Passive surveillance of human-biting ticks correlates with town-level disease rates in Massachusetts

Abstract

AbstractWe assessed the temporal and spatial distribution of Borrelia burgdorferi, Borrelia miyamotoi, Babesia microti, and Anaplasma phagocytophilum among human-biting Ixodes scapularis ticks in Massachusetts using ticks submitted to the TickReport pathogen passive surveillance program. From January 2015 to December 2017, Ixodes scapularis was the most frequently submitted tick species (n=7462). B. burgdorferi prevalence increased in ticks during the study period in adults and nymphs (37.1-39.1% in adults, 19.0%-23.9% in nymphs). The proportion of B. microti infected ticks increased from 5.7% to 8.1% in adult ticks but remained constant in nymphs (5.4-5.6%). Stable or decreasing annual prevalence of B. miyamotoi (2.2 – 2.2% in adults, 1.0-1.9% in nymphs) and A.phagocytophilum (7.6-7.2% in adults, 5.0-4.0% in nymphs) were detected. Coinfections were observed and included all pathogen combinations.Ticks were submitted year-round and had stable infection rates. The temporal pattern of B. burgdorferi- positive nymphs aligned with reported cases of Lyme disease, as did positive B. microti nymphs and babesiosis. A similar situation is seen with B. miyamotoi with an insignificant fall peak in cases. Anaplasmosis demonstrated a significant bimodal distribution with reported cases peaking in the spring and fall. This pattern is similar to that of A. phagocytophilum-infected adult ticks.B. microti infected nymphs were significantly predictive of town-level babesiosis incidence and A. phagocytophilum infected adults were significantly predictive of town-level anaplasmosis incidence in a spatially adjusted negative binomial model. Unlike field collection studies, the high number of ticks submitted provides a high-resolution picture of pathogen prevalence and provides data relevant to human health at the town level. Through temporal and geographic analyses we demonstrate concordance between our passive surveillance tick pathogen data and state reports of tickborne disease.