Pigs drinking from a trough©Tim Scrivener

A virus that destroys illness-causing bacteria but is harmless to humans and animals could help reduce antibiotic use in the pig industry.

Scientists at the University of Leicester are working to develop “friendly viruses” known as phages to help treat illnesses such as salmonella.

They hope the treatment, known as phage therapy, will help farmers and vets target and treat disease in pigs more effectively.

Discovered in 1915 and long used in Russia as an alternative to antibiotics, phages attack bacteria by latching on to bacterial cells and replicating until they kill their host.

Unlike antibiotics, which destroy both good and bad bacteria, phages target specific bacteria of certain illnesses, which is why scientists have become interested in them once again.

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“Phages offer an alternative to antibiotics, especially in the face of growing antibiotic resistance,” said Martha Clokie of the university’s Department of Microbiology and Immunology, who is leading a Bpex-funded study into using phage therapy in pigs.

“Antibiotic resistance has evolved over many years, but by using antibiotics indiscriminately we have exacerbated it.”

Speaking at the Bpex Innovation Conference at Stoneleigh Park, Warwickshire, last week (13 May), Prof Clokie said antibiotic resistance was growing rapidly, yet fewer antibiotics were being developed – mainly because they were not profitable for pharmaceutical companies.

Phages were a good alternative for several reasons, she added, partly because they attack bacteria in a way that means they can treat more complex diseases than antibiotics can, but also because they were selective in what they attacked.

“Antibiotics wipe out all the bacteria – both good and bad,” she said. “So if you a treat a pig for one thing, you cause an imbalance in the pig’s useful bacteria. Phages can target one, making them a more effective treatment.”

As part of the Bpex study, Prof Clokie and her team will carry out tests on pig units to identify which strains of salmonella exist there.

They will then examine which of the phages occurring naturally in a pig’s body are capable of attacking those salmonella-causing bacteria, which could lead to them developing a treatment in future.