Unlike vertebrates, fishes have a temperature-dependent metabolism and immune system. Aquarium fishes are equally susceptible to bacterial, fungal, or viral infections just like their sea-water counterparts. This is because of changing oxygen levels, sub-optimal water pH levels, contagion due to diseased fishes etc. Although prophylactic treatments and good management practices can help prevent diseases, vaccination is the best alternative to combat bacterial and fungal diseases and it can increase their survival rates. It is advantageous over antibiotics because a vaccine is a natural biological material that leaves no residue in the environment and is non-toxic. Vaccination also reduces the costs related to morbidity, mortality, and treatment.
There are 3 ways of vaccinating a fish- immersion, intramuscular or oral.
- Immersion: Here, fishes are dipped into antigen solution after dipping into hyperosmotic salt solution (which uptakes intake of antigen). Fishes might feel subjected to stress while using this method but can be used to vaccinate fishes of any size. Sprays can also be used as a direct alternative to this.
- Intraperitoneal/Intramuscular: Fishes of reasonable size can be vaccinated through this. Only fishes of high unit value are injected via this method due to the high costs associated with the process.
- Oral: It is the most common and useful method for fish vaccination. Although a large number of antigens are used and the immunity is not long-lasting as the other two methods, it doesn’t stress the fish and can be used for fish of any size.
Mentioned below are the commonly used vaccines for fishes for prevention against deadly diseases:
Vaccines for Bacterial diseases:
- Warmwater vibriosis
Vaccines for Viral diseases:
- Koi herpesvirus (CyHV-3)
- Infectious pancreatic necrosis (IPN)
- Infectious hematopoietic necrosis (IHNV)
- Viral hemorrhagic septicemia (VHS)
- Salmon pancreatic disease (SPD)
- Grass carp aquareovirus (GCR)
Fishes respond to a vaccine in a similar way like mammals but since they are cold-blooded creatures, their response also depends on the water temperature. Higher the temperature, the faster is the immune response of the fish to the vaccine. Fish vaccines are licensed by the government and closely regulated in the same manner as all other veterinary vaccines to ensure safety, potency, and efficacy.
Vaccination in pet fishes is quite uncommon and it is done only in specific cases like to prevent ulcer disease in Koi and Goldfish. Routine vaccination is not at all recommended.