosts with targeted anti-tick vaccines would ideally lead to a reduction in tick numbers and prevent transmission of tick-borne pathogens. Comprehensive control of tick-borne diseases would come from successful anti-tick vaccination, vaccination preventing transmission of tick-borne diseases or a combination. Due to the close interaction with wildlife and ticks, with wildlife reservoirs enabling propagation of pathogens between ticks, the vaccination of these reservoirs is an attractive target to reduce human contact with ticks and tick-borne diseases through a one-health approach. Wildlife vaccination presents formulation and regulatory challenges which should be considered early in the development of reservoir-targeted vaccines.

Interactions between Borrelia burgdorferi and its hosts across the enzootic cycle.

The bacterial pathogen Borrelia burgdorferi is the causative agent of Lyme disease and is transmitted to humans through an Ixodes tick vector. B. burgdorferi is able to survive in both mammalian and tick hosts through careful modulation of its gene expression. This allows B. burgdorferi to adapt to the environmental and nutritional changes that occur when it is transmitted between the two hosts. Distinct interactions between the spirochete and its host occur at every step of the enzootic cycle and dictate the ability of the spirochete to survive until the next stage of the cycle. Studying the interface between B. burgdorferi, the Ixodes tick vector and the natural mammalian reservoirs has been made significantly more feasible through the complete genome sequences of the organisms and the advent of high throughput screening technologies. Ultimately, a thorough investigation of the interplay between the two domains (and two phyla within one domain) is necessary in order to completely understand how the pathogen is transmitted.

Under the skin: Ixodes ticks in the subcutaneous tissue of red foxes (Vulpes vulpes) from Germany.

BACKGROUND: Ixodes spp. are vectors of zoonotic pathogens. All three active life stages (larvae, nymphs, adults) need to feed on a host in order to develop. Usually ticks parasitize attached to the external surface of their hosts' skin. Interestingly, in some cases ticks can also be found in the subcutaneous tissue in a variety of hosts, such as red foxes (Vulpes vulpes), raccoon dogs (Nyctereutes procyonoides) and dogs. METHODS: The visceral side of 126 red fox-furs from Germany was examined visually searching for ticks. The localization of ticks was recorded and assigned to ten specific body parts. Morphological identification of ticks was performed according to standardized taxonomic protocols. Ticks which could not be further identified were examined genetically via conventional PCR targeting the 16S rRNA and cox1 gene. Hematoxylin and eosin (H&E) staining was used for histopathological examination. RESULTS: In 111 out of 126 (88.1%) examined coats, at least one tick was found in the subcutaneous tissue. A total of 1203 ticks were removed from the subcutaneous tissue. Well-preserved ticks could be identified based on morphological criteria, but most ticks were in a progressed state of decomposition. Here, morphological species identification was not successful. Also, PCR methods did not lead to a successful species identification. The following species and development stages were found by morphological identification: Ixodes ricinus (female, n = 289; male, n = 8; nymph, n = 1), I. hexagonus (female, n = 2), I. canisuga (female, n = 1). Male I. ricinus were found individually or copulating in pairs with females. Subcutaneous ticks were localized at three predominant affected body parts: ears, axillar and inguinal region. Histological examination of subcutaneous ticks revealed a granulomatous panniculitis. CONCLUSIONS: To the authors' knowledge, this is the first finding of highly prevalent subcutaneous ticks in red foxes from Germany. Subcutaneous location of ticks seems to be very common in red foxes and the rule rather than the exception. Deep embedment of longirostra and long feeding times of females seem to put the subcutaneous location in favor. Most foxes were infested in the inguinal area, where the skin is thin and less hairy.

Tick Cell Lines in Research on Tick Control.

Ticks and the diseases they transmit are of huge veterinary, medical and economic importance worldwide. Control of ticks attacking livestock and companion animals is achieved primarily by application of chemical or plant-based acaricides. However, ticks can rapidly develop resistance to any new product brought onto the market, necessitating an ongoing search for novel active compounds and alternative approaches to tick control. Many aspects of tick and tick-borne pathogen research have been facilitated by the application of continuous cell lines derived from some of the most economically important tick species. These include cell lines derived from acaricide-susceptible and resistant ticks, cell sub-lines with in vitro-generated acaricide resistance, and genetically modified tick cells. Although not a replacement for the whole organism, tick cell lines enable studies at the cellular and molecular level and provide a more accessible, more ethical and less expensive in vitro alternative to in vivo tick feeding experiments. Here we review the role played by tick cell lines in studies on acaricide resistance, mode-of-action of acaricides, identification of potential novel control targets through better understanding of tick metabolism, and anti-tick vaccine development, that may lead to new approaches to control ticks and tick-borne diseases.

[Confirmation of Tick-borne encephalitis virus in an European hedgehog (Erinaceus europaeus)]. / Frühsommer-Meningoenzephalitis-Virus Nachweis beim Europäischen Igel (Erinaceus europaeus).

INTRODUCTION: European hedgehogs (Erinaceus europaeus) have a high exposure to various ticks, which could transmit pathogens with direct health significance for the host and may have zoonotic potential. Tick-borne meningoencephalitis (FSME) is an important tick-borne disease in Switzerland, caused by the tick-borne encephalitis virus. About its occurrence in the European hedgehog population is little known. The present study examined various organs, blood and ticks of 65 European hedgehogs to obtain data of FSME virus presence in this species in Switzerland. Real-time RT-PCR from the lungs, liver, spleen and kidney of 56 hedgehogs and of 114 infesting ticks (Ixodes hexagonus or Ixodes ricinus) were used for the detection of viral RNA. In addition, 19 blood samples were tested for antibodies against FSME by ELISA. FSME virus antibodies were detected for the first time in the serum of a European hedgehog. Lung and spleen tissue samples of the same animal tested also weak virus positive on RT-PCR. Clinically, the hedgehog showed neurological symptoms, although these symptoms could have originated from an other diseases. No viral RNA was detected in any of the ticks. This study could not confirm if the meningoencephalitis in the hedgehog was triggered by the FSME viral infection. Nevertheless, the simultaneous detection of antibodies and virus RNA in the same animal makes the European hedgehog a competent host of the tick-borne encephalitis virus and leads to the assumption that this species can act as a reservoir.

INTRODUCTION: En raison du nombre élevé de tiques présents chez les hérissons d'Europe (Erinaceus europaeus), ces animaux sont fortement exposés aux différents pathogènes qu'ils transmettent, pathogènes qui, en plus de l'importance directe pour la santé de l'hôte, peuvent aussi avoir un potentiel en termes de zoonose. La méningo-encéphalite à tique est, en Suisse, une maladie importante transmise par les tiques. Elle est causée par le virus de la méningo-encéphalite verno-estivale. Son occurrence chez les hérissons d'Europe est jusqu'à maintenant peu connue. Au travers de l'étude des organes, du sang et des tiques provenant de 65 hérissons européens, il devrait pour la première fois être possible de se prononcer sur la présence du virus chez cette espèce en Suisse. La détection de l'ARN viral a été effectuée au moyen d'une RT-PCR en temps réel sur les poumons, le foie, la rate et les reins de 56 hérissons ainsi que sur un total de 114 tiques dont ils étaient porteurs, appartenant aux espèces Ixodes hexagonus ou Ixodes ricinus. En outre, 19 échantillons de sang ont été testés par ELISA pour des anticorps contre le virus. Dans la présente étude, des anticorps contre le virus de l'encéphalite à tiques dans le sérum d'un hérisson européen ont pu être détectés pour la première fois. Les échantillons de poumon et de rate du même animal ont également montré une faible présence virale. Le même hérisson a présenté des symptômes neurologiques, mais ceux-ci pouvaient également être associés à d'autres maladies. On n'a démontré la présence d'ARN viral chez aucune tique. La possibilité d'une encéphalite causée par l'infection virale chez les hérissons ne peut pas être confirmée ou exclues avec cette étude. La détection simultanée des anticorps et de l'ARN viral chez le même animal fait du hérisson européen non seulement un hôte compétent du virus de l'encéphalite verno-estivale mais donne également également à penser que cette espèce pourrait servir de réservoir.

Ixodid ticks parasitizing wild carnivores in Romania.

In Romania, data regarding hard-tick diversity and tick-host associations in wild carnivores are scarce. We aimed to identify tick species in wild carnivores and to establish reliable data on tick-host associations. The study was conducted in various Romanian localities from all five ecoregions found in the country. Fourteen species of wild carnivores were examined. Immature and adult ticks were collected and identified using the morphological keys. The frequency and mean intensity of tick infestation, overall and differentiated by species, developmental stage and host were calculated. Of 202 wild carnivores, 68 were parasitized by seven tick species (predominantly Ixodes ricinus, I. hexagonus and Dermacentor reticulatus). The mean intensity of tick infestation was similar in males (6.97, BCa 95% CI 5.15-9.88) and females (5.76, BCa 95% CI 4.15-9.17). The highest prevalence of infested animals was recorded in the pannonian and steppic ecoregions, 66.7 and 52.7%, respectively. In the continental ecoregion the prevalence was 26.7%, whereas in the pontic ecoregion it was 28%. The lowest value, 16.7% was recorded in the alpine ecoregion. In total 430 ticks were collected, and 24.8% (n = 50) of the animals were infested with more than one tick species. Fourteen new tick-host associations were recorded. Our results suggest that anthropogenic changes of the environment lead to the diminishing of the boundaries, between wild and domestic animals, increasing the exposure for both animals and humans, to infective agents, including tick-borne pathogens.

Co-infection of Trypanosoma pestanai and Anaplasma phagocytophilum in a dog from Germany.

Infections with arthropod-borne pathogens are an increasing threat world-wide that requires heightened vigilance from veterinary and medical practitioners, especially when they involve new or unusual organisms. A dog was presented to a local veterinary clinic in Germany with malaise, pale mucous membranes and stiff joints. Clinical assessment revealed pyrexia, leukopenia and thrombocytopenia. On suspicion of a tick-borne infection, blood samples were examined for clinical and biochemical parameters and subjected to a Anaplasma phagocytophilum-, Borrelia spp.- and Ehrlichia canis-specific real-time PCR. Additionally, a sample of the pre-therapeutic buffy coat was co-cultured with the Ixodes scapularis cell-line ISE6 for 20days. Only the PCR specific for A. phagocytophilum DNA yielded a positive result, and furthermore, Anaplasma morulae were visible in granulocytes and tick cells. After co-culturing, extracellular trypomastigote and epimastigote stages of Trypanosoma sp. with an average length of 29.7µm were observed, featuring a pointed posterior end. Sequence analysis of a 2080bp fragment of the 18S rRNA gene showed 99% identity to the 18S rRNA gene of Trypanosoma pestanai, previously described from a European badger (Meles meles) in France. The dog's condition improved rapidly in response to doxycycline treatment for three weeks. The clinical status normalized and clinical blood parameters were found to be within the reference ranges. To our knowledge this is the first description of T. pestanai infection in a dog, the first detection of T. pestanai in Germany and the first documented co-infection with these two pathogens. Co-infections with unusual opportunistic vector-borne pathogens should be considered, if acute canine granulocytic anaplasmosis is evident.

Tick infestation in birds and prevalence of pathogens in ticks collected from different places in Germany.

The importance of ticks and tick-borne pathogens for human and animal health has been increasing over the past decades. For their transportation and dissemination, birds may play a more important role than wingless hosts. In this study, tick infestation of birds in Germany was examined. Eight hundred ninety-two captured birds were infested with ticks and belonged to 48 different species, of which blackbirds (Turdus merula) and song thrushes (Turdus philomelos) were most strongly infested. Ground feeders were more strongly infested than non-ground feeders, sedentary birds more strongly than migratory birds, and short-distance migratory birds more strongly than long-distance migratory birds. Mean tick infestation per bird ranged between 2 (long-distance migratory bird) and 4.7 (sedentary bird), in some single cases up to 55 ticks per bird were found. With the exception of three nymphs of Haemaphysalis spp., all ticks belonged to Ixodes spp., the most frequently detected tick species was Ixodes ricinus. Birds were mostly infested by nymphs (65.1 %), followed by larvae (32.96 %). Additionally, ticks collected from birds were examined for several pathogens: Tick-borne encephalitis virus (TBEV) and Sindbisvirus with real-time RT-PCR, Flaviviruses, Simbuviruses and Lyssaviruses with broad-range standard RT-PCR-assays, and Borrelia spp. with a Pan-Borrelia real-time PCR. Interestingly, no viral pathogens could be detected, but Borrelia spp. positive ticks were collected from 76 birds. Borrelia (B.) garinii, B. valaisiaina, B. burgdorferi s.s. and B. afzelii were determined. The screening of ticks and birds for viral pathogens with broad range PCR-assays was tested and the use as an "early warning system" is discussed.

New localities of Dermacentor reticulatus ticks in the Baltic countries.

According to previous observations in three Baltic States, Dermacentor reticulatus was found only in Lithuania where it occurred mainly in the central and western parts of the country. During the past decade, evidence about a changing distribution of D. reticulatus in the Baltic countries was provided by the occurrence of canine babesiosis in the new locations in Lithuania and Latvia. In the present study the current distribution of D. reticulatus in Lithuania and Latvia was investigated. Ticks were collected in different habitats in 2013-2014. A total of 3693 questing ticks belonging to D. reticulatus (n = 2789), Ixodes ricinus (n = 896) and I. persulcatus (n=8) were collected in Lithuania and Latvia. Questing D. reticulatus ticks were found in 73.4% (58/79) and in 44.4% (12/28) of the sampling localities in Lithuania and Latvia, respectively. Relative abundances of the ticks in different habitats were compared. All sites with high abundance of D. reticulatus ticks were localized in open areas close to a water basin and mixed forest. The present study demonstrates that during the past two decades D. reticulatus has expanded its range in the Baltic countries. D. reticulatus has been detected in 38 new localities in which this species had not been previously reported. The northern border of D. reticulatus in central Europe moved further to the north. New localities (n = 12) with D. reticulatus occurrence have been found in southern Latvia.

A molecular survey of Babesia spp. and Theileria spp. in red foxes (Vulpes vulpes) and their ticks from Thuringia, Germany.

Wild canines which are closely related to dogs constitute a potential reservoir for haemoparasites by both hosting tick species that infest dogs and harbouring tick-transmitted canine haemoparasites. In this study, the prevalence of Babesia spp. and Theileria spp. was investigated in German red foxes (Vulpes vulpes) and their ticks. DNA extracts of 261 spleen samples and 1953 ticks included 4 tick species: Ixodes ricinus (n=870), I. canisuga (n=585), I. hexagonus (n=485), and Dermacentor reticulatus (n=13) were examined for the presence of Babesia/Theileria spp. by a conventional PCR targeting the 18S rRNA gene. One hundred twenty-one out of 261 foxes (46.4%) were PCR-positive. Out of them, 44 samples were sequenced, and all sequences had 100% similarity to Theileria annae. Similarly, sequencing was carried out for 65 out of 118 PCR-positive ticks. Theileria annae DNA was detected in 61.5% of the sequenced samples, Babesia microti DNA was found in 9.2%, and Babesia venatorum in 7.6% of the sequenced samples. The foxes were most positive in June and October, whereas the peak of tick positivity was in October. Furthermore, the positivity of the ticks was higher for I. canisuga in comparison to the other tick species and for nymphs in comparison to adults. The high prevalence of T. annae DNA in red foxes in this study suggests a reservoir function of those animals for T. annae. To our knowledge, this is the first report of T. annae in foxes from Germany as well as the first detection of T. annae and B. microti in the fox tick I. canisuga. Detection of DNA of T. annae and B. microti in three tick species collected from foxes adds new potential vectors for these two pathogens and suggests a potential role of the red fox in their natural endemic cycles.

Coinfection of tick cell lines has variable effects on replication of intracellular bacterial and viral pathogens.

Ticks transmit various human and animal microbial pathogens and may harbour more than one pathogen simultaneously. Both viruses and bacteria can trigger, and may subsequently suppress, vertebrate host and arthropod vector anti-microbial responses. Microbial coinfection of ticks could lead to an advantage or disadvantage for one or more of the microorganisms. In this preliminary study, cell lines derived from the ticks Ixodes scapularis and Ixodes ricinus were infected sequentially with 2 arthropod-borne pathogens, Borrelia burgdorferi s.s., Ehrlichia ruminantium, or Semliki Forest virus (SFV), and the effect of coinfection on the replication of these pathogens was measured. Prior infection of tick cell cultures with the spirochaete B. burgdorferi enhanced subsequent replication of the rickettsial pathogen E. ruminantium whereas addition of spirochaetes to cells infected with E. ruminantium had no effect on growth of the latter. Both prior and subsequent presence of B. burgdorferi also had a positive effect on SFV replication. Presence of E. ruminantium or SFV had no measurable effect on B. burgdorferi growth. In tick cells infected first with E. ruminantium and then with SFV, virus replication was significantly higher across all time points measured (24, 48, 72h post infection), while presence of the virus had no detectable effect on bacterial growth. When cells were infected first with SFV and then with E. ruminantium, there was no effect on replication of either pathogen. The results of this preliminary study indicate that interplay does occur between different pathogens during infection of tick cells. Further study is needed to determine if this results from direct pathogen-pathogen interaction or from effects on host cell defences, and to determine if these observations also apply in vivo in ticks. If presence of one pathogen in the tick vector results in increased replication of another, this could have implications for disease transmission and incidence.

Unique strains of Anaplasma phagocytophilum segregate among diverse questing and non-questing Ixodes tick species in the western United States.

The emerging tick-borne pathogen Anaplasma phagocytophilum infects humans, domestic animals, and wildlife throughout the Holarctic. In the western US, the ecology of A. phagocytophilum is particularly complex, with multiple pathogen strains, tick vectors, and reservoir hosts. A recent phylogenetic analysis of A. phagocytophilum strains isolated from various small mammal hosts in California documented distinct clustering of woodrat strains separate from sciurid (chipmunk and squirrel) strains. Here, we identified strains of A. phagocytophilum in various Ixodes tick species in California and related these genotypes to those found among reservoir and clinical hosts from the same areas. The sequences from all of the nidicolous (nest-dwelling) Ixodes ticks grouped within a clade that also contained all of the woodrat-origin A. phagocytophilum strains. Two of the I. pacificus sequences were also grouped within this woodrat clade, while the remaining five belonged to a less genetically diverse clade that included several sciurid-origin strains as well as a dog, a horse, and a human strain. By comparing A. phagocytophilum strains from multiple sources concurrently, we were able to gain a clearer picture of how A. phagocytophilum strains in the western US are partitioned, which hosts and vectors are most likely to be infected with a particular strain, and which tick species and reservoir hosts pose the greatest health risk to humans and domestic animals.

Babesia odocoilei infection in a Saskatchewan elk (Cervus elaphus canadensis) herd.

An 8-year-old female elk (Cervus elaphus canadensis) cow, presented for chronic severe weight loss and unthriftiness, was diagnosed with Babesia odocoilei infection based on blood smear evaluation, polymerase chain reaction (PCR), and DNA sequence analysis. Subsequently, velvet antler from a male that died acutely on the same farm was also PCR positive for Babesia spp. Both animals originated from a game ranch of Saskatchewan-bred and -raised animals with no known history of tick exposure, but with a history of numerous sudden deaths of unknown etiology. The presence of B. odocoilei in Canada might be a result of a recent introduction that could have deleterious effects on local wild ungulates or may represent discovery of a previously unrecognized endemic disease in local wildlife.