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Harrison's Principles of Internal Medicine, 18e
| Part 8. Infectious Diseases > Section 19. Helminthic Infections > |
Chapter 218. Filarial and Related Infections
Sections: Filarial and Related Infections: Introduction, Lymphatic Filariasis, Tropical Pulmonary Eosinophilia, Onchocerciasis, Loiasis, Streptocerciasis, Mansonella Perstans Infection, Mansonella Ozzardi Infection, Dracunculiasis (Guinea Worm Infection), Zoonotic Filarial Infections, Further Readings.
Topics Discussed: filariasis; parasitic diseases; parasitology.
Excerpt:"Filarial worms are nematodes that dwell in the subcutaneous tissues and the lymphatics. Eight filarial species infect humans (Table 218-1); of these, four—Wuchereria bancrofti, Brugia malayi, Onchocerca volvulus, and Loa loa—are responsible for most serious filarial infections. Filarial parasites, which infect an estimated 170 million persons worldwide, are transmitted by specific species of mosquitoes or other arthropods and have a complex life cycle, including infective larval stages carried by insects and adult worms that reside in either lymphatic or subcutaneous tissues of humans. The offspring of adults are microfilariae, which, depending on their species, are 200–250  m long and 5–7 m wide, may or may not be enveloped in a loose sheath, and either circulate in the blood or migrate through the skin (Table 218-1). To complete the life cycle, microfilariae are ingested by the arthropod vector and develop over 1–2 weeks into new infective larvae. Adult worms live for many years, whereas microfilariae survive for 3–36 months. The Rickettsia-like endosymbiont Wolbachia has been found intracellularly in all stages..."
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