Infestations

Abstract

Despite all the available pediculicides and scabicides that have been developed in this century we still find ourselves facing a treatment dilemma. Although body lice are not abundant in the United States, they are still found in the homeless populations of our major cities. With the development of dichlorodiphenyltrichloroethane (DDT) in the early 1940s there was no longer a reason to pursue the basic biology of lice. Cheap and effective treatments such as DDT reduced the lice supply and with them the louse-borne diseases that went with the body louse. These diseases, such as trench fever caused by Bartonella quintana, are re-emerging in the United States and in other countries. Head lice and crab lice have never been studied as possible vectors of disease, because they were not usually found in the same population and because, unlike body lice, no laboratory model for head or crab lice exists. Body lice have given all lice a bad reputation, and the stigma from infestations with lice make education in this area difficult. Much of the older lice studies in the literature were conducted in the cold climate of England, which is quite different from climactic conditions in the United States. Body lice, not head or crab lice, were used because they were hardier and can go longer without a blood meal. Pediculosis capitis infestations are in epidemic proportions in some parts of the United States and the world. The development of lice resistant to DDT, lindane, malathion, and permethrin and with a reduced efficacy with natural pyrethrins has resulted in the highest prevalence of head lice in the last 50 years. Parents are spending hundreds of dollars on head lice products that do not meet their purported claims. Some children in Florida have missed more than 2 months of school because of head lice or nits. Parents and even dermatologists are prescribing anything from petroleum gel to olive oil and mayonnaise in an effort to get children back in school. Oral ivermectin is a promising candidate for resistant lice, but future studies will be needed to determine the optimum dosing regimens. Oral ivermectin has been effective even against crusted cases of scabies in patients with acquired immunodeficiency syndrome. In this monograph the diagnosis and treatments for body, head, and crab lice and scabies are discussed, including issues of resistance and treatment in immunocompromised individuals.