The unseasonably hot, dry weather experienced over the summer months in 2018 has continued into July.
The average temperature for the UK in July was 17.3 °C, 2.2 °C above the 1981-2010 long-term average, making it provisionally the joint second warmest July (alongside 1983, after 2006) in a series from 1910. These above average temperatures also extended to observed maximum and minimum temperatures, which were recorded as 1 – 4oC above the long term averages recorded across all regions of the UK. Combined average temperatures for the preceding 3 months (May – July 2018) were above average across all regions of the UK.
Rainfall in the UK in July was recorded at 71% of average, with particularly dry conditions observed in parts of Norfolk and Cambridgeshire. Whilst still below the long term average for July, other areas of the Great Britain were less markedly dry, while the monthly rainfall in Northern Ireland was comparable to the long term average for the region. Combined average rainfall for the preceding 3 months (May – July 2018) were below average across all regions of the UK.
Sunshine was 138% of average and it was provisionally the sixth sunniest July in a series since 1929, and sunniest relative to normal in England where it was provisionally the second sunniest July after 2006.
The preliminary fluke forecast for 2018 was first published in July, and is based on rainfall and temperature data for the months of August-October 2017 and May-June 2018. This forecast predicts moderate to high risk in the north and west of Scotland, and low risk in most other areas (Figure 1). An updated forecast for Autumn 2018 will be produced later in the year based on temperature and rainfall data for May-October 2018.
Figure 1: Provisional fluke forecast for summer 2018 by region. A risk value >300 is considered moderate. A risk value >375 is considered high. A more comprehensive risk forecast for Autumn 2018 will be produced later in the year.
Development of liver fluke and its intermediate host, the mud snail (Galba truncatula; Figure 2), on pasture is dependent upon temperature and rainfall with warm wet conditions optimal. The recent run of dry weather is therefore likely to reduce risk of liver fluke later in the season. However, as was the case for Northern Ireland in July, where above average temperatures and normal levels of rainfall are present the risk of liver fluke later in the season may increase. Similarly, on farms with permanently wet areas and/or permanent water bodies snails may continue to thrive in the hot weather (Figure 2). Consequently, in addition to the NADIS forecast, risk of fluke infection should be considered on a farm by farm basis, with local rainfall and wetlands taken into account.
Figure 2: A large number of mud snails (Galba truncatula) recovered from a farm in Lancashire, August 2018. While the current dry weather indicates lower risk for liver fluke consideration should be given to on farm conditions relating to local rainfall and wetlands. Photo credit: Bethan John, University of Liverpool.
Acute disease caused by fluke may occur at any time from late summer onwards. This type of infection is more common in sheep, with signs including:
Advised actions include:
All animals coming onto farm should be considered a potential source of drug resistant worms. Where buying in new stock, as is the commonly the case in autumn, quarantine measures should be taken.
For sheep, current best practice advised by Sustainable Control of Parasites in Sheep (SCOPS) is as follows:
To prevent introduction of resistant roundworms and sheep scab:
Where resistant liver fluke is a concern:
For cattle, Control of Worms Sustainably (COWS) guidelines highlight the importance of knowing disease status of purchased animals or their farm of origin.
PGE is a disease of lambs in their first grazing season, resulting from the accumulation of large infectious burdens of gastrointestinal roundworms over the course of the grazing season. Typical signs include:
Pasture contamination peaks over the summer months, falling off into the late summer and autumn. As reported above, the hot, dry conditions experienced over the preceding months are likely to have reduced disease risk by increasing larval mortality. However, certain animals, such as lambs with unknown worm burdens grazing “dirty” pastures may still be at risk.
Figure 3: Emaciation caused by failure to control PGE.
Advised actions include:
Figure 4. Regular weighing of lambs over the grazing season enables targeted selected treatment (TST) for animals which aren’t meeting expected growth rates. This also facilitates accurate dosing by weight.
Due to the ability of female Haemonchus contortus worms to produce huge numbers of eggs, the potential for these to develop rapidly on pasture, risk of haemonchosis should not be ruled out based on recent weather. Cases are sporadic and difficult to predict, with a number of outbreaks have been reported over the summer months.
Most anthelmintic products are effective against haemonchus, although some evidence of resistance to white drenches (1-BZ) has been reported previously in the UK. Some flukicidal products, such as nitroxynil and closantel are also effective.
The recent hot, dry weather is likely to have decreased the survival of larvae on pasture. Larval pasture burdens for most cattle roundworms tend to peak in early to mid-July, although levels of Ostertagia ostertagi larvae can remain high until the end of the grazing season. Young stock in their first grazing season may therefore still be at risk of type-1 ostertagiosis, particularly if set stocked on permanent pasture. Animals should continue to be monitored for signs of disease and/or poor performance.
Advised actions include:
Lungworm infection may continue to be a risk into the late grazing season. Larvae shed by already infected cattle may survive drier periods of weather within faecal pats to be dispersed onto pasture en masse following periods of rainfall.
It is therefore advisable to continue monitoring for signs of disease in at risk animals such as unvaccinated calves in their first grazing season. Early signs of infection include:
Where infection is suspected treat animals with an anthelmintic (most products are effective) and remove affected cattle to “safe” pasture (e.g. aftermath) or house in a well ventilated building. Infection can be confirmed by post-mortem or detection of larvae in saliva or faecal samples. In lactating dairy cattle a milk sample antibody ELISAs is also available. It is also important to consider milk withdrawal periods when treating these animals.
Figure 6. Early signs of lungworm infection include widespread coughing and elevated respiratory rates.
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