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What Is White Spot Disease?
White spot disease (Ichthyophthirius multifiliis, or Ich) is one of the most common parasitic diseases affecting tropical fish. Unfortunately, it is also a very persistent disease.
White spot is caused when a protozoan attacks and attaches itself to a fish's body, fins, and gills. The white spots that appear look like grains of salt or sugar, but each one is actually a tiny parasite. They are very damaging to the fish and can cause breathing and mobility problems and even death.
Once the parasites are established in an aquarium, it is difficult to control the infection because they reproduce quickly. If not controlled, there is a 100% mortality rate of the fish in the aquarium. White spot is very contagious. When one fish in a tank gets sick, it won't be long before the rest of the fish will start showing symptoms.
However, with careful treatment of the aquarium's fish, water, ornaments, and plants, the disease can be controlled.
Signs, Treatments, and Prevention
Fish swim to surface more often due to difficulty breathing
Antibiotic anti-parasitic medicine specifically for anaerobes
Maintain balanced pH level
Raising tank water temperature
Replace water with water of same temperature
White spots on fins and body
Malachite green dye
Quarantine new fish for two weeks before introduction
Boil new ornaments and stones before introduction
Symptoms of the Disease
In the first phase of the illness, before white spots appear, infected fish will display some or all of the following behavioral changes:
- scratching against stones and decorative objects (the parasite has crossed the protective mucous membrane that covers their skin)
- disordered swimming
- fins folded against the body
When white spots appear, they are about the size of the head of a pin. The first spots will appear on the fins and can be seen in direct light. As the disease progresses, more spots appear on the rest of the fish's body.
If the gills are affected, the fish may swim to the surface more than usual. This is because they are having difficulty breathing. When the peri-orbital tissues and the eye muscles are affected, the eyeball will protrude.
Anti-Parasitics and Other Treatment Methods
The Ich parasite can only be attacked by medications at a very specific point in their life cycle. Medication can work during what is called the "free phase," when the parasite is multiplying. Once the infection phase has begun, medication will not work because the parasites are inside the fish's tissue.
Effective medications include:
- Anti-parasitic medicines: Anti-parasitics should be of the antibiotic type, specifically for anaerobes. This way they don't attack the aerobic de-nitrifying bacteria in the aquarium.
- Malachite green: This is a dye known to effectively combat white spot. A disadvantage to this method is that not all fish can tolerate the treatment.
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Treatment by Changing Water Temperature
It is possible to combat the parasites by accelerating their biological cycle, thereby decreasing the window of exposure opportunity and making medicines more effective. One way to do this is to increase the water temperature. Raising the temperature of tropical aquarium water to 30 degrees Celsius (86 degrees Fahrenheit) and cold water aquarium to 22 degrees Celsius (71.6 degrees Fahrenheit) can be very effective in the early stages of the illness.
What Causes White Spots?
This disease can be caused by:
- Abrupt changes in environmental conditions—for example, if replacement water is at a lower temperature than the temperature of the tank water.
- Introduction of fish that were incubating the disease into a poorly maintained aquarium.
- Introduction of decorations or plants that were carrying cysts of the parasite.
How to Prevent White Spots
White spot disease is easily preventable. Some basic measures to maintain a healthy, parasite-free aquarium include:
- Maintaining optimal levels of pH and temperature for the species that inhabit the aquarium
- Frequent water changes with high-quality water that is the same temperature as the water of the community tank
- Purchasing fish and plants that come from healthy tanks
- Observing a quarantine period of at least two weeks before introducing new fish
- Boiling stones and decorative objects before putting them into the aquarium
- Cleaning new plants with a strong disinfectant
Pathogenesis and Parasite Life Cycle
The parasite that causes white spot disease has a unique biological cycle. In its free phase, it reproduces. In its infecting phase, it feeds off of the tissues of affected fish.
In the infecting phase, the parasite crosses the outer layers of the fish's skin. It has no preference for any particular tissue. It can invade the skin, gills, eyes, or fins.
Once attached to the fish's body, the parasites produce micro-circulatory lesions that cannot be seen with the naked eye. These put the protozoa in contact with the fish's immune system. When the immune system reacts to stop the infection, it attempts to isolate the parasites by encasing them with a layer of epithelial cells. This reaction is known as epithelial hyperplasia, and it causes the white spots.
Once the parasite is big enough, it leaves the fish and descends to the bottom of the tank. Then it multiplies, producing up to 2,000 new parasites.
Duration of the Biological Cycle
The duration of the biological cycle varies with the temperature of the water:
- At 25 degrees: 3 to 6 days.
- At 15 degrees: 10 days.
- At 10 degrees: 25 to 30 days.
This article is accurate and true to the best of the author’s knowledge. It is not meant to substitute for diagnosis, prognosis, treatment, prescription, or formal and individualized advice from a veterinary medical professional. Animals exhibiting signs and symptoms of distress should be seen by a veterinarian immediately.
muscleguy32 on March 13, 2019:
This is good advice. Increasing the temperature works the same way as fever during viral infections like a cold or flu in humans. Our immune system sees the virus best when I it is also free in the blood and outside the cells so a fever increases the speed of the lifecycle. This is why taking painkillers like paracetamol or ibuprophen lengthens a cold or flu since they lower fever.
Just an example of common biological techniques.