The case of SRS

One of the main infectious diseases caused by a facultative intracellular gram-negative bacterium (Piscirickettsia salmonis) is Piscirickettsiosis (Salmonid Rickettsial Septicemia or SRS), responsible for significant economic losses in the salmon industry.

Among the main strategies used by P. salmonis, as a facultative intracellular bacterium, to generate its systemic infection, is to infect, survive and reproduce within cells from the innate immune system with phagocytic capacity, such as macrophages (Mccarthy et al., 2008), overcome the host's immune response (Perez-Stuardo, et al, 2019; Rozas-Serri et al, 2018; Fernández et al, 2006; Labra et al, 2016).

Considering that the control of Piscirickettsiosis (SRS) is a complex task, that optimizing the use of antibiotics in the salmon industry is essential to counteract the development of bacterial resistance, that some of the control strategies used so far do not induce the expected effectiveness at commercial conditions, and that it is necessary to complement the work done by vaccines, nutritional additives and genomic selection, the current challenge continues to be the development of new non-pharmacological solutions to prevent and control Piscirickettsia salmonis infections.

A non-pharmacological alternative that can increase disease resistance and reduce the impact of Piscirickettsiosis in salmonids, by modulating the innate and adaptive immune response, are the highly purified Quillaja saponaria extracts (Paq-Xtract), rich in triterpenoid saponins (Kensil et al, 1991; Marciani, 2018) (Maier et al, 2015) that when administered orally, have shown beneficial effects to increase disease resistance, and improve the use of nutrients in both, aquaculture and terrestrial species (Wang et al, 2016; Ng’ambi et al, 2016; Naknukool et al, 2011; Cheeke et al, 2005; Francis et al, 2005; Ninomiya et al, 1995).