CUSTUS®YRS: Bacteriophages against yersiniosis

The bacteriophages in CUSTUS®YRS are natural enemies of the Yersinia bacteria that causes disease in salmon. The product provides a simple and effective insurance against harmful levels of bacteria in the environment and is mainly used during operations that are associated with a high risk of yersiniosis outbreaks.
(Available only in Norway)

1. CUSTUS in the vaccination programme

When adding CUSTUS®YRS to the anesthetic bath and/or to the post-vaccination tanks, the level of Yersinia ruckeri bacteria quickly drops to undetectable amounts, and disease outbreaks are avoided. The graph illustrates the mortality rate after vaccination. Five receiving tubs were treated with CUSTUS®YRS, one was not.

2. CUSTUS during transportation

Fish held in a wellboat will shed large amounts of bacteria. If the fish are carriers of Yersinia ruckeri, the transport will pose a risk of spreading infection and causing outbreaks.
The graph shows how the general level of bacteria increases the longer the fish are located in the well, while the level of Yersinia ruckeri quickly falls as a result of added CUSTUS®YRS in the wellwater. CUSTUS®YRS significantly reduces the risk of infections during transportation.

3. CUSTUS during delousing

Mechanical delousing in wellboats increases the risk of infection and disease, as the fish experiences stress and intense infection pressure at the same time. In such operations, CUSTUS®YRS can effectively control the infection pressure of Yersinia ruckeri and prevent outbreaks after delousing operations.
The graph shows how CUSTUS®YRS was used in carrying out the fourth delousing operation on a particular group of fish. Yersiniosis outbreaks and high mortality rates were assosiated with the previous two delousing operations, but CUSTUS®YRS ensured low mortality on the fourth and last delousing.

4. CUSTUS for biofilters

The bacteriophages in CUSTUS®YRS control the infection pressure of unwanted Yersinia bacteria without affecting other microflora necessary for the biofilter function. qPCR shows that after only 3 hours, CUSTUS®YRS shuts down the presence of Yersinia ruckeri in the biofilter.
ACD Pharma recommends treating the biofilter with CUSTUS®YRS 1-2 days before starting a new production cycle. This reduces the infection pressure and prevents Yersinia ruckeri from dominating the microflora in the water flow.

Yersinia ruckeri prevalence

Our studies show that the Yersinia ruckeri bacterium is found in almost all Norwegian hatcheries, even in cases where the most commonly used qPCR analysis shows the opposite. A negative qPCR test only means that there are less than 100 Yersinia bacteria in the water sample examinated. When ACD Pharma have examined larger volumes, Yersinia ruckeri has always been found.

The fish will normally handle such low levels of infection pressure without developing disease. Outbreaks occur when the amount of bacteria in the water exceeds the fish´s tolerance for infection, often in connection with situations that causes the fish to feel stress.

Yersinia ruckeri is a freshwater bacterium. However, the fish carry the bacteria with them when transferred to sea, which can cause outbreaks there as well.

Ask Cyril about CUSTUS®YRS

Tel: +47 976 50 815