Trypanosoma cruzi (Agent of Chagas Disease) in Sympatric Human and Dog Populations in “Colonias” of the Lower Rio Grande Valley of Texas

Abstract

The zoonotic, vector-borne parasite Trypanosoma cruzi causes Chagas disease throughout the Americas, but human and veterinary health burdens in the United States are unknown. We conducted a cross-sectional prevalence study in indigent, medically underserved human and cohabiting canine populations of seven south Texas border communities, known as colonias. Defining positivity as those samples that were positive on two or more independent tests, we found 1.3% seroprevalence in 233 humans, including one child born in the United States with only short-duration travel to Mexico. Additionally, a single child with no travel outside south Texas was positive on only a single test. Among 209 dogs, seroprevalence was 19.6%, but adjusted to 31.6% when including those dogs positive on only one test and extrapolating potential false negatives. Parasite DNA was detected in five dogs, indicating potential parasitemia. Seropositive dogs lived in all sampled colonias with no difference in odds of positivity across age, sex, or breed. Colonia residents collected two adult Triatoma gerstaeckeri and one nymph triatomine from around their homes; one of three bugs was infected with T. cruzi, and blood meal hosts were molecularly determined to include dog, human, and raccoon. Dogs and the infected vector all harbored T. cruzi discrete typing unit I, which has previously been implicated in human disease in the United States. Colonias harbor active T. cruzi transmission cycles and should be a priority in outreach and vector control initiatives.

Repeated cross‐sectional study of Trypanosoma cruzi in shelter dogs in Texas, in the context of Dirofilaria immitis and tick‐borne pathogen prevalence

“…The T. cruzi seroprevalence we report (18.1%) is on the high end of prevalence estimates reported in previous serosurveys of dogs from Texas, Louisiana, and Oklahoma, which ranged from 3.6% to 22% . Our other more targeted studies of Texas canine populations have revealed 57.6% seroprevalence (n = 85) in working dogs housed in outdoor kennels, 19.6% in dogs in underserved communities in south Texas (n = 209), and 7.4%‐18.9% in government working dogs along the Texas‐Mexico border . The T. cruzi seroprevalence obtained in our study (18.1%) is more than twice the estimated seroprevalence (8.8%, n = 205) we previously reported from initial spring sampling at these shelters, owing to revised test interpretation criteria and the availability of the additional serologic test (CDP) used in the current study.…”

Risk factors and select cardiac characteristics in dogs naturally infected with Trypanosoma cruzi presenting to a teaching hospital in Texas

“…Similarly, working hound dogs in south central Texas have a seroprevalence of 57.6% (n = 85) . Finally, dogs in the Lower Rio Grande Valley have a seroprevalence of 19.6% (n = 209) . This information suggests that all regions of Texas and surrounding states should be involved in future efforts for increasing veterinary and public awareness for Chagas disease.…”

“…Trypanosoma cruzi ‐positive dogs were reported from all 10 ecoregions present in Texas, demonstrating that T. cruzi is widespread across Texas. Occurrence of T. cruzi infection in dogs in Texas is well documented in the United States, and Texas could be a hotspot for infection with 7 triatomines capable of transmission, the highest nationwide . The high prevalence of dogs infected with T. cruzi likely demonstrates an established enzootic transmission cycle, as Texas harbors the highest species diversity of triatomine vectors that can transmit T. cruzi and a diversity of wildlife reservoirs .…”

“…Occurrence of T. cruzi infection in dogs in Texas is well documented in the United States, and Texas could be a hotspot for infection with 7 triatomines capable of transmission, the highest nationwide. 2,7,8,36,37,[42][43][44][45][46] The high prevalence of dogs infected with T. cruzi likely demonstrates an established enzootic transmission cycle, as Texas harbors the highest species diversity of triatomine vectors that can transmit T. cruzi and a diversity of wildlife reservoirs. 2,5,47 The South Texas Plains ecoregion had the highest percent of infected dogs (47%), whereas the next highest region was the Edwards Plateau (32%).…”

“…Furthermore, there is a high T. cruzi infection rate in dogs from south central Texas which includes the border with Mexico (this is the south Texas Plains ecoregion). 7,8,36,43 In a population of dogs with T. cruzi testing from 1993 to 2007, more than 60% of the cases came from central and southern Texas. 36 Similarly, working hound dogs in south central Texas have a seroprevalence of 57.6% (n = 85).…”