High Trypanosoma cruzi infection prevalence associated with minimal cardiac pathology among wild carnivores in central Texas

Abstract

Infection with the zoonotic vector-borne protozoal parasite Trypanosoma cruzi causes Chagas disease in humans and dogs throughout the Americas. Despite the recognized importance of various wildlife species for perpetuating Trypanosoma cruzi in nature, relatively little is known about the development of cardiac disease in infected wildlife. Using a cross-sectional study design, we collected cardiac tissue and blood from hunter-donated wildlife carcasses- including raccoon (Procyon lotor), coyote (Canis latrans), gray fox (Urocyon cinereoargenteus), and bobcat (Lynx rufus) - from central Texas, a region with established populations of infected triatomine vectors and increasing diagnoses of Chagas disease in domestic dogs. Based on PCR analysis, we found that 2 bobcats (14.3%), 12 coyotes (14.3%), 8 foxes (13.8%), and 49 raccoons (70.0%) were positive for T. cruzi in at least one sample (right ventricle, apex, and/or blood clot). Although a histologic survey of right ventricles showed that 21.1% of 19 PCR-positive hearts were characterized by mild lymphoplasmocytic infiltration, no other lesions and no amastigotes were observed in any histologic section. DNA sequencing of the TcSC5D gene revealed that raccoons were infected with T. cruzi strain TcIV, and a single racoon harbored a TcI/TcIV mixed infection. Relative to other wildlife species tested here, our data suggest that raccoons may be important reservoirs of TcIV in Texas and a source of infection for indigenous triatomine bugs. The overall high level of infection in this wildlife community likely reflects high levels of vector contact, including ingestion of bugs. Although the relationship between the sylvatic cycle of T. cruzi transmission and human disease risk in the United States has yet to be defined, our data suggest that hunters and wildlife professionals should take precautions to avoid direct contact with potentially infected wildlife tissues.

Keywords: Canis latrans; Lynx rufus; Procyon lotor; Trypanosoma cruzi; Urocyon cinereoargenteus; Zoonotic.

Graphical abstract

Fig. 1

Spatial occurrence and distribution of T. cruzi infected, hunter-harvested wildlife, 2014. Number of infected over total number of that species tested are shown by county.

Fig. 2

Tissue-specific PCR results of T. cruzi testing. For each species, the outer 2 × 2 table cell values represent the number of animals with all possibilities of results based on analysis of right ventricle and apex. The nested cell data include the T. cruzi infection status of blood clots (number positive/number tested) stratified by the infection status of the RV and apex. Not all animals had matched samples from each apex, right ventricle, and clot.