Thanks @el502,
That's interesting. The fact that there are a lot of host DNA contaminants in this one particular study makes me think perhaps there was something subpar with their DNA extraction/amplification process. Maybe it was just a super low biomass sample and their primer picked up a lot more human targets.
What is the tissue type being analyzed in this case? I've seen similar issues with mouse intestinal issues when really strong bead-beating steps are utilized.