Life Cycle
The life cycle of T. suis is direct and does not require any intermediate host. Eggs are passed in feces from infected animals, but are single-celled and are not initially infectious. Infective J1 stage larvae develop within the shell in 3 weeks to 2 months, depending on environmental temperature. The infective J1 stage within the egg is highly resistant and can remain in this form for several years in favorable conditions. Once the infective J1 egg is ingested, the bipolar plugs are digested and the J1 larvae hatch in the small intestine and cecum. The J1 larvae penetrate the mucosa via the crypts of Lieberkühn in the distal ileum, cecum, and colon. During the next 5 weeks, the larvae undergo four molts (J2, J3, J4) to the adult stage (J5) within the mucosal layers. The adult’s thicker posterior one-third then emerges through the mucosal surface into the lumen while the thin anterior two-thirds remains embedded in the mucosal layers. Adults can be recovered anywhere from the distal ileum to the rectum, but most are located in the cecum and proximal colon. The prepatent period is 6 to 8 weeks and life span is 4 to 5 months.
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