Chagas Disease on our doorstep
By James A. Mobley, MD, MPH
In 2007, blood banks began testing donors for Chagas disease. If a donor tests positive for Chagas, that person is referred to a health care provider for further evaluation. Since Chagas is a disease primarily of Central and South America, Texas family physicians may have limited experience or knowledge of how to evaluate Chagas disease. The following true case illustrates a typical Chagas presentation.
When Marivell was 17, her older brother died in an automobile accident. She decided to donate blood at her local blood bank to honor his memory. A few weeks later she received a letter from her blood bank informing her that she had tested positive for Chagas disease. The letter provided information on Chagas disease and advised her to see her family doctor for further evaluation and confirmation of the diagnosis.
Chagas disease is a parasitic infection caused by Trypanosoma cruzi. It is spread through the feces of infected triatomines, also known as kissing bugs. When the kissing bug takes a blood meal, it defecates, potentially contaminating the wound with the Trypanosoma cruzi parasite. Kissing bugs are often found in poorly constructed and rural housing, typically living within mud walls and thatched roofs. They also may be found in brushy and forested environments emerging at night to feed. Chagas can also be transmitted by blood transfusion, organ transplantation, and congenitally. Chagas disease can also be spread by canines and other mammals orally. Oral spread can occur in animals that eat infected kissing bugs. Puppies in Texas have been found with kissing bugs in their mouths.
Chagas is endemic throughout much of Central and South America. It is estimated that as many as 6 million people in Mexico, Central America, and South America have Chagas disease. In Texas, Chagas has been found in skunks, raccoons, and opossums. Persons living in the United States who have migrated from endemic areas and U.S. residents who live in substandard housing are particularly vulnerable to the disease. Also, campers and other people who spend a lot of time in the outdoors may be at risk. It is estimated that there may be over 300,000 infected persons living in the United States, most of whom do not know they are infected. Pets, especially dogs, are also vulnerable to infection with T. cruzi.
Marivell was born in Corpus Christi and has lived in the same house in Sinton, Texas all her life. She has never left the United States. “It seems that it is not unusual that a Chagas-positive individual in the U.S. cannot definitely pinpoint the exact source of infection,” says Dr. Rachel Curtis-Robles of the Texas A&M College of Veterinary Medicine. Marivell was referred by her family doctor to an infectious disease specialist who confirmed the diagnosis of Chagas.
CHAGAS IN TEXAS
In Texas, 60 to 65 percent of the triatomine bugs have tested positive for T. cruzi. Chagas is considered an endemic disease in dogs. In Texas from 2013 to 2014, 351 animal cases of Chagas disease were reported, mostly in dogs. These cases occurred in all geographic regions of the state. Locally-acquired human cases are still uncommon. From 2013 to 2014, 39 human cases of Chagas disease were reported. Twenty-four were acquired in another country, 12 were locally-acquired, and the location of acquisition was unknown for three. It is likely that many more cases of Chagas go unreported than those that are reported.
Urban expansion has caused displacement of wildlife hosts in Texas resulting in a higher prevalence of domestic dogs as hosts. Thomas Cropper, DVM, has found Chagas in Air Force service dogs trained in San Antonio and kissing bugs have been found in the tents of Air Force trainees in the area. Of 33 kissing bugs collected at an Air Force training site in San Antonio, eight tested positive for human blood. Four out of eight tested positive for the Chagas parasite. In San Antonio, 66 percent of opossums, 32 percent of raccoons, and 26 percent of skunks tested positive for T. cruzi.
SYMPTOMS OF CHAGAS DISEASE
Chagas disease has an acute phase — lasting four to eight weeks — and a chronic phase. During the acute phase, most people have no symptoms while some may experience flu-like symptoms. There may be fever or swelling around the site of inoculation. Rarely, acute infection may result in cardiomyopathy, encephalopathy, or meningitis. Romaña’s sign, infected swelling of the eyelid, is a marker of acute Chagas disease. The swelling is due to bug feces being accidentally rubbed into the eye or the bite wound.
Following the acute phase, most infected people enter a chronic indeterminate asymptomatic state during which few or no parasites are found in the blood. Twenty to 30 percent of infected people will eventually develop symptoms. Symptoms include cardiomyopathy, cardiac arrhythmias, congestive heart failure, apical aneurysms with thrombus formation, and stroke. Also dilatation of portions of the gastrointestinal tract may occur, leading to bowel obstruction. Chagas has also been associated with megacolon and megaesophagus.
EVALUATION OF BLOOD DONORS WHO TEST POSITIVE FOR CHAGAS
A medical history, including possible exposures is key. The review of systems should focus on symptoms of chronic Chagas disease including palpitations, syncope, dizziness, congestive heart failure, symptoms compatible with thromboembolic phenomena, dysphagia, odynophagia, weight loss, and prolonged constipation. The evaluation should also include a physical examination and an electrocardiogram with a rhythm strip. Barium studies of the gastrointestinal tract may be considered.
CHAGAS DISEASE DIAGNOSIS
During the acute phase, the parasites may be found in blood smears by microscopic examination. Circulating parasite levels decrease rapidly within a few months and are undetectable during the chronic indeterminate phase. Diagnosis of chronic Chagas disease is made by serologic tests. Initial testing is done by commercial laboratories. If the test is positive, further testing will be done by the Texas Department of State Health Services and the Centers for Disease Control. Because a single test is not sufficiently sensitive or specific to make the diagnosis, a two-step protocol is used. The CDC uses an indirect fluorescent antibody test and an enzyme immuno assay. Consider the diagnosis of Chagas for unexplained heart failure or dysrhythmias especially in younger individuals and in unusual presentations of large and small bowel obstruction. If you suspect Chagas disease in a patient contact your local health department or the Texas Department of State Health Services Infectious Disease Control Unit for assistance.
CHAGAS DISEASE TREATMENT
Untreated Chagas infection is lifelong. There is no FDA approved treatment for Chagas disease. However two drugs, nifurtimox and benznidazole, are available for use under investigational protocols for compassionate treatment. They are available only through the CDC and there is no charge for these medications. The CDC recommends treatment for all people diagnosed with acute infection, congenital infection, or suppressed immune systems. All children with chronic infection should be treated and adults with chronic infection should be considered on a case-by-case basis. Side effects are common and more frequent and severe with increased age. They include peripheral neuropathy, anorexia, nausea, vomiting, headache, and weight loss. Contraindications to treatment include severe hepatic or renal disease. Questions regarding treatment should be directed to the Department of State Health Services or the CDC Parasitic Diseases Public Inquiries.
Marivell’s infectious disease doctor told her that the blood work showed she was in the ‘chronic’ phase. She was advised not to get pregnant and he treated her for six months. During her treatment, Marivell became nauseous, lost her appetite, vomited, and lost about 60 pounds. She did finish the course of the medication. Now 23, she is chronically tired, has little strength, and suffers from frequent body aches. She wonders if it will ever be safe for her to get pregnant and have a family.
For more Information on Chagas disease
Texas DSHS Infectious Disease Control Unit: Their Chagas Disease website is www.dshs.texas.gov/IDCU/disease/Chagas.doc. Contact them at (512) 776-7676 or by email at feedback.IDCU@dshs.state.tx.us.
The Centers for Disease Control and Prevention Chagas website is www.cdc.gov/parasites/chagas/. Questions regarding treatment should be directed to Parasitic Diseases Public Inquiries (404) 718-4745 or email firstname.lastname@example.org.
For more detailed information on evaluation and treatment, visit jamanetwork.com/journals/jama/fullarticle/209410 for free access to the article: Evaluation and Treatment of Chagas Disease in the United States: A Systematic Review (JAMA 2007: 298:2171-81)
For more assistance visit Kissing Bugs and Chagas Disease in the U.S. Texas A&M Agriculture and Life Sciences website kissingbug.tamu.edu/. They will help with analysis of triatomine bugs collected in Texas.
James A. Mobley, MD, MPH is a family physician practicing in Portland, Texas and a Fellow of the American Academy of Family Physicians. He is Health Authority for San Patricio County and the Medical Director for Texas A&M Healthy South Texas Initiative.
The opinions expressed in the article are those of the author and do not necessarily represent the views of the Texas Academy of Family Physicians, the San Patricio County Department of Public Health, or Texas A&M Healthy South Texas.
The author wishes to thank Kerry DuBose, RN; Rachel Curtis-Robles, PhD; Sarah Hamer, PhD, DVM; Thomas Cropper, DVM; and especially Marivell Garcia for their assistance in preparing this article.