IN recent months it has become apparent that the number of people keeping backyard poultry has increased hugely. Driven by media concerns over the welfare of chickens, the popularity of the “grow your own” movement and the trend for celebrity chefs to encourage us to help our kids understand “where food comes from”, both urbanites and rural dwellers alike have flocked to buy chickens.
Agri-merchants are reporting bags of layers pellets flying off the shelf and supermarket shelves are full of trays of pre-packed factory-farmed chickens that don’t look like they are going anywhere.
Small-scale producers
Whether birds are being raised in the garden for meat or eggs, several things are becoming clear. Generally, domestic poultry keepers have little or no idea about what they need to do to keep their birds in good health. Most are raising their birds using free-range systems in part or in whole.
As keepers with fewer than 50 birds have no need to register their flocks with the British Poultry Register, there are no means by which DEFRA can communicate messages about good health practices or disease alerts. In fact, it is commonly acknowledged that there is no way to tell exactly just how many birds, or keepers, there are out there.
That means when it comes to health, most of these new owners are completely reliant on advice from magazines, internet chat rooms – yes, there are chicken blogs – and, of course, advice from their vet or animal health adviser at the local agri-merchant.
Lectures on poultry disease may remain a dim and distant memory for some of us, but actually there is some pretty simple advice that we can give that will contribute greatly to the present and future health of small poultry flocks – such as feeding, hygiene and worming.
Parasitic worms in particular are a disaster just waiting to happen. Perhaps not on a large scale this year but in the years to come, untreated free range birds are very likely to become a significant source of infection and reinfection.
The chicken that got the worm
So what of the dangers presented by worms? The main worm species affecting chickens are Ascaridia (roundworm), Heterakis (caecal worm), Capillaria (hairworm), Amidostomum (gizzard worm) and Syngamus (gapeworm).
The direct lifecycle relies on worm eggs in the environment embryonating to develop into an infectious form which the bird then consumes from contaminated soil or litter. This can take about 10 days but the worm eggs can also survive for much longer periods of time depending on environmental conditions.
The larval worm that hatches out in the chicken can cause extensive damage to the gut wall by burrowing into the mucosa and the adult worms can compete for nutrients and physically block the passage of food. The prepatent period – the time between ingestion and shedding of new worm eggs in the faeces – can be quite short; just 20 days in the case of Capillaria and this is very important when it comes to establishing effective treatment strategies.
Ascardia species can lay thousands of eggs a day, so once contamination occurs the infection rapidly becomes established in the flock and can be very difficult to eliminate. The eggs can also be very sticky and fomite transmission on footwear and equipment represents a significant source of initial infection.
Intermediate hosts for the common poultry worms include earthworms, beetles, flies and snails, so the indirect lifecycle represents another way in which infection can occur, and a way in which the potential for infection is maintained in the environment. For example, in the case of gapeworm, earthworms can remain a source of infection for several years.
Free range birds and those kept on deep litter systems are most at risk of infection, both directly and indirectly. Bought-in birds are a frequent source of infection and as egg laying is only really optimal for the first couple of years of a chicken’s life, it is common practice for poultry keepers to introduce new, young stock to keep egg production at a reasonable level.
Young birds are also more susceptible to infection, so it is important that those are treated both before and after acquisition. All of these factors suggest that the risk of worm infestation increases significantly with time.
Between May 2005 and 2006, the SAC Veterinary Services conducted two surveys on behalf of Janssen Animal Health in 83 free range flocks with variable worming histories.
In those flocks where the poultry had never been wormed, 85% of birds over the age of 30 weeks had positive worm egg counts; in flocks where the worming interval exceeded 12 weeks, more than 80% were infected again.
Clinical signs
In common with many other worm infections, poultry worm infestation may result in no detectable clinical signs, especially in the initial stages. A drop in egg production, size and quality may be one consequence, and ill-thrift, anaemia and even death of birds can also occur.
As birds have only one aperture – the cloaca – which provides passage for both eggs and droppings, there remains the potential for chicken eggs to be contaminated and visible parasitic roundworms have been reported in chicken eggs.
Ascarids are up to 7cm long but Capillaria are thread-like and barely visible to the naked eye. In most cases the non-specific nature of the clinical signs makes it difficult for the novice to identify worm infections.
Treatment and prevention
There are only so many steps a poultry keeper can take to help prevent worm infestation, as access to insects and worms can rarely be precluded. Dry conditions, excessive heat or frost and sunlight can kill worm eggs, so attention to drainage and regular access to fresh pasture are sensible precautions.
Short grass will increase exposure of worm eggs to sunlight so they can be destroyed and placing pea shingle at the entrance/exit to the hen house will dry off feet and and break up droppings passed in this area. Birds should be fed from feeders off the ground to reduce the risks of picking up worm eggs with food.
De-worming represents the only really effective strategy but domestic users have, until now, faced problems accessing effective wormers in economical pack sizes.
Flubenvet Premix, the licensed infeed treatment, is used to manufacture Flubenvet 1% Medicated Premixture. This 1% formulation is now available in a 60 gram pack which is sufficient to treat around 20 birds for the required sevenday treatment period.
An added bonus is that the eggs from layers can still be eaten throughout the duration of the treatment, as there is a zero days egg withdrawal. Chickens raised for meat can be slaughtered seven days after the last day of treatment.
Preventive strategies rely on treating new arrivals on introduction to the flock, treating before putting the birds out to pasture and thereafter routinely at 10-12 week intervals – spring, summer and autumn.
Studies have shown that a more random approach to treatment is rarely successful because of the short pre-patent period and the potential for large scale worm egg production, resulting in significant re-infection.
Strategic programmes take into account the pre-patent period of common poultry worms and rely on treating active infections at intervals shorter than the pre-patent period –which can be anywhere between three and eight weeks – until infection pressure is reduced, as measured by a reduction in eggs per gram (EPG) counts.
Once infection pressure is reduced, regular treatment every 10-12 weeks aims to keep levels of adult egg laying worms in birds to a minimum.
In most cases there is the poultry world’s equivalent of a “periparturient” rise in worm egg counts at around the time of peak poultry egg production and doing an EPG count of samples of droppings at around that time is a good heath check if no discernible problems have been noted.
Even if you feel you don’t know enough about poultry, an effective worming protocol is easy to put in place and to communicate to poultry owners. Talk to domestic chicken keepers about the health of their flock today and be a good egg.
