Archive for the ‘Legionella’ Category

Legionnaires’ Disease – Significant Risk or Shiny Object?

This past summer, there was a cluster of Legionnaires’ disease (Legionellosis) cases in the Bronx. As most readers know, legionellosis is a disease that creates pneumonia-like symptoms caused by bacteria that belong to the species Legionella pneumophila. The species disease names both commemorate the sentinel outbreak that struck 221 attendees at the 1976 American Legion Convention in Philadelphia. Everything we know about Legionella today stems from the initial response to the 1976 outbreak.
Fast forward to the summer of 2015. In response to the cluster of cases in the Bronx, New York City issued emergency regulations and New York State is now drafting similar regulations.
Without diminishing the seriousness of the disease, it’s important to create a context. The Centers for Disease Control (CDC) reports incidence (morbidity) and death (mortality) statistics as incidence per 100,000 person-years (py) exposure (# of cases or # of deaths/100,000 people/year). The morbidity rate for Legionnaires’ disease 0.4 cases/100,000 py (all of the statistics in this post are approximations – epidemiology is an imprecise science). The mortality rate is 10 to 15% of the morbidity rate. By comparison, the morbidity rate for asthma 8,000 cases/100,000 py (mortality 8 deaths/100,000 py). Both diseases tend to occur in clusters and peak seasonally. Both are caused by inhalation. However, Legionnaires’ disease is an infectious disease (the symptoms are caused by a combination of direct and indirect effects of a microbe proliferating within the body) and asthma is typically allergenic (the body’s immune system reacts to inhaled substances). Now consider non-tuberculosis Mycobacteria (NTM). NTM are members of the genus Mycobacteria other than M. tuberculosis. Several NTM species are associated with pulmonary diseases (for example: hypersensitivity pneumonitis – extrinsic allergic aveolitis). The morbidity rate for NTM 2/100,000 py for the general population but can be as high as 20% among farm workers, pigeon breeders and other sectors of the population exposed to NTM sources.
All of these statistics can make your head spin. Morbidity and mortality rates mask the occurrence of disease clusters. Thus although L. pneumophila is ubiquitous, legionellosis typically occurs in clusters. The story for asthma and NTM infections is similar. So what is the shiny object? When a disease outbreak occurs, there is tremendous value in focusing on the immediate cause, but there’s also a need for maintaining a more global perspective. In her paper, presented at last month’s AWT Annual Convention, Diane Miskowski (EMSL Analytical, Inc.; reported – almost parenthetically – that increased numbers of NTM had been recovered from cooling towers which had been treated to kill off L. pneumophila. Are our efforts to control Legionella spp. in order to decrease our legionellosis risk may be increasing our risk of contracting other respiratory diseases? More on this in another post. I’d be interested in reading your thoughts.

Legionella pneumophila in Metalworking Fluids

I’m sharing an email exchange that I had with a colleague who had asked about the risk of L. pneumophila (the microbe that causes Legionnaire’s disease) in MWF.
Thank you for posting your query to BCA’s website.

You wrote:
“I wondered if you could help me answer a customer’s question. One of my customer’s machine tool operators is in the hospital being treated for Legionnaires’ disease. My customer asked me if the Kathon 886 MW or Kathon CC kills this strain of bacteria. I really appreciate your help and advice. I attend the annual STLE meeting every year and hear you speak on maintaining and monitoring metal working fluids, so I thought you would be the best source to ask. The Legionnaires’ disease was most likely contracted in Tennessee while this gentleman was on vacation. Other machine operators are now afraid they might contract the disease through the metal working fluids in the plant.
Thank you for your time and thoughts.”

The short answer is yes.

Not long after Legionella pneumophila was identified as the disease agent that caused Legionnaire’s disease, Rohm & Haas tested Kathon WT1.5 efficacy against the bacterium. WT1.5 is just Dow’s (formerly R & H) water treatment market label for the 1.5% active product we use as Kathon 886MW and 886MW 1.5 in the MW industry.

Keep in mind that L. pneumophila is ubiquitous. If you recall the incident at Ford’s Le Brea, OH plant some years ago, four machinists came down with Legionnaire’s disease. Attempts to detect L. pneumophila from MWF systems all failed. An immunological survey of all of the plant’s employees revealed that the majority has antibodies to L. pneumophila. Other immunological surveys (populations outside our industry) have demonstrated that the majority of the population has been exposed to the microbe (i.e.: has the antibodies). Most of the time, folks who contract the disease have other health problems that render them more susceptible than the general population. Back to Le Brea. That incident and a cluster of Pontiac Fever cases at a Pontiac Plant in Windsor Ontario in 1981 are the only two clusters of Legionnaire’s disease that have been reported in the MW industry. The 1981 outbreak was caused by L. feeleii growing in the facility’s cooling towers. The source of L. pneumophila at Le Brea was never confirmed.

From what we know, workers are much more likely to be at risk from improperly controlled heat exchange systems/cooling towers than from MWF.


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