Utah Plant Pest Diagnostic Lab
Tick Survey
Reason for Survey
Since the initial diagnosis, Lyme disease has climbed to the top of the vector-borne diseases list in the US (Bacon et. al, 2008), affecting over 274,268 Americans between 1995 and 2009 primarily in the northeastern US (Center for Disease Control, 2011). In recent years Utah has received an average of eight Lyme disease cases per year, however, none of these cases are believed to have originated in Utah, but are due to out-of-state travel to areas where Lyme disease naturally occurs. In 2010, a few residents from Lehi, Utah were associated with a potential Lyme disease cluster (Utah Department of Epidemiology, 2010), prompting the Utah County Health Department (UCHD) and the Utah Department of Health (UDOH) to form a task force to examine the validity of these Lyme disease cases. UDOH and Utah State University (USU) are interested in understanding the prevalence of Lyme disease and it's tick vector (the western black-legged tick) in Utah. Money provided by Utah State University Extension, the Center for Disease Control, and the Utah Bureau of Epidemiology are funding the tick survey for 1 year. To date, the findings of the task force have yielded no confirmed cases of Lyme disease originating in Utah.
Female western black-legged tick (Ixodes pacificus) tick collected in Harker Canyon, Tooele County. Jared Kunz, USU.
Survey Plan and Sites
Sites were selected based on their suitability as tick habitat. Prime habitat includes areas along forest/field edges, in low-lying river basins, or along game trails where hosts (e.g. rodents and deer) are abundant or frequently travel. These areas were selected using GIS host distribution and vegetation data provided by the Utah Division of Wildlife Habitat, areas of prior Ixodes pacificus collection, visual inspection, and on the recommendations of county Extension agents, state and federal wildlife or forest employees, and citizens. In spring/summer 2011, tick collection was focused in Utah and Tooele Counties. With additional funding from the CDC and the Utah Bureau of Epidemiology, the survey was expanded to Washington and Juab counties in the Fall of 2011. To view site pictures and descriptions for surveyed areas in 2011 click here. A map of sites surveyed in 2011 is below. (Images of sites surveyed after July 22 have not yet been added to this page). Fifty-one sites were surveyed in 2011.
Map of collection sites in Utah,Tooele, Juab and Washington Counties in 2011.
Sites surveyed for ticks in northern UT, 2011. Red marks indicate locations where ticks were found. The two red marks near Dutch Peak in the SW corner of the map (Tooele Co.) are where western black-legged ticks (Ixodes pacificus) were found.
Sites surveyed in southern UT in 2011. Red marks indicate locations where ticks were found. The northern red mark SW of Enterprise is where 2 western black-legged ticks (Ixodes pacificus) were found.
Ticks were collected using a 1 x 1.25m white flannel cloth (“flag”) with a dowel rod attached to the anterior end using staples, and a chain hemmed into the posterior end. Rope was attached to the protruding ends of the dowel rod and the flag was dragged over vegetation where there were suspected questing tick populations. Questing ticks that adhered to the flag were collected from the flag using forceps, and stored in individual vials containing 70% ethyl alcohol for identification and testing at a later date.
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| Jared Kunz constructs tick drag. | Finished tick drag. | Jared Kunz drags for ticks at Harker Cn. |
All ticks were identified using a light stereoscope. After identification, the DNA was extracted from Ixodes pacificus ticks using a Qiagen DNeasy extraction kit. The DNA was then used to perform a nested PCR technique to detect presence or absence of Borrelia burgdorferi. Finally, the PCR product will undergo DNA sequencing for further genetic analysis.
Black-Legged Tick Biology and Distribution in Utah
Ixodes pacificus is a hard tick in the family Ixodidae. The exact life cycle of Ixodes pacificus in Utah is unknown, however it follows the typical three-host tick cycle as outlined by Sonenshine (1991). Adult females take a blood meal from a large invertebrate host (e.g. deer, canine, human), drop to the ground, mate, and lay eggs. Feeding of the adult female may occur in fall or spring, or when conditions are appropriate. Upon egg hatch, six-legged larvae emerge and search for small invertebrate hosts (e.g. rodents, lizards). If a host islocated, a blood meal may be taken over several days. Fed larvae drop and molt into eight-legged nymphs, which quest for hosts in fall, or the following spring. Nymphs that successfully feed will molt to adults, which feed in fall, or spring of the following year. Feeding is mandatory for reproduction and molting between developmental stages. The life cycle in Utah likely takes two to three years to complete as it does in northern California (Padgett and Lane, 2001).
Tick activity and development depend on environmental factors such as habitat type, temperature, and humidity (Padgett and Lane, 2001; Eisen, et al., 2002; Eisen et al., 2010). In Utah, Ixodes pacificuscan be found in varied habitats from hot, dry desert scrub, to cool, moist higher elevation coniferous forests (Allred et al., 1960). The location and timing of Ixodes pacificus activity, in addition to host preference, can be extrapolated from historic tick collection data (Allred et al. 1960) (see map below). In Utah, Ixodes pacificus ticks have been collected from Beaver, Juab, Millard, Tooele, and Washington counties, but most frequently from Utah County, our targeted collection area. Collection dates for Ixodes pacificus in Utah range from April to November. Allred (1960) reports larvae and nymphs from April and July, adult males and females in July and October, and adult females also in November. In general, we expect that ticks in hotter, arid parts of the state (e.g. Washington County) to reach peak activity in April and May, and ticks at higher elevations (e.g. Provo Canyon in Utah County) to be active from May through July. Ticks at all geographical locations can be active in the fall when temperatures cool and moisture increases. In Utah, ticks were collected from hosts such as: mule deer (Odocoileus hemionus), humans (Homo sapiens), cactus mouse (Peromyscus eremicus), deer mouse (Peromyscus maniculatus), pinyon mouse (Peromyscus truei), magpie (Pica hudsonia), and dogs (Canis familiaris).
