Chagas Surveillance Rare Among US States, CDC Report Finds

Carolyne Bennett, MPH

Only a handful of US states actively surveil Chagas disease, but a new report from the US Centers for Disease Control and Prevention (CDC) says better monitoring of the potentially life-threatening infection could help public health officials gain a clearer picture of its impact and lessen the risk of complications in individual patients.

Chagas disease is caused by a protozoan parasite Trypanosoma cruzi. It can be spread via vector insects, congenitally, or by blood or organ donation, although the latter is considered rare. In the acute phase, patients often are asymptomatic or have flu-like symptoms. Infants face a higher risk of life-threatening complications during this phase. If untreated, the disease becomes chronic, at which point some patients remain asymptomatic, but others—roughly 20% to 30%—develop potentially life-threatening cardiac or gastrointestinal complications.

Although the disease can be serious, its impact is hard to quantify because of a general lack of awareness of the disease among health care professionals, and a lack of screening in the United States, the CDC said in its July 6 Morbidity and Mortality Weekly Report. The report argues more state-level surveillance could aid in the tracking of the disease.

“If resources are available, surveillance for Chagas disease might be important to conduct in states with large populations at risk, including frequent travelers from countries where the disease is endemic and states at risk for local autochthonous transmission (eg, have infected mammalian reservoirs and appropriate triatomine vectors), to delineate the actual prevalence of disease,” wrote the study’s authors, led by Carolyne Bennett, MPH, of the CDC’s Center for Global Health.

The CDC estimates that there are about 300,000 cases of Chagas disease in the United States, and most of those infections were acquired outside of the country, from areas where the disease is endemic. Roughly 8 million individuals have Chagas in Mexico, Central America, and South America.

That’s likely why, of the 6 states where Chagas disease is reportable to state health agencies, 4 of them are states that border either Mexico or the Gulf of Mexico: Arizona, Louisiana, Mississippi, and Texas. The other 2 states that monitor Chagas are Arkansas and Tennessee. Massachusetts previously tracked the disease, but the state discontinued surveillance in 2014.

Arizona, Louisiana, Mississippi, and Texas focus on autochthonous local transmission in their reporting and data collection.

"Most people with Chagas disease in the United States acquired the disease in Latin America, where the disease is endemic,” Bennett told Contagion^®. “States that focus on collecting data on all routes of transmissions are able to assess the total disease burden. With a focus on autochthonous transmission, public health officials are able to respond by investigating to prevent further transmission.”

The other 2 states—Arkansas and Tennessee—track all modes of transmission.

“In Arkansas, the health department disseminates Chagas disease health alerts to physicians, particularly obstetricians/gynecologists who care for pregnant women at risk,” the authors noted. “However, no state conducts surveillance specifically for congenital infections.”

The CDC estimates that between 65 and 315 congenital T cruzi infections occur each year in the United States. Bennett and colleagues wrote that more focused surveillance efforts might improve identification of congenital Chagas cases.

“Timely recognition of infection and treatment will prevent disease development in infected infants and reduce the risk for further transmission,” Bennett and colleagues wrote. “However, surveillance for congenital Chagas disease is challenging in the absence of routine prenatal or newborn screening.”

Regarding the relatively rare category of transmission via blood or organ donation, the authors noted that 2300 infected blood donors have been identified since blood banks started screening for Chagas in 2007. Such data isn’t a reliable indicator of the overall prevalence of Chagas; however, since rates of blood donation are relatively low against foreign-born Latinos, a group statistically more likely to be infected.

The authors determined that surveillance efforts are not only helpful for tracking Chagas, but also for raising awareness among health care professionals and the public. They encouraged states to evaluate their risk and consider beginning surveillance if the state’s risk profile warrants it.

“Even though Chagas disease surveillance can help increase awareness among public health officials and physicians, and prevent disease complications in patients, not every state has the need or the resources to implement surveillance,” Bennett said.