Just because it looks like science doesn’t mean it is

by Nicole Cammack
April 23, 2020

AVMA says, “Study: Raw dog food often contains drug-resistant bacteria”

On April 21, 2020, the AVMA emailed a link to an original article published on April 20, 2020, by the Center for Infectious Disease Research and Policy (CIDRAP) examining the presence of multidrug-resistant (MDR) pathogens within raw meat-based diets (RMBD). Within this article, the CIDRAP cites three separate studies, all of which are abstracts – not peer-reviewed papers. Two of which actually have no direct link to the feeding of RMBDs and pathogens. Like many other articles both peer-reviewed and opinion pieces, this article preys upon the fears of pet owners and the public by claiming potential for pathogen transmission from RMBDs to humans or pets who consume RMBDs to humans. Unfortunately, CIDRAP and AVMA fail to put the entire situation into perspective, which I’ll discuss later on.

The AVMA introduces the CIDRAP article with a short paragraph, clearly showing the AVMA did not validate the sources within the article, before sending it to the veterinary community. This is unfortunate considering so many within the veterinary community hold this organization in high regard and trust them to promote and distribute true science-based literature to be used within the practice of veterinary medicine. However, as evidenced multiple times in the recent past this is just par for the course, (grain-free pet foods and DCM sound familiar?). 

Let’s take a look at the CIDRAP article:

If we examine the CIDRAP article we’ll find links to 3 abstracts that they use to create the perception that RMBDs post a significant public health risk. The problem with this assumption or theory is that data is lacking to support this concern, despite their ‘references’. In fact, the perception among the general public is that all pathogens are bad, which is factually incorrect since many are beneficial. For example, the Centers for Disease Control (CDC) references more than 2,500 serotypes have been described for Salmonella; but, less than 100 serotypes account for most human infections. In addition, it is well known that companion animals may harbor pathogenic bacteria, as a part of their healthy gut flora without any signs of illness.

Studies Cited by AVMA & CIDRAP

Study 1: It is entirely focused on commercially available dry, canned, and raw foods available and purchased from various outlets within Portugal. This is not a sample that can be compared to the U.S., because we have different supply chains, manufacturing processes, and standards for our commercial RMBDs.  Commercial RMBDs within the U.S. have additional steps that reduce the risks of pathogen contamination, within the manufacturing and distribution processes, such as high-pressure pasteurization.  The authors state the following: 9 out of 9 of raw samples contained an MDR pathogen, while 8 out of 15 dry samples contained an MDR pathogen, and 2 out of 22 canned/wet samples contained an MDR pathogen. 

Limitations & flaws of study 1: The authors draw the conclusion that close contact between pets and humans fed raw are a public health risk if transmission of MDR strains occurs between dogs and humans. This conclusion is a glaring problem considering the authors did not study the transmission of bacteria from dogs to humans. In addition, the authors focused on the MDR pathogens within the raw samples and did not fully study the dry and wet samples per their results – even though they clearly carry the same MDR pathogens. Further, both the CIDRAP article and the AVMA completely ignore the fact that these foods are isolated to Portugal, and that the same MDR pathogens also occur in dry and wet food varieties. This likely indicates significant agricultural and meat distribution problems within Portugal.

Absent from the discussion is the potential for the MDR pathogen prevalence to be originating from poor quality meat suppliers, or as a result of mishandling in the distribution and storage processes – which are all potential confounding variables.  More research into RMBDs, within different geographic regions, is necessary for a comparative measure, as well as a closer look into different methods, used in mitigating pathogen presence in RMBDs – just as high-pressure pasteurization, and other “kill step” methods which are widely used in the U.S.

Study 2: Again, isolated to Portugal, the authors investigate the occurrence of colistin resistance genes, in both human and companion animal feces. Ultimately, researchers did find the presence of mcr-1 (mobilized colistin resistance) gene in 1 dog and 2 healthy humans, which is quite rare. Mcr genes confer plasmid-mediated resistance to colistin, one of a number of last-resort antibiotics for treating Gram-negative infections. 

Limitations & flaws of study 2: This study did not call out diet, as one of the variables, focused on for this research, meaning that it is likely that both cats and dogs were eating a variety of foods including dry, wet, and RMBDs. Therefore, this study should not have been used by CIDRAP or the AVMA in an attempt to substantiate their claim. It would have been nice to know the results of this study, based on the diet of the companion animal in the household. The prevalence of this gene is significant but is unlikely associated solely with the practice of feeding RMBDs to companion animals. Rather, the prevalence of this gene in humans and pets is likely multifactorial and complex. 

Study 3: This study is still in progress and is assessing the relevance of companion animal husbandry, in the colonization of MDR organisms of hospital patients. The authors examined a group of 1,500 humans, of which 495 (33%) tested positive for MDR organisms. In total, 296 (20%) participants owned at least 1 pet. There was no significant difference in the prevalence of MDR organisms, in the pet-owning and non-pet owning groups.

Limitations & flaws of study 3: This study was not related to RMBDs. The authors are looking for a much larger sample size, so it is not yet complete. Meaning, we must take into consideration the results above may not be representative of the final results. Much like study 2, the authors do not state that the companion animal diet was a variable that was considered, and it would be nice to know how diet potentially could play a role within the animal-owner group. 

Overall, preliminary conclusions from this study show that animal ownership does not play a significant factor, in MDR organism colonization in hospitalized human patients. 

Counting on Blind Trust or Ignorance?

So did the AVMA actually fail to validate its sources? Or do they know these studies are poor references and hope their readership (aka the veterinary community) do not do their homework? It’s likely AVMA is likely counting on two things:

  1. The majority of veterinarians either don’t have time to do their homework to verify the source and/or that they will trust that the information that AVMA is distributing is rooted, in sound science and that it does not need to be challenged.
  2. The pet-owning public will either see this information in print or hear of it from their veterinarian and accept it as fact, rather than ask questions to obtain the whole picture or challenge the data – or in this case, lack thereof. 

Regardless, this is yet another example of the scientific and veterinary medical communities needing to hold each other accountable. Failing to fact check or bending facts to fit an agenda is not only poor science, but it is also a disservice to the academic community and the animals that rely on their owners receiving factual and complete information from their veterinarian, in order to make decisions on care. Providing only part of the story to the owner or veterinarian simply is unacceptable considering treatment decisions are based on such information.

As pet owners, and professionals in the industry we need to demand better. This entire situation highlights the necessity for pet owners to do their homework, in verifying sources. It is more important now than ever to read, ask questions, and challenge available data and opinions. The status quo obviously isn’t working, and until we start holding each other accountable we won’t see the change we so desperately need.

*This article is for informational purposes only. It is not meant to provide medical advice or replace the advice of a qualified veterinarian.