Serological,Bacteriological, and Molecular Diagnosis of Brucellosis in Domestic Animals in Croatia

Aim

To present the surveillance data on Brucella melitensis, B. suis, and B. ovis infection in cattle, sheep, goats, and swine in Croatia obtained in 2008 by serological, bacteriological, and molecular methods for diagnostics of brucellosis in domestic animals.

Methods

We serologically tested 42 785 cattle serums, 22 686 sheep and goat serums, and 28 520 swine serums using the Rose Bengal test, complement fixation test, and various immunosorbent assays. We also tested 10 173 ram blood samples for B. ovis infection using the complement fixation test. Bacteriological examination was conducted on 214 samples collected from 34 serologically positive animals. Different molecular methods were employed in the identification and typing of 20 isolates from the samples.

Results

B. melitensis biovar (bv.) 3 was confirmed with different identification methods in 2 flocks in 2 Croatian counties and B. suis bv. 2 in 3 herds in 3 counties. B. melitensis in cows was confirmed for the first time in Croatia. Infection with B. ovis was serologically confirmed in 202 rams in 12 counties.

Conclusions

In 2008, the size of the brucellosis-affected area in Croatia and the efficiency of detection and prevention of brucellosis in sheep, goats, and swine were satisfactory. Infection with B. melitensis in cattle was confirmed for the first time and possible links for infection in humans were detected. More efficient measures for suppression and control of ovine epididymitis are required and a new strategy may be necessary for complete eradication of this disease.Brucellosis is a chronic infectious disease caused by bacteria of the genus Brucella that affects animals and humans. Each species of Brucella has their preferred host: B. abortus infects cattle, B. metitensis sheep and goats, B. suis swine, B. canis dogs, and B. ovis sheep, although they can also infect other animals (1). Brucellosis in sheep and goats is endemic in the Mediterranean region but is spread throughout Asia, Africa, and Central and South America (2,3). Along with tuberculosis and rabies, brucellosis is the most important bacterial zoonosis and remains an important public health and economic concern.With the exception of B. ovis and B. neotomae, all Brucella species can cause infections in humans. New Brucella species pathogenic for humans – B. ceti and B. pinnipedialis – have recently been discovered in marine mammals (4). Infection is transmitted to humans though direct contact with the infected animals or by consuming infected milk or fresh cheese (1).In Croatia, brucellosis in domestic animals is controlled in accordance with the annual order issued by the Ministry of Agriculture. Serological blood examination of all male breeding animals is mandatory twice per year, and all cases of abortion must be reported and tested for brucellosis. On large cattle and pig farms, 20% of breeding animals must be tested annually. Castration of seropositive rams without the obligation of bacteriological testing is required as an eradication measure for B. ovis infection.Bovine brucellosis (B. abortus) was eradicated in Croatia in 1964, while brucellosis in sheep and goats has occurred sporadically in the recent years, limited to 1-2 sheep flocks per year. All of the occurrences have resulted from epizooty originating in the neighboring country of Bosnia and Herzegovina (BH) (5,6). Swine brucellosis has been detected in swine and wild boars during regular controls (7,8) and B. suis isolates were determined as biovars (bv.) 1, 2, or 3 (7-11).B. ovis in rams and sheep causes either clinical or subclinical disease and is not pathogenic for humans (12). According to simulation models, B. ovis infection causes significant economic losses in flocks with no control measures, but there is no exact confirmation of the extent of such losses (13,14). Eradication is possible, but requires considerable resources.The aim of this study was to determine the effectiveness of the existing programs for diagnosis and control of brucellosis in domestic animals in order to prevent transmission of disease to humans and to reduce economic losses in animal production. This article describes the spread of brucellosis caused by B. melitensis, B. suis, and B. ovis in cattle, sheep, goats, and swine in the Republic of Croatia in 2008, as determined using different diagnostic methods.