An Expert Interview With Caryn Bern, MD, MPH
An Expert Interview With Caryn Bern, MD, MPH
Editor's Note:
According to the Division of Parasitic Diseases at the US Centers for Disease Control and Prevention (CDC), as many as 8-11 million people in Mexico, Central America, and South America have Chagas disease. The impact is not limited to the rural areas in Latin America in which vector-borne transmission occurs; population movements from rural to urban areas of Latin America and to other regions of the world have increased the geographic distribution and changed the epidemiology of Chagas disease.
Kelly Stimpert, MPH, interviewed Caryn Bern, MD, MPH, Medical Epidemiologist at the US Centers for Disease Control and Prevention in Atlanta, Georgia, about the changing epidemiology, diagnosis, treatment, and management of Chagas disease.
Ms. Stimpert: Why is Chagas disease considered a newly recognized infectious disease in the United States?
Dr. Bern: Although Chagas disease was discovered in 1909 and as many as 11 million people worldwide are infected, until recently there has been little awareness of the disease in the United States. Chagas disease has been primarily a concern in Mexico, Central America, and South America. However, due to rising trends in immigration of Latin Americans, the CDC estimates that at least 100,000 persons living in the United States are infected. The CDC refers to Chagas disease as newly "recognized" as opposed to newly "emerging" because the disease itself was not recently discovered; however, the recognition of its increasing prevalence in the United States is a more recent phenomenon.
Ms. Stimpert: What is Chagas disease, and how is it transmitted?
Dr. Bern: Chagas disease is caused by the parasite Trypanosoma cruzi and is spread by infected bugs called triatomines, or "kissing bugs." A person usually becomes infected after the bug (also referred to as the vector) feeds and defecates; the parasite is found in the feces of infected triatomines. Parasite inoculation typically occurs when the feces are rubbed into the bite wound or a mucous membrane. Chagas disease can also be transmitted by blood transfusion, organ transplantation, and congenitally. Rarely, transmission has occurred by ingesting contaminated food or drink and by laboratory accidents.
Ms. Stimpert: Is there transmission in the United States?
Dr. Bern: Yes. To date investigators have documented 6 cases of US vector-borne infections, 7 transfusion-associated cases, and 5 organ transplant-associated cases. Additional infections by these routes have likely occurred but have gone unrecognized. The transfusion and transplant cases represent totals reported from both the United States and Canada. Screening the US blood supply for Chagas disease was instituted in early 2007, after US Food and Drug Administration (FDA) approval of a blood donation screening test in late 2006. On the basis of data collected by the American Association of Blood Banks (AABB), an estimated 1 in every 27,500 blood donors test positive for Chagas disease. That rate is significantly higher in areas with large Hispanic populations, such as California, Florida, and Texas. During the first 18 months of screening, over 500 confirmed cases of T cruzi in blood donors were identified. All donors with positive results receive correspondence from the blood center. They are also advised that they may no longer donate blood and that they should see their physician.
Ms. Stimpert: What are the signs and symptoms of Chagas disease?
Dr. Bern: There are 2 distinct phases of the disease, acute and chronic. The acute phase typically lasts 4-8 weeks and can be asymptomatic or characterized by mild illness. The chronic phase can be divided into 2 forms: indeterminate and symptomatic. During the chronic phase, few or no parasites can be found in the blood. Most persons will remain in the indeterminate chronic phase for the duration of their lives. However, approximately 20% to 40% of chronically infected persons progress to symptomatic disease, developing cardiac and occasionally gastrointestinal manifestations. Cardiac disease usual begins with conduction abnormalities, such as right bundle-branch block and/or right anterior fascicular block. Years later, this may be followed by higher-grade heart blocks, ventricular arrhythmias, and/or dilated cardiomyopathy. Cardiomyopathy is sometimes accompanied by apical aneurysm and thrombus formation. Less commonly, gastrointestinal manifestations, including several megasyndromes, will be present.
Ms. Stimpert: Who should be tested for Chagas disease?
Dr. Bern: Indications for testing are based on patient risk for infection. A careful medical and social history will be important to identify potential Chagas risk. Have they lived in a Chagas-endemic country? In the country, did they live in poorly constructed housing made of thatched roofing or adobe bricks, particularly in a rural area? If the answers are yes, patients should then be questioned about familiarity with the bug. If they have seen the bug and/or have been previously bitten, testing is recommended. Has the patient received a blood transfusion or tissue or organ transplant? Is the patient's mother from a rural area of an endemic country? Any patient who has presented with cardiac or gastrointestinal manifestations, in addition to residence in an endemic country, should be tested.
Ms. Stimpert: How do physicians test for Chagas disease? What diagnostic tests are used?
Dr. Bern: Most patients will likely be in the chronic phase of disease. Serologic testing to identify antibody to T cruzi is the appropriate way to diagnose those infections. Serum samples can be sent to the CDC through the state health department. Diagnostic testing for Chagas disease is challenging; there is no gold standard test and all currently available tests have varying sensitivity and specificity. The best approach is to apply 2 or more tests, using different techniques, to increase confidence in a diagnosis of Chagas disease. Two commonly used techniques are enzyme-linked immunosorbent assay (ELISA) and immunofluorescent antibody (IFA) test.
Ms. Stimpert: What medications are used to treat Chagas disease? What do physicians need to know in order to properly treat the disease?
Dr. Bern: Two drugs, benznidazole and nifurtimox, are used to treat Chagas disease. They are considered the worldwide standard antiparasitic treatment for Chagas disease. In the United States, the drugs are not FDA-approved and are only available through the CDC, for use under investigational protocols for compassionate treatment. Specific treatment regimens vary depending on an individual's age, clinical status, preference, and overall health. Side effects are common in both medications, and may be more severe and frequent with increasing age.
A baseline evaluation of Chagas-positive patients should include a complete history, physical examination, and resting electrocardiogram (ECG) with a 30-second lead II rhythm strip. Persons infected with T cruzi should be counseled not to donate blood. Screening should be offered for family members with a similar exposure history and for children of infected women.
Ms. Stimpert: It appears that treatment options are complex and vary by patient and stage of disease. Where can physicians find treatment guidelines?
Dr. Bern: For specific diagnostic and treatment guidelines, physicians should refer to The Journal of the American Medical Association (JAMA) article: "Evaluation and Treatment of Chagas Disease in the United States: A Systematic Review." Physicians are also encouraged to visit the CDC's Chagas Website at www.cdc.gov/chagas or to call the Division of Parasitic Diseases at (770) 488-7775 for consultations.
Ms. Stimpert: Is there any other information about Chagas disease that you would like to share?
Dr. Bern: I would encourage physicians, especially those who treat a large number of Hispanic patients, to visit the CDC's Chagas disease Website for more information and to review the list of Chagas-endemic countries. Physicians may also download a photograph of the triatomine to use as a visual aid when questioning patients about their familiarity with the bug. It's also important to mention some of the challenges in recognizing and treating the disease. Many Chagas-positive persons living in the United States may have little or no access to healthcare, in addition to not speaking English. Because of these factors, the CDC is developing educational materials not only targeted to physicians, but also designed to reach Hispanic networks and community-based organizations. Material is available in both English and Spanish. The CDC is also in the process of developing patient fact sheets, designed at various literacy levels, and additional provider resources. Some of these are available now and others will be added.
Editor's Note:
According to the Division of Parasitic Diseases at the US Centers for Disease Control and Prevention (CDC), as many as 8-11 million people in Mexico, Central America, and South America have Chagas disease. The impact is not limited to the rural areas in Latin America in which vector-borne transmission occurs; population movements from rural to urban areas of Latin America and to other regions of the world have increased the geographic distribution and changed the epidemiology of Chagas disease.
Kelly Stimpert, MPH, interviewed Caryn Bern, MD, MPH, Medical Epidemiologist at the US Centers for Disease Control and Prevention in Atlanta, Georgia, about the changing epidemiology, diagnosis, treatment, and management of Chagas disease.
Ms. Stimpert: Why is Chagas disease considered a newly recognized infectious disease in the United States?
Dr. Bern: Although Chagas disease was discovered in 1909 and as many as 11 million people worldwide are infected, until recently there has been little awareness of the disease in the United States. Chagas disease has been primarily a concern in Mexico, Central America, and South America. However, due to rising trends in immigration of Latin Americans, the CDC estimates that at least 100,000 persons living in the United States are infected. The CDC refers to Chagas disease as newly "recognized" as opposed to newly "emerging" because the disease itself was not recently discovered; however, the recognition of its increasing prevalence in the United States is a more recent phenomenon.
Ms. Stimpert: What is Chagas disease, and how is it transmitted?
Dr. Bern: Chagas disease is caused by the parasite Trypanosoma cruzi and is spread by infected bugs called triatomines, or "kissing bugs." A person usually becomes infected after the bug (also referred to as the vector) feeds and defecates; the parasite is found in the feces of infected triatomines. Parasite inoculation typically occurs when the feces are rubbed into the bite wound or a mucous membrane. Chagas disease can also be transmitted by blood transfusion, organ transplantation, and congenitally. Rarely, transmission has occurred by ingesting contaminated food or drink and by laboratory accidents.
Ms. Stimpert: Is there transmission in the United States?
Dr. Bern: Yes. To date investigators have documented 6 cases of US vector-borne infections, 7 transfusion-associated cases, and 5 organ transplant-associated cases. Additional infections by these routes have likely occurred but have gone unrecognized. The transfusion and transplant cases represent totals reported from both the United States and Canada. Screening the US blood supply for Chagas disease was instituted in early 2007, after US Food and Drug Administration (FDA) approval of a blood donation screening test in late 2006. On the basis of data collected by the American Association of Blood Banks (AABB), an estimated 1 in every 27,500 blood donors test positive for Chagas disease. That rate is significantly higher in areas with large Hispanic populations, such as California, Florida, and Texas. During the first 18 months of screening, over 500 confirmed cases of T cruzi in blood donors were identified. All donors with positive results receive correspondence from the blood center. They are also advised that they may no longer donate blood and that they should see their physician.
Ms. Stimpert: What are the signs and symptoms of Chagas disease?
Dr. Bern: There are 2 distinct phases of the disease, acute and chronic. The acute phase typically lasts 4-8 weeks and can be asymptomatic or characterized by mild illness. The chronic phase can be divided into 2 forms: indeterminate and symptomatic. During the chronic phase, few or no parasites can be found in the blood. Most persons will remain in the indeterminate chronic phase for the duration of their lives. However, approximately 20% to 40% of chronically infected persons progress to symptomatic disease, developing cardiac and occasionally gastrointestinal manifestations. Cardiac disease usual begins with conduction abnormalities, such as right bundle-branch block and/or right anterior fascicular block. Years later, this may be followed by higher-grade heart blocks, ventricular arrhythmias, and/or dilated cardiomyopathy. Cardiomyopathy is sometimes accompanied by apical aneurysm and thrombus formation. Less commonly, gastrointestinal manifestations, including several megasyndromes, will be present.
Ms. Stimpert: Who should be tested for Chagas disease?
Dr. Bern: Indications for testing are based on patient risk for infection. A careful medical and social history will be important to identify potential Chagas risk. Have they lived in a Chagas-endemic country? In the country, did they live in poorly constructed housing made of thatched roofing or adobe bricks, particularly in a rural area? If the answers are yes, patients should then be questioned about familiarity with the bug. If they have seen the bug and/or have been previously bitten, testing is recommended. Has the patient received a blood transfusion or tissue or organ transplant? Is the patient's mother from a rural area of an endemic country? Any patient who has presented with cardiac or gastrointestinal manifestations, in addition to residence in an endemic country, should be tested.
Ms. Stimpert: How do physicians test for Chagas disease? What diagnostic tests are used?
Dr. Bern: Most patients will likely be in the chronic phase of disease. Serologic testing to identify antibody to T cruzi is the appropriate way to diagnose those infections. Serum samples can be sent to the CDC through the state health department. Diagnostic testing for Chagas disease is challenging; there is no gold standard test and all currently available tests have varying sensitivity and specificity. The best approach is to apply 2 or more tests, using different techniques, to increase confidence in a diagnosis of Chagas disease. Two commonly used techniques are enzyme-linked immunosorbent assay (ELISA) and immunofluorescent antibody (IFA) test.
Ms. Stimpert: What medications are used to treat Chagas disease? What do physicians need to know in order to properly treat the disease?
Dr. Bern: Two drugs, benznidazole and nifurtimox, are used to treat Chagas disease. They are considered the worldwide standard antiparasitic treatment for Chagas disease. In the United States, the drugs are not FDA-approved and are only available through the CDC, for use under investigational protocols for compassionate treatment. Specific treatment regimens vary depending on an individual's age, clinical status, preference, and overall health. Side effects are common in both medications, and may be more severe and frequent with increasing age.
A baseline evaluation of Chagas-positive patients should include a complete history, physical examination, and resting electrocardiogram (ECG) with a 30-second lead II rhythm strip. Persons infected with T cruzi should be counseled not to donate blood. Screening should be offered for family members with a similar exposure history and for children of infected women.
Ms. Stimpert: It appears that treatment options are complex and vary by patient and stage of disease. Where can physicians find treatment guidelines?
Dr. Bern: For specific diagnostic and treatment guidelines, physicians should refer to The Journal of the American Medical Association (JAMA) article: "Evaluation and Treatment of Chagas Disease in the United States: A Systematic Review." Physicians are also encouraged to visit the CDC's Chagas Website at www.cdc.gov/chagas or to call the Division of Parasitic Diseases at (770) 488-7775 for consultations.
Ms. Stimpert: Is there any other information about Chagas disease that you would like to share?
Dr. Bern: I would encourage physicians, especially those who treat a large number of Hispanic patients, to visit the CDC's Chagas disease Website for more information and to review the list of Chagas-endemic countries. Physicians may also download a photograph of the triatomine to use as a visual aid when questioning patients about their familiarity with the bug. It's also important to mention some of the challenges in recognizing and treating the disease. Many Chagas-positive persons living in the United States may have little or no access to healthcare, in addition to not speaking English. Because of these factors, the CDC is developing educational materials not only targeted to physicians, but also designed to reach Hispanic networks and community-based organizations. Material is available in both English and Spanish. The CDC is also in the process of developing patient fact sheets, designed at various literacy levels, and additional provider resources. Some of these are available now and others will be added.
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