Infestations

Ectoparasites are the etiologic agents of infestations affecting humans The etiologic agents are lice, scabies, and ticks.

Pediculosis is caused by lice: Pediculus hominis or Phthirius pubis. Body lice may transmit trench fever, relapsing fever, and epidemic typhus.

Scabies is a mite infestation. The causative mite is Sarcoptes scabiei var hominis. A severe form (crusted or Norwegian scabies) may occur in patients with cutaneous lymphomas, immunocompromised or debilitated states.

Ticks are mites with a rigid integument (shell) that feed on the blood of animals. Ticks are ubiquitous. Ticks can transmit spirochetal, viral and rickettsial illnesses.

Diagnosis of infestations can be made by a careful history and physical examination of the patient and the skin lesions as well as the demonstration of the presence of the organisms, their eggs, or feces. Tick transmitted infections need to be confirmed by isolation or demonstration of the organism from tissue biopsies (histologically, by polymerase chain reactions, or by cultures) or expected changes in acute and convalescent serologic studies.