Success with worm control programmes in youngstock does not necessarily remove the threat from lungworm, commonly known as husk, warns Merial Animal Health.
With July marking the start of the ’lungworm season’, cattle farmers are being alerted to the symptoms and urged not to assume that successful gutworm programmes also eliminate lungworm. The parasite inflicts serious health and economic damage on stock.
"Lungworm is a killer," says Fiona MacGillivray, technical veterinary manager at Merial, "and even mild infections take their toll on health and productivity. It’s important to understand the disease, be aware of the symptoms, and know how to deal with it.
"There is concern that success with other parasite control programmes can produce a false sense of security with respect to lungworm outbreaks," she says. "We’ve rightly been very focused on dealing with youngstock gutworm infections, to good effect. The disease affects cattle of all ages. At turnout, cattle eat larvae, which pass into the small intestine and migrate to the lungs, where they develop into adult worms.
"It’s usually about the beginning of July that the first cases begin to appear. The irritation caused by the worms stimulates the lungs to produce large quantities of mucus," Ms MacGillivray explains. "That causes the tell-tale symptoms of breathing difficulties and coughing."
Milk yields in adult dairy cows drop immediately, accompanied by an increasingly rapid loss of condition. Some cattle exhibit hypersensitivity to the worms, which may even result in sudden death.
"A lungworm policy, prepared in consultation with a vet, should be included in every producer’s herd health plan," Ms MacGillivray stresses. "While lungworm is by no means endemic on every cattle farm, it’s essential to know how to deal with it, if and when it appears, and how to prevent it becoming a problem in the first place."
"Dairy farmers should be reassured that EPRINEX, the only wormer approved for lungworm treatment in lactating dairy cows, carries no requirement for milk withdrawal," says Ms MacGillivray.
"Rely on your vet’s advice, but generally two wormer treatments – in summer and again at housing – will be sufficient to see off the lungworm threat," advises Ms MacGillivray.
"Don’t forget the weak link presented by newcomers to the herd," Ms MacGillivray points out. "On a farm where husk is already present, newcomers may be ’naïve’ and carry no immunity to the parasite; conversely, new additions could bring lungworm into a previously parasite-free herd. Each will need managing appropriately – remember that the larvae can live outside the host for up to a year."