[ASC-media] Media release: alien plants get up your nose

JCA Media jcamedia at starclass.com.au
Sun May 1 10:39:22 EST 2005

CRC for Australian Weed Management  Media Release 05/18

May 1, 2005



Millions are suffering in a rising national epidemic of allergies and asthma caused by the spread of alien plants in the Australian environment.

"There's no doubt at all, invasive plants are a massive national health problem - but not one that is widely recognised by either the public or the healthcare community," says Dr Rachel McFadyen, CEO of the Cooperative Research Centre for Australian Weed Management on World Asthma Day on May 2.

"They make life miserable for millions of people. And the worst plants actually make you allergic to a whole lot of things you weren't allergic to before."

Dr McFadyen said that when the drugs being taken for allergies and asthma, the doctor visits, hospitalisations, lost productivity and time off work are all accounted for, the total cost could exceed a billion dollars per year. The drugs alone have been estimated to be worth $300m annually. 

The good news, says Dr McFadyen, is that it is possible to control some of the worst offending plants quite cheaply - compared with solving other major health problems - using biological control.

Besides allergies and asthma, alien plants also bring with them other health concerns - deadly fruits and seeds, skin irritants, thorns, spines and stings and livestock poisons.

"Despite some successes, the continued spread of certain invasive plants is increasing the health impact on the nation," Dr McFadyen says. "It is our goal, by 2020, to stop the introduction of any more dangerous plants - and to cut back the extent of existing ones."

The worst offenders include plants like parthenium weed and annual ragweed, which over-stimulate the individual's immune system, giving them new allergies to other plants.  In susceptible individuals both can cause gross facial swelling, allergic eczema and infected sinuses. They have even driven some people from their homes and jobs. Others include privet and annual ryegrass - which is developing resistance to herbicides.

"Fortunately, through biological control, the abundance of these first two nasty introduced plants is in decline - and is a good example of how controlling a weed can achieve a useful healthcare outcome," Dr McFadyen says.

Unfortunately, she adds, many of the worst health offenders have escaped from people's gardens - and it is up to home owners and other land owners to play their part in combating a national health problem.

The NSW Asthma Foundation advises gardeners to avoid plants with wind-borne pollen, and choose native grasses in preference to imported lawns. "We must also all be aware of the risk we pose to community health when we let plants escape from our gardens and establish in the wild," says Dr McFadyen.

Of the 25 major seasonal allergens in Australia around 20 of them are introduced species, says Dr Tim O'Meara of the Woolcock Research Institute at Sydney University

"Native species may also be very important, but they are less well characterized as allergen sources. The introduced species that are know to drive allergies include pasture grasses such as ryegrass and paspalum, trees such as birch and olive and weeds such as ragweed, plantain and parietaria. 

"In Australia, pollens are generally associated with hay fever, known as allergic rhinitis, which affects 20-40% of adults. We do not see a clear association with asthma, except in the case of thunderstorm asthma when pollen grains rupture to a size that readily penetrates deeper into the airways and causes airway narrowing, even in people with no previous history of asthma."

In the US and Europe the pollens from a number of plants introduced into Australia are also found to be associated with asthma, Dr O'Meara says. This may be a result of the stronger seasonality of the pollens in US and Europe. In Australia the pollen seasons all tend to blend together, so it is hard to tease out an effect on asthma - which is a chronic disease - due to a single species. Some of the plants associated with both rhinitis and asthma in the Northern hemisphere are ragweed, parietaria, olive and birch.

"An example of the impact of introduced species on allergies is the association between ragweed and autumn hay fever. In the Northern Rivers area of NSW, an area known to have a ragweed problem, 35 per cent of people are allergic to ragweed. Many suffer hay fever in the months of March-April when ragweed releases its pollen into the air."

One plant which is a growing problem both as an environmental weed and as cause of allergies is the olive tree, which is spreading in the wild in SA. Near infested areas it can account for up to 40 per cent of the airborne pollen on some days, says Flinders University researcher Dr David Bass

"Pollen from olive trees can exacerbate asthma and a range of other allergic conditions. In the Mediterranean area and in California, olives are widely distributed and its pollen is one of the most important causes of respiratory allergy," he says.

"Olive pollen is also cross-reactive. If someone is exposed and sensitized to olive pollen they may react to other allergens such as ryegrass."

Toxic plants which pose a risk to children and pets include thornapple and castor oil seeds, arum lily and blackberry nightshade.

"Although we spend a lot of money controlling weeds in Australia each year, very little is actually targetted at those plants which represent major health problems," Dr McFadyen says.

"At present only one out of 23 problem plants posing a significant respiratory or toxic threat has received federal funding for control. We know that if we cut back the abundance of a plant which causes health problems, the health problems decline and so does the dependence on drugs and healthcare.

"This is a clear case when a modest investment in controlling invasive plants can reap major national health benefits, make life better for millions of people and help reduce the swelling cost of healthcare."

More information:
Dr Rachel McFadyen, Weeds CRC, 0409 263 817 (Sunday 1 May), 07 3362 9388 (wk)
Peter Martin, Weeds CRC, 0429 830 366 (Sunday 1 May), or 08 8303 6693 (wk) 

Some facts on weeds:

*	28 000 plant species have been introduced to Australia since European settlement (this is more than the total number of native plant species - 20 000)

*	over 2500 of these introductions are now established in the wild, and this is increasing at 10% per year

*	65% of these established invasive plants have escaped from parks and gardens, and many are still being traded.

*	Foreign invasive plants that cause allergies in Australia through airborne substances include:

Annual ryegrass (Lolium rigidum)
Ragweed (Ambrosia spp.)
Yorkshire fog (Holcus lanatus)
Capeweed (Arctotheca calendula)
Plantains (Plantago spp.)
Asthma weed (Parietaria judaica) 
Privet (Ligustrum spp.)
       Olive (Olea europaea)

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