Genotypic variation and mixtures of Lyme Borrelia in Ixodes ticks from North America and Europe

Ticks and tick-borne pathogens in selected abattoirs and a slaughter slab in Kumasi, Ghana

BACKGROUND

Ticks are vectors of pathogens that affect the health of animals and humans. With the constant trade of livestock across borders, there is the risk of new tick species invasion accompanied by the spread of infectious tick-borne pathogens.

AIM

This study sought to determine the diversity of tick species within abattoirs and a slaughter slab as well as identify the pathogens carried by these ticks.

METHODS

The ticks were collected from slaughtered cattle, identified and screened for pathogens using PCR and sequencing.

RESULTS

A total of 371 ticks were collected from slaughtered cattle across the three sampling sites: Kumasi abattoir (288, 77.63%), Akwatia Line slaughter slab (52, 14.02%) and Suame abattoir (31, 8.35%). The predominant species was Amblyomma variegatum (85.44%) with Rhipicephalus sanguineus (s.l.) (0.27%) as the least occurring species. Total nucleic acid from the tick pools was screened for pathogens based on the nucleoprotein gene region in the S segment of the Crimean-Congo haemorrhagic fever virus (CCHFV) genome, the 295-bp fragment of the transposase gene of the Coxiella burnetii IS1111a element, the 560 bp segment of the ssrRNA gene of Babesia and Theileria, the 345 bp fragment of the Ehrlichia genus 16SrRNA gene and the rOmpA gene (OmpA) of Rickettsia. From the 52 tick pools screened, 40 (76.92%) were found positive for pathogen DNA. The pathogens identified were Rickettsia africae (69.23%), Rickettsia aeschlimannii (7.69%), C. burnetii (5.77%), uncultured Ehrlichia sp. (5.77%), Candidatus Midichloria mitochondrii (3.85%) and CCHFV (3.85%). A significant association was observed among A. variegatum, Hyalomma rufipes, Hyalomma truncatum and occurring tick-borne pathogens R. africae, R. aeschlimannii and uncultured Ehrlichia sp. (p < 0.001).

CONCLUSION

The findings show the occurrence of zoonotic pathogens, suggesting an increased risk of infections among the abattoir workers. There is a need to adopt control measures within the abattoirs to prevent pathogen spread.

How Do I Approach the Evaluation and Treatment of Early Lyme Disease?

AbstractThe incidence and geographic spread of Lyme disease are increasing, and more than 476,000 new cases a year are estimated to occur in the United States. Therefore, many clinicians in North America will need to consider how to approach a patient with a concern for Lyme disease. This Curbside Consult addresses common clinical considerations, including discussion of signs of early Lyme disease, available laboratory tests, when to treat and with which antibiotics.

Risk factors affecting the feeding site predilection of ticks on cattle in Ghana

Ticks are important disease vectors affecting animal health and causing substantial economic loss, especially in the tropics and subtropics. To examine the tick burden of cattle and associated risk factors for tick infestation, ticks were collected from 388 cattle within five regions in Ghana. Most of the cattle were males (50.3%) and generally older than 3 years (65%). Of the animals sampled, 2187 ticks were collected with a mean tick burden of 5.6 ticks per cattle, and the average tick burden on the udder/scrotum being significantly higher than in the anal region (Generalized Linear Mix Model [GLMM], p = 0.01197). The tick species identified were predominantly Amblyomma variegatum (42.6%) and Hyalomma rufipes (26.2%). High proportions of cattle examined were found to have A. variegatum infesting the udder/scrotum. Furthermore, H. rufipes infested mostly the anal region compared to other examined body parts (OR 14.8, 95% CI 8.6-25.4, p < 0.001). Using the GLMM, tick abundance was found to be significantly higher in cattle older than 3 years. The tick burden in the udder/scrotum was higher than that from the chest and leg/thigh of the cattle (GLMM, p < 0.05). The tick burden at the anal region was also significantly higher than the leg/thigh and chest. This study indicates that the preferred attachment sites of ticks on cattle are species-dependent and effective treatment with acaricides should take into consideration the udder/scrotum and anal regions as well as prioritizing older cattle.

Molecular identification of Crimean-Congo haemorrhagic fever virus in Hyalomma rufipes and Amblyomma variegatum in the Upper East Region of Ghana

Sampled ticks were screened for Crimean-Congo haemorrhagic fever virus (CCHFV) using an assay that targets the nucleoprotein gene region of the S segment, a conserved region of the CCHFV genome. Minimum infection rates of 0.34% and 0.10% were obtained when testing pools of Hyalomma rufipes and Amblyomma variegatum, respectively. Next-generation sequencing and phylogenetic analysis showed that the S and L segments of the CCHFV isolate clustered with those of similar isolates of genotype III. However, analysis of the M segment showed that reassortment had occurred, causing this segment to cluster with those of isolates of genotype I, providing the first evidence of such an occurrence in Ghana.

First Molecular Identification of Rickettsia aeschlimannii and Rickettsia africae in Ticks from Ghana

The threats from vector-borne pathogens transmitted by ticks place people (including deployed troops) at increased risk for infection, frequently contributing to undifferentiated febrile illness syndromes. Wild and domesticated animals are critical to the transmission cycle of many tick-borne diseases. Livestock can be infected by ticks, and serve as hosts to tick-borne diseases such as rickettsiosis. Thus, it is necessary to identify the tick species and determine their potential to transmit pathogens. A total of 1,493 adult ticks from three genera-Amblyomma, Hyalomma, and Rhipicephalus-were identified using available morphological keys and were pooled (n = 541) by sex and species. Rickettsia species were detected in 308 of 541 (56.9%) pools by genus-specific quantitative polymerase chain reaction assay (Rick17b). Furthermore, sequencing of the outer membrane protein A and B genes (ompA and ompB) of random samples of Rickettsia-positive samples led to the identification of Rickettsia aeschlimannii and Rickettsia africae with most R. africae DNA (80.2%) detected in pools of Amblyomma variegatum. We report the first molecular detection and identification of the rickettsial pathogens R. africae and R. aeschlimannii in ticks from Ghana. Our findings suggest there is a need to use control measures to prevent infections from occurring among human populations in endemic areas in Ghana. This study underscores the importance of determining which vector-borne pathogens are in circulation in Ghana. Further clinical and prevalence studies are needed to understand more comprehensively the clinical impact of these rickettsial pathogens contributing to human disease and morbidity in Ghana.

Tick-borne pathogens of zoonotic and veterinary importance in cattle ticks in Ghana

Ticks are important vectors involved in the transmission of pathogens of zoonotic and veterinary importance. In this study, ticks were collected from cattle in Navrongo, Kintampo, and Kumasi and screened for pathogen DNA using PCR and Sanger sequencing. A total of 454 ticks were collected, morphologically identified and confirmed using primers that target the 660-bp segment of the mitochondrial COI gene. The predominant tick species was Amblyomma variegatum (70.26%). DNA was extracted from 85 tick pools and screened for the presence of Rickettsia DNA based on the 639 bp of the outer membrane protein A (ompA) gene, Ehrlichia/Anaplasma DNA based on the 345 bp fragment of the 16SrRNA gene and Babesia/ Theileria DNA based on the 560 bp fragment of the ssrRNA gene. From the 85 tick pools, the DNA of pathogens detected were Rickettsia africae (36.47%), Rickettsia aeschlimannii (16.47%), Ehrlichia canis (2.35%), Babesia occultans (1.18%), Theileria velifera (1.18%) and a symbiont Candidatus Midichloria mitochondrii (8.24%). This study reports the first molecular detection of Candidatus Cryptoplasma californiense (1.18%) in Ghana. Coinfections were recorded in 8.24% of the tick pools. The findings of this study highlight the importance of tick species in Ghana and the need to adopt effective control measures to prevent pathogen spread.

First record of Babesia and Theileria parasites in ticks from Kassena-Nankana, Ghana

Ticks are efficient vectors for transmitting pathogens that negatively affect livestock production and pose a risk to public health. In this study, Babesia and Theileria species were identified in ticks collected from cattle, sheep and goats from the Kassena-Nankana Districts of Ghana between February and December 2020. A total of 1550 ticks were collected, morphologically identified, pooled and screened for pathogens using primers that amplify a 560 bp fragment of the ssrRNA gene and Sanger sequencing. Amblyomma variegatum (62.98%) was the predominant tick species. From the 491 tick pools screened, 12/15 (2.44%) positive pools were successfully sequenced. The pathogen DNA identified were Theileria ovis in eight (15.38%) pools of Rhipicephalus evertsi evertsi, Theileria velifera in two (0.78%) pools of A. variegatum and Babesia occultans and Babesia sp. Xinjiang in one (1.72%) pool each of Hyalomma truncatum. It was further observed that T. ovis occurred in ticks collected from only sheep (p < 0.001) which were females (p = 0.023) and < =1 year old (p = 0.040). This study reports the first identification of these pathogens in ticks within Kassena-Nankana. With the constant trade of livestock, there is a need for effective tick control measures to prevent infection spread.

Lyme borreliosis diagnosis: state of the art of improvements and innovations

With almost 700 000 estimated cases each year in the United States and Europe, Lyme borreliosis (LB), also called Lyme disease, is the most common tick-borne illness in the world. Transmitted by ticks of the genus Ixodes and caused by bacteria Borrelia burgdorferi sensu lato, LB occurs with various symptoms, such as erythema migrans, which is characteristic, whereas others involve blurred clinical features such as fatigue, headaches, arthralgia, and myalgia. The diagnosis of Lyme borreliosis, based on a standard two-tiered serology, is the subject of many debates and controversies, since it relies on an indirect approach which suffers from a low sensitivity depending on the stage of the disease. Above all, early detection of the disease raises some issues. Inappropriate diagnosis of Lyme borreliosis leads to therapeutic wandering, inducing potential chronic infection with a strong antibody response that fails to clear the infection. Early and proper detection of Lyme disease is essential to propose an adequate treatment to patients and avoid the persistence of the pathogen. This review presents the available tests, with an emphasis on the improvements of the current diagnosis, the innovative methods and ideas which, ultimately, will allow more precise detection of LB.

Occurrence of Rickettsia spp. and Coxiella burnetii in ixodid ticks in Kassena-Nankana, Ghana

Ticks are arthropods of veterinary and medical importance which spread zoonotic pathogens that link animal and human health. In this study, ticks were collected from 448 livestock between February and December 2020 in the Kassena-Nankana Districts of Ghana and screened for the presence of zoonotic pathogens DNA using PCR and sequencing approaches. In total, 1550 ticks were collected and morphologically identified. Three tick genera were identified with Amblyomma variegatum (63%) as the predominant tick species collected. DNA was extracted from 491 tick pools and screened for the presence of DNA of Rickettsia spp. based on the 115 bp fragment of the 17 kDa surface protein and 639 bp of the Outer membrane protein A (ompA) gene and the 295 bp fragment of the transposase gene of Coxiella burnetii IS1111a element. From the 491 pools screened, the DNA of Rickettsia spp. and C. burnetii was detected in 56.8 and 3.7%, respectively. Coinfections were identified in 2.4% of the tick pools. Characterization of the Rickettsia spp. in this study based on the ompA gene showed that the DNA of Rickettsia africae and Rickettsia aeschlimannii accounted for 39.7 and 14.7%, respectively, and were 100% similar to sequences in GenBank. Most R. africae and C. burnetii infections occurred in ticks collected in the wet season, whereas R. aeschlimannii occurred mostly in the dry season. These pathogens are potential public health threats, thus there is a need to implement control measures to reduce the risk of infections in vulnerable populations.

First record of Rhipicephalus (Boophilus) microplus in Ghana, a potential risk to livestock production

Ticks are a public health threat due to their tendency to spread pathogens that affect humans and animals. With reports of Rhipicephalus (Boophilus) microplus invasion in neighbouring countries, there is the risk of this species invading Ghana through livestock trade. Previous identification of tick species in Ghana has been based on morphological identification, which can be ineffective, especially with damaged tick specimens or engorged nymphs. This study focused on the Kassena-Nankana District, which serves as a trade route for cattle into Ghana, to determine the presence of R. microplus. Three genera of ticks were identified as Amblyomma (70.9%), Hyalomma (21.3%) and Rhipicephalus (7.8%). The engorged nymphs that could not be identified morphologically were analyzed using primers that target the mitochondrial 16S rRNA gene. This study reports the first record of R. (B.) microplus in Ghana. Furthermore, R. microplus constituted 54.8% of the Boophilus species collected in this study. This finding is an addition to the diverse tick species previously collected in Ghana, most of which are of veterinary and public health importance. With reports of acaricide resistance in R. microplus and its role in spreading infectious pathogens, the detection of this species in Ghana cannot be overlooked. Nationwide surveillance will be essential to ascertain its distribution, its effects on cattle production, and the control measures adopted.

Molecular survey of Anaplasma and Ehrlichia species in livestock ticks from Kassena-Nankana, Ghana; with a first report of Anaplasma capra and Ehrlichia minasensis

Tick-borne pathogens harm livestock production and pose a significant risk to public health. To combat these effects, it is necessary to identify the circulating pathogens to create effective control measures. This study identified Anaplasma and Ehrlichia species in ticks collected from livestock in the Kassena-Nankana Districts between February 2020 and December 2020. A total of 1550 ticks were collected from cattle, sheep and goats. The ticks were morphologically identified, pooled and screened for pathogens using primers that amplify a 345 bp fragment of the 16SrRNA gene and Sanger sequencing. The predominant tick species collected was Amblyomma variegatum (62.98%). From the 491 tick pools screened, 34 (6.92%) were positive for Ehrlichia and Anaplasma. The pathogens identified were Ehrlichia canis (4.28%), Ehrlichia minasensis (1.63%), Anaplasma capra (0.81%) and Anaplasma marginale (0.20%). This study reports the first molecular identification of the above-mentioned Ehrlichia and Anaplasma species in ticks from Ghana. With the association of human infections with the zoonotic pathogen A. capra, livestock owners are at risk of infections, calling for the development of effective control measures.

Large-Scale Sequencing of Borreliaceae for the Construction of Pan-Genomic-Based Diagnostics

The acceleration of climate change has been associated with an alarming increase in the prevalence and geographic range of tick-borne diseases (TBD), many of which have severe and long-lasting effects-particularly when treatment is delayed principally due to inadequate diagnostics and lack of physician suspicion. Moreover, there is a paucity of treatment options for many TBDs that are complicated by diagnostic limitations for correctly identifying the offending pathogens. This review will focus on the biology, disease pathology, and detection methodologies used for the Borreliaceae family which includes the Lyme disease agent Borreliella burgdorferi. Previous work revealed that Borreliaceae genomes differ from most bacteria in that they are composed of large numbers of replicons, both linear and circular, with the main chromosome being the linear with telomeric-like termini. While these findings are novel, additional gene-specific analyses of each class of these multiple replicons are needed to better understand their respective roles in metabolism and pathogenesis of these enigmatic spirochetes. Historically, such studies were challenging due to a dearth of both analytic tools and a sufficient number of high-fidelity genomes among the various taxa within this family as a whole to provide for discriminative and functional genomic studies. Recent advances in long-read whole-genome sequencing, comparative genomics, and machine-learning have provided the tools to better understand the fundamental biology and phylogeny of these genomically-complex pathogens while also providing the data for the development of improved diagnostics and therapeutics.

Monitoring Risk: Tick and Borrelia burgdorferi Public Participatory Surveillance in the Canadian Maritimes, 2012-2020

Ticks are vectors of many diseases, including Lyme disease (Ld). Lyme disease is an emerging disease in Canada caused by infection with the Lyme borreliosis (Lb) members of the Borrelia genus of spirochaete bacteria, of which Borrelia&nbsp;burgdorferi is regionally the most prevalent. The primary tick vector in central and eastern Canada, Ixodes scapularis, is increasing in numbers and in the geographical extent of established populations. This study documents the distribution of ticks recovered by passive surveillance, and their B.&nbsp;burgdorferi infection prevalence, in three Canadian Maritime provinces from 2012-2020. These regions represent areas in which tick populations are widely established, establishing, and considered non-established. Using a community science approach by partnering with veterinarians and members of the public, we collected over 7000 ticks from the 3 provinces. The three species found most often on companion animals and humans were I. scapularis (76.9%), Ixodes cookei (10.4%) and Dermacentor variabilis (8.9%). The most common hosts were dogs (60.5%), cats (16.8%) and humans (17.6%). As is typical of passive surveillance tick collections, the majority of ticks recovered were adult females; for I. scapularis 90.2%, 5.3%, 3.9% and 0.6% of the total of 5630 ticks recovered for this species were adult females, adult males, nymphs and larvae, respectively. The majority of B. burgdorferi-infected ticks were I. scapularis, as expected. Borrelia infection prevalence in I scapularis was higher in Nova Scotia (20.9%), the province with the most endemic regions, than New Brunswick (14.1%) and Prince Edward Island (9.1%), provinces thought to have established and non-established tick populations, respectively. The province-wide Borrelia infection prevalence generally increased in these latter tow provinces over the course of the study. The host did not have a significant effect on B. burgdorferi infection prevalence; I. scapularis ticks from dogs, cats, humans was, 13.3% (n = 3622), 15.6% (n = 817), 17.9% (n = 730), respectively. No I. scapularis larvae were found infected (n = 33) but B. burgdorferi was detected in 14.8% of both adults (n = 5140) and nymphs (n = 215). The incidence of B. burgdorferi infection also did not differ by engorgement status 15.0% (n = 367), 15.1% (n = 3101) and 14.4% (n = 1958) of non-engorged, engorged and highly engorged ticks, respectively, were infected. In New Brunswick, at the advancing front of tick population establishment, the province-wide infection percentages generally increased over the nine-year study period and all health district regions showed increased tick recoveries and a trend of increased percentages of Borrelia-infected ticks over the course of the study. Within New Brunswick, tick recoveries but not Borrelia infection prevalence were significantly different from endemic and non-endemic regions, suggesting cryptic endemic regions existed prior to their designation as a risk area. Over the 9 years of the study, tick recoveries increased in New Brunswick, the primary study region, and I. scapularis recoveries spread northwards and along the coast, most but not all new sites of recoveries were predicted by climate-based models, indicating that ongoing tick surveillance is necessary to accurately detect all areas of risk. Comparison of tick recoveries and public health risk areas indicates a lag in identification of risk areas. Accurate and timely information on tick distribution and the incidence of Borrelia and other infections are essential for keeping the public informed of risk and to support disease prevention behaviors.

Recent Progress in Lyme Disease and Remaining Challenges

Lyme disease (also known as Lyme borreliosis) is the most common vector-borne disease in the United States with an estimated 476,000 cases per year. While historically, the long-term impact of Lyme disease on patients has been controversial, mounting evidence supports the idea that a substantial number of patients experience persistent symptoms following treatment. The research community has largely lacked the necessary funding to properly advance the scientific and clinical understanding of the disease, or to develop and evaluate innovative approaches for prevention, diagnosis, and treatment. Given the many outstanding questions raised into the diagnosis, clinical presentation and treatment of Lyme disease, and the underlying molecular mechanisms that trigger persistent disease, there is an urgent need for more support. This review article summarizes progress over the past 5 years in our understanding of Lyme and tick-borne diseases in the United States and highlights remaining challenges.

Reported County-Level Distribution of Lyme Disease Spirochetes, Borrelia burgdorferi sensu stricto and Borrelia mayonii (Spirochaetales: Spirochaetaceae), in Host-Seeking Ixodes scapularis and Ixodes pacificus Ticks (Acari: Ixodidae) in the Contiguous United States

Lyme disease is the most common vector-borne disease in the United States. While Lyme disease vectors are widespread, high incidence states are concentrated in the Northeast, North Central and Mid-Atlantic regions. Mapping the distribution of Lyme disease spirochetes in ticks may aid in providing data-driven explanations of epidemiological trends and recommendations for targeting prevention strategies to communities at risk. We compiled data from the literature, publicly available tickborne pathogen surveillance databases, and internal CDC pathogen testing databases to map the county-level distribution of Lyme disease spirochetes reported in host-seeking Ixodes pacificus and Ixodes scapularis across the contiguous United States. We report B. burgdorferi s.s.-infected I. scapularis from 384 counties spanning 26 eastern states located primarily in the North Central, Northeastern, and Mid-Atlantic regions, and in I. pacificus from 20 counties spanning 2 western states, with most records reported from northern and north-coastal California. Borrelia mayonii was reported in I. scapularis in 10 counties in Minnesota and Wisconsin in the North Central United States, where records of B. burgdorferi s.s. were also reported. In comparison to a broad distribution of vector ticks, the resulting map shows a more limited distribution of Lyme disease spirochetes.

Molecular Microbiological and Immune Characterization of a Cohort of Patients Diagnosed with Early Lyme Disease

Lyme disease is a tick-borne infection caused by the bacteria Borrelia burgdorferi Current diagnosis of early Lyme disease relies heavily on clinical criteria, including the presence of an erythema migrans rash. The sensitivity of current gold-standard diagnostic tests relies upon antibody formation, which is typically delayed and thus of limited utility in early infection. We conducted a study of blood and skin biopsy specimens from 57 patients with a clinical diagnosis of erythema migrans. Samples collected at the time of diagnosis were analyzed using an ultrasensitive, PCR-based assay employing an isothermal amplification step and multiple primers. In 75.4% of patients, we directly detected one or more B. burgdorferi genotypes in the skin. Two-tier testing showed that 20 (46.5%) of those found to be PCR positive remained serologically negative at both acute and convalescent time points. Multiple genotypes were found in three (8%) of those where a specific genotype could be identified. The 13 participants who lacked PCR and serologic evidence for exposure to B. burgdorferi could be differentiated as a group from PCR-positive participants by their levels of several immune markers as well as by clinical descriptors such as the number of acute symptoms and the pattern of their erythema migrans rash. These results suggest that within a Mid-Atlantic cohort, patient subgroups can be identified using PCR-based direct detection approaches. This may be particularly useful in future research such as vaccine trials and public health surveillance of tick-borne disease patterns.

Post-treatment Lyme Disease as a Model for Persistent Symptoms in Lyme Disease

It has long been observed in clinical practice that a subset of patients with Lyme disease report a constellation of symptoms such as fatigue, cognitive difficulties, and musculoskeletal pain, which may last for a significant period of time. These symptoms, which can range from mild to severe, have been reported throughout the literature in both prospective and population-based studies in Lyme disease endemic regions. The etiology of these symptoms is unknown, however several illness-causing mechanisms have been hypothesized, including microbial persistence, host immune dysregulation through inflammatory or secondary autoimmune pathways, or altered neural networks, as in central sensitization. Evaluation and characterization of persistent symptoms in Lyme disease is complicated by potential independent, repeat exposures to B. burgdorferi, as well as the potential for co-morbid diseases with overlapping symptom profiles. Antibody testing for B. burgdorferi is an insensitive measure after treatment, and no other FDA-approved tests currently exist. As such, diagnosis presents a complex challenge for physicians, while the lived experience for patients is one marked by uncertainty and often illness invalidation. Currently, there are no FDA-approved pharmaceutical therapies, and the safety and efficacy of off-label and/or complementary therapies have not been well studied and are not agreed-upon within the medical community. Post-treatment Lyme disease represents a narrow, defined, mechanistically-neutral subset of this larger, more heterogeneous group of patients, and is a useful definition in research settings as an initial subgroup of study. The aim of this paper is to review the current literature on the diagnosis, etiology, risk factors, and treatment of patients with persistent symptoms in the context of Lyme disease. The meaning and relevance of existing patient subgroups will be discussed, as will future research priorities, including the need to develop illness biomarkers, elucidate the biologic mechanisms of disease, and drive improvements in therapeutic options.

Molecular Testing of Serial Blood Specimens from Patients with Early Lyme Disease during Treatment Reveals Changing Coinfection with Mixtures of Borrelia burgdorferi Genotypes

Borrelia burgdorferi is the etiological agent of Lyme disease. In the current study, we used direct-detection PCR and electrospray ionization mass spectrometry to monitor and genotype B. burgdorferi isolates from serially collected whole-blood specimens from patients clinically diagnosed with early Lyme disease before and during 21 days of antibiotic therapy. B. burgdorferi isolates were detected up to 3 weeks after the initiation of antibiotic treatment, with ratios of coinfecting B. burgdorferi genotypes changing over time.

Recent strategies for the diagnosis of early Lyme disease

Lyme disease (LD) is the most common tick-borne disease in the Northern Hemisphere. As the most prevalent vector-borne disease in the USA, LD affects 300,000 human cases each year. LD is caused by inoculation of the bacterial spirochete, Borrelia burgdorferi sensu lato, from an infected tick. If not treated quickly and completely, the bacteria disseminate from the tick's biting site into multiple organs including the joints, heart, and brain. Thus, the best outcome from medical intervention can be expected with early detection and treatment with antibiotics, prior to multi-organ dissemination. In the absence of a characteristic rash, LD is diagnosed using serological testing involving enzyme-linked immunosorbent assay (ELISA) followed by western blotting, which is collectively known as the two-tier algorithm. These assays detect host antibodies against the bacteria, but are hampered by low sensitivity, which can miss early LD cases. This review discusses the application of some current assays for diagnosing LD clinically, thus providing a foundation for exploring newer techniques being developed in the laboratory for more sensitive detection of early LD.

Xenodiagnosis Using Ixodes scapularis Larval Ticks in Humans

Xenodiagnosis is the use of a natural vector to detect the presence of an organism, and xenodiagnosis using Ixodes ticks has long been used by entomologists in Lyme disease research to provide evidence of the host's infectious status with Borrelia burgdorferi. We developed the methodology and performed the first human research study using uninfected larval Ixodes scapularis ticks to assess evidence of B. burgdorferi infection. Here, we describe in detail the methodology used for the procedure. Xenodiagnosis using Ixodes ticks in humans remains an experimental method and must be performed under an approved clinical research protocol.

Amblyomma americanum (Acari: Ixodidae) Ticks Are Not Vectors of the Lyme Disease Agent, Borrelia burgdorferi (Spirocheatales: Spirochaetaceae): A Review of the Evidence

In the early 1980s, Ixodes spp. ticks were implicated as the key North American vectors of Borrelia burgdorferi (Johnson, Schmid, Hyde, Steigerwalt and Brenner) (Spirocheatales: Spirochaetaceae), the etiological agent of Lyme disease. Concurrently, other human-biting tick species were investigated as potential B. burgdorferi vectors. Rashes thought to be erythema migrans were observed in patients bitten by Amblyomma americanum (L.) (Acari: Ixodidae) ticks, and spirochetes were visualized in a small percentage of A. americanum using fluorescent antibody staining methods, sparking interest in this species as a candidate vector of B. burgdorferi. Using molecular methods, the spirochetes were subsequently described as Borrelia lonestari sp. nov. (Spirocheatales: Spirochaetaceae), a transovarially transmitted relapsing fever Borrelia of uncertain clinical significance. In total, 54 surveys from more than 35 research groups, involving more than 52,000 ticks, have revealed a low prevalence of B. lonestari, and scarce B. burgdorferi, in A. americanum. In Lyme disease-endemic areas, A. americanum commonly feeds on B. burgdorferi-infected hosts; the extremely low prevalence of B. burgdorferi in this tick results from a saliva barrier to acquiring infection from infected hosts. At least nine transmission experiments involving B. burgdorferi in A. americanum have failed to demonstrate vector competency. Advancements in molecular analysis strongly suggest that initial reports of B. burgdorferi in A. americanum across many states were misidentified B. lonestari, or DNA contamination, yet the early reports continue to be cited without regard to the later clarifying studies. In this article, the surveillance and vector competency studies of B. burgdorferi in A. americanum are reviewed, and we conclude that A. americanum is not a vector of B. burgdorferi.

A Molecular Survey of Tick-Borne Pathogens from Ticks Collected in Central Queensland, Australia

Central Queensland (CQ) is a large and isolated, low population density, remote tropical region of Australia with a varied environment. The region has a diverse fauna and several species of ticks that feed upon that fauna. This study examined 518 individual ticks: 177 Rhipicephalus sanguineus (brown dog tick), 123 Haemaphysalis bancrofti (wallaby tick), 102 Rhipicephalus australis (Australian cattle tick), 47 Amblyomma triguttatum (ornate kangaroo tick), 57 Ixodes holocyclus (paralysis tick), 9 Bothriocroton tachyglossi (CQ short-beaked echidna tick), and 3 Ornithodoros capensis (seabird soft tick). Tick midguts were pooled by common host or environment and screened for four genera of tick-borne zoonoses by PCR and sequencing. The study examined a total of 157 midgut pools of which 3 contained DNA of Coxiella burnetii, 13 Rickettsia gravesii, 1 Rickettsia felis, and 4 other Rickettsia spp. No Borrelia spp. or Babesia spp. DNA were recovered.

Species Identification and Phylogenetic Analysis of Borrelia burgdorferi Sensu Lato Using Molecular Biological Methods

Bacterial species identification is required in different disciplines and-depending on the purpose-levels of specificity or resolution of typing may vary. Nowadays, molecular methods are the mainstay for bacterial identification and sequence-based analyses are of ever-growing importance. For diagnostics, immediate results are needed and often real-time PCR of one or two loci is the method of choice while for epidemiological or evolutionary studies sequence data of several loci improve phylogenetic resolution to required levels. Multilocus sequence typing (MLST) and multilocus sequence analyses (MLSA) utilize sequences information of several housekeeping loci (eight for Borrelia) to distinguish between species. This method has been widely used for bacterial species and strain identification and will be described in this chapter.As more and more diversity is being detected in the Borrelia burgdorferi sensu lato species complex, the importance of accurate species and strain typing has come to the fore. This is particularly significant with a view of differentiating human pathogenic and non-pathogenic strains or species and understanding the epidemiology, ecology, population structure, and evolution of species.

Broad-range survey of vector-borne pathogens and tick host identification of Ixodes ricinus from Southern Czech Republic

Ixodes ricinus ticks are vectors of numerous human and animal pathogens. They are host generalists able to feed on more than 300 vertebrate species. The prevalence of tick-borne pathogens is influenced by host-vector-pathogen interactions that results in spatial distribution of infection risk. Broad-range polymerase chain reaction electrospray ionization mass spectrometry (PCR/ESI-MS) was used to analyze 435 I. ricinus nymphs from four localities in the south of the Czech Republic for the species identification of tick-borne pathogens. Borrelia burgdorferi sensu lato spirochetes were the most common pathogen detected in the ticks; 21% of ticks were positive for a single genospecies and 2% were co-infected with two genospecies. Other tick-borne pathogens detected included Rickettsia helvetica (3.9%), R. monacensis (0.2%), Anaplasma phagocytophilum (2.8%), Babesia venatorum (0.9%), and Ba. microti (0.5%). The vertebrate host of the ticks was determined using PCR followed by reverse line blot hybridization from the tick's blood-meal remnants. The host was identified for 61% of ticks. DNA of two hosts was detected in 16% of samples with successful host identification. The majority of ticks had fed on artiodactyls (50.7%) followed by rodents (28.6%) and birds (7.8%). Other host species were wild boar, deer, squirrels, field mice and voles.

Parallelisms and Contrasts in the Diverse Ecologies of the Anaplasma phagocytophilum and Borrelia burgdorferi Complexes of Bacteria in the Far Western United States

Anaplasma phagocytophilum and Borrelia burgdorferi are two tick-borne bacteria that cause disease in people and animals. For each of these bacteria, there is a complex of closely related genospecies and/or strains that are genetically distinct and have been shown through both observational and experimental studies to have different host tropisms. In this review we compare the known ecologies of these two bacterial complexes in the far western USA and find remarkable similarities, which will help us understand evolutionary histories and coadaptation among vertebrate host, tick vector, and bacteria. For both complexes, sensu stricto genospecies (those that infect humans) share a similar geographic range, are vectored mainly by ticks in the Ixodes ricinus-complex, utilize mainly white-footed mice (Peromyscus leucopus) as a reservoir in the eastern USA and tree squirrels in the far west, and tend to be generalists, infecting a wider variety of vertebrate host species. Other sensu lato genospecies within each complex are generally more specialized, occurring often in local enzootic cycles within a narrow range of vertebrate hosts and specialized vector species. We suggest that these similar ecologies may have arisen through utilization of a generalist tick species as a vector, resulting in a potentially more virulent generalist pathogen that spills over into humans, vs. utilization of a specialized tick vector on a particular vertebrate host species, promoting microbe specialization. Such tight host-vector-pathogen coupling could also facilitate high enzootic prevalence and the evolution of host immune-tolerance and bacterial avirulence.

Multiple independent transmission cycles of a tick-borne pathogen within a local host community

Many pathogens are maintained by multiple host species and involve multiple strains with potentially different phenotypic characteristics. Disentangling transmission patterns in such systems is often challenging, yet investigating how different host species contribute to transmission is crucial to properly assess and manage disease risk. We aim to reveal transmission cycles of bacteria within the Borrelia burgdorferi species complex, which include Lyme disease agents. We characterized Borrelia genotypes found in 488 infected Ixodes ricinus nymphs collected in the Sénart Forest located near Paris (France). These genotypes were compared to those observed in three sympatric species of small mammals and network analyses reveal four independent transmission cycles. Statistical modelling shows that two cycles involving chipmunks, an introduced species, and non-sampled host species such as birds, are responsible for the majority of tick infections. In contrast, the cycle involving native bank voles only accounts for a small proportion of infected ticks. Genotypes associated with the two primary transmission cycles were isolated from Lyme disease patients, confirming the epidemiological threat posed by these strains. Our work demonstrates that combining high-throughput sequence typing with networks tools and statistical modeling is a promising approach for characterizing transmission cycles of multi-host pathogens in complex ecological settings.

Crimean-Congo hemorrhagic fever virus in livestock ticks and animal handler seroprevalence at an abattoir in Ghana

Background

Crimean-Congo Haemorrhagic Fever Virus (CCHFV) is a zoonotic virus transmitted by Ixodid ticks and causes Crimean-Congo hemorrhagic fever (CCHF) disease in humans with up to 50 % mortality rate.

Methods

Freshly slaughtered livestock at the Kumasi abattoir in the Ashanti Region of Ghana were examined for the presence of ticks once a month over a 6-month period from May to November 2011. The ticks were grouped into pools by species, sex, and animal source. CCHFV was detected in the ticks using reverse transcription PCR. Blood samples were collected from enrolled abattoir workers at initiation, and from those who reported fever in a preceding 30-day period during monthly visits 2–5 months after initiation. Six months after initiation, all participants who provided baseline samples were invited to provide blood samples. Serology was performed using enzyme linked immunosorbent assay (ELISA). Demographic and epidemiological data was also obtained from enrolled participants using a structured questionnaire.

Results

Of 428 freshly slaughtered animals comprising 130 sheep, 149 cattle, and 149 goats examined, 144 ticks belonging to the genera Ambylomma, Hyalomma and Boophilus were identified from 57 (13.3 %): 52 (34.9 %), 4 (3.1 %) and 1 (0.7 %) cattle, sheep and goat respectively. Of 97 tick pools tested, 5 pools comprising 1 pool of Hyalomma excavatum and 4 pools of Ambylomma variegatum, collected from cattle, were positive for CCHFV. Of 188 human serum samples collected from 108 abattoir workers, 7 (3.7 %) samples from 6 persons were anti-CCHF IgG positive with one of them also being CCHF IgM positive. The seroprevalence of CCHFV identified in this study was 5.7 %.

Conclusions

This study detected human exposure to CCHF virus in slaughterhouse workers and also identified the CCHF virus in proven vectors (ticks) of Crimean Congo hemorrhagic fever in Ghana. The CCHFV was detected only in ticks collected from cattle, one of the livestock known to play a role in the amplification of the CCHF virus.

The IRIDICA BAC BSI Assay: Rapid, Sensitive and Culture-Independent Identification of Bacteria and Candida in Blood

Bloodstream infection (BSI) and sepsis are rising in incidence throughout the developed world. The spread of multi-drug resistant organisms presents increasing challenges to treatment. Surviving BSI is dependent on rapid and accurate identification of causal organisms, and timely application of appropriate antibiotics. Current culture-based methods used to detect and identify agents of BSI are often too slow to impact early therapy and may fail to detect relevant organisms in many positive cases. Existing methods for direct molecular detection of microbial DNA in blood are limited in either sensitivity (likely the result of small sample volumes) or in breadth of coverage, often because the PCR primers and probes used target only a few specific pathogens. There is a clear unmet need for a sensitive molecular assay capable of identifying the diverse bacteria and yeast associated with BSI directly from uncultured whole blood samples. We have developed a method of extracting DNA from larger volumes of whole blood (5 ml per sample), amplifying multiple widely conserved bacterial and fungal genes using a mismatch- and background-tolerant PCR chemistry, and identifying hundreds of diverse organisms from the amplified fragments on the basis of species-specific genetic signatures using electrospray ionization mass spectrometry (PCR/ESI-MS). We describe the analytical characteristics of the IRIDICA BAC BSI Assay and compare its pre-clinical performance to current standard-of-care methods in a collection of prospectively collected blood specimens from patients with symptoms of sepsis. The assay generated matching results in 80% of culture-positive cases (86% when common contaminants were excluded from the analysis), and twice the total number of positive detections. The described method is capable of providing organism identifications directly from uncultured blood in less than 8 hours. Disclaimer: The IRIDICA BAC BSI Assay is not available in the United States.

Trans-Atlantic exchanges have shaped the population structure of the Lyme disease agent Borrelia burgdorferi sensu stricto

The origin and population structure of Borrelia burgdorferi sensu stricto (s.s.), the agent of Lyme disease, remain obscure. This tick-transmitted bacterial species occurs in both North America and Europe. We sequenced 17 European isolates (representing the most frequently found sequence types in Europe) and compared these with 17 North American strains. We show that trans-Atlantic exchanges have occurred in the evolutionary history of this species and that a European origin of B. burgdorferi s.s. is marginally more likely than a USA origin. The data further suggest that some European human patients may have acquired their infection in North America. We found three distinct genetically differentiated groups: i) the outgroup species Borrelia bissettii, ii) two divergent strains from Europe, and iii) a group composed of strains from both the USA and Europe. Phylogenetic analysis indicated that different genotypes were likely to have been introduced several times into the same area. Our results demonstrate that irrespective of whether B. burgdorferi s.s. originated in Europe or the USA, later trans-Atlantic exchange(s) have occurred and have shaped the population structure of this genospecies. This study clearly shows the utility of next generation sequencing to obtain a better understanding of the phylogeography of this bacterial species.

Borrelia yangtzensis sp. nov., a rodent-associated species in Asia, is related to Borrelia valaisiana

Twenty-nine isolates of Lyme borreliosis (LB) group spirochaetes collected from ticks and rodents in China and Japan were included in a multilocus sequence analysis (MLSA). Using a different typing system, three of these strains had previously been identified as being divergent from other LB spirochaete species and the name 'Borrelia yangtze' sp. nov. was proposed. The data presented here confirm that the genetic distance, calculated using sequences of MLSA housekeeping genes, to other known LB group spirochaete species was < 95 % and to Borrelia valaisiana was 96.67 % (which represents the most closely related species within the group of LB spirochaetes). This and the fact that these strains are ecologically distinct from B. valaisiana (rodent-transmitted vs bird-transmitted) provide strong support for the validation of the proposed species status. We suggest the name Borrelia yangtzensis sp. nov. The type strain is Okinawa-CW62T ( = DSM 24625T = JCM 17189T).

Broad-range survey of tick-borne pathogens in Southern Germany reveals a high prevalence of Babesia microti and a diversity of other tick-borne pathogens

Abstract Ticks harbor numerous pathogens of significance to human and animal health. A better understanding of the pathogens carried by ticks in a given geographic area can alert health care providers of specific health risks leading to better diagnosis and treatments. In this study, we tested 226 Ixodes ricinis ticks from Southern Germany using a broad-range PCR and electrospray ionization mass spectrometry assay (PCR/ESI-MS) designed to identify tick-borne bacterial and protozoan pathogens in a single test. We found 21.2% of the ticks tested carried Borrelia burgdorferi sensu lato consisting of diverse genospecies; a surprisingly high percentage of ticks were infected with Babesia microti (3.5%). Other organisms found included Borrelia miyamotoi, Rickettsia helvetica, Rickettsia monacensis, and Anaplasma phagocytophilum. Of further significance was our finding that more than 7% of ticks were infected with more than one pathogen or putative pathogen.

Survey of Ixodes pacificus Ticks in California Reveals a Diversity of Microorganisms and a Novel and Widespread Anaplasmataceae Species

Ixodes pacificus ticks can harbor a wide range of human and animal pathogens. To survey the prevalence of tick-borne known and putative pathogens, we tested 982 individual adult and nymphal I. pacificus ticks collected throughout California between 2007 and 2009 using a broad-range PCR and electrospray ionization mass spectrometry (PCR/ESI-MS) assay designed to detect a wide range of tick-borne microorganisms. Overall, 1.4% of the ticks were found to be infected with Borrelia burgdorferi, 2.0% were infected with Borrelia miyamotoi and 0.3% were infected with Anaplasma phagocytophilum. In addition, 3.0% were infected with Babesia odocoilei. About 1.2% of the ticks were co-infected with more than one pathogen or putative pathogen. In addition, we identified a novel Anaplasmataceae species that we characterized by sequencing of its 16S rRNA, groEL, gltA, and rpoB genes. Sequence analysis indicated that this organism is phylogenetically distinct from known Anaplasma species with its closest genetic near neighbors coming from Asia. The prevalence of this novel Anaplasmataceae species was as high as 21% at one site, and it was detected in 4.9% of ticks tested statewide. Based upon this genetic characterization we propose that this organism be called ‘Candidatus Cryptoplasma californiense’. Knowledge of this novel microbe will provide awareness for the community about the breadth of the I. pacificus microbiome, the concept that this bacterium could be more widely spread; and an opportunity to explore whether this bacterium also contributes to human or animal disease burden.

Prevalence of Borrelia miyamotoi in Ixodes ticks in Europe and the United States

Infection rates of Ixodes ticks with Borrelia miyamotoi in Europe and the United States vary greatly based upon location.

Borrelia miyamotoi, a relapsing fever-related spirochete transmitted by Ixodes ticks, has been recently shown to be a human pathogen. To characterize the prevalence of this organism in questing Ixodes ticks, we tested 2,754 ticks for a variety of tickborne pathogens by PCR and electrospray-ionization mass spectrometry. Ticks were collected from California, New York, Connecticut, Pennsylvania, and Indiana in the United States and from Germany and the Czech Republic in Europe from 2008 through 2012. In addition, an isolate from Japan was characterized. We found 3 distinct genotypes, 1 for North America, 1 for Europe, and 1 for Japan. We found B. miyamotoi infection in ticks in 16 of the 26 sites surveyed, with infection prevalence as high as 15.4%. These results show the widespread distribution of the pathogen, indicating an exposure risk to humans in areas where Ixodes ticks reside.

Borrelia burgdorferi not confirmed in human-biting Amblyomma americanum ticks from the southeastern United States

The predominant human-biting tick throughout the southeastern United States is Amblyomma americanum. Its ability to transmit pathogens causing Lyme disease-like illnesses is a subject of ongoing controversy. Results of previous testing by the Department of Defense Human Tick Test Kit Program and other laboratories indicated that it is highly unlikely that A. americanum transmits any pathogen that causes Lyme disease. In contrast, a recent publication by Clark and colleagues (K. L. Clark, B. Leydet, and S. Hartman, Int. J. Med. Sci. 10:915-931, 2013) reported detection of Lyme group Borrelia in A. americanum using a nested-flagellin-gene PCR. We evaluated this assay by using it and other assays to test 1,097 A. americanum ticks collected from humans. Using the Clark assay, in most samples we observed nonspecific amplification and nonrepeatability of results on subsequent testing of samples. Lack of reaction specificity and repeatability is consistent with mispriming, likely due to high primer concentrations and low annealing temperatures in this protocol. In six suspect-positive samples, Borrelia lonestari was identified by sequencing of an independent gene region; this is not a Lyme group spirochete and is not considered zoonotic. B. burgdorferi was weakly amplified from one pool using some assays, but not others, and attempts to sequence the amplicon of this pool failed, as did attempts to amplify and sequence B. burgdorferi from the five individual samples comprising this pool. Therefore, B. burgdorferi was not confirmed in any sample. Our results do not support the hypothesis that A. americanum ticks are a vector for Lyme group Borrelia infections.

Lyme meningo-radiculitis responsive to oral doxycycline therapy in the USA

The spirochete strains that cause Lyme disease are different between the USA and Europe. This leads not only to a variation in clinical presentations, but it was also thought to alter responsiveness to antibiotic treatment. Unlike in Europe, in the USA there are no head-to-head trials of oral and intravenous antibiotics in the treatment of neuroborreliosis. Guidelines from the American Academy of Neurology (AAN) state that oral doxycycline is probably safe and effective in treating neuroborrliosis without parenchymal involvement, this was mainly extrapolated from European studies data with no reports from North America. To the best of our knowledge, this is the first reported case of Lyme meningo-radiculitis successfully treated with oral doxycycline alone in the USA. This comes in support of the oral doxycycline as an initial and even monotherapy for non-parenchymal Lyme disease of the nervous system in the USA.

Large scale spatial risk and comparative prevalence of Borrelia miyamotoi and Borrelia burgdorferi sensu lato in Ixodes pacificus

Borrelia miyamotoi is a newly described emerging pathogen transmitted to people by Ixodes species ticks and found in temperate regions of North America, Europe, and Asia. There is limited understanding of large scale entomological risk patterns of B. miyamotoi and of Borreila burgdorferi sensu stricto (ss), the agent of Lyme disease, in western North America. In this study, B. miyamotoi, a relapsing fever spirochete, was detected in adult (n=70) and nymphal (n=36) Ixodes pacificus ticks collected from 24 of 48 California counties that were surveyed over a 13 year period. Statewide prevalence of B. burgdorferi sensu lato (sl), which includes B. burgdorferi ss, and B. miyamotoi were similar in adult I. pacificus (0.6% and 0.8%, respectively). In contrast, the prevalence of B. burgdorferi sl was almost 2.5 times higher than B. miyamotoi in nymphal I. pacificus (3.2% versus 1.4%). These results suggest similar risk of exposure to B. burgdorferi sl and B. miyamotoi from adult I. pacificus tick bites in California, but a higher risk of contracting B. burgdorferi sl than B. miyamotoi from nymphal tick bites. While regional risk of exposure to these two spirochetes varies, the highest risk for both species is found in north and central coastal California and the Sierra Nevada foothill region, and the lowest risk is in southern California; nevertheless, tick-bite avoidance measures should be implemented in all regions of California. This is the first study to comprehensively evaluate entomologic risk for B. miyamotoi and B. burgdorferi for both adult and nymphal I. pacificus, an important human biting tick in western North America.

Improved sensitivity for molecular detection of bacterial and Candida infections in blood

The rapid identification of bacteria and fungi directly from the blood of patients with suspected bloodstream infections aids in diagnosis and guides treatment decisions. The development of an automated, rapid, and sensitive molecular technology capable of detecting the diverse agents of such infections at low titers has been challenging, due in part to the high background of genomic DNA in blood. PCR followed by electrospray ionization mass spectrometry (PCR/ESI-MS) allows for the rapid and accurate identification of microorganisms but with a sensitivity of about 50% compared to that of culture when using 1-ml whole-blood specimens. Here, we describe a new integrated specimen preparation technology that substantially improves the sensitivity of PCR/ESI-MS analysis. An efficient lysis method and automated DNA purification system were designed for processing 5 ml of whole blood. In addition, PCR amplification formulations were optimized to tolerate high levels of human DNA. An analysis of 331 specimens collected from patients with suspected bloodstream infections resulted in 35 PCR/ESI-MS-positive specimens (10.6%) compared to 18 positive by culture (5.4%). PCR/ESI-MS was 83% sensitive and 94% specific compared to culture. Replicate PCR/ESI-MS testing from a second aliquot of the PCR/ESI-MS-positive/culture-negative specimens corroborated the initial findings in most cases, resulting in increased sensitivity (91%) and specificity (99%) when confirmed detections were considered true positives. The integrated solution described here has the potential to provide rapid detection and identification of organisms responsible for bloodstream infections.

The Heterogeneity, Distribution, and Environmental Associations of Borrelia burgdorferi Sensu Lato, the Agent of Lyme Borreliosis, in Scotland

Lyme borreliosis is an emerging infectious human disease caused by the Borrelia burgdorferi sensu lato complex of bacteria with reported cases increasing in many areas of Europe and North America. To understand the drivers of disease risk and the distribution of symptoms, which may improve mitigation and diagnostics, here we characterize the genetics, distribution, and environmental associations of B. burgdorferi s.l. genospecies across Scotland. In Scotland, reported Lyme borreliosis cases have increased almost 10-fold since 2000 but the distribution of B. burgdorferi s.l. is so far unstudied. Using a large survey of over 2200 Ixodes ricinus tick samples collected from birds, mammals, and vegetation across 25 sites we identified four genospecies: Borrelia afzelii (48%), Borrelia garinii (36%), Borrelia valaisiana (8%), and B. burgdorferi sensu stricto (7%), and one mixed genospecies infection. Surprisingly, 90% of the sequence types were novel and, importantly, up to 14% of samples were mixed intra-genospecies co-infections, suggesting tick co-feeding, feeding on multiple hosts, or multiple infections in hosts. B. garinii (hosted by birds) was considerably more genetically diverse than B. afzelii (hosted by small mammals), as predicted since there are more species of birds than small mammals and birds can import strains from mainland Europe. Higher proportions of samples contained B. garinii and B. valaisiana in the west, while B. afzelii and B. garinii were significantly more associated with mixed/deciduous than with coniferous woodlands. This may relate to the abundance of transmission hosts in different regions and habitats. These data on the genetic heterogeneity within and between Borrelia genospecies are a first step to understand pathogen spread and could help explain the distribution of patient symptoms, which may aid local diagnosis. Understanding the environmental associations of the pathogens is critical for rational policy making for disease risk mitigation and land management.

Molecular Typing of Borrelia burgdorferi

Borrelia burgdorferi sensu lato is a group of spirochetes belonging to the genus Borrelia in the family of Spirochaetaceae. The spirochete is transmitted between reservoirs and hosts by ticks of the family Ixodidae. Infection with B. burgdorferi in humans causes Lyme disease or Lyme borreliosis. Currently, 20 Lyme disease-associated Borrelia species and more than 20 relapsing fever-associated Borrelia species have been described. Identification and differentiation of different Borrelia species and strains is largely dependent on analyses of their genetic characteristics. A variety of molecular techniques have been described for Borrelia isolate speciation, molecular epidemiology, and pathogenicity studies. In this unit, we focus on three basic protocols, PCR-RFLP-based typing of the rrs-rrlA and rrfA-rrlB ribosomal spacer, ospC typing, and MLST. These protocols can be employed alone or in combination for characterization of B. burgdorferi isolates or directly on uncultivated organisms in ticks, mammalian host reservoirs, and human clinical specimens.

Rapid detection and differentiation of human noroviruses using RT-PCR coupled to electrospray ionization mass spectrometry

The goal of this study was to develop an assay for the detection and differentiation of noroviruses using RT-PCR followed by electrospray ionization mass spectrometry (ESI-MS). Detection of hepatitis A virus was also considered. Thirteen primer pairs were designed for use in this assay and a reference database was created using GenBank sequences and reference norovirus samples. The assay was tested for inclusivity and exclusivity using 160 clinical norovirus samples, 3 samples of hepatitis A virus and 3 other closely related viral strains. Results showed that the assay was able to detect norovirus with a sensitivity of 92% and a specificity of 100%. Norovirus identification at the genogroup level was correct for 98% of samples detected by the assay and for 75% of a subset of samples (n = 32) compared at the genotype level. Identification of norovirus genotypes is expected to improve as more reference samples are added to the database. The assay was also capable of detecting and genotyping hepatitis A virus in all 3 samples tested. Overall, the assay developed here allows for detection and differentiation of noroviruses within one working day and may be used as a tool in surveillance efforts or outbreak investigations.

Insights into the biology of Borrelia burgdorferi gained through the application of molecular genetics

Borrelia burgdorferi, the vector-borne bacterium that causes Lyme disease, was first identified in 1982. It is known that much of the pathology associated with Lyme borreliosis is due to the spirochete's ability to infect, colonize, disseminate, and survive within the vertebrate host. Early studies aimed at defining the biological contributions of individual genes during infection and transmission were hindered by the lack of adequate tools and techniques for molecular genetic analysis of the spirochete. The development of genetic manipulation techniques, paired with elucidation and annotation of the B. burgdorferi genome sequence, has led to major advancements in our understanding of the virulence factors and the molecular events associated with Lyme disease. Since the dawn of this genetic era of Lyme research, genes required for vector or host adaptation have garnered significant attention and highlighted the central role that these components play in the enzootic cycle of this pathogen. This chapter covers the progress made in the Borrelia field since the application of mutagenesis techniques and how they have allowed researchers to begin ascribing roles to individual genes. Understanding the complex process of adaptation and survival as the spirochete cycles between the tick vector and vertebrate host will lead to the development of more effective diagnostic tools as well as identification of novel therapeutic and vaccine targets. In this chapter, the Borrelia genes are presented in the context of their general biological roles in global gene regulation, motility, cell processes, immune evasion, and colonization/dissemination.

Xenodiagnosis to detect Borrelia burgdorferi infection: a first-in-human study

BACKGROUND

Animal studies suggest that Borrelia burgdorferi, the agent of Lyme disease, may persist after antibiotic therapy and can be detected by various means including xenodiagnosis using the natural tick vector (Ixodes scapularis). No convincing evidence exists for the persistence of viable spirochetes after recommended courses of antibiotic therapy in humans. We determined the safety of using I. scapularis larvae for the xenodiagnosis of B. burgdorferi infection in humans.

METHODS

Laboratory-reared larval I. scapularis ticks were placed on 36 subjects and allowed to feed to repletion. Ticks were tested for B. burgdorferi by polymerase chain reaction (PCR), culture, and/or isothermal amplification followed by PCR and electrospray ionization mass spectroscopy. In addition, attempts were made to infect immunodeficient mice by tick bite or inoculation of tick contents. Xenodiagnosis was repeated in 7 individuals.

RESULTS

Xenodiagnosis was well tolerated with no severe adverse events. The most common adverse event was mild itching at the tick attachment site. Xenodiagnosis was negative in 16 patients with posttreatment Lyme disease syndrome (PTLDS) and/or high C6 antibody levels and in 5 patients after completing antibiotic therapy for erythema migrans. Xenodiagnosis was positive for B. burgdorferi DNA in a patient with erythema migrans early during therapy and in a patient with PTLDS. There is insufficient evidence, however, to conclude that viable spirochetes were present in either patient.

CONCLUSIONS

Xenodiagnosis using Ixodes scapularis larvae was safe and well tolerated. Further studies are needed to determine the sensitivity of xenodiagnosis in patients with Lyme disease and the significance of a positive result. Clinical Trials Registration NCT01143558.

Reservoir targeted vaccine against Borrelia burgdorferi: a new strategy to prevent Lyme disease transmission

A high prevalence of infection with Borrelia burgdorferi in ixodid ticks is correlated with a high incidence of Lyme disease. The transmission of B. burgdorferi to humans can be disrupted by targeting 2 key elements in its enzootic cycle: the reservoir host and the tick vector. In a prospective 5-year field trial, we show that oral vaccination of wild white-footed mice resulted in outer surface protein A-specific seropositivity that led to reductions of 23% and 76% in the nymphal infection prevalence in a cumulative, time-dependent manner (2 and 5 years, respectively), whereas the proportion of infected ticks recovered from control plots varied randomly over time. Significant decreases in tick infection prevalence were observed within 3 years of vaccine deployment. Implementation of such a long-term public health measure could substantially reduce the risk of human exposure to Lyme disease.

Inter- and intra-specific pan-genomes of Borrelia burgdorferi sensu lato: genome stability and adaptive radiation

BACKGROUND

Lyme disease is caused by spirochete bacteria from the Borrelia burgdorferi sensu lato (B. burgdorferi s.l.) species complex. To reconstruct the evolution of B. burgdorferi s.l. and identify the genomic basis of its human virulence, we compared the genomes of 23 B. burgdorferi s.l. isolates from Europe and the United States, including B. burgdorferi sensu stricto (B. burgdorferi s.s., 14 isolates), B. afzelii (2), B. garinii (2), B. "bavariensis" (1), B. spielmanii (1), B. valaisiana (1), B. bissettii (1), and B. "finlandensis" (1).

RESULTS

Robust B. burgdorferi s.s. and B. burgdorferi s.l. phylogenies were obtained using genome-wide single-nucleotide polymorphisms, despite recombination. Phylogeny-based pan-genome analysis showed that the rate of gene acquisition was higher between species than within species, suggesting adaptive speciation. Strong positive natural selection drives the sequence evolution of lipoproteins, including chromosomally-encoded genes 0102 and 0404, cp26-encoded ospC and b08, and lp54-encoded dbpA, a07, a22, a33, a53, a65. Computer simulations predicted rapid adaptive radiation of genomic groups as population size increases.

CONCLUSIONS

Intra- and inter-specific pan-genome sizes of B. burgdorferi s.l. expand linearly with phylogenetic diversity. Yet gene-acquisition rates in B. burgdorferi s.l. are among the lowest in bacterial pathogens, resulting in high genome stability and few lineage-specific genes. Genome adaptation of B. burgdorferi s.l. is driven predominantly by copy-number and sequence variations of lipoprotein genes. New genomic groups are likely to emerge if the current trend of B. burgdorferi s.l. population expansion continues.

Multilocus sequence typing of Borrelia burgdorferi suggests existence of lineages with differential pathogenic properties in humans

The clinical manifestations of Lyme disease, caused by Borrelia burgdorferi, vary considerably in different patients, possibly due to infection by strains with varying pathogenicity. Both rRNA intergenic spacer and ospC typing methods have proven to be useful tools for categorizing B. burgdorferi strains that vary in their tendency to disseminate in humans. Neither method, however, is suitable for inferring intraspecific relationships among strains that are important for understanding the evolution of pathogenicity and the geographic spread of disease. In this study, multilocus sequence typing (MLST) was employed to investigate the population structure of B. burgdorferi recovered from human Lyme disease patients. A total of 146 clinical isolates from patients in New York and Wisconsin were divided into 53 sequence types (STs). A goeBURST analysis, that also included previously published STs from the northeastern and upper Midwestern US and adjoining areas of Canada, identified 11 major and 3 minor clonal complexes, as well as 14 singletons. The data revealed that patients from New York and Wisconsin were infected with two distinct, but genetically and phylogenetically closely related, populations of B. burgdorferi. Importantly, the data suggest the existence of B. burgdorferi lineages with differential capabilities for dissemination in humans. Interestingly, the data also indicate that MLST is better able to predict the outcome of localized or disseminated infection than is ospC typing.

Assessment of new culture method for detection of Borrelia species from serum of lyme disease patients

A novel method of culturing spirochetes from the serum of U.S. Lyme disease patients was recently reported by Sapi and colleagues to have 94% sensitivity and 100% specificity for Borrelia species as assessed by microscopy and DNA sequence analysis of the pyrG gene (E. Sapi, N. Pabbati, A. Datar, E. M. Davies, A. Rattelle, and B. A. Kuo, Int. J. Med. Sci. 10:362-376, 2013). The majority of the spirochetes described were related by pyrG sequences to species of Borrelia previously undetected in North American patients without a reported history of travel to Europe or Asia. To better understand these unexpected findings, we determined pyrG sequences of the laboratory reference strains used by the investigators for method development and testing of culture medium. Eighty percent (41/51) of the reported patient-derived pyrG sequences were identical to one of the laboratory strains, and an additional 12% (6/51) differed by only a single nucleotide across a 603-bp region of the pyrG gene. Thus, false positivity due to laboratory contamination of patient samples cannot be ruled out, and further validation of the proposed novel culture method is required.

Broad-spectrum biosensor capable of detecting and identifying diverse bacterial and Candida species in blood

We describe an assay which uses broad-spectrum, conserved-site PCR paired with mass spectrometry analysis of amplicons (PCR/electrospray ionization-mass spectrometry [ESI-MS]) to detect and identify diverse bacterial and Candida species in uncultured specimens. The performance of the assay was characterized using whole-blood samples spiked with low titers of 64 bacterial species and 6 Candida species representing the breadth of coverage of the assay. The assay had an average limit of detection of 100 CFU of bacteria or Candida per milliliter of blood, and all species tested yielded limits of detection between 20 and 500 CFU per milliliter. Over 99% of all detections yielded correct identifications, whether they were obtained at concentrations well above the limit of detection or at the lowest detectable concentrations. This study demonstrates the ability of broad-spectrum PCR/ESI-MS assays to detect and identify diverse organisms in complex natural matrices that contain high levels of background DNA.

Eco-epidemiological factors contributing to the low risk of human exposure to ixodid tick-borne borreliae in southern California, USA

Little is known about the eco-epidemiology of Lyme disease in southern California, a region where the incidence is much lower than it is in northern California. Here, we sought to discover the previously unknown microhabitats of nymphs of the primary vector, the western black-legged tick (Ixodes pacificus), in 3 moderately to heavily-utilized state parks in the Santa Monica Mountains in Los Angeles County; to elucidate the seasonal distribution and abundance of adults of I. pacificus and another human-biter, the Pacific Coast tick (Dermacentor occidentalis); and to determine what Lyme-disease or relapsing-fever group borreliae are present in questing nymphs or adult ticks. I. pacificus nymphs were collected infrequently at various times of day in 2 chaparral or 7 woodland litter areas by dragging (combined mean=0.4 nymphs per hour). The western fence lizard (Sceloporus occidentalis) was a choice sentinel animal for detecting the presence of I. pacificus nymphs (and larvae) in diverse biotopes even when dragging litter in them was fruitless. The abundance and seasonality of I. pacificus and D. occidentalis adults resembled what had been documented previously for these ticks in northern California. Overall, zero of 27 free-living and 118 lizard-infesting I. pacificus nymphs, 7 (0.29%) of 2392 I. pacificus adults and 2 (0.22%) of 896 D. occidentalis adults were infected with Borrelia burgdorferi sensu lato (Bb sl), but none of them harbored B. miyamotoi, a relapsing-fever group spirochete implicated recently as a zoonotic pathogen in Russia. Borrelia americana and the human pathogen B. burgdorferi sensu stricto were each detected in one (0.04%), and uncharacterized Bb sl in 5 adult I. pacificus (0.21%) that clustered with B. americana. Both PCR-positive D. occidentalis adults contained B. burgdorferi sensu stricto. We conclude that the acarologic risk of being bitten by a B. burgdorferi sensu lato-infected ixodid tick in the habitats studied is slight, which offers a plausible explanation for the low reported incidence of Lyme disease in south coastal California.