The Dwarf Gourami Iridovirus is a fatal disease that not only effects Dwarf Gourami but any anabantid fish such as Betta, Gourami and Paradise fish. In the past this disease was noted to be a type of bacterial infection which would case more damage and lead to death, however in more recent years this disease has made itself known even to the most safest and healthiest breeders. Due to the odd nature of this disease, even the most healthiest fish can appear to not have Dwarf Gourami Iridovirus until many months or years later when the disease starts to take hold which makes it extremely hard to stop this disease from spreading.
Due to the nature of this disease, it is extremely hard to tell if a anabantid is infected since the symptoms will not show until months or years through the fish's lifespan. For those fish who are able to carry this disease without it effecting them, it is virtually impossible to know as they will never show any symptoms or signs of infection. Once the disease does start to make itself known on the infected fish, we will see a variety of symptoms which can range from lack of appetite, breathing more heavily through both the mouth and the gills, having a hard time swimming, and most importantly a enlarged spleen which will appear like the fish is bloated or become bloated.
Since many of the symptoms match those of other disease it can be very hard to rule that this is the disease that is truly taking hold of the fish. Once the disease starts to get progressively worse more symptoms will appear which will rule out any other disease and let you know that this is the main culprit. These final symptoms will include the fish being unable to swim to the surface of the water (which is any labyrinth fish is a requirement as they need to get air from both the water through their gills but also through their mouth to fill their lungs), the coloration may appear to be very dull or dark with some grey areas, the fish will lay at an angle or flat on the bottom of the substrate, other bacterial infections may start to show additional symptoms, and lastly the fish will drown due to them being unable to get air from the surface of the water.
Dwarf Gourami Iridovirus is mostly spread to multiple fish populations due to bad breeders who do not take care of the water's parameters or the fish's heath. Since the fish are in contact with each other this disease is allowed to spread to most of the population, before being shipped to the store's tanks where it comes into contact with other fish that might not be infected at all. Even though many stores who sell fish do quarantine any new arrivals, it can be hard to determine which if any fish is infected due to it not showing any symptoms until the fish's immune system becomes weak. Other times even if the new arrivals of Dwarf Gourami are healthy, if there was any traces of a dead or sick fish with this disease it can spread through the water column or if the fish eats any poop that has been leftover from an infected fish. Since Dwarf Gourami are highly wanted fish due to their colors and their personalities, this disease is commonly seen in many breeds of Dwarf Gourami that are sold around the world. A recent study showed that on average 22% of Dwarf Gourami that are shipped from Singapore do indeed carry this disease through tests done on the fish's body.
Treatment and Medication
Unfortunately, there is no known cure to this viral infection although many have stated that using a bacterial and fungus medication does slow down and can prevent death, there is no known documented proof such medicines do truly work. Many have tried to help the infected fish when the disease takes hold by lower the water level in their tank, but due to the fish not being able to eat it will die from starvation. The only way to make sure that you do not get any fish that have this disease is to always buy from a store that is not only reputable, has not had any fish die showing the symptoms listed above, but mainly only gets new fish from trusted and well known breeders.
The best prevention is always to make sure that you are buying from trusted, well known breeders that take care of their stock. Many will make sure that when new shipments are coming in from breeders that they look at all of the fish, sick, dead, or even healthy. Doing so will let you see if any of the fish have any of the symptoms, and if they do you can safety assume that all of the fish might be possibly infected. Sadly since the rate at which this deadly disease effects its inhabitants using quarantine methods (even if you were to do so for a month) the infected fish may never show any symptoms until later in its life cycle.