Medicinus – Cours de Médecine en ligne


(Last Updated On: )

I- Definition:

Ectoparasitoses, scabies and pediculosis, are human-to-human communicable diseases.

II- Gale:

Scabies, a contagious parasitic dermatosis, is caused by a mite, Sarcopte scabiei hominis, a mandatory human parasite.

Photo: female sarcopte (Sarcopte scabieu agent of scabie), a mandatory human parasite. (M.P. B denying Pinchart)

A- Pathogen:

The female sarcopte (0.4 mm long) is responsible for this disease. She digs a furrow into the corneal layer of the epidermis and lays her eggs at the bottom of it (Link 1). The adult lives 4 to 6 weeks, but only 24 to 36 hours outside the host. On the other hand, eggs live about ten days in the outdoor environment.

B- Epidemiology:

Scabies is mainly transmitted through direct human contact, it is also sexually transmitted. Sarcopte scabiei parasitizes millions of individuals worldwide on every continent, of all social levels and of all ages. Scabies occurs through cyclical epidemics, especially in the homes of the elderly. Since 1999, this parasitosis has been on the list of occupational diseases contracted in the hospital setting.

Photo: skin: scabiese (scabies) typical Intergdigital Lesions (Anofel)

C- Clinic: adult common scabies

The incubation period is 2 to 3 weeks, then an intense, generalized and nocturnal resurge appears, it is the major sign of common scabies. Specific lesions of scabies – scabieous furrows and beaded vesicles – should be sought in the interdigital spaces of the hands, the anterior face of the wrists, elbows, the anterior face of axillary hollows, the umbilical region, buttocks, the inner face of the thighs and nipples in women.

Photo: scabiosis (gale) Penile Chancre (Anofel)

Nodules, scabieous nodules, can be observed at the penis and anterior face of axillary hollows. These specific lesions may miss and be replaced by secondary lesions, scratching streaks, excobriated papules, eczema and overinfection (impetigo). The face, scalp, neck and upper back are rarely reached in the common form.

Other clinical forms and complications:

Photo: scabies (scabies) Plantar reach in children (Senegal) (Anofel)

Semiology can vary depending on the terrain.

In infants, the location of vesiculo-bubble lesions can be palm-plantar, and spread throughout the body.

In the elderly, the lesions are often atypical. There is a papulous, vesicular rash, scattered on the trunk, limbs and back, without furrow.

In immunosuppressed patients (corticosteroids, HIV, HTLV…), a massive, highly contagious infestation can be observed, it corresponds to the crusty or scab of The Norwegian. Erythematous papules are spread throughout the body, becoming crusty and hyperkeratosic ("floury"). Lesions can be found on the scalp and face.

E- Diagnosis:

Diagnosis can be difficult. The evidence of the parasite in the dander remains the reference. It requires the completion of a scraping with the curette or vaccinostyle on several sites allowing the collection of serous and dander. Microscopic examination between blades looks for the presence of adult sarcoptes, larvae, eggs or droppings. The negativity of this examination does not formally eliminate the diagnosis. However, the completion of a systematic test treatment, by a topical ascaricide, is also a source of error. Scabies should be among the differential diagnoses of any persistent or atypical pruriginous condition.

F- Treatment:

The treatment concerns the patient himself, his entourage, his clothes and his bedding.
Treatment uses topical scabicides or, more recently, an oral medication.

Active principle Specialty Form
Posology/mode of administration Effects
Benzyle Benzoate Ascabiol Lotion at 10% A: in the evening, for 24 hours, avoid scalp, face
E< 2 ans : 12 h max : prudence (diluer x 2 le produit) 2="" ans="" :="" 12="" h="" max="" :="" prudence="" (diluer="" x="" 2="" le=""></ 2 ans : 12 h max : prudence (diluer x 2 le produit)>
Skin irritation 


Synthetic Pyrethrins Sprégal Aerosol A and: body except face and scalp, 12 p.m. (night) Skin irritation 

Asthma (aerosol)

Scabcide Cream at 1% A: 12 p.m.
E – 2 years: 6 a.m.
CI E:< 2 ans, grossesse 2="" ans,=""></ 2 ans, grossesse>
Eczema Risk of toxicity
neurological, hematological and liver

After treatment with one of these scabicides, the pruritus may persist for about ten days, this post-natal pruritus should not lead to repeated applications. These products are not reimbursed by Social Security. These medications should not be applied to the mucous membranes and should be used with caution in children. The use of lindane-based products is questioned because of their toxicity.

Ivermectin Stromectol Tablets 200g/kg single CI or precautions< 15 kg , grossesse 15="" kg="" ,=""></ 15 kg , grossesse> Exacerbation of pruritus at the beginning of treatment

The cure will not be considered definitive until 4 weeks after treatment. This drug has a special place in the event of a community epidemic because of its ease of use. In case of crusty scabies, hospitalization in dermatology is essential.

It is necessary in combination with the treatment to disinfect laundry and bedding contaminated by washing at more than 60oC or if it is not washable by an insecticide spray or powder (higher toxicity) (Aphtiria®).

Contact subjects should be dealt with simultaneously.

III- Pediculosis:

Lice are blood-eating insects, a strict human parasite. There are three species of lice belonging to two genes: Pediculus humanus capitis and corporis, and Phtirus pubis. Transmission is human-to-human and direct in the vast majority of cases. These ectoparasites measure from 1 to 4 mm, are flattened dorso-ventraleally and equipped with 3 pairs of legs finished by claws. The female lays eggs: nits.

Features Pediculus humanus capitis (link 5) Pediculus humanus corporis Phtirus pubis (link 6)
Dimensions (L) The most common 3.5 mm The largest 4.5 mm Trapu 1-2 mm
Location Hair, hair Clothing Pubic hair or eyelashes
Features Frequency, child, benign Poverty, vector of disease Std
Photo: Adult Pthirus pubis (MEBx33) (Anofel)
Photo: a slow outbreak (Anofel)

A- Pediculosis of the scalp:

Photo: Scalp Pediculosis (Anofel)

Scalp pediculosis is the most common of pediculosis. It exists mainly among children in schools, of all social backgrounds and in adults with poor hygiene. The transmission is most often made by direct contact; indirect transmission (cap, hat, comb…) is much rarer.

It manifests itself in a pruritus initially located in the occipital region. It then predominates in temporal and occipital regions and can cause scratching lesions that can over-infect. Ardosted spots are sometimes observed. Live nits are dark (link 4) and close to the scalp and lice difficult to see (mobile and few in number: 10 /head).

B- Body pou:

Body pediculosis mainly affects individuals in precarious situations (homeless). Lice, Pediculus humanus corporis are found in clothing, they come to feed on the body. The stings can cause a local allergic reaction and are responsible for a pruritus. This is accompanied by a more or less urticarian rash, with scratching and eczema lesions. Lesions predominate in the covered areas (sleeves, scapular and lumbar region). In the event of a chronic infestation, there is often a leucomelanodermy of vagrants.

Body lice are potential vectors of serious diseases: trench fever (Bartonella quitana), exanthematic typhus (Rickettsia prowasekii) and recurrent cosmopolitan fever (Borrelia recurrentis).

C- Phtiriase:

Photo: Pthirus pubis (morpion) adult (Anofel)

Phtirius pubis or inguinalis is usually attached to pubic hair, but can affect other hairs including eyelashes (phtiriasic blepharitis of infants or children – a clinical examination for sexual abuse is essential). These stings cause small bluish lesions and sometimes quite large allergic reactions. The transmission of pubic pediculosis is mostly sexual (STD), non-sexual transmission is rare. Screening for other STDs may be offered.

D- Treatments of pediculosis:

Several insecticides are used in the preparation of lice: pyrethrins, natural or synthetic, organophosphates (malathion), organochlorines (lindane). The galenic forms and commercial presentations are very numerous, because these products are hardly considered medicines, therefore have no AMM and are not reimbursed by social security. They must have pediculicide and lenticide activity. The lotion is the most suitable galenic form (avoiding flow on the mucous membranes).

Example of products, which we think are particularly interesting (non-exhaustive):

Active principle Specialty Dosage Efficiency Effects
Synthetic Pyrethrins d-phenotrine 0.3% Item Lotion Pediculicide,
neurological irritation (low)
Prioderm Lotion Pediculicide,
Irritation, pulmonary, digestive, neurological
Synthetic Pyrethrin – pyperronyl butoxide Itax malation 


Lotion Pediculicide,
Ditto above

Recidivism after treatment exists, it may have several origins i) recontamination, (ii) poorly conducted treatment (in addition, the application time recommended by manufacturers is sometimes insufficient), iii) authentic resistance.

In practice, when a properly performed treatment is unsuccessful, it is necessary to change pharmacological class, for example, from pyrethre to malathion, or vice versa.

In case of scalp pediculosis, it is not necessary to treat the whole family but to monitor the whole siblings.

In case of pediculosis of the body, the disinfection of clothing and bedding is systematic, sufficient for some authors. It may be associated with treatment with pyrethrins or malathion.

The treatment of pubic pediculosis uses the same modalities as scalp pediculosis, but one of the drugs is more (pyrethre, piperonyl butoxide in®specific: Spray-Pax spray). Pubic pediculosis requires the treatment of sexual partners. It is best to

Treat all hair areas of the thighs and trunk and disinfect the clothes. Shaving pubic hair may be necessary in case of abundant nits.

E- Prevention:

Prophylaxis is based on good information and early detection of infected individuals. The preventive role of lice shampoos has never been demonstrated.



Dr. Bariout's Course – Faculty of Constantine

Exit mobile version