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Genome reveals secrets of bloodsucker.

With tenacity befitting its subject, an international team of nearly 100 researchers toiled for a decade and overcame tough technical challenges to decipher the genome of the blacklegged tick (Ixodes scapularis), which lives up to two years in the wild and nine months in the lab. "Ticks spread more different kinds of infectious microbes to people and animals than any other arthropod group," says Anthony S. Fauci, director of the National Institute of Allergy and Infectious Diseases, Bethesda, Md.

"The spiral-shaped bacterium that causes Lyme disease is perhaps the best known microbe transmitted by ticks; however, ticks also transmit infectious agents that cause human babesiosis, anaplasmosis, encephalitis, and other diseases. The recently assembled genome provides insight into what makes ticks such effective vectors and may generate new ways to lessen their impact on human and animal health."

Catherine A. Hill, professor of entomology and vector biology at Purdue University, West Lafayette, Ind., headed the team of investigators. She notes that Ixodes ticks have three blood-feeding life stages and, during each one, they feed on a different vertebrate animal. During feeding, ticks ingest blood for hours or days at a time. After mating, adult female ticks rapidly imbibe a large blood meal during which they expand hugely.

Compared with other blood-feeders, ticks have many more proteins devoted to consuming, concentrating, and detoxifying their iron-containing food. Although mosquitoes--which quickly siphon up relatively small amounts of blood through a tube-like mouthpiece--have several proteins dedicated to blood digestion, ticks have many more involved in this process. Other genes code for proteins that help ticks concentrate the blood and rapidly excrete excess water that accompanies large blood meals. Still other genes allow ticks to expand their stiff outer coats quickly to accommodate a 100-fold increase in total body size during blood feeding.

Other peculiarities of the tick's lifestyle reflected in the genome include genes associated with the multifaceted sensory systems that the parasite uses when "questing" for a host during each of its separate blood-feeding stages. Compared with mosquitoes, ticks appear to have fewer genes used to detect hosts and, unlike a mosquito's "smell" receptors, ticks may use "taste" receptors to locate their food sources.

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Title Annotation:Blacklegged Tick
Publication:USA Today (Magazine)
Geographic Code:1USA
Date:Jun 1, 2016
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