The average temperature for the UK in October was 9.6oC, 0.1oC above the long-term national average (1981-2010). Regionally, temperatures varied around their respective averages for October by up to 0.5oC (East Anglia) with a similar pattern for the previous three months (August-September).
Despite the torrential rain experienced in mid-October, overall UK rainfall was 82% of the long-term average for the month. This pattern was also observed regionally with the exception of northern Scotland. Regional rainfall for the previous three months was also lower than the long-term average with the exception of northern Scotland, where rainfall was above the long-term average and southwest Scotland, northwest England and north Wales where rainfall was equivalent to the long-term average.
Overall, the seasonally typical temperatures are likely to have allowed continued development of parasites on pasture where present. The lower than expected rainfall is likely to have reduced the risk of diseases associated with wetter conditions like fluke, although local weather patterns and conditions should be taken into account when considering on-farm disease risk.
The fluke forecast for autumn 2018 is based on monthly rainfall and temperature data from May-October 2018. This year’s forecast predicts Medium risk for liver fluke in southwest Scotland and Low risk across all other areas of the UK (figure 1).
Figure 1: 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.
Whilst fluke risk is predicted to be low across most of the UK, it is important to take local factors into account when considering on-farm disease risk. Development of liver fluke and its intermediate host, the mud snail (Galba truncatula) on pasture is dependent upon temperature and moisture, with warm wet conditions optimal. On farms with permanently wet pastures and/or permanent water bodies (figure 2) snails may have continued to develop over the summer and autumn, potentially leading to high pasture infectivity. Current abattoir feedback shows fluke infection is being detected on a regular basis (figure 3).
Figure 2: Areas of permanently wet pasture can provide optimal conditions for mud snails, and by extension liver fluke. Such areas can be found on some farms year-round even with low levels of rainfall, such as this farm in Argyle, September 2018. Photo courtesy of Dr Philip Skuce, Moredun Research Institute.
Continued vigilance for signs of disease and on farm contingency plans in the event of an outbreak are therefore of great importance. Liver fluke affects both sheep and cattle (figures 3 & 4), meaning pastures grazed by one are a potential source of infection to the other. Sheep are more susceptible to acute infection, caused by large numbers of migrating juvenile flukes, leading to sudden death in heavy infections. Both cattle and sheep can harbour chronic infections for months or even years if left untreated. Chronically infected animals may show no obvious signs, yet such infections can adversely affect productivity by reducing fertility, growth and milk yields. It is also important to consider the risk of Black disease at this time of year (figure 3). Both sheep and cattle infected with Liver fluke are predisposed to this fatal disease.
Figure 3: In spite of the seemingly unfavourable conditions, fluke infection is still being detected in cattle this season (left). Photo courtesy of Control of Worms in cattle Sustainably (“COWS”). Risk in cattle (and sheep) of Black disease (right) increases significantly in animals infected with Liver fluke. Photo courtesy of Ben Strugnell, Farm Post Mortems.
Risk of infection can be reduced by identifying high-risk fluke pastures and avoiding grazing these during peak risk periods. Mud snails are generally found in damp, muddy areas (figure 2). Cattle farmers grazing sheep on their pastures overwinter should bear this in mind when selecting which pastures to graze them on.
Advised actions include:
Figure 4: In sheep, acute fluke infection (left) is caused by juvenile flukes migrating through the liver. Chronic fluke infection (right) is caused by adult flukes living in the bile ducts.
Where fluke infection is identified:
The larvae of many disease-causing roundworms, particularly Trichostrongylus species, which may continue to be a risk in store and replacement lambs and, sometimes, yearlings into the winter (figure 5). 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, as the weather becomes colder, newly acquired larval infections of abomasal roundworms (including Haemonchus and Teladorsagia) will begin to encyst, 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. Such infections can be targeted over the winter with treatments effective against arrested larval stages. Such products are available across most major worming groups. For more information on anthelmintic selection and treatment options please speak to your vet or SQP. It should also be noted that in the case of such infections FECs can be negative.
Figure 5: Trichostrongylosis 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 6). Infestations cause loss of condition, secondary skin infections and eventually death if not treated. 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 7). 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 6: 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; figure 6) and may present in a similar way to scab. Lean or emaciated sheep tend to be most greatly 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 products containing either a 3-ML or 1-BZ anthelmintic is recommended at housing. These products are effective against encysted stage larvae acquired in the latter stages of the grazing season. If untreated, heavy burdens of encysted larvae can cause type-2 ostertagiosis in later winter or the following year due to triggered mass emergence. Due to the short time spent at pasture and likely minimal quantities of grass consumed, Autumn born calves are unlikely to require any anthelmintic treatment. As with sheep stomach worms, encysted Ostertagia burdens cannot be assessed by worm egg count.
Group 3-ML pour-on preparations have the added advantage they are also effective against both sucking and chewing lice, infestations of which are not uncommon in cattle during winter housing (figure 8).
Figure 8: Pour-on preparations of 3-ML wormers are also effective in controlling sucking and chewing lice.
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