[by:www.51voa.com] [00:00.00]¸ü¶àÌýÁ¦Çë·ÃÎÊ51VOA.COM [00:00.40]In the United States, many children are returning to school [00:05.16]after a nearly three-month summer break from classes. [00:10.00]With the start of school, health officials are warning children and their parents [00:15.75]about a new kind of head lice. [00:19.40]Being infected with head lice can cause a child to miss classes. [00:25.32]The insects are difficult to kill. [00:29.04]They can also cause discomfort in the child, [00:32.68]who may try to remove them from the skin. [00:36.64]A new study suggests that lice populations [00:40.72]in at least half of the 50 states [00:44.08]have become resistant to the chemical pyrethroid. [00:48.23]The substance has been used for years in products to kill the insects. [00:55.17]Seventeen-year old Ben Kupferman of California [01:00.04]just returned home from a summer camp. [01:04.00]He brought some unwanted visitors with him. [01:07.76]"I was just scratching my head and [01:10.12]one of the, the lice just came out. It was a, [01:13.44]just on my finger, crawling around." [01:17.07]The Centers for Disease Control and Prevention [01:21.00]says lice spread to anywhere between six [01:25.64]to 12-million children in the United States every year. [01:31.36]All these boys and girls are between three and 11-years old. [01:38.92]In the past, parents bought a chemical product at a store [01:44.24]and put it on their child's head. [01:47.80]It usually killed the lice within a few days. [01:53.12]But experts say the product is not [01:55.92]as effective as it once was [01:59.28]because the insects have developed tolerance and even resistance to it. [02:07.32]Angela Baker is a doctor at the Children's Hospital of Wisconsin. [02:13.04]"Certain ones (lice) have the potential to mutate and protect themselves against [02:19.44]whatever we're using to try to kill them." [02:22.08]David Gaines is a public health entomologist in the state of Virginia. [02:27.88]He says lice have been developing resistance to chemical treatments for some time. [02:34.80]"This has probably been coming for many, many years. [02:37.76]There's reports of insecticide-resistant lice going back decades." [02:43.69] When traditional treatments don't work, [02:46.92]doctors prescribe stronger drugs. [02:50.56]But some parents object to using strong chemicals on their children. [02:57.00]They instead want to use a more natural treatment. [03:02.48]Beverly Mann joined with other parents [03:05.96]to create a lice-treatment business. [03:09.92]Their company uses products that do not have strong chemicals in them. [03:15.72]"Well, we use an all-natural treatment oil [03:17.88]and we do give (a) guarantee with our services. [03:20.00]So it, it is pesticide-free. [03:22.68]We do the combing, we do the picking, so [03:24.88]the parent at home doesn't have to." [03:27.04]Gerry Wolburg launched a lice-removal business three years ago [03:32.60]when he found lice on his daughter's head. [03:36.60]He uses heat to kill lice eggs. [03:39.80]"It desiccates the, the lice with hot air, [03:44.16]and if you leave eggs in the hair [03:46.92]they're desiccated -- that means they're, they're shriveled up. They're dried (up) and we like to [03:51.48]point out that it's like leaving a boiled egg in a hen-house -- [03:54.96]it's not gonna, it's not gonna hatch." [03:57.72]Lice do not carry diseases. [04:00.24]But they are troubling, [04:02.16]difficult to kill and can make the child feel bad. [04:07.32]And they can keep children from attending school for a few days. [04:12.56]I'm Christopher Jones-Cruise.