NADIS Parasite Forecast - October
Use of meteorological data to predict the prevalence of parasitic diseases
The weather during August was mostly unsettled and fairly cool, with the UK often under the influence of nearby areas of low pressure. Temperatures frequently struggled to reach average levels, although there were some warmer days, particularly across eastern England, with temperatures up to around 25 °C, and the London area reached 30 °C on 22 August. However, frontal systems brought heavy rain and thundery downpours, particularly during the second half of the month (www.nadis.org.uk).
October Parasite Forecast/Update
The most recent version of this monthly parasite forecast may be accessed at www.nadis.org.uk.
LIVER FLUKE FORECAST
This month's parasite forecast places the focus firmly on liver fluke for two reasons:
- 2015/16 is likely to present a high to very high liver fluke disease risk in western regions of the UK, and
- A recent survey revealed that the majority of farmers do not know which is the best fluke treatment to use against specific stages of the developing parasite.
Industry representatives have urged farmers to consult their veterinary surgeon and SQP to develop their knowledge of liver fluke to ensure flock profitability and sheep welfare.
In 2014 there were no predicted high risk regions for liver fluke disease and only a moderate risk covering Scotland; all other areas of the UK were predicted to have a low risk; these NADIS predictions proved accurate.
- This year the risk of liver fluke disease is much greater for western regions of the UK.
- In Scotland the provisional early forecast is for 'a potentially high to very high liver fluke disease risk'.
- If wet conditions prevail throughout September this will result in a high risk of liver fluke disease in all western areas of the UK (southwest England, Wales, northwest England).
- A more accurate prediction of fluke risk will be provided during October once September weather conditions have been analysed but this may come too late for some farms. It is almost certain that prophylactic treatment with triclabendazole during September/early October will be necessary on those farms in Scotland where there is a history of liver fluke disease, and highly likely in northwest and southwest England, and Wales to prevent acute and subacute liver fluke disease.
While there will be different risks within geographical regions, in general:
- Scotland 'a potentially very high liver fluke disease risk' is predicted.
- Northwest and southwest England and Wales a 'high risk' is predicted.
- Central and eastern regions of England are forecast to be at 'low risk'.
Signs of Liver Fluke disease
- Sheep with acute fluke infestation may simply be found dead without prior signs of illness therefore it is important to have all sudden deaths investigated to allow immediate preventive measures to be implemented.
- Postmortem examination is essential to establish a diagnosis of acute fluke.
- Less severe clinical signs include reduced grazing, rapid weight loss, abdominal pain, anaemia, and being slow to gather.
Less severe clinical signs of subacute liver fluke diseases include rapid weight loss, abdominal pain, anaemia, and being slow to gather.
Anaemia (pale mucous membranes) caused by liver fluke disease.
- Triclabendazole is the only flukicide effective against very young immature flukes. Repeat treatment will likely be necessary 4-6 weeks later.
- Evasion strategies should also be adopted wherever possible by not grazing potentially contaminated, poorly-drained areas.
- Where flukicide treatment is necessary, sheep should be moved from these infested pastures.
- The effectiveness of fluke treatments should be monitored by your veterinary surgeon.
- The coproantigen ELISA test can be used to detect triclabendazole resistance two to three weeks after dosing and farmers should contact their veterinary practitioner for further advice where such drug resistance is suspected.
- Later fluke treatments (November/December onwards) could include either closantel or nitroxynil especially when triclabendazole resistance is suspected/proven on the farm.
- Albendazole and oxyclozanide can be used for the treatment of adult flukes during late winter/spring.
- Flocks with no previous evidence of fluke disease must maintain their farm's biosecurity especially with respect to purchased sheep but also cattle.
Evasion strategies for liver fluke should also be adopted wherever possible by not grazing potentially contaminated, poorly drained areas.
Parasitic Gastroenteritis (PGE)
- Clinical PGE is likely to be an increasing problem as larval challenge remains high because farmers are not sending lambs to market due to low prices leading to over-stocked pastures.
- Use of Group 4 (monepantel) or Group 5 (derquantel and abamectin) anthelmintics at this time of year could be considered in flocks to prolong the efficacy of the more commonly used Group 1-3 anthelmintics, and are essential in those flocks with confirmed triple-resistance (all anhelmintics in Grouprs 1-3). These products should only be used after detailed consultation with your veterinary surgeon.
Scouring lambs on 'safe pastures' should not result from PGE - consult your SQP or veterinary surgeon.
Anthelmintic treatments pre-tupping
- Anthelmintic treatment of all breeding females pre-tupping is rarely necessary.
- Dosing all ewes pre-tupping may select for anthelmintic resistant strains.
- In general terms, anthelmintic treatment should be targeted at leaner ewes, gimmers, or those sheep with dags.
- Rams are often neglected at this time and a faecal worm egg count will decide whether a pre-tupping anthelmintic treatment is necessary.
Anthelmintic treatment should be targeted at leaner ewes, gimmers, or those with dags. Investigate cause if a high percentage of sheep are in poor condition.
Growing cattle housed after their first or second season at pasture should be treated with either a Group 1 or 3 anthelmintic at housing. Pour-on Group 3 preparations have the added advantage they are also effective against both sucking and chewing lice.
Pour-on Group 3 preparations have the added advantage over other anhelmintic options in that they are effective also against both sucking and chewing lice.
Do not administer combined closantel and ivermectin preparations at housing in October or November because closantel in not effective against immature liver flukes. Cattle exposed to liver fluke infection should be dosed with closantel at least six weeks after housing to ensure that all fluke stages in the liver are susceptible to this drug. Observe meat withholding periods.
Local farm conditions may vary so consult your veterinary surgeon. Parasite control should be part of your veterinary health plan.
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