* Your assessment is very important for improving the workof artificial intelligence, which forms the content of this project
Download histoplasmosis paper final - Concordia University, Nebraska
Henipavirus wikipedia , lookup
Tuberculosis wikipedia , lookup
Clostridium difficile infection wikipedia , lookup
Carbapenem-resistant enterobacteriaceae wikipedia , lookup
Chagas disease wikipedia , lookup
Foodborne illness wikipedia , lookup
Neglected tropical diseases wikipedia , lookup
Cryptosporidiosis wikipedia , lookup
Dirofilaria immitis wikipedia , lookup
West Nile fever wikipedia , lookup
Diagnosis of HIV/AIDS wikipedia , lookup
Onchocerciasis wikipedia , lookup
Marburg virus disease wikipedia , lookup
African trypanosomiasis wikipedia , lookup
Microbicides for sexually transmitted diseases wikipedia , lookup
Sarcocystis wikipedia , lookup
Hepatitis C wikipedia , lookup
Eradication of infectious diseases wikipedia , lookup
Human cytomegalovirus wikipedia , lookup
Epidemiology of HIV/AIDS wikipedia , lookup
Leptospirosis wikipedia , lookup
Sexually transmitted infection wikipedia , lookup
Hepatitis B wikipedia , lookup
Middle East respiratory syndrome wikipedia , lookup
Trichinosis wikipedia , lookup
Neonatal infection wikipedia , lookup
Schistosomiasis wikipedia , lookup
Fasciolosis wikipedia , lookup
Lymphocytic choriomeningitis wikipedia , lookup
Hospital-acquired infection wikipedia , lookup
Running head: THE EPIDEMIOLOGY OF HISTOPLASMOSIS The Epidemiology of Histoplasmosis Katelyn Strasser September 26, 2013 Applied Epidemiology MPH 510 Concordia University Nebraska THE EPIDEMIOLOGY OF HISTOPLASMOSIS Histoplasmosis is a fungal infection that in humans is caused by one of two subspecies of Histoplasma capsulatum. Although this infection can be acquired many places throughout the world, it is endemic in parts of Africa, Asia, in Central and South America, and in North America in the Mississippi and Ohio River Valley (Luo et al., 2012). In the United States, histoplasmosis is the most common endemic fungal infection found in humans, infected around 250,000 people each year. Histoplasmosis is often asymptomatic in people with the illness, presenting symptoms in just 5% of those infected (Fayyaz, 2013). However, it is becoming an increasing significant public health concern as healthy individuals and those immunocompromised are being treated for the illness in a growing number of countries. H. capsulatum is usually found in soil, and most often in soil that is contaminated with bird or bat droppings. The microorganism may harbor in soil for years (Luo et al., 2012). Humans acquire the illness when they inhale the H. capsulatum spores from soil (MMWR, 2012). Areas endemic for the infection share a characteristic humid and temperate climate, which allow for the microorganism’s growth. Places with high rates of infection are usually associated with activities that disturb the soil or that have bird or bat droppings. Activities such as archaeology, ploughing, and construction work can overturn soil and allow the fungal spores to spread (Norman et al., 2009). Bat and bird droppings actually bolster the growth of the microorganism by increasing the rate of sporulation (Baddley et al., 2011). 2 THE EPIDEMIOLOGY OF HISTOPLASMOSIS In areas where histoplasmosis is endemic, 50-80% of people who live there show proof, through laboratory testing, of having had the infection at one point. It is difficult for epidemiologists to calculate morbidity and mortality rates for this infection because many people remain asymptomatic. Furthermore, symptoms similar to pneumonia often mask the true identity of the illness (CDC, 2012). The incubation period is anywhere from three to seventeen days and symptoms may include, fever, chest pain, a dry or nonproductive cough, joint pain, and anorexia. More life threatening symptoms can occur if the disease disseminates throughout the body. Luo et al. (2012) writes that the infection is diagnosed through the “detection of the fungus in organic fluids or tissues, culture of biological samples, and serologic assays.” Treatment is usually a type of anti-fungal antibiotic. (Luo et al, 2012). H. capsulatum skin tests have provided positive results for similar numbers of men and women. Women with the disease seem to develop more rheumatologic complications. Anyone can contract histoplasmosis, but it occurs more often in immunocompromised people and others with weaker immune system such as young children and the elderly (CDC, 2012). Progressive disseminated histoplasmosis is more common in the immunosuppressed patients, resulting in 1 case per 2000 adults from this group (Loulergue, et al., 2007). Although it is difficult to identify the incidence and prevalence of the disease in the United States, one study found the cumulative incidence of cases of the illness that required hospitalization. The study found the cumulative incidences for both children and adults, according to regions of the country. Figure 1 shows that the 3 THE EPIDEMIOLOGY OF HISTOPLASMOSIS highest incidences were in the Southern and Midwestern parts of the United States. For example, the cumulative incidence of the number of children that needed to be hospitalized because of histoplasmosis in the Southern part of the United States was 3.05. The cumulative incidence in the Midwestern part of the United States was 27.08 in 2002. Table 1 highlights the demographic and clinical features of children and adults hospitalized for histoplasmosis and other endemic mycosis in 2002. According to this data, adults are affected more often than children, and the number of cases affecting white adults more than doubled the cases of other ethnicities. As expected, many of these patients were already immunocompromised (Chu, Feudtner, Heydon, Walsh, & Zaoutis, 2006). Other epidemiological studies of the illness have focused on specific populations such as the elderly, HIV positive individuals, travelers and immigrants, those who work in occupationally hazardous, and others living in endemic areas (Loulergue, 2007). The weakened immune systems of many elderly people cause them to be more susceptible to histoplasmosis and other fungal infections. A retrospective cohort study was conducted to find statistics on three fungal infections in elderly. The study used claims data from 1999-2008 that was taken from a “random 5% national sample of Medicare beneficiaries” (Baddley et al., 2011). All of the participants had certain selection criteria, including being age 65 or older at the beginning of the study. Along with histoplasmosis, coccidoidomycosis and blastomycosis were also studied in this research. 357 of the 1,913,247 people studied were found to have histoplasmosis. Out of the almost two million people, the mean age was 75.7 years and a little over half of the patients were male. 4 THE EPIDEMIOLOGY OF HISTOPLASMOSIS Common co-morbidities of this disease included COPD, diabetes mellitus, solid malignancy, and rheumatoid arthritis (Baddley et al., 2011). Among this cohort, the incidence rate of histoplasmosis was 3.3. This was the highest incidence rate among the three mycosis. Geographic distribution maps showed definitive areas of higher rates of histoplasmosis (Figure 2). The Midwest had the highest incidence rate at 6.1, with rates of 13.0 and 12.0 in Indiana and Arkansas, respectively. Although many of the cases occurred in traditional histoplasmosis endemic areas, some of the cases were reported in non-endemic areas. This suggests that additional research is needed to understand why people living in non-endemic areas are contracting the illness. Another conclusion from this study is that immunosuppression plays a major role in this patient population. Since people are living longer, the elderly are more likely to be immunosuppressed because of pending transplantation or from receiving chemotherapy or immunosuppressive drugs due to other conditions (Baddley et al., 2011). Increased longevity may also allow older people to travel to areas where they are exposed to H. capsulatum. Travel to an endemic area is certainly a risk factor for acquiring the illness. One outbreak of histoplasmosis in a group of travelers in Nicaragua illustrated that the illness can occur in young, healthy individuals as well. In this case, a group of travelers contracted histoplasmosis while visiting a small cave that had live bats and bat guano on the ground. The infection rate of this group was 100%, as 14 of the 14 travelers tested positive for the illness. Contrary to other studies, the majority of those infected showed symptoms (12 out of 14). Half of the symptomatic persons developed mild to moderate respiratory distress, measured 5 THE EPIDEMIOLOGY OF HISTOPLASMOSIS by the patient’s oxygen saturation. Interestingly, the two people who were asymptomatic had prior exposure to bats or caving (Weinberg et al., 2003). Other research has suggested that exposure provides partial immunity later in life (Baddley et al., 2011). No substantial differences in symptoms were attributed to sex, previous spelunking, residence in areas endemic to histoplasmosis, or activities while in the cave. This outbreak demonstrates the risk of histoplasmosis as a travelrelated illness. It shows that when exposed to high concentrations of H. capsulatum spores, even groups of healthy travelers from areas of low histoplasmosis prevalence can have high attack rates of the illness and develop symptoms (Weinberg et al, 2003). Increased travel due to tourism and immigration has brought histoplasmosis to areas that were not formerly endemic. Europe in particular has found many recent cases of the disease in people traveling to the continent. In fact, histoplasmin skin tests have given evidence that the incidence of Europeans who have traveled to Latin American countries may have an infection rate of as high as 20%. Clinical manifestations of the disease vary from patients being asymptomatic, to the disease spreading and causing systemic problems. Most Europeans with the illness can be placed into one of two categories. Some are people who have traveled to endemic areas, were exposed to spores, and develop short-term effects of the illness from which they recover. The second group is comprised of immigrants or expatriates from endemic regions who are immunosuppressed. Much of the immunosuppression occurs because the same person also has HIV. The illness is particularly dangerous for these patients, as these people are more likely to develop 6 THE EPIDEMIOLOGY OF HISTOPLASMOSIS disseminated forms of the infection with mortality rates up to 50%. (Norman et al., 2009). Because symptoms of histoplasmosis are commonly seen in HIV patients, this infection is actually an AIDS-defining opportunistic infection. Before HIV positive patients received the highly-active antiretroviral therapy (HAART), the prevalence of histoplasmosis in HIV infected individuals was around 30%. Histoplasmosis is more common in patients with CD4 counts below 50/mm3, and it usually spreads throughout the body, even appearing on the skin as lesions (Loulergue et al., 2007). A second type a organism that causes histoplasmosis is H. capsulatum var. duboisii. All of the examples so far in this paper have been based on H. capsulatum var. capsulatum. This second variety is much more rare, with Africa being the only continent to produce the illness. For this reason, it is sometimes called the African histoplasmosis. Although H. capsulatum var. capsulatum is often seen in patients with HIV, the coinfection of African histoplasmosis and HIV is rare, even with the overwhelming number of people infected with HIV in Africa. Literature has documented less than 300 cases, and the prevalence of the variety duboisii has not been researched in Africa in HIV-negative patients. The reason for this variety’s rarity is unknown, but some speculate that AIDS victims die before the histoplasmosis develops or that capsulatum is more potent than dubuoisii. Those HIV positive people that do contract the disease usually present with manifestations of the infection in other places besides the lungs. Locations of the infection for HIV positive patients are lymph nodes, skin, bones, in the gastrointestinal tract, and other places throughout the body, but none appear in the lungs. Those that contract 7 THE EPIDEMIOLOGY OF HISTOPLASMOSIS the illness but do not have HIV find the virus within their lungs, causing respiratory symptoms (Loulergue et al., 2007). No matter the variety of histoplasmosis that occurs in African nations, it is undoubtedly a very risky illness for these people to acquire, with so many of them also having HIV. The histoplasmosis skin test has shown a 3% prevalence in areas endemic to he infection. Rural populations have shown an even higher prevalence of around 35%, especially in people in work in occupations where environmental exposure to the fungus is evident. The occurrence of both types of histoplasmosis in Africa continues to be researched (Loulergue et al., 2007)). As mentioned within the African population, contraction of histoplasmosis can be an environmental occupational hazard. Any occupation that exposes workers to soil contaminated with bird or bat droppings, especially in endemic areas, can pose a greater risk of infection. These types of jobs include bridge inspector, construction worker, farmer, pest control worker, spelunker, and many more. The spores of H. capsulatum are not stagnant, and can actually be carried long distances by the wind when dust is disturbed. Airborne travel of spores is blamed for the three largest outbreaks of histoplasmosis ever noted in history. All three outbreaks, occurring in 1979, 1980, and 1988, took place in Indianapolis, Indiana. In 1979, 120,000 people were infected by the illness, resulting in 15 deaths. Half of the victims in the third outbreak were AIDS patients. Workers are encouraged to wear personal protective equipment as recommended by the National Institute for Occupational Safety and Health (NIOSH) and avoid contaminated soil when possible (Lenhart, Schafer, Singal & Hajjeh, 1997). 8 THE EPIDEMIOLOGY OF HISTOPLASMOSIS One population of workers exposed to histoplasmosis was a group of camp counselors. In June 2012 in Nebraska, there was an outbreak of respiratory illness among a group of 32 camp counselors. One of the counselors had a confirmed laboratory diagnosis of histoplasmosis. 59% of the 32 counselors had symptoms that fit the case definition of the infection, and 31% received medical care for their symptoms. Some of the young campers also contracted the illness. Of the 153 children who allowed a laboratory sample or filled out a questionnaire, five had confirmed cases of the infection and twelve more were suspected. Environmental assessment of the area demonstrated that children assigned to a campsite with guano had 2.4 times the odds of infection as children whose campsite was over 21 yards away from the droppings (MMWR, 2012). This outbreak demonstrated how even recreational activities can cause exposure to the infection. Although many small studies about this infection exist, there is not much data available on national morbidity and mortality rates. One reason for this is that the disease itself often difficult to detect because in most people it doesn’t produce symptoms. Another issue with acquiring data on this topic is that the illness is only reportable in a handful of states, and no national surveillance system exists (CDC, 2012). Instituting a national reporting system would be prudent because then researchers could see where a majority of the cases are coming from. As the population ages, more elderly people with weaker immune systems are likely to be infected. Also, further epidemiological research into the duboisii variety would be interesting, since this is so rare and is not usually seen in conjunction with HIV. 9 THE EPIDEMIOLOGY OF HISTOPLASMOSIS Since people with HIV are achieving longer life spans, data on opportunistic infections may prove beneficial in knowing how to prevent and treat the illness. 10 THE EPIDEMIOLOGY OF HISTOPLASMOSIS Figure 1 Cumulative incidences of cases of histoplasmosis (HISTO), blastomycosis (BLASTO), and coccidioidomycosis (COCCI) requiring hospitalization in the United States, 2002. Data are the estimated number of hospitalized patients per 1 million US persons (Chu, Feudtner, Heydon, Walsh, & Zaoutis, 2006). Figure 2 Geographic distribution of histoplasmosis in persons >65 years of age, United States, 1999–2008. Values are no. cases/100,000 person-years (Baddley et al., 2011). 11 THE EPIDEMIOLOGY OF HISTOPLASMOSIS Table 1 Demographic and clinical features of hospitalized children and adults with endemic mycoses in the United States during 2002 (Chu, Feudtner, Heydon, Walsh, & Zaoutis, 2006). 12 THE EPIDEMIOLOGY OF HISTOPLASMOSIS References Baddley, J.W., Winthrop, K.L., Patkar, N.M., Delzell, E., Beukelman, T., Xie, Fenglong, X.., . . . Curtis, J. R. (2011). Geographic distribution of endemic fungal infections among older persons, United States. Emerging Infectious Diseases 17(9). DOI: 10.3201/eid1709.101987 Centers for Disease Control and Prevention. (2012). Histoplasmosis. Retrieved from http://www.cdc.gov/fungal/histoplasmosis/ Chu, J.H., Feudtner, C., Heydon, K., Walsh, T.J., & Zaoutis, T.E. (2006). Hospitalizations for endemic mycoses: A population-based national study. Clinical Infectious Diseases. 42(6): 822-825. Retrieved from http://cid.oxfordjournals.org/content/42/6/822.full Fayyaz, Jazeela. (2013). Histoplasmosis. Medscape. Retrieved from http://emedicine.medscape.com/article/299054-overview Lenhart, S., Schafer, M., Singal, M., & Hajjeh, R. (1997). Histoplasmosis: protecting workers at risk. United States Department of Health and Human Services Public Health Service. Loulergue, P., Bastides, F., Baudouin, V., Chandenier, J., Mariani-Kurkdjian, P., Dupont, B., . . . Lortholary, O. (2007). Literature review and case histories of Histoplasma capsulatum var. duboisii infections in HIV-infected patients. Emerging Infectious Diseases 13(11). Retrieved from http://wwwnc.cdc.gov/eid/article/13/11/07-0665_article.htm Luo, G., Gerrety, M., DeBurger, B., Pfeffer, J., McMasters, R., & Mortensen, J. (2012). 13 THE EPIDEMIOLOGY OF HISTOPLASMOSIS Case twenty two: a disseminated infection. Journal Of Continuing Education Topics & Issues, 14(1), 22-25. Norman, F., Martín-Dávila, P., Fortún, J., Dronda, F., Quereda, C., Sánchez-Sousa, A., & López-Vélez, R. (2009). Imported histoplasmosis: two distinct profiles in travelers and immigrants. Journal Of Travel Medicine, 16(4), 258-262. doi:10.1111/j.1708-8305.2009.00311.x Notes from the field: histoplasmosis outbreak among day cAMP attendees - nebraska, june 2012. (2012). MMWR: Morbidity & Mortality Weekly Report, 61747-748. Weinberg, M., Weeks, J., Lance-Parker, S., Traeger, M. Wiersma, S., Phan, Q.N., . . . Hajjeh, R. (2003). Severe histoplasmosis in travelers to Nicaragua. Emerging Infectious Diseases 9(10). Retrieved from http://wwwnc.cdc.gov/eid/article/9/10/03-0049_article.htm 14