Arthropods Insecta Arachnida Crustacea Diptera Siphonaptera Hemiptera Anoplura
Medical importance Vector Cause disease Mechanical Biological Dermatitis
Mechanical Biological Direct Propagative Indirect Cyclopropagative Cyclodevelopmental Transovarian
Development (metamorphosis= change of form or structure) Egg Larva Egg Nymph Complete Pupa Adult Incomplete Adult
Order Anoplura Lice
Anoplura (Lice) Family Pediculidae Family Phthiridae Pediculus humanus capitus (head lice) Pediculus humanus corporis (body lice) Phthirus pubis (pubic/crab lice)
Development Egg Nymph Incomplete Adult
Pediculus humanus capitus (Head lice)
Morphology Shape: Body compressed dorsoventrally. Wingless Size:2-4mm Color: brown Head: 2 compound eyes, and 5 segments antenna Thorax: 3 fused segments and 3 pairs of stout and well developed legs Abdomen: 7 segments with 6 pairs of respiratory spiracles
Male and female lice Male ends by protruding aedegus Female is notched with 2 gonopodes and vagina
Phthirus pubis (crab, pubic louse) Found in pubic hair, axilla, eye brows and lashes and other hairy parts.
The Phthirus pubis (pubic louse) Adult is shorter, broader than pediculus Thorax : bigger than the abdomen 1 st leg less developed than the other 2 legs Abdomen: 5 segments Lateral abdominal processes Spiracles: Thoracic & abdominal
The head and body louse are similar but the body louse is larger paler and with long antenna. While the pubic louse is shorter and broader.
Bionomics Obligatory, permanent ectoparasites leaving the hosts if dead or feverish. Highly host specific. All stages are blood sucking. They take several blood meals during the day. Live for about 30 days. If a louse crawls off of a head, it dies within 2 days
Life cycle The cycle takes 2-4 weeks. Adults live for 1 month and lay 200-300 eggs (nits). The eggs are cemented to hairs or clothes They hatch to give nymphs that resemble the adults but: Smaller Paler in colour No external genitalia. Than they molts and give the adults
Nits (eggs) The size of egg is 1mm long, oval and opperculated. Firmly attached to the hair close to the scalp Nits are usually found on the hair behind the ears, at the back of the neck, and above the forehead. Do not mistake for dandruff, which can be easily blown off. Hatch 7 days after being laid.
A photo of a nit, or head lice egg.
Medical importance Vector Cause disease Biological Epidemic typhus Trench fever Epidemic relapsing fever Pediculosis Phthiariasis
Pediculosis & Phthiriasis Infestation of scalp, body or pubic hairs with lice Skin irritation, dermatitis Papule formation Pediculosis Head lice Body lice
Contracting Head Lice Head lice crawl quickly from head to head when in close contact Cannot fly, jump, or hop Head lice can be transferred when personal objects are shared; combs, brushes, hats Spread by contact especially in overcrowding condition, like trench and camps during wars, in jails and in the schools.
Recognizing Head Lice Tickling feeling on scalp Itchy scalp Feeling of something moving in the hair Irritability Sores on head from scratching Presence of nits, nymphs, and/or adult head lice
Treating & controlling Head Lice A. Licid B. Remove nits C. House cleaning D. Prophylactic measures
Treating Head Lice Scalp is treated with Licid,.. BUT: Talk to your doctor: If a child is under the age of 2 If you are pregnant or breastfeeding
WHY Removing nits? Removing nits will reduce hatching of eggs that were not killed with treatment will allow you to notice if a new infestation occurs Head lice products are not 100 % effective HOW to remove nits? Use fine-tooth nit comb or thumb nail/first finger to grab the nit and slide it off the hair shaft Place nits in a plastic bag, seal and put in garbage Check and remove nits daily for 2-3 weeks.
Housecleaning Wash in hot, soapy water: Headwear, combs, brushes, pillowcases, towels, bed sheets Items that cannot be washed should be stored in a sealed plastic bag for 2 weeks Vacuum surfaces where heads have rested Sofas, car seats, helmets
Controlling the spread of Head Lice Discourage head-to-head contact and sharing of hats, scarves, brushes, combs and headwear. Check heads of all people in close contact. Treat all family members with head lice at the same time. Check young school-aged children weekly for head lice; more often if there is an outbreak
Body lice In chronic conditions the skin become pigmented, thickened and tough, a condition known as Vagabond disease.
Phthiriasis Due to heavy infection of pubic lice. Manifested as dermatitis in pubic area chest eye lashes and brows and beard.the infection acquired by sexual contact,using contaminated towels, linens and toilet seats
The phthirus cause only phthiriasis which is a severe irritation condition for the skin.
Phthiariasis in eye
Epidemic (louse-borne) typhus Typhus is a group of infectious diseases that are caused by the bacteria of the genus Rickettsia. There are several types of typhus diseases: Epidemic (Lice) Endemic (Flea) Scrub (Mite) The symptoms of typhus are usually similar, but can vary in severity depending on the specific types; fever, skin rashes, headaches and muscular pain.
Epidemic typhus Causative organism: Rickettsia prowazeki Vector: head and body lice Clinically: as endemic but severe NOT by louse bite Treatment: Doxycycline
Mode of transmission Propagative, the Rickettsia invades the gut epithelium cells and multiply than they rupture toward the lumen of gut. So the Rickettsia pass with faeces or vomit of insect. The body fluid and saliva contain no Rickettsia. So the bite of louse is not infective.
Mode of infection Deposition of faeces on broken skin. Crushing of louse. Inhalation of dried faeces contact of contaminated fingers to the mucous membranes.
Trench fever (5 days fever) Received its name during World War I, when millions of troops living in close, unhygienic quarters were infested with body lice and infected with trench fever. Causative organism: Rickettsia quintana Type of transmission: Propagative Mode of infection: as E typhus. Clinically
Epidemic relapsing fever Causative organism: Borrelia recurrentis Type of transmission: Propagative Mode of infection: only by crushing Clinically: onset is abrupt, with fever, headache, and muscle pain that persists for 4 to 10 days, followed by an afebrile period of 5 to 6 days correlated with the absence of spirochetemia. Usually, a single relapse occurs in louse-borne relapsing fever. Bony aches, splenomegaly and raches.
Medical importance Species Disease organism Mode of infection Head and body louse Epidemic typhus fever Rickettsia prowazekii (in epithelium of mid gut) contamination of wound by faeces and contamination of conjunctiva or mucous membrane by finger or inhalation of dried faeces Trench fever Rickettsia quintana (in mid gut) Inhalation of contaminated dust by dried faeces of louse Body louse Epidemic relapsing fever Borrelia recurrentis ( in tissue outside the gut ) By crushing louse on skin abrasions or mucous membrane Pediculosis (Vagabond disease) The skin harboring a large number of lice and become tough and pigmented.
Control of lice For the head lice:-cut the hair short and use the comb with closely set fine teeth to remove the lice The use of the non toxic concentrations of insecticides (to minimize their toxicity) like D.D.T, malathion, pyrethrum, gammexane, Bygon, or sevin by using them as dust, lotions emulsions or shampoos. Licid lotion is more effective to penetrate the eggs than the shampoo. For the body lice :-proper bathing, boiling and cleaning of the clothes and dusting them with non toxic conc. of insecticides. Or by using of superheated steam to kill Rickettsia in the clothes
Control Phthirus Pediculus Shaving & cleaning Bathing with soap & water Applying 1% Lindane If eye lash, brow or moustache Forceps removal Yellow oxide of mercury ointment
Life cycle