Howe, G. E., and Stehly, G. R., 1998, Experimental infection of rainbow trout
with Saprolegnia parasitica: Journal of Aquatic Animal Health, v. 10, no. 4,
p. 397-404.

Abstract

A method was developed to experimentally induce saprolegniasis in rainbow
trout Oncorhynchus mykiss. The development of a reliable method to produce
infected fish is essential to efforts to determine the efficacy of various
antifungal treatments. Three methods for inducing saprolegniasis were
evaluated in waters containing known concentrations of Saprolegnia parasitica
zoospores. These methods included application of the following stressors to
fish: (1) abrasion and dewatering, (2) water temperature increase, and (3) a
combination Cif abrasion, dewatering, and temperature increase. Neither
physical abrasion nor temperature increase stress alone was effective for
inducing saprolegniasis. Only 25.9% of fish stressed by abrasion and
dewatering alone became infected. Application of both abrasion and
temperature stress, however, induced saprolegniasis in 77.8% of fish tested.
Most of these fish became infected after 5 d of stress treatments. No fish
became infected or died in the positive control group (not stressed but exposed
to S, parasitica zoospores) or the negative control group (not stressed or
challenged). This method should enable researchers to induce saprolegniasis
in rainbow trout to study its pathogenesis or to test the efficacy of antifungal
treatments. In conducting efficacy studies, it is important that therapeutic
treatments begin promptly after the first signs of saprolegniasis are observed
because the disease can progress very quickly and often results in mortality.

Keywords

Winter saprolegniosis, channel catfish