An overview of parasitic co-infections in tilapia culture

Co-infection with pathogenic microorganisms has substantial harmful effects on susceptible host organisms. It may influence disease progression and severity via synergistic and, in rare cases, antagonistic interactions. Therefore, sick fish are more prone to acquire infections and disseminate them to other neighboring species. Several studies have been conducted regarding the existence and impact of co-infections of bacteria, parasites, fungi, and viruses in different tilapia species. However, the effect and role of parasitic co-infections in farmed tilapia have not been fully addressed and need further investigation. Thus, this review aims to discuss various aspects of pathogenic parasitic and other microbial co-infections, the mode of transmission of major parasites, and the ecological impacts of the parasites affecting farmed tilapia species worldwide. Co-infections have a significant impact in aquaculture and may influence the development and severity of various fish diseases. Nevertheless, information regarding the underlying pathogenic mechanisms and microbial associations that emerge during these co-infections is scarce. In many cases, a prominent pathogen is believed to be critical and is thus recommended for treatment, while the co-infecting agents are ignored, which may worsen the case. This review also highlights other ways to raise awareness of co-infections and assist scientists and fish health inspectors in paying more attention to the natural occurrence of co-infections. This will result in further investigation and the continuous diagnosis of co-infectious events to maximize treatment practices to save tilapia that have been infected with parasites that cause co-infections.