WARNING: Due to the record temperatures reached in February, NADIS wishes to highlight the SCOPS Nematodirus forecast, which is currently predicting moderate risk in many parts of the UK. In such areas, peak risk could occur within the next 2 weeks if conditions remain favourable. NADIS produces its own Nematodirus risk forecast from mid-March onwards. Due to these unprecedented circumstances, however, it is possible that hatch may have already occurred in some areas by this time. We therefore encourage farmers, vets and SQPs to check for Nematodirus risk in their area using the SCOPS forecast to avoid being caught out by disease outbreaks earlier in the season than would usually be expected.
The relatively mild start to January was replaced by colder conditions in the second half of the month with occasional milder interludes. Frost and snow were widespread between the 17th and 23rd and also towards the end of the month.
The UK mean temperature in January was 3.7 °C, which is equal to the long-term monthly average (1981-2010). Regionally, expected monthly temperatures were observed across all regions except Northern Ireland, where the average monthly temperature was around 1oC above its long-term average. However, the trend of above average temperatures over the preceding three months (November – January) has continued.
January 2019 was another relatively dry month, with 52% of average rainfall overall, making it the 9th driest January in a series from 1910, and the driest since 2006. Below average rainfall for January was observed across all regions of the UK and the previous three months (November – January) with the exception of southern England and Wales.
Due to the recent cold weather, development and emergence of liver fluke on pastures is likely to have arrested. However, previously contaminated pastures will remain infective into the coming season. Grazing of such pastures at this time can cause reinfection, increasing the risk of pasture contamination with fluke later in the season.
Animals which grazed high-risk fluke pastures towards the end of last season may be affected by chronic liver fluke caused by adult flukes residing within the bile ducts of the liver (Figure 1). Such infections often present with few or no obvious signs of disease, yet can negatively affect health, welfare and productivity. Chronically infected sheep and cattle can remain infected for months or even years if untreated, making them an important source of pasture contamination for the coming season.
Figure 1: Chronic liver fluke (fasciolosis) is caused by adult flukes residing in the bile ducts of the liver. Such infections may show no obvious signs of disease, yet can have a profound negative impact on health, welfare and productivity.
Advised actions include:
Figure 2: Chronic fluke infection can be identified through egg sedimentation using either individual or pooled faecal samples.
Where fluke infection is identified:
For more information about how best to implement the various treatment and control options and conduct efficacy testing on your farm, please speak to your vet or SQP.
In pregnant ewes, as lambing approaches the so called “periparturient rise” (PPR) in worm egg count begins to take effect. This is caused by a suppression of the ewe’s immunity around lambing that affords their gut nematodes a temporary period of increased egg production (Figure 3). If such animals are not treated ahead of turnout this can lead to heavy pasture contamination and higher risk of disease in lambs for the coming grazing season. It is important to consider both timing and choice of worming products when treating PPR, as treatments strategies must balance the reduction of pasture contamination against selection for anthelmintic resistance.
Figure 3: The “periparturient rise” in ewes is the increase in daily egg output in pregnant animals that occurs around lambing. Whilst this has little to no impact on the health of ewes themselves, the increased egg output is an important source of pasture contamination and subsequent risk to their lambs.
It is important to consider nematodirosis (disease caused by Nematodirus battus) ahead of the current grazing season. Unlike other gut nematodes, Nematodirus infection passes directly from one season’s lamb crop to the next. Pastures may become highly infective in a short space of time due to favourable conditions leading to mass hatching and emergence of infective stage larvae. If this mass emergence or “peak hatch” occurs at a time when lambs are starting to graze extensively, typically around 6-12 weeks of age, this can lead to widespread and severe disease characterised by sudden onset diarrhoea, dehydration and death. Affected animals normally present with heavily soiled back ends, lack of appetite and a profound thirst (Figure 4). It is therefore important to identify potentially contaminated pastures and avoid grazing lambs on these during peak risk periods for disease. Both NADIS and SCOPS produce risk forecasts for Nematodirus based on local climatic conditions to help predict when “peak hatch” periods are likely to occur. Due to the record temperatures experienced in February 2019, the SCOPS forecast is already predicting moderate risk for nematodirosis in many parts of the UK, with some cases already confirmed. The NADIS forecast will be available from the end of March. It is strongly advised you consult these forecasts and plan your grazing and parasite control strategies accordingly.
Figure 4: Nematodirus battus infection can cause sudden onset, severe diarrhoea in first season lambs often with characteristic soiling around the back end.
Advised actions include:
Figure 5: 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 disease is caused by protozoal parasites (Eimeria spp.) causing gut damage. Signs of disease typically occur around 4-8 weeks of age and are characterised by anorexia, weight loss, diarrhoea (with or without blood) and death in severe cases. Coccidiosis results from a rapid accumulation of infective “oocysts” in the environment, which can occur both indoors and at pasture. This is commonly associated with high intensity husbandry systems and stress factors such as poor colostrum supply, high stocking densities, adverse weather conditions at wet muddy paddocks previously grazed by sheep and/or extended housing periods.
Due to the similar presenting signs and age ranges of affected animals, in grazing lambs it is important to determine whether Eimeria or Nematodirus infection is present and causing disease. Concurrent infection with both parasites is not uncommon, potentially leading to greater disease severity.
Advised actions include:
Calves and youngstock entering their first or second grazing season are at greatest risk of PGE (Figure 6). It is therefore important to plan around these animals when devising an effective, sustainable parasite control plan for your farm. The COWS group currently recommend one of two options. Choice of strategy is largely dependent upon individual farm objectives and the feasibility of their implementation:
Figure 6: PGE in cattle causes diarrhoea and up to a 30% reduction in the growth rates of youngstock. Commonly affected animals include growing dairy heifers in their first grazing season (left) and weaned autumn-born suckler calves in their second grazing season (right).
Irrespective of which approach is taken, over the course of the grazing season regular performance testing through weight gain, diagnostics (e.g. worm egg counts) and post-treatment efficacy testing are hugely valuable and important tools to ensure your chosen control plan is working. Incorrectly controlled PGE can severely impair performance and productivity in both calves and adult cattle. For more information, please speak to your vet or SQP and see the COWS website (www.cattleparasites.org.uk).
On farms with a history of lungworm infection, vaccination offers a valuable tool for protection against disease in calves (Figure 7). Since the lungworm vaccine is live, it must be purchased fresh ahead of each grazing season. Planning and ordering the number of doses required for your farm well in advance is therefore advisable.
Figure 7: Lungworm infection can be a very serious problem for youngstock. On farms with a history of disease vaccination can be hugely valuable in reducing disease incidence and severity, but must be ordered and planned well in advance.
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