Candidatus Neoehrlichia sp. in an Austrian fox is distinct from Candidatus Neoehrlichia mikurensis, but closer related to Candidatus Neoehrlichia lotoris

Tick-Borne Bacterial Diseases in Europe: Threats to public health

BACKGROUND

Tick-borne diseases, caused by bacterial pathogens, pose a growing threat to public health in Europe. This paper provides an overview of the historical context of the discovery of the most impactful pathogens transmitted by ticks, including Borrelia burgdorferi sensu lato, Rickettsia spp., Anaplasma spp., Francisella spp., Ehrlichia spp., and Neoehrlichia mikurensis. Understanding the historical context of their discovery provides insight into the evolution of our understanding of these pathogens.

METHODS AND RESULTS

Systematic investigation of the prevalence and transmission dynamics of these bacterial pathogens is provided, highlighting the intricate relationships among ticks, host organisms, and the environment. Epidemiology is explored, providing an in-depth analysis of clinical features associated with infections. Diagnostic methodologies undergo critical examination, with a spotlight on technological advancements that enhance detection capabilities. Additionally, the paper discusses available treatment options, addressing existing therapeutic strategies and considering future aspects.

CONCLUSIONS

By integrating various pieces of information on these bacterial species, the paper aims to provide a comprehensive resource for researchers and healthcare professionals addressing the impact of bacterial tick-borne diseases in Europe. This review underscores the importance of understanding the complex details influencing bacterial prevalence and transmission dynamics to better combat these emerging public health threats.

Red fox (Vulpes vulpes) play an important role in the propagation of tick-borne pathogens

The red fox (Vulpes vulpes) is the most widespread free-living carnivore in the world. Over the years, foxes have been recognized as hosts for a number of tick-borne pathogens. However, their role as reservoirs for zoonotic tick-borne diseases is poorly understood. The aim of our study was to investigate tick-borne pathogens in the red fox population in the Czech Republic. Out of 117 red foxes, 110 (94.02%) individuals tested positive for the presence of at least one pathogen by the combined PCR and sequencing approach. Hepatozoon canis was the most frequently detected pathogen (n = 95; 81.2%), followed by Babesia vulpes (n = 75; 64.1%). Babesia canis was not detected in our study. Four (3.42%) red foxes were positive for Candidatus Neoehrlichia sp., 3 (2.56%) for Anaplasma phagocytophilum, and one red fox (0.85%) tested positive for the presence of Ehrlichia sp. DNA. Overall, DNA of spirochetes from the Borrelia burgdorferi s.l. complex was detected in 8.6% of the foxes and B. miyamotoi in 5.12% of the samples. As a carnivore found in all ecosystems of Central Europe, foxes obviously contribute to transmission of tick-borne pathogens such as A. phagocytophilum, B. burgdorferi s.l., and B. myiamotoi. In addition, foxes apparently harbour a community of pathogens, associated with this host in local ecological context, dominated by H. canis and B. vulpes (possibly also Candidatus Neoehrlichia sp.). These species have the potential to spread to the domestic dog population and should be included in the differential diagnosis of febrile diseases with hematologic abnormalities in dogs.

Red Foxes (Vulpes vulpes) Are Exposed to High Diversity of Borrelia burgdorferi Sensu Lato Species Infecting Fox-Derived Ixodes Ticks in West-Central Poland

The role of red fox, Vulpes vulpes, and its associated ticks in maintaining Borrelia burgdorferi sensu lato (s.l.) was studied. A total of 1583 ticks were removed from ears of 120 infested animals and were identified as species using a nested PCR targeting the ITS2 and coxI fragments of Ixodes DNA. Ixodes kaiseri prevailed (76%), followed by I. canisuga, I. ricinus, and I. hexagonus. In total, 32.4% of 943 ticks revealed Borrelia DNA and 10 species of B. burgdorferi s.l. complex were identified. Borrelia garinii and B. afzelii comprised 70% of all infections. The other eight species included B. americana, B. bissettiae, B. burgdorferi sensu stricto (s.s.), B. californiensis, B. carolinensis, B. lanei, B. spielmanii, and B. valaisiana. Analysis of tissues from 243 foxes showed that 23.5% were infected with B. burgdorferi s.l. Borrelia garinii was detected in 91% of the infected animals, including 31% of mixed infections with B. afzelii, the second most prevalent species, followed by B. spielmanii. The predominance of B. garinii in PCR-positive animals and infected larval ticks (38.1%), suggests that this spirochete and B. afzelii are preferentially associated with foxes. Although red foxes are exposed to a high diversity of B. burgdorferi s.l. species found in engorged Ixodes ticks, their reservoir competence for most of them appears to be low.

Infectious Wildlife Diseases in Austria-A Literature Review From 1980 Until 2017

This literature review examines infectious wildlife disease research in Austria. We analyzed 226 research papers, published between 1980 and 2017. We determined that wildlife disease papers increased significantly from 0.8 ± 0.8 publications per year in the first decade (1980–1989) when compared to 2008–2017 with an average of 12.9 ± 4.1 publications per year. We illustrate information about the most investigated diseases and highlight the lack of research into certain wildlife pathogens. A special emphasis was given to diseases with zoonotic potential. The review showed that research focused on a few select species like the red fox (Vulpes vulpes), red deer (Cervus elaphus), and wild boar (Sus scrofa), all game species. Moreover, diseases affecting livestock and human health were seen more often. The review also found that only a low number of publications actually stated disease prevalence and confidence interval data. The reported diseases identified were classified according to their notifiable status and the distribution at the wildlife–human and wildlife–livestock interface. Furthermore, we try to argue why research into some diseases is prioritized, and why other diseases are underrepresented in current Austrian research. While spatiotemporal indicators could not be assessed due to the variability in methodologies and objectives of various studies, the information provided by this review offers the first comprehensive evaluation of the status of infectious wildlife disease research in Austria. Therefore, this study could assist investigators to identify further areas of priorities for research and conservation efforts and for wildlife management professionals to inform policy and funding strategies. With this review, we want to encourage research in the field of wildlife diseases in Austria to enhance current knowledge in the prevention of further loss in biodiversity and to find new measures to promote “One Health” on a global scale.

Candidatus Neoehrlichia sp. (FU98) and Borrelia burgdorferi Sensu Lato in Red Foxes (Vulpes vulpes) from Serbia

Human activities such as deforestation, urbanization, and environmental pollution lead to a reduction in the spatial boundary between wild animals, domestic animals and humans. These activities increase the risk for the emergence of pathogens from the sylvatic cycle in the population of domestic animals and humans. Foxes are recognized as potential reservoirs for a number of bacterial pathogens of medical and public health concern. The aim of the present study was to investigate the prevalence and spatial distribution of bacterial tick-borne pathogens from the Anaplasmataceae family, Borrelia burgdorferi sensu lato (s.l.), Rickettsia spp., Coxiella burnetii, Francisella tularensis, Bartonella spp., in the red fox population from Serbia and to discuss the obtained results from the epidemiological point of view. Legally hunted red foxes (Vulpes vulpes) from 14 localities in Serbia were included in the study and spleen samples from 129 animals were tested with conventional PCR assays for the presence of bacterial tick-borne pathogens. DNA of Candidatus Neoehrlichia sp. (FU98), Borrelia burgdorferi sensu stricto, Borrelia lusitaniae, and Borrelia garinii was detected in 6 (4.7%), 1 (0.8%), 2 (1.6%) and 1 (0.8%) animals, respectively. Co-infection by Candidatus Neoehrlichia sp. (FU98) and B. garinii was detected in one animal. All samples were negative for other tested bacterial tick-borne pathogens. The results of the present study indicate the potential role of foxes in natural cycles of Candidatus Neoehrlichia sp. (FU98) and causative agents of Lyme borreliosis in the investigated areas. Further research is required to elucidate the role of foxes in the epidemiology of these and other tick-borne zoonotic pathogens in the Republic of Serbia.

Diversity of Anaplasma and Ehrlichia/Neoehrlichia Agents in Terrestrial Wild Carnivores Worldwide: Implications for Human and Domestic Animal Health and Wildlife Conservation

Recently, the incidence and awareness of tick-borne diseases in humans and animals have increased due to several factors, which in association favor the chances of contact among wild animals and their ectoparasites, domestic animals and humans. Wild and domestic carnivores are considered the primary source of tick-borne zoonotic agents to humans. Among emergent tick-borne pathogens, agents belonging to family Anaplasmataceae (Order Rickettsiales) agents stand out due their worldwide distribution and zoonotic potential. In this review we aimed to review the genetic diversity of the tick-transmitted genera Ehrlichia, Anaplasma and "Candidatus Neoehrlichia sp." in wild carnivores Caniformia (Canidae, Mustelidae and Ursidae) and Feliformia (Felidae, Hyanidae, Procyonidae and Viverridae) worldwide, discussing the implications for human and domestic animal health and wildlife conservation. Red foxes (Vulpes vulpes) have been identified as hosts for Anaplasma spp. (A. phagocytophilum, Anaplasma ovis, A. platys), Ehrlichia canis and "Candidatus Neoehrlichia sp." (FU98 strain) and may contribute to the maintaenance of A. phagocytophilum in Europe. Raccoons (Procyon lotor) have been reported as hosts for E. canis, A. bovis, "Candidatus Neoehrlichia lotoris" and A. phagocytophilum, and play a role in the maintenance of A. phagocytophilum in the USA. Raccoon dogs (Nyctereutes procyonoides) may play a role as hosts for A. bovis and A. phagocytophilum. New Ehrlichia and/or Anaplasma genotypes circulate in wild canids and felids from South America and Africa. While Ehrlichia sp. closely related to E. canis has been reported in wild felids from Brazil and Japan, Anaplasma sp. closely related to A. phagocytophilum has been detected in wild felids from Brazil and Africa. Red foxes and mustelids (otters) are exposed to E. canis in countries located in the Mediaterranean basin, probably as a consequence of spillover from domestic dogs. Similarly, E. canis occurs in procyonids in North (raccoons in USA, Spain) and South (Nasua nasua in Brazil) Hemispheres, in areas where E. canis is frequent in dogs. While "Candidatus Neoehrlichia lotoris" seems to be a common and specific agent of raccoons in the USA, "Candidatus Neoehrlichia sp." (FU98 strain) seems to show a broader range of hosts, since it has been detected in red fox, golden jackal (Canis aureus) and badger (Meles meles) in Europe so far. Brown (Ursus arctos) and black (Ursus americanus) bears seem to play a role as hosts for A. phagocytophilum in the North Hemisphere. Anaplasma bovis has been detected in wild Procyonidae, Canidae and Felidae in Asia and Brazil. In order to assess the real identity of the involved agents, future works should benefit from the application of MLST (Multi Locus Sequence Typing), WGS (Whole Genome Sequencing) and NGS (Next Generation Sequencing) technologies aiming at shedding some light on the role of wild carnivores in the epidemiology of Anaplasmataceae agents.

Ticks are more suitable than red foxes for monitoring zoonotic tick-borne pathogens in northeastern Italy

BACKGROUND

Northeastern Italy is a hotspot for several tick-borne pathogens, transmitted to animals and humans mainly by Ixodes ricinus. Here we compare the results of molecular monitoring of ticks and zoonotic TBPs over a six-year period, with the monitoring of red foxes (Vulpes vulpes) in an endemic area.

RESULTS

In the period 2011-2016, 2,578 ticks were collected in 38 sites of 20 municipalities of Belluno Province. Individual adults (264), pooled larvae (n = 330) and nymphs (n = 1984) were screened for tick-borne encephalitis virus, Borrelia burgdorferi (s.l.), Rickettsia spp., Babesia spp., Anaplasma phagocytophilum and "Candidatus Neoehrlichia mikurensis" by specific SYBR green real-time PCR assays and sequencing. The spleens of 97 foxes, culled in the period 2015-2017 during sport hunting or population control programs, were also screened. Overall, nine different pathogens were found in I. ricinus nymph and adult ticks: Rickettsia helvetica (3.69%); R. monacensis (0.49%); four species of the B. burgdorferi (s.l.) complex [B. afzelii (1.51%); B. burgdorferi (s.s.) (1.25%); B. garinii (0.18%); and B. valaisiana (0.18%)]; A. phagocytophilum (3.29%); "Candidatus N. mikurensis" (1.73%); and Babesia venatorum (0.04%). Larvae were collected and screened in the first year only and two pools (0.6%) were positive for R. helvetica. Tick-borne encephalitis virus was not found in ticks although human cases do occur in the area. The rate of infection in ticks varied widely according to tick developmental stage, site and year of collection. As expected, adults were the most infected, with 27.6% harboring at least one pathogen compared to 7.3% of nymphs. Pathogens with a minimum infection rate above 1% were recorded every year. None of the pathogens found in ticks were detectable in the foxes, 52 (54%) of which were instead positive for Babesia cf. microti (also referred to as Babesia microti-like, "Theileria annae", "Babesia annae" and "Babesia vulpes").

CONCLUSIONS

The results show that foxes cannot be used as sentinel animals to monitor tick-borne pathogens in the specific epidemiological context of northeastern Italy. The high prevalence of Babesia cf. microti in foxes and its absence in ticks strongly suggests that I. ricinus is not the vector of this pathogen.

The occurrence of Anaplasmataceae in European populations of invasive carnivores

The raccoon (Procyon lotor) and the raccoon dog (Nyctereutes procyonoides) belong to a group of the invasive species. The introduced species as potential reservoirs for vector-borne pathogens have been the subject of recent research, though there are still no data with reference to the European population of the raccoon, and few studies concern only the raccoon dog. This study shows the occurrence of Anaplasmataceae representatives in raccoons and a sympatric population of the raccoon dogs obtained from the area of Poland and Germany. During the study, the occurrence of Anaplasma phagocytophilum ecotype I in the introduced raccoon in northwestern Poland was revealed. Additionally, Candidatus Neoehrlichia sp. (FU98) was identified for the first time in the raccoon dog in Central Europe and thereby the raccoon dog is a new host for this pathogen.

"Candidatus Neoehrlichia chilensis" sp. nov.: Molecular detection and characterization of a novel Anaplasmataceae in wild rodents from Valdivia, southern Chile

This study aimed to screen wild rodents from southern Chile, for the presence of Anaplasmatacea. Spleen samples from 33 wild rodents trapped in Valdivia Province were screened by conventional PCR (cPCR), targeting the Anaplasmataceae 16S rRNA gene (16S). Positive samples were further evaluated, targeting a larger 16S fragment, groEL operon, and gltA gene, followed by sequencing and phylogenetic analysis. Anaplasmataceae DNA was detected in 15% (five of 33) of the tested rodents (Abrothrix sp. [four of five] and Mus musculus [one of five]). Analysis of sequenced products based on the 16S gene revealed high similarity with "Ca. Neoehrlichia mikurensis," "Ca. Neoehrlichia lotoris" and "Ca. Neoehrlichia arcana" (97.8%-98.6%). A lower similarity was observed with Candidatus Neoehrlichia groEL (89.7%-92%) and gltA (79.5%-79.9%) loci. According to the 16SrRNA, groEL and gltA phylogenetic analyses, two closely related genotypes of "Candidatus Neoehrlichia" spp. from Chile were observed, which clustered together in a separate clade from other species in this genus. This study suggests the presence of two genotypes of a novel species of "Candidatus Neoehrlichia," proposed as "Candidatus Neoehrlichia chilensis," circulating in rodents from Chile. This is the first report of "Ca. Neoehrlichia" species in rodents from America.

'Candidatus Neoehrlichia mikurensis' in Europe

'Candidatus Neoehrlichia mikurensis' is an uncultured emerging bacterium that is provisionally included in the family Anaplasmataceae. In Europe, it is transmitted by Ixodes ricinus ticks. Rodents are the reservoirs. It is widely distributed in mammals (both wild and domestic) and birds. It causes an inflammatory disease in humans with underlying diseases, but the microorganism also affects immunocompetent individuals in which asymptomatic infection has been recognized. A high degree of suspicion and the use of molecular tools are needed for the correct diagnosis. Efforts to cultivate it and to investigate its pathogenesis should be a priority.

Tick-borne pathogens and their reservoir hosts in northern Italy

The aim of this study was to determine the occurrence of Anaplasma phagocytophilum, Rickettsia spp., Babesia spp., and Candidatus Neoehrlichia mikurensis in Ixodes spp. ticks removed from wildlife, domestic animals and humans in the Province of Trento (northern Italy) in order to better understand their ecology and provide public health professionals with an updated list of pathogens which should be considered during their diagnostic procedures after a tick bite. During 2011-2012, 848 feeding ticks at all life stages (adults, nymphs and larvae) from various hosts (wild ungulates, birds and rodents; domestic sheep, dogs and humans) were collected. The highest prevalences of A. phagocytophilum and Rickettsia spp. were detected in adult and nymphal tick stages feeding on wild ungulates (11.4% prevalence for both pathogens), while the Babesia spp. prevailed in nymphal and larval ticks feeding on wild birds (7.7%). A wide spectrum of tick-borne agents was present in larval ticks: those detached from wild ungulates were positive for A. phagocytophilum, B. venatorum, R. helvetica, R. monacensis and R. raoultii, while those removed from wild rodents were positive for B. venatorum, R. helvetica, R. monacensis and Ca. N. mikurensis, and ticks from wild birds carried A. phagocytophilum, B. venatorum, B. capreoli and R. helvetica. This study provides evidence of circulation of five tick-borne pathogens not reported in this region before, specifically R. raoultii, R. monacensis, B. venatorum, B. capreoli and B. microti. Furthermore, it discusses the epidemiological role of the animal species from which the ticks were collected highlighting the needs for more experimental studies especially for those pathogens where transovarial transmission in ticks has been demonstrated.

Occurrence and diversity of arthropod-transmitted pathogens in red foxes (Vulpes vulpes) in western Austria, and possible vertical (transplacental) transmission of Hepatozoon canis

Red fox (Vulpes vulpes) is the most abundant wild canid species in Austria, and it is a well-known carrier of many pathogens of medical and veterinary concern. The main aim of the present study was to investigate the occurrence and diversity of protozoan, bacterial and filarial parasites transmitted by blood-feeding arthropods in a red fox population in western Austria. Blood (n = 351) and spleen (n = 506) samples from foxes were examined by PCR and sequencing and the following pathogens were identified: Babesia canis, Babesia cf. microti (syn. Theileria annae), Hepatozoon canis, Anaplasma phagocytophilum, Candidatus Neoehrlichia sp. and Bartonella rochalimae. Blood was shown to be more suitable for detection of Babesia cf. microti, whilst the spleen tissue was better for detection of H. canis than blood. Moreover, extremely low genetic variability of H. canis and its relatively low prevalence rate observed in this study may suggest that the parasite has only recently been introduced in the sampled area. Furthermore, the data presented here demonstrates, for the first time, the possible vertical transmission of H. canis from an infected vixen to the offspring, and this could explain the very high prevalence in areas considered free of its main tick vector(s).

The raccoon dog (Nyctereutes procyonoides) and the raccoon (Procyon lotor)-their role and impact of maintaining and transmitting zoonotic diseases in Austria, Central Europe

The neozoan species raccoon dog (Nyctereutes procyonoides) and raccoon (Procyon lotor) are widespread in Europe and potential vectors of many diseases that can threaten human and domestic animal health. Facing a further spread of these species, it is important to know about (i) pathogens imported and/or (ii) pathogens acquired in the new habitat. Thus, we investigated the parasite fauna of wild raccoon dogs and raccoons from Austria, at the edge of their new distribution range. The eight examined raccoons were nearly free of pathogens including Baylisascaris procyonis, and thus assumed to have a low epidemiological impact, so far. Out of ten raccoon dog specimens, we found one from western Austria to be infected with Echinococcus multilocularis and another three from the eastern wetland regions to harbour adults of Alaria alata. Furthermore, we detected Babesia cf. microti in five of eight raccoon dogs all over Austria but none of our samples were tested positive for Trichinella spp. Nevertheless, the raccoon dog seems to be a relevant host, at least for the zoonotic pathogens E. multilocularis and A. alata, and we suggest to further monitor the raccoon dogs parasite fauna.

Vector-borne pathogens in dogs and red foxes from the federal state of Brandenburg, Germany

Dirofilaria repens is endemic in eastern and southern European regions but was recently found in Germany in dogs, mosquitoes and one human patient. Since some of the positive dog and mosquito samples were collected in Brandenburg, it was aimed to systematically assess the prevalence of D. repens and other canine vector-borne pathogens in Brandenburg. Dog owners also received a questionnaire and were asked to provide more information about the dogs including travel history. In total, 1023 dog blood samples as well as 195 fox spleen and 179 fox blood samples were collected. DNA was analysed by PCR for the presence of filariae, piroplasms, anaplasmataceae and Rickettsia spp. Filariae were detected in six dogs (0.6%), two were positive for DNA from D. repens, two from Dirofilaria immitis and two from Acanthocheilonema reconditum. One of the D. repens positive dogs originated from an animal shelter in Brandenburg, but the origin of the other one remained unknown. Interestingly, both D. repens ITS-1 sequences showed 100% identity to a D. repens sample obtained from a Japanese woman that travelled in Europe and were 97% identical to a newly proposed species Dirofilaria sp. 'hongkongensis' described from Hong Kong. However, identity to other D. repens sequences from Thailand was considerably lower (81%). Identity of 12S rRNA and cytochrome oxidase I to D. repens samples from southern Europe was 99%. Due to the low number of Dirofilaria spp. positive dogs and since the origin of these was unknown, endemic occurrence of Dirofilaria in Brandenburg could not be confirmed. Anaplasma phagocytophilum was found in 15 dogs (1.5%), Candidatus Neoehrlichia mikurensis in three dogs (0.3%) and E. canis in one dog (0.1%), which was co-infected with D. repens. Rickettsia spp. were detected in 8 dogs (0.8%), seven were Rickettsia raoultii and one was Rickettsia felis. To the author's knowledge, R. raoultii DNA was detected for the first time in dogs in Germany in this study and Candidatus N. mikurensis for the second time. In spleen samples of red foxes with 47.5% a high prevalence of piroplasms was found. Sequencing of 11 samples identified 10 as Theileria annae. Despite the high prevalence of this pathogen in its reservoir host, it was absent in dog samples. In one dog (0.1%), Babesia canis was detected but there was no further information about the dog's origin. Evaluation of the questionnaire identified a high proportion of dogs (74.2%, n=233) which was not protected by ectoparasiticides. Moreover, 21.2% (n=236) of the dogs originated from inland or abroad shelters, and therefore might potentially come from areas endemic for dirofilariosis or babesiosis.

A new case of the enigmatic Candidatus Neoehrlichia sp. (FU98) in a fox from the Czech Republic

This study reports a new case of Candidatus Neoehrlichia sp. (FU98) infection in a fox from the Czech Republic, and provides confirmatory evidence on the occurrence of this newly identified sequence type. However, further studies are needed to investigate the distribution, host range and possible vector(s) for this bacterium, as well as its impact on animals and humans.