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

Author
item MARTINS, MAURICIO - University Of Santa Catarina
item Xu, Dehai
item Shoemaker, Craig
item Klesius, Phillip

Submitted to: Fish and Shellfish Immunology
Publication Type: Peer Reviewed Journal
Publication Acceptance Date: 7/9/2011
Publication Date: 11/15/2011
Citation: Martins, M.L., Xu, D., Shoemaker, C.A., Klesius, P.H. 2011. Temperature effects on immune response and hematological parameters of channel catfish Ictalurus punctatus vaccinated with live theronts of Ichthyophthirius multifiliis. Fish and Shellfish Immunology. 31:774-780.

Interpretive Summary: Water temperature is one of the most important factors affecting fish physiology and immunity. Ichthyophthirius multifiliis (Ich), a ciliated protozoan parasite, is responsible for significant losses in cultured fish. Immunization studies have shown protection against this parasite. In rainbow trout vaccinated with live Ich the highest immobilization titer was observed at 20oC. A delayed antibody response to Ich was noted in rainbow trout maintained at low temperature (5oC) compared to those maintained at 12oC and 20oC. Hematological (blood) parameters of fish are also affected by alterations in water temperature. For example, fish transferred to low or high temperatures showed decreased white blood cell count. We hypothesized that fluctuations in water temperature would affect immunization efficacy, immune response and hematology in catfish. This study suggests that vaccinated catfish were severely impacted by low temperature, either at 15oC constant temperature or at 15-25oC cycling temperature. The fish showed no anti-Ich antibodies and suffered high mortality similar to non-vaccinated control fish. The catfish immune response and protection following vaccination with Ich was best at 25 C or which is near the optimal temperature for catfish growth.

Technical Abstract: This study evaluated the influence of temperature on the immune responses and hematological parameters in channel catfish Ictalurus punctatus immunized 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 15oC, 20oC, 25oC and 30oC; 3 groups of fish vaccinated and subjected to cycling temperature regime from15-25oC, 20-25oC and 20-30oC, changed 5oC each day; 2 groups of fish were not vaccinated and served as controls at 25oC, one with Ich challenge and the other without challenge. Non-vaccinated fish and those vaccinated at 15oC or 15-25oC 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 25oC, 30oC, 20-25oC and 20-30oC compared to fish at 15oC, 20oC and 15-25oC both 14 and 21 days post immunization. At constant water temperature, fish vaccinated at 15oC showed significantly higher mortality rate (67.8%, P<0.05) than those vaccinated at 20oC, 25oC, and 30oC (0-10.7% mortalities). At cycling water temperature, fish vaccinated at 15-25oC showed significantly higher mortality rate (67.8%) than those vaccinated at 20-25oC and 20-30oC (P<0.05). Twenty days after immunization fish vaccinated at 30oC and 20-30oC 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 15oC constant temperature or at 15-25 oC cycling temperature. The fish showed no anti-Ich antibodies and suffered high mortality similar to non-vaccinated control fish.