In a study published in the journal Microorganisms, scientists have depicted the effect of global warming on viral infection-related mortality in farmed aquatic animals. The meta-analysis conducted in the study reveals an association between increasing temperature and increasing viral pathogenicity.
Study: Impact of Global Warming on the Severity of Viral Diseases: A Potentially Alarming Threat to Sustainable Aquaculture Worldwide, Image Credit: sercandulger / Shutterstock
Background
Maintaining food security for an ever-increasing human population while reducing the environmental impact of food production has become a major global challenge. In an effort to reduce the negative environmental impact of food production, particularly in terms of land use, the global scientific community has taken significant steps to assess the environmental and health impacts of shifting from meat-based diets to fish- and seafood-based diets.
Aquaculture (farming of aquatic animals and plants) is one of the fast-growing food production sectors in the world. As a result, it plays a substantial role in global food security. However, the rapid emergence and transmission of infectious diseases among animals due to global warming have become a major problem restricting the sustainable development of aquaculture.
In the current study, scientists conducted a meta-analysis of published studies investigating viral infection in farmed aquatic animals. They specifically evaluated whether increased water temperature due to global warming can increase the severity of viral infections and related mortality in farmed aquatic animals.
Study design
The scientists systematically screened peer-reviewed articles describing the mortality of farmed aquatic animals due to viral infections. They selected studies that reported stable specific temperatures for infected aquatic animals. Based on the inclusion criteria, they identified three viral pathogens, namely Ostreid herpesvirus-1 (OsHV-1), Cyprinid herpesvirus 3 (CyHV-3) and Betanodavirus.
Linear regression models were developed to investigate the effect of temperature on the mortality of farmed aquatic animals due to infection by each of these pathogens. Fixed effects included in the models were temperature, life stage, type of infection, and infection dose.
Studies reporting Betanodavirus infections included different fish species and variants of the virus. Thus, host and pathogen taxonomy were included as random effects in the models analyzing the Betanodavirus dataset.   Â
Important observations
A total of 53 studies were included in the meta-analysis to investigate the effect of temperature on aquatic animal mortality due to viral infections by OsHV-1, CyHV-3, or Betanodavirus.
The findings revealed that induction in water temperature leads to higher mortality rates in CyHV-3-infected carps, OsHV-1-infected oysters, and Betanodavirus-infected fish.
Among the model’s fixed effects, the temperature was identified as the only vital predictor of mortality for OsHV-1-infected oysters. For CyHV-3-infected carps, temperature and type of infection were identified as important predictors of mortality.
Model-predicted mortality in farmed aquatic animals
According to the model predictions, a 1 °C increase in water temperature resulted in an induction in mortality of 1.47–8.33% in OsHV-1-infected oysters, 2.55–6.98% in CyHV-3-infected carps, and 2.18–5.37% in Betanodavirus-infected fish.
Considering three types of infections together, the models predicted that an overall increase in water temperature of 1 °C is associated with 3.07–5.70% induction in mortality rates among infected aquatic animals. Â
Study significance
The study finds a positive association between water temperature and viral pathogenicity for OsHV-1, CyHV-3, and Betanodavirus infections.
Since the study includes only three types of infections, the findings cannot be generalized for other pathogens. However, three viruses included in the study are known to infect a wide range of aquatic animals from different habitats in tropical, subtropical, and temperate regions worldwide.
According to the United Nations Intergovernmental Panel on Climate Change (IPCC), the global average temperature is expected to increase by 1.4–5.8 °C by 2100. Considering the findings of this study, global warming of this intensity can put a significant burden on aquaculture sustainability as well as food security. Â
Future research is urgently needed to determine whether the findings of this study can be extrapolated to other relevant aquatic viral infections, as stated by the scientists. Furthermore, it is critical to comprehend the effect of global warming on the dynamics of co-infections.
