Lone Star Tick
Primarily found east of the Rocky Mountains, but also found in limited areas along the Pacific coast, American Dog ticks (Dermacentor variabilis) are found predominantly in areas with little to no tree cover, such as grassy fields and along walkways and trails. They feed on a variety of hosts, ranging in size from mice to deer, and can survive for up to 2 years at any given stage if no host is found. Females can be identified by their large off-white scutum against a dark brown body.
Perhaps one of the easiest ticks to identify, the adult female lone star tick (Amblyomma americanum) is round, is reddish-brown in color, and can be easily distinguished from other ticks by the presence of a single, white ‘dot’ in the center of the back. As with most hard ticks, females are generally larger than males.
Scutum coloration in males is dark brown, and sometimes has patches of red. Cream colored or whitish ornations are sometimes present around the festoons of adult males.
Lone Star ticks are three-host ticks, feeding on different hosts during the larval, nymphal, and adult stages. The ticks have piercing-sucking mouthparts with chelicerae that pierce through the skin of the host. Attachment is facilitated by the tubular hypostome and a secreted cement- or latex-like compound that attaches (“glues”) the tick to the host until feeding is complete. After feeding once in each larval, nymphal, and adult stage, the tick withdraws the mouthparts and drops to the ground to molt or oviposit.
A tick lifecycle begins when the blood-engorged female tick falls from the host and after several days deposits ~5,000 eggs on the soil in a “protected” location, such as in mulch or leaf litter. After dislodging from the host, the female will seek a microclimate, typically an area of high humidity at a soil level that is best suited for survival of the eggs.
Females have been shown to search for a favorable microclimate up to 61 cm from where they were experimentally placed on the ground after feeding. Following an incubation period, larvae hatch from eggs and progress through a quiescent (resting) period, then seek a host by questing.
Questing is a behavior that entails climbing up an object, like a blade of grass, and waiting for a host to touch the larva. The larva then grasps the host and proceeds to move about the host, seeking a preferred feeding site. After acquiring a host, the larva attaches, blood-feeds for 1-3 days, detaches its mouthparts, and then drops from the host to digest its blood meal and molt into a nymph.
Nymphs repeat this process; however, after dislodging from this second host they molt into adults. Sizes of ticks in each stage can vary due to genetic and environmental conditions. In laboratory settings, the life cycle can be shortened to less than 22 weeks under optimal conditions, but is usually 2 years in nature.
Larvae, typically called “seed ticks” due to their small size and abundance, are 0.5 to 1.0 mm long and have six legs. If humidity and temperature are favorable the larvae can survive for up to six months in the environment, but typically the larval stage is shorter due to acquisition of a suitable host. After feeding on the host for 4 to 9 days, the larva drops off and, in 3 to 4 weeks, molts into the nymphal stage. When larvae are encountered before host location, several thousand of them can be in a small area.
The Lone Star tick is by far, the most common tick reported to bite humans in the southeastern and southcentral United States. Various pathogens have been shown to enter the tick by blood feeding; however, most are not transmitted because the tick is not a competent vector. An unknown pathogen has been implicated in causing Southern Tick-Associated Rash Illness (STARI) in humans, but etiology, pathogenicity and identification are pending. Several pathogens are known to be transmitted by the lone star tick and given the proper circumstances they may manifest into disease. These include Ehrlichiosis, Rickettsiosis, Tularemia and protozoan infections. The causative agents of ehrlichiosis, rickettsiosis, and anaplasmosis are all tick-borne bacterial infections that are readily treatable in humans, but the causative agent can be difficult to determine because the similarities among the pathogens.
Recently, the Lone Star tick has been shown to be involved in producing or generating an immune response that caused a food allergy to red meat proteins, or Alpha-Gal Syndrome. Heavy infestations of Lone Star ticks also have been associated with increased mortality in white-tailed deer fawns in Oklahoma.
Dogs have been shown to be susceptible to infections of both Ehrlichia chaffeensis and Ehrlichia ewingii. However, dogs also are susceptible to Ehrlichia canis a related microbe, which is usually transmitted by Rhipicephalus sanguineus, the brown dog tick.
Theileria cervi is a tick-transmitted protozoan parasite that infects white-tailed deer and attacks red blood cells. This pathogen has been linked with deer death when tick numbers and parasite numbers are substantial. The role of Theileria cervi in deer mortality is somewhat unclear, however, given that some researchers have reported fawn mortality in deer populations infested with lone star ticks without the presence of Theileria cervi. The incidence rate of Theileria cervi increased in white-tailed deer populations from June to September, which corresponded to lone star tick activity in the area surveyed.
Lone Star ticks tend to live in wooded areas with thick underbrush, and along the edges of meadows and streams, where white-tailed deer are common.
Lone star ticks are widely distributed throughout the Southeastern, Eastern and South Central states.
The Lone Star tick is widely distributed across the eastern, southeastern and midwestern United States. However, the tick may establish local populations outside of this range. The tick reportedly has been expanding its range north and west out of the historic range depicted in the distribution map provided by the CDC. The lone star tick typically is found in second growth woodland habitats that have populations of white-tailed deer (Odocoileus virginianus).
With the re-introduction and increased populations of white-tailed deer in many areas of the eastern U.S., the ticks may further expand their range through transportation while feeding on white-tailed deer, a key host. Wild turkey populations also are a common host and may contribute to tick expansion by providing additional hosts for immature stages. In some Midwestern states the lone star tick is colloquially known as the “turkey tick” due to its association with wild turkeys.
Lone star ticks are known to be more aggressive than other species of tick. They will actively seek a host by sensing vibrations and carbon dioxide.
Although ticks are mobile, hosts are the primary means of tick dispersal for all active life stages. The Lone Star tick is very aggressive and non-specific when seeking hosts, although some specificity does occur within each life stage. Lone star ticks can be found on humans, domesticated animals (e.g. cattle, dogs, horses, goats), ground-dwelling birds (e.g., quail and wild turkeys), and small (e.g. squirrels, opossums, hares) and large (primarily white-tailed deer and coyotes) wild mammals.
Larvae primarily are collected from birds and mammals, but not on small rodents, while nymphs feed on all of these animals. Adults typically feed on large- or medium-sized mammals, but can be found on small rodents and wild turkeys. With the exception of wild turkeys, adult lone star ticks infrequently feed on birds.