EPIDEMIOLOGY OF COCCIDIOIDOMYCOSIS
EPIDEMIOLOGY OF COCCIDIOIDOMYCOSIS
Background: Clinical Description
The disease causing agent, Coccioides spp., causes a wide range of illness, but these illness are mostly determined by the hosts' defenses, inoculum size and possibly specific organism virulence. Most of the clinical infections (about 60%) show few or no respiratory symptoms. However, the rest 40% may show symptoms of illness that may either be acute or sub-acute. The illness could range from progressive pneumonia to flu-like conditions. Misdiagnosis usually occurs in self-limited community-acquired pneumonia. According to Saubolle, McKeller & Sussland (2007), only 29% of 56 people who had community-acquired pneumonia were diagnosed of coccidioidomycosis.
The exact number of people infected with coccidioidomycosis is not known primarily because most of them do not eventually visit the clinic. The reason for this is because the symptoms of this disease usually begin between 7 and 21 days of inhaling anthroconidia. Symptomatic patients may show signs of cough, fever, chest discomfort, fatigue and malaise (Saubolle et al., 2007). Galgiani et al. (2005) pointed out that the acute or sub-acute community-acquired pneumonia which results from coccidioidomycosis usually becomes evident 13 weeks after the infection. The major challenge with the illness is that it is difficult to distinguish it from bacterial or other infections without particular laboratory examinations such as coccidioidal serological testing or fungal cultures.
Epidemiological Description
Coccidioidomycosis is caused by coccidioides immitis, a fungus commonly found in San Joaquin Valley in California. It is also caused by C posadasii which is commonly found in some arid and semi regions of the southwestern United States as well as in the northern regions of Mexico and some areas of Central and South America (Hospenthal et al. n.d). According to Saubolle et al. (2007), the coccidioides genus is considered dimorphic. This implies that it is characterized by the production of filamentous mycelia forms during its saprophytic phase in the environment and during rainy seasons. During this season, the genus grows more rapidly, but it is less harmful. However, it is converted into a yeast-like cellular form during its parasitic phase as it invades its animal host as obvious from epidemiological triangle (Figure 1). This takes place during dry seasons especially in hot dry regions of the southwestern United States. Coccidioidomycosis is not transmitted from person-to-person, person-to-animal or animal-to-person. Rather, the disease is caused by breathing in of the microscopic fungal spores in the air.
Figure 1: The epidemiological triangle
Impact of Coccidioidomycosis
The impact of coccidioidomycosis is largely concentrated in its endemic regions. The people can only be infected with this disease when they travel to endemic regions. Moreover, people who are immunocompromised such as HIV/AIDS, pregnant women, diabetics, and some race/ethnicities mostly Black Filipinos are mostly susceptible to the disease.
Coccidioidomycosis is primarily a disease of the Americans and as a result, it does not have a global impact. According to Hector et al. (2011), every year, an estimate of about 150000 in the United States become infected with the disease and 50000 develop the symptom, with Arizona having the highest number of reported cases. Furthermore, there has been a continuous increase in the impact of this disease locally in some regions of the North and South America. They also reported that the number of reported cases in Arizona more than doubled from 1990 to 1995 (255 to 623). On the other hand, in 2008, the reported cases were 4768. Several factors can be attributed to this abrupt increase, and some of these include soil disturbance due to the construction works following the increasing population in Arizona as well as the influx of susceptible individual into the population. In consideration of race and ethnicity, it can also be observed that the Blacks have the highest number of the disease incidence, and the rate has increased over time from 49/100000 to 67/100000 in 2006-2008 and 2009, respectively. The occurrence of the disease among Filipinos is also high.
Moreover, coccidioidomycosis has been observed to occur in non-endemic areas. Travelers sometimes become symptomatic shortly after returning home. Clusters of the disease have been observed in Pennsylvania and Washington State and some other non-endemic areas (Brown et al. 2013).
Health Care Professional’s Interventions
The intervention on coccidioidomycosis depends on whether it is symptomatic or non-symptomatic. According to Hospenthal et al. (n.d), most infections are self-limited and resolve within a few months without the need for medical intervention. Moreover, in over 90% of the symptomatic individuals, no further prognosis is usually done. However, the disease is usually treated with the use of antifungal therapy. This therapy is mostly effective in defined clinical syndromes.
Furthermore, the disease can become chronic. The chronic case develops in most patients with 5-8% of them having primary pulmonary disease. Moreover, Hector et al. (2011) pointed out that people who recover from coccidioidal infection had durable immunity. However, a sufficient number of physician and relevant education is required in the endemic regions, especially California and Arizona in order to further reduce the incidence. It is also necessary to set up more stringent surveillance and timely diagnostics examinations in order to reduce delays in diagnosis and also to provide the best treatment to those that develop the symptom at the right time. There is a great requirement for improved therapeutics and a preventive vaccine for coccidioidomycosis in order to reduce the economic cost attributed to the disease.
Travelers and immunocompressed folks should ensure that they do not inhale as much dust as possible when traveling through the endemic regions. Moreover, construction workers should also ensure that they apply the requisite preventive measures when working in endemic areas because of the risk of the disease infection.
Conclusion
Coccidioidomycosis is primarily a disease of the Americans with Arizona having the highest number of reported cases. Coccidioidomycosis is caused by coccidioides immitis and C posadasii. Symptoms of the disease include cough, fever, chest discomfort, and fatigue. It is hard to distinguish this disease from bacterial or other infections without laboratory tests. The people can only be infected with this disease when they travel to endemic regions. Most of the infected people recover within a few months without medical intervention. The acute form the disease can be treated with antifungal therapy. Travelers should prevent themselves from dust during traveling in the endemic regions.
References
Brown, J., Benedict, K., Park, B., & Thompson, G. (2013). Coccidioidomycosis: epidemiology. Clinical Epidemiology, 185-197.
CDC, (2016). Coccidioidomycosis. Cdc.gov. Retrieved 7 September 2016, from http://www.cdc.gov/fungal/diseases/coccidioidomycosis/
Galgiani, J., Ampel, N., Blair, J., Catanzaro, A., Johnson, R., Stevens, D., & Williams, P. (2005). Coccidioidomycosis. Clinical Infectious Diseases, 41(9), 1217-1223.
Hector, R., Rutherford, G., Tsang, C., Erhart, L., McCotter, O., & Anderson, S. et al. (2011). The Public Health Impact of Coccidioidomycosis in Arizona and California. International Journal of Environmental Research and Public Health, 8(12), 1150-1173.
Hospenthal et al., (n.d.). Coccidioidomycosis. Emedicine.medscape.com. Retrieved 7 September 2016, from http://emedicine.medscape.com/article/215978-overview
Saubolle, M., McKellar, P., & Sussland, D. (2006). Epidemiologic, Clinical, and Diagnostic Aspects of Coccidioidomycosis. Journal of Clinical Microbiology, 45(1), 26-30.
