Epidemiology and Molecular Typing of Trypanosoma cruzi in Naturally-Infected Hound Dogs and Associated Triatomine Vectors in Texas, USA

Abstract

BackgroundTrypanosoma cruzi is the etiologic agent of Chagas disease throughout the Americas. Few population-level studies have examined the epidemiology of canine infection and strain types of T. cruzi that infect canines in the USA. We conducted a cross-sectional study of T. cruzi infection in working hound dogs in south central Texas, including analysis of triatomine vectors collected within kennel environments.Methodology/Principle FindingsPaired IFA and Chagas Stat-Pak serological testing showed an overall seroprevalence of 57.6% (n = 85), with significant variation across kennels. Dog age had a marginally significant effect on seropositivity, with one year of age increase associated with a 19.6% increase in odds of being seropositive (odds ratio 95% CI 0.996–1.435; p = 0.055). PCR analyses of blood revealed 17.4% of dogs harbored parasite DNA in their blood, including both seronegative and seropositive dogs. Molecular screening of organs from opportunistically sampled seropositive dogs revealed parasite DNA in heart, uterus, and mammary tissues. Strain-typing showed parasite discrete typing units (DTU) TcI and TcIV present in dog samples, including a co-occurrence of both DTUs in two individual dogs. Bloodmeal analysis of Triatoma gerstaeckeri and Triatoma sanguisuga insects collected from the kennels revealed exclusively dog DNA. Vector infection with T. cruzi was 80.6% (n = 36), in which T. gerstaeckeri disproportionately harbored TcI (p = 0.045) and T. sanguisuga disproportionately harbored TcIV (p = 0.029). Tracing infection status across dog litters showed some seropositive offspring of seronegative dams, suggesting infection of pups from local triatomine vectors rather than congenital transmission.Conclusions/SignificanceCanine kennels are high-risk environments for T. cruzi transmission, in which dogs likely serve as the predominant parasite reservoir. Disease and death of working dogs from Chagas disease is associated with unmeasured yet undoubtedly significant financial consequences because working dogs are highly trained and highly valued.

Distribution of triatomine species in domestic and peridomestic environments in central coastal Ecuador

“…Given that dogs and cats have been reported as important reservoirs hosts and sentinels for T . cruzi along the continent [28,29,30], more studies are required to understand their involvement in T . cruzi transmission in Ecuador.…”

Risk factors and select cardiac characteristics in dogs naturally infected withTrypanosoma cruzipresenting to a teaching hospital in 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. 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).…”

“…2,5 The seroprevalence of T. cruzi in dogs is particularly high in the state of Texas, with seroprevalence estimates of 6%-13% in shelter dogs across the state, 6%-18% in government working dogs along the Texas-Mexico border, and seroprevalence exceeding 50% in some multi-dog kennel environments with triatomine infestations. [6][7][8] Seropositive dogs occur in Louisiana, Oklahoma, Tennessee, Georgia, and Virginia. [9][10][11][12][13][14][15] Clinical presentation of Chagas heart disease varies widely depending on the extent of myocardial damage that results in a combination of arrhythmias, conduction abnormalities, heart enlargement, and heart failure.…”

Selected cardiac abnormalities in Trypanosoma cruzi serologically positive, discordant, and negative working dogs along the Texas-Mexico border

“…All dogs were tested for amplification of parasite DNA from buffy coat of blood by real-time PCR as previously described [70,71]; in the case of a positive rt-PCR reaction, additional rt-PCR was carried out to assign the parasite discrete typing unit [72]. All deviations from protocols are previously described [14,73].…”