What is the Risk for Exposure to Vector-Borne Pathogens in United States National Parks?

Abstract

United States national parks attract Ͼ275 million visitors annually and collectively present risk of exposure for staff and visitors to a wide range of arthropod vector species (most notably ßeas, mosquitoes, and ticks) and their associated bacterial, protozoan, or viral pathogens. We assessed the current state of knowledge for risk of exposure to vector-borne pathogens in national parks through a review of relevant literature, including internal National Park Service documents and organismal databases. We conclude that, because of lack of systematic surveillance for vector-borne pathogens in national parks, the risk of pathogen exposure for staff and visitors is unclear. Existing data for vectors within national parks were not based on systematic collections and rarely include evaluation for pathogen infection. Extrapolation of human-based surveillance data from neighboring communities likely provides inaccurate estimates for national parks because landscape differences impact transmission of vector-borne pathogens and human-vector contact rates likely differ inside versus outside the parks because of differences in activities or behaviors. Vector-based pathogen surveillance holds promise to deÞne when and where within national parks the risk of exposure to infected vectors is elevated. A pilot effort, including 5Ð10 strategic national parks, would greatly improve our understanding of the scope and magnitude of vector-borne pathogen transmission in these high-use public settings. Such efforts also will support messaging to promote personal protection measures and inform park visitors and staff of their responsibility for personal protection, which the National Park Service preservation mission dictates as the core strategy to reduce exposure to vector-borne pathogens in national parks.

Novel Focus of Sin Nombre Virus inPeromyscus eremicusMice, Death Valley National Park, California, USA

“…These findings underscore the importance of rodent exclusion and management in and around rural and semirural buildings where risk for contact between rodents and humans is high, even in the absence of P. maniculatus mice ( 9 , 15 ). Park leadership and staff were notified of our study results and given training on hantavirus awareness and prevention, and hantavirus pamphlets were made available for visitors to the park.…”

“…The ultimate objective was to assess potential occupational risk to staff and incidental risk to visitors in a highly visited geographic area of the state that was previously unstudied ( 8 , 9 ). …”

Prevalence and Diversity of Tick-Borne Pathogens in NymphalIxodes scapularis(Acari: Ixodidae) in Eastern National Parks

“…Assessing when and where people are at highest risk for exposure to vectors and what pathogens are present in those vectors are primary steps in risk assessment and prevention (Piesman and Eisen 2008, Eisen et al 2013). In this study, we documented acarological risk for exposure to I. scapularis- borne pathogens on frequently used hiking trails in nine eastern national parks, but we observed great variability in acarological risk within and among parks.…”

“…To reduce vector-borne disease exposures, national parks focus on encouraging visitors to use appropriate personal protective measures. Strategies include informing visitors when and where they are at highest risk, which pathogens are present and what symptoms result from infection (National Park Service 2006, Piesman and Eisen 2008, Eisen et al 2013), and providing guidance on personal protective measures to prevent tick bite (http://www.cdc.gov/ticks/avoid/on_people.html) (accessed July 2016), the importance of prompt and safe removal of attached ticks (http://www.cdc.gov/ticks/removing_a_tick.html) (accessed July 2016) and seeking medical attention if signs and symptoms occur after being bitten by a tick (http://www.cdc.gov/ticks/symptoms.html) (accessed July 2016). Promoting prevention efforts in these areas may be particularly important for those visitors traveling from nonendemic areas that may not be as mindful to the prevention of tick bites or symptoms of tick-borne diseases.…”

“…Regardless of geographic region, previous studies have demonstrated a risk of human exposure to infected host-seeking I. scapularis nymphs in recreational settings (Falco and Fish 1989, Schulze et al 1992, Oliver and Howard 1998, Paskewitz et al 2001, Han et al 2014, Prusinski et al 2014, Ford et al 2015). National parks are popular recreation destinations and may represent areas of elevated acarological risk, yet one cannot adequately infer the risk of tick-borne disease for park visitors or employees from the epidemiological surveillance conducted at the county spatial scale (Eisen et al 2013). National parks often vary ecologically from surrounding areas, and thus the density of infected ticks may differ between settings; further, human behavior within the parks may differ from behavior in surrounding communities.…”