First isolation of Brucella suis biovar 2 in wild boar in Finland

Porcine brucellosis, an infectious disease caused by Brucella suis biovar 1, 2, or 3, is a zoonotic disease of public health and economic concern. The infection generally manifests itself as a reproductive disease potentially leading to abortion in sows and infertility in sows and boars. In Europe, the most common agent of swine brucellosis is B. suis biovar 2 which is endemic in European wild boar and hare populations. These wild animals may spread the infection to domestic pigs causing significant losses in the pig industry.

This study aimed to determine the presence of B. suis bacteria in the wild boar population in Finland by analyzing the samples sent to the Finnish Food Safety Authority Evira as a part of the national monitoring program for African Swine Fever in wild boar.

Specimens sent by hunters contained blood and/or organ samples (spleen, kidney and uterus or testicle) from altogether 133 animals, mainly from the south and south-eastern part of the country. Blood samples were tested for brucella antibodies by serological methods. The organs from antibody test-positive animals were cultured for brucella. Organ samples were also cultured from the animals which could not be tested for brucella antibodies because of lack or poor quality of blood sample.

Blood samples were tested by using three serological methods (Rose Bengal, Complement Fixation and ELISA). For bacteriological examination organ samples were cultivated on selective Farrell's medium and blood agar. Cultures were incubated at 37°C and followed up for 10 days. Presumptive identification was based on Stamp-staining, biochemical tests and PCR assay targeting the IS711. Further identification of PCR positive strains was done at EURL for Brucellosis in France.

Blood samples from five out of 112 (4.5%) wild boars were antibody-positive by all three methods. Four of them originated from male and one from female animals. Organ samples from 37 animals, including the five antibody-positive animals, were cultured. Two out of 37 animals were positive by culture. Both animals were males hunted in the south-eastern part of Finland. All culture-positive animals were also antibody-positive. Both brucella isolates were identified as B. suis biovar 2. Organ samples from other three antibody-positive animals were negative by culture. This may be due to the poor quality of organ samples.

The result of this study shows for the first time that B. suis biovar 2 is also present in wild boar population in Finland.

Disclosure of Interest: None Declared.