Fenbendazole poisoning?


8 Years
Apr 7, 2013
Northern California
I am sick right now as I may have poisoned one of my hens. :hit
I was on the last day of worm ing with fenben (10% goat solution). Today I found one of my hens dead - she died in her sleep. The fenben is the only suspect. She was my largest so the least likely to get enough of an overdose to harm her. I was dosing her at .6 as suggested for a 6+ lb bird.

She was about 4 years old and still laying though she had stopped for the season. She was acting normal and lively the last day. Does anyone know how much it would take to make her that sick? My best guess is she got a hold of part of another's dose, but that would have only been an extra .2 If it is this easy to harm one of my birds, I am not keen on trying to worm them again.
Sorry that you lost your hen. You did not overdose her. Kiki is correct that you gave her less than the dose. If you still have the body, refrigerate it in a plastic bag. Then contact your state vet to get a necropsy in the morning to look for a cause of death. Here is a link to you state vet contact info:
I have been reading about worming specifically using fenbendazole - in the studies they dosed 100 times more than recommended and didn't see any adverse affects.

Here's an excerpt:
"Fenbendazole has been shown to be a very effective treatment for eliminating Capillaria (capillary worms), Heterakis (cecal worms), Ascaridia (roundworms), and Syngamus spp. (gapeworms). Toxicity from overdosing with fenbendazole is very remote. Research indicates that amounts up to 100 times the recommended dosages have been given under research conditions without adverse effects to the birds. Use of this product during molt, however, may cause deformity of the emerging feathers."

I will see if I can find the direct source again.
Thank you all so much!!! I can stop feeling quite so miserable. And thank you for the helpful links! I always love to have the resources.

I unfortunately can't take her in to get a necropsy. With the holidays coming up, I don't even have room for a pint of Ben & Jerry's in my freezer. I could use one...

Re: the dose. I had read on multiple threads that was the correct dose according to a vet? I guess I need to start scouring the UC websites
I forgot to add how I was dosing them.

I use small bread cubes and evenly distributed the dose for each between 3 cubes. Since I have a small group, it is relatively easy to track and I knew the exact dose each was getting. However if .6 is not the right, then I might switch to water treatment for convenience.
Sucking up the med I to a syringe and dosing each one to the beak is the best way to ensure they each get the correct amount.

Under dosing is just the same as not even dosing them to begin with. It's actually worse, it will allow the worms to build up a resistance to the med.

Adding it to water is a bad idea because it isn't water soluble and you won't have a clue as to how much each bird gets.
Very sorry for your loss. :hugs
You're in California, near Davis, yes? Why not drop her off for a $20 necropsy at CAHFS?

You could also take a bunch of poop and have it tested for worm eggs and coccidia.
cahfs fecal.png
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