CpG inclusion in feed reduces sea lice, Lepeophtheirus salmonis, numbers following re‐infection

Abstract

Lepeophtheirus salmonis infections in Atlantic salmon, Salmo salar, have been characterized by little to no hyperplastic response and a biphasic immune response that results in chronic inflammation with tissue repair as the infection progresses. We hypothesized that CpG administration with prior lice exposure would enhance epithelial inflammatory mechanisms and boost the Atlantic salmon immune response to L. salmonis, leading to greater protection against infection. We administered multiple exposures of L. salmonis to two groups of Atlantic salmon and compared responses against first-time exposed Atlantic salmon. Following re-exposure, CpG fed fish exhibited increased skin expression of interleukin (IL)-1β and IL-12 β compared to control previously exposed (CPE) and control first-time exposed (CFE) animals, respectively. This inflammatory enhancement occurred with significantly lower expression of matrix metalloproteinase-9 (MMP 9), both systemically (spleen) and locally (skin). Reduced MMP 9 expression was a hallmark of the re-infected fish (occurred in both tissues at both times). When significant differences were present in the skin or spleen, the two re-exposed groups showed greater similarity than with the first exposure group. Lice numbers on CpG fed fish were significantly lower than CFE fish at 7 days post-re-infection (dpri), and although they were not significantly different at 17 dpri, the trend of lower lice levels remained. CpG fed fish also showed nearly twofold greater protection than CPE when compared to the CFE group (48.5% vs. 27.0% reductions at 7 dpri and 27.2% vs. 13.1% reductions at 17 dpri, respectively). The enhanced protection of CpG oligodeoxynucleotide administration to previous exposure was consistent across all body surfaces and suggests that CpG can not only enhance innate responses to L. salmonis in Atlantic salmon, but also further stimulate adaptive responses.

Transcriptomic Profiling in Fins of Atlantic Salmon Parasitized with Sea Lice: Evidence for an Early Imbalance Between Chalimus-Induced Immunomodulation and the Host’s Defense Response

“…A compromised host immune system resulting from sea lice infection could be the main cause of detrimental consequences of co-infection [13]. Hence, exploring potential control measures (e.g., modulating host immunity using novel feed formulations [14]) to tackle sea lice infections, and potential secondary infectious outbreaks, requires further research attention. Molecular biomarkers identified herein will be valuable tools in our future endeavors.…”

Sexual maturation and administration of 17β-estradiol and testosterone induce complex gene expression changes in skin and increase resistance of Atlantic salmon to ectoparasite salmon louse

“…Development of biological methods for prevention and mitigation needs better understanding of host pathogen interactions and mechanisms of salmon resistance to the parasite, which may depend on multiple factors including the genetic background, nutrition, properties of skin, ability to heal wounds and the immune system responses (Wagner et al, 2008;Gharbi et al, 2009;Gjerde et al, 2011;Igboeli et al, 2013;Purcell et al, 2013). Teleost skin is a dynamic organ expressing great variability in physical properties, cell types and hormonal systems involved (reviewed by Rakers et al, 2010;Esteban, 2012).…”

Sea lice population and sex differences in P-glycoprotein expression and emamectin benzoate resistance on salmon farms in the Bay of Fundy, New Brunswick, Canada

“…Lepeophtheirus salmonis and Caligus elongatus are the major species of sea lice that infect salmon in Atlantic Canada. 2 Strategies that have been used or are under development for sea lice control in salmon farms include biological predators, 3,4 vaccines, 5 -7 immunostimulation, 8,9 drugs and chemicals, as well as good management practices. The macrocyclic lactones (MLs), which could be administered in-feed, to avoid the disadvantages (i.e.…”