The invasion and establishment of new arthropod vectors may lead to the introduction of new pathogenic threats to wildlife, humans, and domestic animals . New vector invasions and geographic expansion from historical ranges have been attributed to climate and anthropogenic land use changes, geographic distribution and abundance of host species, an increase in global travel, and importations of exotic animals [2, 3]. Vector invasions and range expansions may lead to changes in ecological characteristics including competition with and displacement of native species . Ticks with a generalist feeding behavior may be more likely to expand their ranges when they feed on host species with wide distribution ranges such as migratory birds and large mammals . However, the potential for invasive tick species to transmit novel or native infectious diseases remains relatively unpredictable without laboratory and field experiments.
A recent invasive species in the US is the Asian longhorned tick, Haemaphysalis longicornis, which was first documented from New Jersey in 2017, however misidentified specimens have been reported from West Virginia in 2010, and it has rapidly spread across 15 states in the eastern US [6, 7]. Additionally, predictive models suggest the range of H. longicornis will continue expanding westward . In some regions of its invasive range in the US, H. longicornis has been found to be PCR positive for various pathogens including introduced (e.g. Theileria orientalis) and native (e.g. Borrelia burgdorferi) species [9, 10]. In laboratory studies, H. longicornis were found to be competent vectors of Rickettsia rickettsii , but were not competent to transmit B. burgdorferi  or Anaplasma phagocytophilum . While humans may not be a preferred host for H. longicornis  the incidence of this tick species feeding on humans in the US is increasing .
The red sheep tick, Haemaphysalis punctata, is native to the Palearctic region (including southern Europe, southwest Asia, and North Africa) and generally feeds on avian, small mammal, ungulate, and human hosts . They are known vectors of several pathogens of human health concern in the same genera as native US pathogens including Babesia spp., Brucella spp., Rickettsia spp., Theileria spp., and several viruses (Tick-borne encephalitis, Crimean-Congo haemorrhagic fever, etc.) . Furthermore, the red sheep tick has been expanding in its native range; exposing more humans to the pathogens it transmits .
The spread of endemic vectors has resulted in an increase in the incidence of human tick-borne diseases, which comprise over 90% of all reportable vector-borne diseases in the US . In recent years, certain native tick species have expanded their geographic distribution such as A. americanum the lone star tick [3, 19], and Haemaphysalis leporispalustris, the rabbit tick . Lone star ticks transmit several pathogens of human and veterinary concern such as Ehrlichiosis, Tularemia, Heartland viruses and have been associated with the red meat allergy and Southern tick-associated rash illness (STARI), which produces rashes similar to Lyme disease . While rabbit ticks do not commonly feed on humans, they are known vectors of R. rickettsii (agent of Rocky Mountain spotted fever), Coxiella burnetii (an agent of Q fever), and Francisella tularensis (causative agent of tularemia) . These native vector range expansions are cause for public and veterinary health concern because of the potential pathogen expansion into new regions.
Here, we report the first known invasion and establishment of H. punctata in the western hemisphere and in the US and on the discovery of H. longicornis in the state of Rhode Island. Additionally, we report on the geographic range expansion of native tick species A. americanum and H. leporispalustris to a new region in the US. Block Island, RI is an island approximately 14 km south of the mainland and consisting of a 25.2 km2 land mass and is dominated by Ixodes scapularis, the blacklegged tick, native and migratory bird species, and a low diversity of mammals (white-footed mice, the Block Island meadow vole, and white-tailed deer). Few residents remain on the island year-round (n < 1000), but the population drastically increases in the summer months from tourists and seasonal residents (n ≈ 12,000) . The host composition and high annual influx of humans make Block Island an ideal location for studying vector invasion events, pathogen prevalence and diversity, and public health risk of tick-borne pathogens.