6 December 2024

Gardening this spring? Beware of legionnaires’ disease lurking in compost

With spring here and summer time approaching, it’s a popular time for Kiwis to get into the garden to plant veggies and maintain flower beds. 

While working in the garden, at times you tend to forget to keep safe from a potentially serious bacteria lurking in compost, potting mix, mulch, etc. This bacteria can cause legionellosis, commonly known as Legionnaires’ disease.

You can catch the disease by inhaling the dust from compost, potting mix or organic soil containing the bacteria.

Legionnaires’ disease
Handle compost, soil material with care

Legionnaires’ disease affects the lungs, causing flu-like illness. The illness may be mild or severe like pneumonia but can be fatal, if not treated timely.

Many may not be aware, but New Zealand has the highest reported incidence of this Legionnaires’ disease globally.

This was revealed in the first nationwide surveillance study of Legionnaires’ disease in 2019 by Prof David Murdoch, the then Dean of the University of Otago (now Vice-Chancellor) who collaborated with 20 hospitals around the country.

Researchers noted 15 patients had died within 90 days of diagnosis and 38 required admittance into the hospital’s intensive care unit.

Common early symptoms include malaise (feeling generally unwell), fever, loss of appetite, headache, muscle aches, abdominal pains, shortness of breath and dry cough.  By the second or third day, symptoms may also include nausea, vomiting, diarrhoea and confusion.

“Legionnaires’ disease needs to be taken seriously,” says Dr Partho Rao, a GP and an urgent health care physician in Hamilton.

“As a GP, my advice is anyone who develops such symptoms within 2-10 days after handling soil, compost or potting mix, should see their doctor immediately.”

The incubation period for the development of pneumonia is from two to ten days.

Seriousness of this disease can be gauged from a case in December 2020, when a Palmerston North woman inhaled the bacteria when she opened a bag of potting mix when planting vegetables.

She failed to take the basic precaution of wearing a mask while handling potting mix. She was in coma for 10 days, initially paralysed and put on dialysis for kidney failure.

Fortunately, she survived and lived to recite her ordeal. For several others this disease proves fatal.

Take these simple precautions (Image courtesy: SouthernHealth)

When asked if this disease can be treated, Dr Roy says, “Usually antibiotics are effective against legionellosis if given early. But it is important for the illness to be diagnosed and treated promptly to avoid development of complications that could lead to hospitalisation.”

According to Dr Roy, Legionnaires’ disease is more likely to affect older people, or those with underlying lung disease and other long-term conditions, such as diabetes. 

This is affirmed by Prof Murdoch’s research as 60 per cent of the patients found to have the disease, were over the age of 65. 

Legionnaires rarely affect young and healthy people, and is not contagious.

Keeping yourself safe from getting Legionnaires’ disease is not difficult. Those who work with compost and potting mix – whether at home or in their profession, can easily protect themselves from the risk.

The standard advice by the Ministry of Health when working in the garden and handling soils, compost, mulch, or potting mix includes:

  • wear a tight-fitting dust mask and gloves
  • avoid inhaling dust
  • open bags of soil products or composted potting mixes slowly by cutting, rather than ripping
  • ensure your area of work is well ventilated
  • when potting plants, dampen the soil or compost first to reduce dust
  • water your garden using a low pressure spray
  • avoid touching your face
  • wash your hands after finishing even if gloves have been worn, and
  • read and follow the warning label on bagged garden products.

As always, follow the adage ’prevention is better than cure’. Enjoy working in the garden, but remember to take these basic precautions as these could be a life-saver for you.


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