The latest NADIS^* Parasite Forecast sponsored by Boehringer Ingelheim highlights that the recent warm, wet weather heightens the risk of parasites in sheep and cattle.

SHEEP

A key component of a farm’s sustainable parasite control programme is forward planning to provide “safe grazing” right from the start of the grazing season.

One benefit is that lambs grazing safe pastures with ewes shouldn’t need worming until after weaning.  Ideally, wean lambs onto silage or hay aftermaths that have not been grazed by sheep earlier in the year. By mid-summer any over-wintering larvae will have died off and fields can then be considered ‘safe’.

“Lambs grazing permanent pasture usually require worming to limit build-up of infective larvae later in the season (‘mid-summer rise’).  When lambs are dosed, delay any move onto aftermath to allow the treated flock to become lightly re-infected with worms that were not exposed to the wormer, diluting any worms within the lambs that survived treatment and so reducing selection for resistant strains of worms.”  Suggests Sioned Timothy, Ruminant Technical Manager at Boehringer Ingelheim.

Timing of the move and need for worming treatment(s) for lambs will depend upon grazing history, levels of contamination by periparturient ewes, stocking density and prevailing weather conditions.

Ms Timothy, continues: “Moving weaned lambs onto aftermaths during July and August can reduce the risk of parasitic disease. This simple management practice reduces exposure to the high larval challenge that can build up on pasture. This is one of the most critical components of sustainable parasite control.”

Where aftermaths are not available, performance monitoring using growth rates, or worm faecal egg counts (FECs) on lambs every 2-4 weeks from June onwards, can be used to guide anthelmintic treatments.  Pooled faecal samples from approximately 10-12 lambs in a group can be used for FECs and will help guide the need for treatment.

Follow SCOPS** recommendations by leaving some lambs untreated and monitor treatment efficacy by performing a drench test post-treatment.

Ongoing monitoring of wormer efficacy is increasingly important.  The cheapest and simplest way is to perform a drench test to check anthelmintic efficacy.  Ask your vet or SQP for advice.

Prolonged local dry weather during summer can delay larval challenge to lambs grazing contaminated pastures, but infectivity will return in wet weather.  It’s important to remember to include rams in the farm’s parasite control programme because they may have increased susceptibility to PGE (Parasitic gastroenteritis).

Also, if rams often graze the same field every year a significant build-up of infection will occur.

Targeted Selective Treatments (TST)

Those in good body condition and those performing well can be left untreated.  In general, only 40-60 per cent of lambs require worming. This strategy greatly reduces the likelihood of selecting for resistant strains of worms as it allows a pool of unselected parasites to pass eggs onto pasture known as ‘refugia’. This, in turn helps to maintain wormer efficacy in the longer term. Target anthelmintic treatments at lambs that fail to meet expected growth rates.

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Regular weighing also identifies poor growth that may be caused by overstocking or trace element deficiencies.  

Fly Strike

Blowfly strike affects around 80% of UK sheep flocks each year. Female flies are attracted by the odour of decomposing matter such as wounds or soiled fleece.  Preventing diarrhoea caused by worm infections will greatly reduce the risk of blowfly strike on the breech.

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CATTLE

Strategic worm control in cattle is usually applied to autumn or winter-born weaned calves in their first grazing season, and in spring-born beef suckler calves in their second grazing season. Wormers should always be administered following the COWS 5 R’s*** principles – Right product; Right Animal; Right time; Right dose; given in the Right way.

Cattle receiving strategic anthelmintic treatments in the early part of the grazing season should remain on the same pasture for the entire grazing season or be moved to safe pastures e.g. aftermaths, as they become available.

Even low levels of worm infections can reduce growth rate by around 30% in beef calves and replacement dairy heifers. In dairy cows, worm infections can cause a drop in milk yield of 1kg per day^.  In severe infections, there is ill-thrift, loss of body condition and diarrhoea.

Ms Timothy says: “Calves in their first grazing season are most at risk of disease, and heavy worm burdens will cause ill-thrift and potentially severe scouring. Not only that, we know that gutworm has a potential impact on future performance, particularly fertility. Sub-clinical growth checks mean heifers take longer to reach target weight for first service, and can take longer to get in calf, with multiple inseminations often required.

“Despite popular misconception, adult cows will become infected by gutworm, though they carry lower worm burdens, shed fewer eggs and don’t show outward signs of disease. However, the effect on productivity is well documented; milk production decreases by at least one litre per day in affected animals and the additional potential for reduced fertility with increased calving to conception ratios reduces overall performance.”

Lungworm

Lungworm disease (‘Husk’) can appear from June onwards in unvaccinated calves, cattle without an effective anthelmintic programme, and naïve adult cattle.  Adult dairy cattle that have not built up immunity through natural challenge in previous years are also susceptible to lungworm.

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Early signs include coughing, initially after exercise then at rest, increased respiratory rate and difficulty in breathing.  Affected cattle rapidly lose weight and body condition and should be removed from infected pasture and treated as quickly as possible.  Adult dairy cows may show a sudden and dramatic drop in milk yield.

Cattle observed coughing or showing the signs of potential lungworm infection should be investigated by the farm’s vet and prompt treatment with a suitable, fast-acting, zero milk withhold wormer, such as EPRINEX^® Pour On may be advised, depending on the diagnosis.

NADIS parasite forecast www.nadis.org.uk/parasite-forecast.aspx

SCOPS www.scops.org.uk/

COWS www.cattleparasites.org.