June 14, 2008

Be Careful Around Compost: Death in UK Linked to Decay-Loving Fungus

I want to preface this with a disclaimer. What follows may be a bit scary for people who compost as part of their gardening, but it's nothing to get panicked about. It's a call for a bit of caution regarding something about which people may not know.

The death of a gardener in the UK was caused by inhalation of spores from the fungus Aspergillus fumigatus, an ascomycete mold that is commonly found in small quantities in compost. Readers may have heard about other members of the genus Aspergillus in recent memory; this is the same group of molds that contains species which produce aflatoxin and have been found on grain products in the past.

In this case, however, the gardener who died was not killed by aflatoxin but by infection with the mold itself. This happened because he inhaled an unusually large quantity of spores while working with compost. The spores germinated in his lungs and caused an infection capable of killing an otherwise healthy (but see below) 47-year old man.

Fungal exposure and gardening
National Health Service, UK

...a case of a 47-year-old man who "went to hospital with chest pains just a day after opening a bag of rotting leaves". The man died three days later from aspergillosis, which he contracted after inhaling spores from a fungus that grows on dead leaves (Aspergillus fumigatus)...

A 47-year-old man – a welder by trade – was admitted with a history of cough, pleuritic chest pain (a sharp pain worsened by breathing, coughing and movement), increasing shortness of breath, fever and myalgia (muscle aches). He had previously been in good health, although he was a smoker. Other features at presentation included high fever, high breathing rate, irregular chest X-rays, high white blood cell count and crackling sounds in the lung while breathing. The initial assumption was that he had pneumonia, so he was put on antibiotics while further investigations took place.

After 24 hours, the patient was transferred to intensive care because of extreme shortness of breath. His condition worsened, and he showed signs of kidney distress and sepsis (high heart rate, low blood pressure and fever in response to infection throughout the body). The clinicians found that a fungus called Aspergillus fumigatus grew from the man's saliva samples...

Clinicians established from his partner that the symptoms started less than 24 hours after he spread rotting tree and plant mulch from a sack around the garden. Clouds of dust had "engulfed him"...

The clinicians conclude that the patient experienced an acute invasive pulmonary aspergillosis infection. Although this infection would normally be seen only in immunocompromised patients, they say that "smoking and welding could have damaged his lungs and increased his susceptibility to infection". The clinicians also say that "because he died so quickly", they cannot rule out an undiagnosed immunodeficiency.

The clinicians add that although acute aspergillosis following contact with decayed plant matter is rare, it "may be considered an occupational hazard for gardeners". They recommend that quick and appropriate treatment for the fungal infection is essential...
This unfortunate individual seems to have created the circumstances that led to his demise. Such a situation is easily avoidable, though.

First, Aspergillus species mainly flourish where temperature and moisture are high. In the case of this gardener, it's worth noting that he was storing his compost in a plastic bag. That allows for the build-up of lots of moisture while trapping the heat naturally generated by decay and so is almost certain to foster the growth of numerous Aspergillus species, the spores from which are ubiquitous in the air and soil. The remedy is to keep temperature and moisture levels low by allowing heat and water to escape. Compost should never be stored in fully-closed containers and should be turned over frequently to allow for cooling and evaporation. Most species won't grow at all when moisture content is lower than 7%. The particular species in this case, A. fumigatus, also prefers temperatures close to that of the human body.

Second, it would be a very good idea to wear a pollen mask when coming into contact with compost. Aspergillus spores can't hurt you if you don't inhale them in the first place and a mask is an effective and relatively cheap way of preventing this. Compost is by its very nature a breeding ground for fungi and bacteria and inhaling compost dust can lead to infections other than aspergillosis, so don't do it.

Again, there's nothing here to be overly concerned about. As the British NHS states at the end of the article linked above:
Gardeners should not be overly worried that their occupation or hobby has suddenly become a dangerous one. Gardeners are likely to be exposed to a variety of bacteria and mould, which are present in the soil and the compost that they use. In healthy individuals, these do not usually cause serious infections...
A modicum of caution goes a long way.

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