A leading source for news and analysis about Mexico and the U.S.-Mexican border.
By David Gaddis Smith
An editorial in Public Library of Science Neglected Tropical Diseases is calling Chagas disease, a poverty-related chronic illness it says is responsible for an estimated 14,000 deaths in Latin America annually, ''The New HIV/AIDS of the Americas.'' There were an estimated 67,000 annual AIDS-related deaths in Latin America in 2010, and about 1.5 million infected with HIV/AIDS.
It is estimated that 8 million to 10 million people suffer from Chagas disease, and that from 300,000 to 1 million in the United States have it, many of them in Texas and along the Gulf Coast. Almost all of the U.S. cases are of people who contracted the disease elsewhere. The countries most affected are Bolivia, Mexico, Colombia and those in Central America, according to the editorial. Chagas, if not treated, can severely damage the heart, digestive and nervous systems. "Chagas heart disease is the leading cause of infectious myocarditis worldwide," according to one PLOS report.
The editorial recommends that greater action be taken to prevent the transmission of the disease that can occur through blood transfusions and in utero, for the development of greater vector control, and for greater availability of drugs and the development of better drug therapies. The editorial was written by tropical disease experts at the Baylor College of Medicine and other institutions.
Infection / Transmission
The disease was long generally transmitted via bites from the blood-sucking assassin bug in rural areas, and also is transmitted through blood transfusions, organ transplants, in utero (often from mothers who do not know they are infected) and through contact with infected insects' feces. The way insects from the Triatominae subfamily generally transmitted the Trypanosoma cruzi protozoan parasite is by biting a host, and then defecating. When the person scratches the bite, the protozoan can wind up entering the bloodstream through the wound or through the scratcher's eyes or mouth. The bugs generally have infected people in poor, rural, substandard homes often made of mud, adobe, straw or having thatched roofs, where it is easy for the bugs to hide. South American governments have had successful campaigns to eliminate the bugs from homes to the point that "oral transmission by ingestion of food contaminated by feces from infected insects" is now considered to be "the principal method of current transmission," according to a May 15 PLOS Neglected Tropical Diseases article entitled "Lower Richness of Small Wild Mammal Species and Chagas Disease Risk." Luckily for U.S. residents, according to a Scientific American article, the assassin bug species in the southwestern United States tend to defecate after leaving the body of those they feed on, and the chance of infection is extremely low. Only seven cases of bug to human infection have been reported in the United States, according to the April 2012 Emerging Infectious Diseases.
CDC story on the assassin bug and Chagas' disease.
AIDS/HIV Chagas disease similarities
The PLOS Neglected Tropical Diseases editorial found the following similarities between people living with Chagas disease and people living with HIV/AIDS:
• "Chagas disease has emerged as an important blood transfusion–related risk throughout the Americas just as HIV/AIDS did in the early 1980s, prior to the implementation of widespread blood screening and testing."
• Mother-to-child transmission leading to congenital Chagas disease and other adverse neonatal outcomes is increasingly recognized, with the Pan American Health Organization estimating more than 14,000 congenital cases in Latin America and "2,000 newborns infected annually in North America."
• Infection is often not readily apparent for a long time unless one if tested for it. In the case of Chagas disease, it can be years, even decades, before people realize they have been infected. Chagas is sometimes called the silent killer.
• There are roughly 2 million to 5 million individuals with or who are likely to develop Chagasic cardiomyopathy; that compares with 1.6 million people living with HIV/AIDS in the Latin America region.
• Both are chronic conditions requiring prolonged treatment courses: "a lifetime of antiretroviral therapy for HIV/AIDS patients, and one to three months of therapy for those with Chagas disease." The Chagas therapy lags behind the success of the HIV/AIDS antiretroviral therapy.
• "For both diseases the treatment is expensive—in the case of Chagas disease, the expected cost of treatment per patient year is $1,028, with lifetime costs averaging $11,619 per patient."
• "As with patients in the first two decades of the HIV/AIDS epidemic, most patients with Chagas disease do not have access to health care."
• Both Chagas disease and HIV/AIDS disproportionately affect people living in poverty.
Latin American government and regional action have made great strides, but more work is needed
|Chagas-related deaths per year||45,000 (WHO)||11,000 (2008 - WHO)
14,000 (currently in the Americas - PLOS)
|Chagas infections||30 million (WHO)||8 million (2006 - WHO)
8 million-10 million (currently in the Americas - PLOS)
|Annual incidence of Chagas||700,000 (WHO)||56,000 (2006 - WHO)|
Latin American governments and regional organizations have made great strides to curtail Chagas disease, but much more remains to be done, such as making more medicine available, improving that medicine and developing an efficient vaccine. The WHO estimates that annual deaths decreased from 45,000 in 1990 to around 11,000 in 2008, although the PLOS editorial put the current number at an estimated 10 million. Brazil's vector control "reduced the incidence of new cases from 100,000 in 1980 to less than 500 notified cases per year from 2001 to 2006," according to the June 2010 article, "The Centennial of the Discovery of Chagas Disease: Facing the Current Challenges." The insects transmitting the disease have been observed to be developing some pesticide resistance, however.
The editorial recommended a comprehensive strategy for:
• Control and elimination efforts, including expanding vector control strategies and developing new control tools.
• Blood screening and point-of-care testing.
• Maternal and child interventions.
• Overcoming the current lack of available drugs for treatment.
• Health education.
• Parallel research and development.
Alejandro Cruz-Reyes and José Miguel Pickering-López, in the 2006 article "Chagas disease in Mexico: an analysis of geographical distribution during the past 76 years - A Review," say the Mexican government did not officially recognize the disease until 2001. The authors say that Mexico's delay in recognizing the threat, despite reams of literature about the disease's presence in the country, allowed "the disease to reach endemic proportions in some areas, to be spread to new geographic environments, and even to move into new environmental niches because of dissemination via blood transfusion." It reported the states having the most cases as Jalisco, Oaxaca, Veracruz, Guerrero, Chiapas and Morelos. Most of these states are in southern Mexico. Since 2003, the government has been more aggressively combatting the disease estimated to affect 2 million or more Mexicans, and Guanajuato state has developed a strong program to fight the disease.
The May 15 PLOS Neglected Tropical Diseases article says dogs have become important hosts for the disease in a number of countries, including Mexico, the United States, Panama, Argentina and Venezuela. While dogs have not been found to be an important reservoir of the disease in Brazil, the article did find that in communities in wild Brazilian environments, there was a high prevalence of seropositive dogs.
Blood transfusion, organ transplantation infection: Donated blood often is not tested for Chagas
A World Health Organization report, "Chagas disease: control and elimination," (PDF) says: "Contamination rates in blood banks in some cities of the American continent vary from 3% to up to as much as 53%, indicating that the prevalence of T. cruzi-contaminated blood may exceed the prevalence of HIV and hepatitis B and C viruses in blood stocks."
The Oct. 5, 2010 PLOS article "Chagas Disease Risk in Texas" says the disease is endemic there and lamented: "Yet, Chagas disease is not reportable in Texas, blood donor screening is not mandatory, and the serological profiles of human and canine populations remain unknown." It also recommended "that a joint initiative be undertaken by the United States and Mexico to combat Chagas disease in the trans–border region."
The PLOS article said arguments against mandatory blood testing are cost and "the potential for false positive units to be removed from the blood supply." The article said an FDA simulation model in 2009 predicted there would be about 44 cases of transmission–induced Chagas disease in the United States each year with no testing; "With 65% testing, that reduces to about 15 cases." An April 2011 article, "Chagas Disease Has Now Gone Global," says screening has found 1,300 cases of Chagas disease in blood donors.
The WHO says " Increasing evidence shows that treating patients during the acute and early chronic phase could avoid mortality and reduce the severity of symptoms." In Mexico, the Slim Initiative for developing tropical disease vaccines "is focusing its initial efforts on developing a therapeutic vaccine for Chagas disease," according to a PLOS March 12 editorial entitled "Texas and Mexico: Sharing a Legacy of Poverty and Neglected Tropical Diseases."
The May PLOS editorial says a "recent analysis indicates that many patients do not have access to the essential medicines for Chagas disease, in particular, the first line of therapy, the drug benznidazole." It said Doctors Without Borders said highly endemic countries such as Paraguay and Bolivia "face acute shortages of benznidazole, forcing thousands of newly diagnosed patients to postpone treatment." The editorial warns of a "a looming shortage of benznidazole, as well as the over-reliance on a single drug manufacturer." It said Nifurtimox, which also treats Chagas disease, should be made available in Latin America.
The editorial says "the treatment has proven efficacy only for the acute stages of the infection or in children up to 12 years of age during the early chronic phase of the infection." Baylor's Peter J. Hotez, the lead author of the editorial, told the BBC that neither of the drugs "works very well once you've developed the heart manifestations ... and they're also terribly toxic as well, and many times people have to abandon treatment because they can't tolerate it." Hotez, the founding dean of the National School of Tropical Medicine, said the drugs are too toxic to be used for pregnant women. He told the BBC that he particularly compares Chagas disease to AIDS in the early years "when we didn't have effective drugs" and because the numbers of those affected by both diseases are huge. He said Baylor is trying to develop a prototype vaccine for the disease.
|Place||Parasite incidence rate in vectors (bugs)||Cases contracted in area where reported||Estimated human infections||Counties infected vector found in|
|Texas||>50%||4||up to 267,000||82 of 254|
|California (insects gathered at Escondido)||T. cruzi found in 3 of 7 bugs||19||-||-|
|Mexico||-||-||2 million or more||-|
|United States||-||-||300,000 to 1 million||-|
|The Americas||8 million to 10 million|
The disease was discovered by Dr. Carlos Chagas, a Brazilian, in 1909. The WHO says: "In 2005, Chagas disease was incorporated into WHO's classification of neglected tropical diseases in order to promote synergistic advocacy and control efforts with other similarly neglected diseases." It is suspected that Charles Darwin contracted the disease during his journey to South America.