Legionnaires’ Disease and Cooling Towers ©

Legionnaire’s Disease:

Symptoms include fever, chills, muscle aches, and a initially nonproductive cough. Diagnosis is by an antigens-antibodies test. Legionnaires’ disease poses the greatest threat to people who are elderly, ill, or with a compromised immune system.

Legionella pneumophila. bacteria were identified as the cause of a pneumonia outbreak at an American Legion convention in Philadelphia, Pennsylvania. in July 1976. Later Legionella investigation linked the bacteria to other unexplained pneumonia outbreaks in 1965; retained samples of the bacteria date from 1947.

Since the first reported outbreak of Legionnaires’ Disease there have been at least 11 epidemics of the disease resulting in 1,011 cases and 156 deaths. Legionnaires’ Disease bacillus, isolated by the center of disease control in Atlanta, was named appropriately Legionella pneumophila.

Legionella are Gram-negative, non-spore-forming, motile, aerobic bacilli. There are at least 40 types of Legionella bacteria, half of which are capable of producing disease in humans. A disease that arises from infection by Legionella bacteria is referred to as legionellosis. The L. pneumophila bacterium, the root cause of Legionnaires’ disease, causes 90% of legionellosis cases. The second most common cause of legionellosis is the L. micdadei bacterium, which produces sixty percent of infections with non-pneumophila species of Legionella. [1]

Amoebas colonized with Legionella can provide a concentrated source and therefore are more significant source of infection than the direct inhalation; L. pneumophila bacterium live inside Amoeba which are part of the slime layer film. Legionella spp. can cause two distinct syndromes — Legionnaires’ disease and Pontiac fever, collectively referred to as legionellosis [2] . Legionnaires’ disease is characterized as a form of pneumonia.

Although the attack rate is less than 1%, mortality among hospitalized cases can be as high as 15%. Pontiac fever is a non-pneumonic, non-infectious, non-fatal, influenza-like illness. The attack rate can be as high as 95% in the total exposed population. Patients with no underlying illness or condition recover in 2–5 days without treatment. Ninety per cent of cases of legionellosis are caused by L. pneumophila. Most of the fraction of legionellosis associated with recreational-water use appears to be associated with spas. [3] and [4] Outbreaks in swimming pools and ambient recreational waters have never been reported [5]. This is probably due to the lower temperatures. Legionella bacteria like the warmer temperatures of cooling towers and spas. which create an ideal habitat (warm, nutrient-containing and oxygen loaded water. Dose–response experiments using animals suggest that extremely high doses (~107) are required to initiate infection and disease. [6] Thus, clean equipment is a necessity. The amoebas colonized with Legionella is found in the slime layers that may be allowed to accumulate on the tower sump, pipes and slats are surface regions of much higher legionella doses than found free floating in the running water. Inspection of the surfaces is necessary to see if the system is fowled.

Symptoms:

Early symptoms are like the flu and include:

• Headache
• Fever
• Chills
• Muscle aches and pains
• A dry cough and shortness of breath

Other body symptoms that may occur are:

• Diarrhea
• Mental confusion
• Kidney failure

Catching the disease:

Sources may include water, HVAC equipment. Inhalation of contaminated aerosols appears to be the sole route of exposure. The use of hot water with production of aerosols allows Legionella, if present in the water, to get into the lungs. The symptoms of Legionnaires’ disease usually begin to appear within six days of being exposed to the bacteria.

Exposure to the Legionella bacteria doesn’t necessarily lead to infection. According to some studies, although an estimated 5-10% of the American population show serologic evidence of exposure, most do not develop symptoms.

Legionella bacteria account for 2-15% of all cases of pneumonia, Only a few people who come in contact with the bacteria become infected.

It is the high dose contact that maintenance workers should be concerned.

General risk factors for the illness are:

• Men over 50 years of age
• Smokers
• People with chronic illness
• People with medical conditions that impair their immune system
• chronic lung disease
• excess consumption of alcohol.

Specific risk factors:

• frequency of spa use and length of time spent in or around spas.
• working on, around, and inside cooling towers or contact with mist from windage with entrained water droplets (as opposed to water vapors)

Exposure is through the lungs by breathing fine droplets of water containing the bacteria. Legionella bacteria is wide spread in the environment; it is found in rivers, lakes, creeks, hot springs, spas, potting mix, and process water systems such as cooling, heating, industrial processes and cooling towers. Most cooling towers have mist, or water drift, that may be breathed into the lungs by those near these systems.

Preventing Legionnaires’ Disease

There is no vaccine to prevent the disease. However, the growth of the bacteria in spas and cooling towers can be controlled. You can also take care to avoid exposure to Legionella bacteria from other sources.

Treatment :

If you have flue like symptoms, it is important to tell the doctor that you work around cooling towers, and that Legionnaires’ Disease may be suspect.

Several drugs, such as penicillins and cephalosporins, are ineffective against the infection. Although they may be deadly to the bacteria in laboratory tests, their chemical structure prevents them from being absorbed into the areas of the lung where the bacteria are present. Thus, the disease may get much worse is not treated with the correct medication. Delay of the proper medication has happened when the improper antibiotic is administered.

The antibiotic of choice has been erythromycin, sometimes paired with a second antibiotic, rifampin [7]. Tetracycline, alone or with rifampin, is also used to treat Legionnaires’ disease, but has had

mixed success in comparison to erythromycin. Other antibiotics that have been used successfully to combat Legionella include doxycycline, clarithromycin, fluorinated quinolones, and trimethoprim/sulfamethoxazole. The type of antibiotic prescribed by the doctor depends on several factors including the severity of infection, potential allergies, and interaction with previously prescribed drugs. For example, erythromycin interacts with warfarin, a blood thinner. In severe cases with complications, antibiotic therapy may be joined by respiratory support. If renal failure occurs, dialysis is required until renal function is recovered.

Prognosis

Most cases of Legionella pneumonia show improvement within 12-48 hours of starting the appropriate antibiotic therapy. Erythromycin has been shown to have a major impact on recovery from Legionnaires’ disease. Recovery is also linked to the victim’s general health and absence of complications. If the patient survives the infection, recovery from Legionnaires’ disease is complete. Similar to other types of pneumonia, severe cases of Legionnaires’ disease may cause scarring in the lung tissue as a result of the infection. Renal failure, if it occurs, is reversible and renal function returns as the patient’s health improves. Occasionally, fatigue and weakness may linger for several months after the infection has been successfully treated.

Public Awareness

In November 1999, CNN & TIME, a TV news magazine, aired a segment on Legionnaires’ disease in hospitals. CNN reported that “every year thousands of patients contract [Legionnaires’] disease from contaminated hospital water systems.”

The show included an interview with Dr. Victor Yu, a Legionnaires’ expert from the VA Medical Center in Pittsburgh:

“These outbreaks–they’re actually occurring all through the country every week,” said Yu. “It’s an explosive problem to realize that people are dying, to realize that the means are there for preventing all this from happening, and that those means are not being exercised.”

Indeed, more people are learning that Legionnaires’ disease is widespread, and that preventive measures are not implemented in most buildings.

How are Legionella bacteria spread in indoor environments?

Cooling towers are part of large modern air-conditioning systems. They are used to cool water and dissipate unwanted heat to the atmosphere through water evaporation. Warm water flows into the top of the cooling tower through spray nozzles (as shown in the schematic Figure 1). While the water passes through the nozzles, tiny airborne droplets are formed, providing maximum contact between the water and the air moved through the tower by fans. To prevent droplets from fusing into larger ones, splash bars are placed below the nozzles.

While falling through the tower, some of the water evaporates. Because evaporation consumes heat, the remaining water is cooled. Air pushed through the tower by fans also cools the water. Some droplets, known as drift, are carried out of the tower by the air stream produced by the fans. This water loss is reduced by a drift eliminator positioned at the top of the tower. The cool water collects at the bottom of the tower and is pumped back for another cycle.

Evaporative condensers) are similar in their construction and operation to cooling towers. Cooling towers and evaporative condensers may contain Legionella and other microorganisms brought in by circulating air or water.

Legionella grows easily in the water, especially if algae and scale are present. Legionella can be dispersed with aerosolized drift or with the evaporate, but it may enter the air-conditioning system if there is a break between its ducts and those of the cooling tower or evaporative condenser.

Legionella has been found in hot water tanks, hot water propelled from shower heads, faucets and whirlpool spas. It is not known whether Legionella enters a building’s water from municipal feeder systems (but city water in showers have tested positive) or adjacent contaminated cooling towers.

How can we prevent Legionnaires’ disease?

Since the bacteria thrive in warm stagnant water, regularly disinfecting ductwork, pipes, and other areas that may serve as breeding areas is the best method for preventing outbreaks of Legionnaires’ disease. Most outbreaks of Legionnaires’ disease can be traced to specific points of exposure, such as hospitals, hotels, and other places where people gather. Sporadic cases are harder to determine and there is insufficient evidence to point to exposure in individual homes.

The likelihood of Legionella infection can be best reduced by good engineering practices in the operation and maintenance of air and water handling systems. Cooling towers and evaporative condensers should be inspected and thoroughly cleaned at least once a year. Corroded parts, such as drift eliminators, should be replaced. Algae and accumulated scale should be removed. These measures will not only control the growth of germs, but will also maintain operating efficiency.

During cleaning operations in confined spaces, safety procedures for entry into confined spaces should be applied. Face masks are a recommended option.

Cooling water should be treated constantly. Ideally, an automatic water treatment system should be used that continuously controls the quality of the circulating water.

The disinfectants commonly used in cooling towers are chlorine, dibromonitrilopropionamide, and ammonia derivatives called quaternary ammonium compounds. They appear to be effective in laboratory tests, but their value in practice has not been completely proven. It is important that any disinfectant used in a cooling tower water system be compatible with the tower’s construction materials.

Fresh air intakes should not be built close to cooling towers since contaminated aerosols may enter the ventilation system. Air filters should be examined, cleaned and/or replaced periodically and tested for leaks. Cooling towers should be positioned so the drift or evaporate does not enter the fresh air intake. Hot water tanks, which might provide ideal conditions for the growth of Legionella, should be cleaned regularly. The water system should be flushed out on a regular basis to prevent the water from stagnating.

Control of Legionnaires’ Disease Bacteria in Cooling Towers and Air Washers:

Documentation of both mechanical and chemical safeguards are suggested for all buildings operating with cooling towers. A history of documentation and good records is a defense against possible litigation, if someone becomes infected.

Mechanical Safeguards

Cooling towers, evaporative condensers, air washers and their associated piping and heat exchange equipment offer excellent growth environments for all types of microorganisms. Some of this equipment, used in comfort air conditioning at sites of outbreaks of Legionnaires’ Disease, was found to be largely untreated and therefore heavily fouled.

The bacterium grows rapidly in a high oxygen, high nutrient, medium pH (6.9-7.0) environment. This environment is often present in a heavily fouled, untreated cooling system. The drift or mist from an infected cooling tower can be carried by the wind into building air intakes. At least one outbreak of the disease appears to have been caused in this manner.

The CDC also suggested that mechanical safeguards be built into cooling towers to prevent back-syphonage. Back-syphonage, the back- flow of non-potable water into potable water systems, may occur when there is a water below atmospheric pressure in a submerged potable water inlet to a tank of non-potable water. Submerged inlets connected to float valves are frequently found in cooling towers; and since many cooling towers are located on the top of buildings, the chance of low potable water pressure is greater than in other building locations.

An air gap with a vertical distance of twice the diameter of the water supply pipe above the overflow rim of the cooling tower reservoir is necessary to prevent any possibility of back-syphonage.

With some simple mechanical safeguards and the use of a properly designed water treatment program, Legionella pneumophila doesn’t have the opportunity to be a problem in any open recirculating system.

Clean Cooling Tower Systems Include Using Proper Microbicide:

Proper cooling tower maintenance should include a complete water treatment program including corrosion inhibitors, dispersants, pH control agents (if necessary) and microbicides. This approach is necessary for the optimum functioning of the biocides included in a program. The Center for Disease Control supported this ‘clean system’ approach in its Morbidity and Mortality Weekly Report of September 29,1978, which reads in part:

“It might be prudent to encourage adherence to recommendations that have been made for many years for satisfactory mechanical operation of small to medium size cooling towers and evaporative condensers which are used as part of the air conditioning systems for many public buildings and business establishments. Such units should be regularly treated with chemicals that have been tested and shown to be effective in preventing slime, corrosion, algae and high population of bacteria in cooling water or on water contract surfaces.  Individuals or contractors skilled in maintenance of cooling towers should monitor treatment on a regular basis to assure that it has been carried out.”

In its Morbidity and Mortality Weekly Report of June 22, 1979, the CDC cites their tests of didecyl dimethyl ammonium chloride (a quaternary amine) and 2, 2′-dibromo-3-nitrilopropionamide. According to this report, the quarternary ammonium based microbicide was tested at normally recommended dosage rates and exposure times.  Under these conditions, this microbicide was effective in preventing recovery of Legionnaires’ Disease bacteria from the water. Testing was less complete on the nitrilopropionamide based microbicide but initial results also showed it to be effective against the bacteria. In addition to the biocide properties of these compounds, they have cleaning capabilities.

We regularly use and market both of these compounds, and others, that help to keep cooling towers clean.

Control of Legionairres’ Spas and Wirlpools: 

[8] [9] Table 1 lists the bacteria and associated infections/diseases found in swimming pools and spas. Legionellosis is found most in heated spas which like cooling towers are sources of warm to hot water. The other organisms listed will also be found in cooling towers that are not properly treated with an effective biocide program.

Types of Biocides:

As a broad classification, biocides can divided into two types, Non-oxidizing and Oxidizing:

Non-Oxidizing Microbiocides.

There are very few direct tests for these compounds. In the past, the marketplace was not mandated to measure the actual biocide content of the water. This is changing and microbiocide content in will be a required test parameter for cooling water. Governmental restrictions have already been proposed in general for microbiocide content of cooling water discharge and in some cases NPDES permitting or local ordinance the content is already regulated.

Quat and Poly Quat analysis tests are available for these charged cationic products. Both are measurable with low level detection feasible. Samples should be filtered to remove gross contaminants. Quat analysis can be affected by higher iron or hardness levels. Dilution of the samples may be required before an accurate Quat value can be determined.

Glutaraldhyde tests are readily available, easily done and accurate. Pretreatment filtration is recommended with higher iron and hardness values causing erroneous test results.

DBNPA analysis is another non-oxidizing microbiocide test that is available. DBNPA tests are also subject to interference from higher iron, suspended solids or small amounts of free halogen being present. DBNPA analysis should be done quickly and efficiently to minimize the hydrolysis of the DBNPA compound during the test. Generally, DBNPA testing should be done within a minimal amount of time so that you do not understate the residual DBNPA present.

Oxidizing Microbiocides:

Simple and quick tests are available for Chlorine/Bromine. Be sure that the test purchased reflects the halogen control range, do not use a low level Chlorine test to measure higher levels of Chlorine, your error factor will be great.

Generally, as a microbiocide it is the “Free Chlorine” or “Free Halogen” value that is critical and not the “Total Chlorine” or “Total Halogen” value. When using Bromine or the hydantoin Bromine/Chlorine compounds use a combined “Free Halogen” value of 0.5 to 1.0 ppm as your control and use a test procedure that equates to the Bromine found.

Reagent systems for halogen analysis are stable for long periods of time but they should not be exposed to elevated temperatures or to moisture for long periods of time. Other microbiocides present in the sample may cause a precipitation or reaction with the reagent system.

Higher amounts of iron in the sample at times may pose a problem. Quick filtration of the sample will usually overcome this.

Measuring Biocidal Effectiveness:

Keep in mind that any test method of the flowing water does not indicate the true amount of bacteria in the system if there is slime buildup on the tower sides or tower slats.  Legionella hides in the slime buildup. Thus, cooling towers should be kept clean to eliminate many problems that may not observed in the flowing tower water alone.

During the last several years Dip Slide monitoring have been used extensively. Dip Slides do not test for the microbiocide in a cooling tower, but for the active colonies contained in the water. The Dip Slides relate to the effectiveness of the microbiocide being used. If the colony counts are low, then it is perceived that the microbiocide is effective. These are very good trend check analysis tools. Incubation can be completed in as little as 24 hours and is visual. The very severe bacteria and corrosion problems encountered with Sulfate-reducing bacteria can be monitored with a cultured test with results in 48 hours. Handling and care of the Dip Slides is critical! They are delicate agar media is easily destroyed by temperature, light and jostling. Dip Slide counts are not definitive, they are only a trend check technique and do not represent the actual total planktonic or sessile microbial activity that may be present.

ATP analysis is used as a tool for measuring microbiocidal effectiveness. The test is easy to do, requiring only a set of reagents and an ATP metering system. Using ATP analysis is similar to Dip Slides or testing in that ATP analysis should be utilized to measure the trend of microbiocidal effectiveness rather than using the value found as a hard number posture that there is or is not quantities of microbial activity.

Legionella analysis should only be done by qualified and certified laboratories. There are several “field test” methods now available, but the analytical tolerance of the tests and the specific Legionella microbes they are measuring can lead the untrained analysts into false conclusion as to the presence and scope of the Legionella. Sample points and the care one takes in taking representative samples for microbial effectiveness analysis are critical issue. Sample points with dead legs, sample points that are not fully flushed, dirty bottles or poor sampling techniques in general result in false microbiocidal effectiveness values and perceptions. Exposure of the samples taken to stressed, elevated temperature storage or direct sunlight for any period of time results again in aberrant microbiocidal effectiveness values and perceptions.

CHAIN OF CUSTODY:

Must contain sampling date, time sampled, and sample source. This is needed to determine whether or not samples are within hold times and analysis procedure. If looking for total coliforms, please inform us if you would like Presence/Absence (Colilert) or Enumeration (MFT-Membrane filtration technique). We can supply chain of custody documents.

SAMPLE COLLECTION FOR BACTERIA TESTING:

All water samples must be taken in approved, sterile sampling containers, which our laboratory can provide upon request. Treated (municipality / distribution systems) water samples must be de-chlorinated with sodium thiosulfate (this is already in bottles that would be provided by our laboratory). Keep sampling bottle closed until it is to be filled. DO NOT RINSE THE BOTTLE: The preservative or sodium thiosulfate pill will be lost.

Distribution or sink tap samples:

1. Remove aerator for faucet

2. Rinse faucet with a bleach solution

3. Flush line- by turning tap fully on and letting it run for 2 to 3 minutes, or for a time sufficient to permit clearing the service line

4. Reduce water flow to permit filling bottle without splashing

5. 100mL is needed for each sample submitted for analysis

Well samples:

If a sample is taken from a well fitted with a hand pump, pump water to waste for about 5 minutes before collecting sample. If the well is equipped with a mechanical pump, collect sample from a tap on the discharge. If there is no pumping machinery, collect sample directly from the well by means of a sterilized bottle fitted with a weight at the base; take care to avoid contaminating sample by any surface scum.

Legionella sp.:

Collect water sample from the littoral zone or from the cooling towers,condenser coils, storage tanks, showers, water taps, etc. In most instances, a 1 liter water sample is sufficient.

Hold Times:

• Fecal coliforms must be run within 6 hours of samples collection.
• Total coliforms, E. coli , Fecal streptococcus, Sewage Screen, Legionella sp ., and Heterotrophic Plate Count samples need to be run within 24 hours of sample collection.

If client is aware that hold times are going to be exceeded but would like analysis anyway, please indicate this on the Chain of Custody. If hold times are exceeded results are invalid and this will be noted on reports.

Turn Around Times:

• Total coliform-Presence/Absence (Colilert): results can be given in 24 hours.
• Total coliform enumeration (MFT), Fecal coliform, Sewage Screen and Legionella sp.: results in 6-10 days.

Sample Shipping:

All samples must be shipped cold, not frozen and should remain up right. The best method of shipment for these samples is to use ice packs: not soda bottles filled with frozen water, bags of ice or just loose ice.

Samples that are not shipped properly could end up getting contaminated or rejected.

Definitions

Antibody:

A molecule created by the immune system in response to the presence of an antigen. It serves to recognize the invader and help defend the body from infection.

Antigen:

A molecule, such as a protein, which is associated with a particular infectious agent. The immune system uses this molecule as the identifying characteristic of the infectious invader.

Colony Forming Units:

Legionella is reported as the number of Colony Forming Units per Milliliter (CFU/mL) of sample.

Culture:

A laboratory system for growing bacteria for further study.

DNA probe:

An agent that binds directly to a predefined sequence of nucleic acids.

Immunocompromised:

Refers to conditions in which the immune system is not functioning properly and cannot adequately protect the body from infection.

Immunoglobulin:

The protein molecule that serves as the primary building block of antibodies.

Immunosuppressive therapy:

Medical treatment in which the immune system is purposefully thwarted. Such treatment is necessary, for example, to prevent organ rejection in transplant cases.

Legionellosis:

A disease caused by infection with a Legionella bacterium.

Media:

Substance which contains all the nutrients necessary for bacteria to grow in a culture.

Phagocytosis:

The “ingestion” of a piece of matter by a cell.