Pediculosis is an ectoparasitic infestation caused by blood-feeding lice of the order Phthiraptera. Although pediculosis can infest any part of the body but term “Pediculosis” is used for head pediculosis.
Causes & Types
Pediculosis can be divided into following types based on their location and type of lice which causes it:
- Pediculosis capitis: Also known as head lice infestation which is caused by lice Pediculosis capitis. This is the commonest type.
- Pediculosis corporis: Also known as Pediculosis vestimenti or Vagabond’s disease. It is caused by body louse, Pediculus humanus humanus, also known as Pediculus humanus corporis.
- Pediculosis pubis: Also known as “crabs”. It is caused by Phthirus pubis which looks like crabs, therefore, called Crab louse.
Lice live by feeding on host blood and cannot survive for long without a host. Body lice are responsible for transmission of louse-borne relapsing fever, louse-borne typhus and viral encephalitis.
Symptoms
Pediculosis capitis is the commonest cause of lice infestation that is transmitted by close contact like sharing the bed, combs, brushes when children are playing, direct head-to-head contact etc. Children and women are are typically affected. Overcrowded communities provide an ideal setting for its transmission and infrequent combing and washing predispose to infestation.
After infestation, there is pruritus of the scalp. Pruritus intensifies after 3-4 weeks of infestation. Each egg or ‘nit’ may hatch one nymph that will grow and develop into the head louse. Lice feed on the blood of host once or often each day by piercing the skin with their tiny needle-like mouthparts. While feeding lice excretes their saliva, which irritates the skin and causes itching. Advanced cases complain of pruritus and boils in the scalp or glands in the neck. Unlike scabies, these lice cannot burrow into the skin. Eggs are always detectable even if lice are not seen. They resemble dandruff but can be differentiated by their firm adherence to hair (dandruff can be flicked of hair). They are seen as smooth surfaced oval structures attached to the hair at an angle of about degrees.
Complications may arise due to persistent scratching, includes excoriated papules, which develop a secondary streptococcal infection. Pustules, crusts, and matting of scalp hair characterize this stage. Enlargement of lymph nodes (lymphadenopathy) in the back of the neck (posterior cervical region) is a common presentation of pediculosis capitis.
hair at the back of head and back of ears are commonly affected by nits because these are areas which are least taken care of during grooming.
Pediculosis corporis also causes heavy itching of the body. Body lice are vectors for transmission of disease already mentioned. It affected individuals who are unable to wash off their clothes frequently. Most of these persons lack a home and hence the name, vagabond’s disease.Intense itching leads to searching of the body by the individual for the lice but they cling to clothes which make them difficult to find. Numerous petechial and erythematous macules, papules with hemorrhagic puncta, some in linear array and excoriation typify this disease. Commonly involved areas are upper back, over the scapula, shoulders,below axilla and waistline.
Pediculosis pubis is a sexually transmitted condition which is caused by pubic lice. They infest human pubic hair but may infest other areas like eyelashes causing pediculosis ciliaris. They affect areas like perineum, genitals, perianal region, thighs, lower abdomen and other hairy parts.
Diagnosis
Diagnosis of pediculosis is made by the typical finding of itching and demonstration of lice in head with the help of louse comb. The comb should then be examined for the presence of lice.
Pediculosis corporis can be diagnosed by severe pruritus in the trunk, especially in back that is out of proportion or existing skin lesions. Lice and nits can be demonstrated from the clothes.
A pubic louse can be diagnosed with the demonstration of nits, nymphs and adult lice on pubic hair either by removing it with forceps or by cutting hair and examining under lens or microscope.
Treatment
Pediculosis capitis treatment has to be given to all family members especially those sharing beds and combs with the patient. A single application of Gamma benzene hexachloride (1%), malathion (0.5%) or permethrin (2%) is very effective. It can be repeated after 10 days for more safety. Nits can be killed by applying kerosene (5%) or removed by combing the hair with a fine-toothed comb following application of vinegar (dilute acetic acid) that loosens them. Shampoo can be used to clean the scalp, antihistamines can be given to relieve itching and topical antibiotics for infection or lymph nodes enlargement.
Pediculosis corporis can be treated by washing clothes in boiling water and pressing with a hot iron. Alternatively, clothing can be powdered with disinfectants like DDT (10%), GBH (1%), pyrethrin or malathion. Improving personal hygiene and regular washing of clothes are crucial for preventing recurrence.
Pediculosis pubis can be treated by applying GBH (1%) or Permethrin (2%) on affected areas. Sexual partner of affected person should also be treated. Shaving hair off affected areas is helpful. Piperonyl butoxide and lindane can also be used.
