Environmental Diseases in Aquatic Systems
Environmental diseases affecting aquatic systems and aquatic domestic animals are diverse and influenced by a variety of factors including water quality parameters like salinity, temperature, chlorine/chloramine levels, dissolved gases, and the presence of toxicants such as hydrogen sulfide and heavy metals. These diseases can have significant impacts on a wide range of aquatic species, from fish to invertebrates, and understanding their causes, effects, and treatments is crucial for veterinary professionals working in aquaculture or managing aquatic ecosystems.
Poor water quality is a leading cause of environmentally induced diseases in aquatic animals. Factors such as low dissolved oxygen and high ammonia levels can directly lead to fish mortality. Additionally, the toxicity of other parameters, such as ammonia, can increase with rising pH levels. Temperature plays a critical role as well, where inappropriate temperatures can be linked to fungal diseases in fish, for instance, Fusarium solani infections in bonnethead sharks can be managed by maintaining the water temperature above 80°F (27°C).
Chlorine and chloramine, often used in municipal water treatment, are highly toxic to aquatic organisms. These substances can cause acute and chronic health issues in fish and other aquatic animals, with symptoms ranging from ragged fins and excess mucus to lethargy and mortality at very low concentrations. Effective management involves testing and treating water to remove these compounds before introducing it to aquatic systems.
Hydrogen sulfide, resulting from anoxic conditions in poorly maintained tanks or sediments, and heavy metals like copper and zinc from plumbing or environmental contamination, can also cause significant health problems. Strategies to mitigate these risks include regular tank maintenance, water testing for toxic substances, and the use of specific filtration systems to remove or neutralize these compounds.Dissolved gases, particularly oxygen, are vital for the health of aquatic systems. Fluctuations in oxygen levels, often due to photosynthesis, respiration, and other natural processes, can lead to stress and mortality among aquatic animals.
Monitoring and managing dissolved oxygen levels are essential to prevent hypoxia and ensure the well-being of aquatic life.The U.S. Geological Survey (USGS) and other organizations conduct research and surveillance on aquatic animal health, focusing on the identification of pathogens, understanding their impacts on hosts and ecosystems, and developing mitigation strategies. This work includes the study of diseases in a variety of aquatic environments and is aimed at promoting the health of aquatic ecosystems and the sustainability of aquaculture industries.For veterinary professionals, staying informed about the latest research findings and disease management strategies is crucial. Engaging with scientific literature, attending professional workshops, and collaborating with research institutions can enhance their ability to diagnose, treat, and prevent environmental diseases in aquatic systems effectively.
Important Concepts
Water Quality: The most crucial factor for aquatic animal health; includes parameters like chlorine, dissolved gases, nitrogenous compounds, pH, salinity, and temperature.
Key Environmental Hazards
Chlorine and Chloramine:
Sources: Municipal water, tank disinfectants.
Toxicity: Lethal at concentrations >0.04 mg/L.
Testing: Use kits for free and total chlorine.
Dissolved Gases:
Oxygen: Optimal >5 mg/L, hypoxia causes stress and mortality.
Nitrogen Supersaturation: Causes gas bubble disease.
Nitrogenous Compounds:
Ammonia: Toxic at NH₃ >0.05 mg/L, causes gill damage.
Nitrite: Causes methemoglobinemia ("brown blood disease").
Nitrate: Chronic exposure leads to goiter in elasmobranchs.
pH and Carbonate Compounds:
pH Fluctuations: Influenced by CO₂ levels, affecting aquatic health.
Clinical Changes and Pathological Signs
Hypoxia: Piping behavior, lethargy.
Ammonia Toxicity: Gill damage, neurological signs.
Nitrite Toxicity: Brown gills, hypoxia.
Chlorine Exposure: Ragged fins, excess mucus, cloudy corneas.
Treatment and Management
Chlorine/Chloramine: Dechlorination products, testing water regularly.
Hypoxia: Increase aeration, manage bioload.
Ammonia/Nitrite: Water changes, maintain biofilters.
Nitrogen Supersaturation: Aeration, fix mechanical issues causing gas entry.
pH Imbalance: Manage CO₂ levels, regular monitoring.
Prevention
Regular Testing: Essential for maintaining water quality.
Proper Filtration: Ensures removal of toxicants.
Adequate Aeration: Prevents hypoxia and gas supersaturation.
References:
Environmental Diseases of Aquatic Animals in Aquatic Systems - Exotic and Laboratory Animals. Merck Veterinary Manual.
Diseases of Aquatic Organisms | U.S. Geological Survey.
Aquatic Animal Health and Disease | U.S. Geological Survey
