There are statistics and studies that address these concerns.  There is a recent study that was completed on the spread of disease that was previously attributed to felines. The results of study attributed the spread of this disease by opportunistic feeding birds (seagulls) and the discharge of sewage (lacking a secondary treatment).  (Interesting that both of these conditions exist in our local community).  The geography where this study was completed provide an excellent control since it lacked the presence of felines and felids.  Perhaps there may be an opportunity to have a public forum to rationally discussed the aforementioned concerns.