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.

Canterburywater

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.

..

If you would like to see more investigative journalism in New Zealand on pressing issues like this, please consider supporting Wake Up NZ on Patreon. Patreon is a crowd funding platform for on-going projects, and your support means we can provide media content on a more regular basis in a country seriously lacking in investigative journalism.

About The Author

Kyle is a Christchurch based freelance writer with a passion for investigative journalism and thirst for the truth. He's also an avid environmentalist and tiny house dweller.

One Response

  1. 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?

    Reply

Leave a Reply

Your email address will not be published.