Disclosed are methods, compounds, and compositions for treating infection by an Apicomplexan parasite that include administering a compound that selectively inactivates ornithine aminotransferase of the Apicomplexan parasite. Specifically, the methods, compounds, compounds may be utilized for treating infection by Toxoplasma gondii and toxoplasmosis and for treating infection by Plasmodium falciparum and malaria. The compounds disclosed herein are observed to selectively inactivate Toxoplasma gondii ornithine aminotransferase (TgOAT) relative to human OAT and relative to human γ-aminobutyric aminotransferase (GABA-AT).