Stercorarian pattern: Trypomastigote forms circulate within the blood of a vertebrate host. They are extracellular parasites. A blood-feeding vector such as a bed bug ingests trypomastigote along with its blood meal. Trypomastigotes transform into epimastigotes within the midgut After about 1 week they transform into metacyclic trypomastigotes. When the host feeds, it often defecates at the same time, releasing metacyclic trypanosomes that contaminate the wound. Within the vertebrate the trypomastigotes are phagocytosed by host defense cells or they may enter other cells such as cardiac muscle. During this intracellular phase of existence they transform into amastigotes and multiple by fission. Large numbers of amasitgotes accumulate and form pseudocysts. Eventually the amastigotes transform into trypomastigotes, rupture the host cell, and enter the circulation. They may be ingested by a vector or infect a new host cell, again becoming amastigotes and repeating the cycle" (University of Alberta).