In 1986 the use of antibiotics in animal feed was banned in Sweden, as one of the first countries in the world. The ban was due to an escalating antibiotic resistance developing in animals, similar to that seen in human antibiotic use. Antibiotics in animal feed are used to prevent for instance post-weaning diarrhoea in piglets. The ban resulted in an increased prevalence of diarrhoea. The suffering this caused and the increased number of deaths due to stress and infectious disease epidemics was disastrous and caused noticeable profit loss.
To come to terms with the problem and possibly find an alternative feed, a joint scientific project was initiated, combining the expertise from veterinary medicine, microbiology, infectious disease and immunology.
Since the 1980's Stefan Lange and Ivar Lönnroth at the Department of Clinical Bacteriology at the Sahlgrenska University Hospital in Gothenburg, Sweden had been studying mice and cholera disease. They were searching for a substance that immunized mice and rats to diarrhoea caused by cholera toxin. It is well known that survivors of cholera, both rats and humans, develop resistance for a long time. Lange and Lönnroth discovered an endogenous system that reacted faster than the immune system, probably an endogenous substance prone to different types of stimulation. The resistance can be triggered by the addition of enterotoxins or by a combination of amino acids and sugars in defined proportions.
Through further research they discovered that a substance produced in the pituitary gland gave resistance to cholera toxin. The protein was named Antisecretory Factor, in short AF (Lange and Lönnroth 1984; Lange et al 1987). This regulatory protein affects the intestinal fluid and electrolyte balance in cell membranes in different organs. AF normalises intestinal fluid secretion, an important factor in the treatment of diarrhoeal disease.