Field of Science

Antibiotics & Animals Part 2: The First Warnings

In the previous post, we were wowed by the miraculous discovery that antibiotics could improve the growth and well being of farmed animals, such as pigs and baby chicks. The use of these growth promoters enabled farmers to save money on animal feed and improve the health of their animals. Soon, nearly 50% of all antibiotic sales went to the agricultural industry. Whilst there were some concerns over this unregulated use triggering the development of antibiotic resistant bacteria, without evidence these fell on deaf ears. This would soon change.

We begin this chapter of the story at the Enteric Reference laboratory. The job of this reference laboratory was to receive and catalogue samples of bacteria obtained from intestinal infections occurring around the country. It was during the 1960's that they began to receive samples from concerned farmers.
The environments on intensive farms of this era could best be described as overcrowded factories for disease. The farmers had noticed that calves were particularly prone to getting diarrhoeal infections. The bacteria causing these infections was Salmonella typhimurium, the bacterium responsible for human typhoid disease. This was not only a threat to the health of the herd, and those who interacted with them. Calves were dying. The Salmonella outbreaks needed to be brought under control. This is where it all started to go wrong.

There were two methods that were used to put a stop to Salmonella on these farms. The first method was to use high doses antibiotics to treat visibly sick cattle. The second method was to give lower doses of antibiotics to the rest of the visibly healthy herd, to prevent them getting ill. I say "visibly" because cows can carry Salmonella without showing any symptoms, so it is likely that plenty of the cows with Salmonella received the lower doses of antibiotic.
Unbeknownst to the veterinarians, they were creating the perfect environment for bacteria to develop resistance.
Antibiotic resistant strains began to make their first appearance in the beginning of 1963, when a strain developed resistance to sulfonamides and streptomycin.  A year later these bacteria had become resistant to six more antibiotics.

Soon, this multi-resistant strain of Salmonella began to spread to humans. The Enteric reference laboratory received over 500 samples of this same bacterial strain, obtained from human infections. The antibiotics that would normally used in these situations turned out to be useless. This outbreak provided dramatic evidence of the hazards of utilising antibiotics in agriculture. The UK government was forced into action

In 1969, the Swann committee convened to change the way we used antibiotics, so that this kind of outbreak would never be repeated. They recommended that a quasi-non governmental organisation (Quango) be created, which would act to oversee the use of antibiotics for both humans and animals. It was there to increase transparency, to make sure that people knew what antibiotics were being used for, and how much they were used. It would bring together the usage of both veterinary and medical antibiotics under one authority. This co-ordination would enable scientists to better understand the threat of resistance in all of its facets.
 Whilst the committee’s job was to regulate the use of antibiotics in both humans and animals, it ran into a number of problems. But the various different interest groups involved in antibiotics had no compulsion to co-operate. The committee had no real power to control the use of antibiotics, nor did it have any resources to investigate the impact of antibiotic overuse. Eventually it died a quiet death, having never quite lived up to the promise of its birth.

To be Continued Next Tuesday... Thursday...

Anderson E.S. (1968). Drug Resistance in Salmonella Typhimurium and its Implications, BMJ, 3 (5614) 333-339. DOI:

(1981). Death of a quango., BMJ, 282 (6274) 1413-1414. DOI:

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