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Depuration Of Aeromonas Salmonicida By The Freshwater Bivalve Amblema plicata To Prevent The Bacterium’s Transmission To Arctic Char (Salvelinus alpinus) Clifford E.
Starliper USGS, Leetown Science Center, National Fish Health
Research Laboratory, 1700 Leetown Road, Kearneysville, WV 25430 Freshwater
bivalves are very susceptible to environmental and biological factors that
impact their existence. Factors such as dams, construction, siltation and most
recently the unwanted introduction of zebra mussels (Dreissena polymorpha) have resulted in greater than 70% of the
animals native to North America to become listed as threatened, endangered or
of special concern. In 1995, the U.S. Fish and Wildlife Service, with other
partners, initiated conservation efforts; one was a relocation program whereby
animals would be collected and propagated at facilities, including fish
hatcheries, free of their natural threats with the ultimate goal of
reintroduction. With relocation, questions arose regarding the potential to
introduce fish pathogens with the mussels. According to standard protocol,
prior to relocation mussels must undergo a 30-day quarantine to ensure zebra
mussels are not inadvertently spread. The study presented here was done to
determine if quarantine in pathogen-free water would also provide for the
mussels to depurate fish bacterial pathogens they might harbor. There are no
bacterial pathogens known to cause disease to both mussels and fish, therefore,
a model system was developed for study utilizing the bivalve Amblema plicata, the salmonid fish
Arctic char (Salvelinus alpinus) and Aeromonas salmonicida. An artificial epizootic was established by injecting
(i.p.) two groups of Arctic char (60 fish each) with 2.26 X 102 cfu
and 2.26 X 100 cfu, respectively, of viable A. salmonicida per fish.
These fish were placed in a tank with non-injected char, which became infected
via cohabitation. The injected fish died and after the non-injected fish began
to die, 120 A. plicata were placed in
the tank. When the A. plicata had
become carriers of, and potential vectors for A. salmonicida, the animals were transferred to four tanks and
pathogen-free Arctic char were added after 1, 5, 15 and 30 day quarantine
periods. Transmission of A. salmonicida
from the mussels to the “clean” char was then monitored. Infectivity and
transmission to fish and mussels was determined by bacteriological culture. It
was found that a quarantine period in pathogen-free water is effective to
prevent transmission of A. salmonicida,
but effectiveness depends on the length of quarantine.
Return to 25th Annual Eastern Fish Health WorkshopReturn to Leetown Science Center Home Page |