MYCOTOXINS - Global Problem

Mycotoxins are fungal toxins and a secondary toxic - metabolites which are produced from various toxigenic fungus. These metabolites have harmful effects on animal productivity and health, also increased over the past few years. Mycotoxin produces acute and chronic toxicity in animals and cause reduction in animal yield.

On the basis of negative effect on poultry production and feed contamination aflatoxins, zearalenone, fumonisin, deoxynivalenol and ochratoxin A are considered to be the most important mycotoxins. Though multiple mycotoxins are found throughout the globe, yet the individual mycotoxin prevalence in the animal feed differs from area to area.

 
 
According to the FAO (Food and Agriculture Organization) approximately 25% of crops are affected by mycotoxins annually (CAST, 1989) , which would extrapolate to billions of dollars (trail et al., 1995) Annual economic cost of mycotoxins to the U.S. agricultural economy is estimated to average $ 1.4 billion (CAST, 2003) . Economic losses are due to effects on livestock productivity, losses in crops and the costs effects of mycotoxicosis treatment programs.
 
Last news from FAO shows that samples collected from 16490 different feed raw materials in 2013 and 35.9% of them were found to be contaminated with aflatoxin.  (Table-1)
 
 

Joint FAO/WHO food standards programme codex committee on contaminants in foods, Seventh Session, Moscow, Russian Federation, 8-12 April 2013

 Any mycotoxin could be produced from many fungal species, and any fungal strain can produce many mycotoxins.   So, when one mycotoxin is detected, one should suspect that others are also present in a contaminated feed. Nowadays, more than one thousand different chemically identified mycotoxins are isolated.  They are of low molecular weights. Some of them act with each other synergistically as fumonisin-B1 and aflatoxin-B1, ochratoxin-A and aflatoxin, T2 toxin and aflatoxin. Mycotoxins cause a wide variety of adverse clinical signs depending on the nature and concentration of mycotoxin present, duration of exposure, animal species, age, nutritional and health status at the time of exposure to contaminated feed.
The toxin would be produced at pre-harvesting, harvest, during the post-harvest, handling and storage period. According to this period, toxinogenic fungi can be divided into three groups:

a.      Field fungi: Fusarium (F. moniliforme, F. roseus, F. tricinctum, F. nivale)

b.      Storage fungi: Aspergillus, Penicillium (A. flavus, A. parasiticus)

c.      Advanced deterioration fungi: A. clavatus, A. fumigates, Caetomium, Scopulariopsis, Rhizopus, Mucor and Absidia. (Do not infest intact grains but easily attack damaged ones and require high moisture content)

These fungus produce mycotoxin when the environmental situation is available. Toxin production depends on substrate, moisture, temperature etc.  (Table-2)

 
 

Several types of mycotoxins and various effects

Aflatoxin is the most commonly known mycotoxin. They rated as class 1 human carcinogen by the IARC (International Agency for Research on Cancer). According to the studies were four major aflatoxins: B1, B2, G1, G2. In addition to the metabolic products consist of M1 and M2. Aflatoxin B1 is the most common and has the most toxic and carcinogenic effects. Aflatoxin M1 and M2 isolated from milk which dairies fed with aflatoxin contaminated feed.

There will be decrease in the animal yield which is decrease in weight gain, egg and milk production, feed intake and feed conversion efficiency, fertility and hatchability, with increase mortality, organ weight and hepatocellular hyperplasia.

Fumonisin B1 developer of cancer, especially trichothecenes with other mycotoxins play an important role on carcinogenesis in humans. Fumonisin occurs in maize and maized based food products and besides their hepatotoxicity and nephrotoxicity, they affected also the immune system. Fumonisin doesn’t included in milk but it damaged the organs of dairy cattle and reduces feed intake, weight gain and milk production.

The major group of mycotoxins which is Ochratoxin, synthesized by Penicillium species. Ochratoxin come across more in cold climates in warehouse. The lower temperature of 5 ˚C can produce ochratoxin. Ochratoxin mostly nephrotoxic and causes distortions in kidney. Ochratoxin effects observed as pulmonary edema and increased mortality in dairy cattle.

Trichothecenes are large group of mycotoxins which includes DON (vomitoxin), T-2, HT-2.  There is two types of trichothecene mycotoxins; Type A and Type B. Poultry is more sensitive to Type A than Type B. Trichothecenes’s mode of actions are inhibit protein synthesis, and has a neurologic, immunodepressive effects. The maximum level of T-2 doesn’t permitted in EU and USA.

 

Identification of Mycotoxin

Detection of mycotoxins is also very complicated. This is because of the synergistic effects of mycotoxins, masked mycotoxins and also the sample will be not references to all rations.

‘’Masked mycotoxins’’ is a newly discovered subject. They are conjugated forms of mycotoxins. They called masked mycotoxins because they are not detectable by analytical techniques.

And also mycotoxins aren’t distributed throughout the feed or food.  However, each method has specific sensitivity, reproducibility within a specific range of mycotoxin levels.

The synergistic effect of mycotoxins varies according to the types of toxins. For example; Aflatoxin and T-2 toxin have a synergistic effect on lethality. (Pierce 1991) T-2 toxin synergized the activity of DON with respect to several parameters including weight gain (swine). (Friend et al., 1992)

Therefore, the best way to fight against mycotoxin is directly protect the animal without losing time with identifying.