THERE is an old saying that one sheep is another's worst enemy. As far as worms are concerned, this is often devastatingly true as any flock owner who lets his worming programme lapse will testify! The reason being, infestation spreads very quickly amongst the flock, which provide the link in the parasitical life cycle of egg ingestion, incubation of worms in the gut and then the expelling of immature eggs. This worm cycle production is ruthlessly efficient so you need to take swift action once worms are suspected.

Symptoms

Usually the first sign of worms is scour or diarrhoea. Lambs tend to succumb first as older sheep build up some resistance. Growth slows, fleeces tend to be dry and lacklustre and if left untreated, symptoms gradually worsen. Animals become dehydrated, tight skinned and will feel light to handle. They become prone to fly strike and maggots and eventually they die.

Types of worms

Worms affecting sheep are generally of the roundworm or tapeworm variety. They are both picked up from pasture when grazing and once infestation is present on a farm it is almost impossible to get rid of. Fortunately, drenches and a good pasture management programme can keep outbreaks under control and a well cared for flock shouldn't be bothered too much by worms. Keep a sharp eye out for these two types of worms though, as losses amongst a new lamb crop can be devastating.

Parasitic Gastroenteritis

Parasitic Gastroenteritis (PGE). This is mainly a disease of lambs though it can affect slightly older sheep. Eggs of the tricostrongyloid group are passed in the faeces and are then picked up and ingested by other youngsters. It is the most common summer worm problem in lambs and often strikes shortly after turn out. PGE damages the gut and appetite can be reduced by as much as 10-20% or more.

Nematodirosis

Nematodirosis is a round worm affecting young lambs up to 6 months of age. It is caused by Nematodirus infection and can cause devastating losses if allowed to get out of hand. Fortunately, lambs begin to build up resistance at around three months of age and by six months most are well able to resist infection. As ewes are immune to these worms they do not carry any adult worms and so do not re-infect the pasture.

In fact, it isn't adult worms that do the damage, but large numbers of infective larvae burrowing into the gut simultaneously. Lambs experience a lot of pain and will decline rapidly. If you notice lambs with their heads down, drooping ears and generally looking "tucked up" suspect nematodirosis infestation. They also get very thirsty due to dehydration so another give away is grouping around the water trough.

Liver fluke

Another parasite to keep an eye out for is, Liver fluke. This is caused by the dwarf pond snail Lymnaeatruncatula and is linked to high summer rain fall. Some areas are more prone to it than others. Symptoms include, weakness, signs of abdominal pain and as the disease progresses, acute haemorrhagic anaemia with sudden death occurring in animals where sufficient numbers of flukes are present. If you suspect Liver fluke, you should consult your vet immediately.

Control

Control is the optimum word here, not eradicate! Worm eggs can remain dormant in the soil for years so even if you move on to a holding where sheep haven't been known for decades, it's likely that sooner or later these parasites will stage a come back. The best you can do is to worm regularly and keep a sharp eye out for any break down in your worming programme. Your vet will help you decide on the best course of action and will also supply drenches. The following tips are also worth bearing in mind:

1. Worms build up resistance to particular drenches so change each year. The three main types of wormer are: Benzimidazoles (white drenches), Levamisoles (clear drenches) and Avermectins/Milbemycins (also known as the macrocyclic lactones, ML, and endectocides). There is also a herbal wormer from Verm-X, suitable for organic farmers, (see side panel for details).

2. Do not guess dosage! Underestimating can cause resistance build up by not knocking out the infection properly. If it isn't possible to get an accurate weight for your ewes and lambs err on the high side. With the exception of Levasol, wormers have a wide safety margin.

3. Worm ewes a couple of weeks before lambing for optimum results. If you can't do it at this time, do it immediately after lambing while they are in the bonding pen. Worming before and at lambing time have a marked effect on milk production so is well worth doing. Once wormed, turn onto clean pasture and don't mix with ewes still to lamb.

4. Dose all stock coming onto the farm on or before arrival and keep off pasture and separate from indigenous stock for at least 24 hours.

5. Put newly wormed sheep onto clean pasture, preferably that which has been grazed by other species. Our newly lambed flock always go out onto fields last grazed by our sucklers in the autumn, but the aftermath of hay cutting is also good.

6. If pasture is limited and you can't move onto rested areas then it's important that lambs are wormed every three or four weeks from six weeks of age. Actually we do this anyway as during April, May and June most of our fields are shut up for hay and these are just the months when worms thrive. Later in the year more land is available for grazing and worms are less of a problem.

Getting organised

Worming can be an onerous job unless you are well organised. Combining it with other routine tasks such as shearing or foot care can save time in gathering and penning but also consider using a specialised worming gun for larger numbers.

These can be purchased from most good agricultural suppliers and consist of a large container for the drench, often in the form of a back pack, connected to a worming gun. Using a system such as this, it is easy for a single shepherd to worm a tightly penned flock in a few minutes. You will need to mark each animal with a coloured marker though.

Herbal wormer

If you are producing naturally reared or organic products you may be interested in Verm-X's herbal worming pellets for sheep, goats and alpacas. Specially developed for stock on small holdings and organic farms, these pellets are a natural blend of quality ingredients including the Verm-X herbal stock formula which will control all known internal parasites.

The pellets are designed to mix into standard feeds or corn with all ingredients being natural and non-GM. The pellets have to be added to feed for 7 consecutive days every month. They are gentle on the digestive system, extremely palatable and have no known resistance. The course has to be repeated every 4 weeks.

The pellets are supplied in 1.5kg and provide a 4 month supply for 5 animals at a cost of £1.86 per animal per month.

Verm-X's success was recognised in both 2004 and 2006 when Verm-X was awarded a Bronze medal from the Green Apple Organisation, a Government Supported award scheme to reward products and industries for Environmental Best Practice.

Contact: Verm-X, Paddocks Farm Partnership Ltd, Paddocks Farm, Huish Champflower, Somerset, TA4 2HQ, Tel: +44 (0) 870 850 2313, Email: info@verm-x.com, www.verm-x.com.

Sheep worming guide

Useful article from the Intervet website offering advice on traditional wormers, dosage and brands. See at a glance tables compares the basic differences between the main brands of wormers. http://www.intervet.co.uk/Species_Pages/Sheep/Sheep_Worming_Guide.asp.

Sheep identification system

Following visits to farms, markets and abattoirs in the north of England, Scotland and Northern Ireland to check on the sheep tagging system, European Inspectors will shortly be assessing whether the UK can extend the double tagging derogation beyond June 2007.

Malcolm Corbett, NFU livestock vice-chairman said, "The NFU is pushing for an extension of the double tagging derogation until the rules on individual identification change.

Reports on trials using what will be a mandatory electronic tagging system are not expected until after July, which lends weight to delaying the implementation of the new rules beyond the first of January, 2008.

Currently, the UK use a batch movement system to deliver traceability and it is hoped that the European Food and Veterinary Office will be assured by the inspectors visit that the existing system is a sensible and effective process to minimise the spread of any potential animal disease.

If you are unclear as to the rules regarding the tagging and movement of sheep and goats, guidelines can be downloaded from the Defra website.

http://www.defra.gov.uk/animalh/tracing/sheep/index.htm