Lungworm disease in cattle set to peak in August

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Lungworm disease in cattle will reach its peak during August and farmers are urged to look out for the early signs in their cattle before outbreaks of severe disease occur.

The August NADIS Parasite Forecast, sponsored by Merial Animal Health, advises farmers to be vigilant for the early signs of husk which include coughing during periods of activity, a reduction in milk yield and loss of condition.

Early signs of disease can be seen as soon as one week after initial infection as the maturing larvae first reach the lungs. At this stage diagnosis is often based on clinical signs, since larvae will not be present in the faeces until they develop into egg laying adults approximately two weeks later. Once husk has been diagnosed immediate treatment of all cattle in the group is required to clear the infection and protect animal productivity.

Sioned Timothy, veterinary adviser for Merial, says: “Young cattle during their first grazing season are most at risk from husk, but cases are increasingly seen in adults, so all ages of cattle should be monitored for signs of disease.

“As soon as coughing is observed, or any other signs are detected, it’s vital to seek advice from a vet or SQP. This will ensure appropriate investigation, diagnosis and treatment takes place as soon as possible.

“Husk can be prevented either by vaccinating before spring turnout or through strategic worming with a suitable product.”

Due to the unpredictable nature of husk a planned approach to control is advisable. This should take into account local risk factors such as climatic conditions and the farm’s own parasite status, and also address the risk posed by bought-in animals of unknown lungworm status.

The overall aim of control measures should be to minimise the risk of clinical disease, whilst allowing sufficient low level exposure to the parasite to promote protective immunity. This can be a delicate balancing act; too little exposure and they don’t develop the immunity required, while too much will cause clinical disease and production losses. To further complicate this situation, even immune cattle can succumb to severe clinical disease in the face of a high pasture larval challenge, highlighting the need for on-going vigilance throughout the grazing season.

Many wormers used to treat gutworm (Ostertagia ostertagii) such as EPRINEX® (eprinomectin), will also treat lungworm. One treatment with EPRINEX® will clear lungworm and prevent reinfection for up to 28 days, with zero milk withhold.

In sheep, there has been a reduced pasture larval challenge due to the very dry weather experienced in many regions during June. However, the strategic use of safe grazing wherever possible to minimise the parasite challenge faced by lambs, should play a crucial role in parasite control programmes in the coming months.

After weaning, lambs moved to safe grazing may not need to be wormed for up to six to ten weeks. However, this will depend on the level of worm burden that the lambs are carrying when they are moved, the stocking rate, and weather conditions. Ongoing monitoring of worm burdens by faecal egg counts (FECs) on pooled samples from around ten lambs every seven to ten days can help identify whether a worm treatment is necessary.

“Farmers should also consider adopting a targeted approach to wormer treatment whereby lambs are weighed and only those that are failing to grow at expected rates are dosed,” says Ms. Timothy. “This minimises the number of unnecessary treatments administered, saving time and money and reduces the selection pressure for resistant strains of worm. Farmers should be aware that there are other causes of reduced growth rate, such as cobalt deficiency, that may complicate interpretation if not recognised and addressed, so advice should be sought from a vet or animal health advisor (SQP) before embarking on this approach.”

Blowfly strike will continue to be a major risk during August. Effective internal parasite control will minimise scouring and reduce the risk of strike. Following recent heavy rain, farmers should be alert to flystrike occurring on the back of sheep.

“Strike prevention is the best form of control,” says Ms. Timothy. “Spray-on products containing insect growth regulators (IGRs) will prevent an infestation, but will not kill maggots that are already present.”

Where sheep have already become struck, topical products containing a synthetic pyrethroid (SP), or a diazinon based plunge dip will treat the problem. These products may also provide protection against future blowfly strike and treat other external parasites.

“Farmers should consult their vet or animal health advisor to ensure they are using the most appropriate medicine for the circumstances,” concludes Ms. Timothy.