Last data update: May 06, 2024. (Total: 46732 publications since 2009)
Records 1-3 (of 3 Records) |
Query Trace: Lynn GE[original query] |
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A comparison of horizontal and transovarial transmission efficiency of Borrelia miyamotoi by Ixodes scapularis
Lynn GE , Breuner NE , Hojgaard A , Oliver J , Eisen L , Eisen RJ . Ticks Tick Borne Dis 2022 13 (5) 102003 Borrelia miyamotoi is a relapsing fever spirochete carried by Ixodes spp. ticks throughout the northern hemisphere. The pathogen is acquired either transovarially (vertically) or horizontally through blood-feeding and passed transtadially across life stages. Despite these complementary modes of transmission, infection prevalence of ticks with B. miyamotoi is typically low (<5%) in natural settings and the relative contributions of the two transmission modes have not been studied extensively. Horizontal transmission of B. miyamotoi (strain CT13-2396 or wild type strain) was initiated using infected Ixodes scapularis larvae or nymphs to expose rodents, which included both the immunocompetent CD-1 laboratory mouse (Mus musculus) and a natural reservoir host, the white-footed mouse (Peromyscus. leucopus), to simulate natural enzootic transmission. Transovarial transmission was evaluated using I. scapularis exposed to B. miyamotoi as either larvae or nymphs feeding on immunocompromised SCID mice (M. musculus) and subsequently fed as females on New Zealand white rabbits. Larvae from infected females were qPCR-tested individually to assess transovarial transmission rates. Tissue tropism of B. miyamotoi in infected ticks was demonstrated using in situ hybridization. Between 1 and 12% of ticks were positive (post-molt) for B. miyamotoi after feeding on groups of CD-1 mice or P. leucopus with evidence of infection, indicating that horizontal transmission was inefficient, regardless of whether infected larvae or nymphs were used to challenge the mice. Transovarial transmission occurred in 7 of 10 egg clutches from infected females. Filial infection prevalence in larvae ranged from 3 to 100% (median 71%). Both larval infection prevalence and spirochete load were highly correlated with maternal spirochete load. Spirochetes were disseminated throughout the tissues of all three stages of unfed ticks, including the salivary glands and female ovarian tissue. The results indicate that while multiple transmission routes contribute to enzootic maintenance of B. miyamotoi, transovarial transmission is likely to be the primary source of infected ticks and therefore risk assessment and tick control strategies should target adult female ticks. |
An immunocompromised mouse model to infect Ixodes scapularis ticks with the relapsing fever spirochete, Borrelia miyamotoi
Lynn GE , Breuner NE , Eisen L , Hojgaard A , Replogle AJ , Eisen RJ . Ticks Tick Borne Dis 2018 10 (2) 352-359 The hard tick-borne relapsing fever spirochete, Borrelia miyamotoi, has recently gained attention as a cause of human illness, but fundamental aspects of its enzootic maintenance are still poorly understood. Challenges to experimental studies with B. miyamotoi-infected vector ticks include low prevalence of infection in field-collected ticks and seemingly inefficient horizontal transmission from infected immunocompetent rodents to feeding ticks. To reliably produce large numbers of B. miyamotoi-infected ticks in support of experimental studies, we developed an animal model where immunocompromised Mus musculus SCID mice were used as a source of B. miyamotoi-infection for larval and nymphal Ixodes scapularis ticks. Following needle inoculation with 1 × 105 spirochetes, the SCID mice developed a high spirochetemia (greater than 1 × 107 copies of B. miyamotoi purB per mL of blood) that persisted for at least 30 d after inoculation. In comparison, immunocompetent M. musculus CD-1 mice developed transient infections, detectable for only 2–8 d within the first 16 d after needle inoculation, with a brief, lower peak spirochetemia (8.5 × 104 – 5.6 × 105 purB copies per mL of blood). All larval or nymphal ticks fed on infected SCID mice acquired B. miyamotoi, but frequent loss of infection during the molt led to the proportion infected ticks of the resulting nymphal or adult stages declining to 22–29%. The ticks that remained infected after the molt had well-disseminated infections which then persisted through successive life stages, including transmission to larval offspring. |
Prevalence and geographic distribution of Borrelia miyamotoi in host-seeking Ixodes pacificus (Acari: Ixodidae) nymphs in Mendocino County, California
Lynn GE , Graham CB , Horiuchi K , Eisen L , Johnson TL , Lane RS , Eisen RJ . J Med Entomol 2018 55 (3) 711-716 Borrelia miyamotoi is an increasingly recognized human pathogen transmitted by Ixodes ticks in the Northern Hemisphere. In North America, infection prevalences of B. miyamotoi are characteristically low (<10%) in Ixodes scapularis (Say; Acari: Ixodidae) and Ixodes pacificus (Cooley & Kohls; Acari: Ixodidae), both of which readily bite humans. We tested 3,255 host-seeking I. pacificus nymphs collected in 2004 from 79 sites throughout Mendocino County in north-coastal California for presence of B. miyamotoi. The collection sites represented a variety of forest types ranging from hot, dry oak woodlands in the southeast, to coastal redwoods in the west, and Ponderosa pine and Douglas fir-dominated areas in the northern part of the county. We found that B. miyamotoi was geographically widespread, but infected I. pacificus nymphs infrequently (cumulative prevalence of 1.4%). Infection prevalence was not significantly associated with geographic region or woodland type, and neither density of host-seeking nymphs, nor infection with Borrelia burgdorferi sensu stricto was associated with B. miyamotoi infection status in individual ticks. Because B. burgdorferi prevalence at the same sites was previously associated with woodland type and nymphal density, our results suggest that despite sharing a common vector, the primary modes of enzootic maintenance for the two pathogens are likely different. |
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