In Kundiawa in the mid-1960s, the resident medical officer Dr (later Prof) Tim Murrell investigated a disease colloquially named pigbel, or, more crudely, ‘gangrene of the gut’. Here PROF FRANK SHANN (pictured) reviews how this dreadful condition came to be identified and conquered. It turned out to be more complex than simply eating undercooked pig meat, as we in the Simbu thought at the time….
TIM MURRELL MADE VERY IMPORTANT observations about pigbel, but he did not identify the key factors in its pathogenesis.
So pigbel remained the commonest cause of death in highlands children over 2 years of age until some brilliant research done by Greg Lawrence in the 1970s.
Greg found the key factors in the disease to be:
(1) the toxin that causes pigbel is a protein made by the bacterium Clostridium welchii Type C (now called C. perfringens Type C);
(2) the toxin is easily digested by trypsin and chymotrypsin (the enzymes that humans use to digest protein);
(3) people on a low-protein diet have low levels of trypsin and little or no chymotrypsin;
(4) sweet potato contains a trypsin inhibitor.
(5) highlanders often do not cook sweet potato at a temperature high enough to inactivate the trypsin inhibitor;
(6) pigbel occurs when people eat protein (often pig meat) *and* sweet potato containing trypsin inhibitor *and* have C. perfringens present (either in the meal or already in the bowel). In the presence of protein and sweet potato, the C. perfringens Type C grows quickly and produces toxin; the toxin is normally digested by trypsin, but in pigbel this does not occur because of the low trypsin levels and the trypsin inhibitor in the sweet potato.
Greg's work encouraged the development of a Type C vaccine for use in people. The vaccine was made by The Wellcome Laboratories, and was an inactivated form of the toxin that causes the damage in pigbel.
The vaccine caused people to make antibody to the toxin. It not only protected immunised individuals against pigbel but, unexpectedly, eradicated the disease - so that vaccination against pigbel is no longer required in PNG.
I found that pigbel was common in southern China as well as PNG, and it was also common in areas of Vietnam where sweet potato was a staple food.
Greg also discovered why giving antibody to the toxin (antitoxin) did not help patients with pigbel: antitoxin would have had to be given within 12 hours of the protein plus sweet potato meal; by the time patients presented to hospital in PNG, the bowel was already severely damaged and it was too late to give antitoxin.
Of course, Greg relied heavily on Tim Murrell's extensive observations - just as Tim relied on earlier research by vets, and by scientists in Germany (where "pigbel" was common for a few years after the second world war).
From 1968, Frank Shann practised medicine in West New Britain, Rabaul and Goroka (as the paediatrician) 1977-1982. He assisted Greg Lawrence develop the vaccine against pigbel, and also did much research on pneumonia. Prof Shann's PNG protocols now form the basis of World Health organisation guidelines for the management of sick children in all developing countries.
In the course of a colourful professional life, Prof Shann was stabbed by a psychotic patient at Goroka Hospital in 1981 and reviewed child health services in Queensland (including one that led to the building of Queensland Children's Hospital).
He is a Staff Specialist in Intensive Care at the Royal Children’s Hospital in Melbourne and Professor of Critical Care Medicine at the University of Melbourne.