ARS | Publication request: INTERACTIONS BETWEEN TRICHODINA SPP. PARASITISM AND STREPTOCOCCUS SPP. INFECTIONS IN CHANNEL CATFISH, ICTALURUS PUNCTATUS

Submitted to: International Aquatic Animal Health Symposium Proceedings
Publication Type: Abstract Only
Publication Acceptance Date: June 20, 2006
Publication Date: August 2, 2006
Citation: Pasnik, D.J., Evans, J.J., Klesius, P.H., Shoemaker, C.A. 2006. Interactions between Trichodina spp. parasitism and Streptococcus spp. infections in channel catfish, Ictalurus punctatus. 5th International Symposium on Aquatic Animal Health Proceedings. San Francisco, CA. September 2-6, 2006. p 211.

Technical Abstract: Streptococcus iniae and S. agalactiae are generally not considered pathogens of channel catfish, Ictalurus punctatus, but concurrent parasitism may increase catfish susceptibility to these streptococcal organisms. Young channel catfish with mild-to-moderate Trichodina spp. parasitism on the gills and skin were experimentally challenged with either S. iniae or S. agalactiae. In order to determine whether the Streptococcus spp. could cause mortality in parasitized catfish, fish were challenged by immersion in 1 ´ 109, 108, 107, 106, or 105 CFU S. iniae or S. agalactiae/mL water and observed for 7 days after challenge. Behavioral changes and mortalities among challenged fish began within 1 day after challenge, and LD50 values in these Trichodina spp.-parasitized fish 7 days after streptococcal challenge were 1.10 x 107 CFU/mL for S. iniae and 3.80 x 107 CFU/mL for S. agalactiae. The survival patterns of parasitized catfish were significantly influenced by S. iniae at the 109 CFU/mL (P < 0.0001) challenge level and by S. agalactiae at the 107 CFU/mL (P < 0.0014) and the 109 CFU/mL (P < 0.0001) challenge levels. These results of the present study demonstrate that both S. iniae and S. agalactiae can cause morbidity and mortality in parasitized young channel catfish.