View photos of the medicinal plant Cupressus arizonica (Arizona cypress), profiled in Medicinal Plants of the American Southwest.

A passage from  Medicinal Plants of the American Southwest:

Cypress’s aromatics are inhibiting to Giardia lamblia and the ameba group of organisms, particularly Entamoeba histolytica. The tea or tincture can be used alone, or more successfully with Castela emoryi or Ailanthus altissima.