Brucellosis, or undulant fever, is a zoonotic infection caused in humans by organisms of three main species of the genus Brucella: Brucella melitensis, whose natural host is the goat; Brucella abortus, transmitted largely from cattle; and Brucella suis, transmitted from pigs. Clinically; all three types cause similar infections in humans characterized by intermittent waves of fever that may persist for weeks, often with subsequent relapses and prolonged periods of ill health. The causal relationship between organism and disease was first recorded by David Bruce in Malta in 1887; the name Malta fever, which reflects its prevalence among civilians and British troops in that island in the nineteenth century, has been in general use for most of the present century. More recently, other Brucella species have been found to be implicated in the human disease, which has been shown to be widespread around the globe. The terms “Malta fever” and “Mediterranean fever” have been gradually replaced by undulant fever, or brucellosis.

Etiology and Epidemiology

The type of brucellosis originally studied in Malta and described by Bruce in 1887 is caused by B. melitensis. It is transmitted to human beings by consumption of milk from infected goats; occasional cases due to contamination of skin with infective material have also been observed. The mode of transmission became established only during the first decade of the twentieth century. In Malta and elsewhere around the Mediterranean littoral, the disease was endemic rather than epidemic during the nineteenth century, its highest incidence occurring during the summer months.