Lungworm becoming more prevalent in Scotland – how to control

That is the advice of veterinary adviser Dr Kat Baxter-Smith from MSD Animal Health, who says there are five key things farmers need to bear in mind when thinking about lungworm control:

1. Lungworm is becoming more prevalent

Since the mid-1990s, cases of lungworm have increased, particularly in the north of England and Scotland. The disease is also no longer just a youngstock disease and is becoming more common in adult cattle.

“There are two likely causes of this,” Dr Baxter-Smith says. “The first being a change in climate allowing farmers in Scotland to turn cattle out for longer – up to two months longer in some cases. And depending on their lungworm control methods, these cattle may not be protected for the later part of an extended grazing season.

"We’re also finding vets are becoming more focused on lungworm testing and diagnoses prior to recommending anthelmintic use, which is highlighting the presence of lungworm more.”

2. Incident costs are enormous

If you do see a lungworm outbreak, the costs can be significant. The overall cost of an incident of lungworm is conservatively estimated at £140 per adult cow in a dairy herd. Decreases in milk production – estimated at 4kg per cow per day, takes up 50% of the costs, says Dr Baxter-Smith, with the other half of costs coming from laboratory fees, treatments, extra inseminations and the disposal of dead animals.

“What’s more, lungworm can have knock-on effects on overall cow health and performance – potentially resulting in low fertility, lameness, mastitis and other secondary infections. It can also lead to long lasting production losses due to severe, irreversible lung damage.”

3. Coughing isn’t always the first clinical sign

Coughing and rapid breathing are often said to be the first clinical signs of lungworm in cattle. However, production decreases are typically the first indicator in adult cattle.

“It can be up to a fortnight from the time cows become infected with lungworm to when they begin coughing and breathing heavily. But quite often we see milk production drop almost overnight – serving as the first sign of disease. It’s not common, but sudden death can also occur. Cows that have suffered from lungworm two to three times before are most at risk to sudden death due to anaphylactic reactions,” says Dr Baxter-Smith.

Lungworm is becoming more prevalent and farmers should consider control before turnout in spring

4. Your current worm control regime may be decreasing cow immunity leading to more cases.

Long lasting anthelmintics (aka preventative wormers) tend to be administered as a pour on or bolus to treat the whole herd prior to turnout. But this approach may not give first season grazers the parasite exposure they need to build up immunity.

“We are finding that long lasting anthelmintics are quite often the culprits behind immunity issues. Cattle actually have the ability to build immunity against lungworm, but to do that they must have controlled, low-level exposure to lungworm," she says.

Since some long lasting anthelmintics can wear off before cattle vacate contaminated pastures, some animals still at grass can face a high worm burden later in the season and be vulnerable to infection.

5. Vaccination is essential for effective long-term control

While preventative wormers have their place in practice, Dr Baxter-Smith suggests they should be used sparingly on a case-by-case basis. What producers should be doing instead to manage the lungworm threat is to vaccinate first season grazers and naïve cattle alongside sound grazing management for more effective long-term control.

“Lungworm vaccination contains irradiated lungworm larvae that work their way to an animal’s lungs the same way normal lungworms would if ingested through grazing. As a result, vaccinated cattle may still develop the signature cough temporarily when the larva reach the lungs. However, because the larvae are irradiated, they can’t fully develop, which allows the animal to kill them off and develop enough immunity to get them through the year.”

Dr Baxter-Smith confirms that effective lungworm control is best led by vaccination and sound grazing management, with anthelmintics only being used as and when required, based on diagnostics and veterinary advice.

“When incorporating a vaccination programme for youngstock and adult cattle, there are a variety of issues to consider, so it is important Scottish farmers work with their vet at this time of year to develop an effective strategy,” she advised.