late lice. The common louse head Pediculus humanus capitis may take up to 14 days to hatch.
Gilles San Martin / Wikimedia Commons
Here are some lousy news for parents of children biting head: Lice eggs can take 2 weeks to hatch in the hair humans, which makes the standard 7 days treatment delousing ineffective in some cases. New research shows that if the conditions are good, eggs, called nits, can sit dormant for treatment, only to appear later and re-infest the scalp. A third application may be necessary after 14 days to remove nits hatch slow, they say.
Lice do lay their eggs directly on the skin instead, they lay nits at the base of the hair stems. The timing of the outbreak louse on a human head is difficult to follow because adult lice lay eggs continuously, obscuring earlier hatches, and the effectiveness of traditional insecticides on eggs varies. Previous estimates of how long remain viable nits only to 14 days, but most of this work from the 1920s and 1930s, when researchers reared body lice inside boxes attached to the arm or ankle of a person. More recent work is based on head lice raised in laboratory incubators, which are more stable than the wide range of temperatures and cleanliness found on a human scalp.
For a more reliable estimate, medical entomologist Ian Burgess of Insect Research & Development Ltd. in Cambridgeshire, UK, analyzed data from 20 previous studies on treatments that kill lice by physical means, such as lotions that suffocate insects, but do not kill the eggs. They do not include insecticide treatments for lice across the UK have developed resistance to standard drugs, Burgess said, leading more doctors to try a brute force approach that does not rely on insecticides.
1895 Data patients revealed cases where newly hatched found technicians lice nymphs on the 14th day after the start of treatment, even if the second application the scalp was held seven days before. "Some [nymphs] had emerged just an hour or two before checking," said Burgess. To exclude cases where reinfestation of another child had occurred, or when adults had escaped little lice treatment, it excluded cases with lice that have emerged over the number of days since the last treatment. Nearly two dozen cases have remained-enough to check a handful of nits may last longer than standard treatment protocols, Burgess reported in an upcoming issue of Medical and Veterinary Entomology.
Although the treatments themselves may play a role, the temperature of a person's scalp is likely to be the most important factor in the time it takes to hatch eggs, Burgess said. Location and hair issues as: Lice grow faster in warmer temperatures, so they will hatch more quickly when on the warm, thick hair at the nape as the thinner hair on top and in front of the scalp
analysis is the most rigorous yet to quantify the outbreak louse times, said Rich Pollack, an entomologist of public health at Harvard University. "It must be considered by those trying to make a management decision process," said Pollack, noting that only a small number of patients may need a third dose.
New insecticides oral may make the issue of time of incubation theoretical, Pollack notes. These drugs now available by prescription in the United States, are up to 85% effective in killing lice and eggs with a dose sparing spraying scalp's parents several times a child squirms.
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