Abstract
Simple SummaryAlthough the intensification of fish production allows for better economic results, it also increases the risk of infections depending on fish density. Frequently occurring co-infections are difficult to diagnose because the isolated microorganisms are opportunistic, and their role in the development of disease is uncertain. The infectious pancreatic necrosis virus (IPNV) and bacteria Yersinia ruckeri are widespread pathogens of rainbow trout, causing economic losses in fish culture. The influence of the studied pathogens on non-specific immunity in both single and co-infections was determined. Results imply that IPNV infection may contribute to secondary bacterial infections.Background: The IPNV is one of the most common viral pathogens of rainbow trout (Oncorhynchus mykiss), while Y. ruckeri infections are widespread among bacterial agents. The current study aimed to determine the influence of IPNV and Y. ruckeri co-infection on a non-specific immune response. Methods: Two experiments were conducted. The first experiment determined the changes in non-specific immunity parameters upon the simultaneous occurrence of IPNV and Y. ruckeri infection. In the second experiment, infection with the IPNV was performed two weeks before Y. ruckeri infection. The level of total protein, gamma globulins, the activity of lysozyme and ceruloplasmin, as well as the metabolic activity and potential killing activity of phagocytes were measured: 0, 24 h, 72 h, 7 days, 14 days, and 21 days after co-infection. Results: A differentiated effect on the parameters of the non-specific immune response was shown between single infections with the IPNV and Y. ruckeri as well as co-infection with these pathogens. Conclusions: The immune response in the course of a co-infection depended on the time between infections. IPNV infection causes lysozyme activity suppression, which may lead to secondary bacterial infections.
Highlights
Due to the growing human population, the demand for wholesome food products, including fish, is increasing and aquaculture has become one of the fastest-growing sectors of food production
Rainbow trout fry with an average body weight of 60–80 g were brought from a fishing farm with known epizootic status concerning the occurrence of infectious pancreatic necrosis virus (IPNV) and Y. ruckeri
In the case of fish diseases, studies that would determine the correlation between infection with viral and bacterial pathogens are limited, and there are no studies that would determine whether IPNV infection affects the pathogenicity of Y. ruckeri
Summary
Due to the growing human population, the demand for wholesome food products, including fish, is increasing and aquaculture has become one of the fastest-growing sectors of food production. The predisposing factors include changes in the physicochemical parameters of water, breeding procedures such as fish sorting, and excessive density in tanks. This is important because the overcrowding of fish causes stress that can lead to disease in asymptomatic vectors, and a large group of fish promotes the spread of pathogens. The first experiment determined the changes in non-specific immunity parameters upon the simultaneous occurrence of IPNV and Y. ruckeri infection. Results: A differentiated effect on the parameters of the non-specific immune response was shown between single infections with the IPNV and Y. ruckeri as well as co-infection with these pathogens. IPNV infection causes lysozyme activity suppression, which may lead to secondary bacterial infections
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