Amblyomma americanum, also known as the Lone Star Tick, the Northeastern Water Tick, or the Turkey Tick, is a type of tick indigenous to much of the eastern United States and Mexico, that bites painlessly and commonly goes unnoticed, remaining attached to its host for as long as seven days until it is fully engorged with blood. It is a member of the phylum Arthropoda, class Arachnida. The adult lone star tick is sexually dimorphic, named for a silvery-white, star-shaped spot or "lone star" present near the center of the posterior portion of the adult female shield (scutum); adult males conversely have varied white streaks or spots around the margins of their shields. A. americanum is also referred to as the turkey tick in some Midwestern U.S. states, where wild turkeys are a common host for immature ticks. It is the primary vector of Ehrlichia chaffeensis, which causes human monocytic ehrlichiosis, and Ehrlichia ewingii, which causes human and canine granulocytic ehrlichiosis. Other disease-causing bacterial agents isolated from lone star ticks include Francisella tularensis, Rickettsia amblyommii, and Coxiella burnetti.
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Range and Habitat
The lone star tick is widely distributed across the East, Southeast, and Midwest United States. It lives in wooded areas, particularly in second-growth forests with thick underbrush, where white-tailed deer (the primary host of mature ticks) reside. Lone star ticks can also be found in ecotonal areas (transition zones between different biomes) such as those between forest and grassland ecosystems. The lone star tick utilizes thick underbrush or high grass to attach to its host by way of questing. Questing is an activity in which, in response to stimuli from biochemicals such as carbon dioxide or heat and vibration from movement, the tick climbs up a blade of grass or to the edges of leaves and stretches its front legs forward, mounting the passing host as it brushes against the tick's legs. Once attached to its host, the tick is able to move around and select a preferred feeding site.
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Development
The tick follows the normal development stages of egg, larva, nymph and adult. It is known as a 3-host tick, meaning that it feeds from a different host during the larval, nymphal, and adult stages. The lone star tick attaches itself to a host by way of questing.
Hosts
The lone star tick is an aggressive, generalist feeder; it actively pursues blood meals and is nonspecific about the species of host it feeds upon. A. americanum is a three host tick, meaning it requires a separate animal or human host to complete each stage of its life cycle (larva, nymph, and adult). The life cycle begins when the blood-engorged adult female tick drops from her host, depositing around 5,000 eggs a few days later, once she has reached a safe and suitable location, such as in mulch or leaf litter. After an incubation period, larvae hatch from their eggs and undergo a quiescent (resting period); this is followed by the pursuit of a host via questing. After feeding for one to three days, the blood-engorged larva will dislodge from its host to digest its blood meal and molt into a nymph. The nymph follows this same pattern, attaching to a new host via questing and dropping from the host after its blood meal to molt into an adult tick. The female adult tick dies shortly after depositing her eggs.
Larval lone star ticks have been found attached to birds and small mammals, and nymphal ticks have been found on these two groups as well as on small rodents. Adult lone star ticks usually feed on medium and large mammals, and are very frequently found on white-tailed deer. Lone star ticks will also feed on humans at any stage of development.
Vector
Like all ticks, it can be a vector of diseases including human monocytotropic ehrlichiosis (Ehrlichia chaffeensis), canine and human granulocytic ehrlichiosis (Ehrlichia ewingii), tularemia (Francisella tularensis), and southern tick-associated rash illness (STARI, possibly caused by the spirochete Borrelia lonestari). STARI exhibits a rash similar to that caused by Lyme disease, but is generally considered to be less severe.
Though the primary bacterium responsible for Lyme disease, Borrelia burgdorferi, has occasionally been isolated from lone star ticks, numerous vector competency tests have demonstrated that this tick is extremely unlikely to be capable of transmitting Lyme disease. Some evidence indicates A. americanum saliva inactivates B. burgdorferi more quickly than the saliva of Ixodes scapularis. Recently the bacteria Borrelia andersonii and Borrelia americana have been linked to Amblyomma americanum.
In response to two cases of severe febrile illness occurring in two farmers in northwestern Missouri, researchers determined the lone star tick can transmit the heartland virus in 2013. Six more cases were identified in 2012-2013 in Missouri and Tennessee.
Meat allergy
The bite of this tick can cause a person to develop a meat allergy to nonprimate mammalian meat and meat products. This allergy is characterized by adult onset, and a delayed reaction of urticaria or anaphylaxis appearing 4-8 hours after consumption of the allergen. The allergen has been identified as a carbohydrate called galactose-?-1,3-galactose (alpha gal). As well as occurring in nonprimate mammals, alpha gal is also found in cat dander and in patients taking Cetuximab. Commercial tests for alpha gal IgE became available following research.
Source of the article : Wikipedia
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