Preliminary Evaluation of Human Personal Protective Measures Against the Nymphal Stage of the Asian Longhorned Tick (Acari: Ixodidae).

The invasive, human-biting Asian longhorned tick, Haemaphysalis longicornis Neumann, is establishing in the United States. This tick is a threat to public health in its native range in Asia, serving as a vector of severe fever with thrombocytopenia syndrome virus and Rickettsia japonica, the agent of Japanese spotted fever. However, there is a lack of published information specifically for H. longicornis concerning the efficacy of generally recommended personal tick bite prevention measures. We, therefore, evaluated permethrin-treated clothing and formulated human skin repellent products, representing the six repellent active ingredients generally recommended for tick bite prevention by the Centers for Disease Control and Prevention (CDC), against H. longicornis nymphs from a colony established with adult ticks collected in New York state. Reluctance of H. longicornis nymphs to stay in contact with nontreated human skin precluded the use of a human skin bioassay to optimally evaluate repellency. In a Petri dish choice bioassay, all tested product formulations were highly effective with estimated repellencies ranging from 93 to 97%. In addition, we observed strong contact irritancy of a summer-weight permethrin-treated garment against H. longicornis nymphs, with 96% of introduced ticks dislodging from the vertically oriented textile within 3 min. These preliminary studies indicate that personal tick bite prevention measures currently recommended by the CDC are effective against the invasive H. longicornis. However, additional studies are needed to explore the efficacy of the evaluated products against different life stages of H. longicornis, as well as ticks collected in the field rather than reared in the laboratory.