LCCS Industrial Microbiology

	Lewis Conquer Consultancy Services


	Legionnaires' Disease *Lewis Conquer Consultancy Services are no longer involved in Plant Hygiene Surveys for Legionella.* This page has been maintained in order to provide bckgrond information. Legionnaires disease- causes and epidemiology Legal requirements in the UK for controlling Legionnaires' disease Health Effects The term "Legionnaires' disease"** was coined in 1976 after a dramatic outbreak of serious respiratory disease at a convention of the American Legion led to the discovery of a new disease entity and, eventually, to the identification of the responsible bacteria, Legionella pneumophila. L. pneumophila, one of more than twenty currently recognised species of the genus Legionella, is the species most commonly implicated in cases reported both in Australia and overseas. Illnesses caused by any species of Legionella are called Legionellosis. "Legionnaires' disease" is the term used for the disease caused by L. pneumophila. However, "Legionnaires' disease" has become the familiar term used to refer to any severe form of pneumonia which is caused by a species of Legionella. This form of pneumonia may be accompanied by involvement of other organs such as the brain, causing confusion; the bowel, causing diarrhoea; and the kidneys, causing kidney failure. Symptoms include rapid onset of high fever, non-productive cough, chills, headache and general 'aches and pains'. Positive identification can be achieved by isolating and identifying the L. pneumophila from the patient's respiratory secretions or blood. The incubation period, that is the time between infection and signs and symptoms appearing, is usually 2-10 days. Less than 5 per cent of the exposed persons are likely to become ill, but up to 30 per cent of these may die. Pontiac fever, also caused by a species of Legionella, is an influenza-like illness with symptoms including fever, chills and headache. The incubation period ranges from 4 hours to 3 days. Up to 95 per cent of the exposed persons become ill. Pneumonia does not occur and full recovery can be expected. Many infections by L. pneumophila do not result in recognisable signs and symptoms. Antibodies have been found in up to 25% of adults tested. This suggests that up to I in 4 adults have been infected at some time in their life but have not necessarily developed any symptoms. Humidifier fever is not caused by Legionella, yet it is often considered, incorrectly, as a form of Legionnaires' disease. This influenza-like fever may result from the inhalation of micro-organisms that cause allergic reactions. The potential source is often the humidifier of an air conditioning system. Humidifier fever belongs to a group of illnesses known collectively as hypersensitivity pneumonitis. Sensitisation to these microbial contaminants occurs after a period of repeated daily exposures and the period may vary from 1 month to a year or more. It should be noted that the presence of fungi, algae, protozoa and other bacteria in air-handling and water systems may contribute to the: multiplication of the Legionella bacteria; emergence of diseases in addition to those associated with the Legionella bacteria. Sources of Infection Legionella bacteria are widely distributed natural inhabitants of waters. They have been found in lakes, rivers, creeks and other bodies of water ranging in temperature up to 60 degrees C. However, significant multiplication of these bacteria is generally restricted to temperatures of 20 degrees C to 45 degrees C and particularly to the range 35 degrees C to 43 degrees C. Systems with waters of this temperature range facilitate proliferation. The growth of L. pneumophila is promoted by the presence of other micro organisms. Certain single-cell organisms are able to amplify these bacteria in cooling towers as well as to protect them from adverse conditions, including the biocidal action of water treatment chemicals. Other bacteria and algae can provide nutrients for L. pneumophila. Sediments can stimulate the growth of the environmental micro flora which, in turn, stimulate the growth of L. pneumophila. Investigations of the relationship between the chemical environment in plumbing systems and growth of L. pneumophila. has shown that low concentrations of certain metals such as iron, zinc and potassium enhance proliferation of the species. Hence, the metal components and corrosion products of plumbing systems (e.g. galvanised iron) may play a role in promoting growth of these bacteria. The constituents of certain types of rubbers used in rubber fittings in the system can also support the multiplication of L. pneumophila. The proliferation of L. pneumophila. occurs mainly in water systems as a result of the inter-relationships between temperature, environmental micro flora and sediments and the chemical composition of waters in man-made systems. In general, the sources of Legionella implicated in outbreaks of Legionnaires' disease have been traced to large air conditioning plants or to hot water distribution systems which have been incorrectly commissioned or have been poorly maintained. The release of aerosols from water distribution systems may occur from shower heads or from water splashing in hand basins or baths. Standby installations would also be sources of infection if they are used infrequently and not included in the general maintenance routine. Other less common sources of infection that have been recorded include spa pools, the coolant in industrial milling machines, high pressure cooling and cleansing processes and humidification devices. Potential sources of infection could include domestic air conditioners, artesian bores, decorative fountains, fixed garden sprinklers, car washes, and above ground storage tanks, which feed aerosol generating equipment, although there have been no recorded cases from these sources. Outbreaks of Legionnaires' disease are sporadic and the source of the organisms is often very difficult to determine. Mode of Transmission The means by which these Legionella bacteria can infect humans involves the formation of aerosol, the air transport of the aerosol into the breathing zone of persons and the deposition of the aerosol in the lung. Controlling the build up of Legionella spp. In the UK owners or occupiers of sites using equipment that falls within the scope of the Notification of Cooling Towers and Evaporative Condensers Regulations 1992 must inform the local authority about the use of the plant. Guidance and advice can be found in two HSE documents: HS(G) 70 The control of Legionellosis including Legionnaires' Disease Approved code of Practice L8 The prevention or control of Legionellosis (Including Legionnaires' Disease) The second publication places responsibility on employers to ensure the following: identify and assess the sources of risk prepare a scheme to prevent or control the risk implement and manage precautions keep records of the precautions implemented Assessments should be reviewed if there is reason to suspect that the original findings may no longer be valid e.g.: if there is a change to plant or water systems, or to their use there are changes to the use of buildings in which equipment is housed where new information concerning the risks or control measures becomes available where the results of checks or tests show that control measures are not effective Exposure to harmful organisms, including Legionella, is covered in the UK by the Control of Substances Hazardous to Health 1994 (COSHH), in the same way as these regulations cover the exposure to chemicals, COSHH imposes the duty on an employer to ensure that employees are not exposed to harmful substances, or where this is not practicable the exposure is adequately controlled. . .. .