Mycotoxin alert for rural SA

SA’s subsistence-farmed grain may be prone to dangerous levels of aflatoxin and fumonisin. A “farm to fork” health check is urgently needed. Roelof Bezuidenhout spoke to Edson Ncube.
Issue date: 30 May 2008

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In SA’s subsistence farming districts, levels of fumonisin and aflatoxin in grain are so high that farmers and rural communities are at serious risk of eating contaminated food. So says a study by Ncube and Dr Bradley Flett of the ARC Grain Crops Institute (GCI) in Potchefstroom, in collaboration with Prof Altus Viljoen of the University of Stellenbosch.

Ncube warns fumonisin has already been associated with the high risk of oesophageal cancer in Butterworth and Centane. In one instance aflatoxin-contaminated maize killed more than 100 people in Kenya.

“Mycotoxins such as fumonisins and aflatoxins are produced by fungi and are harmful to animals and humans,” says Ncube. “Contamination of maize and groundnut grain is often most severe in rural areas, where farmers are unaware that these substances exist and they tend to follow practices that can contribute to mycotoxin production in their crops. Subsistence farming practices during pre- and post-harvest periods affect a crop’s susceptibility to fungal infection, and associated mycotoxin production.”

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Ncube explains that mycotoxin-producing Aspergillus spp. and Fusarium spp. in particular are common in grain exposed to high temperatures, drought stress and insect damage. “These conditions are common to SA’s rural areas, where farmers can’t afford the chemicals and commercial seed required to ensure healthy and safe crops. Their biggest problem is a general lack of information on how to grow healthy maize.”

The researchers warn an increase in the maize price can lead to food insecurity and potentially result in the consumption of mycotoxin-contaminated grain and derived products. They suggest measures such as identifying critical control points and using hazard analysis critical control points (HACCP) in a “farm to fork” system.
hey’d also like to see awareness programmes targeted at extension officers, particularly in areas where communities rely on maize – irrespective of its quality – as their primary source of food and income.

The danger
Food contaminated with aflatoxin can cause acute or fatal illness and is associated with liver cancer. Eating fumonisin-contaminated maize is associated with oesophageal cancer and neural tube defects in babies.

In chickens, pigs and cattle aflatoxin-contaminated animal feed causes oxidative stress, loss of productivity, liver necrosis, haemorrhage and death.

Fumonisin-contaminated feed causes equine leukoencephalomalacia (ELEM) in horses and donkeys, porcine pulmonary oedema in pigs and loss of productivity in other livestock. No statutory maximum levels have been set for fumonisins in maize in SA. Commercial grain grading procedures, as defined by Act 112 of 1990, are applied only to reduce the risk of mycotoxin contamination of food. The US has set maximum levels of fumonisin in maize intended for direct human consumption at two parts per million (ppm) (Table 1), while the EU has set them at 1ppm. Contact Edson Ncube on (018) 299 6100 or 072 663 5839, or e-mail [email protected] |fw

Where highest fumonisin levels were found

Fumonisin contamination was highest in KZN, ranging from 0ppm to 21,8ppm, far exceeding US and EU prescriptions (see Figure 1). Contamination was particularly severe near Mbazwane, Jozini, Pongola, Vryheid and Manguzi in northern KZN. Limpopo had the second highest fumonisin levels in maize grain, ranging from 0ppm to 4,8ppm. The Thohoyandou and Mokopane districts were most severely affected. The Eastern Cape’s Lusikisiki and Engcobo districts were worst contaminated. Contamination in Mpumalanga hit 5,3ppm, but only in the KwaMhlanga area.

Where highest aflatoxin levels were found

In maize produced around Port Shepstone, Highflats, Izingolweni, Ndwedwe and Underberg in southern KZN, and in the Jozini district in northern KZN, aflatoxin levels far exceeded the maximum set by the US, the EU, and SA’s Department of Health (see Figure 2). In Limpopo aflatoxin levels ranged from 0ppm to 16ppm, in Mpumalanga from 0ppm to 19ppm, and in the Eastern Cape from 0ppm to 12ppm.