Large Scale Spatial Risk and Comparative Prevalence of Borrelia miyamotoi and Borrelia burgdorferi Sensu Lato in Ixodes pacificus (original) (raw)
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Applied and Environmental Microbiology, 2009
Factors potentially contributing to the lower incidence of Lyme borreliosis (LB) in the far-western than in the northeastern United States include tick host-seeking behavior resulting in fewer human tick encounters, lower densities of Borrelia burgdorferi-infected vector ticks in peridomestic environments, and genetic variation among B. burgdorferi spirochetes to which humans are exposed. We determined the population structure of B. burgdorferi in over 200 infected nymphs of the primary bridging vector to humans, Ixodes pacificus, collected in Mendocino County, CA. This was accomplished by sequence typing the spirochete lipoprotein ospC and the 16S-23S rRNA intergenic spacer (IGS). Thirteen ospC alleles belonging to 12 genotypes were found in California, and the two most abundant, ospC genotypes H3 and E3, have not been detected in ticks in the Northeast. The most prevalent ospC and IGS biallelic profile in the population, found in about 22% of ticks, was a new B. burgdorferi strain defined by ospC genotype H3. Eight of the most common ospC genotypes in the northeastern United States, including genotypes I and K that are associated with disseminated human infections, were absent in Mendocino County nymphs. ospC H3 was associated with hardwood-dominated habitats where western gray squirrels, the reservoir host, are commonly infected with LB spirochetes. The differences in B. burgdorferi population structure in California ticks compared to the Northeast emphasize the need for a greater understanding of the genetic diversity of spirochetes infecting California LB patients.
Ecology of Ixodes pacificus Ticks and Associated Pathogens in the Western United States
Pathogens, 2022
Lyme disease is the most important vector-borne disease in the United States and is increasing in incidence and geographic range. In the Pacific west, the western black-legged tick, Ixodes pacificus Cooley and Kohls, 1943 is an important vector of the causative agent of Lyme disease, the spirochete, Borrelia burgdorferi. Ixodes pacificus life cycle is expected to be more than a year long, and all three stages (larva, nymph, and adult) overlap in spring. The optimal habitat consists of forest cover, cooler temperatures, and annual precipitation in the range of 200–500 mm. Therefore, the coastal areas of California, Oregon, and Washington are well suited for these ticks. Immature stages commonly parasitize Western fence lizards (Sceloporus occidentalis) and gray squirrels (Sciurus griseus), while adults often feed on deer mice (Peromyscus maniculatus) and black-tailed deer (Odocoileus h. columbianus). Ixodes pacificus carry several pathogens of human significance, such as Borrelia bur...
PLOS ONE, 2015
Habitat heterogeneity influences pathogen ecology by affecting vector abundance and the reservoir host communities. We investigated spatial patterns of disease risk for two human pathogens in the Borrelia genus-B. burgdorferi and B. miyamotoi-that are transmitted by the western black-legged tick, Ixodes pacificus. We collected ticks (349 nymphs, 273 adults) at 20 sites in the San Francisco Bay Area, California, USA. Tick abundance, pathogen prevalence and density of infected nymphs varied widely across sites and habitat type, though nymphal western black-legged ticks were more frequently found, and were more abundant in coast live oak forest and desert/semi-desert scrub (dominated by California sagebrush) habitats. We observed Borrelia infections in ticks at all sites where we able to collect >10 ticks. The recently recognized human pathogen, B. miyamotoi, was observed at a higher prevalence (13/349 nymphs = 3.7%, 95% CI = 2.0-6.3; 5/273 adults = 1.8%, 95% CI = 0.6-4.2) than recent studies from nearby locations (Alameda County, east of the San Francisco Bay), demonstrating that tick-borne disease risk and ecology can vary substantially at small geographic scales, with consequences for public health and disease diagnosis.
Seroepidemiology of Emerging Tickborne Infectious Diseases in a Northern California Community
The Journal of Infectious Diseases, 1997
A seroprevalence and risk factor study of emerging tickborne infectious diseases (Lyme disease, ehrlichiosis, and babesiosis) was conducted among 230 residents of a semirural community in Sonoma County, California. Over 50% of residents reported finding a tick on themselves in the preceding 12 months. Samples from 51 (23%) residents were seroreactive to antigens from one or more tickborne disease agents: 1.4% to Borrelia burgdorferi, 0.4% to Ehrlichia equi, 4.6% to Ehrlichia chaffeensis, and 17.8% to the Babesia-like piroplasm WA1. Only 14 (27%) of these seroreactive residents reported one or more symptoms compatible with these diseases. Seroreactivity was significantly associated with younger age (õ16 years), longer residence in the community (11-20 years), and having had a physician's diagnosis of Lyme disease. In northern California, the risk of infection with these emerging tickborne diseases, particularly in children, may be greater than previously recognized.
Prevalence of Borrelia miyamotoi in Ixodes Ticks in Europe and the United States
Emerging Infectious Diseases, 2014
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.
Journal of Vector Ecology
Ticks (Acari: Ixodidae) can transmit a diverse group of pathogens and are considered one of the most important arthropod vectors of human diseases, second only to mosquitoes. One of the most commonly reported tick-borne illnesses in the United States, Lyme disease, is caused by Borrelia burgdorferi sensu stricto (ss), which is transmitted by ticks in the Ixodes ricinus complex (Mead 2015). Ixodes scapularis, the blacklegged tick, is considered the primary vector of B. burgdorferi ss in the northeastern and northcentral United States and I. pacificus, the western blacklegged tick, is the primary vector in western states. In the United States alone, more than 30,000 cases of Lyme disease are reported each year but it is believed that the actual number of cases may reach as high as 300,000 (Mead 2015). In California, members of the B. burgdorferi sensu lato (sl) complex, including B. burgdorferi ss, B. americana, B. bissettiae (formerly B. bissettii), B. californiensis, B. carolinensis, and several uncharacterized genospecies have been detected in I. pacificus and mammals throughout the state (Lane et al. 2013, Foley et al. 2014, Padgett et al. 2014, Swei et al. 2015). Two pathogenic tick-borne Rickettsia species are also known to occur in California: R. rickettsii, the causative agent of Rocky Mountain spotted fever (RMSF), documented in Dermacentor species and R. philipii (formerly Rickettsia sp. 364D), likely transmitted by the
Genetics, 2002
Over 80% of reported cases of Lyme disease in the United States occur in coastal regions of northeastern and mid-Atlantic states. The genetic structure of the Lyme disease spirochete (Borrelia burgdorferi) and its main tick vector (Ixodes scapularis) was studied concurrently and comparatively by sampling natural populations of I. scapularis ticks along the East Coast from 1996 to 1998. Borrelia is genetically highly diverse at the outer surface protein ospC. Since Borrelia is highly clonal, the ospC alleles can be used to define clones. A newly designed reverse line blotting (RLB) assay shows that up to 10 Borrelia clones can infect a single tick. The clone frequencies in Borrelia populations are the same across the Northeast. On the other hand, I. scapularis populations show strong regional divergence (among northeastern, mid-Atlantic, and southern states) as well as local differentiation. The high genetic diversity within Borrelia populations and the disparity in the genetic struc...
Emerging microbes & infections, 2016
Amblyomma americanum (Linnaeus), the lone star tick, is a major human-biting tick in the eastern, southeastern and midwestern USA. 1 Because of the high population densities and increased expansion ability, its capacity to transmit multiple pathogens, and its aggressive and liberal feeding behavior, A. americanum is emerging as one of the most medically and economically significant tick vectors in the United States. 2 Involvement of A. americanum in transmission of Borrelia burgdorferi sensu lato (s.l.) spirochetes in the southeastern USA has been a subject of discussion for 430 years, and a limited number of published studies present rather conflicting results. 3-8 Although the results of Schulze et al. 7 support the possible role of A. americanum as a vector of B. burgdorferi, the latest study of Stromdahl et al. 8 did not reveal the presence of B. burgdorferi spirochetes in Amblyomma ticks. Earlier, B. burgdorferi was detected in 5.4% of A. americanum adults and in 3.4% of nymphs, collected in 1984 at a major endemic focus of Lyme disease in New Jersey. 9 Analysis of cultured pools of ticks and fleas collected by the Texas Department of Health in 1988 and 1989 resulted in isolation of B. burgdorferi from three of 354 pools of A. americanum (0.85%). 5 Later analysis of A. americanum collected in southeastern Missouri detected spirochetes in 1.9% of questing ticks using indirect fluorescent antibody tests with the monoclonal antibody H5332, followed by verification of indirect fluorescent antibody-positive organisms using PCR with two different sets of B. burgdorferi-specific primers, and by Southern blotting. 6 Attempts to define the vector competency of A. americanum were conducted in different laboratories, using geographically distant populations of this tick species and laboratory animal models. 3,4 The results revealed an interesting finding. Although an A. americanum population originated from Texas was completely refractory to infection with B. burgdorferi strain JD1 (ospC type C), specimens of the same tick species from Alabama showed overall infection rate of 5%. 3 The following experiments of Sanders and Oliver Jr 4 involved two different spirochete strains, B. burgdorferi SH2-82 (ospC type I) and MI-6, later identified as B. bissettii. Laboratory transmission of the selected strains was unsuccessful. However, for the first time, the possible