You could be forgiven for thinking that if chickens are running around free-range on a clean, grassy area that they would be free from internal parasites. However, worm eggs and larvae occur naturally in the environment; inside earthworms, insects and wild birds (which are intermediate hosts or carriers). Contaminated soil and dirty poultry litter can also harbour eggs and larvae. These can also stick to footwear, poultry equipment and even pets.

Worm eggs are able to live in the soil for years and are resistant to disinfectants so good hygiene and treating the birds to keep worms at bay is essential. All birds are vulnerable and free range poultry that pick up insects and earthworms are particularly at risk of worm infestation. Once inside the bird the adult worm lays more eggs which are again passed out into the environment and the cycle begins again. In rare cases worms can even be incorporated into the chicken’s egg.

The most common worm found in poultry is Ascaridia gali (Roundworm), which can be a serious threat. They are capable of causing a necrotic-like enteritis and subsequent E.coli infection as well as migrating to other parts in particular the liver and causing damage. Severe infestation of roundworms can block the intestines, even causing them to rupture and may be visible in the bird’s droppings.

Capillaria contorta (Hairworm) is a thin, hairlike, pale coloured roundworm, which can be anything from 7-18mm in length that infests the crop and oesophagus. Capillaria obsignata is found in the small intestine. Infection is through the oral route. These worms although small can be very debilitating to the birds concerned.

Cestodes (Tapeworm) is a segmented parasitic worm that attaches itself to the small intestine by the head. Growth is from the head outwards, so the segments furthest from the head are the ripest and contain the eggs. These egg containing segments will break away and eventually be passed out of the bird’s body via the droppings. The minute eggs are then ingested by a smaller being, such as an insect, slug or earthworm, whereupon they hatch. The chicken then becomes infected when it eats the insect that contains the tapeworm cyst. There are many different species of tapeworm that poultry are hosts to and these can vary from minuscule worms to some around 25cms (10 inches) in length.

Heterakis gallinarum (Caecal worm) is a nematode parasitic worm up to 1.5cm in length that is found in the caecum. It causes inflammation of the caecum but more importantly it can carry another parasite, Histomonas meleagridis, which causes Blackhead in turkeys. Histomonas meleagridis is a protozoan parasite that chickens can carry but to which turkeys, pheasants, game birds and peafowl could succumb.

Syngamus trachea (Gapeworm) is a nematode parasitic worm, which lives in the bird’s windpipe. They can so severely infest this part of the anatomy that the bird chokes, hence the ‘gaping’ for breath and the name. Infection is via the oral route, with earthworms, slugs and snails being the worm hosts. Gapeworm is more likely to affect free-range birds, especially where gatherings of wild birds are present, for instance, near a rookery or starling roost.

Poultry should be wormed from around 6-8 weeks of age and thereon after about four times a year if the chickens are periodically moved to fresh pasture, housing litter is kept clean and feeding and drinking equipment cleaned thoroughly on a regular basis. Where there are flocks of wild birds, such as starlings, sparrows or crows living near poultry, then the risk of the poultry harbouring worms as well as external parasites will certainly be greater.

If poultry are kept in one area alone or on land that has had poultry on it for several years, then worming needs to be carried out more frequently. Clean pasture is paramount and the use of mobile housing for a small number of chickens, whereby the unit can be moved – often daily – will help to prevent a build up of faecal infection.

Treating for worms should never be done on an only when you remember basis. Have a routine programme of treatment with the aim of keeping the birds free of adult, egg laying worms. Flubenvet is a product licensed in the UK by the Veterinary Medicines Directorate (VMD) for worm treatment in poultry which is incorporated in the feed. Flubenvet comes as a white powder in a 60g pot which will cater for up to 20 birds. It can only be purchased from a veterinary practice or a qualified agricultural merchant or pet store as it is a Prescription Only Medicine (POM). Another product, also licensed as a wormer is Solubenol. This is soluble and should be administered in the birds drinking water. Only products that have a licence may be marketed as wormers.

The management of your poultry will play a major role as to whether or not you are successful in keeping the risk of worm infection down. Worming alone will not deal with the problem if good husbandry practices are not adhered to. During worming treatment all litter should be destroyed and the housing thoroughly cleaned out before fresh litter in replaced. Without this attention worm eggs could remain and chickens will quickly become re-infested.

Some of the biggest health challenges to poultry are through the gut and any natural help in fending off worms and other bugs is a bonus. Cider vinegar is often quoted as being useful for this and is placed in drinking water. By altering the pH level of the gut and making it more acidic it becomes a less hospitable environment, making it more difficult for parasites to pass through and go on to damage vital organs. Try only a little Cider vinegar in the water at first because if the taste is too strong or they take a dislike to it the birds may resist drinking which could lead to dehydration.


This article was written exclusively for Smallholder magazine. For more expertise in poultry from Janice Houghton-Wallace, subscribe to the monthly magazine by calling 01778 392011 or emailing It is also available from newsagents.