– infection from agent that is already in body, infection keeps circulating inside body

            Example: Cyrptosporidium infections will continue to circulate with lack of immune response

inside membrane but outside cytoplasm (remains in parasitophorous vacuole, lives in membrane)

            Example: cryptosporidium stays in membrane when infecting cell

hospital settings

            Example: Groups in hospitals are more at risk for crypto

small amount of constant re-exposure helps keep immunity

            Example: Residents of San Juan de Miraflores develop immunity to C.hominis by constant small re-exposure

programmed cell death

            Example: crypto sends out anti-apoptotic signals to prevent intestinal cells from dying so that the parasite can complete life cycle

lymphtocytes in epithelial layer of mucosal lining

Example: crypto lives in membrane of host cell but not cytoplasm (intracellular but extracytoplasmic)

Thin-walled and thick-walled oocyst

Zygotes form into oocysts

- 80% thick wall: survive well in environment to infect new host

- 20% thin wall: create new route of reinfection in same host

Example: Cryptosporidium zygotes form into two different oocysts, 80% thick wall hardy survival in environment to infect new host, 20% thin wall to find new routes of reinfection in same host to continue autoinfection

oral therapy

Example: oral antibody solutions to cut down on crypto reinfection

vaccination to stimulate immune response

Example: no vaccine for crytpo