Amblyomma americanum (Lone star tick)

This section will provide information on Amblyomma americanum also known as the lone star tick. This tick is rarely found in Wisconsin but there are occasional reports every year, especially in the southern half of the state.   WE WELCOME SUBMISSIONS  OR DIGITAL IMAGES OF LONESTAR TICKS  COLLECTED FROM ANIMALS OR HUMANS WITHOUT A RECENT OCCURRENCE OF OUT -OF-STATE TRAVEL.  Dead lone star ticks can be placed in plastic bags or small containers for shipping.  If you have live adults, please contact me for information about shipping as we may want to preserve them differently.

“Tick swarms”.  We also welcome information about encounters with large numbers of very small ticks (immature stages), usually 20-200 within a few minutes (less than 5 minutes) on the lower body or pants.  These may attach rapidly and bites are said to be very itchy.  Removal can be facilitated through the use of duct tape or a lint roller (like those used for removal of hair and lint from clothing).  Preserve the duct tape or lint roller tape in a clear plastic bag and mail to the address below, along with the location and the contact information for the submitter.

Contact:  Dr. Susan Paskewitz, 237 Russell labs, 1630 Linden Drive, Madison Wisconsin 53706.  608-262-1269.  paskewit@entomology.wisc.edu

AMB AME MALE & FEMALEFigure 1.  Adult female (left) and male (right) lone star ticks that were collected in Wisconsin.

Amblyomma americanum female (open source image from wikipedia)

 

Distribution in the United States and Wisconsin: 

A. americanum is found west-central Texas, north to Iowa, Illinois and Michigan, and eastward up to Maine (Keirans and Lacombe 1998). It is most widely distributed in the eastern and southeastern United States (Childs & Paddock 2003; Means & White 1997).

This tick is uncommon in Wisconsin and it is unknown whether there are established, breeding populations within the state. There are occasional reports and collections every year, especially in the southern half of Wisconsin.  Reports have increased in 2013.  See the map below for a summary of these reports.

Amblyomma records 2013

Figure 2.  Records of lone star ticks in Wisconsin.  Both nymphs and adults have been collected by tick dragging in Dane County by UW Madison researchers.  Other reports derive from surveillance in collaboration with veterinary, animal rehabilitator and humane society partners or from submissions from the general public.  Data from D. Murphy, P. Pellitteri and S. Paskewitz.

Description and Identification: Amblyomma tick species are more rounded in shape versus Dermacentor and Ixodes species which have more of a tear-drop shape that tapers at the mouthparts. Adult female lone star ticks are reddish-brown in color and can be easily distinguished from other ticks by the presence of a distinctive white spot or “star” on the dorsum or back. This spot may vary in color from whitish to cream or gold to bronze and is often iridescent in appearance upon closer inspection. The spot appears closer to the mouth parts when the female has fed on an animal or human. Females are generally larger than males and average around 1/6 to 1/4 inch (4-6 mm) unfed and up 1/2 inch or larger (~16 mm or larger) when fully fed.  Adult male lone star ticks average around 1/10 to 1/4 inch (2-5 mm) in size with a body that is dark brown in color, sometimes with patches of red. In adult males, a whitish pattern may be visible along the outer margins of the lower body surface. 

Amblyomma stages

 Figure 3.  Stages of the lone star tick.  Image from the Tick Encounter Resource Center. http://www.tickencounter.org/tick_identification/lone_star_tick

 Hosts: Lone star ticks, in general, are aggressive, generalist feeders at all three life stages (larva, nymph and adult). In other words, this means the lone star tick will often actively pursue a meal and does not tend to be picky about what species of animal it gets a blood meal from.  A. americanum larvae and nymphs tend to feed on small mammals (for example, rabbits and squirrels), and ground-feeding birds as well as white-tailed deer and domestic animals.  Nymphs and larvae of the lonestar tick will often feed on humans, and can sometimes be present in large numbers.  These are sometimes called “seed ticks” in the southern USA.  It is not uncommon for a person to pick up 20 to several hundred seed ticks at a time.

A. americanum adults frequently feed on white-tailed deer (Odocoileus virginianus), domestic cattle, horses and sheep, feral swine and domestic dogs and humans (Allan et al. 2010; Childs & Paddock 2003; Kollars et al. 2000). 

Life Cycle and Biology:  Lone star ticks are three-host ixodid ticks, which means they require three separate hosts (animal or human) at each life stage (larva, nymph and adult) in order to complete their life cycle. Peak activity of each life stage varies by season. For example, peak activity of larval lone star ticks usually occurs from June to August but this may vary slightly due to climatic and geographic factors. Lone star ticks are most often found in woodland habitats, especially second-growth forests and the abundance, or numbers of A. americanum found in an area or habitat, is influenced by the availability of suitable hosts (animals or humans) for all three life stages and the availability of appropriate habitat for both the tick as well as it’s potential hosts (Childs & Paddock 2003). A. americanum is especially abundant in non-agricultural habitats which support high numbers of white-tailed deer (Mount et al. 1999).

Medical and Veterinary Significance: The lone star tick is an important vector of both human and animal tick-borne diseases but is not considered a competent vector of Borrelia burgdorferi, the bacterial agent which causes Lyme disease in humans and some domestic animals (Ledin et al. 2005; Piesman & Happ, 1997). Research suggests a possible reason why the lone star tick is not a competent vector for Lyme disease is the “borreliacidal” or toxic effect of the lone star tick’s saliva on B. burgdorferi bacteria which prevents acquisition of Lyme bacteria from infected vertebrate hosts (Ledin et al. 2005). 

The lone star tick is the primary vector of Ehrlichia chaffeensis and Ehrlichia ewingii which cause ehrlichiosis in humans and domestic dogs (Anderson et al. 1993; Beall et al. 2012).  There is recent evidence of human infection with E. chaffeensis in Wisconsin residents without travel history (contact the State Department of Health for further information).

E chaffeensis 2013

Other bacterial agents isolated from lone star ticks include:

Rickettsia amblyommii- a member of the spotted fever group–R. amblyommii has been implicated as a possible human pathogen based on serologic evidence from individuals recovering from illness after a tick bite.

Francisella tularensis- the cause of tularemia or rabbit fever in humans and domestic animals. Tick transmission of this pathogen remains important–ticks are efficent reservoirs and vectors and can maintain the organism both transstadially (through life stages) and transovarially (from female to offspring). Other routes of transmission include: inhalation of aerosolized bacterial organisms and direct contact with infected wildlife species or ingestion of infected carcasses of wild game species (e.g. cottontail rabbits, beaver, muskrat, meadow voles). 

Coxiella burnetti- the cause of Q-fever in humans and domestic animals. Tick transmission of this pathogen is not thought to play a significant role in human disease but ticks may transmit the disease among domestic ruminants (e.g. cows, sheep and goats). Both Ixodid (hard) and Argasid (soft) type ticks can act as reservoirs for this bacterial organism. 

Meat allergy-Recent work suggests that some people may become allergic to red meat following the bite of a lone star tick.  Symptoms range from hives to severe shock resulting in a trip to the emergency room.  For many people, the allergy begins to wear off within a few months. 

Curr Opin Allergy Clin Immunol. 2013 Aug;13(4):354-9. doi: 10.1097/ACI.0b013e3283624560. Tick bites and red meat allergy.  By Commins SP and Platts-Mills TA.

 References:

Allan BF, Goessling LS, Storch GA, Thach RE. (2010). Blood meal analysis to identify reservoir hosts for Amblyomma americanum ticks. Emerg Infect Dis; 16(3): 433-440. http://wwwnc.cdc.gov/eid/article/16/3/09-0911.htm

Anderson, B.E., Sims, K.G., Olson, J.G., Childs, J.E., Piesman, J.F., Happ, C.M., Maupin, G.O. & Johnson, B.J. (1993) Amblyomma americanum: a potential vector of human ehrlichiosis. American Journal of Tropical Medicine and Hygiene, 49, 239–44.

Beall MJAlleman ARBreitschwerdt EBCohn LACouto CGDryden MWGuptill LCIazbik CKania SALathan PLittle SERoy ASayler KAStillman BAWelles EGWolfson W,Yabsley MJ. (2012). Seroprevalence of Ehrlichia canis, Ehrlichia chaffeensis and Ehrlichia ewingii in dogs in North America. Parasit Vectors. 2012 Feb 8;5:29.
 

Childs JE & Paddock CD (2003). “The ascendancy of Amblyomma americanum as a vector of pathogens affecting humans in the United States.” Annual Review of Entomology; 48 (1): 307–337.  http://www.annualreviews.org/doi/pdf/10.1146/annurev.ento.48.091801.112728

Keirans JE, Lacombe EH. 1998. First records of Amblyomma americanumIxodes (Ixodes) dentatus, and Ixodes (Ceratixodes)uriae (Acari: Ixodidae) from Maine. J. Parasitol. 84:629–31.

Keirans JE and Litwak TR. (1989). Pictorial Key to the Adults of Hard Ticks, Family Ixodidae (Ixodida: Ixodoidea), East of the Mississippi River. J. Med. Entomol. 26(5): 435-448. http://www.dtic.mil/cgi-bin/GetTRDoc?AD=ADA233445

Kollars TM Jr, Oliver JH, Durden LA, Kollars PG. (2000). Host association and seasonal activity of Amblyomma americanum (Acari: Ixodidae) in Missouri. J Parasitol. 86(5): 1156-9.
 

Ledin KE, Zeidner NS, Ribeiro JMC, Biggerstaff BJ, Dolan MC, Dietrich G, VredEvoe L & Piesman J. (2005). “Borreliacidal activity of saliva of the tick Amblyomma americanum Medical and Veterinary Entomology; 19(1): 90–95.

Masters EJ, Grigery CN & Masters RW (June 2008). “STARI, or Masters disease: lone star tick-vectored Lyme-like illness”. Infectious Disease Clinics of North America; 22 (2): 361–376, viii.

Means RG, White DJ. (1997). New distribution records of Amblyomma americanum (L.) (Acari: Ixodidae) in New York State. J Vector Ecol; 22(2): 133-45.

Mixon TR, Campbell SR, Gill JS, Ginsberg HS, Reichard MV, Schulze TL, Dasch GA. Prevalance of Ehrlichia, Borrelia, and Rickettsial agents in Amblyomma americanum (Acari:Ixodidae) collected from nine states. J Med Entomol. 43(6): 1261-8.

Piesman, J. & Happ, C.M. (1997) Ability of the Lyme disease spirochete Borrelia burgdorferi to infect rodents and three species of human-biting ticks (blacklegged tick, American dog tick, lone star tick) (Acari: Ixodidae). Journal of Medical Entomology, 34, 451–6.