6.8 Summary

This chapter has provided a short introduction to infectious diseases in fish alongside examples of organisms which might cause these diseases. A summary of the major points covered in this chapter is provided below:

• Approximately half of Earth’s animal life comprises microbes, the majority of which are non-pathogenic in our daily lives.
• Infectious disease theories acknowledge that in any community, a percentage of healthy and normal individuals can harbor potentially pathogenic microbes without symptoms, lesions, or economic impact.
• René Dubos’ insights into the germ theory highlight that exposure to a disease agent does not guarantee infection; the susceptibility of the host is influenced by environmental and microbial changes as well.
• Deficiencies in the management of livestock (i.e., husbandry practices, water quality, nutrition, and biosecurity) can create opportunities for disease outbreaks to occur.
• Starting with a comprehensive history from the owner, the veterinary clinician can establish substantial information about how long, how fast, and how severe a disease has been, aiding in the diagnosis and treatment process.
• Gram staining, a laboratory test that helps distinguish between Gram-positive and Gram-negative bacteria under a microscope, is one method used to identify the type of bacterial pathogens present in a population, though it cannot provide a definitive diagnosis on its own.
• Understanding the complexities of disease outbreaks and the factors influencing them is crucial for effective disease management in aquaculture.