Scabies, an infection by the itch or scabies mite, Sarcoptes scabiei var. hominis, remains a major public health problem throughout the developing world ( Fig. 293.1 ). Scabies in its most severe form, crusted or Norwegian scabies ( Fig. 293.2…
Pediculosis is a complex of three different human infestations with two species of blood-sucking lice of the insect order Phthiraptera, suborder Anoplura: Pediculus humanus and Phthirus pubis. Sometime after early humans began to wear clothes, P. humanus evolved into two…
Ectoparasites infest the skin and its appendages, such as the hair and sebaceous glands, and most external orifices, especially the ears, nares, and orbits. Like endoparasites, ectoparasites may be obligatory parasites, programmed to feed on human hosts to complete their…
Most helminths that infect humans are relatively host specific to humans, undergo characteristic migration and development, and are found in typical anatomic locations. However, these helminths sometimes undergo atypical or aborted migrations and cause symptoms or signs because of their…
In humans, parasitic cestode infections occur in either of two forms: as mature tapeworms residing in the gastrointestinal tract or as one or more larval cysts (variously called hydatidosis, cysticercosis, coenurosis, or sparganosis) embedded in liver, lung, muscle, brain, eye,…
The trematode flatworms that infect humans include the schistosomes, which live in venules of the gastrointestinal (GI) or genitourinary tract, and other flukes, which inhabit the bile ducts, intestines, or lungs. The geographic distribution of each species of trematode parallels…
Tissue-dwelling nematode (roundworm) infections are widely distributed throughout the world. The health and socioeconomic impacts of these infections are greatest in resource-poor settings in the tropics and subtropics, although populations in temperate and industrialized regions of the world continue to…
Intestinal Nematodes More than 1 billion people are infected with intestinal nematodes worldwide. Also referred to as soil-transmitted helminths (STHs), intestinal nematodes are complex, nonsegmented, multicellular worms. Each organism is surrounded by a species-specific acellular cuticle composed of structural proteins,…
The helminthiases are among the most prevalent infections in the world and a leading cause of morbidity, particularly in low-income and resource-constrained regions. An estimated 1.5 billion persons harbor at least one species of parasitic worm. The helminths that parasitize…
During the past several decades, the association of human health and environmental problems with harmful and toxic algae has been increasingly recognized, as has awareness of the complex range of natural toxins (and toxin congeners) that can be produced by…