Mycotoxicoses

Mycotoxicoses are diseases resulting from consumption or exposure to mycotoxins. Mycotoxins are secondary metabolites of fungi that can cause serious health problems in animals, especially ducks. They are produced by various molds belonging primarily to the species of the Aspergillus, Penicillium, and Fusarium genera. Mycotoxins are produced both pre- and post-harvest in crops and other feed and food commodities. They have also been isolated and in some cases, abundant in straw, dust, materials used for animal bedding, certain pasture grasses, hay, medicinal herbs, fruits and nuts.

Ingestion of mycotoxins can cause acute, overt disease with high morbidity and death to chronic, depressed resistance to pathogens and reduced productivity. Chronic ingestion of low levels of mycotoxins can cause a wide range of metabolic, physiologic, and immunologic disturbances in ducks. The European Union (EU) and the Federal Department of Agriculture (FDA) in the United States, has established limits for several mycotoxins that are regulated.

Mycotoxin	Exposure Effects	Regulatory limits for animal feed
Aflatoxins (AF)	liver damage, tumors, gastrointestinal dysfunction, reduced productivity, birth defects, suppressed immune system	EU: <20 ppb FDA: For starter and grower feeds, corn, and peanut products intended for poultry feed, excluding cottonseed meal: <20 ppb Laying hen feed, corn and peanut products intended for mature poultry: <100 ppb Cottonseed meal intended for all poultry: <300 ppb
Citrinin	kidney damage, watery fecal droppings, reduced weight gain, anemia, hyperkalemia, metabolic acidosis, reduced blood pH	EU/FDA: No restrictions set
Cyclopiazonic acid	Poor weight gain and feed conversion, reproductive tract impairment	EU/FDA: No restrictions set
Ergotamine	Tissue necrosis, neurological signs	EU/FDA: No restrictions set
Deoxynivalenol (DON)	Damages the epithelial intestinal barrier of the gastrointestinal tract, inhibits protein synthesis	EU: < 5 ppm FDA (only advisory level, does not enforce): < 10 ppm for grain and grain by-products and < 5 ppm for complete feeds
Fumonisins	Damages the intestinal barrier of the GI system, decreases nutrient absorption	EU: < 20 mg/kg FDA: < 50 mg/kg
Ochratoxin A (OTA)	Weight loss, granular degeneration in the epithelium and mononuclear cell infiltration and activation of capillary endothelium in the kidney and liver; degenerative changes and depletion of lymphoid organs	EU: < 0.1 mg/kg FDA: No restrictions set
Oosporein	kidney damage, extensive visceral gout, dehydration, reduction in feed intake, decreased egg production	EU/FDA: No restrictions set
Sterigmatocystin	Decreased egg production, reduced feed intake, pale egg shells, liver impairment, embryo malformations and mortality	EU/FDA: No restrictions set
T-2 Toxins (T-2)	Oral lesions, suppressed immune system, irritation, hemorrhage, and necrosis of the digestive tract.	EU/FDA: No restrictions set
Zearalenone (ZEA)	Reproductive damage, egg shell quality, problems with vitamin D3 metabolism	EU/FDA: No restrictions set

Certain types of fungi and mycotoxins are attracted to particular crop species, climates, and weather events, and their distribution differs across geographical regions. The effects of mycotoxins vary widely in ducks and depend on many factors such as whether there is co-contamination with multiple types of mycotoxins, amount (dose) ingested, duration of exposure, species, age, stress level, diet, and immune system. Ducks can develop an acute condition or chronic due to mycotoxins. Diagnosis of mycotoxins in ducks can be difficult, due to a number of complicating factors which include:

• Mold growth is not uniform in feed, which makes testing feed samples difficult, slow and expensive.
• Usually there are multiple mycotoxins involved, making diagnosis difficult as there are additive and even synergistic interactions.
• Mycotoxins affect more than one body system simultaneously.
• Not all mycotoxins can be detected in routine mycotoxin testing by commercial laboratories.
• Forage (hay, silage) and animal bedding (straw, shavings ) are not regulated for the presence of mycotoxins.

Often times, symptoms are generalized and similar to that caused by many other diseases. Also, since chronic cases involve the ingestion of low levels of mycotoxins over a period of times, feed, bedding and pasture contamination is often overlooked. Samples of at least 500g (1lb) of suspected contaminated feed or ingredient should be properly collected in separate containers and promptly submitted to a feed testing laboratory for analysis. Ducks are highly susceptible, and a minimum toxic dose is 0.03 mg/kg of contaminated feed.