Detection of serum antibodies to Brucella in Russian aquatic mammals

A serologic survey of Brucella infection was performed in Caspian seals (Pusa caspica, n=71), Baikal seals (P. sibirica, n=7), ringed seals (P. hispida hispida, n=6), and beluga whales (Delphinapterus leucas, n=4) inhabiting Russian waters, by enzyme-linked immunosorbent assay (ELISA) using Brucella abortus and B. canis as antigens. The sera of 4 Caspian seals (4%) tested positive for B. abortus. The same sera samples demonstrated weaker yet detectable affinity for B. canis antigens. Several discrete bands against B. abortus and B. canis antigens were detected on Western blot analysis of the ELISA-positive seal sera; the bands against B. canis were weaker than those against B. abortus. The sera of 3 beluga whales (75%) were positive for B. abortus antigens but showed no binding to B. canis antigens in the ELISA. The positive whale sera showed a strong band appearance only against B. abortus antigens in the Western blot analysis. Many detected bands were discrete, while some of them had a smeared appearance. The present results indicate that Brucella infection occurred in Caspian seals and beluga whales inhabiting Russian waters, and that the Brucella strains infecting the seals and the whales were antigenetically distinct.