Trichodina is a body parasite that is commonly found on carp, and it has the potential to cause secondary health issues and in severe infestations it can cause death. It can be a bit of a slow-burning issue, often going undetected until it starts to cause issues.
This blog information is taken from our Issue 19 magazine article, ‘Trichodina: How To Identify And Keep Them At Bay.’ If you’d like to read the full article then check out our issue 19 magazine. It’s available in the back issues section of our online shop.
Trichodina (Trichodinid) are parasites that are commonly found in many fish species around the world and there is a freshwater family that specifically targets and thrives on our Koi. There are more than 150 Trichodinid species, they are a very widely populated parasite and have a high success rate. They are classed as protozoa parasites that are single-celled and can be free living in water and/or parasitic in their behaviour, making them, generally speaking, quite prevalent. They are an extremely mobile parasite and this is one of the reasons why they are so widely seen in the hobby; finding a host is relatively easy in a pond scenario as they can move around the pond, and they can multiply rapidly. They do not require a host to replicate and procreate via binary fission, or in layman’s terms, ‘cell-splitting’. Therefore, they can become prevalent; one becomes two, two become four, four become eight, and so on. The offspring from the original cell will be lacking half the number of denticles to that of the originator cell, they then have to synthesise the remaining denticles and the process is completed, and this ‘daughter’ cell can then carry out the same function in due course. For these reasons they can be found in particularly high numbers in Koi ponds. Denticles are essentially the sharp, tooth-like structures of the Trichodina that allow for them to attach themselves to a host and this is where the irritation is caused.
Ironically, unlike a lot of parasites, Trichodina merely uses the host as a vessel to attach themselves to. The mouth of the parasite (the cytostome) faces away from the body of the fish in order to feed on bacteria in the water and the opposing side (aboral surface) of the cell is used to attach themselves to the fish, quite clever really. So, unlike many parasites that physically feed from the host fish, Trichodina causes an indirect problem for our Koi. Low numbers will be harmless, however, due to their nature, a few can soon become many in the right environment. Trichodina can mature within a matter of a few days so its life cycle is fairly rapid and given its reproductive nature you can see why heavy infestations can occur in the right environments. There are studies within Talapia that suggest a parasitic-bacterium symbiosis and this relationship kind of goes hand-in-hand with these secondary occurring issues that we see with ulceration and abrasions on the skin of Koi.
Trichodina, as we have explored, are highly mobile and can find a host in a densely stocked pond with relative ease, particularly given the potential numbers of water-bound Trichodina. They are so adept at finding a host that they can even attach themselves to amphibians, insects, and even copepods! So, this is how they naturally integrate into the pond. They can also move from host to host through touch, meaning that in a Koi pond scenario if you find Trichodina on one Koi there is a high chance that it will be on others as Koi are constantly coming into contact with one another. There is a good chance you will have seen hundreds of flies just above the surface of your pond at some point, well this is ample room for Trichodina to hitch a ride, and then when in contact with the water, they become water bound. In this sense it can be hard to eliminate this parasite but there are definite methods to mitigate them. Equally, the introduction of new Koi can also be the introduction of Trichodina to the pond, whether it be from a dealer or another hobbyist.
If you are buying Koi from a dealer then this is where you can ask about their protocols and if the Koi has been scraped recently, you can even ask the dealer to scrape the Koi in front of you if you really have concerns.
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To read all of this detailed article, order your copy of issue 19 today.
It’s available in the back issues section of our website.