Human and animal brucellosis in Jordan between 1996 and 1998: a study

Abstract

Between 1996 and 1998, a total of 2,494 samples of blood from humans and animals were collected and tested for brucellosis. This total included 1,594 samples of animal blood, collected from 1,050 sheep from 20 flocks, and 544 goats from eight herds. The serum samples were tested using the Rose Bengal test, the tube agglutination test, the complement fixation test and an enzyme-linked immunosorbent assay. Moreover, a complete history was compiled from each flock/herd. The rate of abortions in sheep due to brucellosis ranged from 0.5% to 56%, with a mean of 33.2%. The goats had a higher abortion rate. Thirty-four aborted sheep foetuses collected from these 20 flocks were bacteriologically and pathologically examined. A pure culture of Brucella melitensis biotype 3 was isolated from 21 of the aborted foetuses. The human blood samples were collected from two groups: first, from 800 apparently healthy people who were reporting to community hospitals for routine health checks and secondly, from 100 people from groups with a high-risk of contracting brucellosis, such as veterinarians, sheep-herders and laboratory technicians. The Brucella antibody titres for the 900 human serum samples were obtained using the microtitre agglutination test. The cumulative percentage of the serum samples showing a titre reading greater than 1:80 was higher in the at-risk group than among the normal population (7% compared to 4.1%). Although these results were not statistically significant, the higher percentage of positive reactors among the high-risk group may indicate an increased risk factor among professional agricultural and veterinary personnel in Jordan. It was concluded that brucellosis is common in sheep and goats in Jordan, subjecting the human population to high risks. Brucella melitensis Rev. 1 vaccination has been internationally recognised as the key to successfully controlling the disease. All animals in Jordan were repeatedly vaccinated between 1996 and 1998 on a trial basis, using a reduced dose of 1 x 10(5) colony-forming units (CFU). Cumulative data on the annual rate of human cases of brucellosis indicate that fewer people are affected each year. The same is true for the rate of abortions in animals. Such evidence strongly suggests that the vaccination programme has been successful. However, as wild strains of Brucella have also been isolated from vaccinated animals, the authors recommend increasing the amount of vaccine to a full dose of 1 to 2 x 10(9) CFU and vaccinating young female animals between the ages of three and eight months. To avoid brucellosis in humans, people should be educated about the dangers of contact with infected animals and the consumption of raw milk and milk products.