In the second of our sponsored series looking at poultry health issues, we invite a panel of experts to answer our questions, this time looking at worms.
Meet the experts
Alan Beynon is a founding member of the St David's Poultry Team. He joined the practice in 1988 after qualifying from The Royal Dick Veterinary College, Edinburgh University. After two years he left to work in industry and abroad before returning again to become a partner in 1992. Alan has extensive experience in many areas of poultry production. He has carried out research in the layer sector with brachyspira and with autogeneous vaccines.
Alastair Johnston qualified from the University of Glasgow in 1983 and, after spending two years as House Officer (Large Animals) at the University of Liverpool Veterinary Field Station (Leahurst), he joined the Minster Veterinary Practice in York. Becoming a partner in the practice in 1989, he has worked in the multi-site poultry department for the last 15 years. He was president of the British Veterinary Poultry Association from 2003 to 2005.
1. Which poultry species suffer from worms: layers, breeders, broilers, turkeys, ducks, geese, game?
AJ: All of these can suffer from worm infestations. The worms tend to be specific for each species, although certain types of worms can cross-infect different types of bird. For example, gapeworm (Syngamus trachea) can infect chickens and game birds.
2. Where do the worms come from, and where and when is the threat greatest?
AB: Worms can be found in poultry litter, regardless if housed or free range. The actual worm infestation is the result of worm eggs and larvae being brought into the house on footwear, by vermin, insects, wild birds or vehicles, or it may be already present in the surrounding ground. The bird ingests the egg and it develops into an adult egg-laying worm. As soon as the litter is contaminated it is practically impossible to break the cycle as the worms, now inside the bird, lay copious amounts of eggs, which are passed into the litter from droppings. Free-range poultry also have access to earth worms and snails which can be the intermediate hosts to some species of worm.
AJ: Wet conditions in the autumn and winter can encourage increases in worm numbers. However, either the re-use of poultry litter or a poor clean out of poultry houses can allow a build up of worm eggs to occur. The introduction of poultry on to laying farms from rearing sites with worm infestations already present is another potential risk.
3. What are the main species of worms I need to look out for?
AB: There are four species regularly found in poultry:
• Ascaridia are roundworms, and are particularly common, but rarely causes severe disease. They reside in the small intestine and measure between 200 and 750mm in length. They can easily be seen in the droppings and will live in the host for 9-14 months if no worming programme is in place.
• Heterakis gallinae is a smaller worm (15mm) and inhabits the caeca of poultry. It acts as a vector to the protozoa histomoniasis or 'blackhead' - a particular concern to turkey keepers. Large numbers can give anorexia, diarrhoea and production losses.
• Capillaria, or the hairworm, is found in the intestinal tract and can be highly pathogenic with a heavy infestation. The capillaria worms cause irritation and inflammation in the small intestine, in turn causing stress and production drops.
• Syngamus trachea or gapeworm inhabits the trachea and lungs and is, uniquely, in permanent copulation. It is contracted by young birds and turkeys of all ages and can be a frequent problem in pheasant poults.
4. How do they affect my birds with regards physical performance and economic issues?
AB: Birds are affected in several ways including production drops, pale shells, reduction in bodyweight and sometimes enteritis. With breeder flocks, fertility and hatchability are sometimes affected too. Birds may appear lethargic and unthrifty. Specific species of worms can cause different symptoms; for example, birds infested with gape worm will present with respiratory problems. From an economic perspective worms will reduce your feed conversion, lower your egg production by up to 3% and give you downgrades.
AJ: Certain worms can cause the death of birds if present in higher numbers, namely Syngamus can block the windpipe and Ascaridia sp. can block the intestine. However, most worms have an effect on the bird's ability to absorb nutrients from the feed because of damage to the lining of the intestine. This can then lead to poor weight gain and anaemia.
5. How do I diagnose if I have a worm problem?
AB: It is generally a straight forward task to diagnose the presence of worms on your site by collecting fresh droppings and having them analysed at a laboratory which carries out worm egg counts. You will need to collect approximately 10 fresh droppings per flock and ensure you collect droppings of varying consistencies to get a representative sample. The droppings examined under a microscope to establish which worms are present, as ascertained by the shape of the eggs.
AJ: It is straightforward to identify adult worms of the Ascarid and Heterakis sp. during post-mortem examination of birds which have died with worm infestations. Capillaria sp. can be more difficult to spot and careful examination of mucosal washings under a dissecting microscope may be the only way to identify adult worms within the intestine.
The identification of worm eggs from faecal samples in the laboraotory is relatively easy. As a rule of thumb, the following counts can be considered to be the maximum acceptable levels:
• Ascarid sp. – 1,000 eggs per gram faeces
• Heterakis sp. – 1,000 eggs per gram faeces
• Capillaria sp. – 50 eggs per gram faeces
• Syngamus sp. – 50 eggs per gram faeces
6. How quickly do worms reproduce?
AJ: This will vary depending on the type of worm and also the age of the poultry. Syngamus trachea can develop from an egg to maturity capable of producing more eggs (pre-patent period) in 18 to 20 days. The pre-patent periods of Capillaria sp. is 20 to 26 days and Heterakis sp. varies from 24 to 30 days. The longest pre-patent periods are for Ascaridia sp. which vary from 35-42 days in young poultry to 50-56 days in adult birds.
7. What management /biosecurity measures can I take to help with the worm issue?
AB: Biosecurity is paramount for effective worm control. Limiting the movement into the poultry unit by people, pests, machinery and equipment will help ensure that no worm eggs or larvae are brought on to the site. Ensuring a proper clean out in between crops is essential, and litter should not be reused. Raising various species or birds of different ages on the same site can also be problematic.
AJ: Most disinfectants commonly in use for disinfection of poultry housing have some degree of activity against worm eggs. The use of dehydrating agents such as Stalosan powder are also effective. The removal of faecal material from the scratching areas and the range on a regular basis is very important. Exposing the faecal matter and therefore worm egg and larval stages to sunlight by harrowing is a very effective way of reducing infective burdens on the ground, as is moving drinkers and feeders regularly.
8. What licensed medicated poultry wormers are available and are there any alternative treatments I should consider?
AB: Flubenvet is the only licensed product in the UK or the water-soluble product Solubenol. These are the only medicines that have a nil withhold on eggs and have been tested extensively to show they are safe. Regular use of Flubenvet will reduce the worm contamination on an infected range as the birds "hoover" up the eggs.
9. What is the best de-worming programme over a season and longer term?
AB: Birds are generally wormed every eight weeks. A comprehensive worming programme designed specifically for the site should be discussed with your veterinarian. This may include regular faecal worm egg counts and post-mortems to assess the worm burden in the birds.
AJ: The licensed wormers should be used in either feed or via the water route for seven consecutive days. Repeat courses of treatment should then be implemented after a period of time less than the pre-patent period for the suspected infection. This could vary from three to nine weeks.
In flocks with a more severe worm problem, I would recommend a four-week gap between treatments. Once worm levels are falling, gradually increasing periods between worming treatments can be adopted.
10. Will we ever eliminate worms in poultry production?
AB: Given the ubiquitous nature of worm populations, many with indirect lifecycles, their ability to remain in the ground for long periods of time and continual use of the land by animals, it is seems very unlikely that we will eliminate worms from poultry production altogether.
AJ: Because of the presence of these worms in wild bird populations, it may prove impossible to completely eliminate worms from poultry.
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