The reported incidence of Crohn’s disease in Canterbury, New Zealand has doubled over the past decade, crowning the region with the highest reported incidence globally. Scientists around the world believe environmental factors are contributing to this disconcerting rise. In this investigation, we present the research on a disease found primarily in dairy cattle called Johne’s disease, which has the same symptoms as Crohn’s disease and is recognised on over half of all dairy farms in New Zealand. If the MAP bacteria which causes the immune responses in dairy cattle is tested and found in our local drinking water supplies, our air and our dairy products, we could be facing a public health issue of massive proportions.

Johne’s (“Yo-nees”) disease is a contagious, chronic and sometimes fatal infection caused by Mycobacterium avium subspecies paratuberculosis (MAP). Johne’s disease is found primarily in agricultural ruminants such as cattle and sheep, and is an immune system response following MAP infection which leads to deteriorated bowels. This inability to process nutrients leads to the most obvious signs an animal may have contracted Johne’s such as weakening, weight loss and even death. Most animals are infected during the first months of their life, yet signs of the infection can take years to show.

Crohn’s disease is also a chronic inflammatory bowel disease which has similar symptoms to Johne’s such as weight loss, abdominal pains and diarrhoea, while having no known cure. The number of people who have Crohn’s disease in New Zealand is unknown, but if estimates in the Canterbury region of 26 out of 100,000 can be applied across the country, New Zealand may have some of the highest rates in the world. The two most common age groups diagnosed with Crohn’s are between 15-30 years of age and 60-70, similar to the young and old which contract Johne’s in ruminants.

Research indicates that more than 50 percent of New Zealand dairy farms have stock infected with Johne’s, yet this number could be much higher due to the number of farms unaware they have it. For approximate dairy cattle infection rate comparison, Canada has 9.8-43.1%, Denmark has 80-86%, Netherlands has 20-71% and the United States has 68%.

In 2004, Canterbury had the largest ever reported incidence of Crohn’s disease in the world at 16.5 per 100,000. Using identical methodology in 2014 revealed this number has rocketed up to 26 per 100,000 in just a 10-year period. Co-author of the latest study Andrew Day commented “We’ve seen almost twice as many people being diagnosed over that 10 years and people with Crohn’s Disease have a lifetime of inflammation.”

With such a high rate of incidence in New Zealand, what are the possible contributing factors?

There is a well documented genetic component to Crohn’s disease. Relatives who suffer from Crohn’s are 10-times more likely to be infected by the disease than the general public, increasing to 30-times if the relative is a brother or sister. Although a genetic component to Crohn’s disease is well accepted in the scientific community, it is not considered the sole cause of the disease. Scientists now believe environmental exposure is a large contributing factor.

Some researchers believe exposure to MAP, the bacteria which leads to Johne’s disease in ruminants is the cause of Crohn’s disease at least in some patients. Advances in technology have revealed the presence of MAP in blood, tissues and faeces of Crohn’s patients, leading researchers to believe there is a strong link. In November last year, Washington State University professor William C. Davis and his colleagues published a case report on the link between Johne’s and Crohn’s.

“The findings presented in this case report suggest MAP is zoonotic and can cause disease in humans with the clinical manifestations of both Johne’s and Crohn’s disease, a key point that has been argued for more than 100 years now,” Davis said. “I suspected all along that it was only a matter of time before a patient would be identified that linked Crohn’s disease with an MAP infection.”

Dr Richard Gearry, a Gastroenterologist, professor of medicine at the University of Otago and also author of the original 2004 Canterbury study believes scientists “may be the missing link between whatever is going on in our environment and our risk of getting these diseases.”

Considering exposure to MAP could be the missing link, where is this exposure coming from?

On New Zealand farms, there are many potential pathways for MAP alongside other pathogens such as campylobacter and E- coli to reach our streams, rivers and drinking water supplies as happened in Havelock North. Surface run-off on intensively stocked farms is a major issue, especially during periods of heavy rain or over-irrigation, which results in many of these bacteria and nutrients draining down into waterways. Laneways and ineffective effluent storage facilities also allow a direct route of transmission. Preferential flow pathways are when contaminants travel down through soil layers into aquifers and water bodies, especially in the case of gravelly coarse soils such that 70% of Canterbury’s irrigated dairy resides on. Pathogens such as MAP can survive for longer than 12 months in suitable conditions, and may be present at high densities in biofilms on the insides of pipes and taps. On top of this, MAP has also been shown to resist chlorine disinfection treatment, putting public drinking water supplies at even higher risk.

A 2008 Canterbury study found that intensive dairy farming and the use of border-strip irrigation increased the concentrations of E-Coli and Campylobacter in nearby groundwater, impacting drinking water supplies. Large scale conversion and intensification of agricultural land in Canterbury is clearly linked to decreases in water quality and the resulting increase in waterborne diseases. The result is that in 2015 alone, E-Coli was detected in Christchurch’s untreated water supply 14 times, raising debate on whether the supply should now be treated.


Well sampling sites and inferred shallow groundwater flow directions for each of the five Canterbury Plains aquifers. Source

The majority of the plains have shallow groundwater which is recharged from low-land rainfall directly or via foot-hills rivers. The problem is this recharge can carry with it leached contaminants from the surface and as you can see above , filters through the whole region and into drinking water supplies.

A 2004 report by Food Standards Australia and New Zealand states ‘it is possible that water sources may be contaminated with MAP through the excreta of infected animals (ruminant and non-ruminant). Water running off from grazing lands, or lands that have used manure from infected animals as fertiliser, may therefore contain viable MAP.’ Given the above geographic topography of Canterbury, this should be of great concern to the region.

Another transmission pathway for MAP is through the air. When farmers spread their stored effluent back over farmland through irrigators, this turns any MAP contaminated effluent into an aerosol. Aerosolisation can result in a >1,000-fold increase in numbers of viable mycobacterial cells per millilitre of water droplets ejected, which then can enter the human lung and lead to infection.

There has been scientific comparisons between the high rate of incidence in Canterbury to the situation in Cardiff, South Wales UK where a high incidence of Crohn’s disease has been linked to exposure to MAP bacteria in aerosol droplets. Cardiff is a seaside city at the end of the river Taff which runs through rich agricultural pastures, similar to how Canterbury populations are down river from large scale agricultural land use. The data suggests the clustering of Crohn’s in Cardiff may have been from inhalation of MAP due to the prevailing southwesterly winds past the river Taff. Inhalation is a hypothetical route of MAP exposure in ruminants, just as pulmonary involvement is documented in some adults that suffer from Crohn’s.

Canterbury is known for it’s strong northwest winds, acting as a disease delivery system blowing irrigation and dust MAP aerosols across the plains and into population dense areas, massively increasing exposure to MAP.

MAP can also be made airborne through dust particles from animals that are shedding the disease. In one study, dairy cattle shedding MAP were introduced to a barn to see how far the pathogen will spread. The result was ‘widespread contamination of the internal and external environment of a dairy barn, including the presence of viable MAP in settled dust particles suggesting potential transmission of MAP infection through bio-aerosols.’

Another potential exposure pathway is through the consumption of dairy products. Studies testing how effective pasteurisation is at killing MAP have found small percentages can still be viable even after reaching the required temperatures and duration under normal process.

Studies concerned with the detection of MAP from dairy products on retail sale included in the systematic review

Studies concerned with the detection of MAP from dairy products on retail sale included in the systematic review.

Looking at the table above which shows detectable levels of MAP and then the corresponding percentage that is viable and can be cultured, these studies show it is likely viable MAP is present at low levels in commercially pasteurised cows’ milk and other dairy products in New Zealand.

With the majority of the studies overwhelmingly and definitively supporting the role of MAP in at least 30%-50% of Crohn’s disease patients, New Zealand could be facing a public health issue of massive proportions. With enough public outcry, New Zealand local councils and district health boards will be forced to start testing drinking water supplies for MAP bacteria as well as testing the air for aerosol pathogens and dairy products for viable bacteria. If MAP is detected at viable levels, there needs to be urgent action taken for the safety of the public given the proximity of large-scale intensive farming and population centres.

We need to be collectively concerned about Johne’s disease and treat it as a zoonotic disease as a precautionary measure until more is known about the high rate of Crohn’s incidence in New Zealand.


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5 Responses

  1. Linda Pocock

    My neighbours son is Christ hurch born and bred .
    At 23 after a long period a
    Of illness and discomfort he has been diagnosed with terminal bowel and liver cancer.
    Why is the media message perpetuated that nitrates in water only affect babies?Yes adult blood does not seem to be harmed in same way BUT Google affects on adult health and high blood pressure especially reproductive women and gut and liver cancers all feature as caused by the nitrosamines formed in the gut when bacteria convert the nitrates to nitrites then on to well documented carcinogens, nitrosamines.

    The other element missing is the synergistic effect of combinations of irritants.
    I believe that WaterZone Committees cannot be ignorant of all this information and may be trying to reduce the impact of dairy intensification by slow introduction of controls but are not going to go public because the public outcry would overwhelm them.They are nearly all in some way job dependant on farming and irrigation.
    Also the real cost of cleaning up this massive environmental and health damage will be immense.
    Better to avoid stirring the mud!
    Please help allert the public media to be brave enough to go really public before more 23year olds are robbed of their future.

  2. Francis

    I am a step-parent to a young man with Crohn’s disease so I applaud your efforts to find a cause. I would like to suggest a couple of additional angles I feel worthy of study.
    1) When you watch episode 9 of GMO’s Revealed you will see Dr Zach Bush explain how the herbicide glyphosate (brand name Roundup) loosens the tight junctions between the cells in the gut and causes leaky gut (starting at about 2:05 in the video). This herbicide is used extensively with GMO corn and soybeans and is the most used herbicide worldwide.
    I don’t know how things are in New Zealand but in the US vaccine use has increased dramatically starting in the late 1990’s. Although the manufacturers of vaccines try to hide it, some of these have been linked to gut conditions and autism. This link was first proposed by Andy Wakefield and the industry made a huge attempt to discredit him. The other factor with vaccines is all the added toxic ingredients (go to and search vaccine excipients for a complete list). These are known vaccine ingredients that are injected into the body in a way that bypasses it normal protections. Vaccines also may contain ingredients that we don’t even know to test for such as the SV40 virus that contaminated some of the polio vaccine. I feel that the vaccines were the cause of my stepson’s Crohn’s and later his Guillione Barre’ syndrome (GBS). GBS is even listed as a side effect of flu vaccine.
    Keep in mind that many reputable scientists and physicians feel that the 2 factors listed above work together in creating a number of different conditions depending on the genetic predisposition of the individual.
    I wish you the best of luck in your search for the root causes for Crohn’s. I also hope you take a moment to look at the possible contributions of these two other factors in Crohn’s disease. Again, best of luck in your search.

  3. raro

    I think there’s a typo in this para: surely it’s not scientists who are the missing link? “Dr Richard Gearry, a Gastroenterologist, professor of medicine at the University of Otago and also author of the original 2004 Canterbury study believes scientists “may be the missing link between whatever is going on in our environment and our risk of getting these diseases.”

  4. Kimberley

    18 years ago, Professor Tom Borody from Sydney told me exactly the same information as what is in this article. I had severe Crohns diseases and nothing was helping. Tom started me on Anti MAP therapy – a mixture of 3 antibiotics, and I was on them for 9 years. Only a short time after I started the treatment my symptoms rapidly improved and I now lead a completely normal life, Crohns free and medication free. I was even lucky enough to have 2 children, something I was told I would never be able to have. RedHill Pharmasuitical company in Israel is in its 3 stage of clinical trial for this medication ( in a combined capsule rather than 3 Antibiotics) – hopefully it will approved by the FDA very soon and it will be available to all.
    I grew up in Mid Canterbury right on the river next to a beef feed lot, and down the river from many dairy farms. I know that’s how I got the infection. This needs to stop.

  5. Peter Archer

    I wish I had known this a long time ago. I suspect that this bacteria is implicated in not only Crohns disease, but in other similar conditions, like leaky guy syndrome, and I am wondering if quite a lot of people are infected but never realise it?


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