Biological peculiarities and Medical importance of the Lice family

Lice fall into the class insecta of the order Anoplura

. Their bodies are flattened, dorso-ventrally. Lice are wingless insects with shortlegs. Order Anoplura displays incomplete matamorphosis. Lice are divided into the head luse (Pediculus humanus capitis); body (clothes) louse (pediculus humanus humanus) and the crablous (phthirus pubis).Morphology

Adult louse is 2-5mm in size, male is smaller than female. Body is divided into head, thorax and abdomen. Conical head carries 2 simple eyes, 2 five-segmented antennae, and retractile proboscis. Thorax consists of 3 fused segments and carries 3 pairs of short legs (which end with single tarsal segments and single claws) and one pair of respiratory spiracles. 8-segmented abdomen carries 6 pairs of respiratory spiracles on each side of the first 6 segments, spring-like aedeagus protruding from the posterior end (male). The last abdominal segment of female is notched. Two triangular processes (gonopods) are located on the vagina's sides Eggs (nits) are whitish, oval, operculated (crown-like), 0.7-0.8 mm in size. Nymph resembles the adult louse but is smaller and sexually immature.Life cycle

Female louse lays about 10 eggs daily. Eggs are cemented to hairs or to fibers of clothes. Eggs hatch in about one week. Nymphs feed on blood and pass through 4 instairs. Louse emerges in about two weeks. Lice are permanent ectoparasites, they die out of the host's body. If the body temperature rises (e.g fever) or falls (e.g death) lice leave the host, trying to find another host. They feed on blood several times a day.Disease transmission (body louse)

Epidemic typhus caused by Rickettsia provaceki. Rickettsia invade the gut wall of the louse and multiply. After rupture of epithelial cells they are liberated into louse's lumen and come out with the feces. The life of louse is shortened by infection from 4 to 6 weeks (normal span of life) to approximately 10 days. Mode of transmission of epidemic typhus is by contamination of bite wound or mucous membranes by feces; inhalation of dust containing rickettsia.Trench fever caused by rickettsia quintana is transimitted in the same way as in the case of epidemic typhus. but the life of the louse is not endangered. Epidemic relapsing fever caused by Borrelia reccurentis. The organisms disappear from the gut of the louse and appear in the body fluid. Infection occurs by crushing the louse and contamination of the bite wound with the body fluid containing borrelia.Pediculosis (vagabond's disease) means heavy infestation of hair with lice (pediculus humanus capitis). The main symptoms of pediculosis are cutaneous lesions and pruritis.Crablouse (Phthirus Pubis)

Infects pubic region and armpits, and is the causative agent of pediculosis pubic. Crablouse is smaller than the lead louse of body (clothes) louse. Its body is short, thorax and abdomen are practically fused together. Crablouse is an ectoparasite, the causative agent of pediculosis pubic; does not take part in disease transmmision. Prevention of lousiness (pediculosis) includes regular body washing with simultaneous change of linen, maintenance of cleanliness, Pubic accommodations should be kept clean. Special insecticides soaps and sprays are used for extermination of lice and nits.I am Funom Theophilus Makama. I advertise through writing. As a platinum expert Author, I write lots of articles and hence promote interested websites, companies, groups, organizations, and communities through publishing and distributing my articles. For more information on this interesting venture, click on the link belowhttp://funom-makama.blogspot.com/2010/07/advertising-contracts.html

Biological peculiarities and Medical importance of the Lice family

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