| Abstrakt: |
Measures of acarological risk of exposure to Ixodes scapularis-borne disease agents typically focus on nymphs; however, the relapsing fever group spirochete Borrelia miyamotoican be passed transovarially, and I. scapularislarvae are capable of transmitting B. miyamotoito their hosts. To quantify the larval contribution to acarological risk, relative to nymphs and adults, we collected questing I. scapularisfor 3 yr at Fort McCoy, Wisconsin (WI, n = 23,367 ticks), and Cape Cod, Massachusetts (MA, n = 4190) in the United States. Borrelia miyamotoiinfection prevalence was estimated for I. scapularislarvae, nymphs, females, and males, respectively, as 0.88, 2.05, 0.63, and 1.22 % from the WI site and 0.33, 2.32, 2.83, and 2.11 % from the MA site. Densities of B. miyamotoi-infected ticks (DIT, per 1000 m2) were estimated for larvae, nymphs, females, and males, respectively, as 0.36, 0.14, 0.01, and 0.03 from the WI site and 0.05, 0.06, 0.03, and 0.02 from the MA site. Thus, although larval infection prevalence with B. miyamotoiwas significantly lower than that of nymphs and similar to that of adults, because of their higher abundance, the larval contribution to the overall DIT was similar to that of nymphs and trended towards a greater contribution than adults. Assuming homogenous contact rates with humans, these results suggest that eco-epidemiological investigations of B. miyamotoidisease in North America should include larvae. A fuller appreciation of the epidemiological implications of these results, therefore, requires an examination of the heterogeneity in contact rates with humans among life stages. |
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