Chilodonelliasis: Causes, Symptoms & Treatment

Chilodonelliasis is a fish disease caused by species of protozoan genus Chilodonella, mostly free living, parasitic on fish in cold and warm waters.

The article will cover the life cycle of the Chilodonella parasite, the risk factors associated with infection, and the common symptoms experienced by affected individuals.

Additionally, the article will delve into various treatment approaches, including both preventive measures and therapeutic interventions, to effectively manage and control chilodonelliasis in different settings, such as in aquatic environments and among animals.

Chilodonella in fish

Causes of Chilodonelliasis

Parasites can lead to greatest economic losses to aquaculture. Chilodonella is a single-celled ciliate endoparasite. Chilodonelliasis is an important parasitic disease of carp during winter, resulting in great loss to the pond fisheries.

The agent of the disease is a holotrichous ciliate of the family Chlamydodontidae, Chilodonella cyprini, which infect fins and body surface. The two other species which are known to infect the fish are Chilodonella piscicola and Chilodonella hexasticha.

Morphology of Chilodonella

Chilodonella species are distinguished by the number of ciliary rows in the left or right kinetic bands, the morphology of the cytostome, and the size dimensions of mature cells. Chilodonella is comparatively small, with an average length of 60-80 micrometres.

Chilodonella has a ring of cilia around the anterior end of its body, which it uses for locomotion and feeding.

Chilodonella has a long, deep oral groove on one side of its body that extends from the anterior end to the middle of the body.

The oral groove is lined with cilia and used to capture and ingest food particles. Chilodonella has a contractile vacuole that helps maintain osmotic balance by expelling excess water from the cell.

Most Chilodonella species have been characterized based on potentially plastic morphological features. Chilodonella species have nuclear dualism, with an inactive micronucleus and a macronucleus responsible for gene expression.

The macronucleus contains gene-sized chromosomes and divides through amitosis. Chilodonella species have unique features related to their genome structure, including variations in gene copy number between individuals within a population and gene expression levels.

Types of Chilodonella species

Chilodonella is a genus of ciliate parasites that infect freshwater fish worldwide. Some types of Chilodonella species are:

Chilodonella uncinata: Chilodonella uncinata is known as facultatively parasitic ciliate, which can opportunistically parasitize on fish fins and gills and sometimes can cause host mortality. As a model organism, it is always used for genetic studies.

Chilodonella piscicola: Chilodonella piscicola is an ectoparasite common in various fishes.

Chilodonella hexasticha: Chilodonella hexasticha is an important species that is parasitic to fish and found on the body surface, gills and fins of the hosts.

Life Cycle of Chilodonella

Chilodonella is a genus of parasitic ciliates that infect freshwater fish. The life cycle of Chilodonella involves several stages, including trophonts, tomonts, and theronts.

Here is a brief overview of the life cycle of Chilodonella:

Trophont stage: The life cycle of Chilodonella begins when the ciliate attaches itself to the skin or gills of the host fish.

It feeds on the host’s tissue at this stage and grows into a trophont. The trophont has a characteristic shape and can be seen under a microscope.

Tomont stage: As the trophont grows, it becomes too large to remain on the host. It detaches and falls to the bottom of the water body, where it encysts and becomes a tomont. The tomont is a dormant stage of the parasite, which can survive for several days in the environment.

Theront stage: After a few days, the tomont releases numerous theronts into the water. The theronts are the parasite’s infective stage and can swim actively in search of a new host fish.

Re-infection: The theronts attach themselves to a new host fish, and the life cycle begins again. The life cycle of Chilodonella can be completed within 3-4 days under favorable conditions.

However, factors such as temperature, pH, and water quality can affect the duration of each stage of the life cycle.

Geographical distribution of Chilodonella

Chilodonella is a genus of ciliated protozoan parasites that can affect various fish species in both freshwater and marine environments. The distribution of Chilodonella is not limited to any particular geographical region or continent.

They are known to be prevalent in both tropical and temperate regions.
Chilodonella has been reported in many countries worldwide, including the United States, Canada, Australia, Europe, Africa, and Asia.

Chilodonella has been identified in various states in the United States, including California, Colorado, Florida, Illinois, Indiana, Iowa, Michigan, Minnesota, Missouri, Nebraska, New Jersey, Ohio, Pennsylvania, and Texas.

Chilodonella has been reported in Europe in many countries, including the United Kingdom, France, Italy, Spain, Germany, Austria, and Poland.

It has also been seen in freshwater fish in Australia, India, Japan, China, and South Africa.

The prevalence and severity of Chilodonella infections may vary depending on factors such as water quality, temperature, and fish species.

However, the global distribution of this ciliate parasite suggests that it is a significant threat to freshwater fish populations worldwide.

Fish species affected by Chilodonella

Chilodonella hexasticha and Chilodonella piscicola are the most important parasites winch cause disease in various fish.

Some of the fish species that can be affected by Chilodonella include:

  1. Trout
  2. Koi
  3. Salmon
  4. Tilapia
  5. Catfish
  6. Goldfish
  7. Guppies
  8. Swordtails
  9. Discus fish
  10. Angelfish

Diseased fish exhibit skin ulceration, depigmentation, scale loss and excessive mucus production and gill lesions.

Causing signs and symptoms of Chilodonella

Chilodonelliasis is a parasitic disease caused by the ciliate protozoan Chilodonella, which affects a variety of freshwater fish worldwide. Chilodonelliasis in fish occurs due to overcrowding, reduced water flow and very poor environmental conditions.

The main signs and symptoms are:

The mass development of parasites causes a greatly higher production of mucus and disturbance in the respiratory function of the skin.

It includes heavy breathing, excessive secretion of mucus that makes the skin of fish cloudy, clamped fins and loss of appetite. It is seen that the infected fish act more lethargically when a general loss of virility occurs.

Infected fish swim unevenly, come to the water’s surface and try to flip or thrash and rub against pond walls and rocks to relieve itching and irritation and get rid of the parasites.

The fish becomes restless and rises to the upper layers of water. Its entire body is covered with a bluish-white coating, particularly in the head region. It causes localized hyperplasia of the gill epithelium.

The hyperplastic epithelium covers the thin respiratory epithelium, drastically reducing the gill’s respiratory surface.

If left untreated, Chilodonella infections can be fatal to the host organism.

Diagnosis of Chilodonella

Chilodonelliasis can be diagnosed through clinical signs, microscopic examination, and laboratory testing.

A fish health specialist may take skin or gill samples and examine them under a microscope for the presence of Chilodonella parasites.

Microscopic examination and pathological analysis were used in order to detect the presence of C. uncinata.

In some cases, a blood test may be performed to detect the presence of antibodies to the parasite.

For parasitic diagnosis, skin and gills samples are scraped onto slides, dried at room temperature, stained impregnated with AgNO3 and the measurements are gained from photomicrographs.

If chilodonelliasis is suspected, emergency treatment with antiprotozoal medications or other appropriate treatments should be administered to prevent further spread and improve the health of the fish.

Prevention of Chilodonella

Chilodonella is a parasitic protozoan that can cause serious health problems in fish, particularly in aquariums and farms.

The best way to prevent Chilodonella is to maintain good water quality and hygiene in your fish tank or pond.

Here are some steps that can help to prevent Chilodonella:

To maintain water parameters appropriately: We should keep the pH, temperature, and other water parameters within the recommended and suitable range for fish species.

Chilodonella thrives in warm water with low oxygen levels, so the tank should be well-aerated, and the water should be well-circulated.

Quarantine new fish: We must always quarantine them before introducing them to the main tank or pond. The quarantine will help prevent the introduction of any potential diseases or parasites, including Chilodonella.

Regularly clean tank or pond: Regular water changes should be done, and cleaning the tank or pond regularly is necessary to remove any uneaten food, waste, or other debris that can increase the growth of Chilodonella.

Use a UV sterilizer: A UV sterilizer can help to kill or minimize any parasites or pathogens that may be present in the water. We must make sure to properly maintain and change the bulb as needed.

Avoid overfeeding: Overfeeding can lead to an accumulation of organic matter in the tank or pond, which can increase the growth of Chilodonella. We should feed fish only what they need and remove the uneaten food after feeding.

Monitor fish: Keeping a close eye on fish is crucial for any signs of illness or stress, and take action immediately if you notice any issues. Early detection and treatment are significant in preventing the spread of Chilodonella.

Treatment of Chilodonella

For Chilodonella, the following treatments are recommended:

Sodium Chloride- Dip bath 1.5% to 3% for 5 minutes to 1 hour.
Formalin- Dip Bath: 150-250 ppm for 30-60 minutes. Indefinite treatment 15-25 ppm.

Malachite green- Dip treatment: 2.5-5 ppm for 30 seconds; 60 ppm for 10-30 seconds at 20°C. Indefinite treatment: 0.1 ppm in combination with formalin 0.25 ppm malachite green in 125 ppm formalin 2-6 hours.

Potassium Permanganate- Dip treatment: 0.1% for 30-45 seconds; Indefinite treatment: 2-3 ppm.


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