Susceptibility to columnaris disease in Chinook salmon Oncorhynchus tshawytscha offspring from thiamine-deficient and thiamine-replete females.

Abstract

Nutrient deficiency can cause increased susceptibility to infectious diseases in fish, thus leading to high rates of morbidity and mortality. Thiamine deficiency complex (TDC) in fish can lead to low reproductive success and high mortality rates. Columnaris disease in salmonids, caused by Flavobacterium columnare, has resulted in devastating losses in aquaculture production and wild populations of Pacific salmon particularly associated with climate change and high water temperatures. There is growing awareness that both TDC and columnaris are emerging diseases of salmonids on the west coast of North America; however, it is unknown whether fish that survive from low/intermediate thiamine level eggs will experience latent mortality due to susceptibility to infectious diseases like columnaris. To investigate the interaction of TDC survivors and columnaris, Chinook salmon Oncorhynchus tshawytscha fry reared from either thiamine-deficient (n = 120) or thiamine-replete (n = 120) eggs were challenged with F. columnare using an immersion challenge model of infection, and morbidity/mortality, immune responses, and bacterial load were evaluated. The cumulative mortalities between the treatment groups were significantly different, with the thiamine-deficient, F. columnare-exposed fry ending the challenge with an 80.3% survival rate and the thiamine-replete, F. columnare-exposed fry ending with a 29.03% survival rate (p < 0.0001). Different transcript abundance was detected in gills and spleen of thiamine-deficient and thiamine-replete fry exposed to F. columnare. This study demonstrated that fry reared from eggs low in thiamine have an altered immune response and warrants further studies to better understand interaction with potential pathogens at different life stages.