Poultry Health: Parasitic Worms

Have you thought about what may be happening within the guts of your hens? If not, they may look like this:

However, if your hens have an infestation of capillaria (hair) worms, there may be little to see unless you have a microscope, but the gut lining could be even more damaged than by the roundworms (ascaridia) in the picture above. Some free range farmers seem to be complacent about routinely worming their hens. All of the scientific and on farm evidence suggests that worms are indeed a problem on most free range farms. They can not and must not be ignored. Therefore I make no apology for raising the topic again.

There are various species of worms that can infest the intestines of hens. Their importance is that they can impede the passage of nutrients through the gut wall. In severe infestations of round worms (ascaridia), they not only compete for the nutrients in the gut but also can physically block the passage of the food through it. It has now become recognised that considerable damage to the gut wall can be done during the larval stage of development. The hens pick up (ingest) worm eggs from within the house or from the range area. These eggs can then develop into larvae within the bird in a few days. At this stage the larvae burrow into the gut wall and it can become thickened and damaged. The larvae then develop into worms and the eggs from these worms can pass with the faeces out of the hen to a site where they are ingested by any hens that are unfortunate enough to have pecked at that particular point! The timing of this cycle is important because the period from ingestion to shedding of worm eggs in the faeces ("prepatent period") can be as short as three weeks. It is easy to see that the range and house can quickly become contaminated.

Following a collaborative examination of the worm status of four free range flocks by ADAS (me) and what was then the Central Veterinary Laboratory at Weybridge, some clear cut conclusions were made. They were:

1. That hens deposit worm eggs onto the range (and within the house). The area closest to the house is where there is the greatest infestation, because that is the area that has the most numerous deposits of faeces. As one moves away from the house the risks to the hens of ingesting worm eggs decreases exponentially. The message: Encourage your hens to range well. Ensure that near to the house, large stones or weldmesh are in place to decrease the risks of the hens ingesting worm eggs.

2. The farms that have had hens on the range for the longest period had the worst infestations. This is because a new batch of pullets pick up embryonated (infestive) worm eggs that have been deposited by the previous flock. The message: Be vigilant. Don't assume that worm infestations happen to others and not to you. Therefore worm your flocks routinely (seek veterinary advice).

3. Cold or wet weather did not kill worm eggs in the ground. They lay in the ground awaiting hens to ingest them for very many months. However, sunlight (ultra-violet rays) kills worm eggs. The message: Expose the worm eggs in the ground to sunlight. Therefore use chain harrows in the summer to try to get worm eggs that are just under the surface to be raised to where the sunlight can kill them.

SOME SUGGESTIONS

a) Ensure that your pullets have been wormed during the rearing stage before you receive them. Yet again, there has been a recent case of pullets aged 16 weeks having been delivered with worms hanging from their vents. It is essential that you liaise with your pullet rearer and insist that they have been wormed. About 14 weeks old seems to be about an optimal age for this.

b) Worm the pullets just after you receive them (say when about 17 weeks old). If you don't you could get a production graph like the one below that shows a dramatic post peak dip in a young flock. In this particular case capillaria worms caused it. The hens had a bacterial infection and spotty livers that were associated with the worm infestation. Worming the hens improved the situation.

c) Look for symptoms of a worm infestation such as diarrhoea; loss of condition; reduced egg size and numbers; variable yolk colour; cannibalism.

d) Look closely at the droppings to see if you can see roundworms. However this is like shutting the stable door after the horse has bolted! Also, if they are in the droppings they could have slithered into the oviduct and got into tomorrow's egg. Hens have a design fault i.e. only one aperture at their rear end, that makes this possible. It would be hard to imagine a more damaging example of something that would do the reputation of both the packer and you a greater disservice. If worms are visible in the droppings, you probably have a bad infestation that ought to have been treated earlier. So don't waste time, act now. In future, act sooner.

e) Send hens for a post mortem examination and ask for a check of the gut contents for worm eggs. At the same time and also at regular intervals, into each of the two pots, collect 10 fresh dollops of faeces, using a miniature pooper scoop! Send these in a well sealed bag or parcel to your vet and request an assessment whether they contain worm eggs and if so, how many. If the vets' answer is that there are either no eggs or very few, repeat this in say 8 weeks time. However, if worm eggs are there, the vet may advise worming the hens as often as every 5 weeks. The aim of this is to ensure that the risks of worm eggs in the faeces are reduced, because the worms in the hens are too immature to be producing eggs. Therefore progressively, the number of eggs on the range area should gradually reduce.

f) Paddock grazing of the range area is essential in my view. Use weldmesh or slats to form a corridor to each area. Not only is the grass given time to recover but especially in the summer, the risks of a worm infestation can be reduced that has been caused by the hens picking up worm eggs.

In short, with good management, that includes routine medication, parasitic worms should not be debilitating your hens and therefore your bank balance! They are a problem over which you have control (unlike many other problems that free range egg producers face)!

For help with your worming problem contact Dave Cunnah at Janssen Animal Health.