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Avivets News

Aug 20, 2017

Worm Control in Game Bird Release Pens

Avivets publish another game bird article with shooting partner, Guns on Pegs, with this month's article covering the control of worms in release pens. The full article is available here

Category: General
Posted by: avivets

The full article is available here.

The Gapeworm

Worms are not a new finding in game birds, they’ve been around for generations, they are a major threat to laying and breeding birds and our poults can still quite easily fall victim to them. The most common worm is by far the well-known gapeworm, Syngamus trachea, or Gapes. Young poults often pick up the worm eggs from contaminated ground of release pens where their parents may have been released the previous year or where they were caught up at the beginning of the breeding season. Once the worm eggs are ingested they mature into larvae which make their way to the windpipe of game birds where they take up residence. The male and female of the gapeworm species are attached to each other in permanent coitus, forming a Y shape as the female is considerably larger than the male – she’s the once producing all the eggs. These eggs are coughed up by the host, swallowed and passed out in faeces for the next bird to consume. Several species of bird are susceptible to gapeworm including rooks and crows - pest species that are well known for spending far too much time around breeding and release pens and bringing with them a number of diseases.

The eggs and larvae of the gapeworm can also be ingested by earthworms, which our unassuming poult would quite happily consume once in the release pen. There’s not much we can do to prevent that especially given the many benefits that the humble earthworm brings to our land and arable activities. Unfortunately, though, the earthworms can host the dormant eggs and larvae for several years, allowing a release site to become a reservoir of infective gapeworm eggs. Furthermore, the eggs themselves, like many other worm or coccidial species can remain dormant in the superficial layers of the soil.

Spotting the signs

Many game farmers and keepers are familiar with the classic gaping signs of the Syngamus trachea. However, it is worth a note of warning that the clinical signs can be confused with other respiratory diseases from time to time, especially when the disease is in the early stages or there may be concurrent infection. These other diseases could include Mycoplasma or Ornithobacter rhinotracheale (ORT) both of which are making an ever more prevalent appearance in game bird diagnostics. The classic signs of gapeworm are the coughing and snicking with a crouched-up bird and a ’gaping for breath’ expression. When the burden is bad enough the birds will eventually die from asphyxiation. The easiest way to confirm the diagnosis is visualisation of the adult worms in the trachea on a post mortem examination. If you are uncertain of the disease, a post mortem examination is well worthwhile for the benefit of accurate diagnosis and the health of the rest of the flock.

Intestinal worms seem to be less of a problem for game birds in comparison to gapes but that certainly doesn’t mean that they aren’t present. Game birds are susceptible to most of the common species of intestinal worms as poultry species, including round worms and hair worms. The worm seeming to make more of a common appearance is the caecal worm, Heterakis gallinarum and Heterakis isolonche. The caecal worm gets its name from the location in the intestinal tract that it prefers, the caeca, or large intestines. Heterakis worms tend to have a direct lifecycle, meaning their eggs pass from one host to another, through a faecal-oral route without needing an intermediate host. A bit like the gapeworm, caecal worm eggs can be carried by earthworms and also flies, and the eggs can also remain dormant in the environment for a couple of years or more.

Caecal worms in their own right are not too much of a problem for game birds. Most adult birds can deal with an infestation which perhaps only causes mild inflammation of the caeca in some instances. The greater harm from caecal worms comes from their ability to carry the disease Blackhead. This disease is caused by a protozoan called Histomonas meleagridis which can survive in the adult caecal worms or their eggs. The protozoal disease causes catastrophic damage to the intestinal wall as it migrates to the liver, causing further tissue damage and ultimately killing its host. Blackhead can be diagnosed by the classic circular lesions on the liver and in some rare cases a blue discolouration to the head. This is very rare and is only occasionally seen in turkeys.

Assessing the level of worms in your flocks in achievable through faecal worm egg counts where a collective sample of faeces from the birds are assessed for the number of worm eggs which is representative of the adult worm population. This laboratory test can also be performed on soil or earth samples taken from release pens or overwinter pens as the eggs remain dormant for prolonged periods of time. Your game bird vet should be able to provide this test for you.

Medication and prevention

Wormer medication has long been available for worm control in game birds in the UK. Flubenvet (Flubendazole) has a specific licence for use in treatment of game birds and is available to be milled into feed. Other medications are available to be given in drinking water, however, their use would be ‘off-label’ and having some dispensed, while not impossible, would require a conversation with your vet. Prevention of worms in game birds seems to have become less of a priority as medication is so easily available and effective. However, in time, our focus, as with the realm of antibiotics, is bound to shift towards a reduced usage and treatment only where necessary based on diagnosis.

For these reasons, the industry would do well to act now in an attempt to reduce the prevalence of worms through prevention. Prevention means a number of strategic actions for worm control, include rotation of breeding, overwinter and release pens and treatment of the ground with lyme, harrowing and ploughing. There is little better for killing worm and coccidiosis eggs than sunlight. Appropriate cleaning and hygiene management of feeders and drinkers will go a long way, particularly in the height of the rearing season when this seems to be last on the priority list. All of the worm species concerning game birds pass through faecal-oral transmission so if we can reduce stocking densities we will be able to reduce the rate at which transmission occurs and hopefully the level of infestation. As mentioned a number of wild birds can carry worms and worm eggs, so discouraging roaming wild birds especially crows and rooks will help prevent the likelihood of a number of diseases, not just worms. And finally worming medication looks to remain effective for the foreseeable future, there have been no reports of resistance in poultry or game birds. There are a number of products available for drinking water and Flubenvet remains available for the feed.