Antibiotic-resistant marker genes used in genetically engineered (GE) plants might already be harming South Africans.
Scientists and activists opposed to genetic engineering are increasingly concerned that plants with this kind of genetic manipulation are reducing the efficacy of medicines by creating widespread resistance to antibiotics.
Biotechnologists use gene markers to determine if a gene transfer has been successful and to identify where the implanted gene has attached itself in the DNA sequence of the host organism. They make the new genetic material antibiotic-resistant so that only the genetically engineered material survives when an antibiotic is applied. The material is implanted into the DNA sequence of the plant with a bacterium or a virus.
Biowatch, a South African environmental group, has collected research that shows the AAD antibiotic marker gene can be present in both types of GE cotton, Bollgard and Roundup Ready, grown throughout the country. AAD creates resistance to Streptomycin and Spectinomycin. Both drugs are used in the treatment of infections related to HIV/Aids, TB and gonorrhoea.
Though cotton is not eaten, by-products such as cotton seed oil and cotton seed cake are used in animal feed. Cotton is also used in sanitary towels and tampons, babies’ nappies, bandages and other wound dressings.
South Africa is the only country in Africa to have approved the planting of GE white maize for human consumption. GE soya is also grown locally.
The government has decided against imposing mandatory label-ling of GE foods, saying labelling would be too costly to enforce and would push up prices for end users.
Consumers therefore have no way of distinguishing between GE and non-GE products, which activists say strips South Africans of their right to make an informed choice.
“We are worried because there has been no long-term testing, taking place over generations, to establish the impact of GE foods on humans,” said Haidee Swanby of Biowatch.
Winston Hide, professor of genomics and bioinformatics at the University of the Western Cape (UWC) and director of the South African National Bioinformatics Institute says: “As a scientist I am saying that we do not know enough about biology to say that GE foods are safe.”
Hide says that genetic engineering with antibiotic-resistant markers compromises human health by harming the body’s ability to fight pathogens. Research has also shown that transgenes and antibiotic-resistant marker genes from transgenic plants end up in soil fungi and bacteria.
“The problem is that genes do not stay in one place. So once the marker genes from the plants are ingested they are transferred into the bacteria living inside the human gut,” he said.
Hide criticises the government’s stance on labelling. The government has also not heeded precautions such as the internationally upheld precautionary principle that science should err on the side of caution where there is possible risk to humans, animals and the environment.
“It is hugely concerning that there is a strong lobby of poorly informed government officials and scientists who are misleading the public. The use of antibiotic gene markers is a big deal and no one should have the right to force this unproven technology on to another human being. This position further compromises the public and is just like what the government is doing with the HIV/Aids issue in this country,” Hide said.
The British Medical Association (BMA) has called for antibiotic-resistant marker genes to be banned.
“We believe that the use of these marker genes in GE foodstuffs is a completely unacceptable risk, however slight, to human health,” said a BMA spokesperson.
The association says that health risks from antibiotic resistance developing in micro-organisms are one of the major public health threats of the 21st century.
Dr S Prakash, senior biochemist at the Department of Gastroenterology and Human Nutrition at the All India Institute of Medical Sciences (AIIMS), says GE crops could compound problems with Aids.
Prakash says GE plants can inhibit the formation of antibodies and thereby aggravate infections related to autoimmune diseases, including those caused by HIV/Aids.
“If a plant is genetically modified at any time, either by conventional breeding techniques or genetic manipulation, it ultimately results in the introduction of new proteins which can bring about drastic changes in its properties,” Prakash said in the paper he delivered at a convention on transgenic rapeseed-mustard in March.
“Such genetically modified plants, with changes in their amino acids, can inhibit the self-formation of antibodies, substances which assist in combating harmful foreign bodies, thereby enhancing autoimmune diseases such as hepatitis B and Aids.”
Pro-GE scientists believe the furore is little more than a storm in a teacup and accuse the naysayers of misinformation.
“This is a complete non-issue and there is more reason to be concerned about the existing antibiotic resistance that has been created by irresponsible prescription and irresponsible patient use of antibiotics,” says Jennifer Thomson, a professor at the University of Cape Town’s department of molecular and cell biology.
Thomson says that the antibiotic-resistant genes cannot remain stable or be expressed inside the human body and therefore pose no danger. She said the dosage of antibiotics in the modified plants was too small to have any significant effect.
“Antibiotic resistance falls squarely in the field of microbiology and as an expert in this area I am more qualified to comment on this than scientists in other branches of biology,” says Thomson.
She says the antibiotics used in GE foods are seldom used any more in modern medicine. Shadrack Moephuli, senior manager of genetic resources at the Department of Agriculture, shares her view.
“The antibiotics used in GE crops in South Africa are antiquated medicines and because these crops are cooked before they are eaten the antibiotics are destroyed in the process,” he says.
Moephuli says there is also no evidence that the antibiotics from GE plants can be passed along the food chain from plants to animals and to human beings.
“We do have a general concern about the health implications of antibiotic-resistant marker genes, but this is all about risk assessment and we feel the advantages outweigh the disadvantages.
“We continue to monitor [the use of antibiotic-resistant marker genes] and to proceed with caution as each appli-cation for GE crops is made. For example, we wouldn’t approve an application that makes use of an antibiotic that is still commonly used,” he says.
But this is the very risk factor that worries scientists and activists.
“If GE is so safe then why does it need to be monitored so closely?” Hide asks.
Glenn Ashton from the anti-GE lobby group SAFeAGE (South African Freeze Alliance on Genetic Engineering) says: “We are not convinced because these foods have never been tested on human beings and we intend to take strong action at the World Summit”.