Research has revealed children under 10 are most likely to contract campylobacter disease by drinking raw milk and account for 29% of the raw milk-related cases notified in the MidCentral Health district from 2012 to 2017.
The study collected data on all cases of campylobacter notified in that period. It then dug deeper into raw milk campylobacteriosis cases, comparing the demographics of them to other campylobacter cases where raw milk was not drunk.
Raw milk was linked to almost 8% of the notified cases.
There was a peak in cases among children from both rural and urban homes.
Among the raw milk cases, 17% were rural children and 8% were urban children. Two-thirds of all raw milk cases were urban, the rest rural.
Campylobacter is far from the worst bacteria that can be contracted from raw milk. However, it is the most common, typically resulting in stomach cramps, diarrhoea and vomiting.
Once diagnosed it must be notified to the health authority for further investigation.
Raw milk is more likely than other foods to cause campylobacter.
Raw milk provides an ideal culture for the likes of campylobacter bacteria because it is a good food source, in an environment naturally close to the livestock source.
Previous Ministry for Primary Industries studies have found almost two-thirds of dairy farmers drink raw milk but there are associated factors that can influence the rate of disease in rural children.
“There has not been a lot of work done but it appears milk consumption may decline with age so children might be drinking more. Children may also be more susceptible to raw milk associated disease organisms in general.”
The seasonal potential for cows to shed campylobacter bacteria cells in greater numbers at certain times can also come into play.
“It could be they are shedding more bacteria at a time when milk production is starting to increase after calving, often when contact with cattle is starting to increase on a daily basis.”
Adding to the multiple factors is some evidence exposure to campylobacter can deliver a level of resistance that fades after weeks or months.
For rural families who consume milk from the farm dairy during the year then switch to pasteurised purchased milk over the dry period of lactation that resistance may fade, leaving them more at risk at a higher risk period of the year when they start using farm-sourced milk again.
“So you have a bit of a double header there with increased bacteria shedding and a lift in consumption of the farm-sourced milk.”
The survey held some surprises about why people do or don’t choose to drink raw milk.
Overseas work has indicated consumer choices are based on a desire to support local farmers, a belief in better animal welfare and for perceived health reasons.
However, there is no strong consensus among raw milk cases about their motivation for choosing the product. The most common motivation reported was health reasons but that was for only about a third of the cases. Other popular reasons were taste and convenience.
She said it would have been interesting to also better understand what the behaviour change was, if any, in people who drank raw milk and became sick.
While not intending to take the work any further herself Davys said there are some interesting areas researchers might want to examine.
They include a better understanding of the spatial link between raw milk supply points and disease outbreaks. Further exploration of data from the sequence typing of the campylobacter organisms could determine if there is a statistical difference between the types seen in raw milk cases and general campylobacteriosis cases.
Davys said she won’t drink raw milk knowing the infections that can come from it, of which campylobacter is only one.
“So you need to be aware if you do choose it there is a higher risk of becoming sick and children are most at risk.”
