Lice on a person’s head

Lice on the head parasitized even among ancient people who shared their shelter from the weather with wild animals and with bats. It was these warm-blooded bats that caused the spread of parasites. Giant Saurodectes parasitized on early Cretaceous pterosaurs. After the death of the dinosaurs, lice adapted to new food objects and settled with bats in caves.

Description and brief description of the species

By changing the object of nutrition, lice and transformed themselves. During evolution, they significantly decreased in size and lost wings. Insects began to differentiate about 130–115 million years ago, since it was in the sediments of this period that wingless lice were found. Lice are highly specialized parasites and cannot change their host.

Interesting!

Scientists from the University of Illinois (USA) described adaptive features in lice parasitizing on different species of animals and birds. In birds or chicken lice a long narrow body that helps them hide in the beards of feathers, and insects living in rodent hair have an elongated indentation on their heads, with which they “fasten” to the hairs.

In humans, infection is caused by human lice, which have two morphotypes - head lice and pubic areas. They vary in appearance and have adapted to the type of hairs on different parts of the body. Head lice have a subtype - cootie. From headaches, head lice are distinguished by a more shortened body and color - more gray.

The elongated body of head lice is clearly divided into the cephalothorax and abdomen. The abdomen is much larger than the cephalothorax. After sucking a portion of blood, the color of the abdomen changes - it turns red. The long body allows the parasite to move quickly among the thick hair on the head. And tiny, from 2 to 4 mm, dimensions make it elusive.

Interesting!

Clothes and head lice can mutually transform when changing habitat. These morphotypes were divided and specialized only 72 ± 42 thousand years ago. Getting into the folds of underwear, head lice after several generations acquire the characteristic features of body lice. Despite the close proximity, they do not interbreed in nature, but under laboratory conditions they produce offspring capable of reproduction.

Six running limbs provide fast movement. The paws end with large claws in the form of sickles. With their help, head lice cling to hairs. Covering the hair, the claw tightly pressed against the lower leg, securely fixing the insect. It is these claws, adapted to covering hair of a certain section, that do not allow the parasite to live on the pubis or in the armpit hair, beard - there the hair is thicker. Anthony van Levenguk, who is quoted today by biology textbooks, admired the structure and functionality of louse claws.

Type and power

The oral apparatus of the parasite is ideally suited for feeding blood. Two sharp stylet, hidden in a soft tube that turns out, pierce the skin. At the distal end of the tube there is a nimbus of small hooks, with which the head louse is attached to the skin, sucking blood.

When the insect does not drink blood, the "proboscis" hides in the head section.The ducts of the highly developed salivary glands open into the proboscis. At lice bite their secretion enters the capillary in the scalp, preventing the formation of a blood clot. Once in the wound, saliva irritates the tissue, causing itching.

Eating, head lice suck out about 0.5 ml of blood at one time, and such “approaches” during the day the parasites make 4-5. Like all insects with incomplete transformation, nymphs of head lice are competitors of the imago in nutrition - they also suck out blood.

Interesting!

Head lice eat only human blood. When receiving the vaccine against typhus, the material for which was taken from infected insects, the question arose sharply: “How to feed head lice?” No matter how scientists struggled, offering laboratory animals to parasites, trying to feed them with the help of ingenious devices - head lice were persistent in their preferences. Researchers had to look for volunteers who agreed to feed the fickle on their heads.

Scientists have established another feature of the nutrition of parasites - head lice prefer the blood of girls aged 6-10 years. This feature was noted by Aristotle. In his essay Problemata, the great philosopher draws incorrect conclusions from correct observations, including the reasons for such selectivity.

With the invention of the microscope, scientists began to study in detail the internal structure of synanthropic insects. P. Borel, a healer at the court of King Louis XIV of France, described his observations in this way: “A terrible transparent louse allows you to observe how blood circulates in her heart.”

Parasite life cycle

Having reached puberty, the female lays up to 5 eggs per day on her scalp hair. For the whole period of life, which is 30 days in adult head lice, the population increases by 150 individuals. Oval eggs, covered with a dense shell, are called nits. This name was given to them by Aristotle. With the advent of the microscope, Aristotle's idea of ​​spontaneous generation of lice was refuted.

Under the microscope, gender differences in head lice are visible - bifurcation on the last segment of the abdomen in the male, which the female does not have. The copulative organ of the male is hidden inside the body and shines through the abdomen in the form of an elongated triangular formation. On the front pair of paws of the male there are claws used by him when mating to hold the partner.

Sexual intercourse of head lice lasts 20-70 minutes. During mating, the male introduces the seed material, which can be stored for a long time in the abdomen of the "lady". Already formed and covered with a dense shell eggs move along the oviduct to the exit. In the cap there are many tiny holes through which the male sex cells penetrate, fertilizing them.

The female attaches nits using the sticky secretion of special glands in the basal part of the hair. Here the temperature of the human head accelerates the maturation of eggs. How lice and nits look on the head, demonstrates a photo. After 7-10 days, larvae emerge from the nits, very similar to their parents, but much smaller in size. The larva feeds intensely, grows, molts several times, and after 6-10 days turns into an adult. Due to such short maturation of eggs and the rapid growth of larvae, breeding lice going fast.

Head lice are very temperature sensitive - the whole life cycle of the parasite depends on it. At normal human body temperature (36-37 ° C), the development of nits takes 4-8 days. A temperature drop of 13 ° C slows the development of the embryo by half. The lower limit of the temperature “comfort zone” is 22 ° C, and the upper limit is 40 ° C.

Interesting!

When the temperature drops to + 12 ° C, the females stop laying eggs, the activity of the parasite decreases. At temperatures below 10 ° C, insects leave the head of the host and creep in search of more comfortable conditions. The Bible has a description of the death of King Herod, from whose corpse "lice flowed like a spring that flows from the earth."And in the chronicles there is such historical evidence of the death of Bishop of Noyon: “there were so many lice on it that when he died, he had to be sewn into a leather bag so that the lice would not creep away before the burial, on the grieving guests.” In those days, for Christians, lice was a sign of holiness, testifying to the mortification of the flesh.

Despite the “attachment” to the object that provides food, parasites, when the opportunity arises, leave it, expanding the distribution area.

Infection pathways

Head lice in humans have long ceased to be a sign of a marginal personality. Increased attention to personal hygiene, scalp care, the use of ammonia hair dyes and the emergence of such powerful insecticides as DDT for several decades allowed the person to breathe a sigh of relief. But in the 70s of the XX century, the first alarm signal came from England. Here, when examined in the head, lice and nits were found in 13-17% of adolescents. An overwhelming wave swept across Europe and swept the United States.

Scientists have put forward various versions, ranging from long hair that was fashionable at that time among young people to the change in the biology of parasites and the formation of resistance. But the only reason why the "vagabond disease" became a national problem was never put forward.

The head louse is not very concerned about the cleanliness and neatness of the object. In close contact with the infected person, clothing, and bedding lice are transmitted another person in contact. Therefore, epidemics of infection with lice are often found in close groups - schools, kindergartens, summer camps, resorts.

Interesting!

Lice in water can live about 2 days, so people become infected by swimming in a pool or open water. Outside of its host, the parasite can live up to 2 days, and at a temperature of about 10 ° C - up to 10 days. The parasite removed from the hair hurries to return to its owner. Lice really “like” the baby’s clean, shampoo-washed hair. Here it is easier for them to eat, piercing thin skin, freed from keratinized scales of the epidermis, sebum, and dirt.

The rate of breeding of head lice also depends on the degree of overshoot. The more parasites on a person’s head, the less insects spend time looking for a mating partner.

Symptoms of Pediculosis

Pediculosis is a reaction of the body to bites of lice. Head lice manifests itself:

• itching
• erythema occurs on the surface of the skin in places of bites - swelling and redness, small bluish spots;
• visible yellowish crusts;
• bites can cause inflammation of the hair follicles on the head;
• the introduction of a secondary infection in places where the epidermis is damaged causes dermatoses, fungal diseases of the scalp.

A visual examination of the head on the hair reveals empty shells of eggs and nits. Untreated pediculosis is accompanied by inflammation of the regional lymph nodes on the head and neck, allergic dermatitis, furunculosis, conjunctivitis.

From the moment of infection with head lice until symptoms of lice it may take several weeks. It is easy to detect parasites - nits on the hair are clearly visible in any light and special devices are not needed to detect them.

Lice treatment

To get rid of lice The pharmaceutical industry produces a variety of insecticides on the hair of the head:

• For the treatment of pediculosis in adults, agents containing insecticides are used - emulsions MedifoxMedilis-Super, Pedilin shampoos, HigiaPediculen Ultra Spray Aerosol Steam Plus, cream nyx.
  

  

• Many drugs are based on liquid silicone. They are safe for the human body, so such drugs are recommended for elimination of lice in children. This group of drugs includes Nyuda spray, Paranit Sensitive.
• Against lice use drugs based on vegetable, mineral, essential oils - sprays Avalanche, Pedicule-ultra.
• In combination products include, in addition to a complex of insecticides, natural acids - Bubil, Spray Pax, A-Par, Paraplus. Means additionally care for the scalp and hair.

Despite the fact that pediculicidal drugs effective and quickly relieve problems, they do not affect nits, so the treatment must be supplemented by combing the hair. To do this, use a special comb with a fine pitch of metal grooved teeth. Lice comb maybe electric, when combed out, an electric discharge affects live lice on the head. To completely get rid of head lice, repeated treatment is necessary after 7-10 days, during the period when nymphs appear from nits.

Disinsection of women during gestation or lactation and children require a special approach and the selection of special tools. Safe medicines that improve the condition of the hair on the head and effectively fight against head lice - NOC, Nittifor, Nyuda, Paranit, Lavinal and others.

Many patients prefer not to use "chemistry". For them there are folk remedies for lice on the head:

• vinegar solution;
• hellebore water;
• decoctions of pomegranate and lemon balm;
• essential oils: ylang-ylang, cloves, anise, tea tree ;
• homemade ointments from ledum, cranberry, hellebore;
• fruit and berry acids;
• tar soap.

Modern methods pediculosis treatment they should not reject the experience of past generations, accumulated in the "bloody" struggle with insects, which went with a person the whole path of development from primitive to intelligent.