Pet Food Contamination: Aflatoxin, Molds, and Melamine

As a companion to the guest post I wrote on the basics of cat and dog nutrition over on PawDiet, (I promise I’m not abandoning our ABCs, and K will be my next post!), today we’re going to cover the touchy topic of pet food contamination.

If you haven’t had a chance to check out PawDiet, take a peek at the Food Finder and the widgets page.  The ability to find a food based on multiple criteria is essential for picking the right diet for your pet!

What is so scary about packaged pet foods?

Pet Food Contamination

Villainous pet food

This is a question bouncing around in people’s head a lot lately, especially considering the food recall in 2007 and all of the buzz around switching to grain-free or raw-based diets.

There are a lot of factors that influence the quality of a packaged pet food extending past the manufacturer. Ingredients shipped from distributors can become contaminated, storage of foods at the store (and at home) can affect food quality, and there are some toxins that the FDA doesn’t completely regulate. The contaminants we are going to cover today include:

  • Molds such as aflatoxin and tremorgenic mycotoxins
  • Melamine

Jerky treats and bacterial contamination will be covered in a later article.  Currently, the causes of jerky-treat-related death are still being investigated. Bacterial infection is an expansive topic and needs an article of its own! However,  bacterial contamination is a very common type of animal food contamination.

In many cases, pet food contamination may not be directly related to the manufacturer itself, but instead a breakdown in one of many pieces in a chain of events that ends up affecting your animal.

Melamine – what happened in 2007

Melamine pet food contaminaion

A magic eraser made from melamine! 
(No, magic erasers won't kill your pet in the same way)

Melamine is a chemical used in the production of several non-edible products such as plastics and resin.  When added to wheat gluten, melamine can falsely increase the protein content when subjected to laboratory tests.  While not approved for use in any food, some companies will illegally add melamine to wheat gluten in order to falsely bump up the reported protein content of a product.

In 2007, a Chinese plant-product processor, an Chinese food product exporter, and an American food product supply company entered a contract that ended up with 800 tons of melamine-contaminated wheat gluten to be imported to the US and sold to pet food companies. When a pet food manufacturer reported several linked illnesses and deaths in the pet community, the supply companies were all brought up on federal charges.

FDA’s response was to develop an initiative called PETNet, which is a web-based network that allows for quick reporting and communication regarding illness outbreaks and pet food contamination between federal and state levels, previously a process that did not have good standards of communication.

While melamine has a wider margin of safety (meaning that a larger amount of melamine has to be ingested all at one time before we start to see toxic effects), the buildup of melamine in small amounts over a long period of time (called a chronic exposure) causes the formation of crystals in the kidneys in both animals and humans.

The crystals lead to urinary problems, kidney stones, and eventually kidney failure.  Before everyone who has had an animal in kidney failure runs to report their pet food, this type of pet food contamination is not very common.  Due to increased regulation of food products on part of the FDA and increased awareness of melamine in the food industry, the risk of this happening is very low.  It is still a good idea to keep up-to-date on current pet product recalls through the FDA.

Aflatoxin and other molds

Pet food contamination: aflatoxin

Aflatoxin is a toxic byproduct produced by certain species of Aspergillus fungi (aka, a mold).  While many molds tend to be tremorgenic  (meaning they cause tremors and seizures), aflatoxin directly affects the liver.

These species of molds thrive in warm weather and moist grain conditions.  They are common enough in grain storage that the FDA has reported “acceptable” levels of aflatoxin in food-based products.  As you can see, the “acceptable” levels for certain things (corn here being the key) are HIGHER for food planned for animal consumption than for food planned for human consumption.

It is not a well-kept secret that pet food companies often invest in cheaper ingredients for their pet foods, and food that has NOT passed the qualification for human consumption may be sold to a pet food manufacturer for animal consumption.  While the current claim is that these levels of aflatoxin in pet food are not high enough to risk the health of the animal, there is not a lot of documentation on the long-term effects of chronic exposure in pets.

Acute exposure tends to occur when improper storage leads to an acute contamination that slips through the cracks of the food control process (again not a common occurrence)

Signs related to aflatoxicosis start with tummy upset and progress:

  • Vomiting
  • Diarrhea
  • Unwillingness to eat
  • Dark, tarry stools from digested blood (melena)
  • Stomach pain
  • Bloody diarrhea
  • The buildup of fluid in the stomach (abdominal effusion)
  • Increases in thirst and urination
  • Dehydration and other electrolyte imbalances
  • Increases in liver enzymes, liver damage, and liver failure
  • Coagulopathy (excess bleeding)
  • Brain damage or malfunction
  • Death

As these signs are common among all toxins that cause damage to the liver, it can be very difficult to tie an affected animal to a contaminated food source.  If at any point you suspect that your pet may have been exposed to a contaminated food and died as a result, insist upon a necropsy and have samples kept of both your pet’s liver, the contents of your pet’s stomach, and bag up several samples of the food at home for laboratory testing (use gloves!).  Then report everything to the FDA. 

Alternative to testing through the FDA (which they may or may not offer), you can have your vet send the samples of to a diagnostic testing lab for analysis.


There is no antidote for aflatoxin.  Animals are treated supportively to help protect the liver and alleviate signs:

  • IV fluids to support hydration
  • Vitamin K supplements to prevent coagulopathy
  • Drugs to replace loss of antioxidants and prevent vomiting
  • Liver protectants

As is often the case,  with sudden-onset liver failure, these cases can be difficult to treat, and may end up being fatal.

Tremorgenic mycotoxins cause vastly different signs


While aflatoxin occurs most often due to poor storage at the level of production and distribution, other molds can occur after a product has been purchased. Food at home that has been improperly stored may grow mold, leading to toxic

osis (shout-out to Doctor Schell who authored this tox brief.  She is one heck of a fun person and has led an interesting life). This is not limited to purchased pet foods, but is something that can also affect animals who ingest trash, compost, or human food that is past expiration.

Signs of ingestion include:

  • Vomiting
  • Stumbling
  • Changes in heart rhythm and rate
  • Twitching
  • Tremors
  • Seizures
  • Death

Depending on how alert you are to the fact that your dog has ingested a moldy substance, treatments can vary:

As opposed to aflatoxin, dogs who ingest mycotoxins do well if they receive treatment in time.  Veterinary care is required, so keep the number to animal poison control handy, or notify your local or emergency vet if you suspect an exposure.

Prevent pet food contamination

As always, prevention is key to keeping your pet healthy. There are several changes you can make at home to help reduce the likelihood of your pet being exposed to spoiled or moldy foods:

  • Always check the expiration date on foods you feed to your pets.
  • Never feed anything that smells “off” or “funny”.
  • Store dry food in an air-tight plastic container with a lid.
    • Write the food’s expiration date on a piece of masking tape and tape it to the top of the lid.  Disposed of any expired food.
  • Cap and date opened cans of unused wet food.  Store them in the fridge, and toss them after 2-3 days.
  • Toss all cans of expired, unopened pet food.
  • Don’t keep food in the garage, or outside.
  • Invest in a  trash can with a lock, or get a lid-lock.
  • Throw away spoiled or moldy food in the outside trash can, and do not keep bags with moldy food inside.

Happy eating!

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50 Comments on "Pet Food Contamination: Aflatoxin, Molds, and Melamine"

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Great, usable information – I really appreciate this article! You’ve delivered educational content that all pet parents should read!


Good info. Thanks for sharing!

Lauren Miller

Great post! This is so important! We go through our pet food regularly and make sure it’s not outdated. I also carefully check it before feeding, too!

Michelle & The Paw Pack

Really useful information! I was familiar with the dangers of aflatoxins but learned some new stuff about melamine for sure. Thanks for sharing.

Tenacious Little Terrier

We have to buy such small bags the food doesn’t usually have a chance to go bad. Big bags would be more cost efficient but it would spoil before we could use it all.

Pawesome Cats

Interesting post – thanks! The quality and contamination risk with commercial foods is one reason why we feed our cats a raw diet – prepared at home and adhering to strict hygiene standards.

Andy's Paw Prints

Everyone should read this!

Val Silver

Yuck, pretty scary stuff. Ted’s little, so I buy smaller bags and store food in a plastic container.

Fur Everywhere

It’s really scary how pet food can be contaminated. I try to feed my kitties high-quality food, but even that can be contaminated. We all have to be aware of the recalls and be mindful of what we’re feeding our babies.

M. K. Clinton

Pet food contamination happens way more often than people think. Great post with excellent information!

Three Chatty Cats

What great information you have provided here! I will be bookmarking this so I can refer to it again later. Thank you!

Talent Hounds

Great information. I worked on water purification for a while a few years ago and so scary what can contaminate food and water. Those toxins can be so bad for dogs.


Thanks for sharing this information. There’s so much to know and it’s so important to be vigilant!


I’m still angry over the melamine issue and don’t think the companies faced fair repercussions. However, there are so many smaller companies making pet food now – using human grade ingredients and in Canada at human-grade (and inspected) manufacturing plants, which makes me a little more confident. The food industry here is heavily regulated and meeting human food plant level inspections (voluntarily) is good PR.


I’m still angry over the melamine issue and don’t think the companies faced fair repercussions. However, there are so many smaller companies making pet food now – using human grade ingredients and in Canada at human-grade (and inspected) manufacturing plants, which makes me a little more confident. The food industry here is heavily regulated and meeting human food plant level inspections (voluntarily) is good PR.

Cathy Armato

The pet food recalls have gotten more and more frequent the last couple of years, it’s so scary. Thanks for this info and the tips on food storage to keep pet food safer.
Love & Biscuits,
Dogs Luv Us and We Luv Them


I learned about this when studying nutrition – and I think it’s great you’re creating awareness for these molds (and defining aflatoxin and tremorgenic mycotoxins). Great post!

Jessica Gibson

Ahh this stuff is so scary! But this is very useful information. Thanks for sharing.


Such important information. I’ll be sharing for sure. Thank you! And thanks for joining our Blog Hop today, too!


Wow! Very interesting – and in need of sharing. Thank you for this information.

Sweet Purrfections

Very information and very scary!

Lindsay Pevny

I’d hate to lose my dog this way – thanks for sharing this info!


Wow this is very informative and useful! Thanks for sharing 🙂

Spencer the

Wonderful and informative post! Thanks you for sharing!!!


Pet food companies can be so dishonest sometimes! It is very troublesome that they get away with putting these types of things in pet foods until enough animals die that the public is outraged. I hope that in the future we will see improvements in the regulation of pet food. There doesn’t necessarily need to be more rules, there just has to be effective rules that are well enforced.

Susan and the gang from Life with Dogs and Cats

Great advice! I check and double check anything I feed my dogs and cats.
—Wags (and purrs) from Life with Dogs and Cats


[…] Now that we know what a good food for a dog or a cat looks like and can pick it up on the shelves, we’re ready to delve into the real concern, which are the standards set out by the FDA, and what can end up in your bag of cat food. Let’s talk about the risk of toxic exposure in pet food. […]