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Review of Ticks Infesting Humans in the US

(Top-L) Adult Female deer tick, adult female dog tick.(Bottom-L) Adult female, adult male, and nymph lone star ticks. Credit J. Occi, PhD (cand.), Rutgers

Ticks and Tick-Borne Diseases, (Lars E.), published a review article “Tick species infesting humans in the United States” in November, 2022*.  The author presents data as a summary table for published records of bites, diseases, and infestations of ticks on humans in the United States (US) to date. The goal of this review is to present data for both native and recently established hard and soft tick species that have been reported on humans regarding the frequency that they have been observed. The author also states that this type of long-term data regarding human/tick encounters is lacking for the public at the national scale, and he provides guidance for future reporting to better track these encounters and the risks. * Version of Record 13 August 2022.

The author found published records that document 36 hard tick species (234,722 specimens) and 13 soft tick species (230 specimens) that have bitten or infested humans in the US to date. Data shows that the top 5 hard tick human encounters were with the blacklegged tick (Ixodes scapularis); the lone star tick (Amblyomma americanum); the American dog tick (Dermacentor variabilis); the western blacklegged tick, (Ixodes pacificus); and the Rocky Mountain wood tick (Dermacentor andersoni).

The most frequently recorded soft tick human encounters were with the spinose ear tick (Otobius megnini); and the pajaroello tick (Ornithodoros coriaceus).

Additional species of note documented by more than 250 encounters with humans included the woodchuck tick (Ixodes cookei); the Pacific Coast tick (Dermacentor occidentalis); the brown dog tick (Rhipicephalus sanguineus sensu lato); the winter tick (Dermacentor albipictus); and the Gulf Coast tick (Amblyomma maculatum).

Interestingly, some ticks widely believed to be “non-human biters” or “nidicolous” in behavior (staying close to the host nest or burrow), were reported from over 100 to over 200 instances, and are species that are known to be competent vectors of Borrelia burgdorferi s.s. bacteria. These ticks included Ixodes muris, Ixodes dentatus, Ixodes angustus, and Ixodes spinipalpis.

 


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