It has beneficial effects on host defense mechanisms and restores depressed immune responses in animals and human.
Another interesting use of levamisole in humans is as a treatment for common warts (verruca vulgaris).
News of its anthelmintic efficacy and immune system benefits has been known among aquatic hobbyists for years.
As an added benefit, it boosts the immune competence of fish, humans, large animals, birds and some reptiles. This article hopes to pull together what scientific information is available, a bunch of individual accounts, apply some common sense, and put together in one place a helpful guide to the use of Levamisole HCl for treating aquarium fish.

It is not ovicidal, which means it will not affect eggs already present, but it will affect the larval stage of the worm. To ensure complete eradication of the parasite treat again after remaining eggs have hatched

Function of levamisole hydrochloride

The mechanism of action for its immunostimulating effects is not well understood. 

It is believed that it restores cell-mediated immune function in peripheral T-lymphocytes and stimulates phagocytosis by monocytes. 

The drug appears to restore depressed immune function rather than to stimulate response to above-normal levels. There are multitudes of medical studies being done with its use in humans and animals, the goal being to attain understanding of its immunomodulating mechanism. 

The mechanism will be defined, with time. However, at the time of the writing of this article, there is no complete answer to this question. For us, it is enough to know that it does stimulate immune function in fish that are suffering due to parasites or disease.