Commissioned as a surgeon captain in the Royal Army Medical Corps.
Sent to Malta, stationed in the Valetta Hospital. Impressed by Dr. Robert Koch’s recent discovery of the tubercle bacillus, he began to do some investigations on a disease called Malta fever.
Isolated the micrococci following the method of Robert Koch and reported his observations. He continued to study the properties of this organism and proposed the name of Micrococcus melitensis.
The Governor of Natal whom he knew while he was in Malta asked him to investigate a disease called nagana—a sleeping illness affecting cattle in the Northern Zululand.
Bruce inoculated the blood from the infected cattle into healthy horses and dogs; they became acutely ill, and the blood swarmed with hematozoa. The hematozoon was confirmed to be a trypanosome
The Bruces discovered that the mode of transmission of the disease was the tsetse fly.
T. Zammit, one of the Maltese member of the Commission for the Investigation of Mediterranean Fever headed by Bruce, found that goat milk was the disseminating vehicle for Malta fever.
