Two Uncommonly Diagnosed Toxins: Copper and Tremorgenic Mycotoxins
Presenting Author: Laura Wade, DVM, Dipl ABVP (Avian)
Advanced Avian & Exotic Pet Care, All Creatures Animal Hospital, Amherst, NY
Interpretive Review and comments by Dr. Nemetz:
Toxins are abundant (Click here for Handout) in the household environment, yet often overlooked in the diagnosis of companion avian disease. The main reason is that owners rarely witness their pet ingest or inhale the toxic or potentially toxic agent. To compound this is the fact many clinical presentations mimic more common infectious and metabolic diseases and there are very few diagnostic detection methods available to confirm a veterinarian's suspicion.
Common toxins of the house include chlorine bleach, tobacco smoke, polytetrafluoroethylene (PTFE) gas (Teflon),avocados, zinc and lead poisoning. Dr. Wade presents two other toxins that may have more significance than previously thought: tremorgenic mycotoxins and copper.
Mycotoxins are secondary metabolites (waste products) produced by fungi growing on agricultural products before or after harvest or during transportation or storage. It is estimated that 25% of all food commodities produced on Earth are contaminated with mycotoxins. The most common mycotoxins are:
- Aflatoxin B1 - produced by Aspergillus species and found mostly in corn, peanuts, cottonseed. It is carcinogenic and toxic to the liver.
- Ochratoxin A - produced by Aspergillus and Penicillium species.
Agricultural products that may harbor mycotoxins include edible nuts, cereals, dried fruit, apple juice, and dairy products. Conditions that favor mold growth are moisture content >13%, relative humidity >70%, temperature >55oF, and pH>5. Mycotoxins are heat stable and survive pelleting, canning, and other processing. Even though these may produce damage to various cells of the body, none have classic clinical signs in animals. This, Dr. Wade explains, is why mycotoxicosis is do difficult to diagnose and patient history is so important to uncovering the cause.
Mycotoxins primarily affecting the central nervous system include those from the genera Penicillium, Aspergillus and Claviceps. These Tremorgenic mycotoxins luckily are not as common as those listed above. These are primarily found in moldy cheese, bread, pasta, fruit, corn, cereal grains, soybeans, and nuts (especially walnuts and peanuts). Tremors caused by these mycotoxins can also be caused by vitamin B6 (Pyridoxine) deficiency.
Overall, Dr. Wade explained, the best treatment for any of these mycotoxins is supportive care and removal of the suspected contaminated product. Since other causes are possible, good history, blood chemistries, and other diagnostics are needed to rule out other neurotoxins. The good news is that with a proper diagnosis and supportive care, most cases will survive.
Copper is an essential trace element of the body. Deficiencies lead to defects in pigmentation, keratinization, bone formation, myelination (nerve formation), heart formation, lung development, and connective tissue formation. However, too much copper is a well known toxin in many species.
Copper sources include paint, kitchen utensils, electrical conductors, copper wire, pennies minted before 1982, and leather. It is also found in metal alloys (brass and bronze). The form of copper influences the toxicity of the product and is too detailed for this summary. However in its toxic form it can cause damage to the proventricular and ventricular epithelium, the liver and kidneys as well as cause damage to the red blood cell membrane causing it to rupture. The level ingested determines the organ most effected.
Treatment is by using chelating drugs (D-penicillamine (Cupramine), Dimercaprol (BAL), Calcium versenate (CaEDTA)) to bind up the copper and supportive care.
Dr. Wade's paper was especially interesting to me because of the many "toxicity" cases presented to The BIRD Clinic over the years with suspicion of mycotoxins or copper as the underlying cause.
Since mycotoxicosis is so vague, only cases that have died and liver tissue analysis done have there been a confirmed diagnosis. A client's best prevention is not offering your birds products that have a higher risk of mycotoxin production, especially if you live in more humid climates. Nuts, especially peanuts and walnuts carry the highest risk as well as corn products.
Copper toxicosis has been seen at The BIRD Clinic mostly in small species that tend to get their beaks into all the wrong places (budgies, lovebirds, cockatiels). The most common source of toxicity is electrical cords found throughout a household. It only takes one strand of copper no more than 2mm in length to cause acute toxicosis with depression, regurgitation, ataxia (weakness), dehydration, anorexia (not willing to eat) and even death.
For years I have explained to my clients that a house is NOT a safe place to let a pet bird roam unattended. Birds are fast and mischievous. They seem to know all the wrong things to chew on. Every week a bird is presented to the clinic with some form of toxin ingested. Please be very careful and keep our pet birds safe.