Lyme Disease Ticks



It certainly isn't necessary to understand ticks in order to beat Lyme disease. However, in case you'd like an objective viewpoint of the minute critter that is likely responsible for your illness, here's a brief overview of the arthropod we all know and despise, the black-legged tick.

Arthropods are the most successful animals in nature. They have the capacity to exploit the greatest amounts, and the most diverse kinds of food. They have the most offspring, they thrive and survive in the most habitats, and they efficiently fend off competition and threats from predators and other organisms.
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There are five lineages of arthropods. The tick is a tiny, ancient animal that belongs to the chelicerate lineage. The other four lineages are the insects, the crustaceans, the myriopods (where we find centipedes and millipedes), and the extinct branch of the family tree, the trilobites. The tick is a type of arachnid whose familiar relatives include spiders, scorpions and chigger mites. These beasts evolved out of shallow seas, where they originated during the Paleozoic era, about 500 million years ago. The remaining marine species include sea spiders, horseshoe crabs and a few mites.

Among the smallest members of the arachnid family are the land mites, a species that is incredibly abundant and diverse. They have wide distribution. Like dust bunnies under the furniture, they multiply easily and get around. There is an estimated 500,000 species of mites, including the dust mite and the tick. Ticks are one of the few harmful parasites in the whole bunch. Many ticks transmit pathogens that cause disease in humans. The black-legged tick (aka the Deer tick or Ixode), which is the vector for
Borrelia burgdorferi, transmits the bacterial agent responsible for Lyme disease. Other bad diseases caused by pathogens distributed by tiny ticks include Rocky Mountain spotted fever, scrub typhus, tularemia and encephalitis.
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Carbohydrates are the most abundant biological molecules in nature. The tick's body, like that of an earthworm, spider or crab, is covered with a protective cuticle that is reinforced with chitin, a class of carbohydrate called a polysaccharide. The cuticle is called the exoskeleton, and possibly evolved as a defense against predators. If you've ever seen a big spider walk across an aluminum oil pan in the garage, you might have also heard the faint clackety-clack of chitin.

The bite from an infected tick transmits Borrelia burgdorferi from wild animals, such as mice and deer, to humans. Humans may then develop
symptoms of Lyme disease. Not everyone gets the most typically cited symptom, the bull's eye rash, which is a reaction to the tick bite. Some may develop it but not see it, especially if it's hidden behind a knee, on their scalp or another area of the body covered in hair. Ticks don't fly and they can't jump. They crawl onto animals and people who brush up against the tips of grasses and plants where they await their next blood meal. Once on the body, they generally crawl for a secure hiding space. This is why ticks and tick bites are often found in armpits, the groin, hidden in body hair or beneath the tight elastic bands of socks, underwear or pants.
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Tick bites were not always associated with Lyme disease. Polly Murray, who moved with her family from New York City to Lyme, Connecticut in the 1960s, knew that she wasn't a hypochondriac as the doctors she consulted thought, but she didn't connect her symptoms to the tick bites she and her children had become exposed to. The skin rashes, swollen glands, painful joints and neurological problems that her family had experienced ever since moving to Lyme weren't a figment of her imagination. Allen Steere, a rheumatologist at Yale University, was convinced that their rheumatoid arthritis, which he later designated "Lyme arthritis," might be the result of a virus, not the result of a bacterial infection spread by ticks. Steere's research into Lyme disease deepened, and he discovered that about 25% of his young patients, who were all suffering from an unusually high occurrence of juvenile arthritis, remembered having a spreading rash. He began to connect the dots, having heard about a skin rash in northern Europe associated with ticks.

Ticks are ancient creatures, and Lyme is not a new disease. Over a hundred years ago German, Swedish and Austrian physicians and researchers studied and wrote about expanding rashes and concurrent neurological disease, related to tick bites, that have lead to our current understanding of Lyme disease.
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References

Beating Lyme: Understanding and Treating This Complex and Often Misdiagnosed Disease by Constance A. Bean with Lesley Ann Fein, MD, MPH. (Amacom 2008)

Biology today and tomorrow (Thomson Learning Inc. Brooks/Cole 2005)

Suzanne Arthur/Lyme Disease Research Database/All rights reserved 2008