The salmon industry is at a critical juncture, facing the constant challenge of Caligus rogercresseyi , a sea louse that not only harms the fish's health but also represents a multi-million dollar financial loss. Until now, the solution has almost always involved the use of drugs, but as we know, the parasite has become quite resistant, forcing scientists to seek alternatives beyond simply patching up the problem.
In this context, Chilean science, led primarily by the INCAR Center , is making giant strides. The goal is to move from a reactive approach to preventive and adaptive management , where biotechnology and genomics work together to create biological shields that protect fish without the constant need for chemical intervention.
The bet on recombinant vaccines and vitellogenin
One of the most promising approaches has been analyzing the parasite's genome to find its weaknesses. Recently, researchers have focused on vitellogenin (Vtg) , a key protein in the louse. Following computational analysis, experts identified two functional domains, CrVtg-VWF1 and CrVtg-VWF2 , which proved to be ideal candidates for a vaccine.
When these formulations were tested on Atlantic salmon, the results were very revealing. Twenty-one days after infestation, the vaccine based on the CrVtg-VWF2 domain achieved an efficacy of 53,4% , significantly outperforming vaccines using the complete protein. This approach is a breath of fresh air because it demonstrates that targeting specific fragments of the parasite is much more effective at reducing the parasite load.
IPath®: Much more than a head lice vaccine
When discussing innovations, we can't leave out IPath® . This vaccine is a marvel of biotechnological engineering, as it utilizes a chimeric recombinant protein with iron-chelating capabilities . The idea is simple yet brilliant: to deprive the environment of the nutrients that Caligus needs to thrive, creating a hostile environment for the parasite.
The most surprising thing about IPath® is its versatility. In laboratory trials, a reduction in parasite load of nearly 96% was achieved , going from hundreds of lice per fish to barely a dozen. Furthermore, this vaccine has been shown to help fish improve oxygen transport by overexpressing the erythropoietin gene and acts as a booster against bacteria such as Piscirickettsia salmonis and Aeromonas salmonicida.
Licevax2 and the leap towards oral immunization
Administering injectable vaccines is a hassle. It involves handling the fish, which causes them tremendous stress and can lead to preventable deaths. To address this, the Licevax2 project was launched , aiming to implement an oral vaccine integrated directly into the feed.
This works by using BSSD (Bacillus subtilis Spore Surface Display) technology . Essentially, it uses spores of a bacterium that can display the antigen on their surface. The advantage of these spores is that they withstand the high temperatures of the pellet manufacturing process, ensuring the vaccine reaches the fish's stomach intact. This method is not only cheaper to produce, but it also allows for booster doses throughout the production cycle without stressing the animal.
Synergies and the path to the sea
Science has shown that IPath® works well with other tools. In fact, there is a positive synergy when combined with commercial vaccines such as BlueGuard® or Alpha Ject LiVac®. This combination results in a more robust immune response and prevents immune genes from being suppressed during bacterial infections, something that commonly occurs when only commercial products are used.
However, the biggest challenge is taking all of this out of the lab. While the data from tanks is impressive, the reality of the sea is a different story: there are daily waves of infestation and abrupt changes in temperature and oxygen levels. Therefore, the current focus is on validation under real-world farming conditions , seeking industry licenses for these technologies so they can move from prototypes to everyday tools in the cages.
The integration of oral vaccines, the use of iron-chelating proteins, and a deep understanding of the parasite's genome are shaping a new health paradigm. By combining biosecurity, functional nutrition , and advanced vaccination, salmon farming can reduce its dependence on pharmaceuticals and move toward a much more sustainable and environmentally friendly production model.