Ticks that transmit Lyme disease, a debilitating disease caused by influenza like Borrelia bacteria spread quickly across the United States. A new study shows how quickly. Over the past 20 years the two species known to spread the disease to humans were so advanced in half of all US counties.
Lyme disease cases have tripled in the US over the past two decades, making the vector-borne disease most frequently reported in the northern hemisphere. The disease now affects about 300,000 Americans each year. If the early diagnosis of a rash usually appears around the site of the tick bite, Lyme can be treated effectively with antibiotics, but the long-term infections may produce more severe symptoms, including stiffness of joints, the inflammation of the brain, and nerve pain.
For a comprehensive map of where the two black-legged tick species ( Ixodes scapularis ) and the western black-legged tick ( I pacificus .) - lived, Rebecca Eisen and colleagues from the Centers for Disease Control and Prevention (CDC) in Fort Collins, Colorado, combined data from published articles with state monitoring data and ticks County dating back to 1996. they counted tick sighting reports in each of the 3110 continental US counties to determine if these counties have welcomed an established population or only a few individuals. Ticks were considered "established" when observations of at least six ticks or two of the three stages of life, have been reported in one year.
Their findings, published in the Journal of Medical Entomology , show that the black-legged tick has undergone a population explosion, doubling its range established in less than 2 decades. It is now reported in 45.7% of US counties, up from 30% in 1998. The black-legged ticks are found in 37 states across the eastern United States. Western tick rare black legs, limited to just six states showed modest increases of established populations, from 3.4% to 3.6% of the counties. Together, these two vectors of Lyme disease are now found in half of all US counties.
"Since the late 190s, the number of counties in the northeast of the United States who are considered at high risk of Lyme disease have increased over 320%," says Eisen. "The tick is now established in areas where he was not there 20 years ago," she added.
The distribution throughout the United States to tick observations between a) 107-1996 and b) 107-2015
(top to bottom): .. DT Dennis et al J. Med. . Entomol (1998); R. J. Eisen et al. , J. Med. Entomol. (2016
Perhaps the most worrying northeast of tic-dense is where Lyme disease is most common. Although the tick black-legged is found from Florida to Minnesota, 95% of confirmed cases come from only 14 states in the northeast and upper Midwest. "Although our map shows a wide distribution ... the risk of people getting the disease Lyme are not equal in the country, "says Eisen.
a study published in PLOS ONE last year could hold the answer. Isis Parasitologist Arsnoe of Michigan State University East Lansing and colleagues found that populations of black-legged ticks behave differently in the northern and southern United States. tick nymphs black-legged in the north are bolder and more active in the search for hosts a behavior known quests. Arsnoe and his team found that tick nymphs from Wisconsin and Rhode Island were 20 times more likely to get out of the leaf litter, putting them in the path of passing humans, the nymphs of Tennessee and Florida. "Behaviour Questing is a key factor that affects the risk of tick bites," says Arsnoe. "Ticks that remain buried in the leaves are not likely to have the opportunity to bite the man pass and unless they bite, they can not transmit the disease." Arsnoe is concerned that the ticks found in the north may also develop in the southern states, taking their quest behavior with them.
But despite the wide distribution of vectors, the chances of a tick to come into contact with humans are still relatively low. Avoid thick vegetation zones, using a strong repellent and bath after hiking are usually enough to avoid contact, CDC said. Eisen said the most important thing now is to carefully monitor the spread of the black-legged tick, so that people can learn about potential vectors of diseases in their area and take steps to protect
0 Komentar