Introduced Species: 2000
Burreson, E.M., Stokes, N.A., and Friedman, C.S.
Title: Increased virulence in an introduced
pathogen: Haplosporidium nelsoni (MSX) in the eastern
oyster Crassostrea virginica.
Publication: Journal of Aquatic Animal
Health 12(1): 1-8, 2000.
© Taylor & Francis
protistan parasite Haplosporidium nelsoni has caused
extensive mortality in the eastern oyster Crassistrea
virginica along the mid-Atlantic coast of the United States
since 1957. The origin of H. nelsoni has remained
unresolved. Molecular diagnostic tools were used to examine the
hypothesis that a haplosporidian parasite in the Pacific oyster
C. gigas is H. nelsoni. A DNA probe specific for
H. nelsoni reacted positively in in situ hybridizations
with haplosporidian plasmodia from C. gigas collected in
Korea, Japan, and California. Primers that specifically amplify
H. nelsoni DNA in the polymerase chain reaction amplified
product from Californian C. gigas infected with the
haplosporidian parasite. The DNA sequence of the 565-base pair
amplified product was identical to the H. nelsoni sequence
except for a single nucleotide transition, a similarity of 99.8%.
These results are conclusive evidence that the parasite in C.
gigas is H. nelsoni and strongly support previous
speculation that the parasite was introduced into Californian
populations of C. gigas from Japan. Results also support
previous speculation that H. nelsoni was introduced from
the Pacific Ocean to C. virginica on the East Coast of the
United States, likely with known importations of C. gigas.
These results document greatly increased virulence in a naive
host-parasite association and reinforce potential dangers of
intentional, but improper, introductions of exotic marine
organisms for aquaculture or resource restoration.