Far-Reaching Dispersal of Borrelia burgdorferi Sensu Lato-Infected Blacklegged Ticks by Migratory Songbirds in Canada

Historical associations and spatiotemporal changes of pathogen presence in ticks in Canada: A systematic review

BACKGROUND

Starting in the early 20th century, ticks and their pathogens have been detected during surveillance efforts in Canada. Since then, the geographic spread of tick vectors and tick-borne pathogens has steadily increased in Canada with the establishment of tick and host populations. Sentinel surveillance in Canada primarily focuses on Ixodes scapularis, which is the main vector of Borrelia burgdorferi, the bacterium causing Lyme disease. Other tick-borne pathogens, such as Anaplasma, Babesia, and Rickettsia species, have lower prevalence in Canada, but they are emerging or re-emerging in tick and host populations.

AIMS/MATERIALS & METHODS

Here, we assessed the historical associations between tick vectors, hosts and pathogens and identified spatiotemporal clusters of pathogen presence in ticks in Canada using data extracted from the literature.

RESULTS

Approximately one-third of ticks were infected with a pathogen, and these ticks were feeding primarily on bird and mammal hosts. B. burgdorferi was the most detected pathogen and I. scapularis harboured the greatest number of pathogens. We identified several spatial outliers of high pathogen presence in ticks in addition to five spatiotemporal clusters in southern Canada, all of which have long-established tick populations. Six spatiotemporal clusters of high pathogen presence in ticks were also identified based on surveillance method, with four clusters associated with passive surveillance and two clusters associated with active surveillance.

DISCUSSION

Our review represents the first systematic assessment of the literature that identifies historical associations and spatiotemporal changes in tick-host-pathogen disease systems in Canada over broad spatial and temporal scales.

CONCLUSION

As distinct spatiotemporal clusters were identified based on surveillance method, it is imperative that surveillance efforts employ standardized methods and data reporting to comprehensively assess the presence, spread and risk of tick-borne pathogens in tick and host populations.

New geographical records for tick-borne pathogens in ticks collected from cattle in Benin and Togo

BACKGROUND

Ticks are obligate hematophagous arthropods capable of transmitting a great variety of endemic and emerging pathogens causing diseases in animals and humans.

OBJECTIVES

The aim of this study was to investigate the presence of Bartonella spp., Rickettsia spp., Borrelia burgdorferi sensu lato (s.l.) and Anaplasma phagocytophilum in ticks collected from cattle in Benin and Togo.

METHODS

Overall, 396 (148 males, 205 females and 43 nymphs) ticks were collected from cattle in 17 districts (Benin and Togo) between 2019 and 2020. Ticks were pooled into groups of 2-6 ticks per pool according to individual host, location, species and developmental stage. The DNA of each pool was extracted for molecular screening.

RESULTS

PCR results revealed that 20 tick pools were positive for Bartonella spp. (Benin and Togo) and 23 tick pools positive for Rickettsia spp. (Benin), while all pools were negative for A. phagocytophilum and B. burgdorferi s.l. Sequence analysis of positive Rickettsia samples revealed the presence of Rickettsia aeschlimannii.

CONCLUSIONS

The present study highlights the presence of zoonotic agents in ticks collected from cattle in Benin and Togo. This information will raise awareness of tick-borne diseases among physicians and veterinarians, stimulate further studies to monitor these pathogens, and advise on necessary measures to control the spread of these zoonoses.

Errata in East Coast tick study: retort to Tufts & Diuk-Wasser

The authors overlook the first report of Haemaphysalis punctata in the Western Hemisphere documented by a pioneer acarologist in 1910. The authors assume that climate change alters movement of ticks, but provide no data. The authors’ assumptions are only opinions, and must be corrected and challenged.

Detection of Anaplasma phagocytophilum, Babesia odocoilei, Babesia sp., Borrelia burgdorferi Sensu Lato, and Hepatozoon canis in Ixodes scapularis Ticks Collected in Eastern Canada

Tick-borne pathogens cause infectious diseases that inflict much societal and financial hardship worldwide. Blacklegged ticks, Ixodes scapularis, are primary vectors of several epizootic and zoonotic pathogens. The aim was to find varius pathogens of I. scapularis and to determine their prevalence. In Ontario and Quebec, 113 I. scapularis ticks were collected from songbirds, mammals, including humans, and by flagging. PCR and DNA sequencing detected five different microorganisms: Anaplasma phagocytophilum, 1 (0.9%); Babesia odocoilei, 17 (15.3%); Babesia microti-like sp., 1 (0.9%); Borrelia burgdorferi sensu lato (Bbsl), 29 (26.1%); and Hepatozoon canis, 1 (0.9%). Five coinfections of Bbsl and Babesia odocoilei occurred. Notably, H. canis was documented for the first time in Canada and, at the same time, demonstrates the first transstadial passage of H. canis in I. scapularis. Transstadial passage of Bbsl and B. odocoilei was also witnessed. A novel undescribed piroplasm (Babesia microti-like) was detected. An established population of I. scapularis ticks was detected at Ste-Anne-de-Bellevue, Quebec. Because songbirds widely disperse I. scapularis larvae and nymphs, exposure in an endemic area is not required to contract tick-borne zoonoses. Based on the diversity of zoonotic pathogens in I. scapularis ticks, clinicians need to be aware that people who are bitten by I. scapularis ticks may require select antimicrobial regimens.

Detection of Babesia odocoilei in Humans with Babesiosis Symptoms

Human babesiosis is a life-threatening infectious disease that causes societal and economic impact worldwide. Several species of Babesia cause babesiosis in terrestrial vertebrates, including humans. A one-day clinic was held in Ontario, Canada, to see if a red blood cell parasite, which is present in blacklegged ticks, Ixodes scapularis, is present in humans. Based on PCR testing and DNA sequencing of the 18S rRNA gene, we unveiled B. odocoilei in two of 19 participants. DNA amplicons from these two patients are almost identical matches with the type strains of B. odocoilei in GenBank. In addition, the same two human subjects had the hallmark symptoms of human babesiosis, including night sweats, chills, fevers, and profound fatigue. Based on symptoms and molecular identification, we provide substantive evidence that B. odocoilei is pathogenic to humans. Dataset reveals that B. odocoilei serologically cross-reacts with Babesia duncani. Clinicians must realize that there are more than two Babesia spp. in North America that cause human babesiosis. This discovery signifies the first report of B. odocoilei causing human babesiosis.

Detection of Babesia odocoilei in Ixodes scapularis Ticks Collected in Southern Ontario, Canada

Tick-borne zoonotic diseases have an economic and societal impact on the well-being of people worldwide. In the present study, a high frequency of Babesia odocoilei, a red blood cell parasite, was observed in the Huronia area of Ontario, Canada. Notably, 71% (15/21) blacklegged ticks, Ixodes scapularis, collected from canine and feline hosts were infected with B. odocoilei. Consistent with U.S. studies, 12.5% (4/32) of questing I. scapularis adults collected by flagging in various parts of southwestern Ontario were positive for B. odocoilei. Our data show that all B. odocoilei strains in the present study have consistent genetic identity, and match type strains in the GenBank database. The high incidence of B. odocoilei in the Huronia area indicates that this babesial infection is established, and is cycling enzootically in the natural environment. Our data confirm that B. odocoilei has wide distribution in southern Ontario.

Human and Veterinary Vaccines for Lyme Disease

Lyme disease (LD) is an emerging zoonotic infection that is increasing in incidence in North America, Europe, and Asia. With the development of safe and efficacious vaccines, LD can potentially be prevented. Vaccination offers a cost-effective and safe approach for decreasing the risk of infection. While LD vaccines have been widely used in veterinary medicine, they are not available as a preventive tool for humans. Central to the development of effective vaccines is an understanding of the enzootic cycle of LD, differential gene expression of Borrelia burgdorferi in response to environmental variables, and the genetic and antigenic diversity of the unique bacteria that cause this debilitating disease. Here we review these areas as they pertain to past and present efforts to develop human, veterinary, and reservoir targeting LD vaccines. In addition, we offer a brief overview of additional preventative measures that should employed in conjunction with vaccination.

Microbiome Composition and Borrelia Detection in Ixodes scapularis Ticks at the Northwestern Edge of Their Range

Lyme disease-causing Borrelia burgdorferi has been reported in 10–19% of Ixodes ticks from Alberta, Canada, where the tick vector Ixodes scapularis is at the northwestern edge of its range. However, the presence of Borrelia has not been verified independently, and the bacterial microbiome of these ticks has not been described. We performed 16S rRNA bacterial surveys on female I. scapularis from Alberta that were previously qPCR-tested in a Lyme disease surveillance program. Both 16S and qPCR methods were concordant for the presence of Borrelia. The 16S studies also provided a profile of associated bacteria that showed the microbiome of I. scapularis in Alberta was similar to other areas of North America. Ticks that were qPCR-positive for Borrelia had significantly greater bacterial diversity than Borrelia-negative ticks, on the basis of generalized linear model testing. This study adds value to ongoing tick surveillance and is a foundation for deeper understanding of tick microbial ecology and disease transmission in a region where I. scapularis range expansion, induced by climate and land use changes, is likely to have increasing public health implications.

Detection of Borrelia burgdorferi Sensu Lato and Relapsing Fever Borrelia in Feeding Ixodes Ticks and Rodents in Sarawak, Malaysia: New Geographical Records of Borrelia yangtzensis and Borrelia miyamotoi

Members of the Borrelia burgdorferi sensu lato (Bbsl) complex are etiological agents of Lyme disease (LD), and Borrelia miyamotoi is one of the relapsing fever Borrelia (RFB). Despite the serological evidence of LD in Malaysia, there has been no report from Sarawak, Malaysian Borneo. Thus, this study aimed to detect and characterize Borrelia in rodents and Ixodes ticks from primary forests and an oil palm (OP) plantation in Sarawak. Borrelia yangtzensis (a member of the Bbsl complex) was detected in 43.8% (14/32) of Ixodes granulatus; most of the positive ticks were from the OP plantation (13/14). Out of 56 rodents, B. yangtzensis was detected in four Rattus spp. from the OP plantation and B. miyamotoi was detected in one rodent, Sundamys muelleri, from the primary forest. Further, the positive samples of B. yangtzensis were randomly selected for multilocus sequence analysis (MLSA). The MLSA results of successfully amplified tick samples revealed a clustering with the sequences isolated from Japan and China. This study is the first evidence of B. miyamotoi, a known human pathogen in Malaysia, and B. yangtzensis, which is circulating in ticks and rodents in Sarawak, Malaysian Borneo, and presenting a new geographical record of the Borrelia spp.

Detection of Babesia odocoilei in Ixodes scapularis Ticks Collected from Songbirds in Ontario and Quebec, Canada

Songbirds widely disperse ticks that carry a diversity of pathogens, some of which are pathogenic to humans. Among ticks commonly removed from songbirds, the blacklegged tick, Ixodes scapularis, can harbor any combination of nine zoonotic pathogens, including Babesia species. From May through September 2019, a total 157 ticks were collected from 93 songbirds of 29 species in the Canadian provinces of Ontario and Québec. PCR testing for the 18S gene of Babesia species detected Babesia odocoilei in 12.63% of I. scapularis nymphs parasitizing songbirds in Ontario and Québec; none of the relatively small numbers of Ixodes muris, Ixodes brunneus, or Haemaphysalis leporispalustris were PCR-positive. For ticks at each site, the prevalence of B. odocoilei was 16.67% in Ontario and 8.89% and 5.26% in Québec. Of 31 live, engorged I. scapularis larvae and nymphs held to molt, 25 ticks completed the molt; five of these molted ticks were positive for B. odocoilei. PCR-positive ticks were collected from six bird species—namely, Common Yellowthroat, Swainson’s Thrush, Veery, House Wren, Baltimore Oriole, and American Robin. Phylogenetic analysis documented the close relationship of B. odocoilei to Babesia canis canis and Babesia divergens, the latter a known pathogen to humans. For the first time in Canada, we confirm the transstadial passage of B. odocoilei in I. scapularis molting from larvae to nymphs. A novel host record reveals I. scapularis on a Palm Warbler. Our findings show that B. odocoilei is present in all mobile life stages of I. scapularis, and it is widely dispersed by songbirds in Ontario and Québec.

Monitoring of Nesting Songbirds Detects Established Population of Blacklegged Ticks and Associated Lyme Disease Endemic Area in Canada

This study provides a novel method of documenting established populations of bird-feeding ticks. Single populations of the blacklegged tick, Ixodes scapularis, and the rabbit tick, Haemaphysalis leporispalustris, were revealed in southwestern Québec, Canada. Blacklegged tick nymphs and, similarly, larval and nymphal rabbit ticks were tested for the Lyme disease bacterium, Borrelia burgdorferi sensu lato (Bbsl), using PCR and the flagellin (flaB) gene, and 14 (42%) of 33 of blacklegged tick nymphs tested were positive. In contrast, larval and nymphal H. leporsipalustris ticks were negative for Bbsl. The occurrence of Bbsl in I. scapularis nymphs brings to light the presence of a Lyme disease endemic area at this songbird nesting locality. Because our findings denote that this area is a Lyme disease endemic area, and I. scapularis is a human-biting tick, local residents and outdoor workers must take preventive measures to avoid tick bites. Furthermore, local healthcare practitioners must include Lyme disease in their differential diagnosis.

Borrelia burgdorferi sensu lato infecting Ixodes auritulus ticks in Uruguay

In the southern cone of South America different haplotypes of Borrelia burgdorferi sensu lato (Bbsl) have been detected in Ixodes spp. from Argentina, southern Brazil, Chile, and Uruguay. So far, Lyme borreliosis has not been diagnosed in Uruguay and the medical relevance of the genus Ixodes in South America is uncertain. However, the growing number of new genospecies of Bbsl in the southern cone region and the scarce information about its pathogenicity, reservoirs and vectors, highlights the importance of further studies about spirochetes present in Uruguay and the region. The aim of this study was to determine the presence of Bbsl in Ixodes auritulus ticks collected from birds and vegetation in two localities of southeastern Uruguay. In total 306 I. auritulus were collected from 392 passerine birds sampled and 1110 ticks were collected by flagging in vegetation. Nymphs and females were analyzed for Borrelia spp. by PCR targeting the flagellin (fla) gene and the rrfA-rrlB intergenic spacer region (IGS). The phylogenetic analysis of Borrelia spp. positive samples from passerine birds and vegetation revealed the presence of four fla haplotypes that form a clade within the Bbsl complex. They were closely related to isolates of Borrelia sp. detected in I. auritulus from Argentina and Canada.

Detection and Transstadial Passage of Babesia Species and Borrelia burgdorferi Sensu Lato in Ticks Collected from Avian and Mammalian Hosts in Canada

Lyme disease and human babesiosis are the most common tick-borne zoonoses in the Temperate Zone of North America. The number of infected patients has continued to rise globally, and these zoonoses pose a major healthcare threat. This tick-host-pathogen study was conducted to test for infectious microbes associated with Lyme disease and human babesiosis in Canada. Using the flagellin (flaB) gene, three members of the Borrelia burgdorferi sensu lato (Bbsl) complex were detected, namely a Borrelia lanei-like spirochete, Borrelia burgdorferi sensu stricto (Bbss), and a distinct strain that may represent a separate Bbsl genospecies. This novel Bbsl strain was detected in a mouse tick, Ixodes muris, collected from a House Wren, Troglodytes aedon, in Quebec during the southward fall migration. The presence of Bbsl in bird-feeding larvae of I. muris suggests reservoir competency in three passerines (i.e., Common Yellowthroat, House Wren, Magnolia Warbler). Based on the 18S ribosomal RNA (rRNA) gene, three Babesia species (i.e., Babesia divergens-like, Babesia microti, Babesia odocoilei) were detected in field-collected ticks. Not only was B. odocoilei found in songbird-derived ticks, this piroplasm was apparent in adult questing blacklegged ticks, Ixodes scapularis, in southern Canada. By allowing live, engorged ticks to molt, we confirm the transstadial passage of Bbsl in I. muris and B. odocoilei in I. scapularis. Bbss and Babesia microti were detected concurrently in a groundhog tick, Ixodes cookei, in Western Ontario. In Alberta, a winter tick, Dermacentor albipictus, which was collected from a moose, Alces alces, tested positive for Bbss. Notably, a B. divergens-like piroplasm was detected in a rabbit tick, Haemaphysalis leporispalustris, collected from an eastern cottontail in southern Manitoba; this Babesia species is a first-time discovery in Canada. This rabbit tick was also co-infected with Borrelia lanei-like spirochetes, which constitutes a first in Canada. Overall, five ticks were concurrently infected with Babesia and Bbsl pathogens and, after the molt, could potentially co-infect humans. Notably, we provide the first authentic report of I. scapularis ticks co-infected with Bbsl and B. odocoilei in Canada. The full extent of infectious microorganisms transmitted to humans by ticks is not fully elucidated, and clinicians need to be aware of the complexity of these tick-transmitted enzootic agents on human health. Diagnosis and treatment must be administered by those with accredited medical training in tick-borne zoonosis.

Presence of Babesia odocoilei and Borrelia burgdorferi Sensu Stricto in a Tick and Dual Parasitism of Amblyomma inornatum and Ixodes scapularis on a Bird in Canada

Wild birds transport ticks into Canada that harbor a diversity of zoonotic pathogens. However, medical practitioners often question how these zoonotic pathogens are present in their locality. In this study, we provide the first report of an Amblyomma inornatum tick cofeeding with a blacklegged tick, Ixodes scapularis, which parasitized a Veery, Catharus fuscescens—a neotropical songbird. Using the flagellin (flaB) gene of the Lyme disease bacterium, Borrelia burgdorferi sensu lato, and the 18S rRNA gene of the Babesia piroplasm, a malaria-like microorganism, we detected Borrelia burgdorferi sensu stricto and Babesia odocoilei, respectively, in an I. scapularis nymph. After the molt, these ticks can bite humans. Furthermore, this is the first documentation of B. odocoilei in a tick parasitizing a bird. Our findings substantiate the fact that migratory songbirds transport neotropical ticks long distances, and import them into Canada during northward spring migration. Health care practitioners need to be aware that migratory songbirds transport pathogen-laden ticks into Canada annually, and pose an unforeseen health risk to Canadians.

Extensive Distribution of the Lyme Disease Bacterium, Borrelia burgdorferi Sensu Lato, in Multiple Tick Species Parasitizing Avian and Mammalian Hosts across Canada

Lyme disease, caused by the spirochetal bacterium, Borrelia burgdorferi sensu lato (Bbsl), is typically transmitted by hard-bodied ticks (Acari: Ixodidae). Whenever this tick-borne zoonosis is mentioned in medical clinics and emergency rooms, it sparks a firestorm of controversy. Denial often sets in, and healthcare practitioners dismiss the fact that this pathogenic spirochetosis is present in their area. For distribution of Bbsl across Canada, we conducted a 4-year, tick–host study (2013–2016), and collected ticks from avian and mammalian hosts from Atlantic Canada to the West Coast. Overall, 1265 ticks representing 27 tick species belonging to four genera were collected. Of the 18 tick species tested, 15 species (83%) were positive for Bbsl and, of these infected ticks, 6 species bite humans. Overall, 13 of 18 tick species tested are human-biting ticks. Our data suggest that a 6-tick, enzootic maintenance cycle of Bbsl is present in southwestern B.C., and five of these tick species bite humans. Biogeographically, the groundhog tick, Ixodes cookei, has extended its home range from central and eastern Canada to southwestern British Columbia (B.C.). We posit that the Fox Sparrow, Passerella iliaca, is a reservoir-competent host for Bbsl. The Bay-breasted Warbler, Setophaga castanea, and the Tennessee Warbler, Vermivora peregrina, are new host records for the blacklegged tick, Ixodes scapularis. We provide the first report of a Bbsl-positive Amblyomma longirostre larva parasitizing a bird; this bird parasitism suggests that a Willow Flycatcher is a competent reservoir of Bbsl. Our findings show that Bbsl is present in all provinces, and that multiple tick species are implicated in the enzootic maintenance cycle of this pathogen. Ultimately, Bbsl poses a serious public health contagion Canada-wide.