The mycotoxin menace
January 01, 2006
by Melissa Alexander
Hundreds gather at World Mycotoxins Forum to discuss ways to combat a problem that costs the grain industry billions of dollars each year
by Arvin Donley
NOTE: This is the final article in a three-part series on mycotoxins and their impact on the grain and feed processing industries. The first and second articles in the series were published in the 2005 September and November issues of World Grain.
Mycotoxins, toxic substances produced by fungi, can easily enter the human food chain directly via plant products such as cereal grains and oilseeds. There is evidence to suggest human consumption of mycotoxins can cause a wide range of health problems, which is why scientists are searching for ways to eliminate or reduce mycotoxins from the food supply.
The latest strategies for the prevention and control of mycotoxin contamination in food and animal feed products were discussed at the World Mycotoxins Forum, Nov. 10-11 in Noordwijk, the Netherlands.
The Forum, which drew 250 participants from 36 countries, including leaders from the scientific community, industry and government, focused on a variety of topics, including:
• regulatory issues and international developments;
• progress on major mycotoxins and emerging problems;
• mycotoxin prevention: what’s on the horizon; and
• mycotoxins in the food chain.
The following are highlights from three presentations given at the conference. For the list of other presenters at theforum,visit http://www.bastiaanse-communication.com/html/wmf_new.ht.
IMPACT OF MYCOTOXIN LEGISLATION ON WORLD TRADE Because agricultural commodities containing mycotoxins are traded internationally, the mycotoxin issue is a sensitive one for major exporters of products such as maize.
In her presentation on the impact of mycotoxin legislation on world trade, Dr. Felicia Wu, University of Pittsburgh Graduate School of Public Health, Pittsburgh, Pennsylvania, U.S., said developing more uniform standards for foodborne mycotoxins is necessary to settle trade disagreements between food importing and exporting nations.
Currently, the standards vary from country to country. The mycotoxin problem impacts industrialized nations and developing nations in very different ways, Wu said. Losses for industrialized nations tend to be economic, while high levels of mycotoxins tend to have a greater affect on the health of citizens in developing countries.
Wu’s recent study — "Mycotoxin Risk Assessment for the Purpose of Setting International Regulatory Standards," published in Environmental Science & Technology — included an analysis of the risks and costs associated with fumonisins (a class of fungal mycotoxins) in maize. The U.S. Food and Drug Administration has set guidelines to industry for levels of fumonisin acceptable in human food at 2 mg/kg. But very few regulations exist in other nations regarding acceptable fumonisin levels.
The empirical economic model in Wu’s study shows that moving from a harmonized fumonisin standard in maize of 2 mg/kg to 0.5 mg/kg would result in an increased worldwide annual market loss of more than U.S.$200 million through rejected maize, with the U.S., China, and Argentina bearing the brunt of the economic burden.
The main beneficiaries of stricter mycotoxin standards, in this case, would be net importers of maize, such as Japan, Korea, Mexico, Egypt, Canada and Taiwan, which have a high prevalence of hepatitis B and C, diseases that are exacerbated when they interact with mycotoxins. With the possible exception of Taiwan, all of these countries have low hepatitis B and C incidences.
Conversely, nations with high hepatitis prevalence — China and sub-Saharan African countries — may increase the risk to their populations, Wu said, by attempting to export their best-quality crop and keeping the most contaminated food to be consumed domestically.
Wu said the study found that addressing a broader set of health, economic and risk questions can better inform policy decision-making, particularly when arriving at international acceptable standards for trade. If mycotoxin regulations were based solely on direct health effects, important questions of the economic feasibility of meeting excessively strict standards could be ignored, with potentially disastrous consequences for less developed food exporting countries.
EMERGING ISSUES IN SOUTHERN EUROPE Mycotoxins have been suspected as the cause of several epidemics in Italy during the past two centuries, including a pellagra outbreak in the 1800s, in which thousands of people in Northern Italy were stricken with gastrointestinal disease, dermatitis and severe central nervous system disorders.
In his presentation on emerging mycotoxin-related issues in Southern Europe, Dr. Gianfranco Piva, Università Cattolica Sacro del Cuore’s Institute of Food Science and Nutrition, focused on an outbreak in 2003 in Northern Italy in which maize containing high levels of aflatoxin was fed to dairy cattle, leading to widespread contamination of milk.
He noted that the region was plagued by extremely hot and dry weather during the summer of 2003, which allowed aflatoxin to flourish in the drought-stressed maize plants. The weather conditions resulted in a widespread reduction in crop cycle length, with rapid drying and anticipated ripening. Consequently, farmers harvested maize with a lower moisture content and stored the maize without drying or cleaning it.
A survey of 110 samples of maize taken from different growing areas in Northern Italy in September 2003 showed a 75% positive sample for aflatoxin B 1 (AFB 1 ) with a mean and maximum value of 4.4 and 154.5 parts per billion (ppb), respectively.
In Lombardy alone, over a period of 20 days in early October 2003, more than 4,000 inspections were carried out on samples of milk from different farms and dairy factories. More than 33% of those milk samples were above the established threshold of .05 µg/kg of aflatoxin M 1 (AFM 1 ).
Farmers were not allowed to put their milk on the market in the days after a positive test until their milk was found, in a later inspection, to be back to an acceptable level.
Systematic analysis of maize and raw materials used in dairy cow feeds and a well-run information campaign rapidly reduced the problem.
To comply with milk production parameters, daily intake of AFB 1 had to be measured. Other measures involved careful corn cleaning to remove broken kernels and dust, which were found to contain higher levels of contamination. By following the cleaning and removal procedures, batch contamination was reduced by nearly 70%.
In 2004 and 2005, a change in climactic conditions and compliance guidelines by farmers led to a dramatic reduction of the problem.
An Italian research project, AFLARID (aflatoxin reduction in milk), funded by Italy’s Ministry of Agricultural Policy, is focusing on different aspects of the milk and dairy production chain in order to identify suitable and appropriate action and procedures. An alert system based on meteorological data collection and collaboration and the development of a predictive model for the aflatoxin is central to the project.
USE OF GMOS AS A PREVENTION STRATEGY The economic impact of mycotoxin contamination of food crops has been estimated to range from U.S.$500 million to U.S.$1.5 billion in the U.S. alone, according to Monsanto’s Bruce Hammond, who spoke at the forum about the potential for GMO crops to prevent mycotoxin formation. He added that in other areas of the world, the economic impact of mycotoxin contamination has not been well studied but is believed to be significant.
Biotechnology is providing tools for researchers to understand the complex dynamics involved in fungal infection and production of mycotoxins, said Hammond. The fungal synthetic pathways for mycotoxins such as aflatoxin, fumonisin and deoxynivalenol (DON) are complex, involving multiple enzymatic steps.
Research efforts are geared toward identifying critical control points in mycotoxin production.
Some researchers have proposed introducing genes into plants that produce mycotoxin-degrading enzymes. Others are using biotechnology to help identify natural resistance factors to fungal infection that are present in plants such as maize. Once identified, the coding sequences for these resistance factors may be introduced into susceptible varieties of maize to see if they improve protection against fungal infection.
Researchers also are developing healthier maize plants that can withstand environmental stress factors, such as insect damage, drought and nitrogen deficiency, that may increase susceptibility to fungal infection in the field.
Insect feeding injures maize kernels, creating ports of entry for fungi that produce ear rot and mycotoxins. Protecting maize kernels against insect feeding can reduce fungal infection and mycotoxin contamination, Hammond said.
He said field tests in the U.S., France, Italy, Argentina and Turkey have shown that Bt maize, a genetically modified variety, reduces fungal infection and mycotoxin contamination by protecting corn kernels against insect feeding. The tests showed that:
When averaged across 180 sites for two consecutive years, fumonisin levels for several different Bt hybrids were approximately 50% lower in the U.S.
• In Argentina, fumonisin levels were on average 60% lower in one Bt hybrid tested at more than 50 locations for one year.
• In Turkey, one Bt hybrid tested for two consecutive years had fumonisin levels 85% lower than a control group.
• Consistently lower fumonisin levels were found in Bt hybrids in Italy and France.
Building on this initial success, Hammond said the next offering of Bt maize will produce proteins that will provide better protection against a wider variety of insect pests such as fall armyworm and corn earworm.