A tick will sneak up on you or your dog, take up residence on your body, administer a painless bite into the skin and engorge itself with blood. A single tick bite can transmit multiple pathogens as well as creating secondary infections and allergic reactions. Do you know what to do and how to protect yourself?
The tick is often mistaken as an insect but is actually a small arachnid. Ticks are external parasites (ectoparasites) that feed on the blood of mammals, birds, some reptiles and amphibians. The term for diet consisting of only blood is called hematophagy.
Description of a tick
The typical tick has a fiendishly designed feeding system. With its mouth, which is made up of a pair of jointed “palps,” a pair of “chelicerae,” and a barbed feeding tube called a "hypostome", it selects and sets its dining table, uninvited, on the skin of its unwilling host.
Using its palps it chooses the precise spot where it will puncture the skin. The chelicerae shield the hypostome, its feeding tube. The backward-barbed hypostome penetrates the skin, producing a small excavation where blood can pool. The barbs make it hard to remove the tick. A glue-like substance from its salivary glands firmly secures its connection to the skin. The saliva acts as both a local anesthetic and as an anticoagulant.
A tick ensures that its host feels neither pain nor irritation and remains blissfully unaware of its presence. The blood supply does not clot but remains fluid for sucking due to the saliva's action. As it sucks in blood, engorging its expandable body and external skeleton, the tick, depending on its species, may increase its body weight by as much as several hundred times, according to scientist Larisa Vredevoe, University of California, Davis.
With simple eyes and specially adapted sensors, it can detect light, shadow, shapes, movement, exhaled carbon dioxide, smells and heat all signals it uses to find and climb aboard potential hosts, including mammals, birds, reptiles and amphibians.
A fraction of an inch in length, a typical tick has a roughly teardrop-shaped, two-part body encased in a leathery, accordion-like, dark brown external skeleton. One part the tip of the teardrop serves as its head, with a primitive brain, simple eyes, and mouth. The other part the main swell of the teardrop functions as an expandable body, containing the internal organs.
A single tick bite can transmit multiple pathogens as well as creating secondary infections and allergic reactions. Ticks therefore are the most common transmitters of vector-borne diseases in the U.S.
- -Rickettsia parkeri Rickettsiosis
- -Rocky Mountain Spotted Fever (RMSF)
- -STARI (Southern tick-Associated Rash Illness)
- -Tickborne relapsing fever (TBRF)
- -364D Rickettsiosis
A tick may belong to either of two familiesthe “hard” ticks, which have projecting and very noticeable mouthparts, or the “soft” ticks, which have barely noticeable projecting mouthparts. There are
A hard tick, unable to fly or jump, climbs up low-growing vegetation near an animal run, where it waits, sometimes for months, for a target of opportunity. When the moment arrives, it uses its clawed front legs to latch onto the ankles or legs of the passing potential host.
The tick selects its mark, pierces the skin and begins sucking blood. Typically, the adult female tick behaves like a glutton, remaining in place until she is engorged, which may take several days. She may increase her body weight several hundred times. Then the female tick abandons her feeding site to lay eggs and die. The adult male tick feeds less ravenously, for it has come to the host for the primary purpose, not of finding a meal, but rather, of finding a mate. Opportunistically, the male tick sometimes feeds, not on the host, but on an engorged female.
When the female hard tick abandons her feeding site, she lays a batch of 10,000 or more eggs, and then dies, according to the Pest Products Internet site. (The male typically dies soon after mating.)
Tick offspring pass through four life cycle stages. First, is the egg stage. Second, the newly hatched larva, or “seed” tick, which has only six legs, immediately begins to seek its blood fortune. With luck, the young tick will attach itself to a small mammal or reptile. Third, after engorging, probably over no more than several hours, it will molt, emerging as a nymph, now with its full complement of eight legs. The new nymph tick repeats the feeding cycle, taking longer to engorge itself. Fourth, the tick will molt once more, now emerging as an eight-legged adult tick. The adult ticks repeat the feeding cycle over a several day period, which will culminate in reproduction and death.
Depending on its species, a hard tick may remain on the same host throughout the last three stages of its life cycle; or it may remain on the same host for the middle two stages of its life cycle and find a new host for the fourth stage; or it may find a new host for each of the last three stages of its life cycle. In the first instance, it would be called a “one-host tick,” Vredevoe said. In the second, it would be called a “two-host tick,” and in the third, a “three-host” tick. Its life cycle lasts no longer than perhaps a year in our desert basins, but it may live for three years or more in our forested mountain ranges.
The Soft Tick
Soft ticks do not have a hard shield; they are shaped like a large raisin. Soft ticks prefer to feed on birds or bats and are seldom encountered unless these animals are nesting or roosting in an occupied building. A typical soft tick takes up residence in the burrow or nest of a mammal, bird, reptile or amphibian, waiting for the opportunity to clamber onto a host.
When feeding, it may increase its body weight by five to ten times. Unlike a hard tick, the adult soft tick feeds and reproduces repeatedly. The female may lay several dozen eggs after each meal.
Like the hard tick, a newly hatched soft tick larva has six legs. It takes a blood meal then molts, emerging as an eight-legged nymph. Unlike the hard tick, the soft tick passes through several nymphal stages, feeding repeatedly, growing and molting several times, until it develops into an eight-legged adult. A soft tick typically lives much longer than a hard tick. Some ticks have gone a year or more without feeding.
American Dog Tick, Dermacentor variabilis, is one of the most frequently encountered ticks and is also sometimes known as the wood tick. The larvae and nymphs feed on small warm-blooded animals such as mice and birds. The adult American dog tick will feed on humans and medium to large mammals such as raccoons and dogs. It is the most commonly identified species responsible for transmitting Rickettsia rickettsii, which causes Rocky Mountain spotted fever in humans. The American dog tick can also transmit tularemia. This tick is widely distributed east of the Rocky Mountains and also occurs in limited areas on the Pacific Coast.
Brown Dog Tick, Rhipicephalus sanguineus, is found through most of the United States. This tick feeds on dogs, but rarely bites people. Unlike other species of ticks, its life cycle allows it to survive and develop indoors.
Rocky Mountain Wood Tick, Dermacentor andersoni, can transmit Rocky Mountain spotted fever and tularemia to humans. This tick is found in the Rocky Mountain states in the northwest. Adult ticks feed primarily on large mammals. Larvae and nymphs feed on small rodents. Adult ticks are primarily associated with pathogen transmission to humans.
Western Blacklegged Tick, Ixodes pacificus can transmit the organisms responsible for causing anaplasmosis and Lyme disease in humans. Wild rodents and other mammals are likely reservoirs of these pathogens. The Larvae and nymphs feed on birds and small rodents, while adult ticks feed on deer and other mammals.The Western Blacklegged Tick is distributed along the Pacific coast of the United States.
Blacklegged Tick or Deer Tick - Ixodes scapularis can transmit the organisms responsible for causing anaplasmosis and Lyme disease in humans. The Deer Tick is found in the eastern United States from central Texas and Florida up to Maine, Minnesota and Iowa. The primary host of the adult Deer Tick is the white-tailed deer. The larvae and nymphs attach andfeed on small mammals and birds. Adult ticks are primarily associated with pathogen transmission to humans.
Written by Jay Sharp
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