14 January 2000

Wormer muddle causing rise in lungworm cases

By Jessica Buss

MANY herds remain at risk of costly lungworm outbreaks, with poor awareness of the diseases effect on adult cattle.

An Intervet-sponsored ADAS study calculates the cost of an outbreak in a 142-cow herd, in which heifers introduced to the herd are infected by cows, at £5857 or £41 a cow in the herd.

Lungworm reduces lactation yield and fertility, says ADASs Nick Holt-Martyn. Added to this, it must be treated and any lost animals replaced

"But even when a heifer suffers lungworm in its first lactation and then recovers it will yield 5% less in its lifetime. For a 6000-litre heifer, this will reduce her lifetime profit by £53."

Long period

He estimates that vaccinating for 27 years equals the cost of a lungworm breakdown. "Its such a long period that it must be worth vaccinating."

In a recent Intervet-commissioned survey of 100 producers either stopping or starting vaccination within the past two years, those stopping often did so to save costs. But both producers who had stopped spending on vaccine and those recently starting to use vaccine were spending about the same on worm control – £10 a head, says the companys Ian Mawhinney.

Those stopping lungworm vaccination were saving half of the £10 budget for the animals second grazing season, suggesting they believe this is more worthwhile than vaccination.

Vet Lab Agency parasitologist Graham David says second season worming is a management practice started in the mid-1980s.

A VLA study of farms with a lungworm outbreak in adults showed that most used wormer in the second grazing season. "Worming in the second year breaks the cycle of animals living with a low level of infection which they need to build up immunity, together with vaccination."

A decrease in vaccinations is also likely to contribute to lungworm outbreaks, he says. Vaccine sales have decreased by 75% since the early 1980s, much faster than cattle population is declining.

Incidence of lungworm outbreak has been five to 10 times higher in the past three years compared with the 1970s and 1980s, with about 500 recorded outbreaks, says Mr Mawhinney.

Most of these outbreaks have been in cattle over 18 months, rather than in youngstock as was more common in the 70s, says Mr David.

But a third of new vaccine users and 44% of lapsed users were unsure or did not think it was a disease of adult cattle, despite the increase in adult cattle cases, says Mr Mawhinney.

"However, half those starting to vaccinate did so because of a recent lungworm problem."

There is also still confusion about the effect of wormers on lungworm immunity. The survey showed 46% of producers stopping vaccination expected to gain immunity from using wormers.

"In reality wormers cannot produce immunity and generally all wormers have a negative effect on immunity. Only one-third of those stopping vaccination and relying on wormers realised protection against lungworm ran out when the wormer ran out."

Mr David points out that some wormers are active for 135 days – a whole grazing season – and while offering protection from lungworm infection, they allow no immunity to develop.

"Pulse release wormer boluses theoretically offer more opportunities for immunity to develop, but we cant say whether they help immunity because it depends when cattle are exposed to lungworm." Lungworm is unpredictable compared with gutworms, which follow a known life cycle.

Mr Mawhinney says pulse release boluses are the most commonly used product by those no longer vaccinating who thought animals would gain immunity from wormers.

Mr David advocates vaccination to ensure lungworm immunity. It can now be given to cattle at different ages and doses to boost immunity, making it more flexible than in the past. "Discuss the best policy for your herd with the farms health adviser." &#42

LUNGWORM

&#8226 Outbreaks costly.

&#8226 Producer awareness poor.

&#8226 Wormer effect confusion.