Assessing Surveillance, Density, and Pathogens in the Ticks of Shelter Island, New York

Abstract

Shelter Island, New York is a 32 km2 island off Long Island that has many opportunities for outdoor recreation, and its large lot sizes preserve green spaces among housing. Located in Suffolk County, it has a high rate of tick-borne diseases, and habitat for several tick species that can transmit pathogens to humans. The island has a history of tick surveillance, a now defunct four-poster program, and performs regular white-tailed deer culling. Despite this, tick densities and pathogen prevalence are not well understood. A surveillance program was undertaken in the summer of 2020 to sample seven sites, 4 on Mashomack Preserve, and 3 in other areas of Shelter Island. Surveillance with drags cloths was performed once weekly for a period of eight weeks. Four medically important tick species were collected. Ixodes scapularis and Amblyomma americanum were the most abundant species. Dermacentor variablis was also present, but rare. Additionally, a single specimen of Haemaphysalis longicornis was collected, marking the first confirmed record of this invasive species on Shelter Island. Density of nymphs was determined for the two most abundant species, and pathogen testing was conducted on a subset (10%) of tick samples. A small number (7.41%) of tested I. scapularis were positive for Anaplasma phagocytophilum and Babesia microti, and 3.41% were positive for Borrelia burgdorferi and Babesia. miyamotoi. This result was lower than reported B. burgdorferi infection rates for I. scapularis collected from other locations in Suffolk County. No pathogens were detected in A. americanum, but over half (55.81%) were positive for a rickettsiae endosymbiont (Rickettsia spp.) that is not known to be pathogenic to humans and animals. Study results and recommendations for future surveillance and public education on risk and tick bite prevention were developed and submitted to Shelter Island and Mashomack Preserve officials. The presence of pathogens and a new invasive tick species on the island indicate the importance of continued surveillance and testing.