W

ith the geriatric population on the rise, institutions for the elderly in all formats, including assisted-living facilities and nursing homes, are rapidly being built to accommodate it. However, due to these living arrangements, the geriatric population is at risk for infectious diseases, particularly scabies and pediculosis. Scabies has existed for over 2,500 years, with millions of cases detected yearly. Scabies is an intensely pruritic and highly contagious infestation of the skin caused by Sarcoptes scabiei. Pediculosis is an infestation of the hairy parts of the body or clothing with adult lice, eggs, or larvae.

Scabies

       Despite its long existence, there is still no effective method to prevent scabies from spreading. During the last 20 years, the number of patients infected by scabies has been increasing. Scabies has caused major problems in nursing homes, particularly in debilitated patients. The risk factors for infection with scabies among nursing homes include age of the institution (more than 30 years), size of the institution (more than 120 beds), and the ratio of beds to healthcare workers (more than 10:1).¹
       Due to its chronic undiagnosed condition, scabies is sometimes referred to in laymen terms as “7-year itch.” The word scabies is believed to originate from scabere, a Latin term meaning “to scratch.” Our ancestors falsely believed that the disease resulted from poor hygiene. Scabies does not make any distinction in socioeconomic levels, age, gender, race, or standard personal hygiene. The scabietic mites are motionless at room temperature and unable to fly from person to person. Therefore, transmission requires direct skin-to-skin contact with an infected person. Occasionally, there are cases caused by contact with contaminated clothing or bedding.
       An adult female mite is tortoise-shaped and only about 0.3–0.4mm in size. The mite has 8 legs. The male mite is about half the size of the female and mates with the female on the skin surface. Both male and female mites have the lifespan of about 1 month; they can live up to 3 days off of a host’s body environment. After being transferred from 1 host to the other, the female mite will quickly burrow beneath the epidermis and lay eggs. The eggs will hatch in about 3–4 days. A delayed type-IV hypersensitivity reaction to the mites, their eggs, saliva, and scybala (packets of feces) occurs within 2–6 weeks of infestation. This inflammatory reaction is responsible for the intense pruritis that is the hallmark of the disease. Pruritis is intensified at night with no known cause. Patients will show signs of infection after about 2 weeks or more. However, patients who have been previously infected will develop the symptoms 1–4 days after being re-infected. The burrows present as lesions with short, elevated, serpiginous tracks—thin (about the width of a human hair), short (about 2–3mm in length), and gray. A small papule may appear at the end of the burrow or occur independently. The burrows typically reside on the hands, interphalangeal finger webs, wrists, waistline, and anterior and posterior axillary folds. They can also be found on the external genitalia, nipples, and buttocks. The head and neck are usually spared.
       Scabies can exist in different forms. Nodular scabies comprises about 10% of the cases and usually resolves spontaneously after weeks or months. The nodules are 5–20mm in diameter, red, pink, tan, or brown in color, and smooth. The nodules can be found on the penis, scrotum, axillae, waist, buttocks, and areolae. The infected location may resolve with postinflammatory hyperpigmentation. The second form of scabies is bullous scabies, where bullae and vesicular lesions are common. A distinctive, highly contagious form of scabies—known as Norwegian scabies, crusted scabies, or keratotic scabies—has a predilection for individuals who are immunocompromised (ie, those infected with HIV and organ transplant recipients), aged, debilitated, or mentally impaired. The disease was first found in Norway. The first case was reported by Danielssen and Boeck in 1848,who mistook the disease as a variant form of leprosy.² In 1851, Hebra accurately diagnosed the disease as a cause of scabietic infection.² The main difference between keratotic scabies and regular scabies is simply the number of mites present on the host. In regular scabies, on average, the number of mites on a host at any 1 time is about 10–15 mites (with the range of 3–50). In keratotic scabies, the patients will be infected with thousands to millions of mites. Clinically, keratotic scabies differs from regular scabies in 2 ways: its skin manifestation is much more severe, and it is usually not very pruritic. Keratotic scabies may be present for years. As stated above, keratotic scabies usually infects immunocompromised patients, leading to decreased inflammatory reaction and decreased pruritic presentation. In patients with keratotic scabietic presentation, HIV status should be determined.
       The differential diagnoses of scabies comprise a lengthy list of different skin manifestations (see Table 1).

Table 1

       Diagnosis for scabies is relatively easy. A sample may be taken from the hands, finger webs, wrist, waistline, etc. The sample is then examined under a magnifying glass to detect the mite. A drop of mineral oil is placed on the suspicious papule or burrow, and the area is then scraped or shaved with a scalpel blade. Under a microscope, the specimen is examined for mites, eggs, or scybala. The presence of any 1 of these 3 findings confirms the diagnosis. A negative scraping does not exclude scabies infestation. Early diagnosis is important. Anticipating secondary infection, such as Staphylococcus aureus, and potential epidemic outbreaks is critical when dealing with scabies.
       Infected individuals and close physical contacts should be treated simultaneously, whether or not the symptoms are present. Sexual partners and close personal or household contacts within the last month should be examined and treated prophylactically. Bedding, clothing, and towels should be decontaminated by machine washing or dry cleaned and removed from body contact for at least 72 hours. Thorough cleaning of the patient’s room is recommended.
       Currently, a treatment of choice for scabies is 5% permethrin (Elimite® Cream, Allergan, Inc., Irvine, Calif, or Acticin® Cream, Bertek Pharmaceuticals, Inc., Durham, NC) cream or 1% cream rinse (NIX® Cream Rinse, Insight Pharmaceuticals Corp., Blue Bell, Pa). Permethrin is a synthetic pyrethroid, formed by the modification of the molecular structure of pyrethum, the flower heads of Chrysanthemum cinerariaefolium. It is also used in veterinary practice, animal husbandry, and agriculture for the control of arthropod pests and ectoparasites. The solution is applied to the skin from head to toe at bedtime and washed off the next morning. It is recommended that the cream be applied to cool, dry skin of the affected bodily areas, including the palms of the hands, soles of the feet, groin, under finger nails, and the scalp and left on for about 8–14 hours.
       Some suggest that patients should apply a second treatment 1 week later to secure the uncovered areas during the first treatment. All lesions should be healed within 4 weeks after the treatment. If the symptoms persist, the patient may be re-infested and may require further evaluation and treatment. Permethrin is an expensive medication. Additionally, it can be cumbersome to apply the medication throughout the body, and this may cause noncompliance. Because less than 2% of the lotion is absorbed into the skin, the potential toxicity of the medication is low.³ Its side effects include mild, transient burning, stinging, redness, and rash.

       Editor’s note: Part 2 of this article, featuring more treatment options for scabies as well as an in-depth description of pediculosis, will appear in the June issue of ECPN.