Scabies

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 scabei, human itch, or mange mites, are in the arthropod class Arachnida, 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 fomites (e.g., bedding or clothing). Sarcoptes scabei undergoes four stages in its life cycle; egg, larva, nymph and adult. Sarcoptic 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;