Thursday, December 8, 2016

Another Health Issue You Can Get Without Ever Smoking

by JW

           My generation has grown up being told that smoking is bad for you and it causes countless ailments. One thing that no one thought to warn us about is microbes that can cause things such as acute respiratory distress syndrome, and the dimorphic fungus Blastomyces dermatitidis is one of those microbes. It was first found in Canada in 1910 but as also been found in Midwestern and southern United States as well as parts of Canada that are along bodies of water like the Great Lakes (1). Diagnosis and identification of this fungus is primarily done from a histological exam on sputum or bronchial washings where they are looking for a broad-based budding yeast with refractile cell walls (2). When asexually reproducing by budding, often the daughter cells are as large as the mother cell before detachment. Patients that come into a hospital with an infection of B. dermatitidis often aren’t diagnosed until it is too late. In a study from a rural area of northwestern Ontario, Canada, A 27-year old woman went to an emergency department with signs of labored breathing and decreased air entry into the left upper lung (2). The first few days of being in the hospital the patient was stable, but after five days the hospital staff requested that the patient be airlifted to an intensive care unit in another facility. After only being in the intensive care unit for a day the patient went into cardiac arrest, and the cause of death was determined to be from acute respiratory distress syndrome.
                        While some infections of B. dermatitidis result in hospitalization, most infected patients remain asymptomatic (3). A more common illness caused by B. dermatitidis is Blastomycosis and is caused by inhaling the fungus from the environment in its mold phase and it converts to a yeast phase in the lungs. Often patients that have symptoms of Blastomycosis aren’t correctly diagnosed because the illness can mimic those of bacterial pneumonia, acute respiratory distress syndrome, or tuberculosis. Symptoms of blastomycosis typically appear after two to six weeks of incubation of the yeast phase in the lungs. Most often it involves the lungs and approximately 50% of pulmonary infections do not require treatment, however blastomycosis can affect nearly every organ including the skin, bones, eyes, and others. Symptoms of the illness are only considered a confirmed illness when the symptoms persist even after multiple courses of antibacterial therapy. Patients with an acute case are often given antibacterial medications and experience improvement within two to three weeks. This improvement is actually from the self-limited nature of the infection and not from the treatment with antibacterial medications.  
            A survey in Wisconsin showed that the average annual incidence for blastomycosis was 40.4 per 100,000 persons in one county (3). However, mandatory public health reporting for this illness is not required everywhere. It is only required in six states in the United States and only two Canadian provinces, making the true rate of occurrence of this infection in humans unknown. However, while we don’t know the true infection rate in humans, we do know that B. dermatitidis also infects animals, and especially dogs. In the same areas of Wisconsin where they reported blastomycosis, they also reported canine cases to be high at the same rate. One report even showed that as many as a third of patients who had blastomycosis and owned a dog reported that their dog was diagnosed with blastomycosis, some times even before the patient themselves (3).
            While the fungus B. dermatitidis is in its mold phase in nature it produces conidia, which are spores that are produced from asexual reproduction and are placed at the end of branching filaments called hyphae. This structure is shown in the picture below. The conidia are aerosolized during activities where the soil or decaying wood are disturbed. There are occupational risk factors for the blastomycosis disease. People that live in densely wooded areas with moist soil, open bodies of fresh water, and those that spend a large amount of time in these outdoor environments are at a higher risk of inhaling the aerosolized conidia. There is a higher amount of cases reported in men than in women and that most likely has something to do with men having more of an exposure to the environment with jobs that require moving wood and farming.
            The virulence of B. dermatitidis is difficult to evaluate given that the clinical course of blastomycosis is seen to be correlated with the amount of aerosolized conidia initially inhaled. Without consistency for the amount of inoculum inhaled in the cases reported, it is difficult to tell if the difference in the disease process is from the virulence of from the amount that was inhaled. This means that it is difficult to tell if acute respiratory distress syndrome is caused from a prolonged infection with B. dermatitidis conidia or if it the amount of conidia that the patient first encountered. Most cases of blastomycosis-induced acute respiratory distress syndrome follow weeks to months of symptoms for pneumonia before development as seen in the case study of the 27 year old woman from rural Ontario, Canada.
This map above shows the areas that B. dermatitidis is located at in blue. As shown from the multiple reports out of Wisconsin and the map above, the area of this state is surrounded by the Great Lakes along with having lakes in the state itself. The other factor of decaying wood being a source for conidia is also very common for Wisconsin as the state is 46% covered in trees. With the ecosystem like this in Wisconsin it’s no wonder that there is such a high reporting of blastomycosis (4). There are occupational risks for those working outside in the south and Midwestern regions of the United states and Canada because we still aren’t able to understand how the virulence of the fungus comes into play for how the infection of B. dermatitidis. It can either be a mild form of blastomycosis that is asymptomatic or a life threatening illness such as acute respiratory distress syndrome which leads to complications. While the dangers of smoking are still ever present, there are a few other things to watch out for that can cause lung problems, especially if you work outside in Wisconsin.

(1) Kroll, R. R., & Grossman, R. F. (2013). Pulmonary blastomycosis in a professional
diver: An occupational risk. Canadian Respiratory Journal : Journal of the Canadian Thoracic Society20(5), 340–342.
(2) Dalcin D, Rothstein A, Spinato J, Escott N, Kus JV. Blastomyces gilchristii as cause
of fatal acute respiratory distress syndrome. Emerg Infect Dis. 2016 Feb [11/5/16].
(3) Castillo, C. G., Kauffman, C. A., & Miceli, M. H. (2016). Blastomycosis. Infectious
Disease Clinics of North America, 30(1), 247–64. doi:10.1016/j.idc.2015.10.002
(4) Natasha Kassulke, K. E. (2005). Fast forestry facts -- Wisconsin Natural Resources magazine -- December 2005. Retrieved from

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