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Anaplasmosis, Human Granulocytic

Human granulocytic anaplasmosis (HGA) is an infection caused by the bacteria Anaplasma phagocytophilum. HGA bacteria infect the white blood cells of their hosts, specifically the granulocytes. In California, people get HGA when they are bitten by a western black-legged tick infected with HGA bacteria. Ticks become infected with HGA bacteria when they bite an infected wild rodent. If that tick later bites a human, the tick may transmit the HGA bacteria to the person. Dogs and horses can be infected with HGA bacteria, but they cannot transmit the infection to people.

Most individuals infected with HGA bacteria have no or mild symptoms. When symptoms occur, they resemble the flu, with fever, headache, fatigue, muscle aches, and nausea. Some individuals may also have vomiting, cough, or a rash. Some patients, particularly elderly persons or those with weakened immune systems, may have a more severe illness and need to be hospitalized. HGA is rarely fatal.

Taking appropriate precautions to avoid tick bites can reduce the risk of HGA, as well as other diseases transmitted by ticks. When you are in areas where ticks are present:

• Stay on trails whenever possible.

• Wear light-colored long pants and long sleeve shirts.

• Tuck your shirt into your pants and your pant legs into your socks or boots.

• Apply repellents containing DEET to the skin.

• Apply tick repellents containing permethrin to your clothing.

• Check yourself for ticks promptly after being in an area where ticks are present.

• Remove any ticks you find on your body right away.

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Last modified on: 7/24/2012 1:02 PM