Warming climate could mean more-virulent fish viruses, study suggests

Rising temperatures may increase the risk that viral pathogens pose to farmed seafood species, according to French research.

Scientists at Université de Montpellier conducted a meta-analysis of studies looking at the effects of temperature on the virulence of cyprinid herpesvirus 3, which affects common carp; herpesvirus OsHV-1, which affects shellfish; and variants of betanodaviruses, which affect a range of finfish and cause the disease viral nervous necrosis.

Their statistical analysis demonstrated that higher temperatures resulted in greater mortalities across all the pathogens. Increases in viral virulence were higher than those seen for bacterial pathogens in warmer waters, though less than in temperate waters.

The work’s focus went on to examine the likely impact of such a connection on aquaculture in low- or middle-income countries (LMICs), where the majority of global farming of aquatic species takes place.

“We have shown that even a relatively small temperature increase of 1° C could lead to an increase in mortalities of 3% to 6%, which, in the context of LMIC aquaculture, could already have a significant impact on food safety,” the authors wrote in the journal Microorganisms.

“This study thus serves to raise awareness of the urgency of developing approaches to make aquaculture in LMICs a sustainable source of protein for rapidly increasing populations.”

Broader risks, but options available

Under climate change, higher temperatures could not only pose a risk of higher viral virulence but also the selection and spread of virulent strains to wild organisms, they suggested.

In order to reduce the risks of emerging infectious diseases and reduce the prophylactic use of antibiotics on fish farms in developing countries, enhanced surveillance methods are needed, they said, which may include the use of environmental DNA methods.

Additionally, approaches such as integrated farming and aquaculture, greater use of vaccines and novel feed supplements can improve future prospects in LMICs. This can move the industry closer to the objectives of the global One Health initiative, they added: continued economic development while considering impacts on animal, human and environmental health.



Read the full report in the journal Microorganisms.