<ol> <li>To standardize the virulence of doses of Cryptosporidium parvum used in this and subsequent studies.
<li>To investigate the suitability of the Brown-Norway rat as a model for Cryptosporidium parvum infectivity in humans or the C57Bl/6 mouse chemically suppressed with dexamethasone if BN is unsuitable.
<li>To compare Cryptosporidium parvum infectivity for model animals with age andpegnancy which may influence immunocompetence.
<li>To compare Cryptosporidium parvum infectivity for model animals with chemical immunosuppression other than by dexamethasone.
<li>To compare Cryptosporidium parvum infectivity in animals with immunosupression models similar to the effects of AIDS.
<li>To compare Cryptosporidium parvum infectivity in animals with physiological stress and nutritional immunosupresssion models.
<li>To use these data in pathogen virulence and host susceptibility in a model for the transmission dynamics of Cryptosporidium parvum in human outbreaks.</ol>
FY 2000 Accomplishments: <ol><li>Prepared a protocol to develop information for use in risk assessment models of microbial pathogens.
<li>Worked with models of pathogen secondary transmission.</ol>
FY 2001 Plans: <ol><li>Present interim results to EPA.
<li>Work on model.
<li>Start animal work.</ol></p>