Levamisole is the active ingredient in broad-spectrum chicken worming products. It is one of the most effective products to use. However, I often hear about people using it in a food source rather than given as a liquid. I always recommend the liquid way given with a 5ml syringe.
The article below is written from a goat owner's perspective, but also applies to chickens.
For those who advise adding Levamisole (worming product) - Kilverm, Nilverm, Avitrol etc to treats such as bread or porridge, it's really not an appropriate way to dose a medication, a drug, a chemical which is supposed to be dosed according to individual weight.
The risk of adding it to treats is that the dominant birds may overdose and those lower in the pecking order may miss out or under dose.
This study was done on goats but may well apply to poultry - and just because you do it this way and your birds are ok, doesn't mean that it's good practice.
Poultry do have a much higher tolerance to overdosing than do goats but it is still not a suitable method to dispense it.
Levamizole toxity has been seen in Angora goats due to overdosing.
The symptoms appear very quickly and it has been known for an Angora goat farmer to see symptoms while still dosing a flock of Angoras.
Symptoms may appear 5-15 minutes after dosing but usually peak after 30 minutes.
The general off label dose of anthelmintic advised in goats is 1.5-2X that of the sheep dose.
Levamizole has a narrow toxic range compared to most anthelmintics and so should be used with care in Angora goats. Toxic levels may be reached at 4x (some authors suggest 2x) the therapeutic dose. In Angora goats, oral doses of 35 mg/kg (usual therapeutic dose ~8 mg/kg) may cause toxicity. A 10X dose will cause death. The cases where deaths have occurred in Angora goats have been associated with those doses that are reconstituted from powder form and the farmer has made a decimal point dilution error resulting in 10x overdose.
Toxic Symptoms caused by Levamisole Poisoning:
- Restlessness, hyperactivity
- hypersalivation (drooling),
- abdominal pain, colic,
- diarrhea, hiccups
- bradycardia (low heart rate), collapse.
- dyspnea (difficult breathing), tachypnea (rapid breathing).
- Nervous symptoms: miosis (contraction of the pupil), spasms, cramps, trembling,
- In extreme cases death can follow within 1 hour after administration due to respiratory failure.