Jump to content
mysterygirl

Flukes and Mysterious Praziquantel

7 posts in this topic

Flukes and Mysterious Praziquantel

Flukes are blood-dwelling parasitic flatworms, a genus of trematodes called Schistosoma. Schistosoma have the distinction among flatworms of having both male and female sexes. The male (remarkably) engulfs the much smaller female entirely in his underbelly groove, where she spends the rest of life reproducing. These pairings are monogamous.[1]

The adult pair produce about 300 eggs each day, one every 4.8 minutes, which are excreted by the fish through their urine or feces. Fluke larvae require a freshwater snail to host their growth before the next stage of the parasite emerges that can infect a new host by directly penetrating the skin. The snail required is specific to the various fluke species.

Schistosomiasis, the human infection of flukes, is considered by the World Health Organization as 2nd only to Malaria in its socieo-economic devastation.[2]

In goldfish, adult flukes parasitize mesenteric blood vessels. They use the use the globins from their fish-host’s blood for their own circulatory system to distribute oxygen to their cells.

The drug Praziquantel (PZQ) has been used by vets and doctors for almost 40 years to treat parasitic worms. Goldfish and koi keepers use it to treat their fish for flukes. Developed by Bayer and Merck in the mid 1970’s, it has since become the most popular treatment for fluke parasites because of its low cost, ease of application and high tolerance with few adverse side effects but the exact target and mechanism of how it works remains a mystery.

In one recent experiment, Praziquantel caused abnormal and irreversible lesions in the flatworm’s skin called their tegument.[3]

Bayer’s website states that “The primary effects of Praziquantel on cestodes and trematodes are tetanic contractions of the parasitic musculature and an intense vacuolation of their integument. The integumental damage probably results from the interaction of Praziquantel with phospholipids and proteins that create an imbalance in the ion transport of cations through the integument membranes. The destabilisation of the integument renders the parasites vulnerable to the digestive system and the immune defense of the host.” [4]

That is to say Praziquantel may increases the permeability of the membranes of fluke cells towards calcium ions. The drug seems to induce muscle spasms and cramp-like contractions of the parasites, resulting in paralysis in the contracted state. The dying parasites are dislodged and are then killed by the fish’s immune reaction.

Other possibilities include disrupting the parasites ability to lay eggs or attach to the host.

Another hypothesis concerning the mechanism of action of Praziquantel has been recently reported. The drug seems to interfere with adenosine uptake in cultured worms.[5] That could affect their blood flow, energy transfer and sleep regulation.

Although we don’t yet know exactly how it works on eliminating flukes, Praziquantel remains the most effective and safest treatment for blood-flatworms in goldfish and koi.

Share this post


Link to post
Share on other sites

Hi Mysterygirl,

This type of flukes is not the flukes that infect fish. There are a number of very distinct differences. I happened to have worked in schistosomiasis research for a while.

1. The flukes that infect fish that we talk about most often belong to the genus Gyrodactylus and Dactylogyrus. These flukes do not need an intermediary host, such as a snail, as is the case of schistosoma.

2. Praziquantel does kill schistosoma, although we are now seeing some amount of drug resistance.

3. The mechanism of prazi action on these worms appear to be the same, which is to punch holes in their tegument, causing it to be leaky, leading to death.

Share this post


Link to post
Share on other sites

This paper would be better titled "Blood Flukes and Mysterious Praziquantel" as it is specifically about the blood-fluke genus Schistosoma. For more on the fluke genus Dactylogyrus and genus Gyrodactylus check out Koko's own paper called Flukes, Diagnosis and Treatment Options. There are no human health concerns associated with Dactylogyrus or Gyrodactylus flukes, which are also treated with Praziquantel.

Share this post


Link to post
Share on other sites

This paper would be better titled "Blood Flukes and Mysterious Praziquantel" as it is specifically about the blood-fluke genus Schistosoma. For more on the fluke genus Dactylogyrus and genus Gyrodactylus check out Koko's own paper called Flukes, Diagnosis and Treatment Options. There are no human health concerns associated with Dactylogyrus or Gyrodactylus flukes, which are also treated with Praziquantel.

But this is where I am having problems understanding where we are going with this article...the schistosomes ONLY infect humans and some other mammals. So why are we talking about it as a research article on a fish forum?

Pardon my directness, please.

Share this post


Link to post
Share on other sites

Then I'm not sure what relevance this article has to this forum?

Share this post


Link to post
Share on other sites

Wow, neat to see that this medication has so many applications, I had no clue it worked on parasites other than the ones I might experience with goldfish! I'm always happy to learn new capabilities of the common fish medications I keep in my cabinets, and happy to see the science bug has bit others! Thanks for sharing :)

Share this post


Link to post
Share on other sites

Hi all,

I was investigating how Praziquantel works before dosing my pond. I thought it was interesting that it is not entirely clear to modern science. Most of the research money to investigate the exact mechanism is going to the variant of flukes which cause problems for humans, so that seems the most likely reason the Prazi papers I found concerned only the blood-flukes genus.

I certainly didn’t understand that blood-flukes don’t affect fish, as there were plenty of comments like this one:

Like the Schistosomatidae, the natural reservoir for Opisthochiidae is fresh water snails, with fish as second intermediate hosts. Humans pick up the parasites by swimming or bathing in infested water, or by eating raw or undercooked fish. – [1]

If those of you who have actually studied the subject and feel that this post is irrelevant or confusing to the intended audience please remove it. Simply consider it the trail of my investigation into flukes, Prazi and its mechanism of its action on them.

Share this post


Link to post
Share on other sites

Create an account or sign in to comment

You need to be a member in order to leave a comment

Create an account

Sign up for a new account in our community. It's easy!

Register a new account

Sign in

Already have an account? Sign in here.

Sign In Now