Objective—To determine the prevalence of
Streptococcus iniae in tilapia (Oreochromis spp),
hybrid striped bass (Morone chrysops × M saxatilis),
and channel catfish (Ictalurus punctatus) on commercial
fish farms in the United States.
Animals—1,543 fish (970 tilapia, 415 hybrid striped
bass, and 158 channel catfish).
Procedures—The dry-swab technique was used for
collection of specimens for streptococcal isolation.
Specimens were shipped by overnight delivery and
processed by use of standard bacteriologic techniques.
Results—Streptococcus iniae was not isolated from
market-size channel catfish. Prevalence in tilapia and
hybrid striped bass was 37 of 970 (3.81%) and 30 of
415 (7.23%), respectively. Prevalence by farm ranged
from 0.0 to 27.4% for tilapia and 0.0 to 21.6% for
hybrid striped bass. In tilapia, prevalence was lowest
in market-size and nursery fish (4 of 239 [1.67%] and
3 of 339 [0.88%], respectively), with an increase in
prevalence for fish in the grow-out stage (30 of 337
[7.96%]). For hybrid striped bass, prevalence was
lowest in nursery and market-size fish (3 of 96
[3.12%] and 1 of 47 [2.12%], respectively) and highest
in fish in the grow-out stage (26 of 272 [9.56%]).
Prevalence in market-size tilapia and hybrid striped
bass was 5 of 286 (1.75%).
Conclusions and Clinical Relevance—Results of
this study do not support the contention that S iniae
is a serious public health threat associated with commercially
raised fish; rather, it represents a limited risk
for older or immunocompromised people who incur
puncture wounds while handling and preparing fish.
(Am J Vet Res 2001;62:174–177)