Meta-analysis examined effect of temperature on mortality rate of aquatic animals infected with pathogenic bacteria commonly found in aquaculture.

April 21, 2020

2 Min Read

Aquaculture — rearing aquatic organisms such as fish and shellfish — plays a vital role in food security in many countries, as it supplies more than half of the aquatic animals people consume worldwide, according to the Institut de Recherche pour le Développement (IRD) in France. Aquaculture is particularly important for developing countries, such as in Asia, which accounts for 90% of global output.

However, in some regions, fish farmers use large quantities of antimicrobials to treat or prevent disease on their farms, but when used inappropriately, antimicrobials are ineffective and may foster the development of resistant bacteria, IRD said.

Researchers from IRD and CIRAD, a French agricultural research and international cooperation organization belonging to the Institute of Evolution Sciences of Montpellier's fish diversity and aquaculture team, examined data from more than 400 scientific articles referring to more than 10,000 bacteria of aquacultural origin from 40 countries. That meta-analysis allowed them to study the effect of temperature on the mortality rate of aquatic animals infected with pathogenic bacteria commonly found in aquaculture, IRD said. The researchers then conducted a systematic review on the abundance of resistant bacteria found on fish farms and calculated a "multi-antibiotic resistance" index for 40 countries.

"Our results show that global warming promotes the development of pathogenic bacteria, hence disease development on fish farms," explained Dr. Rodolphe Gozlan, an IRD specialist in biodiversity-health relations.

Aquatic bacteria are, in effect, temperature sensitive. "Global warming will, therefore, push up mortality rates on fish farms, which is likely to mean increased antibiotic use," IRD post-doctoral student Miriam Reverter added, and as the study showed, antimicrobial resistance is already a reality in several countries among those that are highly vulnerable to climate change.

The study's authors raised an alarm about the consequences of inappropriate antibiotic use for both the sustainability of aquaculture and for human health, IRD said.

"Resistant bacteria in aquaculture can either spread or transmit their resistance genes to non-resistant bacteria that infect humans, thus causing diseases that are difficult to treat in both animals and humans," CIRAD microbiologist Samira Sarter said.

"We urgently need to help producers in the global south find alternatives to treat and prevent disease on fish farms," Gozlan said. "This means encouraging research that makes use of the One Health or EcoHealth approaches, e.g., that is multidisciplinary and multi-sector."

He added that research has shown that certain plants are highly effective for boosting disease immunity in fish, and their use on fish farms could help reduce antibiotic use. Alongside this, researchers are also working to develop more resilient aquaculture systems based on the principles of agroecology with the aim of reducing disease rates.

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