Dr Liesel van der Merwe is a small animal medicine specialist. Send her your questions: This e-mail address is being protected from spambots. You need JavaScript enabled to view it .

Dr Liesel van der Merwe

Toxins in dog food are not always “deliberate poisonings” but can also be produced as metabolic by-products by fungi.

These mycotoxins are a problem in large animal feeds as well as in dog food. Aflatoxin is the mycotoxin currently causing death due to liver failure in dogs in the Pretoria region.

Aflatoxin is produced by a group of fungi of the aspergillus and Penicillium species. These fungi are found throughout the world as soil contaminants and grow on most natural products, including maize, peanuts, rice, soybean, wheat and oats. They only produce the toxin in specific temperature and moisture conditions and this occurs mainly when crops are stressed by drought, insect damage and inappropriate handling and storage.

Dogs and cats are especially susceptible to the toxic effects in feed. Aflatoxins are readily absorbed from the gut and transported to the liver, where damage occurs. Aflatoxin contamination is thus a risk in any shipment of natural feed products and testing needs to be carried out. Ideally every single batch of raw material arriving at the feed plant needs to undergo testing for a variety of products. One cannot assume that the same supplier will have the same results as each batch is subjected to their own individual process of handling and storage.

The tests used to evaluate a product are also not all equal. Tests that have lots of false positive results are oversensitive and those that have lots of false negative results are not sensitive enough. It is also important where the cut-off level in parts per million is determined to be.

With many contaminants, even in our water with E coli for example, a balance has to be found where the substance may be present, but not at dangerous levels. Additionally the contaminated feed may not be evenly distributed in the batch delivered and may not be present in the material sampled.

A less expensive fluorescent screening test can be used where a green glow indicates aflatoxin. This test does not measure the amount present. A more expensive specific test that uses high performance liquid chromatography (HPLC) is used to determine actual levels in the food. The maximum level in the USA is <20ug of aflatoxin per kilogram of food.

Aflatoxins attack the liver and cause varying degrees of liver failure. If animals survive the initial disease they can still unfortunately succumb to liver failure months later as the liver tries to heal itself and fibrosis results in liver cirrhosis.

The liver has many functions: It is essential in glucose availability; it manufactures proteins; it manufactures clotting factors; and it metabolises and excretes drugs and byproducts in the bile.

Dogs which eat high levels of toxin become acutely ill, their skin and gums become yellow, they vomit, often blood, and they have profound bleeding tendencies.

Prognosis is guarded. Even with intensive medical care, survival is only about 36% according to a recent study. Lower grade toxicities may recover, but are then at risk of cirrhosis in later life.

If you suspect that your dog is suffering from food intoxication it is vital that you keep a sample of the food or the packaging. The food can be tested and the packaging allows the affected batches to be identified and traced.

It is also vital for pet owners to realise that quality raw materials and raw material testing cost a company money. You pay for what you get. If you are buying cheap dog food you cannot expect top quality manufacturing control guidelines and top quality raw materials of either protein or grain origins.