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Internal Parasites

Infections with internal parasites cause damage to the bird's intestines. This may result in a variety of problems including:

  • Decrease in shell strength, yolk color, egg size, and egg production.
  • Poor body weight gain leading to unevenness or stunted birds. Affected birds may be dull and show pale combs.
  • Increased cannibalism through vent pecking due to straining. Death, in very heavy infestations.

There are 3 main worms that may cause problems in free-range or cage birds:

  • Roundworms (Ascaridia galli). These are the largest and most common. They are white, up to 5 cm (2 in) long and may be visible in droppings in heavy infestations.
  • Hairworms (Capillaria). These are much smaller (hair-like) and are barely visible with the naked eye but can cause significant damage even in only moderate infestations.
  • Cecal worms (Heterakis gallinarum). These worms spend most of their time in the ceca. Cecal worms are generally harmless, but can be the intermediary host of another parasite, Histomonas meleagridis, the cause of blackhead disease.

Birds become infected by picking up worm eggs from litter, soil, or feces. The worm eggs need warm moist conditions to develop outside the bird, which is why problems are frequently worse in the spring and summer, especially following a wet spring. Worm burdens can be identified by examination of feces, culled birds, or worm egg counts on bulk feces.

Effective control is aimed at breaking the cycle of infection. Strategic use of anti-parasitic drugs (in the growing phase) will help to reduce challenge, but this needs to be combined with limiting stock density on land, the use of range rotation, good drainage, and the removal of heavily contaminated soil around the house before new pullets arrive. 

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