In recent years, there has been an increase in the number of reported cases of viral diseases in fish, due to improved surveillance and diagnostics.
The world of fish is under threat from a variety of viral diseases. Viral diseases of fish are a significant problem in aquaculture and in wild fish populations.
Fish viruses can cause significant mortality in both farmed and wild fish, and can have a major impact on the economics of the aquaculture industry.
Some of these diseases are new and are not well understood, while others have been around for many years.
This article will provide an overview of some of the most common viral diseases of fish. It will also discuss the symptoms, treatment, and prevention of these diseases.
What is Virus
A virus (from the Latin virus meaning toxin or poison). A disease-causing agents made up of minute infectious particles that can be identified only with powerful magnification are called viruses. An individual infectious particle of a pathogen is a virion.
The disease agents of viruses are minute organisms that multiply only in cells. These agents are minute infectious particles, consisting of a nucleic acids core surrounded by a protein coat or capsid.
They have no intracellular structure and cannot control their biochemical processes independently, but they do have the capacity to transcend their host cell by reproducing their genetic function and the potential of mutation.
In their own bodies, they’re characterized by their capacity for reproduction of the characteristic with their own genetic material in living host cells.
Viral Diseases of Fishes
Some of the most common viral diseases of fish include;
| Viral Disease | Causing Agent | Fish Affected |
| Spring Viremia of Carp (SVC) | Spring Viremia of Carp Virus | Cyprinids |
| Channel Catfish Viral Disease (CCVD) | Channel Catfish Virus | Channel Catfish |
| Viral Hemorrhagic Septicemia (VHS) | Viral Hemorrhagic Septicemia Virus | Salmon |
| Infectious Pancreatic Necrosis (IPN) | Infectious Pancreatic Necrosis Virus | Trout |
| Infectious Hematopoietic Necrosis (IHN) | Infectious Hematopoietic Necrosis Virus | Trout |
Spring Viremia of Carps (SVC)
Each spring, a deadly virus threatens North America’s carp population. Spring Viremia of Carps (SVC) is a highly contagious and often fatal disease that affects common carp, koi, and goldfish.
The virus is believed to originate in Russia and spread to Europe and North America through the importation of infected fish.
SVC was first detected in North America in the early 1990s and has since caused widespread die-offs of carp in lakes, ponds, and aquaculture facilities.
The virus attacks the liver, kidney, and spleen of infected fish and causes hemorrhaging within the body cavity. Affected fish often display red or bloody patches on their skin and fins.
Prominent abdominal distention, also called ascites, is a condition in which the abdominal cavity fills with serous fluid. This fluid may be mixed with blood or necrotic material. SVC is a common cause of ascites in fish.
There is no known cure for SVC and infected fish must be destroyed to prevent the spread of the disease.
Channel Catfish Viral Disease (CCVD)
Channel Catfish Viral Disease (CCVD) is a viral disease that can affect channel catfish. The disease is caused by a virus in the family Herpesviridae, and is considered to be one of the most serious diseases of channel catfish.
CCVD can cause death in fish within days of infection, and there is no known cure. The disease is most commonly found in farm-raised fish, but can also occur in wild populations.
Infected fish may show signs of lethargy, anorexia, and ulceration of the skin. In severe cases, the virus can lead to hemorrhaging and death.
Transmission of CCVD can occur through contact with infected fish, or through contact with contaminated water.
There is no known way to prevent the spread of CCVD, and it is considered to be a serious threat to the channel catfish industry.
Viral Hemorrhagic Septicemia (VHS)
Viral Hemorrhagic Septicemia is a viral infectious disease caused by the Viral Hemorrhagic Septicemia Virus (VHSV) in the Rhabdovirus family.
The virus is thought to be spread by contaminated water, and it can infect a wide variety of fish species. VHS can cause bleeding and swelling in the fish, and it can be fatal.
Viral hemorrhagic septicemia (VHS) is a serious viral disease of fish that can affect a wide range of fish species. Viral hemorrhagic septicemia (VHS) is a highly contagious disease that affects both wild and hatchery-raised rainbow trout.
The disease is caused by a virus that is present in freshwater fish, and can cause death within 24 hours of infection.
VHS is characterized by internal and external bleeding, and can lead to death in a very short period of time. The most common signs of VHS are exophthalmia (bulging eyes), ascites (fluid in the abdomen), dark skin, pall gills, anemia, and hemorrhages in the eyes, skin, and gills.
VHS is a highly contagious disease, and once it gets into a fish population it can spread rapidly. Infected fish often die before they show any signs of illness, making it difficult to detect early on.
However, if you see any of the above signs in your fish, it is important to seek veterinary care immediately as there is no known cure for VHS.
Infected fish may show no outward signs of illness, making it difficult to detect the disease in its early stages. VHS can spread quickly through a fish population, and is often fatal to young fish.
In order to prevent the spread of VHS, it is important to practice good biosecurity measures when handling fish.
This includes disinfecting all equipment that comes into contact with fish, and not transporting live fish from one body of water to another.
Infectious Pancreatic Necrosis (IPN)
Infectious Pancreatic Necrosis (IPN) is a viral disease that affects fish. The disease is caused by a virus in the family Birnaviridae and is characterized by necrosis of the pancreas.
Infectious Pancreatic Necrosis (IPN) is an acute, systemic, and usually virulent birnavirus disease of wild and young trout s and certain pacific salmons in costal North America.
Infected fish exhibit loss of appetite, increased body temperatures, and abnormal swimming behavior.
IPN is characterized by severe necrosis of the pancreas and other organs, resulting in a high mortality rate in infected fish. Early signs of IPN include inflammation and necrosis of the exocrine secretary tissue, and fecal pancreatic necrosis
IPN is most commonly spread through contaminated water or by direct contact with infected fish.
There is no known cure for IPN, and infected fish should be immediately removed from the population to prevent the spread of the disease.
Infectious Pancreatic Necrosis is a serious threat to aquaculture and fisheries, as the virus can spread quickly through populations of fish. IPN has been detected in wild fish populations in several countries, including the United States.
Infectious Hematopoietic Necrosis (IHN)
Infectious Hematopoietic Necrosis (IHN) is an acute, systemic, and usually virulent Rhabdoviral disease of wild and young trout s and certain pacific salmons in costal North America.
IHN was first documented in California in 1955, and has since been reported from both freshwater and marine environments in Oregon, Washington, British Columbia, and Alaska.
The virus infects a wide range of fish species, but is most commonly associated with wild and young trout s. IHN is typically fatal to infected fish, with mortality rates exceeding 90% in some cases.
The virus is believed to be transmitted via contaminated water or by direct contact between infected and uninfected fish.
Infectious Hematopoietic Necrosis (IHN) is a deadly fish virus that affects the kidneys, liver, and spleen. The virus is characterized by pale organs, a reddish kidney and spleen, and a distended stomach with milky fluid.
IHN is highly contagious and can be fatal to fish in just a few days. There is no known cure for the virus, so prevention is key.
There is no known cure for IHN, and infected fish must be destroyed to prevent the spread of the disease.
Fishkeepers can help prevent the spread of IHN by quarantine new fish and maintaining clean tanks and equipment.
Transmission of Viral Diseases
The most common way fish catch viral diseases is from other fish. So if you have a sick fish in your tank, it’s important to isolate it from the healthy ones.
Other ways fish can contract viruses include through water contaminated with feces or vomit from an infected fish, or through contact with objects or surfaces that have been in contact with an infected fish.
There is no cure for most viral diseases of fish, so the best thing you can do is try to keep your aquarium clean and free of contaminants, and watch your fish closely for any signs of illness.
If you see any symptoms, take your fish to a veterinarian who specializes in aquatic animals as soon as possible.
References
- Walker, P. J., & Winton, J. R. (2010). Emerging viral diseases of fish and shrimp. Veterinary research, 41(6), 51.
- Pilcher, K. S., & Fryer, J. L. (1980). The viral diseases of fish: A review through 1978: Part 1: Diseases of proven viral etiology. CRC Critical Reviews in Microbiology, 7(4), 287-363.
- Kimura, T., & Yoshimizu, M. (1991). Viral diseases of fish in Japan. Annual Review of Fish Diseases, 1, 67-82.
- Trust, T. J. (1986). Pathogenesis of infectious diseases of fish. Annual Reviews in Microbiology, 40(1), 479-502.
- Plumb, J. A. (2021). Viral diseases of marine fish. In Pathobiology of marine and estuarine organisms (pp. 25-52). CRC Press.
- https://www.azolifesciences.com/?tag=/Virus
- https://en.wikipedia.org/wiki/Portal:Paleozoic/Natural_world_articles/18
- https://eol.org/docs/discover/viruses
- https://draxe.com/nutrition/antiviral-herbs/
