Increased threat of husk in adult cows and unprotected youngstock

Outbreaks of husk (lungworm) in adult beef and dairy cattle, as well as youngstock, are likely to occur across the UK in the coming weeks and months, as recent warm weather followed by rainfall have provided the perfect conditions for lungworm larvae to migrate from dung pats to grass. Sudden outbreaks could be severe and, if the early signs of infection are not identified quickly, significant production losses could occur, including death in the worst cases, warns Merial Animal Health’s Veterinary Adviser Sioned Timothy.

While youngstock are traditionally thought to be more susceptible to lungworm infection and associated respiratory disease, there is an increasing trend for adult cattle to be affected. Immunity to lungworm is short-lived, and if natural boosting through low-level exposure to larvae does not occur, animals may be rendered susceptible to disease when the number of larvae present on the pasture increases. However, even immune animals can succumb to disease in the face of high larval challenge.

Losses of up to £137 per animal can be attributed to lungworm infections and include additional costs and loss of income resulting from reduced milk production, disposal of dead animals, reduced fertility, laboratory diagnosis and treatment costs¹. Even after recovery, lung damage can leave animals susceptible to secondary infections and affect long term productivity.

“The problem for farmers, and vets, is that lungworm can be difficult to diagnose at an early stage and may not be spotted until a full-blown outbreak occurs,” says Ms Timothy.

“The initial signs of coughing can be confused with other respiratory diseases such as Infectious Bovine Rhinotracheitis (IBR), particularly in older cattle, but it’s important not to overlook the risk of lungworm in cattle of all ages as delays in treatment can hit productivity hard. Severe outbreaks can even result in the loss of individual animals.”

A rapid loss of condition and sudden milk drop in lactating animals are often observed during the acute stages of disease. Animals have a deep harsh cough during activity which progresses to coughing at rest, with laboured breathing. Severely affected cattle will typically stand with neck and head extended in the ‘air hunger’ position. Dairy cows may be observed resting more often and drinking and eating less than normal.

Lungworm should always be considered as a potential cause of coughing in cattle at grass. Farmers should not wait until the whole herd is unwell, but seek advice early in the course of disease to minimise the longer term impact.

Vaccinating youngstock and adult cows before spring turnout is an effective method of preventing clinical disease. However, this immunity may wane as the grazing season progresses resulting in late-summer outbreaks when animals experience a high challenge from infective pastures.

In young cattle, lungworm control will also be achieved through the use of strategic worming programmes implemented primarily to control gastro-intestinal parasites such as gutworm (Ostertagia ostertagii).

When using early-season parasite control with products such as Ivomec Classic (ivermectin) after turnout, additional treatments may also be needed later in the grazing season and farmers must remain alert for signs of disease.

“In adults a targeted approach is often used, with wormer treatments administered in response to the early signs of disease,” suggests Ms Timothy. “Vigilance is required for this approach to be effective and ensure cattle are treated before outbreaks of severe disease and associated lung damage occur.  

“Cattle should be treated as soon as possible with a suitable anthelmintic, ideally one which has prolonged activity against reinfection to allow lungs time to recover. It’s vital that the whole herd is treated as some infected animals will not show obvious clinical signs but will still suffer from impaired performance.”

 Merial’s Ivomec Classic (ivermectin) and Eprinex (eprinomectin) wormers can be used as part of a programme for lungworm control and for treating outbreaks, says the company. The active ingredients prevent reinfection for up to 28 days after treatment.

Ivomec Classic injection or pour-on is suitable for use in youngstock and adult beef cattle while Eprinex has zero milk withhold and offers fast and effective control of lungworm in adult dairy cows.

In severe cases, farmers should consult their vet to discuss supportive treatment options to relieve pain, manage inflammation and treat any secondary infections.