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Temperature effects on immune response and hematological parameters of channel catfish Ictalurus punctatus vaccinated with live theronts of Ichthyophthirius multifiliis

Martins, M. L., Xu, D. H., Shoemaker, C. A., Klesius, P. H.
Fish and Shellfish Immunology 2011 v.31 pp. 774
Ichthyophthirius multifiliis, Ictalurus punctatus, antibodies, antibody formation, catfish, erythrocytes, intraperitoneal injection, monocytes, mortality, protozoal infections, thrombocytes, vaccination, water temperature
This study evaluated the influence of temperature on the immune responses and hematological parameters in channel catfish Ictalurus punctatus immunized via intraperitoneal injection with live theronts of Ichthyophthirius multifiliis. Fish were distributed in 18 aquaria and received 9 treatments: 4 groups of fish were vaccinated with live theronts and maintained at constant temperature 15 , 20 , 25 and 30 ; 3 groups of fish vaccinated and subjected to cycling temperature regime from 15e25 , 20e25 and 20e30 , changed 5 each day; 2 groups of fish were not vaccinated and served as controls at 25 , one with Ich challenge and the other without challenge. Non vaccinated fish and those vaccinated at 15 or 15e25 did not show anti-Ich antibodies in the serum 14 and 21 days post-immunization. The antibody levels were significantly higher from fish vaccinated at 25 , 30 , 20e25 and 20e30 compared to fish at 15 , 20 and 15e25 both 14 and 21 days postimmunization. At constant water temperature, fish vaccinated at 15 showed significantly higher mortality rate (67.8%, P < 0.05) than those vaccinated at 20 , 25 , and 30 (0e10.7% mortalities). At cycling water temperature, fish vaccinated at 15e25 showed significantly higher mortality rate (67.8%) than those vaccinated at 20e25 and 20e30 (P < 0.05). Twenty days after immunization fish vaccinated at 30 and 20e30 showed significant increase in the red blood cells, white blood cells, thrombocytes and monocytes. Six days after challenge with I. multifiliis theronts the fish showed decreased white blood cells, thrombocytes and monocytes. This study suggests that vaccinated catfish were severely impacted by low temperature, either at 15 constant temperature or at 15e25 cycling temperature. The fish showed no anti-Ich antibodies and suffered high mortality similar to non vaccinated control fish.