A study published in Veterinary Record reports that a large proportion of frozen raw meat-based diets sampled in the Netherlands contained pathogenic bacteria or parasites, including E. coli, Listeria, Salmonella, Sarcocystis, and Toxoplasma.

More details on the study of contamination of raw pet diets can be read in the Guardian. The original study is available in the Veterinary Record. 

More information on risks associated with raw pet diets is also available in the MSD Veterinary Manual.