RT Book, Section A1 Pollack, Richard J. A1 Norton, Scott A. A2 Jameson, J. Larry A2 Fauci, Anthony S. A2 Kasper, Dennis L. A2 Hauser, Stephen L. A2 Longo, Dan L. A2 Loscalzo, Joseph SR Print(0) ID 1156510719 T1 Ectoparasite Infestations and Arthropod Injuries T2 Harrison's Principles of Internal Medicine, 20e YR 2018 FD 2018 PB McGraw-Hill Education PP New York, NY SN 9781259644016 LK accessmedicine.mhmedical.com/content.aspx?aid=1156510719 RD 2021/04/10 AB Ectoparasites include arthropods and creatures from other phyla that infest the skin or hair of animals; the host animals provide them with sustenance and shelter. The ectoparasites may penetrate within or beneath the surface of the host or may attach by mouthparts and specialized claws. These organisms may inflict direct mechanical injury, consume blood or nutrients, induce hypersensitivity reactions, inoculate toxins, transmit pathogens, create openings in the skin for secondary bacterial infection, and incite fear or disgust. Human beings are the sole or obligate hosts for only a few kinds of ectoparasites but serve as facultative, dead-end, or paratenic (accidental) hosts for many others.