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Patterns in Descriptive Epidemiological Variables in Blastomycosis Outbreaks By: Bill Luebke Epidemiology Abstract Blastomycosis is a disease caused by the dimorphic fungus called Blastomyces dermatitidis. It exists in mold form and is found in decaying vegetation, animal and bird excrement, and organic debris. There are many small outbreaks of blastomycosis throughout the United States, Mexico, and Canada. I completed a cross-sectional study by researching specific case studies and analyzed these studies to find any descriptive epidemiological patterns between the outbreaks: age, race, gender, and location. Men aged 40 years old, of any race have a higher incidence rate to blastomycosis. 60% of males in the case studies were more likely to get blastomycosis than females. The median age for all case studies was 40.9 years of age. There was a very wide range of patients that were diagnosed with blastomycosis; from 4 months to 95 years of age. A correlation between race and blastomycosis was not found because there was insufficient information provided to make any comparisons. Most common incidences occurred in rural, wooded, and riverbed areas. Description of Disease Blastomycosis is a disease caused by the dimorphic fungus called Blastomyces dermatitidis. It exists in mold form and is found in decaying vegetation, animal and bird excrement, and organic debris. According to the Canadian Material Safety Data sheet (2010), “the infection develops when conidia of Blastomyces dermatitidis are aerosolized from soil.” The spores are either inhaled or planted into the skin of a susceptible human or animal at 25 degrees Celsius. The warmer temperature of the host transforms the mold into yeast once it reaches 37 degrees Celsius. The yeast may continue to colonize the lungs and cause adult respiratory distress syndrome (ARDS) and/or obstructive lung disease. It may spread into the bloodstream and cause damage to other parts of the body, skin, bones, joints, organs, or the central nervous system. It can even cause death. Description of Symptoms and Diagnoses From the date of exposure to the onset of symptoms is the incubation period. The CDC (2014) claims that the symptoms can occur between “3 -15 weeks after being exposed.” The symptoms that can occur after exposure to Blastomyces dermatitidis vary greatly. Symptoms to different body parts include: cutaneous, bone, central nervous system, and other sites of infection. According to the CDC (2014), only 50% of the people exposed will actually have symptoms. Some symptoms are very similar to flu like symptoms; including fever, chills, cough, muscle aches, joint pain, chest pain, weight loss, and fatigue. Most people diagnosed with blastomycosis also have skin symptoms, such as, pustules. Pustules are small grayish bumps resembling warts on the skin that fill with fluid or pus. The pustules are typically painless, although they can eventually lead to scarring of the skin. In serious cases the fungus can spread to the “long bones, vertebrata, ribs, and the cranium in the form of osteomyelitis with dissemination to the joints, where it may cause septic arthritis.” In the central nervous system, “patients may manifest signs of meningitis, cerebral abscess, or granuloma formation associated with the presence of Blastomyces dermatitidis.” Other body parts that can exhibit symptoms are the “breasts, eyes, ears, thyroid, adrenal glands, myocardium, pericardium, or digestive tract (Lopez-Martinez, Mendez-Tover 2012).” Description of Treatment Depending on the severity of the symptoms and diagnosis, medicine may or may not be needed. According to Lopez-Martinez and Mendez-Tovar, “treatment should be prescribed without exception to all patients with pulmonary blastomycosis, systemic dissemination to any organ, and immunosuppression (2012).” Triazole drugs are prescribed for patients with mild pulmonary symptoms with a “cure rate of 90%-95%” after 2-6 months of use. Other mild forms can just be monitored by the patients’ physician. In patients who have severe pulmonary blastomycosis, amphotericin B is prescribed. After the patient finishes the amphotericin B, they must follow that up that up with several months of the triazole drugs. “Immunosuppressed patients are advised not to travel to endemic zones and to avoid contact with dogs in these regions, due to reports of transmission of disease through dog bites (Lopez-Martinez, Mendez-Tovar 2012).” Description of Environment According to Dworkin, Duckro, Proia, Semel, and Huhn, (2005) Blastomyces dermatitidis can be found throughout the world, but is most common in parts of North, Central and South America. In the United States it is typically found in the Southeast and Midwest. More specifically, the fungus is found in regions surrounding the Mississippi River, the Great Lakes area, and the Ohio River. There have also been outbreaks in Wisconsin, Illinois, New York, Louisiana and Colorado. The fungus has also been reported worldwide; Canada, Africa, England, and India. Even though the fungus is primarily found in rural locations there have been endemic outbreaks in non-rural areas near yard waste collection and composting facilities, especially where pine tree litter is present. “Environmental and meteorological conditions and material management practices were identified that may have facilitated growth and dispersal of B. dermatitidis conidia near this residential area (Phister, Archer 2010).” Description of Susceptibility People who live in endemic areas and engage in activities that expose them to woods or river banks are at a higher risk. Studies have shown that occupationally, farmers and forestry workers are the most common professions exposed. People who partake in rural activities such as hunting, fishing, gardening, hiking, and camping are more susceptible than non-rural activities. According to CDC.gov (2014), anyone can be exposed to Blastomyces dermatitidis but patients with underlying defects in T cell and other personal health issues are more susceptible. According to cmr.asm.org (2014), “B. dermatitidis appears no more likely to cause disease in a person with compromised cellular immunity than to cause disease in a normal host. The presence of natural defenses against inhaled conidia in the lung may explain this observation. When blastomycosis does occur in immunocompromised patients, the disease is more aggressive than in immunocompetent hosts.” Outside of humans, canines are the most commonly affected but other animals such as cats, tigers, lions may also develop the disease. Description of Exposure According to the CDC (2014), Blastomyces dermatitidis is found in soil and molds which enter the body through inhalation of asexually produced spores into the respiratory tract. Other rare forms of transmission included, inoculation, dog bites, conjugal transmission, and intrauterine transmission. Conclusions Leading to a Hypothesis Based upon my research of blastomycosis thus far, I have found that most case studies have specifically focused upon only one aspect of descriptive epidemiology: geographical location of the exposure to explain epidemiological outbreaks. I believe that this is because blastomycosis can only occur in certain geographical locations throughout the world, and more specifically, in certain parts of the United States and Canada. This is where I feel there is a gap in the research. I am going to use historical data and a cross sectional study to research whether or not descriptive epidemiologic attributes contribute to incidence of blastomycosis. The descriptive epidemiological variables researched are: age, gender, race, location, and job specific incidents. Null Hypothesis: There is no correlation between age, gender, and race in incidence of blastomycosis. Predicted Outcome: The null hypothesis will be rejected. There will be a correlation between age, gender, and race after comparing specific case. There are many small outbreaks of blastomycosis throughout the United States, Mexico, and Canada. I completed a cross-sectional study by researching specific case studies and analyzed these studies to find any descriptive epidemiological patterns between the outbreaks. There were a total of 6 smaller outbreaks with 17 individual patients that were diagnosed with blastomycosis used in the report and one large outbreak in a county of Wisconsin from 1999-2005. In order to determine whether or not descriptive epidemiological variables such as age, gender, race, and location, contribute to incidence to blastomycosis, the specific case studies were compared to each other to determine any correlation between the descriptive epidemiologic variables. Brief Description of the case studies used: 1. Expanding Epidemiology of Blastomycosis: Clinical Features and Investigation of 2 Cases in Colorado Colorado Outbreak: The first outbreak that was researched was a small outbreak in Colorado. The two patients were coworkers working in the Front Range region of the Rocky Mountains. They were engaged in a prairie dog relocation project and were exposed to contaminated soil. The median age was 30. There were 2 males and 0 females during this outbreak. The race was not specified. Location Median Age Gender Male Female Race Occupation Colorado 30 2 (100%) 0 (0%) N/A Prairie Dog Relocation 2. Blastomycosis Tennessee Outbreak: This outbreak was a single case where the patient was a tire plant employee. The patient was a 28 year old male and his race was unidentified. Location Median Age Gender Male Female Race Occupation Tennessee 28 1 (100%) 0 (0%) N/A Tire Plant Worker 3. Blastomycosis imported to Monterrey, Mexico: fifth case reported in Mexico Mexico Outbreak: The outbreak consisted of 5 patients. Although, they traveled to and were diagnosed in Mexico, the patients were all originally from the United States. One of the patients was an over the road truck driver, the other 4 patients occupations was not disclosed. There were 5 males and 0 females diagnosed with blastomycosis. There was no race information and the median age was 38.8 Location Mexico Median Age Gender Male Female Race Occupation 38.8 5 (100%) 0 (0%) N/A N/A 4. The Epidemiology of Blastomycosis in Illinois and Factors Associated with Death Illinois Outbreak: A case study from Illinois tracked 500 cases of blastomycosis from January 1993 to August 2002. Of the 500 cases they selected 4 case studies. The median age was 36.25, there were 2 males and 2 unknown genders, and there were no races listed. Location Median Age Gender Male Female Unknown Race Illinois 36.25 2 (50%) 0 2 (50%) N/A 5. Pulmonary Blastomycosis: a New Endemic Area in New York State New York Outbreak: According to the research there have only been 3 people exposed to blastomycosis in the state of New York. Two of the cases occurred in 2012, and one occurred in 2007. The two cases that occurred in 2012 were in the same county. The median age of the outbreak was 42 years old. There were 3 males and 0 females, which mean 100% of the patients were males. The race of the patients was not listed. Location Median Age Gender Male Female Race New York 42 3 (100%) 0 (0%) N/A 6. Using Local Epidemiology to Make a Difficult Diagnosis: a Case of Blastomycosis Ontario Outbreak: This case study used one patient. This patient was a seasonal worker. He had recently quit working on a construction project clearing brush and digging ditches in Northwestern Ontario. The median age was 21, there was 1 male and 0 females, and no races listed. Location Median Age Gender Male Female Race Occupation Winnipeg 21 1 (100%) 0 (0%) N/A Excavator/Construction 7. Blastomycosis-Wisconsin 1986-1995 Wisconsin Outbreak: Wisconsin has one of the highest rates of blastomycosis and is also a state that is required to report blastmycosis cases. During this time 636 cases of blastomycosis were reported to the DOH statewide. The median age is 46 years old for the cases in Wisconsin. There were 381 males and 254 females diagnosed with blastomycosis, which is 60% and 40% respectively. There was no data related to race of any of the outbreaks and occupations were Location Median Age Gender Male Female Race Occupation Wisconsin 46 381 (60%) 254 (40%) N/A Excavator/Construction Descriptive Epidemiological Patterns Race: In all of the case studies the race of the patients was not discussed in any of the studies. There have been no links between race and blastomycosis. Age: There were a wide variety of ages for the patients with blastomycosis throughout all of the case studies. The ages in all cases were very random. The ages ranged from 4 months – 95 years. The median age for all of the case studies was 40.9 years old. Gender: There were 395 males, 254 females, and 2 unknown genders in all cases. This is a large trend that shows more males are diagnosed with blastomycosis than females. Location: Each of the case studies took place in different locations. The locations were from Colorado, Mexico, Illinois, New York, Ontario, Tennessee, and Wisconsin. The case study in Colorado took place in the Front Range region of the Rocky Mountains. The Mexico outbreak states that the patients were traveling to endemic areas and that there was no confirmation of the exposure in Mexico. The case study in Ontario took place in Northwestern Ontario. He was a seasonal worker dealing with excavation. Of the 3 case studies in New York, 2 of the cases occurred in Otsego County and 1 occurred in Herkimer County. Both counties are not along the St. Lawrence River. The St. Lawrence River was an endemic area reported in dogs. None of the patients traveled from their resident counties. Overall Data Case Study Outbreaks (n=651) n(%) Gender Male Female Unknown Median Age Race 395 (60%) 254 (39%) 2 (.003%) 40.9 Years Not Known Conclusion Based on the above data, men aged 40 years old, of any race have a higher incidence rate to blastomycosis. 60% of males in the case studies were more likely to get blastomycosis than females. The median age for all case studies was 40.9 years of age. There was a very wide range of patients that were diagnosed with blastomycosis; from 4 months to 95 years of age. A correlation between race and blastomycosis was not found because there was insufficient information provided to make any comparisons. Most common incidences occurred in rural, wooded, and riverbed areas. In my opinion there are many reasons for this outcome. Men are more likely to work in endemic areas outside performing construction, excavation etc. than women. Men may also be more likely to have outdoor hobbies such as fishing, hunting, hiking, etc. Some of the outbreaks occurred due to the job duties of the patients. The job professions included Tanner, Excavation, Laborer, Prairie Dog Relocation, Truck Driver, and a Tire Plant Worker. The seasonal laborer and the 2 prairie dog relocaters worked directly with soil and brush. Since blastomycosis occurs mainly in people that work or have outdoor hobbies the occupations listed were not surprising. The original null hypothesis stated that there was no correlation between age, gender, race, and location in incidence of blastomycosis. The predicted outcome was that the null hypothesis would be rejected, and there would be a correlation between age, gender, race, and location after comparing statistical data. The null hypothesis was not entirely proven or disproven. There was a correlation between age and gender and blastomycosis. There was no correlation between race and blastomycosis. The rural, wooded, and riverbed areas did contribute to some incidence of blastomycosis but did not hold true for all cases. References Alkrinawi, S., & Pianosi, P. (2000). Pulmonary Function Following Blastomycosis in childhood. Clinical Pediatrics. 27-31. Retri eved from http://www.ncbi.nlm.nih.gov/pubmed/10660815 Anderson, J.L., Sloss, B.L., & Meece, J.K. (2013). Clinical and molecular epidemiology of veterinary blastomycosis in Wisconsin. BMC Veterinary Research, 9(84), 1-8. Retrieved from http://www. biomedcentral.com/1746-6148/9/84 CDC. (1996). Blastomycosis - Wisconsin, 1956-1995. Morbidity and Mortality Weekly Report, 45(28), 601-603. Retrieved from http;/ /ebscohost.com Centers for Disease Control and Prevention. (2010). Blastomycosis. Retrieved from http://www.cdc.gov/fungal/diseases/blastomycosis/ Crampton, T.L, Light, B., Berg, G.M., Meyers, M.P., Schroeder, G.C., Hershfield, E.S., & Embil, J.M. (2002). Epidemiology and clinical spectrum of blastomycosis diagnosed at Manitoba hospitals. Clinical Infectious Diseases, 34, 1310-1316. Retrieved from www .ncbi.nlm.nih.gov De Groote, M.A., Bjerke, R., Smith, H., & Rhodes, L.V. (2000). Expanding epidemiology of blastomycosis: Clinical features and investigation of 2 cases in Colorado. Clinical Infectious Diseases, 30, 582-584. Retrieved from http://www.ncbi.nlm.nih.gov/pubmed/10722448 Dworkin, M.S., Duckro, A.N., Proia, L., Semel, J.D., & Huhn, G. (2005). The epidemiology of blastomycosis in Illinois and factors associated with death. Clinical Infectious Diseases, 41, 107-1011. doi:http://www.ncbi.nlm.nih.gov/pubmed/16288388 Hicks, K., Smith, G.W., & Stinson, J.M. (1982). Blastomycosis. Journal of the National Medical Association, 71(1), 87-90. Retr ieved from http://www.ncbi.nlm.nih.gov/pubmed/7120447 Kemper, C.A. (2013). Environmental reservoirs for human infection. Infectious Disease Alert, , 33. Kesselman, E.W., Moore, S., & Embil, J.M. (2005). Using local epidemiology to make a difficult diagnosis: A case of blastomycosis. Canadian Association of Emergency Physicians, 7(3), 171-173. Laskey, W.K., & Sarosi, G.A. (1980). Blastomycosis in children. Pediatrics, 65(1), 111-114. Retrieved from http://pediatrics.aa ppublications.org/content/65/1/111.full.pdf Lopez-Martinez, R., & Mendez-Tovear, L. J. (2012). Blastomycosis. Clinics in Dermatology, 30, 565-572. Retrieved from http://dx.d oi.org/10.1016/j.clindermatol.2012.01.002 Permpalung, N., Kaewpoowat, Q., Prasidthrathsint, K., Chongnarungsin, D., & Hyman, C.L. (2013). Pulmonary blastomycosis: A new endemic area in New York state. Blackwell Verlag GmbH, 56, 592-595. Ret rieved from http://www.ncbi.nlm.nih.gov/pubmed/23496278 Pfister, J.R., Archer, J.R., Hersil, S., Boers, T., Reed, K.D., Meece, J.K., Anderson, J.L., Burgss, J.W., Sullivan, T.D., Klein, B.S., Wheat, L.J., & Davis, J.P. (2011). Non-Rural point source blastomycosis outbreak near a yard waste collection site. doi:1 0.3121/cmr.2010.958 Salas-Alanis, J.C., Martinez, M.F., Garcia-Melendez, M., Gonzalez, B.L., & Ocampo-Candiani, J. Mexico: (2013). Blastomycosis imported to Monterrey, Fifth case reported in Mexico. Mycosis, 56, 495-497. Retrieved from http://www.ncbi.nlm.nih.gov/pubmed/2337415