Death to pests
There are chemical treatments for getting rid of unwanted ‘guests’ and most of them can destroy the invaders with a single treatment.
However, there are also a few ways that involve readily available natural remedies you can grow, sprinkle around in the coop or add to food or water which provide an ongoing deterrent. These natural methods are not as 100% effective as a specific, over-the-counter chemical product would be and some do not really kill the pest in question, but their use helps to build a bird’s immune system to such a level that it can better withstand a mild influx of parasites without suffering any ill effects.
A chemical that wipes out a population of parasites with one treatment is going to be out of a bird’s system by the time the next challenge arrives, so having your birds healthy and strong all the time using ongoing natural products makes sense. There are some excellent chemical wormers available to buy, but most have an egg withholding period so the best strategy is to use them to give your flock a ‘clean out’ once or twice a year when the hens are not laying (late winter, later summer).
You may also need a specific wormer for some types of parasites, such as gapeworm, eg Flubenol or Aviverm (for large birds).
The most common off-label wormer is oral ivermectin (Eprinex® pour-on for cattle), used at a rate of 0.1ml (1 drop) per kilogram of bodyweight, placed on the bare skin underneath the wing. Note: this should not be fed to the bird, only applied to the skin. If you’re wondering about natural options to help suppress internal parasite populations, there’s not a lot of scientific information to go on.
Chopped green pumpkin seeds contain a chemical called cucurbitacin which is said to affect internal worm burdens.