It's all very well having animals around as food or for company, but the trouble is that we pick up diseases from them, and those can be deadly, especially in the initial phase after jumping across to our species. At the end of the year in which Ebola hit the headlines for months, I've discussed the wider problem of zoonotic disease and the lessons to be learned from the failure to tackle Ebola in time to stop it running out of control.
Our shared burden of diseases
Current Biology Volume 24, Issue 24, pages R1139–R1141, 15 December 2014 Open access
(I can send PDF "reprints" on request, and the article should become freely accessible one year after publication)