An international authority on lameness in pasture-fed cattle fears a disease found in a Taranaki cow last year is already widespread in New Zealand.
Since Inglewood vet Neil Chesterton revealed the discovery in Taranaki of the bacterial infection called bovine digital dermatitis (BDD), vets have been contacting him about possible cases they've seen - up to 20 years ago - without knowing what it was.
He is worried the disease, which causes milk production and fertility losses, will become established in New Zealand - the world's last significant dairying area without it.
Late last year a vet told him he'd seen individual cases of the infection in a 230-cow South Taranaki herd for years. "So on a whim I went and had a look," he said.
Visiting the farm during milking, Chesterton cleaned the back feet of the entire herd with a high- pressure hose. Inspecting the feet with a torch, he found the infection in the form of a small dried-up lesion in 22 animals. Analysis of samples he took were all positive.
He believes it's the first time multiple cases of the infection have been identified in New Zealand.
A second vet who treated a lame cow with a fresh strawberry-like lesion in another South Taranaki herd took a sample that returned a positive test on histology and silver stain. Chesterton found the infection in 17 animals in that 260-cow herd. None was lame and lameness had never been a problem in the herd, but the infected cows reacted to the high-pressure hose on their feet.
He advised the farmers to set up footbaths at their cowsheds' exit.
Chesterton said he doubted multiple cases of the infection were restricted to South Taranaki. "I don't think we've got the only two herds in the country with the infection. Clean, green Taranaki will not be the only area with multiple infections."
He believed it was present in all the country's dairying areas. "Maybe it's always been this way. We don't know."
Either the two farms had always had the infection or the disease was now spreading.
Overseas research showed the infection started with an individual cow and spread to others when conditions were damp and muddy.
On the two farms he looked for muddy areas that could be the site from where the infection spread. "We know it spreads from cow to cow, but we don't know how.
"Neither farmer thought there were other cows in the herd affected by the infection. I just went for the heck of it, not because I thought I'd find an extensive problem.
"If BDD becomes established in a herd, the farmer will forever be doing footbaths and applying topical treatment - at a huge cost."
He's advising vets and farmers to take the disease seriously. Any farmer who sees a cow with lesions like those in the photograph should ask his vet to take a sample for laboratory analysis. If the test was positive, the vet should check for lesions on the feet of the entire herd. Any herd that had similar lesions in the past should also be checked.
He's also asking vets and hoof trimmers to ensure they wash their equipment and their gumboots with lots of water and antiseptic before they visit other farms.
He said British, European and United States vets now working in New Zealand had seen the devastating effect of the disease on herds in their own countries and were relieved to see only isolated cases here. "But those single cases could be the tip of an iceberg - the start of an epidemic."
"I'm glad we have overseas vets who have seen it and who know how serious it can be. Overseas, once it's established, no herd has ever got it rid of it."
Chesterton said cows with the disease could be severely lame at first. While the lameness decreased, the infection often remained and spread to other cows.
A working party consisting of representatives of the Society of Dairy Cattle Veterinarians, the New Zealand Veterinary Association, the Australasian Hoof Trimmers Association, Massey University and DairyNZ has been established under the chairmanship of Ministry for Primary Industries' animal health surveillance expert Daan Vink.
It is considering protocols for vets and farmers who find the disease and is building awareness of the risk factors for its spread. Cattle moving between the North and South islands and young stock grazed off farms were at risk, as were cattle using feedpads and housing, he said.
- © Fairfax NZ News
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