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AMR, megafarms and zoonoses

AMR, megafarms and zoonoses

22/08/17Government

PEN explores the concerns of livestock sciences, from antimicrobial resistance to megafarms and zoonoses

In a post-Brexit Britain, concerns from within the environmental and animal sciences are mounting around the demand for intensive farming. Commonplace in the US, farms with as many as 1.7 million animals – megafarms – could be the future of British agriculture and farming. Campaigners are raising concerns over animal welfare, where livestock are kept in intensive conditions with little access to the outside perimeters of their holdings. Researchers have also found evidence which locates superbugs in the vicinity of intensive farming. However, farming leaders suggest that through the mass approach they can deliver efficient food production without jeopardising standards.

Tracy Worcester, director of Farms not Factories, said: “Local residents will be poisoned by ammonia and sickened by antibiotic-resistant organisms and bio-aerosols that come out of the sheds,” as was reported in The Guardian.

Chickens have also been a focus of concern as an effect of the forthcoming Brexit. Debates have centred on the treatment of chickens, and whether the UK would import chlorinated chicken from the US. The UK government has, however, reassured consumers that treated chickens would not appear on the British market and that high standards of livestock welfare would be maintained.

Antimicrobial resistance and agriculture

Animals on US megafarms are fed growth-promoting hormones, as well as antibiotics. As a result, antimicrobial resistance (AMR) is of mass concern – referring to the ability of micro-organisms to withstand antibiotic-based treatment. The European Food Safety Authority (EFSA) says on its website that ‘Zoonoses are infections or diseases that can be transmitted directly, or indirectly, between animals and humans, for instance, by consuming contaminated foodstuffs’. Diseases under zoonoses include brucellosis, salmonellosis and listeriosis.

Subsequently, when AMR is present in zoonotic bacteria, it can compromise the effective treatment of infectious diseases in humans. To counteract such concerns, the European Commission launched a 2011 action plan containing 12 actions for implementation within EU member countries, identifying seven areas where measures are of a necessity.

Within this, the EU legislation on zoonoses places an obligation on member states to monitor trends in antimicrobial resistance, which may pose a threat to public health. Food-borne zoonotic diseases are caused by consuming food contaminated by pathogenic micro-organisms such as bacteria, toxins, viruses and parasites. Many of these are found in the intestines of healthy animals.

An EU approach

Risks of contamination are present from the farm to the kitchen, requiring prevention and control throughout the entire food chain. In response to the 320,000 human cases per year, the EU has adopted an integrated approach to limit and control the impact of zoonotic diseases. The approach is a unified system which covers risk assessment through data collection and analysis, as well as risk management measures. Such measures involve EU member states, the European Commission, European Parliament, EFSA, the European Centre for Disease and Prevention and Control (ECDC) and economic operators.

This co-ordinated approach, led by the European Commission and enforced by member states, helped to reduce Salmonella cases by almost one-half between 2004 and 2009 (196,000 cases in 2004 and 108,000 in 2009). In 2006, an EU-wide ban was enforced regarding the use of antibiotics as growth promoters in animal feed. As the final step in phasing out antibiotics for non-medicinal purposes, the ban contributed to the commission’s overall strategy to address the emergence of bacteria and other microbes which have become resistant to antibiotics due to their overexploitation or misuse.

Economics and ethics

The British Society of Animal Science (BSAS) aims to improve the understanding of animal science and the ways in which they can contribute to ensuring that food is produced both economically and ethically. BSAS has a mission to enhance the welfare and productivity of farm animals to help produce quality, safe, and environmentally sustainable food.

At the Future of Animal Science: BSAS Annual Conference 2017, held on 25-27 April in Chester, UK, Professor Liam Sinclair, the president of the BSAS, said that Westminster should use the Brexit break from European agricultural policy as an opportunity to change its approach to farming. If it does not do so, Sinclair added, it could put the future of UK food production at risk. Sinclair also said that the UK government needs to engage with all sectors of the industry to develop policies that are firmly focused on science and innovation, as well as adding value to the country’s food production.

“Coming out of the EU means the end of the CAP and single farm payments,” Sinclair said, “and if we want to extend our global competitiveness and maintain our current standards of production, food quality and animal welfare, it is essential that government develops well thought out, focused policies that are based on sound evidence and supported by targeted incentives.

“This is a chance to join up thinking across government and the industry as a whole. It will be difficult to do, but it’s vital that it happens.”

BSAS chief executive Bruce Beveridge added that if Westminster fails to acknowledge the importance of the livestock industry to the UK economy, “there is a major risk to the UK’s balance of trade, and potentially food security, tourism and employment.”

Avian flu

Transmission of avian flu is thought to be carried through an eggshell-like mineral layer, acquired by the virus from a high calcium concentration in the intestines of birds. A report made by Chinese researchers in Angewandte Chemie showed that mineralised viruses are significantly more infectious, robust and heat stable than native viruses. The report explains why humans are more susceptible to catching avian flu from birds, as opposed to other humans, and has the potential to augur developments in treating avian flu.

Close contact with diseased birds, or their faeces, is understood to be the predominant source of avian flu infections in humans. Previously, it was thought that these viruses crossed the bird-to-human barrier as a result of mutation or recombination with other pathogens. However, new research has demonstrated that avian flu viruses isolated from infected humans have the same gene sequences as those taken from birds.

Researchers working alongside Ruikang Tang at Zhejiang University, Hangzhou, China, claim that humans become infected with the disease as the virus acquires a mineral ‘shell’ whilst still in a bird’s intestines. As a result, the digestive tract of birds — the primary location of avian flu viruses — provides a calcium-rich environment wherein the virus becomes mineralised, i.e. protected from the bird’s own immune system.

In experiments with cell cultures and mice, mineralised viruses have proved to be considerably more infectious – and fatal – than native viruses. In humans, the avian flu virus infects the airways and can be detected in bodily fluids, where the calcium concentration is too low for mineralisation. After mineralisation has occurred, the shell transforms the electric surface potential of viruses, causing them to be absorbed in a more efficient way into the surfaces of host cells.

Typically, a virus arrives at the receptors on the surface of the cell and is consequently accepted into it. The mineral layer inhibits this process and, instead, stimulates an efficient modification of its own. Once inside, mineralised viruses enter into lysomes, where a slightly acidic environment dissolves the mineral shell and releases the viruses, infecting the host.

Infection biologist Felipe Cava of the Department of Molecular Biology at Umeå University, Sweden, confirmed through a similar study how the rapid identification of cell wall biology in this bacteria has led to developments in taxon-specific AMR strategies.

Cava said: “We identified a novel peptidoglycan structure displayed by acetic acid bacteria, which are very relevant microbes in the food industry. One of these modifications occurs in the diaminopimelic acid, a highly conserved amino acid in the peptidoglycan cell wall of Gram-negative bacteria. In addition, these species have devised an original way of cross-linking their peptidoglycan mesh, which is different to what has been described for other bacteria so far,” explains Felipe.

The results of the study were published in the Journal of the American Chemical Society.

Pan European Networks Ltd