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Tick-borne diseases outside usual borders.

As summer approaches, people in the Northeast and Midwest look forward to spending more time outdoors--which also means plotting ways to avoid the disease carrying black-legged deer tick. However, those living outside of these areas also may want to take precautions. Black-legged ticks are growing in number rapidly, expanding geographically, and carrying pathogens that can lead to ailments like Lyme disease and babesiosis into places where they were relatively unknown.

Disease ecologist Maria Wasser of Columbia University, New York, is tracking the spread and emergence of tick-borne pathogens, including a malaria-like parasite called Babesia microti, which causes babesiosis--a malaria-like malady-when transmitted to humans. An increasing number of ticks are infected with Babesia and Wasser's team is exploring evidence that the trend is connected to the rapid spread of Borrelia burgdorferi, the bacterium that causes Lyme disease.

"We found that these two pathogens co-occur in ticks more frequently than expected, resulting in enhanced human exposure to multiple infections," says Wasser, associate professor in the Department of Ecology, Evolution and Environmental Biology. "Multiple infections lead to more severe symptoms and can make diagnosis more muddled and difficult."

About 1,000 new cases of babesiosis are reported each year, while Lyme disease infects about 30,000 people annually. The two diseases share some of the same symptoms, including a flu-like illness, but babesiosis, which can cause certain types of anemia, potentially is fatal in people with suppressed immune systems. It also can be transmitted via blood transfusions, posing an additional public health threat.

If left untreated, Lyme disease, which generally has a distinctive bull's-eye shape at the site of the bite, may lead to problems in the brain and nervous system, muscles and joints, heart and circulation, digestion, and reproductive system and skin.

Following lab experiments, field work, and the use of mathematical models, Wasser's team and researchers at the Yale School of Medicine, New Haven, Conn.; Tufts Medical Center, Boston, Mass.; and Australia's Royal Melbourne Institute of Technology recently concluded a study suggesting a connection between Borrelia and Babesia. The study shows that mice infected with both pathogens are more likely to transmit Babesia to ticks, which suggests an increased exposure to babesiosis for humans. So, as Lyme-disease causing Borrelia invades new areas, babesiosis likely will follow.

"Understanding how these pathogens may influence each other's distribution is important," stresses Wasser, who notes that, when an infection emerges in new areas, "the diagnosis may be delayed because doctors and veterinarians don't immediately recognize the symptoms."

One working theory concerning why ticks are invading new areas relates to global warming: higher temperatures speed up ticks' development, which can result in larger populations.

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Title Annotation:Pathogens
Publication:USA Today (Magazine)
Date:Jun 1, 2015
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