Effects of chlorantraniliprole insecticide on innate immune response of silver catfish (Rhamdia quelen) naturally infected with Aeromonas hydrophila.

It is well documented today that pesticides, used in crop production, may modulate the immune system of healthy fish. However, there is still only limited information regarding the effects of these anthropogenic stressors in conjunction with natural stressors (pathogens), on the innate immune responses of freshwater fish. Thus, the aim of this investigation was to compare the innate immune response of two groups of fish (Rhamdia quelen), naturally infected with Aeromonas hydrophila, exposed and unexposed to a non-lethal concentration of chlorantraniliprole (CAP) insecticide (0.0 and 1.3 μg/L/24 h). Unhealthy fish exposed to CAP showed significant higher total leukocyte counts and neutrophils percentage compared to non-exposed infected fish). However, the monocytes and eosinophils percentage significantly decreased in fish exposed to CAP. Furthermore, lysozyme activity values measured in plasma, skin mucus, gill and intestine significantly reduced in fish exposed to CAP. The CAP-induced immunomodulation may interfere on the ability of the animal to heal or fight the infection, and possible contribute to the spread of bacterial infection in fish production or environment.