Johnes Disease a potential timebomb for dairy sector
Evidence is mounting on links between the bovine disease and Crohns disease in humans
Published 22/06/2016 | 02:30
Johnes disease is possibly the largest skeleton in the Irish dairy industry's closet.Not only is there a growing mountain of data linking Johnes with the debilitating Crohns disease in humans, the spread of Johnes in national cattle herds continues at an alarming rate.
Ireland is no exception. Best estimates until Teagasc complete their survey this year is that one in five herds -in both beef and dairy - are carrying the disease. Globally, it may be closer to 50pc in intensive dairy regions.
Meanwhile, industry insiders speak in quiet tones about loads of Irish milk powder being rejected because of the presence of Johnes cells, and studies carried out by various internationally renowned specialists in this area have repeatedly found viable Johnes cells in samples of infant milk formula from some of the world's biggest brands.
"It's no good pointing the finger at any particular country - the ingredients for these products are often sourced from all over the world," said Mike Collins, a professor in Pathobiological Sciences at the University of Wisconsin.
He has focused a lifetime's work on the disease since the 1980s, and will be chairing one of the key sessions on this subject at the World Buiatrics conference to be held in Dublin in early July.
"I think it's fair to say that every major dairy exporting country in the world has a problem with Johnes. We've had it in the US since the 1900s, and now it's effectively endemic because it is present in 91pc of dairy herds," he said.
He believes that any country that expanded its herds over the last century bought in the disease, with the US and Australia being some of the first, followed by Chile in the 1950s, and more recently China as it goes through a major expansion of milk output.
"Some of the positive herds may have an incidence rate of 40pc, when clinical cases are obvious, but more herds will be exhibiting no signs of the disease even though 5-10pc of the cows will actually be carrying the infection," said Mr Collins.
He believes that the evidence linking the disease to the similar human wasting condition, Crohns, will only continue to mount.
"There is a major clinical trial here on a new antibiotic for Crohns. If it proves successful, it will be a major new piece of incriminating evidence to link the two conditions," he said.
The expert added that Ireland is a high risk region for the spread of Johnes now as dairy farmers attempt to rapidly expand.
"With quotas gone, farm businesses will either expand or get out of business. A lot of that expansion is likely to happen through buying in stock, sadly, without enough biosecurity. If you buy enough, sooner or later, you're going to buy in Johnes," said Mr Collins.
He believes this is the reason that larger, more "progressive" herds are the ones that have suffered initially with the disease. Despite Ireland being "behind" on tackling the disease, the US professor thinks that we can learn a lot from countries such as Australia, Holland, Sweden and Denmark.
"Sweden are the world leaders with a verifiably Johnes-free herd. Ironically, the EU is resisting the Swedish authorities' attempt to impose import restrictions on animals from Johnes-positive herds.
"The Danes are also to be commended for being quite open about the issue. They are lucky in that they are a small industry that is vertically integrated so it is relatively easy for them to implement a national programme.
"The Dutch programme doesn't stand up to much scientific scrutiny but at least they test every cow, while the Australians have done a very good job with comprehensive programmes for every species," he said.
He says that processors should be more proactive in dealing with the issue, but that they are "afraid to break ranks".
"The cost of eradicating Johnes should not be heaped on farmers because the reality is that farmers with low incidences of the disease in their herds will not see any major improvement in their profit by tackling the disease.
"It takes 8-10 years to get a herd free of Johnes. The US government threw $260m (€233m) over 10 years at the disease, but when state funding stopped, herd participation also stopped.
"This proves that Johnes is not actually a very costly disease for the farmer, but if it ever becomes an issue beyond the farm gate, then everyone will have to pony up," he said.
€500m project to tackle Johnes
The Irish government have sunk nearly €500,000 into a pilot project aimed at getting farmers to tackle Johnes, mainly through Animal Health Ireland (AHI), who have a wealth of resources available online.
Over 1,400 farmers started off in the programme, but the dropout rate among farmers that found their herd testing negative was high. But as Prof Michael Collins notes, Johnes is a "sneaky" pathogen that spreads slowly but silently through a herd long before animals start showing clinical signs.
One of the farmers that has been through the wringer with the issue is a 400 cow dairy farm in Co Meath with over 80pc of the herd calving in the spring. In the late 1990s, a major TB outbreak resulted in the entire herd of 180 cows being replaced over the course of three years with imported stock.
By the early 2000s they began to see sick animals that were scouring and becoming thin. Initial veterinary advice said it was a problem with parasite control, resulting in no progress.
Things began to change when the farm joined a Johne's disease control programme in 2005. In the first round of blood testing revealed that 60 animals were positive - almost 40pc of the herd. When added to the culls over the next seven years, an average of 20 animals were culled annually during this period.
As part of the programme two blood tests were taken per year with random faecal sampling every two years. It was estimated that the disease was costing the farm up to €30,000 each year.
Through the programme, the farmers to learn how to tackle Johnes, including the construction of individual calving and calf pens.
Since then the herd has grown to 400 cows, but the efforts to eliminate the disease continue.
The farm continues to calve all their cows in individual pens and these pens are washed out and disinfected after each calving.
Each new-born calf is given two feeds of colostrum from their own dam or from a test-negative cow before moving them on to milk replacer. No slurry is spread on the calf grazing area.
The levels of Johnes in the herd prevalence has gone from 40pc to 2pc, with zero clinical cases. In order to push for full eradication, this year they concentrated on snatching calves within 10 minutes of birth, which required all the calvings to be monitored.
The annual blood test is now taken in December to identify all the positive cows before calving. These animals are isolated and they cull both the positive cows with high readings and their heifer calves.
The efforts have resulted in improved fertility and a significant reduction in the use of antibiotics, but it will be some years before the farm will be Johnes free.
Understandably, these farmers feel that every farmer should know their infection status, and that the pilot programme was worthwhile.
But they also want farmers that go through this process given formal recognition, and claim that compulsory testing would benefit all.