Understanding the ecological and epidemiological roles of pets in the transmission of SARS-CoV-2 is critical for animal and human health, identifying household reservoirs, and predicting the potential enzootic maintenance of the virus. We conducted a longitudinal household transmission study of 76 dogs and cats living with at least one SARS-CoV-2-infected human in Texas and found that 17 pets from 25.6% of 39 households met the national case definition for SARS-CoV-2 infections in animals. This includes three out of seventeen (17.6%) cats and one out of fifty-nine (1.7%) dogs that were positive by RT-PCR and sequencing, with the virus successfully isolated from the respiratory swabs of one cat and one dog. Whole-genome sequences of SARS-CoV-2 obtained from all four PCR-positive animals were unique variants grouping with genomes circulating among people with COVID-19 in Texas. Re-sampling showed persistence of viral RNA for at least 25 d-post initial test. Additionally, seven out of sixteen (43.8%) cats and seven out of fifty-nine (11.9%) dogs harbored SARS-CoV-2 neutralizing antibodies upon initial sampling, with relatively stable or increasing titers over the 2–3 months of follow-up and no evidence of seroreversion. The majority (82.4%) of infected pets were asymptomatic. ‘Reverse zoonotic’ transmission of SARS-CoV-2 from infected people to animals may occur more frequently than recognized.

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.

National parks attract millions of visitors each year. Park visitors, employees, and pets are at risk of infection with various zoonotic pathogens, including Trypanosoma cruzi, causative agent of Chagas disease. Big Bend National Park is located along the Texas-Mexico border in a region with endemic triatomine insects- vectors of T. cruzi- yet the degree to which the parasite is transmitted in this region is unknown. We collected triatomines for T. cruzi detection and discrete typing unit (DTU) determination, and conducted blood meal analyses to determine recent hosts. As an index of domestic/peridomestic transmission, we tested residential dogs in the Park for exposure to T. cruzi. From 2015 to 2017, 461 triatomines of three species-Triatoma rubida, Triatoma gerstaeckeri, and Triatoma protracta-were collected in and around the Park. Adult triatomine encounters peaked in June of each year (52.8% of collections). We detected an overall infection prevalence of 23.1% in adult triatomines (n = 320) and 4.2% in nymph triatomines (n = 24). DTU TcI was the only T. cruzi strain detected. Of 89 triatomines subjected to blood meal analyses, vertebrate host DNA was successfully amplified from 42 (47.2%); blood meal sources included humans, domestic animals, and avian and mammalian wildlife species. Tested dogs were considered positive if reactive on at least two independent serologic assays; we found 28.6% seroprevalence in 14 dogs. These findings reveal interactions between infected triatomines, humans, dogs, and wildlife in and around Big Bend National Park, with potential risk of human disease.

Of the documented tick-borne diseases infecting humans in México, Rocky Mountain spotted fever (RMSF), caused by the Gram-negative bacterium Rickettsia rickettsii, is responsible for most fatalities. Given recent evidence of brown dog tick, Rhipicephalus sanguineus s.l., as an emerging vector of human RMSF, we aimed to evaluate dogs and their ticks for rickettsiae infections as an initial step in assessing the establishment of this pathosystem in a poorly studied region of northeastern México while evaluating the use of dogs as sentinels for transmission/human disease risk. We sampled owned dogs living in six disadvantaged neighborhoods of Reynosa, northeastern México to collect whole blood and ticks. Of 168 dogs assessed, tick infestation prevalence was 53%, composed of exclusively Rh. sanguineus s. l. (n = 2170 ticks). Using PCR and sequencing, we identified an overall rickettsiae infection prevalence of 4.1% (n = 12/292) in ticks, in which eight dogs harbored at least one infected tick. Rickettsiae infections included Rickettsia amblyommatis and Rickettsia parkeri, both of which are emerging human pathogens, as well as Candidatus Rickettsia andeanae. This is the first documentation of pathogenic Rickettsia species in Rh. sanguineus s.l. collected from dogs from northeastern México. Domestic dog infestation with Rickettsia-infected ticks indicates ongoing transmission; thus, humans are at risk for exposure, and this underscores the importance of public and veterinary health surveillance for these pathogens.

Background: The canine heartwormDirofilaria immitis,a filarioid nematode of dogs and other carnivores, is widespread in the USA and the world. Over 20 different mosquito species serve as intermediate hosts ofD. immitis, but their contribution to transmission varies according to factors like host feeding patterns, geographic locations and climatic conditions. The yellow fever mosquito,Aedes aegypti,is a competent vector ofD. immitisbut is often dismissed as a vector of veterinary relevance given its anthropophilic feeding behavior. We evaluated the prevalence ofD.immitisin pet dogs along the USA-Mexico border and assessed whetherAe.aegyptiin the area are naturally infected with heartworm and are potentially acting as a vector.Methods: A total of 200 whole blood samples collected from pet dogs in the Lower Rio Grande Valley in south Texas from 2016 to 2019 were included in this study. Canine serum samples forD. immitiswere tested using the DiroCHEK® Canine Heartworm Antigen Test Kit pre- and post-immune complex dissociations (ICD) and blood samples were tested using high-resolution melt (HRM) quantitative PCR (qPCR) and a probe-based qPCR. Additionally, mosquito specimens were collected and identified, andAe. aegyptiheads, abdomens and pools were tested using conventional PCR (cPCR) and HRM qPCR.Results: Overall, heartworm prevalence in dogs aged > 6 months was 40.8% (64/157) when the results from all testing modalities were considered. Heartworm antigen was detected in 33.5% and 40.7% of the dogs using DiroCHEK® pre- and post-ICD, respectively. By molecular screening, 20.1% of dogs tested positive with probe-based qPCR, while only one tested positive with HRM qPCR. Of theAe. aegyptiabdomens from blood-fedAe. aeygptitested, 20 (21.7%) from mosquitoes that fed on dogs and four (7%) from those that fed on humans tested positive for heartworm. AmongAe. aegyptiheads from blood-fedAe. aeygpti, two (1.1%) were positive based on cPCR and four (2.5%) were positive based on HRM qPCR. NoD. immitisDNA was detected in the 208 pools of whole bodies (358 individuals) ofAe. aegyptigravid females.Conclusions: Our study highlights a high prevalence of heartworm in dogs in south Texas and provides evidence thatAe. aegypticould be contributing to heartworm transmission in canine populations in this region.Graphical

Of the documented tick-borne diseases infecting humans in Mexico, Rocky Mountain spotted fever (RMSF), caused by the gram-negative bacterium Rickettsia rickettsia, is responsible for most fatalities. Given recent evidence of brown dog tick, Rhipicephalus sanguineus sensu lato, as an emerging vector of human RMSF, we aimed to evaluate dogs and their ticks for rickettsiae infections as an initial step in assessing the establishment of this pathosystem in a poorly studied region of northeastern Mexico while evaluating the use of dogs as sentinels for transmission/human disease risk. We sampled owned dogs living in six disadvantaged neighborhoods of Reynosa, Northern Mexico to collect whole blood and ticks. Of 168 dogs assessed, tick infestation prevalence was 53%, comprised of exclusively R. sanguineus s. l. (n=2,170 ticks). Using PCR and sequencing, we identified an overall rickettsiae infection prevalence of 4.1% (n=12/292) in ticks, in which eight dogs harbored at least one infected tick. Rickettsiae infections included R. amblyommatis and R. parkeri, both of which are emerging human pathogens, as well as candidatus R. andeanae. This is the first documentation of pathogenic Rickettsia in R. sanguineus s.l. collected on dogs from northeastern Mexico. Domestic dog infestation with Rickettsia-infected ticks indicates ongoing transmission, thus humans are at risk for exposure and underscores the importance of public and veterinary health surveillance for these pathogens.