Scabies While sitting around your house, watching television, you notice that you have been scratching your arm and in between your fingers for a little while. After taking a closer look you notice something that you assume is a rash and just ignore it. The next day however you notice that the rash has spread and that you think you see burrows in your skin. Then it hits you, the weekend that you spent away on vacation in that not so expensive hotel to save a couple of dollars has now cost you more money in the long run. You must go see your doctor to be treated for scabies! Scabies mites are distributed worldwide, affecting all races, ages and socioeconomic classes in all climates. Sarcoptes sca bei, human itch, or mange mites, are in the arthropod class Arachnid a, subclass Acari, family Sarcoptidae.
These mites burrow under the skin, living in linear burrows. Other races of scabies may cause infestations in other mammals such as domestic cats, dogs, pigs, and horses. It should be noted that races of mites found on other animals could not establish infestations in humans. They may cause temporary itching due to dermatitis but they do not tunnel into the skin. The mode of transmission is primarily person-to-person contact. Newly emerged impregnated females will crawl onto the uninfected person.
The mite will hold onto the skin using suckers attached to the two most anterior pairs of legs. They will then burrow into the skin. Transmission may also occur via fo mites (e. g.
, bedding or clothing). Sarcoptes sca bei undergoes four stages in its life cycle; egg, larva, nymph and adult. Sar coptic mites form definite burrows under the skin in which females deposit eggs. Females deposit eggs at 2 to 3 day intervals as they burrow through the skin.
Eggs are oval and 0. 1 to 0. 15 mm in length. Incubation time for eggs is 3 to 8 days. After the eggs hatch, the mites migrate to the skin surface and molt. The larval stage, which emerges from the eggs, has only 3 pairs of legs.
This form lasts 2 to 3 days. After larvae molt, the resulting nymphs have 4 pairs of legs. This form molts into slightly larger nymphs before molting into an adult. Larvae and nymphs may often be found in short burrows or hair follicles. They look similar to adults, only smaller.
Adults are round, sac-like eyeless mites. Females are 0. 3 to 0. 4 mm long and 0. 25 to 0. 35 mm wide.
Males are slightly more than half that size. Mating occurs on the skin surface. Afterward, the impregnated female will burrow into the skin and spend the remaining 2 months of her life in tunnels under the surface of the skin. Males are rarely seen. They make a temporary gallery in the skin before mating. When a person is infested with scabies mites for the first time, there is usually little pathology for the first month (range 2 to 6 weeks).
After this time and in subsequent infestations, people usually become sensitized to mites and symptoms generally occur within one to four days. Mites burrowing under the skin cause a rash, which is most frequently found on the hands, particularly the webbing between the fingers; the folds of the wrist, elbow or knee; the penis; the breast; or the shoulder blades. Burrows and mites may be few in number and difficult to find in some cases. Most commonly there is severe itching, especially at night and frequently over much of the body, including areas where no mites are living. A more severe form of scabies that is more common among people with immunocompromised states is called Norwegian scabies, characterized by vesicles and formation of thick crusts over the skin, accompanied by abundant mites but only slight itching.
Complications due to infestation are usually caused by secondary bacterial infections due to scratching. Most diagnoses of scabies infestation are made based upon the appearance and distribution of the rash and the presence of burrows. Whenever possible scabies should be confirmed by isolating the mites, ova or feces in a skin scraping. Scrapings should be made at the burrows, especially on the hands between the fingers and the folds of the wrist. Alternatively, mites can be extracted from a burrow by gently pricking open the burrow with a needle and working it toward the end where the mite is living. The most widely used treatments in the U.
S. today are Lindane (K well (R) ), Permethrin (E limite (R) ) and Crotamition (Eur ax (R) ). In addition, Ivermectin (Stromectol (R) ) has been used for the Norwegian form. Package instructions should be followed carefully. Some require only one treatment.
However, a second treatment may be indicated 7 to 10 days following the first treatment. Itching may persist for a week or more after treatment and does not necessarily indicate a treatment failure. Oral antihistamines (e. g. Diphenhydramine = Benadryl or Hydroxyzine = Atarax) can also be used simultaneously with the. Since the scabies mite cannot live more than 24 hours away from a host, insecticide treatments of the household are not needed.
It is recommended that when treatment is initiated, bedding and undergarments should be removed and washed with hot water. People who have had skin-to-skin contact (including household members and sexual partners) should receive prophylactic treatment.