The iridovirus Lymphocystis is found in both freshwater and marine fish. The presence of pink or white lumps anywhere on the fish's body usually causes a change in appearance. Unfortunately, there is no cure, however the condition is self-limiting and does not produce any significant clinical symptoms.
What Is Lymphocystis?
Lymphocystis is a viral infection that affects fish. These viruses are classed as iridoviruses because they have double-stranded DNA structures. They may be found in a variety of animals, including amphibians, invertebrates, and freshwater and marine fish. They are linked to megalocytiviruses, which are iridoviruses as well.
Raised skin nodules are the most common Lymphocystis symptom in freshwater fish. They might appear as a cluster of dozens of nodules or as a few scattered nodules. They can occur on any part of a fish's body, including the fins and mouth. Early infections might appear as a thin layer on the body of the fish. External parasites, bacterial or fungal infections are all possible causes of these symptoms. Differentials for koi should include carp pox (Cyprinid herpesvirus-1) and hikui. This self-limiting sickness has no serious health consequences and just affects the fish's look.
Causes of Lymphocystis
The virus spreads by direct touch and through the water supply. Lymphocystis can persist in the surrounding water for up to a week after being shed from an infected fish. Some fish may be latent carriers, meaning they have the virus but exhibit no symptoms. Because of the virus's extended incubation period, which can last weeks or months, it may not appear until after most quarantine precautions have been completed.
How is Lymphocystis diagnosed?
Your veterinarian will take a skin scrape and examine it under a microscope to diagnose lymphocystis. This is done to eliminate common parasite illnesses like white spot and Ich. Epitheliocystis might look like lymphocystis, however unlike lymphocystis, it can also affect the gills. A veterinary pathologist can also take samples for histological examination. A tiny sample of skin and lesion from your fish will be clipped and packed in formalin by your veterinarian. It might take a few days or weeks to process these samples.
Treatment of Lymphocystis
Lymphocystis has no known therapy. Other stresses in the tank, including as poor water quality, inadequate nutrition, or unsuitable temperatures, can often increase clinical indications of lymphocystis. Your fish's look may be restored if you address any of these concerns. Most fish owners are unconcerned about it because it has no effect on anything other than aesthetics.
How to Prevent Lymphocystis
Even with good quarantine protocols, catching lymphocystis outbreaks is difficult. Even the most well-known fish keepers may have lymphocystis in their tanks and be unaware of it due to the long incubation period and presence of non-symptomatic carriers. Because it has no effect on the fish's overall health, keeping stress levels low in aquarium fish is the greatest way to prevent lymphocystis from spreading.
Is Lymphocystis Contagious to Humans?
Thankfully, lymphocystis is not a zoonotic disease and therefore cannot transfer to humans. There are other viruses within the iridoviridae family which can affect frogs, snakes, and insects.