Chagas Disease in Texas

BACKGROUND: Chagas disease has been diagnosed in Texas for decades and is considered enzootic in canines. Although most human cases have been associated with living in or traveling to endemic countries, autochthonous transmission in Texas has been sporadically reported. Human and animal cases of Chagas disease became reportable conditions in Texas on January 1, 2013. Seven of the 11 species of vector bugs found in the US are found in Texas. All are involved in the enzootic cycle of the protozoan parasite Trypanosoma cruzi, the causative agent for Chagas disease.

METHODS: Texas Department of State Health Services (TDSHS) surveillance data from 2013 and 2014 were analyzed to determine case demographics, temporal/spatial distribution of cases, and distribution and percent positive of bugs carrying T. cruzi. Peer-reviewed articles were reviewed to assess their utility in gauging the risk of T. cruzi transmission in Texas by considering prevalence of parasites in vectors; vector distribution, habitat, and behavior; serosurvey results; and risk factors that predispose humans and animals to infection.

RESULTS: TDSHS data shows 12 autochthonous human cases and 351 animal cases during 2013 and 2014. Research supports the occurrence of unrecognized and consequently unreported autochthonous cases.

Approximately half of the Triatominae bugs submitted to the TDSHS test positive for the presence of T. cruzi. Blood meal analysis of bugs collected in peridomestic ecotopes reveals feeding behavior involving a wide range of hosts, including humans.

Data from two years of mandatory reporting of animal Chagas disease cases shows cases occurring in areas where studies have documented the presence of parasite-carrying bugs. No association between human and animal cases was demonstrated.

Studies have demonstrated that there is a profound lack of knowledge of Chagas disease in the medical community which contributes to lost opportunities for appropriate diagnosis, treatment, and reporting.

CONCLUSIONS: Texas possesses all the elements required to maintain local transmission of T. cruzi: parasite, vector, reservoir, and a susceptible host population. Autochthonous transmission has been verified. The disease risk and current disease burden in Texas from Chagas disease are not adequately characterized. The gap in Chagas disease awareness has prompted federal grant opportunities to develop tools and practices to improve knowledge in the medical community and other segments of the population.  

Mandatory reporting of animal Chagas disease cases has not contributed additional knowledge or insight for public health intervention and will be discontinued by TDSHS effective January 1, 2016.