Ichthyobodo necator
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| Henneguy , 1883 |
Ichthyobodo necator , formerly Costia necatrix , is a parasite that causes the disease known as Costia or Ichthyobodo in fish. In many cases, the parasite or disease is still referred to by the old name. It is a heterotrophic flagellate (flagellate) from the realm of the protozoa, only 10 to 20 μm in size,and is one of the opaque skin.
Appearance and way of life
Ichthyobodo is one of the smallest parasites and can only be seen with a microscope due to its small size. At a magnification of around 400 times, Ichthyobodo necator can be accurately diagnosed. However, its jerky and rotating movements are already noticeable from a magnification of 100 times.
The body shape of Ichthyobodo necator is oval shaped like an almond. By means of a flagellum , at the end of which there is a cytoplasmic process, it attaches to the outer skin epithelium of the fish host. Ichthyobodo necator has a macronucleus and two flagella, one of which is used to move from host to host and the other to anchor itself to the host. Here the parasite feeds by grazing on the cell tissue and damages it so severely that the host cells die off due to the ongoing loss of cell tissue and the parasite then attacks a new, healthy cell . Ichthyobodo necator needs a host to survive and then reproduce through longitudinal division. If it does not find a host within a period of one to two hours during its swarming phase in the free water, looking for a fish host, the parasite dies. Ichthyobodo necator is able to form cysts that keep it from drying out and thus allow it to survive even longer periods of drought. The parasite then lingers within these cysts until the circumstances return to its preferred living conditions.
Ichthyobodo necator is highly temperature dependent and reaches its highest rate of reproduction in a range between 10 and 25 ° C. Ichthyobodo necator is not viable above a temperature of 28 ° C. Below 10 ° C it protects itself through the formation of cysts. It is transmitted through direct contact or through its ability to swim freely in the water to find a new host.
infection
Since it is one of the parasites that are permanently found on fish, it feeds mostly on the dead cells of the fish. At this point in time, it does not pose a threat to the infected, healthy fish, as it can cope very well with the parasite due to its immune system and Ichthyobodo necator only has a very short life cycle. Carp or carp species can develop resistance to this parasite in the course of their life , but are very susceptible to ichthyobodo when they are young. Ichthyobodo necator is, however, a classic parasite of weakness that just waits for its host to be weakened by other circumstances. This moment triggers a mass infestation which, undetected or untreated, leads to a very high mortality rate. Ichthyobodo necator is extremely dangerous for young fish or fry and inevitably leads to death in the offspring.
Course of disease
The outbreak of a disease that is triggered by a mass infestation of Ichthyobodo necator only occurs in the case of overstocking and generally poor water parameters associated with the overstocking.
The first signs of an infestation with this parasite are a greasy, gray coating on the skin surface of the fish that can even become cloudy. As the fish progresses, the mucus layer is destroyed and the mucous membrane becomes detached in a noticeable manner. Once the upper epithelial layer has been destroyed, the parasite now penetrates deeper tissue layers, followed by proliferating and bleeding ulcers through to holes caused by the bacterium Aeromonas hydrophilia , which Ichthyobodo necator also carries on its biting tools. At the same time, the wounds are infected and colonized by the water mold Saprolegnia . After the bacteria have invaded the fish's bloodstream, renal insufficiency or failure occurs, which no longer enables the fish to correct its osmotic balance and inevitably ends in death. In addition, Ichthyobodo necator attacks the gill tissue of the host and causes gill necrosis through its feeding activity. Ichthyobodo necator often occurs in connection with Chilodonella piscicola (Zacharias, 1894), which is also a real parasite of weakness.
treatment
Ichthyobodo necator and Ichtyobodo pyriformis are the most common representatives of the group of these parasites that occur on fish. A treatment is carried out with an increase in temperature to at least 30 degrees Celsius and the simultaneous addition of oxygen over a period of two days, which safely kills the parasite. However, temperature increases in these areas are only advisable for warm water fish. If no temperature increase is possible, a spa treatment with acriflavin (trypaflavin) is also an option . As a sole drug, this remedy is only rarely used because many pathogens have already developed resistance. As a rule, acriflavine is offered in medicinal products as a combined preparation in the relevant specialist trade as an over-the-counter drug. As a single active ingredient, acriflavine can only be obtained from a pharmacy.
Acriflavine can:
- color the water and plastic objects very yellow
- Damage and / or kill aquatic plants
- cause sterility in certain species of fish such as guppies
- Kill filter bacteria and make repopulation necessary
Iodine-free salt additions of around 2% salinity can also be considered in the initial stage, but only if there is no damage to the deeper connective tissue or muscles. Additional oxygen is also urgently required here. However, a reliable diagnosis and the resulting treatment must be guaranteed by a veterinarian or a veterinary medical examination center (for farmed fish).
Farm fish
In the case of commercial fish, the very small amount of drugs permitted for food-producing animals is a major problem for local pond management. The pharmaceutical industry shies away from new developments for the treatment of parasitic diseases due to the high development costs and the low profit margins within the pond industry. Here there is the possibility to switch to lignite humic substances, which have anti- inflammatory , mucous membrane-covering, astringent , toxin-binding , antibacterial and virucidal effects. Furthermore, lignite HS preparations are not known to have any carcinogenic (carcinogenic), mutagenic , embryotoxic , foetotoxic or allergenic properties. No toxic effects can be determined when applied via the feed . The use of BBB should also not cause resistance to develop (including Eichhorn et al. 1982; Kühnert et al. 1989; Lange et al. 1996; Ziechmann 1996). An exact diagnosis and the associated use of medication can, however, only be carried out by a veterinarian or a corresponding veterinary medical examination center.
Web links
- Study from the Institute for Parasitology at the University of Leipzig
- Ectoparasitic Protozoa (Flagellates and Ciliates)
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- Gerald Bassleer: Illustrated atlas of fish diseases in freshwater aquariums . Naturbuch Verlag, Augsburg 1996, ISBN 3-7888-0372-X
- Gerald Bassleer: The new picture atlas of fish diseases in tropical ornamental fish and pond fish . Naturbuch Verlag, Augsburg
- Wilhelm Schäperclaus, Hugo Kulow, Kurt Schreckenbach: Textbook of fish diseases . 5th edition. Akademie-Verlag, 1990, ISBN 3-055-00190-7
- Heinz-Hermann Reichenbach-Klinke: Diseases and damage to fish . 2nd, completely revised edition. Fischer, Stuttgart 1980, ISBN 3-437-30300-7
- Erwin Amlacher: Pocket book of fish diseases: Basics of fish pathology ; with 19 tab. 6., revised. Edition Fischer, Jena, Stuttgart 1992, ISBN 3-334-00350-7