Cuddling cows may combat asthma
Children growing up in contact with farm animals in rural areas are
more likely to be protected against allergic asthma than their city cousins.
Research around the world has suggested exposure to animals may play a
key role in protecting children against atopic, or allergic, asthma, which
accounts for about half of New Zealand asthma sufferers. Dr Jeroen Douwes,
from the Centre for Public Health Research, is leading a research project
to uncover whether the same can be said for New Zealand children and what
might be behind the findings.
“It appears that there is something in the lifestyles of farming
families that is protecting them from getting allergic asthma. This is
something positive for the rural community. If we can identify what factors
are creating the protective effect then hopefully we will be able to develop
tools that can help protect others.
“If there is an association between life on a farm and low levels
of allergic asthma in New Zealand then we can compare the results with
the European work. We might then be able to exclude a number of possible
causes that are different from Europe and identify what it is that might
help prevent allergic asthma.”
Surveys have been sent to 3000 randomly selected dairying, sheep and beef
and cropping farming families throughout New Zealand, asking questions
about their lifestyles, farm practices and health history. Surveys have
also been sent to a control group of 1000 families with low exposure to
farming. Unfortunately, to date the response has been less than anticipated
and Dr Douwes now has a team ringing the recipients to complete the surveys
over the phone. He says he realises farmers are often busy and finding
time to fill in a survey may not be of highest priority, but he stresses
that what they might uncover in the research could be extremely beneficial
to asthma sufferers.
He says research in other countries suggests that children raised on livestock
farms are more likely to be protected from allergic asthma than those
from cropping farms. It also appears there is a protective effect on adults,
although to date this has not been studied extensively. Growing up in
a rural area alone is not enough. To benefit from the protective effect
children must come into contact with livestock.
Dr Douwes says the protective effect appears to come from an immune-like
response to micro-organisms, and particularly to bacterial endotoxins.
He says there is also a hypothesis that drinking unpasturised milk and
being exposed to lactobacilli changes the gut flora, again leading to
a higher level of protection against allergic diseases. He says reduced
exposure to these and other micro-organisms may explain the increasing
prevalence of allergic asthma in western countries.
“In farming homes, where the family is in contact with livestock,
bacterial endotoxin levels are significantly higher than in non-farming
homes. In a healthy person exposure to endotoxins may induce non-allergic
symptoms but protect against allergic symptoms. The challenge is to find
a balance between the two.”
Dr Douwes says phase two of the project is to take skin prick tests from
600 families to assess their allergic immune responses. They will also
gather dust from the families’ homes, which will be analysed for
endotoxin levels, and assess a connection between the two.