Scabies is one of the commonest dermatological conditions in the world. It is a parasitic skin infestation caused by a mite called Sarcoptes scabiei var hominis. The mite is so small that it is not visible to the naked eye. It burrows into the epidermis (top layer of skin), lays eggs, triggering a host immune response that leads to intense itching in response to just a few mites, (scabies is a Latin word that simply means to scratch). Scabies is a contagious disease primarily related to overcrowding and poverty. Scabies is transmitted from human to human by prolonged skin-to-skin contact with a person who has scabies.
Scabies affects people from every country, accounting for a substantial proportion of skin disease in developing countries. Globally, it affects more than 130 million people at any time and the prevalence varies from 0.35 to 46%. The highest rates are found in countries with hot, tropical climates, where infestation is endemic. Scabies is more prevalent in overcrowded communities with low socioeconomic conditions. Institutions such as child care facilities, group homes, and prisons are often sites of scabies outbreaks.
During a case study follow up, 81% of inmates of an orphanage in rural area of Maharashtra, India, were found to be suffered from scabies and all inmates were successfully treated with mass scabies treatment and health education. An epidemiological study conducted in rural community has reported the prevalence rate of scabies as 13%.
Scabies infestation is often complicated by bacterial infection, leading to the formation of skin sores and further complications such as septicemia, heart disease and chronic kidney disease. Young children and the elderly in resource-poor communities are especially susceptible to scabies; as well as to the secondary complications of infestation.
Although scabies is not a life threatening condition, yet it may be considered to be important from the public health point of view because of several reasons, namely it is found globally; severe itching is extremely distressing, social stigmatization; and indirect effects of various complications. Therefore more evidence for epidemiological links with cardiac and renal disease, better diagnosis, treatment, and public health measures are needed to control scabies.
Signs and symptoms of scabies include-
Itching (mainly at night)- Itching is the most common symptom, appears 2-6 weeks after the mite burrows in to the skin ( in a person who had scabies before, itching usually begins within 1-4 days).The most common places to have itching and rash are-
Infants and children who have scabies are often irritable.
Rash- scabies rash can look like tiny bites or pimple-like.
Sores- Intense itching of scabies leads to scratching. Scratching the itchy rash can cause sores and secondary bacterial infection.
Thick crusts on the skin (Norwegian scabies)- Sometimes in immune-suppressed patients, including those with HIV/AIDS, or persons who have conditions that prevent them from itching and/or scratching (spinal cord injury, paralysis, loss of sensation, mental debility) a severe form of scabies develops; it is called crusted scabies. Another name for crusted scabies is Norwegian scabies. Crusted scabies is characterized by vesicles and thick crusts that can contain thousands of mites. Persons with crusted scabies may not show the usual signs and symptoms of scabies such as the characteristic rash or itching because of patient’s altered immune status or neurological condition. However these persons are very contagious due to the presence of millions of mites and are important to identify as they are a significant source of reinfection to the rest of the surrounding community.
Human scabies is caused by a mite (human itch mite) called Sarcoptes scabiei var hominis. The mite is very small, barely visible to the naked eyes.
Scabies mites burrow into the top layer of the skin (epidermis), where the adult female lays eggs. The presence of mite proteins and faeces triggers an allergic reaction in the patient causing an intense itch.
Scratching can lead to infection of the skin with bacteria (particularly Staphylococcus aureus and Streptococcus pyogens), leading to the development of skin sores (impetigo). Impetigo can be complicated into deeper skin infection such as abscesses and immune-mediated complications as acute post-streptococcal glomerulonephritis (kidney disease) and possibly rheumatic heart disease. Up to 10% of children with infected scabies may show renal damage in resource-poor settings and, in many, this persists for years following infection resulting to permanent kidney damage. Recurrent infestations are common.
Transmission of scabies-
Scabies is usually transmitted by direct, skin to skin contact from infected person to another person; such as holding a baby, sexual activity, sharing a bed, school children holding hands. Close interpersonal contact is the main way of transmission. Sometimes people pickup itch mite from infested items such as bedding, clothes and furniture. The mite can survive for 48 to 72 hours without human contact.
Scabies can be diagnosed by the appearance of the skin, distribution of the rash and the presence of burrows and vesicles around the wrists and especially finger webs in adults and on the soles of the feet and ankles and sometimes the head in infants.
A doctor can examine patient’s skin from head to toe for the burrow marks of the mite and scabies nodules. Prolonged itching leads to the development of scabies nodules in adults; often found on the genital area, especially the penis and scrotum as well in areas around the breast.
Additionally, asymptomatic family members of the patient may also have burrows in the finger webs. If more than one family member has similar symptoms, this finding may favor the diagnosis of scabies.
For the confirmation of scabies, a skin sample may be scraped from the affected area (the hands between the fingers and the folds of the wrist) and can be examined under the microscope for the presence of scabies mite, their eggs and faeces.
Primary management of scabies: The aim of treatment for scabies is to suppress the discomfort due to the disease, to limit the risk for secondary infection and related complications such as (heart and kidney disease), and to limit the dissemination of the disease in the family and more widely in the community.
Products used to treat scabies are called scabicides, they kill scabies mites and some also kill mite eggs. Different topical scabicides may be used for the treatment of scabies such as permethrin 5% (caution in children aged under 6 months), 5% malathion in aqueous base, 10–25% benzyl benzoate emulsion or 5–10% sulphur ointment.
Use of oral ivermectin- It may be used in very closed communities, such as homes for the elderly. The current recommendation is to treat every inhabitant of such community.
Secondary management involves prompt treatment of the complications of scabies, such as impetigo using appropriate antibiotics or antiseptics.
Important tips -
Scabies infestation is frequently complicated by bacterial infection leading to the development of impetigo (skin sores), especially in the tropics.
Impetigo can be complicated by deeper skin infection such as abscesses, as well as serious invasive disease and sepsis in infants.
In tropical settings, scabies-associated skin infection can cause immune-mediated complications such as acute post-streptococcal glomerulonephritis (kidney disease) and possibly rheumatic heart disease.
The most important strategy for prevention is early treatment of those who show symptoms and all their contacts at the same time.
For control and elimination of scabies treatment of individuals with scabies and their contacts is not sufficient, there is increasing interest in a mass drug administration strategy.
Large studies of mass drug administration using oral ivermectin versus topical treatment are currently underway. Oral ivermectin single dose repeated after 7 days proved effective for the treatment and prophylaxis of scabies in an infected institutional environment.
An important aspect of control and elimination programmes is their integration into existing clinical and public health programmes and systems.
International Alliance for the Control of Scabies (IACS) is now working as a global network committed to this goal.