Submitted to: ARS Immunology Workshop
Publication Type: Abstract Only
Publication Acceptance Date: 9/11/2003
Publication Date: 12/2/2003
Citation: Bilodeau, A.L., Small, B.C., Wise, D.J. 2003. Correlations between disease resistance, pathogen levels, and clearance rate in channel catfish. ARS Immunology Workshop. p. 55. Interpretive Summary:
Technical Abstract: Real-time PCR technology was utilized to measure differences in bacterial loads and clearance rates for 6 ESC-susceptible and resistant families of channel catfish during immersion challenge. Significant differences (p < 0.05) in the quantity of bacterial DNA between resistant and susceptible families were evident for both blood and spleen tissue 5 days following exposure to E. ictaluri and mean quantities of bacterial cell equivalents per 100 uL of blood at 5 days post-exposure were 2.84 x 105 ± 143123 for the susceptible families and 496 ± 455 for the resistant families. Significant differences in spleen tissue also occurred on day 12, with fish from the resistant families having higher (p < 0.05) levels of bacteria than fish from the susceptible families. Overall, families that are susceptible to ESC carried higher levels of bacterial DNA in their blood than resistant families. Clearance was evident by day 12 in fish from the susceptible families and bacterial levels continued to decrease throughout the remainder of the trial. However, no significant clearance was evident in fish from the resistant families. This may be due to chronic low levels of infection that did not trigger a clearance response from the immune system. The innate immune system may suppress infection only in resistant families, preventing an acute host-response whereas in susceptible families, acute infection occurs and may secondarily be cleared. Clearance rate does not appear to significantly affect mortality.