Scabies is a highly contagious skin condition caused by an infestation of the microscopic mite, Sarcoptes scabiei var. hominis. This parasite burrows into the outer layer of human skin, where the female mite lays eggs. The resulting symptoms, including rash and intense itching, are caused by an allergic reaction the body develops to the mites, their eggs, and their waste products. Scabies can occur virtually anywhere on the body, and it often affects the genital area, including the groin, penis, and vulva. This article explores the specific manifestation of scabies in these regions, modes of transmission, and necessary steps for complete eradication.
Scabies Mites and the Genital Area
When scabies infests the genital region, symptoms typically involve the scrotum and penis in males, and the vulva and breasts in females. The female mites tunnel into the stratum corneum, the skin’s outermost layer, to establish a permanent burrow. The genital region is one of the common sites for the infestation to concentrate.
The most prominent symptom is intense pruritus, or itching, which is often significantly worse at night. The body’s immune response to the mite’s presence creates characteristic lesions. These may appear as small, pimple-like red bumps, vesicles, or linear, S-shaped tracks on the skin where the female mite has burrowed.
A unique manifestation often observed in the genital area is the formation of scabies nodules. These are firm, reddish-brown bumps that can persist for months, even after the mites have been successfully eliminated. Nodules represent a localized, delayed hypersensitivity reaction to the remnants of the mites and their waste.
How Scabies Spreads
Transmission of scabies requires specific conditions because the mites do not survive long off a human host, typically perishing within two to three days without human skin contact. Consequently, brief casual contact, such as a quick handshake or hug, is usually insufficient to spread the infestation.
Transmission occurs primarily through prolonged, direct skin-to-skin contact, defined as a relatively long period of physical contact, often lasting 10 minutes or more. Because of the nature of the contact required, transmission is highly likely among household members and sexual partners.
Given the infestation’s predilection for the genital area, intimate or sexual contact is a common route of spread. Less common is transmission via shared items (clothing, towels, or bedding), but only if the exposure is prolonged. The risk of indirect transmission is significantly higher only in cases of crusted scabies, a severe form where the host harbors thousands of mites.
Steps for Diagnosis and Eradication
Diagnosis begins with a medical professional’s visual inspection of the skin and a review of the patient’s symptoms and exposure history. Clinical suspicion is confirmed by laboratory testing to identify the presence of the mite, eggs, or fecal matter (scybala). Confirmation of the diagnosis is important because the symptoms often mimic other skin conditions.
Diagnostic Methods
One common diagnostic method is the skin scraping, which involves superficially scraping a suspected burrow or lesion and then examining the collected material under a microscope. Another technique is the burrow ink test, where a washable felt-tip marker is used to color a suspected area. When the surface ink is wiped away, the ink absorbed into the mite’s serpentine tunnel remains, illuminating the characteristic burrow track.
Treatment and Environmental Control
Eradication requires prescription medication, as no effective over-the-counter treatments exist for human scabies. The standard first-line therapy is the application of a topical cream, such as 5% permethrin, applied to the entire body from the neck down and left on for eight to fourteen hours. For severe cases, crusted scabies, or when topical treatments are unsuccessful, an oral medication like ivermectin may be prescribed, often in two doses given about one week apart.
Simultaneous treatment of all close contacts, including household members and sexual partners, is highly recommended, even if they are currently asymptomatic. To prevent re-infestation from the environment, all clothing, bedding, and towels used by the infested person in the preceding 72 hours must be decontaminated. This is accomplished by machine washing the items in hot water and drying them on a hot cycle. Items that cannot be washed can be sealed in a plastic bag and kept away from body contact for at least 72 hours, as this exceeds the mite’s ability to survive off a host.