Last month, two leading pet-food manufacturers were forced to recall large batches of their dry food products from stores and distribution outlets throughout the US after a number were discovered to have unacceptably high levels of mycotoxins, the toxic and potentially carcinogenic byproducts of mould.
Cargill Animal Nutrition announced that it was voluntarily recalling batches of seven products of River Run and Marksman, already distributed in 15 states, while Procter & Gamble announced the recall of a single production run of Iams ProActive Health Smart Puppy Dry Dog Food. Last summer, Merrick Pet Care recalled a run of its Doggie Wishbone product, 248 cases of which had already been shipped to 10 distributors, because of “the potential” of being contaminated with Salmonella.
These and other recent cases highlight the relatively high risk of contamination of commercially processed pet foods with one or more deadly mycotoxins. In 1997, a study of 100 varieties of dry pet and bird foods revealed a “low level” of the deadliest type of aflatoxin in a sample of cat food. There was also ochratoxin A in 10 per cent of all samples of animal food, and fumonisins in 30 per cent of the samples tested (Food Addit Contam, 1997; 14: 175-86).
Five types or groups of mycotoxins are quite often found in food for humans and animals: deoxynivalenol/nivalenol; zearalenone; ochratoxin; fumon-isins; and aflatoxins. The most common form are the latter, produced by the Aspergillus species of fungi, and aflatoxin B1, the type found in the cat-food sample in the above study, is a potential carcinogen linked to liver disease, including liver cancer. Aflatoxin curtails the production of cholesterol and many of the proteins that profoundly affect blood-clotting, and leads to pathological changes in the liver. Severely affected dogs suffer from intractable vomiting and internal bleeding. In most instances, once a pet has been poisoned with the mould, there is no antidote; two-thirds of dogs with mycotoxic food poisoning die.
Ochratoxin A, produced by the Penicillium and Aspergillus species of mould, has also been linked to tumours of the urinary tract in humans, and fumonisins, made by the Fusarium mould that mainly infects wheat and maize grains, have been linked to cancer in a variety of rodents and to nervous-system disorders in horses.
Pet food has also been shown to contain trichothecenes, also from Fusarium, which are associated with potentially fatal toxic reactions in both animals and humans (Int J Food Microbiol, 2007; 119: 95-102).
More recent reviews of the evidence to date on mould in pet foods disclosed that the chronic presence of aflatoxins, ochratoxin A and Fusarium mycotoxins have caused several food-poisoning outbreaks in dogs (J Agric Food Chem, 2006; 54: 9623-35), and all varieties of mould have resulted in both acute toxicity and chronic health problems in pets (Int J Food Microbiol, 2007; 119: 95-102).
One of the worst outbreaks occurred in late 2005, after veterinarians at the Mendon Village Animal Hospital, in Mendon, NY, noticed that a number of dogs had presented with similar serious and sudden symptoms after consuming a particular brand of Diamond pet foods. When some dogs died, their bodies were sent to Cornell’s Animal Health Diagnostic Center (AHDC), where researchers discovered the presence of aflatoxin, and a common cause of death due to liver failure. By early 2006, the death toll had reached 100 dogs-all of which were found to have high levels of aflatoxins in their system.
Although Diamond, Country Value and Professional recalled various lots of their brands, many dog and kennel owners remained unaware that the contaminated lots-shipped to some 24 countries-had been recalled. Cornell’s College of Veterinary Medicine became the defacto clearing house for information about dog-food poisoning, offering to analyze blood and liver samples from any sick dogs across America suspected of food poisoning.
“Entire kennels have been wiped out,” noted Sharon Center, professor of veterinary medicine specializing in liver function and disease, at the time. “I’ve been working with liver disease in dogs for 30 years, and I’ve never seen such miserably ill dogs.”
One reason for the high mycotoxin levels in pet food is the inherent risk of contamination in all processed cereal products. Fumonisins, in particular, are a very common contaminant in both maize-based foods and feeds not only in the Far East, but also in France, Italy, South America and the US. This problem is a constant challenge for the processed food and pet-food industries because of grain-processing, storage condi-tions and synergistic interactions between moulds (J Agric Food Chem, 2006; 54: 9623-35).
Mycotoxins are produced in two ways. Although some invade plants before harvest, most are able to colonize a stressed plant and contaminate it after harvest in storage, particularly when plants are grown outside of their temp-erature adaptation. Once stored, the most common causes are too much moisture, particularly when plants are not dried immediately after harvesting, and damage to the grain, particularly from insects.
The latest approach to mycotoxin control is mycotoxin deactivation, using yeast, enzymes or bacterial strains plus radiation, extraction with solvents and other chemical or biological agents-all with their own potential effects on food.
A study of raw maize received as imports and at major maize mills discovered that up to 8 per cent of samples did not meet the EC statutory requirements for maximum permissible levels of aflatoxin B1. Furthermore, fumonisins and zearalenone were detected in virtually every sample, with 41.7 per cent of maize containing more than 100 mcg/kg of zearalenone and 48 per cent of samples containing more than 100 mcg/kg of total fumonisins. Although cleaning the maize lowered the concentrations of all mycotoxins, 60 per cent of aflatoxins and 68 per cent of fumonisins remained (Food Addit Contam, 2000; 17: 407-16).
In one recent study of 37 samples of cereals and feed, 29 per cent of cereals were contaminated with fumonisins, ochratoxins or zearalenone above the permissible limit for humans, and at least two toxins appeared in up to 54 per cent of samples (Arh Hig Rada Toksikol, 2009; 60: 427-34). Although, in general, neither we nor our pets consume high levels of myco-toxins, no one knows the effects of chronic ingestion of low levels of these moulds (Dtsch Tierarztl Wochenschr, 2004; 111: 307-12).
Another reason for the growing danger in pet food is the sheer amount of cereal now used in them. Largely because there are such lax laws about what constitutes ‘food’ in dog or cat foods (the American Feed Control Officials, which determines the labelling of pet food in America, are largely poacher-turned-game-keeper industry insiders), pet-food manufacturers are allowed to call their products ‘beef dinners’ with only 5-per-cent beef in the concoction, and ‘with beef’ with only 3-per-cent beef product in the total weight. The remainder is largely made up of highly processed cereals-usually corn or corn byproducts.
If you are concerned about mycotoxins, you would do well to avoid anything but the new organic pet foods that specify 60 per cent of the product as meat and use less-processed wholefoods-or better yet, feed your pet home-cooked or raw food. It’s also important to give your pet supplements of antioxidants and omega-3 fatty acids, which can protect against mycotoxin poisoning to some degree.
Lynne McTaggart
Factfile: In case of mycotoxin poisioning . . .
If your dog shows the following symptoms, arrange for liver function, enzyme and blood tests immediately, as these can help to detect liver injury or problems with blood-clotting:
WDDTY VOL 22 NO 10 January 2012
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