Brucellosis in the Americas

16 World Health • 51 st Year, No. 4, July-August 1998

Brucellosis in the Americas

Primo Arambulo

Workers preparing food of animal origin in South America. Slaughterhouse workers are at particular risk of contracting zoonoses such as brucellosis.

Photo WHO/PAHO/C. Gaggero

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Brucei'la melitensis is the most likely to cause serious illness in humans. Next comes B. suis, then B. abortus, then B. canis. The main mode of transmission of brucellosis to humans is consumption of conta- minated milk and cheese.

Brucellosis spreads through the population where contaminated food is sold. The different stages of the disease are difficult to diagnose, and in areas where brucellosis (particu- larly the bovine type) recurs regu- larly in animals, infection is often transmitted in asymptomatic form.

The main countries in the Americas affected by this foodborne disease are Argentina, Mexico and Peru. In 1995, a total of2699 cases of human brncellosis were reported in Mexico. In 1996, there were 3362 cases: an increase of approximately 20%. The Mexican States most affected are Guanajuato, Coahuila,

Durango and Nueva Leon.

In Argentina, 496 cases of human brucellosis were reported in 1995 and the number increased further in 1996, to stand at 565. The provinces most affected are those with the largest goat population: Catarnarca, Mendoza, Salta and San Luis.

In Peru, brucellosis recurs regu- larly in the departments of Ancash, Lima, lea and El Callao, where there are epidemic outbreaks. Vaccination of goats has brought about a consid- erable reduction in cases among humans, but vaccination programmes which do not reach most of the target animal population or are not carried out every year lead to new outbreaks.

In countries where the disease in animals has been brought under control, it can reappear sporadically in individuals who acquire the infec- tion from abroad, usually by consum- ing illegally imported and unsafe animal products. It also occurs from time to time in occupationally ex-

posed groups such as farmers, vet- erinarians and laboratory and slaughterhouse workers.

In North America, efforts to eradicate brucellosis have been successful in Canada which has been free of the disease since 1985. In the United States, 141 herds were found to be infected in 1996, of which only 45 were still under quarantine at the end of that year. The United States hopes to eradicate the disease by the end of 1998, but this might not be possible because of the difficulty of vaccinating bison, which live in the wild. Annual incidence of brucel- losis in humans in the United States has been below l 00 cases since 1996. •

Dr Primo Arambulo is Coordinator of the Veterinary Public Health programme at WHO's Regional Office for the Americas/Pan American Sanitary Bureau, 525, 23rd Street NW, Washington, DC 20037, USA