Prepare for lungworm threat in cattle warns parasite forecast

Unvaccinated animals of all ages may be at risk, but clinical husk will be more likely in youngstock that are not part of a strategic worming programme, and naïve bought-in cattle that are introduced to herds where lungworm is a recognized problem.

Sioned Timothy, veterinary adviser for Merial, said: “Coughing, particularly during activity, is often the earliest sign of husk, but this can rapidly progress to severe respiratory disease, particularly if the pasture challenge is high. Farmers should be vigilant for signs of lungworm, particularly on farms with a history of disease: husk should be suspected in any cattle coughing at grass whatever their age. Early diagnosis and treatment is key to achieving the best outcome.”

Cattle infected with lungworm will rapidly lose condition, and dramatic milk drops can occur in lactating cattle. This can result in pronounced production losses that will be compounded in outbreaks where deaths occur.

Animals that were not vaccinated prior to turnout are at risk of infection. Last year saw a high number of cases across all age groups of cattle. Overwintered larvae and those shed by carrier cattle may contribute to the pasture challenge in the coming months which could result in outbreaks later in the year, particularly if the weather turns warm and wet – encouraging larval dispersal and development. Where husk is suspected, farmers should consult their vet or animal health advisor to ensure that effective treatment of the whole group is implemented as soon as possible.

“Strategic worming programmes using broad-spectrum wormers such as those containing ivermectin (IVOMEC® Classic, IVOMEC® Super - which also contains clorsulon) and eprinomectin (EPRINEX® ) to control gutworms, will also control lungworm,” said Ms Timothy.

“Where no strategic programme is in place, farmers should treat all individuals in the affected group once lungworm is diagnosed. Group 3 wormers are effective against all parasitic stages of lungworm. IVOMEC® Classic, available as an injectable or pour-on formulation, provides a flexible treatment option for youngstock, whilst EPRINEX® is particularly suitable for dairy cattle, as it has the benefit of a zero milk withhold.”

Incidents of clinical parasitic gastroenteritis (PGE) peak in cattle during August and September. If implementing a strategic treatment programme such as IVOMEC® treatment at 3,8 and 13 weeks after turnout, it is critical that cattle remain on the same pasture for the entire grazing season or are moved to lower risk ground, such as silage aftermath. Untreated animals should not be introduced to the group as this will increase the risk of disease.

In sheep, lambs on safe grazing should not require worming until around three to four months of age. Those grazing contaminated pastures will become increasingly at risk of PGE from a build-up of infective larvae on the grass, as the season progresses.

Timing of initial worm treatments will depend on a number of factors including the treatment given to ewes at turnout, grazing conditions, stocking density and the weather.

Weather plays an important role in larval loading on pastures. Larval challenge reduces during hot and dry weather, but warm, wet weather can increase the numbers of active larvae on pasture and pose a risk to growing lambs.

Ms Timothy said “Lambs should be monitored throughout the season to allow effective management of parasites, minimising their negative impact on production. Pooled facial egg counts (FECs) from around 10 lambs will help guide the need for, and timing of, worm treatments. Alternatively a targeted approach can be taken, where lambs are weighed and only those failing to meet expected growth rates are treated.”

Rams should not be overlooked. They may establish significant worm burdens which will impact on their health and productivity. With tupping rapidly approaching, now is a good time to assess the risk and treat accordingly.