Hairworms, also known as threadworms, are a type of parasitic nematode that can infect chickens and other poultry. These are threadlike and hair-like, and can be difficult to see with the naked eye. They are usually 7–18 mm long and 0.05 mm wide.

The worms live inside infected birds, where they feed on various parts of their body and lay their eggs. Their microscopic eggs get passed through into the chicken's faeces, contaminating the surrounding environment. The eggs are so microscopic, that you cannot see them with the naked eye. You need a microscope in order to identify their presence, hence why faecal tests are used as a great preventative tool. Other chickens in the flock will ingest the eggs when forging, eating, or drinking. Once ingested, the eggs hatch in the chicken and develop and feed on their crop, oesophagus, small intestines, or ceca. Upon reaching adult age, the worms will then lay their eggs which gets passed through the chicken in their faeces.

Symptoms include:

• Diarrhoea, greenish faeces

• Anaemia which can cause a pale comb

• Loss of appetite leading to weight loss,

• Poor absorption of nutrients

• Hens look depressed and dull.

​

Steps to take to protect you birds from roundworm:

​​Disinfect sheds with a Poultry Disinfectant which destroys worm eggs

• Separate birds from possible intermediate hosts

• Use a disinfectant and ground sanitiser that destroys worm eggs

• Use deep litter bedding system in the coop so the birds do not eat faeces

• Making sure that droppings are cleaned up daily

• Keep grass short

• Introduce apple cider vinegar and crushed garlic into the birds drinking water

• Use feeders and waterers designed to minimize contamination of your chicken’s food.

• Keep treats off the ground where possible