Welcome to the session about lice. This lesson has been prepared by Jovin Kitau Professor and from the Kilimanjaro Christian Medical College in Moshi. Lice belong to order Anoplura. The order is composed of organisms that suck blood. There are three organisms in this particular order that are known to parasitize human beings, and these are, pediculus humanus humanus, the body louse, pediculus humanus capitis, the head louse, and pthirus pubis, the crab louse or the pubic louse. Pediculus humanus humanus and pediculus humanus capitis are the subspecies in pediculus humanus species. Let's start with the body louse, pediculus humanus humanus. Pediculus humanus humanus is a wingless insect that is dorsoventrally flattened. It has one pair of inconspicuous eyes and three pairs of well developed legs that end up in strong claws. The females have lateral female organs in the bifurcated tip of the abdomen, Which facilitates clasping of the fibers when the female lay eggs. In terms of the life cycle, both sexes, males and females would feed on blood. And they undergo incomplete metamorphosis. The eggs would hatch in six to ten days after laying, and at temperatures between 21 and 36 degrees centigrade. However, they cannot survive more than one month. The nymph emerges through an operculum, which is an opening at the tip of an egg. And they undergo three moults and in two weeks they become adults. Adults and nymphs take blood at least two to five times a day throughout theirlife. Adults live for about a month, and females lay about 200 to 300 eggs in their lifetime. In terms of epidemiology and transmission, the ovas are distributed worldwide, however they're much more distributed in temperate areas. These are actually the true ectoparasites simply because they cannot survive for long away from the hosts. They need blood and warmth. Transmission is through close contact with infested people, especially where individuals are overcrowded. In refugee camps and overcrowded jails, or where people are congregated. Following disasters such as famine and drought, this infestation becomes prevalent. Infection peaks during cold weather. This is the time when individuals would put on a lot of clothes, which are rarely changed. Sharing of clothing and bedding also facilitates transmission. Lice will live between 15 degrees centigrade and 38 degrees centigrade, and they die about 40 degrees centigrade. When individuals are sick and temperatures are very high or when individuals die, the lice would abandon the bodies and seek for new hosts. Another organism is head louse, pediculus humanus capitis. The head lice are confined to the scalp. The morphology very much resembles that of the body louse. Eggs are cemented to the hair at the base, and especially behind the ears and the back of the neck, usually they are brought into view when the hair grows. Transmission is through close contact where the heads touch. Sharing of combs and hats can also facilitate transmission. There are usually no noticeable signs of this particular infestation. However, in very heavy infestation, scratching may result in bacterial and fungal infections of the scalp. It is mainly hygienic and aesthetic reasons. Simply because individuals who are infested, their social status is lowered. It is not known to be a vector of any disease. Another organism is pthirus pubics, which is the pubic louse. This is found mainly in genital and inguinal areas. They prefer areas of the body which are thick but not very densely covered with hair, and particularly the beards, the mustache, chest hair and eyelashes. There is less differentiation between the thorax and the abdomen of this particular species, and which is what gives them the characteristic name the crab louse. The first pair of legs is relatively underdeveloped, whereas the two posterior legs are very well developed with very heavy claws. In terms of the life cycle, it very much resembles that of pediculus species. Females lay about 150 to 200 eggs, which are slightly smaller than those of pediculus species. Eggs are cemented to hairs of the genital and perianal regions. Infection is acquired mainly through sexual contact, although it may also arise from discarded clothing and shared beddings. The crab lice is not known to be a vector of any disease. In terms of the medical importance of lice, An infestation due to lice is called pediculosis, and in this particular case, under heavy infestation, the skin becomes pigmented and tough, a condition that is called vagabond disease. Frequent feeding and injection of saliva into the body introduces toxic effects, which are such as the weariness, irritability and severe itching. Scratching may lead to inflammation and secondary bacterial infection in areas that are infested. For most people, it is an aesthetic nuisance, simply because it lowers their social status. And then, apart from being a nuisance, the body lice act as important vectors of infections such as epidemic typhus, caused by rickettsia prowazeki, epidemic relapsing fever, borrelia recurrentis, and trench fever, rochalimaea quintana. In terms of diagnosis, the infestation is suspected from an individual with a history of itching and scratching. There's darkening of skin and hardening of skin in individuals who are infested. However, in pubic lice, the skin tends to be bluish or having bluish spots. But then black spots may also be seen in underwears if the louse infestation is present. Adults and nymphs and eggs may be found on hair of scalps, on body hair, or on seams and folds of clothing. Louse eggs fluoresce under UV light. In terms of the control, the body lice can be eradicated by changing and washing clothes, normally at temperatures hotter than 60 degrees centigrade. Preferably if such clothes are soaked for 30 minutes, that becomes ideal, so is when such clothes are ironed. Shaving of hair, both pubic and head hairs, is also effective in controlling infestations by lice. The regular washing of soap or regular washing with soap and water, and combing hair with both steel or plastic comb is also effective in controlling this infection. However, combing would not necessarily remove the eggs of lice, simply because they are firmly glued onto the fibers. However, this may reduce the number of nymphs and adults lice. Under epidemic conditions, insecticides may become useful in what is called mass delousing campaigns. And in this case, 10% DDT or gamma benzene hexachloride powder, when blown at 30 grams per person, between the body and clothing is also effective. So is the emulsions of 2 to 5% DDT and 0.1% hexachlorohexane applied to the head, and left for 24 hours before washing. There are also lotions and shampoos that contain permethrin, temephos, and malathion, and also carbaryl, which are effective in controlling or killing lice. Thank you for listening.
