1. Roundworms (Ascaridia galli).
   These are the biggest and most common. They are white, up to 2 inches long and may be visible in droppings in heavy infections.
   
   
2. 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.
   
   
3. Caecal worms (Hetarakis gallinarum).
   As their name suggests, these worms spend most of their time in the lower end of the gut, the caecae. Frequently they cause no obvious harm in themselves but can carry another parasite, Histomonas, into the birds.
   Histomonas is the cause of blackhead and hence control of one parasite can help to control another.

Birds become infected by picking up worm eggs from grass, soil or faeces. 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 faeces, culled birds or worm egg counts on bulk faeces. Routine worm counts on droppings samples are recommended to monitor infection levels.

The only licensed wormer for laying birds is Flubenvet, (Janssen Animal Health). This product has a nil withdrawal period which means that it can be given in the feed during lay without the need to discard eggs, except in organic diets where eggs may need to be withheld.

Effective control is aimed at breaking the cycle of infection. Strategic use of in feed worming (starting in the rearing phase and during lay) will help to reduce challenge but this needs to be combined with limiting stock density on land, the use of paddock rotation, good drainage and the removal of heavily contaminated soil around the house before new pullets arrive

Coccidiosis

This parasitic infection of the intestines can lead to gut damage and, in severe infestations, death of birds. More commonly, poor control of subclinical infection reduces feed conversion, or leaves pullets with chronic irreversible gut damage. Such flocks may be uneven or underweight at grading, and may not perform to their full potential in lay.

Currently, effective control is achieved with drug treatments in feed that suppress oocyst output. These may involve the use of ionophores or chemicals on a step-down programme to ensure a good build up of immunity in pullets. To avoid problems with drug resistance and continuous drug treatment, and help ensure even and target weight pullets, a live attenuated oral vaccine (Paracox: Schering Plough) is available. This vaccine is currently administered in the drinking water as a single dose between five and nine days of age. Alternative application methods for the vaccine are being developed for ease of use.

All treatment/vaccination strategies should be supported with effective biosecurity The use of a disinfectant with proven efficacy against coccidial oocysts will reduce challenge pressure. Maintenance of good friable litter will reduce oocyst build up.