Legionnaires' disease

Apart from the global economic chaos, Ontario also seems to have been affected by a series of nasty bugs. First, it was the Listeriosis outbreak in Toronto and GTA last month. Then, the E.coli outbreak in North Bay and now it is Legionella. An update released by the Peel Public Health in September says that there has been an increase in legionellosis cases noted in Peel and other jurisdictions around the Golden Horseshoe. Hamilton Public Health also confirms seven cases of legionellosis since August 2008.

So, what is Legionella?
Legionella bacteria (gram negative, poorly staining rods) are naturally found in the environment, usually in water. They may be found in water distribution systems of hospitals, hotels, ships, public buildings, homes and commercial facilities. They can survive for several months in a wet environment and multiply in the presence of algae, protozoa and organic matter.  Legionella acquired its name after a July, 1976 outbreak among people attending a convention of the American Legion in Philadelphia. The mystery disease sickened 221 persons, causing 34 deaths. The causative agent was identified by scientists at the Centres for Disease Control and Prevention (CDC) and subsequently named Legionella.

Symptoms
Legionella pneumophila is the causative agent of the legionellosis disease which presents itself in two forms:

• Legionnaires’ disease – the more severe pneumonic form
• Pontiac fever – the milder non-pneumonic illness

Legionnaires’ disease is a type of pneumonia that may be mild to fatal. Symptoms include high fevers, chills, nausea, cough and headache. There may be memory loss or a change in mental status. Pontiac fever is not associated with pneumonia and is milder. Symptoms include fever and headache.

Transmission
Legionella infections are acquired exclusively from environmental sources – through inhalation of contaminated aerosols – mist droplets containing the bacteria. These aerosols are formed from cooling towers, large central air conditioning systems, domestic hot-water systems, showers and faucets, fountains and similar water environments. Natural sources of Legionella include freshwater ponds and creeks. Legionella can travel at far as 6 km from its source by airborne spread. It is not spread from person to person. Older people (65 years or more) or immunocompromised patients are more susceptible to the infection.

Control
Legionella infection can be best reduced by good engineering practices in the operation and maintenance of air and water handling systems as emphasized by ASHRAE – American Society of Heating, Refrigerating and Air Conditioning Engineers. Common measures taken are cooling tower maintenance, increased heat shock treatments and use of biocides. Water treatment, prevention of scaling and algal build-up, periodic cleaning and maintenance of equipment are highly recommended.

Monitoring and Sampling
Air, water, sludge and sediments can be sampled for detection of Legionella. For sampling Legionella in water systems, several locations are recommended.  Water at bottom drain and outlet pipes, water from hot and cold faucets, tanks, humidifiers, spas and fountains can be sampled in sterile containers and sent to the lab for analysis at the earliest. Swabs are recommended for surfaces like inside of faucets and shower heads or any surface showing biofilm formation. Culturable air sampling is done by using air sampling pumps that draw air directly onto culture media which can be further analysed for the presence of Legionella after incubation and other tests.

For further information and a detailed protocol on Legionella sampling, call us at 905-290-9101 or e-mail us at info@moldbacteria.com.

Edited By: Dr. Jackson Kung’u, PhD.