| Abstrakt: |
Borrelia miyamotoiis a relapsing fever spirochete transmitted by ticks in the Ixodes ricinuscomplex. In the eastern United States, B. miyamotoiis transmitted by I. scapularis,which also vectors several other pathogens including B. burgdorferisensu stricto. In contrast to Lyme borreliae, B. miyamotoican be transmitted vertically from infected female ticks to their progeny. Therefore, in addition to nymphs and adults, larvae can vector B. miyamotoito wildlife and human hosts. Two widely varying filial infection prevalence (FIP) estimates - 6% and 73% - have been reported previously from two vertically infected larval clutches; to our knowledge, no other estimates of FIP or transovarial transmission (TOT) rates for B. miyamotoihave been described in the literature. Thus, we investigated TOT and FIP of larval clutches derived from engorged females collected from hunter-harvested white-tailed deer in 2015 (n = 664) and 2016 (n = 599) from Maine, New Hampshire, Tennessee, and Wisconsin. After engorged females oviposited in the lab, they (n = 492) were tested for B. miyamotoiinfection by PCR. Subsequently, from each clutch produced by an infected female, larval pools, as well as 100 individual eggs or larvae, were tested. The TOT rate of the 11 infected females was 90.9% (95% CI; 57.1–99.5%) and the mean FIP of the resulting larval clutches was 84.4% (95% CI; 68.1–100%). Even though the overall observed vertical transmission rate (the product of TOT and FIP; 76.7%, 95% CI; 44.6–93.3%) was high, additional horizontal transmission may be required for enzootic maintenance of B. miyamotoibased on the results of a previously published deterministic model. Further investigation of TOT and FIP variability and the underlying mechanisms, both in nature and the laboratory, will be needed to resolve this question. Meanwhile, studies quantifying the acarological risk of Borrelia miyamotoidisease need to consider not only nymphs and adults, but larval I. scapularisas well. |
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