Multi-County Tick Survey (Acari: Ixodidae) in Missouri Usa, 2019 and 2021

Ongoing surveillance of tick populations is critical for informing the health of humans, livestock, and companion animals. From 2004 to 2019 in the USA and its territories, the National Notifiable Disease Surveillance System data show a 2.1-fold increase in all reportable notifiable tick-borne diseases (TBDs) in humans. Eight tick-borne zoonotic pathogens and 1 syndrome were described for the first time in the USA between 2004 and 2024. In Missouri, 33 counties were surveyed over a 2-year period (2019 and 2021). More than 3,811 ticks were collected during the study: 89.0% Amblyomma americanum, 10.9% Dermacentor variabilis, <0.1% Amblyomma maculatum, <0.1% Haemaphysalis longicornus, and <0.1% Ixodes spp. Significantly greater tick density was found in metropolitan areas as compared to rural counties (P = 0.012). Of the 2 level I ecoregions in Missouri, the Eastern Temperate Forest (ETF) had a significantly greater tick density (P = 0.0045). Even so, D. variabilis had significantly higher density in the Great Plains ecoregion than in ETF (P = 0.031). Ozark Highlands had the highest tick density of the 5 level III ecoregions surveyed (5.12 ticks/100 m2). A moderate, positive correlation between a county's density of A. americanum nymphs and its quadrennial tick-borne disease rate was observed (r = 0.68, P = 0.002). Our study adds new data on established and reported tick populations for 13 counties and examines the relationships of tick density to TBDs and to area designation.