1. Life cycle of Trichinella spiralis (trichina worm)
Life cycle of Trichinella spiralis (trichina worm). Pigs become infected from eating uncooked garbage containing raw infected meat or occasionally from eating infected rats. Humans most commonly acquire the infection from undercooked pork. Polar bears often are infected from seal prey, and the seals presumably from infected carrion. Many such predator-prey cycles can account for transmission of this nonspecific nematode. Symptoms of infection (orbital and other sites of edema, muscle pain, eosinophilia) occur during the period of invasion of muscle tissue, 2–6 weeks after human ingestion of contaminated meat. 1–4: Larvae digested from cysts (1) enter the mucosa, develop to adults in 3–4 days, and then return to the lumen and mate. The fertile females return to the mucosa and pass motile embryos (2) that enter the bloodstream and migrate to tissues. A larva leaves its blood vessel and enters a muscle fiber, which it modifies to a "nurse cell" (3). A few days later, it encysts within the modified muscle cell (4). (Reproduced, with permission, from Goldsmith R, Heyneman D [editors]. Tropical Medicine and Parasitology. Originally published by Appleton & Lange. Copyright © 1989 by The McGraw-Hill Companies, Inc.)
Source: Protozoal & Helminthic Infections, Current Medical Diagnosis & Treatment 2017
Citation: Papadakis MA, McPhee SJ, Rabow MW. Current Medical Diagnosis & Treatment 2017; 2016 Available at: Accessed: October 20, 2017
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