We had overlooked Stevens et al. 2014 in which the same 12S primers were used to successfully amplify opossum DNA.

http://journals.plos.org/plosntds/article?id=10.1371/journal.pntd.0003047

Stevens, L., Monroy, M. C., Rodas, A. G., & Dorn, P. L. (2014). Hunting, swimming, and worshiping: human cultural practices illuminate the blood meal sources of cave dwelling Chagas vectors (Triatoma dimidiata) in Guatemala and Belize. PLoS neglected tropical diseases, 8(9), e3047.