Epidemiologic Assessment of Scabies: Actuality of Airborne Transmission and Additional Standards to Reduce Spread of Contagion and Reinfestation

Abstract

Scabies are caused by parasites that live their entire life within the outer layers of the epidermis. When dislodged either by gravity, friction, motion, wind, or static electricity, they assume great risks to survival. Innate abilities to sense human smell and heat, to move over short distances, and to penetrate the skin quickly allow them a fighting chance to find a new host if they land within 4 inches of a human. Females store sperm, allowing one mite to begin a colony. Transmission is by person-to-person, fomite, and airborne. They are aerodynamic, light, and balloon-shaped, all making airborne transmission easier than previously understood, as well as explaining the dissemination of mites beyond the normal zones of activity of the index case. Presently, the bulk of the medical literature suggests that transmission from inanimate objects poses little concern in common scabies. However, as mites can navigate through cloth gowns, one might consider protection with more protective garb. Mites cannot penetrate through waterproof clothing, and thus, this attire should be recommended to avoid reinfestation and infesting others. Sofas, chairs, office furniture, and car seats on which an index case might sit need to be covered with plastic sheeting. Given that the half-life of ivermectin is 18 hours and that mites dehydrate within 96 hours, strict transmission controls are only needed for 3 days to avoid reinfestation as well as infesting others. Key Points Scabies is an intensely itchy skin rash caused by a burrowing mite that infects the outer layers of the skin. Scabies is contagious and usually spread by direct, prolonged skin-to-skin contact with an infected person; however, fomite and airborne transmission are also operative. Precautions should be in place to avoid direct skin-to-skin contact between a patient with scabies and visitors. Water-proof clothing would be advisable, especially in cases involving Norwegian scabies. Success rates with oral ivermectin would more closely approach 100% if all transmission factors, including fomite and airborne, were addressed.