Major-General Sir David Bruce, KCB, FRS, FRCP, FRSE[1] (29 May 1855 – 27 November 1931) was a Scottish pathologist and microbiologist who made some of the key contributions in tropical medicine.

In 1894, he discovered a protozoan parasite, named Trypanosoma brucei, as the causative pathogen of nagana (animal trypanosomiasis).

[3] In 1886, he was chairman of the Malta Fever Commission that investigated the deadly disease, by which he identified a specific bacterium as the cause.

Later, with his wife, he investigated an outbreak of animal disease called nagana in Zululand and discovered the protozoan parasite responsible for it.

[6] After a brief period as a general practitioner in Reigate, Surrey (1881–83), where he met and married his wife Mary, he entered the Army Medical School in Hampshire at the Royal Victoria Hospital, Netley.

[8] Bruce was appointed assistant professor of pathology at the Army Medical School in Netley in 1889, and served there for five years.

[9] When the Second Boer War broke out in 1899, accompanied by his wife, he ran the field hospital during the Siege of Ladysmith (2 November 1899 until 28 February 1900).

In 1914 he became Commander of the Royal Army Medical College at Millbank, London, the position he held until his retirement as a Major-General in 1919.

From the spleen of corpses, he recovered a bacterium which he referred to as Micrococcus, which he described:When a minute portion taken from one of these [culture] colonies is placed in a drop of sterilized water and examined under a high power [of microscope], innumerable small micrococci are seen.

[12]Bruce's assistant, Surgeon Captain Matthew Louis Hughes named the disease "undulant fever" and the bacterium, Micrococcus melitensis.

It now remains to be seen what effect, if any, this micro-organism has on healthy animals; what are the conditions of temperature, &c., under which it flourishes; where it is to be found; how it gains entrance to its human host; and many other points.

But an analysis of the historical record in 2005 revealed that Themistocles Zammit, one of the members of the commission, was the one who experimentally demonstrated the origin of the bacterium from goat milk.

For the present I shall call it the Haematozoon or Blood Parasite of Fly disease, although in all probability on further knowledge, it will be found to be identical with the haematozoon of Surra, which is called Trypanosoma Evansi or at least a species belonging to that genus...[20]He also made accurate identification characters of the parasite as unique organisms: [Under a microscope] can be seen transparent elongated bodies in active movement, wriggling about like tiny snakes and swimming from corpuscle to corpuscle, which they seem to seize upon and worry.

He found that the tsetse fly (Glossina morsitans), which was common in the region, could carry the live parasites from feeding on the blood of the animals.

Be it at once stated that I have not the slightest belief in the notion popularly prevalent up to the present that the Fly causes the disease by the injection of a poison elaborated by itself, after the manner of the leech, which injects a fluid to prevent the coagulation of the blood, or the snake for the purpose of procuring its prey or for defence, but that at most the Tsetse acts as a carrier of a living virus, an infinitely small parasite, from one animal to another, which entering into the bloodstream of the animal bitten or pricked, there propagates and so gives rise to the disease.

[20]Henry George Plimmer and John Rose Bradford gave the full description of the new parasite in 1899 as Trypanosoma brucei, the name after the discoverer.

[28] Led by George Carmichael Low from the London School of Hygiene and Tropical Medicine, the team included his colleague Aldo Castellani and Cuthbert Christy, a medical officer on duty in Bombay, India.

Twenty-three names of public health and tropical medicine pioneers were chosen to feature on the School building on Keppel Street when it was constructed in 1926.