David Bruce, discoverer of brucellosis

Early life

**Sir David Bruce** (1855–1931). Source: London School of Hygiene & Tropical Medicine. CC BY 2.0

Every medical student would be expected to know something about brucellosis, though quite unlikely to ever see a case. He would have to know that the disease in man may be caused by the Brucella of goats, swine, or cows, but apparently not by that of dogs, foxes, or fish. Bright students might also know something about the man who discovered these pesky organisms, Dr. David Bruce, not to be confused with the other Bruce, the victor of Bannockburn, whose exhumed body was lately shown not to have been afflicted by leprosy.

The physician Bruce was born in Melbourne in 1855. His parents had emigrated there during the Australian goldrush, went back to Scotland after five years, and had the boy educated at Stirling. He grew up tall and strong, hoping to become a prize fighter, but was left weak in the chest after a bout of pneumonia and took a job in a warehouse in Manchester. He loved bird watching and considered studying zoology, but later decided to take up medicine at the University of Edinburgh.

It was a little over one hundred years since the cross Samuel Johnson had pontificated that the best roads led from Scotland and that much could be made of a Scotsman if he be caught young. Bruce was twenty-six and went south, to Surrey, to become an assistant to a general practitioner. There he met Mary Elisabeth Steele, the daughter of a doctor, and they fell in love. It was a marriage made in heaven. She was gentle and would always smooth things over when he was difficult and gruff. She also knew laboratory techniques.

Malta

Readers of Cronin’s Citadel may remember that general practice in England in those days was no bonanza. Work was hard, pay low. After two years Bruce decided to join the Army and in 1884 was posted to Malta, then an outpost of the British Empire. The capital Valletta, now a beautiful city with white houses gleaming in the Mediterranean sun, was then an unsanitary port infested by Malta or Undulant fever. This was a disease that resembled typhoid and malaria, and indiscriminately infected British soldiers and native inhabitants.

These were the heady days of bacteriology, when Louis Pasteur and Robert Koch had shown that infectious diseases were caused by bacteria and not by miasmas. They now could identify these bacteria by simply spreading a drop of material on a heated slide, staining it with gentian violet and counterstaining it with safranin. If the microbe took up the gentian violet it was deemed to be positive; if it was stained only by safranin it was gram-negative.

Stimulated by the feats of these pioneers whom he greatly admired, Bruce purchased a microscope and began to examine the spleens, livers, and kidneys from deceased victims of Malta fever. Late in 1886 he saw “enormous numbers” of a gram-negative organism in the spleen from one patient and some more from four others. He grew the organisms in culture and injected seven monkeys, infecting some with the same bacterium as had caused the original disease. By performing culture studies, he fulfilled Koch’s postulates of showing that an organism caused a particular disease, and Bruce sent his findings to the Pasteur Institute in Paris. The cause of Malta fever was thus discovered, but the manner by which it spread had to wait seventeen years.

Thus, David Bruce joined the ranks of the immortals of infectious diseases. After leaving Malta in 1889, he and his wife stopped over in Berlin to learn more techniques from Robert Koch, with whom he established a lifelong relationship. Back in England, he was appointed assistant professor of pathology at the army medical school, but in 1898 was posted to the province of Natal in South Africa.

South Africa

Natal was, at the time, afflicted by a disease of cattle that the natives called nagana. The governor of Natal, having previously served in Malta and remembering Bruce’s work, assigned him to investigate this disease. David Bruce and his wife travelled with a team of bullocks and microscopes into Zululand. Examining the blood of affected cattle, they soon discovered an organism with a long tail that swam like a fish. It was a trypanosome. Remembering the stories from another Scotsman, David Livingstone, about the tsetse fly, he extended his studies for two years, living with his wife in a hut like pioneers, eating the roughest food and shooting their own meat from the big game that surrounded them. He told the natives to drive their cattle to where they would be bitten by the tsetse fly, and on culturing their blood found the trypanosome. It was the first demonstration of the transmission of a protozoal disease by an insect. With the sole assistance of his wife he had been able to prove that the tsetse fly acted as the carrier of the lethal trypanosome. Extending his studies, Bruce also showed that wild antelopes and buffaloes living in tsetse fly infested areas survived, like Maltese goats, by becoming immune to the disease.

After the Boer war, in 1903, David Bruce and his wife went to Uganda to follow up on an earlier suggestion by Dr. Castellani that a deadly illness called Negro lethargy or sleeping sickness, that had killed some 20,000 people, was also transmitted by the tsetse fly. They found trypanosomes in the cerebro-spinal fluid of some patients, and conducted epidemiological studies showing that the disease did not occur in areas where the tsetse fly was absent. Later he conducted studies in other areas of Africa and found that the tsetse fly was also capable of transmitting other forms of trypanosomiasis.

Malta again

**Portrait of Sir David Bruce with Lady Bruce.** Wellcome Collection. (CC BY 4.0)

In 1904, as head of a commission to investigate the source of Malta fever, he returned to Malta and began to suspect that the disease was being spread by infected goats, but was unable to infect them with the disease. Then a member of the commission, Dr. Themistocles Zammit, found that the blood of Maltese goats would react in an agglutination test with the brucellosis organism, and was able to isolate it from their blood. Further proof came when on a ship transporting a herd of goats from Malta to America only those who had drunk goat milk became ill. This was the final link that permitted the public health measure of eliminating goat’s milk from the diet of the British Army and eventually led to pasteurization. Drs. Bruce and Zammit were both honored for their contribution and were featured on a memorial stamp.

Later life

On returning to England, Bruce received many honors and was appointed to many scientific societies and positions. During World War I he investigated the nature of trench fever, caused by the Rickettsia of typhus, and also introduced measures to prevent tetanus occurring in wounded soldiers operated on in the battlefield. He lived until 1931 and died on the very day of his wife’s funeral. He was a great investigator but not an accomplished technician, and it was Lady Bruce who with a microscope had been supreme.

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