A few times a year, parents with young children receive a message from school: lice. Advice? Comb thoroughly with the lice comb for two weeks until no more eggs and lice can be found. And possibly on days one and ten put the hair in the greasy stuff Dimethicone for fifteen minutes that makes the lice suffocate. And hope they’re all gone.
head lice, Pediculus humanus capitis, are small, gray-brown parasites the size of a sesame seed that claw their way into people’s hair. They need blood to survive. They suck that blood from the scalp with their suction snout. The lice spit that is released causes itching. Does someone with lice take a selfie with someone else and are the hairs long enough together? Then lice can crawl over – they don’t jump – and the other person will also have to comb.
Adolescents and adults
Lice seem to be most common among children. In the last RIVM sample, in September 2018, 3.1 percent of 0 to 18-year-olds suffered from head lice. Head lice were most common in primary school children; 7.1 percent turned out to be infected. “We think this is because children more often play close to each other where they have hair-hair contact,” says Thijs Veenstra of RIVM. It may well be the case that although it occurs more often in children, it is also reported more often. “I think that adolescents and adults are more likely not to report it.”
Because the parasite remains outside the body, a person does not develop a defense against lice. As long as the insects are not exterminated en masse, someone can become infected again and again. In 2010, the National Support Center for Head Lice came up with the idea of ’Lice Day’. This year it falls on Wednesday 9 March. The idea is that everyone has their hair checked that day in order to make the Netherlands lice-free in one day. The fact that it has now become an annual day shows that in practice this is still quite difficult. “If you check everyone at the same time, it takes longer for lice to reappear, but it’s just very easy to miss one egg or louse,” says Veenstra.
The female of the head louse sticks about five white eggs, the nits, to the hair per day. She does this with an adhesive that does not dissolve in water. The host can go for a swim or shower, but the eggs will remain. The eggs hatch after seven days. The young larvae immediately start sucking blood. Lice can live up to 20 days as long as they have blood to feed on.
Bedding and stuffed animals
Without blood, lice die within one to two days. That is why the RIVM deleted the advice to wash or freeze clothing, hats, bed linen and cuddly toys from the guideline a few years ago. The lice will die on their own if they are away from their food source.
This is probably the reason that the brother of the head lice, the body louse, has virtually disappeared from the Netherlands. Body lice do not attach themselves to hair, but to clothing. Their eggs are also glued to textiles. Like head lice, they need blood to survive. Veenstra: “I suspect that we see the body lice less because we change our clothes much more often than in the past.”
There is no such simple solution for head lice. According to Veenstra, the conclusion is simple. “We cannot eradicate the head lice. There’s just a lot of hair in the world. Getting rid of lice on one head is difficult, let alone anywhere in the world.”
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