Early to mid-March saw high levels of rainfall with storms Freya and Gareth bringing particularly wet and windy weather. Temperatures were mostly mild, with cold spells, sleet and snow further north. From March 18th conditions were generally mild, settled and dry.
The provisional UK mean temperature in March 2019 was 6.8 °C, 1.3 °C above the 1981-2010 long-term average. Regionally, above average temperatures were observed across all areas both in March and for the previous 3 months from January-March. Unlike most of the winter months, March also saw relatively high levels of rainfall, 140% of the long-term average. This was the case across all regions in March, although the longer-term 3 monthly average rainfall still shows below average rainfall for all regions except Northern Ireland, NW England and N Wales due to the relatively dry months of January and February.
Due to the unseasonably warm temperatures in February and March, this year’s NADIS Nematodirus forecast has predicted a very early hatch, with peak risk likely to have occurred across most of the country at this time. Similarly, the SCOPS Nematodirus forecast has been predicting increasing risk to “high” and “very high” in many locations throughout April.
Unlike most PGE-causing roundworms, Nematodirus battus infection passes directly from one season’s lamb crop to the next meaning pastures grazed by last season’s lambs should be considered high risk. Eggs survive on pasture over winter and develop the following spring in response to increasing temperatures. The resulting mass emergence or “peak hatch” period of infective stage larvae is what is predicted in the above forecasts. Risk of disease (nematodirosis) is generally greatest if peak hatch occurs at the same time lambs are starting to graze extensively, typically 6-12 weeks of age. Whilst the early predicted hatch this year is likely to have happened before many lambs are this age it is important to remember that in wet, cool conditions infective larvae can survive on pastures for several months. Consequently, “high risk” pastures may potentially remain a risk to grazing lambs into the summer.
Advised actions include:
Figure 1: Nematodirus battus infection can cause sudden onset, severe diarrhoea in first season lambs often with characteristic soiling around the back end. Soiled back ends are also a common site for blowfly strike
Infected ewes will show little or no obvious signs of disease, but can have very high worm egg counts around lambing time (referred to as the periparturient rise or “PPR”). Disease generally occurs in lambs later into the grazing season as pasture contamination accumulates.
Advised actions include:
Figure 2: Faecal egg counts are a useful way of evaluating various parasitic infections. This method can be used to identify Nematodirus eggs (N.b) and those of other PGE-causing roundworms (Str.) as well as coccidial oocysts (arrows).
Another parasitic disease of importance in growing lambs is coccidiosis. This is caused by protozoal (single celled) parasites and the rapid accumulation of their infective “oocsyts” in the environment leading to overwhelming infection and disease. Unlike roundworm infections, coccidiosis can affect housed animals as well as those at pasture (Figure 3).
This disease is commonly associated with high intensity husbandry systems and stocking densities as well as stress factors such as poor colostrum supply, adverse weather conditions at wet muddy paddocks previously grazed by sheep and/or extended housing periods.
Coccidiosis typically affects later born lambs aged 4-8 weeks. Signs include anorexia, weight loss, diarrhoea (with or without blood) and death in severe cases. Due the similarities in presenting signs and ages of affected animals, in grazing lambs it is important to determine whether coccidia or Nematodirus infection is present and causing disease. Coccidial oocysts can be detected in faecal egg counts (Figure 3). Further testing to determine if these are a disease-causing species is also advised when deciding whether or not to treat.
Figure 3: Unlike PGE caused by roundworms, coccidiosis can affect both housed and grazing lambs.
To reduce risk of disease outbreaks:
As new adult flies emerge in the spring and become active it is important to consider blowfly strike and plan accordingly. Fly strike caused by blowfly maggots, commonly greenbottles (Lucilia sericata; Figure 4) is a hugely important disease in terms of its animal welfare and economic impact. Blowfly strike affects around 80% of UK sheep flocks each year, with an estimated cost of £2.2 million per annum to the UK sheep industry through loss in productivity, fleece damage, treatment costs and death in severe cases.
Figure 4: Blowfly strike is caused by adult female greenbottles laying eggs in wounds and soiled fleece. Maggots then hatch and cause extensive damage.
Female flies are attracted to odours produced by decomposing matter. Soiled back ends resulting from PGE (Figures 1 & 3), foot rot lesions (Figure 5), dermatophilosis (lumpy wool), urine scalding around the prepuce and shearing injuries are all common sites for fly strike. Failure to treat even very small lesions promptly is a welfare issue and can lead to disrupted grazing, loss of condition, secondary infections and death.
Disease severity depends upon a variety of factors including weather, with warmer, humid conditions favourable. As was the case last year, NADIS produces a blowfly alert based on daily temperature and rainfall data and updated every 2 weeks over the course of the grazing season.
Figure 5: Wounds and footrot lesions are a common site for blowfly strike
Advised actions include:
If practicing set stocking with strategic anthelmintic dosing to control PGE in grazing calves and young stock:
If taking a “wait and see” approach to PGE control in youngstock:
For more information on treatment and control options for PGE in cattle, please speak to your vet or SQP or visit the COWS group website.
Figure 6: Common signs of PGE in young stock include loss of appetite, body condition and diarrhoea.
On farms with a history of lungworm infection, vaccination offers a valuable tool for protecting against disease in calves.
As temperatures increase, fly and tick activity will resume. These pests can cause their own problems and irritations for cattle, but also lead to additional health concerns:
Figure 7: New Forest Disease (“pink eye” or infectious bovine keratoconjunctivitis) is a potentially serious bacterial infection of cattle which can be spread by nuisance flies.
Control of ectoparasites, in particular ticks, can be problematic. However, options are available:
For more information on ectoparasite control please speak to your vet or SQP and see the COWS group website.
Due to the mild winter, development of liver fluke on pastures may have continued later and longer than usual. Consequently, treatments given during the “usual” risk period in autumn may not have been effective in controlling disease, with deaths caused by chronic fluke infection currently being reported in some areas of the UK (Figure 8).
Advised action include:
Figure 8: Chronic liver fluke in a shearling ewe at lambing. Presenting signs were poor condition; this was the 3rd death in a group of 200. April 2019, North York Moors (Photo credit: Ben Strugnell, Farm post mortems Ltd.)
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