Streptococcosis: Implications for Aquaculture

Siow Foong Chang*
MSD Animal Health Innovation
1 Perahu road
Singapore 718847
Email: siow.foong.chang@merck.com

Global tilapia production has increased rapidly and tilapia is now the second most farmed fish in the world. This is supported by a strong demand for a neutral tasting whitefish. The international trade in tilapia and tilapia products are growing rapidly.

Disease is a key challenge in tilapia production, and intensification of tilapia farming very often impacts on the health status of production systems. In particular, streptococcosis in cultured tilapia is becoming increasingly common. The main etiological agents are Streptococcus iniae and Streptococcus agalactiae. These pathogens do not just impact on production, but have implications for food safety and market access.

Preventive veterinary medicine is central to most other protein production systems. Core to such a program are vaccines, biosecurity and a deep understanding of the interactions between pathogens, their hosts and the production system.  

It is no different with the approach to control streptococcosis in fish. We have found that control measures targeted at these pathogens need to take into account different bacteria biotypes and their interaction with the hosts, production systems and geographical regions.

Different S. agalactiae biotypes will require a different approach to control. Control measures also need to take into consideration the presence of other diseases in the same production system and affecting fish at various production stages. Integrating understanding of diseases and production will allow a bespoke approach to disease control programmes.

Farms also need to take into account increasing market and regulatory demand for a sustainably farmed, safe and wholesome protein.

One key area of increasing concern is food safety. Streptococcosis is a zoonotic agent with known food borne outbreaks associated with consumption of fish. At the same time, the ease of application of antimicrobials to keep diseases at bay can also lead to drug residue and environmental issues.

A potential focus area for future risk mitigation is antimicrobial resistance (AMR). There is growing international regulatory awareness and pressure to carry out risk assessments, surveillance and potential trade regulations to reduce the risk of AMR. This is an area where many farms are neither aware nor prepared.  

The challenge for farmers is to integrate preventive control programmes into their production system and derive additional value from these investments, by maintaining relevance to future regulatory and market access demands.