Average UK temperature in November 2018 was 7.3oC, which is 1.1oC above the long-term national average (1981-2010). This was the case across all regions of the UK, with temperatures also above average for the previous 3 months (September-November) for all regions except Northern Ireland.
Overall, rainfall was 101% of the long-term average for the UK in November, but varied greatly between regions: rainfall was above average in southwest and east Scotland, southwest and southeast England, south Wales and Northern Ireland, and below average in north Wales, northeast and northwest England, East Anglia. Regional rainfall in November also bore little resemblance to overall rainfall from September-November, with below average rainfall observed across England, Wales and Northern Ireland, and above average rainfall for this period in Scotland.
With average temperatures dropping, it is likely that development of eggs being shed onto pasture will begin to slow considerably. However, it is important to remember that already infective pastures may continue to be a source of disease, with the some roundworm species able to survive the colder conditions present on pastures over winter. It is therefore important to continue monitoring at risk groups of grazing animals for signs of infection and disease.
Winter provides a good opportunity to review and plan on-farm parasite control strategies ahead of coming grazing season. Preparation will help you to develop a robust yet practical programme, which should ultimately help reduce disease burdens, costs, and selection for anthelmintic resistance. Please speak to your vet or SQP about devising a parasite control plan to work for your farm. More information on sustainable parasite control is sheep and cattle can be found on the “SCOPS” and “COWS” websites, and cattle and sheep-specific parasite control planners are available through NADIS (Figure 1), which can help devise and visualise your plan for the coming year. Important things to bear in mind include:
Figure 1: Cattle and sheep specific parasite control planners are available through NADIS and can help develop a sustainable, practical on-farm strategy.
Whilst the Autumn fluke forecast for 2018 predicted only Medium risk in southwest Scotland and Low risk in all other regions (Figure 2), it is important to continue to be vigilant for signs of disease where this parasite has been known to be a problem previously, particularly since the milder than usual weather experienced in November may have allowed prolonged development of the infective stages of fluke later into the season.
Figure 2: Regional risk for liver fluke in autumn 2018. It is important to remember this forecast is a guide, and local conditions should be considered when evaluating on-farm disease risk.
It is also important to be on the lookout for chronic infection at this time of year. Chronically infected animals may show no obvious signs of disease, but can have significant reductions in productivity (Figure 3). Furthermore, chronically infected sheep and cattle can remain infected for months or even years if untreated, making them an important source of pasture contamination in the coming season.
Advised actions include:
Figure 3: Chronic fluke infection in sheep caused by adult flukes living in the bile ducts. Such animals may show no obvious signs of disease so it is important to check for infection through diagnostic testing.
Where fluke infection is identified:
The larvae of many disease-causing roundworms, particularly Trichostrongylus, may continue to be a risk in store and replacement lambs and, sometimes, yearlings into the winter (Figure 4). It is therefore important to maintain vigilance for signs of disease in at risk animals grazing potentially contaminated pastures.
It is also important to consider that acquired larval infections of abomasal roundworms (including Haemonchus and Teladorsagia) will undergo encystment or “hypobiosis” during the winter months, resuming development in the spring. Such populations can be an important source of pastures contamination the following spring, and in yearling lambs with heavy infections may cause scours in a similar manner to type-2 ostertagiosis in cattle. In such infections FECs can be negative, so it is important to consider grazing history and previous management when identifying at risk animals. These hypobiotic infections can be targeted with treatments effective against arrested larval stages, with products available in most major worming groups. For more information on anthelmintic selection and treatment options please speak to your vet or SQP.
Figure 4: Trichostrongylosis, characterised by black scour, is a common problem in store and replacement lambs in the autumn and winter months
Advised actions include:
Where anthelmintic treatments are required:
Scab (mite) and louse infestations can become a significant problem in sheep flocks over the autumn and winter months, typically September-April. Whilst the signs of scab and louse infestations (pediculosis) are similar, treatment options vary due to scab mites living beneath the surface of the skin, whilst lice reside within the fleece. This makes diagnosis an important first step towards treatment.
Sheep scab is caused by psoroptic mites (Psoroptes ovis; Figure 5). Infestations cause loss of condition, secondary skin infections and eventually death if untreated. Signs include severe itching, wool loss, restlessness, biting and scratching of affected areas and weight loss or reduced weight gain. When examined, the fleece may be wet, sticky and yellow due to serum discharge and the skin may become thickened and corrugated (Figure 6). Studies show scab mites can remain infective in the environment for up to 17 days. Consequently, fields, sheds and pens where infected sheep have been kept and handled should be considered a potential source of infection to other sheep during this period.
Figure 5: Psoroptic mites (left) can be identified from skin scrapings, whilst louse infestations can be confirmed in affected fleece (right). Photos courtesy of Dr Joseph Angell.
Louse infestations in the UK are caused by chewing lice (e.g. Bovicola ovis) and may present in a similar way to scab. Lean or emaciated sheep tend to be most severely affected, with widespread louse infestations often indicative of an underlying problem with flock management.
To reach a diagnosis:
Figure 7: Severe case of sheep scab characterised by wool loss, serous exudate and thickening of the skin.
Where treatment is required:
For growing cattle housed after their first or second season, treatment with a product containing either a 3-ML or 1-BZ anthelmintic is recommended as these are effective against encysted larval infections which may have been acquired in the latter stages of the grazing season. If untreated, heavy burdens of encysted larvae can cause type-2 ostertagiosis due to triggered mass emergence in late winter/ early spring. Encysted larval Ostertagia infections cannot be assessed by worm egg count.
Louse and mite infestations in cattle are not uncommon during winter housing. Generally low level infections are not of major concern, but heavy louse infestations may indicate an underlying management or health issue and, where sucking lice are present, may cause anaemia compounding existing problems (Figure 7).
A range of pour-on or spot-on synthetic pyrethroid products are available with efficacy against lice, whilst group 3-ML pour-on worming preparations are also effective. Injectible group 3 ML preparations are also effective against sucking lice.
A relatively small number of injectable and pour-on group 3-ML based products are available in cattle against mange mites, with some pour-on synthetic pyrethroids preparations effective against sarcoptic and chorioptic mange. Where mange infestations are a suspected cause for concern, please seek veterinary advice concerning further diagnosis. For more information on ectoparasite control in cattle please speak to your vet or SQP, and see the “COWS” guidelines.
Figure 7: Louse infestations are not uncommon in cattle housed over winter. Heavier infestations may indicate, and contribute to, underlying health and management issues.
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