Do pathogens in animal products cause deadlier illnesses?

Millions get sick, tens of thousands are hospitalized and over a thousand die each year from food-borne illnesses acquired in the United States. The government agencies involved in monitoring or regulating matters related to food safety usually give us the useful but humdrum advice that we should cook meats at high enough temperatures, wash our produce well, or use separate cutting boards for different categories of foods. There isn't any official advice available if we want to make a decision on which foods to avoid in order to reduce our overall risk from pathogens. It would be useful to have answers to two questions: (i) consumption of which category of foods is most likely to lead to an illness? (ii) which categories of foods contain pathogens that cause the deadliest illnesses? This post offers data to help answer the second question.

Sources cited
  1. M. B. Batz, S. Hoffmann and J. G. Morris, Jr. Ranking the Risks: The 10 Pathogen-Food Combinations with the Greatest Burden on Public Health. University of Florida, Emerging Pathogens Institute, April 2011. (link, accessed January 1, 2013)
  2. E. Scallan et al. (Centers for Disease Control and Prevention). Foodborne Illness Acquired in the United States—Major Pathogens. Emerging Infectious Diseases 17(1), January 2011. (link, accessed January 1, 2013)

Even though statistics on illnesses caused by various food-borne pathogens are widely available, very little data is available on which food-pathogen combinations cause these illnesses. This is because it is easier to know if a patient has a Salmonella infection but harder to trace back and isolate the food consumed by the patient that caused the infection. Thankfully for us, the Emerging Pathogens Institute (EPI) of the University of Florida has done the hard work and produced a report estimating the annual number of illnesses, hospitalizations and deaths attributable to each category of food. I used their data (which considers the top 14 pathogens), combined it with the estimates by the Centers for Disease Control and Prevention (CDC) on the total number of illnesses, hospitalizations and deaths (which considers a more comprehensive set of 31 pathogens) to determine the percentage attributable to each food category. The following pie-charts summarize these attributions with my own categorization of vegan, vegetarian and non-vegetarian foods. The multi-ingredient category includes foods such as baked goods, sandwiches, pasta, salads and dressings, where a specific contaminated unprocessed ingredient was not identified (some of which may even be because there was cross-contamination with other foods due to mistakes during handling, preparation and cooking.)

Raw data sources: EPI, CDC
Percentage of ILLNESSES
attributable to food category
Percentage of HOSPITALIZATIONS
attributable to food category
Percentage of DEATHS
attributable to food category

It is no surprise that the majority of hospitalizations and the vast majority of deaths from food-borne pathogens are directly attributable to the consumption of animal ingredients. But, there is something else that jumps out at us when we look at these three pie charts together: what is attributable to animal ingredients is larger in the second pie chart than in the first and even larger in the third. For example, only 44% of illnesses are attributable to animal ingredients but 58% of hospitalizations and an amazing 72% of deaths are attributable to animal ingredients. Could it be that there is something nastier about pathogens in animal ingredients than in vegan ingredients? In the following bar graphs, I examine this question more closely for vegan and farmed animal product categories. The bar graphs compare the rates of hospitalizations and deaths for those with illnesses attributable to each food category.

Number of HOSPITALIZATIONS per hundred thousand illnesses
attributable to food category (sources: EPI, CDC)
Number of DEATHS per hundred thousand illnesses
attributable to food category (sources: EPI, CDC)

I had no idea before I plotted these graphs that illnesses attributable to eggs or dairy are among the ones most likely to lead to hospitalization. I did not know that pork and deli meats are among the ones that cause the deadliest illnesses. There are many implications that one can draw from this data for both public health and animal advocacy. What implications do you see?

Comments

Mick

That's it. You have one of the coolest blogs on the internet. I'm printing your posts and distributing them at a huge family gathering this weekend. Please don't stop blogging!

Harish

Thank you, Mick!

Susanna

I was wondering how come eggs were so high on the list, but after having watched "food inc" and how the poultry actually live I'm not surprised at what it says in the article.
• Salmonella is the leading disease-causing bug overall, causing more than $3 billion in disease burden annually. In addition to poultry, Salmonella-contaminated produce, eggs etc...
But - if you cook the egg hard the bacteria should die, so I think the problem is soft-boiled eggs and fried eggs with soft yolk for example.
I always eat completely fried or boiled eggs - just because I dont like it soft - Maybe I'll be safer from the "egg threat" in the US because of that.

Spike

The threat is not only from the eggs you eat, but the conditions poultry are raised in also contribute to the evolution of antibiotic resistant bugs.

Lara

After doing further research on this topic, I discovered that chickens with a diet consistent with that of pure and simple grazing have a far lower likelihood to produce eggs and meat that are contaminated. However, how they're butchered and/or handled makes a difference as well.

If you're a consumer of meat/dairy/eggs, your best bet to stay as clean as possible is to find a local farm that strictly grass (or pasture) feeds their animals with NO "vegetarian" diets (read: corn fed which could be genetically modified), and confirm that their butchering/handling practices are sanitary. Go visit the farm too if you're able. Farmers who are open about their practices will actually welcome it.

Jack Norris

Now I can't drink vegan beverages any longer - it will be only produce for me. I keep telling Vic to be wary of those green smoothies...

I'm kidding - thanks for another very interesting post, Harish!

JD Mumma

Thanks!
I am wondering...
1) If the pathogens that vegans eat where due to fecal matter contamination - which would be a result of a meat based diet society.
2) Based on the small percentage of the vegan population (I'm guessing in the range of 2-5% in the U.S.), would this data translate to meaning a rather high percentage vegans have become ill, hospitalized and/or died?

Alex

Mumma: "2) Based on the small percentage of the vegan population (I'm guessing in the range of 2-5% in the U.S.), would this data translate to meaning a rather high percentage vegans have become ill, hospitalized and/or died?"

That doesn't follow since everyone eats vegan food and drinks beverages, not just vegans.

bp

I thought seafood would be higher.

Jon

Interesting article, as always, Harish!

Guy Grayson

Purhaps the animals dying wishes are coming true-"God please take some of these supermarket sociopaths with me"!
Thanks Harish, the revolutionary mathematician for another profound article.

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