Bionomics and Spatial Distribution of Triatomine Vectors of Trypanosoma cruzi in Texas and Other Southern States, USA

Abstract

Defining spatial and temporal occurrences of triatomine vectors of Trypanosoma cruzi, the agent of Chagas disease, in the US is critical for public health protection. Through a citizen science program and field collections from 2012 to 2016, we collected 3,215 triatomines, mainly from Texas. Using morphological and molecular approaches, we identified seven Triatoma species and report sex, length, and blood engorgement status. Many citizen-collected triatomines (92.9%) were encountered indoors, in peridomestic settings, or in dog kennels and represent spillover transmission risk of T. cruzi to humans and domestic animals. The most commonly collected species were Triatoma gerstaeckeri and Triatoma sanguisuga. Adult T. gerstaeckeri were collected from May to September, peaking from June to July, whereas adult T. sanguisuga were active later, from June to October, peaking from July to September. Based on cross correlation analyses, peaks of captures varied by species and across years. Point pattern analyses revealed unique occurrences of T. sanguisuga in north and east Texas, T. gerstaeckeri in south and west Texas, Triatoma indictiva and Triatoma lecticularia in central Texas, and Triatoma rubida in west Texas. These relatively unique spatial occurrences suggest associations with different suitable habitats and serve as a basis for future models evaluating the ecological niches of different vector species. Understanding the temporal and spatial heterogeneity of triatomines in the southern United States will improve targeted interventions of vector control and will guide public outreach and education to reduce human and animal contact with vectors and reduce the risk of exposure to T. cruzi.

Figure 1.

Phenology of collection of live triatomines of five species. Seasonal occurrence of five species of triatomines (and the total of those five species) collected alive by citizen scientists in Texas, 2012–2016. Of 39 specimens collected from November through March, 36 had locations specified, of which 27 (75.0%) were found indoors. In addition, four were found outdoors near animal quarters, including three in dog kennels and one in a chicken coop. This figure appears in color at www.ajtmh.org.

Figure 2.

Yearly phenology of collection of live triatomine species from Texas. Citizen scientists in Texas opportunistically collected live Triatoma gerstaeckeri and Triatoma sanguisuga, 2013–2016. This figure appears in color at www.ajtmh.org.

Figure 3.

Maps indicating areas of relatively unique distributions of five triatomine species in Texas. Higher than expected densities of Triatoma spp. are highlighted in red and lower than expected densities are highlighted in blue. This figure appears in color at www.ajtmh.org.