In May 1988, 3 newly-introduced Baikal seals (Pusa sibirica) died one
after another from their acute symptoms. Besides, the disease infected 3 other seals that were
originally kept in the same tank as well, and one of those three seals finally died, too. The
others survived and recovered about one month later. All of the dead seals showed severe
congestion of lungs and remarkable hindrance of circulation, and clinical symptoms of
respiratory embarrassment and convulsion. Severe diarrhea and liver disorder were observed in
otherwise, one seal showed green colored eyes. These symptoms and the invalidity of antibiotics
suggested that the cause of the seals, death was virus infection.
To identify the type of virus, we carried out virus neutralization tests
using Canine Distemper Virus (CDV). 5 serum samples of Baikal seals had high antibody titres of
CDV, but samples of Harbour seals showed low titres in contrast.
As a result of the epidemiological survey, we concluded the CDV or closely
related morbillivirus have been brought into the Aquarium from Lake Baikal by new comer
seals.