Epidemiology, genetic variants and clinical course of natural infections with Anaplasma phagocytophilum in a dairy cattle herd

Molecular detection and diversity of tick-borne rickettsial pathogens in ticks collected from camel (Camelus dromedarius) in Upper Egypt

Tick-borne rickettsial pathogens pose significant threats to public and animal health. In Upper Egypt, limited information exists regarding the prevalence and diversity of such tick-borne pathogens. Therefore, this study aimed to conduct a comprehensive investigation to elucidate the presence and variety of tick-borne rickettsial pathogens in Upper Egyptian camels. Our results revealed a prevalence of 2.96 % for Anaplasma marginale and 0.34 % for Candidatus Anaplasma camelii among Hyalomma ticks. However, Ehrlichia spp. weren't detected in our study. The identification of Ca. A. camelii in H. dromedari ticks was documented for the first time, suggesting a potential mode of transmission in camels. Notably, this study marks the first documentation of Rickettsia aeschlimannii with a prevalence of 6.06 % in the study area. Furthermore, we detected Coxiella burnetii in a prevalence of 8.08 % in Hyalomma ticks, indicating a potential risk of Q fever transmission. Molecular techniques results were confirmed by sequencing and phylogenetic analysis and provided valuable insights into the epidemiology of these pathogens, revealing their diversity. This study is vital in understanding tick-borne rickettsial pathogens' prevalence, distribution, and transmission dynamics in Upper Egypt. In conclusion, our findings emphasize the importance of continued research to enhance our understanding of the epidemiology and impact of these pathogens on both animal and human populations.

Host-pathogen associations revealed by genotyping of European strains of Anaplasma phagocytophilum to describe natural endemic cycles

BACKGROUND

The zoonotic intracellular alpha-proteobacterium Anaplasma phagocytophilum is a tick-transmitted pathogen. The associations between vertebrate reservoirs and vectors are described as wide-ranging, and it was previously shown that the pathogenicity of A. phagocytophilum differs depending on the combination of pathogen variant and infected host species. This leads to the question of whether there are variations in particular gene loci associated with different virulence. Therefore, this study aims at clarifying existing host-variant combinations and detecting possible reservoir hosts. To understand these interactions, a complex toolset for molecular epidemiology, phylogeny and network theory was applied.

METHODS

Sequences of up to four gene loci (msp4, msp2, groEL and 16S rRNA) were evaluated for different isolates from variable host species, including, for example, dogs, cattle and deer. Variant typing was conducted for each gene locus individually, and combinations of different gene loci were analysed to gain more detailed information about the genetic plasticity of A. phagocytophilum. Results were displayed as minimum spanning nets and correlation nets.

RESULTS

The highest diversity of variants for all gene loci was observed in roe deer. In cattle, a reduced number of variants for 16S rRNA [only 16S-20(W) and 16S-22(Y)] but multiple variants of msp4 and groEL were found. For dogs, two msp4 variants [m4-20 and m4-2(B/C)] were found to be linked to different variants of the other three gene loci, creating two main combinations of gene loci variants. Cattle are placed centrally in the minimum spanning net analyses, indicating a crucial role in the transmission cycles by possibly bridging the vector-wildlife cycle to infections of humans and domestic animals. The minimum spanning nets confirmed previously described epidemiological cycles of the bacterium in Europe, showing separation of variants originating from wildlife animals only and a set of variants shared by wild and domestic animals.

CONCLUSIONS

In this comprehensive study of 1280 sequences, we found a high number of gene variants only occurring in specific hosts. Additionally, different hosts show unique but also shared variant combinations. The use of our four gene loci expand the knowledge of host-pathogen interactions and may be a starting point to predict future spread and infection risks of A. phagocytophilum in Europe.

Prevalence of Anaplasma phagocytophilum, Borrelia burgdorferi sensu lato, Rickettsia spp. and Babesia spp. in cattle serum and questing ticks from Belgium

BACKGROUND

Anaplasmosis, borreliosis, rickettsiosis and babesiosis are tick-borne diseases of medical, veterinary and economic importance. In Belgium, little is known on the prevalence of these diseases in animals and previous screenings relate only to targeted geographic regions, clinical cases or a limited number of tested samples. We therefore performed the first nationwide seroprevalence study of Anaplasma spp., A. phagocytophilum, Borrelia spp., Rickettsia spp. and Babesia spp. in Belgian cattle. We also screened questing ticks for the aforementioned pathogens.

METHODS

ELISAs and IFATs were performed on a representative sample set of cattle sera stratified proportionally to the number of cattle herds per province. Questing ticks were collected in areas where the highest prevalence for the forenamed pathogens in cattle serum were observed. Ticks were analyzed by quantitative PCR for A. phagocytophilum (n = 783), B. burgdorferi sensu lato (n = 783) and Rickettsia spp. (n = 715) and by PCR for Babesia spp. (n = 358).

RESULTS

The ELISA screening for antibodies to Anaplasma spp. and Borrelia spp. in cattle sera showed an overall seroprevalence of 15.6% (53/339) and 12.9% (52/402), respectively. The IFAT screening for antibodies against A. phagocytophilum, Rickettsia spp. and Babesia spp. resulted in an overall seroprevalence of 34.2% (116/339), 31.2% (99/317) and 3.4% (14/412), respectively. At the provincial level, the provinces of Liege and Walloon Brabant harboured the highest seroprevalence of Anaplasma spp. (44.4% and 42.7% respectively) and A. phagocytophilum (55.6% and 71.4%). East Flanders and Luxembourg exhibited the highest seroprevalence of Borrelia spp. (32.4%) and Rickettsia spp. (54.8%) respectively. The province of Antwerp showed the highest seroprevalence of Babesia spp. (11%). The screening of field-collected ticks resulted in a prevalence of 13.8% for B. burgdorferi s.l., with B. afzelii and B. garinii being the most common genospecies (65.7% and 17.1%, respectively). Rickettsia spp. was detected in 7.1% of the tested ticks and the only identified species was R. helvetica. A low prevalence was found for A. phagocytophilum (0.5%) and no Babesia positive tick was detected.

CONCLUSIONS

The seroprevalence data in cattle indicate hot spots for tick-borne pathogens in specific provinces and highlights the importance of veterinary surveillance in anticipating the emergence of diseases among humans. The detection of all pathogens, with the exception of Babesia spp. in questing ticks, underlines the need of raising awareness among public and professionals on other tick-borne diseases along with lyme borreliosis.

A One Health Evaluation of the Surveillance Systems on Tick-Borne Diseases in the Netherlands, Spain and Italy

Simple Summary

Ixodid ticks and tick-borne diseases are expanding their geographical range, but surveillance activities vary among countries. We analysed the surveillance systems in place in the Netherlands, Spain and Italy, to identify ideal elements to monitor tick-borne diseases, by using a One Health evaluation protocol. We identified differences among the three surveillance systems, with the Dutch initiative showing a high level of transdisciplinary collaboration, good identification of the actors and engagement of the public in research and education. Measurable outcomes have been generated, such as the reduction in tick bites and the discovery of new pathogens and tick species. In Italy and Spain, surveillance systems are based on compulsory notification to health authorities; legislation seems relevant but law enforcement alongside the availability of economic resources is rather fragmented and limited to the most severe diseases. The non-scientific community is marginally considered and collaborations are limited to local initiatives. Research activities in both countries have mostly contributed to gaining knowledge on the distribution of tick species and the discovery of new pathogens. Although all TBD surveillance plans comply with the EU regulations, the initiatives characterised by trans-disciplinary collaboration may be more effective for the surveillance and prevention of tick-transmitted diseases.

Abstract

To identify ideal elements for the monitoring and prevention of tick-borne diseases (TBD), we analysed the surveillance systems in place in the Netherlands, Spain and Italy. We applied a semi-quantitative evaluation to identify outcomes and assess the degree of One Health implementation. Differences emerged in the surveillance initiatives, as well as the One Health scores. The Dutch surveillance is dominated by a high level of transdisciplinary and trans-sectoral collaboration, enabling communication and data sharing among actors. Different project-based monitoring, research and educational activities are centrally coordinated and the non-scientific community is actively involved. All this yielded measurable health outcomes. In Italy and Spain, TBD surveillance and reporting systems are based on compulsory notification. Law enforcement, alongside dedicated time and availability of economic resources, is fragmented and limited to the most severe health issues. Veterinary and human medicine are the most involved disciplines, with the first prevailing in some contexts. Stakeholders are marginally considered and collaborations limited to local initiatives. Research activities have mostly contributed to gaining knowledge on the distribution of tick vectors and discovery of new pathogens. Although all TBD surveillance plans comply with EU regulations, initiatives characterised by transdisciplinary collaboration may be more effective for the surveillance and prevention of TBD.

Detection and molecular identification of Anaplasma phagocytophilum and Babesia spp. infections in Hyalomma aegyptium ticks in Tunisia

Tortoises of the genus Testudo are the main hosts of Hyalomma aegyptium ticks. This species serves as a vector of several zoonotic pathogens. Therefore, the present study aimed to investigate the presence of four pathogens associated with H. aegyptium ticks obtained from tortoises from Tunisia. Conventional, multiplex and nested PCRs were used for Aanaplasma phagocytophilum, Ehrlichia canis, Coxiella burnetii and Babesia spp. screening. The molecular analyses revealed the presence of A. phagocytophilum and Babesia spp. None of the ticks, were infected by E. canis or C. burnetii species. Co-infection was detected in four ticks. As a conclusion, this is the first detection of A. phagocytophilum and Babesia spp. in H. aegyptium ticks collected from tortoises, in Tunisia. Thus, considering these results, the spur-thighed tortoise constitute a potential host of H. aegyptium which plays an important role in the transmission of pathogenic agents affecting both human and animals. In term of public health, a strict control and surveillance should be carried to reduce the circulation of such pathogens between different hosts.

Prevalence and Genotyping of Anaplasma phagocytophilum Strains from Wild Animals, European Bison (Bison bonasus) and Eurasian Moose (Alces alces) in Poland

Simple Summary

The populations of bison and moose, the largest wild ruminants in Poland, are growing every year. These animals return to Polish forests after many years of risk of extinction or, as in the case of European bison, are reintroduced step by step. Unfortunately, they are still rare and require close health surveillance and monitoring. One serious threat to their health and life is the bacterial parasite Anaplasma phagocytophilum. Moose and bison can also be sources of pathogenic bacteria for humans, which can be transferred through tick bites. In line with the World Health Organization (WHO) “OneHealth” program, indicating that animal health affects human health and vice versa, the following study examines the occurrence of Anaplasma phagocytophilum bacteria in European bison and Eurasian moose populations using molecular biology tools. Our results provide useful data regarding Anaplasma phagocytophilum that could be used in future strategies for the diagnosis and treatment of people and animals.

Abstract

Wild large ungulates, like European bison (Bison bonasus) and Eurasian moose (Alces alces), form an important part of the circulation of Anaplasma phagocytophilum, a Gram-negative, intracellular, tick-transmitted bacterium, in the natural environment. Bison and moose tissue samples were subjected to 16S rDNA, groEL and ankA partial gene marker amplification with specific primers using various variants of PCR. Out of 42 examined individuals, Anaplasma sp. were detected in 4/13 Eurasian moose (31%) and 7/29 European bison (24%). In addition, 12 groEL and 5 ankA partial gene positive samples were obtained from the examined animals. The phylogenetic analysis of the groEL partial gene classified samples from European bison to ecotype I, and samples from Eurasian moose to ecotype I and II; the analysis of the ankA partial gene assigned the samples to clusters I and IV. This study extends knowledge about A. phagocytophilum in wild large ungulates in Poland. This is the first report about the occurrence of Anaplasma sp. in one of the largest populations of free living European bison in the world. Our findings confirm that strains of A. phagocytophilum from Bison bonasus and Alces alces may constitute a natural reservoir of pathogenic HGA Anaplasma strains.

First report on molecular surveillance based on duplex detection of Anaplasma marginale and Theileria annulata in dairy cattle from Punjab, Pakistan

Theileriosis and anaplasmosis are important tick-borne hemoparasites of bovines. The first surveillance study aimed to assess the suitability of duplex PCR for simultaneous detection of Theileria annulata and Anaplasma marginale field infections in Jhang and Rawalpindi districts of Punjab, Pakistan. Cattle blood samples (n = 480) were collected from selected union councils of all tehsils using a multistage sampling technique. The sampling unit consisted of asymptomatic cattle belonging to either age, sex, and breed. Epidemiological data related to host, area, management, and season were collected using a questionnaire. Based on duplex PCR, the overall prevalence of the two concurrent tick-borne pathogens was 19.79% (95/480). Chi-square analysis indicated that age, breed, tick infestation, history of tick-borne diseases, frequency of acaricidial application, and season were significantly associated with tick-borne pathogens. Phylogenetic analysis of A. marginale and T. annulata isolates based on msp1β and cytochrome b genes, respectively, revealed that nucleotide sequences acquired from these two pathogens are novel, grouped separately from different countries. All our A. marginale isolates showed 88.2 to 80.5% similarity with isolates from Egypt, Israel, Mexico, and lesser homology with South African isolates. Similarly, the phylogenetic tree based on cytochrome b partial sequences of T. annulata revealed that our sequences are closer to those from India and Iran. Based on this first study on concomitant detection of tick-borne pathogens, it can be concluded that mixed infections are endemic in the study districts and mPCR is suitable for detecting concurrent field infections. Simultaneous infections should be considered while performing surveillance and chemotherapeutic trials for better prevention and control of tick-borne diseases.

First detection of Anaplasma phagocytophilum and Babesia divergens and high infection rates of Anaplasma marginale and Babesia bigemina in cattle in extensive grazing systems of Central Spain

Bovine vector-borne diseases have a considerable economic impact worldwide and affect health of humans and animals. However, different aspects of their epidemiology and their pathogenesis remain unclear. Despite the frequent description of clinical cases reported by practitioners attending cattle from Madrid, Central Spain, molecular prevalence of Anaplasma spp. and Babesia spp. has not been described. The aim of this study was to assess the positivity rate of A. phagocytophilum, A. marginale, A. centrale, B. bigemina and B. divergens in livestock of this area and to evaluate the existence of associations between these pathogens and haematological, biochemical and epidemiological data. Babesia divergens and A. phagocytophilum were detected for the first time in cattle from Madrid. Their positivity percentages were low (2.2% ± 1.4% and 1.8% ± 1.2%, respectively), but this description is of special interest, as these agents are potentially zoonotic. Both agents were found in areas of higher altitude and relative humidity and lower temperature. The detection of ticks in livestock during the moment of sampling was confirmed as a risk factor for these infections. Anaplasma marginale showed the highest molecular infection rate (30% ± 4.1%) in this study, followed by B. bigemina (21.9% ± 3.7%). Higher positivity rates of A. marginale and B. bigemina were found in the areas of mountain climate and warm-summer continental Mediterranean climate. The use of ectoparasiticide treatment was found as a risk factor for infection by A. marginale and B. bigemina. This finding could lead to reconsider the ectoparasiticide protocols that are used nowadays. Grazing on pastures with domestic or wild ruminants and the presence of wild carnivores were associated with higher rates of infection by these four agents and coinfections were frequently found.

Seasonality and Geography Have a Greater Influence than the Use of Chlorine-Based Cleaning Agents on the Microbiota of Bulk Tank Raw Milk

Cleaning of the production environment is vital to ensure the safety and quality of dairy products. Although cleaning with chlorine-based agents is widely adopted, it has been associated with detrimental effects on milk quality and safety, which has garnered increasing interest in chlorine-free cleaning. However, the influence of these methods on the milk microbiota is not well documented. This study investigated the factors that influence the raw milk microbiota, with a focus on the differences when chlorine-based and chlorine-free cleaning of milking equipment are used. Bulk tank raw milk was sampled during three sampling months (April, August, and November), from farms across Ireland selected to capture the use of different cleaning methods, i.e., exclusively chlorine-based (n = 51) and chlorine-free cleaning (n = 92) and farms that used chlorine-free agents for the bulk tank and chlorine-based cleaning agents for the rest of the equipment (n = 28). Shotgun metagenomic analysis revealed the significant influence of seasonal and geographic factors on the bulk tank milk microbiota, indicated by differences in diversity, taxonomic composition, and functional characteristics. Taxonomic and functional profiles of samples collected in November clustered separately from those of samples collected in other months. In contrast, cleaning methods only accounted for 1% of the variation in the bulk tank milk bacterial community, and samples collected from farms using chlorine-based versus chlorine-free cleaning did not differ significantly, suggesting that the chlorine-free approaches used did not negatively impact microbiological quality. This study shows the value of shotgun metagenomics in advancing our knowledge of the raw milk microbiota. IMPORTANCE The microbiota of raw milk is affected by many factors that can control or promote the introduction of undesirable microorganisms. Chlorine-based cleaning agents have been commonly used due to their effectiveness in controlling undesirable microorganisms, but they have been associated with the formation of chlorine residues that are detrimental to product quality and may impact consumer health. Chlorine-free alternatives have been recommended in some countries, but the influence of cleaning agents on the milk microbiota is unknown. Here, we investigated the influence of cleaning methods and other factors on bulk tank raw milk. Results showed that season and location had a greater influence on the milk microbiota than the cleaning agents used. Indeed, the similar microbiota compositions of raw milk from farms that used chlorine-based and those that used chlorine-free cleaning methods supports the further use of chlorine-free cleaning agents in dairy production.

Anaplasma phagocytophilum and Anaplasma ovis-Emerging Pathogens in the German Sheep Population

Knowledge on the occurrence of pathogenic tick-borne bacteria Anaplasma phagocytophilum and Anaplasma ovis is scarce in sheep from Germany. In 2020, owners from five flocks reported ill thrift lambs and ewes with tick infestation. Out of 67 affected sheep, 55 animals were clinically examined and hematological values, blood chemistry and fecal examinations were performed to investigate the underlying disease causes. Serological tests (cELISA, IFAT) and qPCR were applied to all affected sheep to rule out A. phagocytophilum and A. ovis as a differential diagnosis. Ticks were collected from selected pastures and tested by qPCR. Most animals (n = 43) suffered from selenium deficiency and endoparasites were detected in each flock. Anaplasma spp. antibodies were determined in 59% of examined sheep. Seventeen animals tested positive for A. phagocytophilum by qPCR from all flocks and A. phagocytophilum was also detected in eight pools of Ixodes ricinus. Anaplasma phagocytophilum isolates from sheep and ticks were genotyped using three genes (16S rRNA, msp4 and groEL). Anaplasma ovis DNA was identified in six animals from one flock. Clinical, hematological and biochemical changes were not significantly associated with Anaplasma spp. infection. The 16S rRNA analysis revealed known variants of A. phagocytophilum, whereas the msp4 and groEL showed new genotypes. Further investigations are necessary to evaluate the dissemination and health impact of both pathogens in the German sheep population particularly in case of comorbidities.

Seroprevalence and Risk Factors of Anaplasma spp. in German Small Ruminant Flocks

Knowledge about the distribution of Anaplasma spp. in small ruminants from Germany is limited. Therefore, serum samples were examined from 71 small ruminant flocks (2731 sheep, 447 goats) located in the five German federal states: Schleswig-Holstein (SH), Lower Saxony (LS), North Rhine-Westphalia (NRW), Baden-Wuerttemberg (BW) and Bavaria (BAV). Antibodies to Anaplasma spp. were determined by a cELISA based on the MSP5 antigen. A risk factor analysis at animal and flock level was also performed. Antibodies to Anaplasma spp. were detected in 70/71 flocks without significant difference in the intra-flock prevalence (IFP) between the federal states. The mean antibody levels from sheep were significantly lower in northern Germany (LS, SH) compared to west (NRW) and south Germany (BW, BAV). Sheep had a 2.5-fold higher risk of being seropositive than goats. Females and older animals (>2 years) were more likely to have antibodies to Anaplasma spp. in one third and one quarter of cases, respectively. Flocks used for landscape conservation had a five times higher risk of acquiring an IFP greater than 20%. Cats and dogs on the farms increased the probability for small ruminant flocks to have an IFP of above 20% 10-fold and 166-fold, respectively. Further studies are necessary to assess the impact of Anaplasma species on the health of small ruminants in Germany.

Genetic diversity of Anaplasma bacteria: Twenty years later

The genus Anaplasma (family Anaplasmataceae, order Rickettsiales) includes obligate intracellular alphaproteobacteria that multiply within membrane-bound vacuoles and are transmitted by Ixodidae ticks to vertebrate hosts. Since the last reclassification of Anaplasmataceae twenty years ago, two new Anaplasma species have been identified. To date, the genus includes eight Anaplasma species (A. phagocytophilum, A. marginale, A. centrale, A. ovis, A. bovis, A. platys, A. odocoilei, and A. capra) and a large number of unclassified genovariants that cannot be assigned to known species. Members of the genus can cause infection in humans and a wide range of domestic animals with different degrees of severity. Long-term persistence which, in some cases, is manifested as cyclic bacteremia has been demonstrated for several Anaplasma species. Zoonotic potential has been shown for A. phagocytophilum, the agent of human granulocytic anaplasmosis, and for some other Anaplasma spp. that suggests a broader medical relevance of this genus. Genetic diversity of Anaplasma spp. has been intensively studied in recent years, and it has been shown that some Anaplasma spp. can be considered as a complex of genetically distinct lineages differing by geography, vectors, and host tropism. The aim of this review was to summarize the current knowledge concerning the natural history, pathogenic properties, and genetic diversity of Anaplasma spp. and some unclassified genovariants with particular attention to their genetic characteristics. The high genetic variability of Anaplasma spp. prompted us to conduct a detailed phylogenetic analysis for different Anaplasma species and unclassified genovariants, which were included in this review. The genotyping of unclassified genovariants has led to the identification of at least four distinct clades that might be considered in future as new candidate species.

Enlisting the Ixodes scapularis Embryonic ISE6 Cell Line to Investigate the Neuronal Basis of Tick-Pathogen Interactions

Neuropeptides are small signaling molecules expressed in the tick central nervous system, i.e., the synganglion. The neuronal-like Ixodes scapularis embryonic cell line, ISE6, is an effective tool frequently used for examining tick–pathogen interactions. We detected 37 neuropeptide transcripts in the I. scapularis ISE6 cell line using in silico methods, and six of these neuropeptide genes were used for experimental validation. Among these six neuropeptide genes, the tachykinin-related peptide (TRP) of ISE6 cells varied in transcript expression depending on the infection strain of the tick-borne pathogen, Anaplasma phagocytophilum. The immunocytochemistry of TRP revealed cytoplasmic expression in a prominent ISE6 cell subpopulation. The presence of TRP was also confirmed in A. phagocytophilum-infected ISE6 cells. The in situ hybridization and immunohistochemistry of TRP of I. scapularis synganglion revealed expression in distinct neuronal cells. In addition, TRP immunoreaction was detected in axons exiting the synganglion via peripheral nerves as well as in hemal nerve-associated lateral segmental organs. The characterization of a complete Ixodes neuropeptidome in ISE6 cells may serve as an effective in vitro tool to study how tick-borne pathogens interact with synganglion components that are vital to tick physiology. Therefore, our current study is a potential stepping stone for in vivo experiments to further examine the neuronal basis of tick–pathogen interactions.

First reports of indigenous lethal infection with Anaplasma marginale, Anaplasma bovis and Theileria orientalis in Croatian cattle

Anaplasmosis and theileriosis are important diseases with great economic impact that affect the cattle industry worldwide. In this study, we describe the first molecularly confirmed clinical cases of anaplasmosis caused by Anaplasma marginale and of a concurrent infection with A. bovis and Theileria orientalis in Croatian cattle. Clinical signs of A. marginale-infected cows included fever, lethargy, dark urine, as well as icteric and reddish mucous membranes. Postmortem examination revealed icterus, urinary bladder filled with dark urine and splenomegaly. A marginale was observed within erythrocytes on Giemsa-stained spleen imprints. Three affected cows were successfully treated with oxytetracycline, after which no new deaths occurred in the herd. Three cows in a different herd died suddenly and were found to be concurrently infected with A. bovis and T. orientalis. Postmortem examination revealed generalized icterus and urinary bladder filled with dark urine. These cases of A. marginale, A. bovis and T. orientalis infection show that bovine anaplasmosis and theileriosis are present within Croatian cattle and should be included in differential diagnostic protocols.

Co-infection, reinfection and superinfection with Anaplasma phagocytophilum strains in a cattle herd based on ankA gene and multilocus sequence typing

BACKGROUND

Anaplasma phagocytophilum is a Gram-negative obligate intracellular bacterium that replicates in neutrophil granulocytes. It is transmitted by ticks of the Ixodes ricinus complex and causes febrile illness in humans and animals. We used multilocus sequence typing (MLST) and ankA gene-based typing to study the molecular epidemiology of the A. phagocytophilum strains circulating in a German cattle herd over one pasture season. The aim was to investigate whether co-infection with two distinct variants, reinfection with the same and/or superinfection by a different strain occurred during one pasture season. Eight genetic loci were sequenced in 47 PCR-positive samples from 15 animals.

RESULTS

Five different sequence types (ST) and four ankA alleles were detected in the cattle herd. Three different ST caused clinically overt tick-borne fever in primary infected animals. The concordance between ST and ankA allele was 100%. Therefore, the housekeeping genes used for MLST and the highly variable ankA gene were concatenated to increase resolution. Co-infection could be proven because samples of chronologically close collection dates were included. Co-infecting A. phagocytophilum strains differed by 14 to 18 single nucleotide polymorphisms (SNPs). Most superinfecting variants varied by 14 SNPs from the previous strain and appeared in median after a free interval of 31 days. Thus, it is unlikely that superinfecting strains arose by in-animal evolution. Immunity against re- or superinfection was assumed because the cattle developed clinical signs only during primary infection.

CONCLUSIONS

The tick-pathogen-vertebrate host interaction is probably much more complex than previously thought taking into account the frequently occurring events of co-infection, reinfection and superinfection. This complex situation could not be easily simulated in an experimental infection and underlines the value of field studies.

Genetic characterization of Anaplasma phagocytophilum strains from goats (Capra aegagrus hircus) and water buffalo (Bubalus bubalis) by 16S rRNA gene, ankA gene and multilocus sequence typing

Anaplasma phagocytophilum is a Gram-negative obligate intracellular bacterium that replicates in neutrophil granulocytes. It is transmitted by ticks and causes tick-borne fever in domestic ruminants such as sheep, cattle and goats. However, in contrast to sheep and cattle little is known about the clinical course of infection in goats. We report here on three cases of symptomatic infection with A. phagocytophilum in two goats (Capra aegagrus hircus) and one water buffalo (Bubalus bubalis). The animals showed symptoms and laboratory findings similar to sheep and cattle. To our knowledge, this is the first report on the symptomatic infection of water buffalos with A. phagocytophilum. The infecting strains were genetically characterized by 16S rRNA gene, ankA gene and multilocus sequence typing (MLST). Four other strains from asymptomatically infected goats were also included. The ankA sequences from five goats were part of the formerly described ankA gene clusters I and IV that are known to contain A. phagocytophilum strains from sheep and cattle. However, the sequences from one goat and from the water buffalo belonged to ankA gene cluster II that was formerly described to be restricted to roe deer. A similar observation was made for MLST as three goats clustered with sequences from sheep and cattle, whereas three other goats and the water buffalo were found to be part of the roe deer cluster. However, since most of the strains from sheep and cattle were distinct from the roe deer strains, roe deer might not represent major reservoir hosts for tick-borne fever in domestic ruminants. When differing parts of the 16S rRNA gene were used for typing the results were conflicting. This shows that the use of a standardized typing method such as MLST is highly desirable to generate easily comparable results.

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.

Simultaneous infection of cattle with different Anaplasma phagocytophilum variants

Anaplasma phagocytophilum is a tick-transmitted Gram-negative obligate intracellular bacterium that replicates in neutrophil granulocytes. It causes tick-borne fever in cattle and sheep. We report here the case of a 5-year-old cow from Germany with clinically overt granulocytic anaplasmosis presenting with fever, lower limb oedema and drop in milk-yield. The herd encompassed 10 animals, 8 other animals showed subclinical infection. The strains from the 9 A. phagocytophilum positive cows were molecularly characterized using ankA gene-based and multilocus sequence typing (MLST). Seven of 9 (78%) animals were infected simultaneously with different ankA variants belonging to ankA clusters I and IV. MLST analysis also revealed the presence of multiple strain types. This could be due to co-transmission or superinfection. Hosts harboring diverse A. phagocytophilum strains might enable the emergence of new ankA variants and/or MLST sequence types via bacterial recombination.

Co-circulation of different A. phagocytophilum variants within cattle herds and possible reservoir role for cattle

Background

Anaplasma phagocytophilum is a zoonotic tick-borne intracellular alpha-proteobacterium causing tick-borne fever, which leads to significant economic losses in domestic ruminants in Europe. Its epidemiological cycles are complex and reservoir host species of bovine strains have not yet been identified. Given that little genetic information is available on strains circulating within a defined bovine environment, our objective was to assess the genetic diversity of A. phagocytophilum obtained from the same farms over time.

Methods

Blood samplings were performed several times in two European herds. In the French herd, 169 EDTA-blood samples were obtained from 115 cows (32 were sampled two to four times). In the German herd, 20 cows were sampled six times (120 EDTA-blood samples). The presence of A. phagocytophilum DNA was assessed using a qPCR targeting msp2. The positive DNA samples underwent MLST at nine genetic markers (typA, ctrA, msp4, pleD, recG, polA, groEL, gyrA, and ankA). For each locus, sequences were aligned with available bacterial sequences derived from cattle, horse, dog, and roe deer hosts, and concatenated neighbor joining trees were constructed using three to six loci.

Results

Around 20% (57/289) of samples were positive. Forty positive samples from 23 French and six German cows (11 of them being positive at two time points) were sequenced. Six loci (typA, ctrA, msp4, pleD, recG, and polA) allowed to build concatenated phylogenetic trees, which led to two distinct groups of bovine variants in the French herd (hereafter called A and B), whereas only group A was detected in the German herd. In 42% of French samples, double chromatogram peaks were encountered in up to four loci. Eleven cows were found infected three weeks to 17 months after first sampling and harboured a new variant belonging to one or the other group.

Conclusions

Our results demonstrate the occurrence of two major bovine strain groups and the simultaneous infection of single cows by more than one A. phagocytophilum strain. This challenges the role of cattle as reservoirs for A. phagocytophilum. This role may be facilitated via long-term bacterial persistence in individual cows and active circulation at the herd scale.

Electronic supplementary material

The online version of this article (10.1186/s13071-018-2661-7) contains supplementary material, which is available to authorized users.