Brucellosis

BRUCELLOSIS

Brucellosis, a zoonosis, is a bacterial infection, mainly of cows and goats, but with humans as alternative hosts. The causative organisms, Brucella abortus or Brucella melitensis, are small gram-negative bacilli that are difficult to cultivate, though they can be isolated from blood culture in the acute and sometimes in the chronic phase. Varieties of the causative organisms (e.g., B. canis and B. suis) occur in every part of the world where domesticated and wild cattle or goats are found. Brucellosis responds to treatment with antibiotics such as rifampin and streptomycin.

Humans are usually infected by handling or eating infected animal parts or dairy products. Person-to-person transmission does not occur. Brucellosis is principally an occupational disease of goat and cattle farmers, veterinarians, and abattoir workers. It has always been prevalent in countries around the Mediterranean Sea—where it was formerly called undulant, Mediterranean, or Malta fever—but it can occur wherever there are herds of cattle or goats. It may have an acute or insidious onset following an incubation period of up to two months, and it frequently lingers for many months or even years—sometimes for the remainder of a person's life—with remissions and relapses of low fever, debility, depression, weight loss, joint pains and arthritis, and sometimes enlargement of the spleen and liver.

In 1859, Florence Nightingale, previously a very active woman, returned unwell to England from the Crimean War, where she had established a hospital for sick and injured soldiers. She remained a chronic invalid until her death in 1910, probably suffering from brucellosis.

Besides its debilitating and (rarely) fatal effects on human victims, brucellosis has considerable economic importance because it causes abortion in dairy cattle (hence the name of the commonest variety of the causative organism, which also carries the name of its discoverer, Sir David Bruce).

When brucellosis is diagnosed in a domestic animal herd, segregation of the herd is mandatory. Sometimes the herd is slaughtered and incinerated. Prevention of transmission depends on education of workers, scrupulous hygiene, avoidance of contact with suspected infected animal parts, especially the placenta, and the use of serologic tests to identify infected animals. Preventing infection of occupationally exposed humans also relies mainly on education, personal hygiene, and avoidance of contact with contaminated animals and their carcases. Pasteurization of milk and dairy products protects against infection by the ingestion of such products.

JOHN M. LAST

(SEE ALSO: Veterinary Public Health; Zoonoses)