How do I treat my chickens for parasites?

Backyard chickens are commonly infected with both internal parasites (worms, tapeworms, coccidia, and other protozoa) and external parasites (fleas, lice, mites, and ticks). At best, these parasites will make your chickens uncomfortable and perform poorly; at worst, they can cause severe disease and even death. Good parasite control is therefore important when you keep backyard chickens.

Internal parasite control

Free-range poultry, such as backyard chooks, are frequently found to be carrying a worm or protozoal parasite burden.  These parasites may have either a direct life cycle (the chicken eats the worm eggs off the ground), an indirect life cycle (an insect eats the worm eggs and is then eaten by the chicken), or both. As many intestinal parasites have indirect life cycles, it can be appreciated how susceptible free-range birds can be to infection, and how difficult it can be to prevent parasites.

Worming programmes are based around several key factors:

  1. Do the chickens have worms or protozoal infections?
  2. If they do, what type of parasites do they have?
  3. What is the life cycle of these parasites – how often will treatment be required?
  4. What drugs are effective against these parasites?
  5. Are these drugs banned in chickens, or are there withholding periods (WHP) to be observed?

The first two factors can be addressed by regular (2-4 times per year) faecal tests by your veterinarian. Once the presence and identification of the parasites are known, a worming regime can be developed for the client. Some points about these programmes include:

  1. Very few worming agents are registered for poultry. Levamisole and flubendazole are two, but praziquantel is not. Therefore flubendazole (Flubenol®) and levamisole (Nilverm®, Kilverm®) can be used without a WHP, but levamisole with praziquantel (Avitrol Plus®) must have a 4 – 6-week WHP applied to its use. Similarly, moxidectin and ivermectin must have a similar WHP applied when used.
  2. There is no evidence that topically applied ivermectin/moxidectin is effective against intestinal parasites.
  3. The best drugs for motile protozoans are the nitroimidazoles (e.g., metronidazole and ronidazole) – but their use is banned in poultry. Currently we have no effective treatment for these parasites that can be legally used.
  4. Low numbers of coccidia may not require treatment unless causing clinical signs. Low level infections are thought to confer a measure of natural immunity.
  5. Coccidia should be re-treated after 5 days.
  6. Toltrazuril is an effective treatment for coccidia, but the poultry formulation must be added to the birds’ drinking water as per directions. It has a pH of 12 and is unsuitable for treating an individual bird by direct dosing. (There is a Piglet suspension that can be used for this purpose.)
  7. Sulpha-based drugs are unreliable for treating coccidiosis as there is a lot of resistance.

As you can see, there are many considerations and complexities to consider, so it is best if you talk to your avian vet and have them advise you on the most effective and safe programme for your chickens.

External parasite control

Poultry are frequently carrying significantly heavy burdens of lice, mites, ticks, and fleas. Regular treatment may be required, especially if the chickens are handled regularly by their owners.

Pyrethrin-based washes, sprays and powders are generally safe and effective, but are not registered in poultry, so a WHP of 3-4 weeks should be applied to their use.

Some organophosphates (e.g., malathion) are registered in poultry but carry serious risks to the chickens, the owners, and the environment.

A newly registered product showing promise is flurlaner (Exzolt®).  An in-water medication used for 1 day and repeated after 7 days, it shows a high efficacy against all external parasites. Retreatment every 3-6 months is recommended and, when combined with biosecurity measures to exclude wild birds, effective control can result. As flurlaner is registered in poultry with a nil WHP, it has great advantages over sprays and washes.

Also Read

Updated on September 19, 2023
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