Don't risk your single farm payment
Environment Agency farm advisers are reminding farmers and contractors to ensure they are properly authorised and to take care when dipping, showering or jetting sheep, or they could pay the price.
Bob Merriman, Environment Agency Agriculture Policy Advisor said:
"Sheep dip is very polluting but, with proper authorisation and simple
good practice, farmers and contractors can avoid risks to the environment and
help ensure they do not fall foul of Common Agriculture Policy Cross-Compliance
requirements, with threats to their Single Farm payment from 2005."
Authorisation
Farmers and contractors in England and Wales must have a valid
authorisation from the Environment Agency to dispose of used dip chemical.
A code of practice for the Use and Disposal of Sheep Dip Compounds was published by Defra in 2001 and sets out good practice advice for protecting the environment when dipping, jetting or showering sheep, including the siting and use of mobile units
Before dipping or other treatment
During and immediately after treatment
Special precautions for mobile units
Using mobile units for dipping, showering or spraying sheep on farmyards
can carry a high risk of pollution, unless sheep dip chemicals are properly
contained and cannot enter surface water drains, ditches or soakaway areas.
Units can, however, be located in fields, providing the sites are first checked
to ensure they are level, have well established grass cover and are at least 10
metres from any well, borehold or spring. Further guidance is included within
the Code of Practice.
Disposal of used dip or unused chemicals
Even if used dip is treated before disposal, it is still very polluting and
must be disposed of in strict accordance with the conditions in the
authorisation issued by the Environment Agency. These are not onerous and
reflect long-established guidance.
Positive response
Bob Merriman continued: "Overall, farmers have responded positively in
recent years to reduce the frequency of serious water pollution incidents from
farms. There have, however, been very serious cases of pollution involving
synthetic pyrethroid sheep dip chemicals in North West England and
Herefordshire in recent months. These incidents highlight how devastating
synthetic pyrethroid dip chemicals are to river life. The incident in
Herefordshire killed a very important population of native crayfish, a
protected species which is in serious decline across England and Wales.
Wet sheep
"Environment Agency investigations in mid-Wales have highlighted the
damage caused by sheep being able to access streams immediately after dipping
with, in some cases, apparently just a few wet sheep causing serious pollution.
It is very important farmers follow this advice to keep sheep out of streams,
with drinking water troughs, so they don't rush to streams to drink. After all,
if the dip chemical washes off the sheep, they may be left un-protected."
The Groundwater Protection Code 'Use and disposal of sheep
dip compounds'
was published by Defra in August 2001. Copies are available from Defra by
telephoning 08459 556 000 or on the DEFRA website:
www.defra.gov.uk
By kind permission of NSA Winter Focus 2004
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A year round look at flukicide treatment
The parasite responsible for causing disease in sheep in the UK is Fasciola hepatica which requires a semi-aquatic mud snail as intermediate host. This dependency on a suitable snail for completion of the life-cycle means that the occurrence of fluke is markedly affected by climate, particularly rainfall and temperature. It is important to recognise that liver fluke differs from roundworms in several respects. Firstly, the life-cycle is longer, taking a minimum of 18-20 weeks. Secondly, there is a multiplication phase in the snail resulting in around 500-600 stages (cercariae) being shed onto pasture for each stage that enters the snail. These stages encyst on vegetation as metacercariae and are infective for livestock for several months. Thirdly, flukes can accumulate in the liver as they induce little immune response in the host.
Importance of environmental factors
Moisture - A moist environment is essential for the successful
development of fluke eggs in the dung. A water-film is required to allow the
free-living stages to locate and penetrate the snail host and also to enable
the stages shed from the snail to migrate onto herbage.
Temperature - Below average temperatures of about 100°C fluke eggs shed in the dung do not develop and hatch into infective stages and snail reproduction and development of fluke stages within the snail are also curtailed. As a consequence, in many regions of the UK the fluke life-cycle is only fully completed between May and October.
Snail survival - Snails can overwinter in mud and emerge the following spring. They can also survive dry summer conditions by burrowing deeper into moist ground.
Sources of infective cysts on pasture
Summer infection of snails - This leads to an accumulation of infective
cysts on herbage in late summer/autumn and accounts for the majority of disease
outbreaks in early/mid winter.
Winter infection of snails - Infective stages, derived from snails infected the previous autumn, can be shed in the spring/early summer when snails emerge from hibernation.
Types of fluke disease and treatment
Fluke disease occurs in three forms, acute, sub-acute and chronic, the
latter being the most common.
Acute - This occurs when massive numbers of infective cysts are
ingested from herbage over a short period. The simultaneous migration of large
numbers of immature fluke through the liver can cause severe tissue damage.
Acute infections can lead to sudden deaths in autumn/early winter before fluke
eggs appear in the dung.
Following a diagnosis, treat sheep immediately with a flukicide that is
effective against young immature fluke. Triclabendazole is the drug of choice.
If possible move treated livestock to well-drained pasture. Animals which
remain on infected pasture may require a further treatment after about 3 weeks.
Sub-acute - Cysts are ingested over a longer period and the liver contains immature and some adult flukes. Disease occurs in late autumn/winter. Treat as for acute disease.
Chronic This is associated with a prolonged intake of moderate numbers of infective cysts and the accumulation of adult fluke in the bile ducts. Chronic disease is mainly seen in late winter/early spring and is exacerbated by poor nutrition. A single treatment with any flukicide which has high efficacy against adult fluke is advocated, combined where practical with a move to low-risk pasture.
Aims of prophylactic treatments
Spring/early summer To remove adult fluke burdens which accumulate from
the previous year's infection and thus reduce the deposition of eggs on to
pasture. This will reduce the summer infection of snails.
Autumn - To prevent immature fluke migration and development following ingestion of metacercariae and to improve the condition of the ewe.
Winter - To kill adult and immature fluke and prevent liver/biliary damage and ill-thrift.
A typical treatment schedule in an average rainfall season would be:
Further treatments may be necessary in high risk areas if the season has been very wet. Frequency of treatment will also be influenced by the spectrum of activity of the flukicide.
Changing patterns of fluke infection
An increase in the number of cases of fluke disease has been observed over
recent years (see Figure 1). Fluke is normally associated with areas of the UK
which have a high annual rainfall such as western and hill areas. However,
there have been increasing reports of disease in central and eastern areas.
These regions have previously been considered too dry to consistently maintain
adequate snail habitats. Environmental and management factors are thought to be
responsible for the changing patterns of epidemiology.
| |
| Figure 1 |
Climate Changes in weather patterns are likely to influence the prevalence of fluke disease. Recently, there has been a trend towards milder winters, warmer and wetter spring, summer and autumn seasons. These conditions will favour transmission by extending the season of snail and fluke activity.
Farm management - Movement of untreated livestock and the presence of wildlife reservoirs (such as deer and rabbits) may be important in introducing infection into new areas. On many mixed farms, cattle are often not treated for fluke as they are more tolerant than sheep and develop partial immunity. As a consequence, they will act as a reservoir of infection for sheep. Also, movement of untreated livestock from endemic fluke areas in the west of Britain has the potential to initiate fluke infection on farms in more eastern areas that now have a wetter environment that is able to sustain the mud snail.
Anthelmintic resistance - Any development of flukicide resistance will allow treated livestock to continue to contaminate the pasture with fluke eggs. Although anthelmintic resistant roundworms are now widespread on many sheep farms in Britain resistance to flukicides is currently at a low level. It is important to monitor the effectiveness of flukicides on the farm, use them correctly and where possible to avoid using one chemical family of flukicide year after year. At times when livestock are exposed to a high fluke challenge, with subsequent migration of immature flukes through the liver tissues (usually late September-January), a flukicide that has high efficacy against immature stages is recommended. When the fluke burden is predominantly comprised of adult parasites (late winter/spring) then treatment with a drug with limited activity against immature stages and high efficacy against adults would be one way to reduce the selection pressure on flukicides such as triclabendazole.
Quarantine measures
A warmer wetter climate and the emergence of some resistance to flukicides
makes it important that fluke infection is not imported onto farms. Farmers
need to adopt an effective quarantine strategy in conjunction with a
veterinarian or specialist advisor. Where grazing is suitable for snail
habitats treat all sheep, goats and cattle arriving onto the farm with a
flukicide which is effective against immature fluke. As livestock can pass
fluke eggs for about 3 weeks post-treatment it is advisable, where practicable,
to keep treated imported animals on pastures with no snail habitat or house
animals for 4 weeks.
| Dr. Bob Coop is the retired Head of Parasitology Division of the Moredun Research Institute, Edinburgh. Moredun runs a membership scheme which aims to keep farmers and their vets up to date with the latest developments in animal health research. If you would like more information on fluke control or are interested in becoming a member of Moredun, please contact Margaret Bennett at The Moredun Foundation, Pentlands Science Park, Bush Loan, Penicuik, EH26 0PZ, phone 0131 445 5111 or visit their website at www.moredun.org.uk |
By courtesy of the NSA Sheep Farmer, September/October, 2005