The four clinically important cestodes, or flatworms, are Taenia saginata (beef tapeworm), Taenia solium (pork tapeworm), Diphyllobothrium latum (fish tapeworm), and Hymenolepis nana (dwarf tapeworm). The tapeworms live in the intestine of vertebrates (the primary or definitive host) but spend…
Hookworm disease is caused by either of two nematodes, Necator americanus (New World hookworm) or Ancylostoma duodenale (Old World hookworm). N. americanus is found in the Western Hemisphere in tropical and subtropical areas and also in Africa and Asia. A.…
Strongyloidiasis, caused by the nematode Strongyloides stercoralis ( S. sterocralis, threadworm), is prevalent in Asia, Africa, Oceania, South America, Southern Europe, and southeastern states of the United States (Kentucky, Virginia, Tennessee, and North Carolina). In the United States, the predisposing…
An estimated 807 to 1221 million people in the world are infected with Ascaris lumbricoides, the largest helminth to infect humans. The adult male measures 15 to 25 cm and is smaller than the female, which may be as large as…
Enterobiasis is caused by the pinworm Enterobius vermicularis. This nematode is probably the most common parasite to host on humans because it flourishes in temperate and tropical climates. The small, spindle-shaped, white round adult worms inhabit the cecum and appendix,…
Intestinal helminths are common worldwide, but the most important and common soil transmitted helminthic infections are by Ascaris lumbricoides, Trichuris trichiura, and the two hookworm species Ancylostoma duodenale and Necator americanus. Trichuris trichiura is commonly known as the “whipworm” because…
Giardia lamblia, also called Giardia intestinalis (or G. duodenalis ), is a flagellated intestinal protozoan ( Fig. 116.1 ). In the United States an estimated 1.2 million individuals are reported to develop gastrointestinal symptoms annually because of giardial infection. G.…
Worldwide, amebiasis is caused by Entamoeba histolytica (E. histolytica) and is the third most common parasitic disease, affecting 50 million people and causing 100,000 deaths per year. It is highly prevalent in Central America, South America, Africa, and Asia. In…
Actinomycosis of the abdomen is most often caused by a gram-positive anaerobic bacterium, Actinomyces israelii. However, many other species can cause the same syndrome. Actinomyces as commensals colonize the oral cavity, upper gastrointestinal tract, and female urogenital tract. Abdominal and…
Tuberculosis (TB) is caused by Mycobacterium tuberculosis and historically is one of the oldest known human afflictions. According to the World Health Organization (2013), globally the annual incidence of TB was 8.6 million, and 1.3 million died in 2012. TB…