LEGIONELLA AWARENESS SEMINAR for the NORTH WEST WALES HEALTH AND SAFETY GROUP by Ken Ashley formerly HM Specialist Inspector HSE Dangerous Pathogens Section.

LEGIONELLA AWARENESS SEMINAR

for the NORTH WEST WALES HEALTH

AND SAFETY GROUP by

Ken Ashley formerly

HM Specialist Inspector HSE Dangerous Pathogens Section

now Independent Consultant

SESSION ONE

LEGIONNAIRES’ DISEASE AND

LEGIONELLA BACTERIA

Legionnaires’ diseaseLegionnaires’ disease

• First recognised July 1976 Philadelphia

• American Legionnaires’ convention

• 182 cases of pneumonia

• 29 died

Legionella : Hazard or risk?

• The hazard : is

• the presence of Legionella bacteria in your water system.

• The risk: is:

• Legionella bacteria growing to a sufficient level to cause Legionnaires’ disease in the population exposed

Legionnaires' disease in Residents of England & Wales by Category of

Exposure 1980 to 2004

What is the real number of cases? Under-reporting

• Estimate 1. –Countries with best surveillance report 20 cases / 106 p.a. –This suggests in England & Wales a total of 52 x 20 = 1040 cases

p.a.– Estimate 2

–2000/2001 - 192,565 cases of pneumonia in England in 1 year–Agent identified in <5% –Estimates of true incidence of LD based on intensive studies of

patients in hospital with pneumonia caught in the community suggest 2% – 3% of all community acquired pneumonias are legionnaires’ disease –This suggests in England & Wales there are about 5500 cases

p.a.

Legionellosis - an infection caused by Legionella

• Severest - legionnaires’ disease – Low attack rate – infects less than 5% of those exposed– atypical pneumonia:

– symptoms: cough - usually dry, 75%; fevers 70%; confusion, 45%; new sputum, 45%; bad headache, 32%; diarrhoea & vomiting ~30%

– up to 40% die (European average 13%)– Incubation (time from exposure to first symptoms) : 2 – 10 days– but sometimes 16 or even up to 21 days (may be longer in the

immunocompromised)• Mild - Pontiac / Lochgoilhead fever

– high attack rate: affects over 95% of exposed– influenza like illness: no deaths – incubation: 12 – 48 hours

• Asymptomatic (healthy without symptoms)– – (serological evidence) of exposure to infection

•

Mode of infection

• Inhalation of organisms suspended in air • (aerosol - not a spray)• Rarely by aspiration, maybe significant for

patients in the dental chair? • No evidence of person to person

– Factors NB for infection include:

» Bacterial burden (infectious dose unknown)

» Effectiveness of dissemination

» Virulence of organism

» Patient susceptibility

Growth requirements of legionella bacteria

• Grows well between 29oC- 40oC with an optimum of 35oC

• Will grow between 20°C and 45°C• Below 20°C legionella survives but does not

grow • Above 50°C legionella is killed • Food e g sludge in a calorifier• Presence of cysteine(an amino acid) and iron• Iron increase growth 10,000 to 100,000 fold

Susceptibility to physical and chemical agents

• Heat eg hot water above 50°C and particularly above 60°C as used in hot water storage

• Biocides used in hot and cold water services where temperatures cannot be achieved such as chlorine dioxide or silver ions

Cultural characteristics

• Do not grow on ordinary nutrient media

• Up to 14 days to grow legionella

• Reminder-monitoring is a snapshot

• Reminder-monitoring is not control

• Most clinically important bacteria grow within 18 to 24 hours

• Reminder-dip slides do not detect legionella bacteria

Identification

• Culture-for both patients and plant

• Urine antigen(patients)

• Antibody(patients)

• Gene probe(both but will detect dead organisms in plant as well as live)

Habitat

• Wide-spread in natural water sources– Rivers and lakes - therefore in the water

supply– Mud and soil– Then will enter into many man made

systems eg hot and cold water systems, cooling towers etc as less sensitve to chlorine than most waterborne bacteria.

– Therefore you cannot avoid it entering your practice

Habitat

• Biofilm• Other organisms are needed, particularly

ameobae in a water system that ‘graze’ on the water/suface interface eg the inner surface of a pipe

• When legionella bacteria burst from an amoeba there are about 10,000 released into the water

Pathogenicity

• Mainly, L. pneumophila serogroup 1 and 6

• L. micdadei, L. dumoffi

• You need to know the name of the organism in bullet point one as this is the one that causes 90% of cases/outbreaks

Statistics summary

• 600 or so cases per year(much higher in 2002 because of Barrow)

• MOST cases are caused by H&CW • 50% possibly travel associated if you

include returning to an infected water system at home

• Usually 10-12% mortality(in hospitals up to 40%)

• Males more likely to be affected (3:1)

Conditions required for proliferation

• Water containing legionella (inevitable) • Temperature between 20°C and 45°C, noting

that the maximum growth is between 30°C and 40°C

• Food source eg organic debris such as leaves or animal access to cold water tanks

• Stagnation eg blind ends or surfaces beneath scale and rust as often found in old domestic (some of your practices) hot and cold water systems

Factors promoting infection

• Presence of airborne droplets containing viable legionella

• Chain of events– Presence of legionella– Conditions suitable for

multiplication/proliferation to high numbers – Means of creating breathable droplets – Exposure of susceptible person

Who is most susceptible?

•Men more than women ( ≈ 3 : 1)•Aged > 50 years•Smokers•Heavy drinkers•Diabetics•Chronically ill•Immuno-suppressed

–transplant patients–Steroid treatment

0

100

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300

400

500

600

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900

1000

0-9 10-19 20-29 30-39 40-49 50-59 60-69 70+ NS

Age Range

Nu

mb

er o

f C

ases

Males Females

BARROW IN FURNESS

• July/August 2002• Approximately 175 infected and 7 deaths• Stafford in 1985 was 100+ cases and 28

deaths• Associated with a cooling tower used to

reject heat from an air conditioning system

Summary

• Moisture/water needed• Temperature between 20oC and 450C • Nutrients from sediment, sludge, scale,

compatible organisms and materials used in construction

• Presence of biofilm, stagnation and conditions to promote proliferation

• Breathable droplets