The start of another school year is just around the corner and with it comes the threat of closures, lost school days and that now too familiar annoyance - no, not teacher strikes, the risk of head lice.
The return to school always heralds the return of head lice, but now the nits are becoming a particular problem. Researchers have discovered mutant bugs which can survive the most popular if smelly treatments.
Prof John Clark and Mr KyongYoon, of the University of Massachusetts at Amherst, have developed a novel way to study these new mutants, however, using artificial scalp which the nits take to be the real thing. They hope to use this artificial feeding system to raise mutants and learn why they have become resistant to permethrin, one of the most commonly used lice insecticides.
The two described their feeding system this week to the 224th national meeting of the American Chemical Society in Boston. "We have a membrane and automatic blood-feeding system that allows us to rear these things on little hair tufts," said Prof Clark. "We just cut little hair tufts and make tepees out of them. The head lice kind of sit on this membrane and they think they are on a scalp and they wander down and take a blood meal and then go back up."
Insect resistance to chemical treatments is a common problem, but a particularly itchy one when it comes to head lice. If the chemical is not used properly, most nits will die, but a few mutants will remain to grow and multiply.
"We don't have an effective control process out there," said Prof Clark. "That means that they \ are becoming harder to control and the chances of increased infestation are certainly higher. The longevity of effective control provided by permethrin is in serious jeopardy unless effective monitoring of this resistance is begun."
The researchers studied permethrin resistance in a number of head lice populations across the US. Resistance ranged from 50 per cent in nits from some Los Angeles schoolchildren to about 98 per cent in migrant workers in Florida. Nits resistant to permethrin were discovered in Boston and Texas.
Prof Clark believes that the ability to raise human head lice in a laboratory will also allow researchers to investigate what role lice may have in disease transmission, even including agents of bio-terrorism such as anthrax.
Wounds left by head lice bites would leave people more susceptible to cutaneous anthrax, if it was released, because the anthrax can enter through cuts in the skin.