About

Gabriel Hamer, Ph.D., is a Professor in the Texas A&M University Department of Entomology. His research and teaching broadly investigate the ecology and control of infectious diseases affecting humans, wild animals, and domestic animals, with particular attention to those transmitted by arthropod vectors such as mosquitoes, ticks, and kissing bugs. He has studied vector-host interactions that lead to parasite amplification and increased disease risk, and develops and evaluates vector control approaches aimed at reducing human and animal disease. Hamer employs multidisciplinary tools including molecular biology, landscape epidemiology, immunology, and modeling to study these complex disease systems. A primary goal of his research is to elucidate mechanisms of disease transmission across space and time to facilitate effective management and preventative strategies.

Research topics

• Virology
• Medicine
• Biology
• Veterinary medicine
• Internal medicine
• Zoology
• Immunology
• Ecology
• Computer Science
• Geography
• Data science
• Engineering
• Operations research
• Food science
• Toxicology
• Environmental resource management
• Risk analysis (engineering)

Selected publications

• Active surveillance reveals common SARS-CoV-2 infections among cats and dogs from households with human COVID-19 cases in Texas, USA

  One Health · 2026-03-03

  articleOpen access

  Households where people have COVID-19 are high-risk environments for companion animals to become infected by SARS-CoV-2. We sampled 579 pets from 281 households with one or more laboratory-confirmed persons with COVID-19 in central Texas from June 2020 to May 2021. Nineteen out of 396 (4.8%) dogs and 21 out of 157 (13.4%) cats were positive for SARS-CoV-2 by RT-qPCR. Additionally, 95/382 (25%) dogs and 52/146 (36%) cats harbored SARS-CoV-2 neutralizing antibodies. Twenty-six companion animals of ten other species were negative. Overall, 164 (29%) pets were positive for SARS-CoV-2 by molecular and/or serological tests; a total of 110 (39%) out of 281 households had at least one animal with active or past SARS-CoV-2 infection. Cats were more likely to be infected by SARS-CoV-2 and had higher endpoint antibody titers than dogs. We detected 11 SARS-CoV-2 lineages and isolated five of them from dogs and cats, including the B.1.234 lineage that was isolated from a cat a few weeks after the first detection in humans in the United States. Detection of SARS-CoV-2 RNA decreased by 10% per additional day post COVID-19 diagnosis of the human case in the household for both dogs and cats, whereas seropositivity odds increased with each additional day. Human-pet interactions associated with a higher risk of infection in dogs and cats included sleeping in the same room as an infected person, living with multiple infected persons, and sharing food with people. The frequency of clinical signs in pets with active infections did not differ from uninfected ones, suggesting that not all reported signs are attributed to SARS-CoV-2 infection. Characterizing animal infections using active SARS-CoV-2 surveillance in pets at risk of infection may aid in One Health pandemic prevention, response, and management.

  PublisherDOI

• Triatomine host preference in an experimental cafeteria: the impact of Trypanosoma cruzi infections

  bioRxiv (Cold Spring Harbor Laboratory) · 2026-01-14

  articleOpen access

  Background Hematophagous triatomine vectors of the Chagas disease parasite, Trypanosoma cruzi, have a wide bloodmeal host breadth yet mammals are the primary competent reservoirs for T. cruzi. Accordingly, the transmission of T. cruzi is dependent on triatomines encountering mammalian hosts. We hypothesized T. cruzi-infected triatomines exhibit a preference for mammalian versus non-mammalian hosts, as compared to uninfected triatomines. Methodology/Principal Findings We used a dual-choice olfactometer to present individual T. cruzi-infected and uninfected Triatoma gerstaeckeri- an important North American triatomine species- to pairwise combinations of no host, dog, human, or chicken. We found that uninfected T. gerstaeckeri preferred dogs over chickens and humans, but T. cruzi-infected T. gerstaeckeri had no host preference. Additionally, T. cruzi-infected T. gerstaeckeri took less time to begin advancing towards hosts (average of 522 s ± 577 s vs 801 s ± 704 s) and spent more time on both sides of the olfactometer compared to uninfected insects. As a comparative group, we tested Rhodnius prolixus- a potent South American vector- and found no statistical preference among hosts, yet they advanced towards hosts more often (63.2% vs 47.1%) and faster compared to T. gerstaeckeri. Conclusions/Significance The increased locomotion of R. prolixus and T. cruzi-infected T. gerstaeckeri toward hosts may promote increased transmission of T. cruzi. Dogs are a preferred host for T. gerstaeckeri and may be considered in future host-targeted interventions for triatomine control.

  PublisherOA PDFDOI

• Advancing the design of the kissing bug kill trap for surveillance of triatomines

  PLoS neglected tropical diseases · 2026-02-27

  articleOpen accessSenior author

  Standardized surveillance and control of kissing bugs (Hemiptera: Reduviidae: Triatominae), the insect vectors of the Chagas disease parasite, Trypanosoma cruzi, which causes Chagas disease, remains difficult. The Kissing Bug Kill Trap consists of solar powered LED lights mounted over a column of black funnels. It operates autonomously to capture, kill and preserve adult triatomines. We conducted experiments from 2022-2024 testing potential ways to improve trap performance, ease of deployment, and minimize cost. Thirteen prototypes evaluated in Texas, Guatemala, and Mexico captured 1,531 triatomines. In 2022-2023 we selected a six-funnel trap suspended from a single support pole with an angle bracket, and with four LED lights and a solar panel mounted above the rain-guard, as a reference trap. In 2023, traps with smaller funnels, blue funnels, and blue lights were inferior to the reference trap based on high by-catch of other arthropods and/or fewer triatomines caught per day. In 2024, traps with more or fewer than six funnels or with LED lights mounted on or below the rain guard did not outperform the reference trap. The experiments added five new triatomine species to the four already known to be caught by the Kissing Bug Kill Trap and revealed differences and similarities in phenology of dispersal flights of Triatoma gerstaeckeri over a three-year period in Texas. The reference trap was selected as the pre-commercial prototype, based on its suitability for triatomine surveillance and potential for reducing the risk of T. cruzi infection by intercepting dispersing adult triatomines before they reach human habitats.

  PublisherDOI

• Investigating the use of human COVID-19 rapid assays to detect antibody and antigen in domesticated dogs ( <i>Canis lupus familiaris</i> ) and cats ( <i>Felis catus</i> )

  bioRxiv (Cold Spring Harbor Laboratory) · 2026-03-05

  articleOpen access

  Abstract Severe acute respiratory syndrome coronavirus-2 (SARS-CoV-2), the virus that causes coronavirus disease-2019 (COVID-19) in humans, is also known to infect animals including dogs ( Canis lupus familiaris ) and cats ( Felis catus ). This study evaluated the efficacy of human COVID-19 rapid antigen and antibody tests in dogs and cats. Nasal/oral swabs from 60 animals (32 dogs, 28 cats) and serum from 40 animals (20 dogs, 20 cats) were tested. Rapid antigen tests used on respiratory swabs showed low-to-moderate sensitivity (75% dogs, 57% cats) and moderate-to-high specificity (79% dogs, 95% cats) compared to RT-PCR. Rapid antibody tests used on serum samples demonstrated low-to-moderate sensitivity (70% dogs, 50% cats) and moderate-high specificity (60% dogs, 100% cats) compared to PRNT. While imperfect, these test kits may have some utility for field surveillance studies, particularly when species-specific rapid SARS-CoV-2 assays for dogs and cats are unavailable. These test characteristics in dogs and cats are similar to the findings from studies of the same types of tests in humans which have found an average sensitivity and specificity of common commercially available kits in the US range from 50.0-84.3% and 64.5-74.3%, respectively, when used with human samples (1,2).

  PublisherDOI

• Bloodmeal metabarcoding reveals host feeding patterns for Aedes aegypti and Culex quinquefasciatus in Jutiapa, Guatemala and Texas, USA

  Research Square · 2026-02-19

  preprintOpen accessSenior author
  PublisherDOI

• High SARS-CoV-2 Exposure in Feline Residents of a Cat Café in Texas, United States, 2021–2022

  Preprints.org · 2025-03-13 · 1 citations

  preprintOpen access

  Congregate animal settings can serve as foci for increased transmission of pathogens, including zoonoses. Domestic cats have been shown to be reservoirs for SARS-CoV-2 but the public health importance of infected cats has not yet been determined. A population of indoor-only residential cats at a cat cafè in central Texas with high level of human interaction was evaluated for infection with SARS-CoV-2 in a longitudinal study in 2021-2022. Among 25 cats, none were qRT-PCR-positive, while 50% harbored SARS-CoV-2 neutralizing antibodies, including one that remained seropositive for &amp;gt;8 months. The high level of human exposure in this unique congregate cat setting- in which dozens of new visitors interact with the cats every day- likely facilitated the hu-man-to-cat transmission of SARS-CoV-2 that led to a 50% infection prevalence in cats. This work was conducted when Delta and Omicron variants predominated. Given feline susceptibility to infection and shedding of virus may vary across different viral variants, veterinary surveillance may be an important component of veterinary and human health risk assessments.

  PublisherOA PDFDOI

• SARS-CoV-2 exposure in dogs before and after the largest COVID-19 wave in rural Guatemala, 2022

  One Health · 2025-10-25

  articleOpen access

  The SARS-CoV-2 pandemic burdened low- and mid-income countries during many waves of high transmission, particularly in rural communities. We tested whether dogs from rural households were exposed to SARS-CoV-2 before and after the largest COVID-19 wave in Guatemala. We tested dogs in June and August 2022, before the rise and after the initial peak of the second Omicron wave, respectively. None of the 133 dogs tested (63 tested in June and 70 tested in August) had evidence of SARS-CoV-2 RNA in respiratory swabs. Three dogs in June and five dogs in August had neutralizing antibodies against SARS-CoV-2. Risk factor analysis showed that the largest COVID-19 wave in Guatemala did not increase dog exposure to SARS-CoV-2. However, dogs with outdoor access had higher odds of infection compared to indoors-only dogs. Public health interventions should provide education regarding pet roaming practices to mitigate the spread of zoonotic diseases in rural areas. • Evaluating dog exposure to SARS-CoV-2 before and after an Omicron wave in Guatemala. • Access outside of household was associated with higher dog exposure to SARS-CoV-2. • The largest COVID-19 wave did not increase dog exposure to SARS-CoV-2.

  PublisherDOI

• <i>Triatoma dimidiata,</i> domestic animals and acute Chagas disease: A 10 year follow-up after an eco-bio-social intervention

  medRxiv · 2025-03-13 · 1 citations

  preprintOpen access

  Abstract Introduction Trypanosoma cruzi , the causative agent of Chagas disease, is primarily transmitted by triatomine insects, including Triatoma dimidiata . In Central America, vector control programs have significantly reduced transmission; however, certain regions, such as Comapa, Jutiapa, Guatemala, continue to experience persistent T. dimidiata infestation. This study presents a 10-year follow-up assessment of triatomine infestation, T. cruzi infection, and acute Chagas disease cases after an eco-bio-social intervention. Methods Between June and August 2022, entomological surveys were conducted in four communities of Comapa. Seventy six households were systematically searched for triatomines using the one-person hour method, which were collected and processed for T. cruzi detection using qPCR. Bloodmeal analysis was performed to assess host feeding patterns. Dog samples and environmental DNA from household surfaces were also processed for T. cruzi detection. Additionally, surveillance for acute Chagas disease cases was carried out in collaboration with the Ministry of Health. Results Persistent infestation of T. dimidiata was observed across all communities, with infestation rates ranging from 17–38% and colonization levels between 9–29%. The mean household triatomine density remained low, suggesting a possible reduction in transmission risk. A total of 86 triatomines were collected, of which 26% tested positive for T. cruzi (all TcI strain). Amplicon deep sequencing analysis from triatomines identified seven vertebrate species and one insect family as hosts upon which triatomines have previously fed, with chickens being the most common blood source (occurring in 57% of triatomines), along with rats, dogs, humans, cats, pigs, ducks, and one genus of cockroach. Of the 132 dogs processed 22% were positive for T. cruzi (all TcI). One acute Chagas disease case detected in a child in 2015 remained seropositive in 2022, emphasizing the need for continued surveillance. Conclusions Despite multiple interventions over a decade, T. dimidiata infestation remains high in Comapa with sustained evidence of actue disease in humans, necessitating continued vector control efforts. The persistence of T. cruzi transmission among triatomines and dogs and the predominant role of chickens in supporting the vector population highlights the need for innovative control strategies including those that target domestic animals to mitigate Chagas disease risk.

  PublisherOA PDFDOI

• High SARS-CoV-2 Exposure in Feline Residents of a Cat Café in Texas, United States, 2021–2022

  Veterinary Sciences · 2025-04-21

  articleOpen access

  Congregate animal settings can serve as foci for the increased transmission of pathogens, including zoonoses. Domestic cats have been shown to be reservoirs for SARS-CoV-2 but the public health importance of infected cats has not yet been determined. A population of indoor-only residential cats at a cat café in central Texas with a high level of human interaction was evaluated for infection with SARS-CoV-2 in a longitudinal study in 2021-2022. Among 25 cats, none were qRT-PCR-positive, while 50% harbored SARS-CoV-2-neutralizing antibodies, including 1 that remained seropositive for >8 months. The high level of human exposure in this unique congregate cat setting-in which dozens of new visitors interact with the cats every day-likely facilitated the human-to-cat transmission of SARS-CoV-2 that led to a 50% infection prevalence in cats. This work was conducted when the Delta and Omicron variants predominated. Given that feline susceptibility to infection and shedding of a virus may vary across different viral variants, veterinary surveillance may be an important component of veterinary and human health risk assessments.

  PublisherOA PDFDOI

• Transmission potential of <i>Culex</i> and <i>Aedes</i> species for Madariaga virus, a member of the eastern equine encephalitis virus complex

  bioRxiv (Cold Spring Harbor Laboratory) · 2025-09-04

  preprintOpen access

  Abstract Madariaga virus (MADV), widely distributed in Latin America, can cause severe disease in humans and equids, yet, key aspects of its transmission cycle remain unclear. To identify mosquitoes that could act as MADV vectors, we assessed the vector competence of Aedes aegypti , Ae. albopictus , Ae. taeniorhynchus , Culex tarsalis , Cx. coronator , and Cx. quinquefasciatus , following oral exposure to MADV isolated in Panama (all species) or Brazil ( Ae. taeniorhynchus only). MADV RNA and infectious virus were quantified from mosquito bodies, legs, and saliva. At 14 days post-exposure, five species had virus in all biological sample types. Culex quinquefasciatus was susceptible to infection and dissemination but had no positive saliva samples. Aedes taeniorhynchus showed higher infection probabilities with MADV-BR. Time-course analysis revealed distinct dynamics in Ae. aegypti and Ae. albopictus . Our findings indicate MADV may be compatible with mosquito species present in endemic regions and areas at risk of virus introduction.

  PublisherOA PDFDOI

Recent grants

• Social-ecological factors influencing receptivity to Zika virus and the efficacy of interventions in communities along the Texas-Mexico border

  NIH · $408k · 2016–2019

• Consequences of pathogen co-infection in mosquitoes on West Nile virus transmission

  NIH · $430k · 2017–2021

Frequent coauthors

• Sarah A. Hamer

  Texas A&M University

  100 shared

• José G. Juárez

  Universidad del Valle de Guatemala

  88 shared

• Ester Carbajal

  65 shared

• Katherine L. Dickinson

  57 shared

• Edward D. Walker

  Michigan State University

  57 shared

• Jeffrey D. Brawn

  University of Illinois Urbana-Champaign

  55 shared

• Tony L. Goldberg

  University of Wisconsin Health

  47 shared

• Marilyn O. Ruiz

  University of Illinois Urbana-Champaign

  41 shared

Awards & honors

• Subject Editor for the Journal of Medical Entomology
• Past Chair of the American Committee of Medical Entomology