Pr. Bowser et al., EFFECTS OF FISH AGE AND CHALLENGE ROUTE IN EXPERIMENTAL TRANSMISSION OF WALLEYE DERMAL SARCOMA IN WALLEYES BY CELL-FREE TUMOR FILTRATES, Journal of aquatic animal health, 9(4), 1997, pp. 274-278
To determine the effects of fish age at challenge and of challenge rou
te on transmission of walleye dermal sarcoma, 25-week experimental tra
nsmission trials were conducted with cell-free tumor filtrates. Invasi
ve dermal sarcomas developed in walleyes Stizostedion vitreum receivin
g intramuscular injections of tumor filtrate at 6 or 8 weeks posthatch
. Invasive tumors were observed in few (5%) 12-week-old fish and in no
1-year-old fish injected with the tumor filtrates. Fish challenged at
12 weeks after hatching via topical application of inoculum or via or
al gavage also developed walleye dermal sarcoma. Fish challenged via g
avage developed tumors at a variety of locations on the body and fins.
Again, invasive tumors were seen in few of the 12-week-old fish chall
enged by topical application (3%) or gavage (10%). However, several fi
sh challenged via gavage developed severe tumors in the oral cavity an
d on the head near the oral cavity. Fish challenged via topical applic
ation of the inoculum developed tumors that were particularly well dev
eloped at the site of application. The topical contact and oral routes
of experimental transmission of walleye dermal sarcoma are likely to
more closely proximate routes of infection that occur under natural co
nditions than does injection.