The flukes, or trematodes, are long-lived parasites that can cause human disease by mechanical obstruction and by inciting local inflammatory responses in affected organs ( Table 48.1 ). Blood flukes ( Schistosoma spp.), hepatobiliary flukes ( Clonorchis sinensis , Opisthorchis…
Filarial worms are nematodes or roundworms that dwell in the subcutaneous tissues and the lymphatics. Although eight filarial species commonly infect humans, four are responsible for most of the pathology associated with these infections. These are (1) Brugia malayi ,…
Infections by cestodes (tapeworms, or flat, segmented worms) in the United States, Canada, and other affluent countries are rare but do occur in specific at-risk populations related to geographic, behavioral, or migration risk characteristics. Clinical suspicion is needed to detect…
General Considerations Medically important worms belonging to the phylum Nematoda (roundworms) parasitize the gastrointestinal tract of humans. It is estimated that 60% of the world population is infected with at least one intestinal helminth. The worms are commonly acquired through…
A genital ulcer is defined as a discrete mucosal or cutaneous discontinuity involving the genitals, perineum, or surrounding tissues. Genital ulcer disease (GUD) is an important risk factor for sexual acquisition and transmission of human immunodeficiency virus (HIV), and serious…
Syphilis results from infection with the spirochete Treponema pallidum . Transmission of syphilis occurs most often through sexual contact. Mother-to-infant transmission also occurs, and infection via blood transfusion is possible. Although T. pallidum induces strong humoral and cell-mediated immune responses,…
Infections caused by Neisseria gonorrhoeae and Chlamydia trachomatis are the most common of the bacterial sexually transmitted infections (STIs). Since 1995, genital chlamydial infections have been the most frequently reported bacterial infection in the United States; for gonorrhea, continued emergence…
Because sexually transmitted infections (STIs) are defined by their transmission from one person to another during sex, travel—with its attendant opportunities for new contacts—can facilitate the transmission of STIs in several ways. The number of international travelers has increased steadily…
Leprosy, also known as Hansen's disease, is a chronic infectious disease predominantly affecting skin and nerves. The nerve damage occurring in leprosy may result in deformity, disability, and social stigma, creating problems for patients and their families. The interaction between…
The leishmaniases are a group of chronic cutaneous, mucocutaneous, and visceral diseases caused by infection with one of several species of the protozoan parasite Leishmania . Members of the genus Leishmania are obligate intracellular parasitic protozoa in the family Trypanosomatidae.…