Deworming with fenbendazole

[casportpony]

I think @casportpony posted a withdrawal period for praziquantel once before. Hopefully she'll chime in.

I can't remember if I posted something official or not. I know I found an egg residue study for meloxicam, but I don't remember finding one for praziquantel.

 

[casportpony]

I thought some of you might appreciate this:

"Prophylactic Deworming

I have been saying this for years (because I have been seeing this for years!) and here it is: Many young and adult birds can be harboring ascarids (especially if they were parent-raised for any length of time) and you can run fecals all day, and guess what? The fecals will almost always be negative. A paper out of the Univ. of Georgia a few years back confirmed this. Many a time I have been a hero when I have dewormed a bird during a second or third opinion, when it passes a pile of ascarids and shocks the owner after being repeatedly told by other vets that "the fecal was negative." Well, deworm it anyway, with something safe. I routinely use pyrantel pamoate, since you can't hurt a bird with it, unless you aspirate it! "
Source: http://www.exoticpetvet.net/avian/challenges.html

 

[dawg53]

Prophylactic Deworming: I remember seeing it before. I'm glad you posted it again!

 

[casportpony]

I did a fecal on my chickens and thought I'd share the process, hopefully this be informative.

I am planning to treat my hens with 20 mg/kg fenbendazole for tapeworms and nematodes.
Here's what I found on the fecal exam.

Ascaridia (roundworms):
View attachment 1711364
There were many, many of these tapeworm eggs. If you look inside the egg, you can see the little hooks. There are six of these so what's inside each egg is called a hexacanth embryo. (hex = 6, acanth = thorny).

View attachment 1711366

Here is a "squash prep" of a motile (moving) tapeworm segment I found in the chicken feces. They have an impressive number of eggs in the uteri. This is only one group of proglottids, each segment is delineated pretty clearly here. Each segment has its own uterus, testes and a vagina. They are literally baby-making machines, these things. They're amazing.
Here's a segment of about 3 mm that I picked out of feces and literally squashed it between a slide and a coverslip. Each of the striations is an individual segment. Whatever species this is (Railletina, I think) sheds proglottids in packets like this. This is 4x magnification.

View attachment 1711368

Moving up to 10x, you can start to see how much of this thing is actually eggs which you can see spilling out due to being squished.


View attachment 1711369

And closer still at 40x. All eggs. They are actually really magnificent creatures, aren't they?

View attachment 1711370

Here's a shot of the edge of the whole package, showing individual segments. The vagina is seen here, but you have to really look. They are a tiny divot at the edge, just right of each high point. The one in the middle appears to have an egg emerging from it.

View attachment 1711374

So. Neat. My chickens have worms. Time to deworm them. To make it simplest, I am planning to treat with oral fenbendazole, 20 mg/kg once a day for three days, then I'll recheck them after 2 weeks. This should kill the tapeworms at this dose, and will kill any nematodes they have too, including gapeworm if those happen to be present.

View attachment 1711375

My chickens weigh about 2 kg (I'll get exact weights later on) so if I want to kill the tapeworms, I'll give them 20 mg/kg, or about 40 mg per chicken per day for 3 days.

I weighed out 8 grams of paste, which equals 800 mg total.

View attachment 1711378

For ease of dosing, I brought it up to 20 mL with distilled water so it's a liquid. Each mL now contains 40 mg fenbendazole, so I will have enough premix to dose everyone. I don't know how stable FBZ is in water, I plan to use it all between now and Monday, but I am keeping it in the fridge just in case. This is OFF LABEL use for chickens, so I plan to discard all eggs for at least 21 days.

View attachment 1711398

Best post I have seen in a long time!

 

[Shadrach]

Exactly Dawg. Classes of dewormers that are active against tapeworms and other cestodes are very few and far between. Pyrazinoisoquinolines (like praziquantel) and benzamidazoles (like fenbendazole) are pretty much it.

Admittedly fenbendazole isn't that great for tapeworms and has to be given at high doses to even scratch the surface, but it is the only one of the list above that's approved in the US for use in food animals.

I've had a discussion before about flubendazole products on BYC and was told that while it may be licensed for use on livestock in Europe it wasn't the case in the USA. (?)
So, does approved mean licensed in this case?

 

[casportpony]

I've had a discussion before about flubendazole products on BYC and was told that while it may be licensed for use on livestock in Europe it wasn't the case in the USA. (?)
So, does approved mean licensed in this case?

It means that because it's not approved in the US for laying hens or any other livestock that there *is* a withdrawal when given to food animals in the US.

Read this:
https://www.avma.org/KB/Resources/FAQs/Pages/ELDU-and-AMDUCA-FAQs.aspx

I think it's FDA approved for people, so it can be used in pets and livestock.

Edited to add:
Here in the US there are only two two de-wormers approved for use in laying, one is hygromycin b, the other is fenbendazole, but fenbendazole is only approved at miniscule doses which will only treat large roundworms and cecal worms. The approved/zero day egg withdrawal dose is 1 mg/kg for 5 days. Use more than that and they recommend observing some with of egg withdrawal period.

 

[Shadrach]

While it's on my mind; Flubenvet which is a Flubendazole based product gets used for tapeworm here.
Dosage 0.95 mg of active ingredient (Flubendazole) per kilo of live weight for 5 days.

 

[Shadrach]

It means that because it's not approved in the US for laying hens or any other livestock that there *is* a withdrawal of given to food animals in the US.

Read this:
https://www.avma.org/KB/Resources/FAQs/Pages/ELDU-and-AMDUCA-FAQs.aspx

I think it's FDA approved for people, so it can be used in pets and livestock.

Here we go again.
So Sue is wrong?

scratch the surface, but it is the only one of the list above that's approved in the US for use in food animals.

 

[casportpony]

ere we go again.
So Sue is wrong?

No, she's not wrong. Fenbendazole at the amounts she is using is considered off label and *does* require egg withdrawal.

 

[Shadrach]

No, she's not wrong. Fenbendazole at the amounts she is using is considered off label and *does* require egg withdrawal.

I wonder why that is.
One of the advantages and one of the reasons it is licensed in the EU is because the studies carried out showed negligible residue in the egg white and non critical residue in the yolk.
Afaik, here at least, for a slaughtered fowl there is a recommended 7 day wait post treatment with Flubendazole.
It seems a bit strange that the tests carried out in Europe which state eggs are safe to eat are not accepted in the US, particularly when you have mentioned before that this product hadn't undergone FDA approval.