Study summary · Dogs and cats · Raw-food safety · van Bree et al., 2018
Contamination findings need a clear denominator.
Testing found several potential pathogens in frozen raw foods. These are food-sample results, not infection rates in pets or people.
Why this study matters
A safety claim can concern the food itself, illness in an animal, or illness in a household. Those questions require different measurements. Knowing which one was studied prevents a contamination percentage from being mistaken for the chance that a pet will become ill.
How the study worked
Samples
35 frozen raw pet foods from eight brands available in Dutch shops. Products were selected by availability, rather than a random sample of the whole market.
What happened?
Laboratory screening for bacteria and parasites.
The comparison
No cooked-food comparison group.
What was measured?
Selected bacteria were examined using culture-based methods; parasite DNA was assessed by PCR. The study did not measure illness in animals or households.
What the researchers found
| Outcome | Reported result | How to read it |
|---|---|---|
| Salmonella | 7/35 samples (20%). | Sample prevalence, not illness risk. |
| Listeria monocytogenes | 19/35 (54%). | Results concern the tested market and products. |
| Resistant E. coli | ESBL-producing E. coli: 28/35 (80%). | A resistance finding does not measure transmission. |
| Other detections | E. coli O157:H7: 8/35; Toxoplasma gondii: 2/35. | Detection alone does not establish clinical infection. |
Source access: full article checked, including sampling, laboratory methods and disclosures.
What strengthens the evidence?
Testing covered multiple products and brands, with organism-specific laboratory methods reported in the full article. Counts and uncertainty intervals help readers judge the limited sample size.
What limits the conclusions?
A small historical convenience sample cannot estimate contamination across today’s entire market. There was no cooked-food comparator. Parasite DNA detection does not establish viability; the identified Sarcocystis species were not zoonotic. Brands were anonymised, preventing attribution to current named products.
What the researchers concluded
The authors identified potential risks from contaminated raw foods.
Evidence.pet interpretation
This study identifies a food-safety hazard in the samples examined. It does not measure the chance of a particular pet or person becoming ill. Bacterial culture and parasite DNA testing support different inferences, so their positive results should not be treated as interchangeable. Neither a category-wide condemnation of every current product nor a claim of zero risk follows from these data. Product and batch testing would be needed for a named-food conclusion.
Funding and author interests
Part-funded by the Eijkman Foundation for Postgraduate Education and Research in Public Health, Utrecht. The authors declared no competing interests.
Read the original research
van Bree FPJ, Bokken GCAM, Mineur R, et al. Zoonotic bacteria and parasites found in raw meat-based diets for cats and dogs. Veterinary Record. 2018;182(2):50. doi:10.1136/vr.104535.
Evidence.pet editorial summary · Study ID STU-005 · Source checked 23 September 2026. Strengths, limitations and interpretation are our editorial assessment, not a formal evidence grade.
Full-text editorial appraisal completed. This is a critical reading of one study, not a systematic review or formal certainty grade.