Free-roaming kissing bugs, vectors of Chagas disease, feed often on humans in the Southwest

Trypanosoma cruzi infection in dogs along the US-Mexico border: R0 changes with vector species composition

Infection with Trypanosoma cruzi, etiological agent of Chagas disease, is common in US government working dogs along the US-Mexico border. This 3145 km long border comprises four states: Texas (TX), New Mexico (NM), Arizona (AZ) and California (CA) with diverse ecosystems and several triatomine (a.k.a., kissing bug) species, primary vectors of T. cruzi in this region. The kissing bug (Heteroptera: Reduviidae) community ranging from CA to TX includes Triatoma protracta (Uhler), Triatoma recurva (Stål) and Triatoma rubida (Uhler) and becomes dominated by Triatoma gerstaeckeri Stål in TX. Here, we ask if T. cruzi infection dynamics in dogs varies along this border region, potentially reflecting changes in vector species and their vectorial capacity. Using reversible catalytic models of infection, where seropositivity can be lost, we estimated an R0 (Estimate ± S.E.) of 1.192 ± 0.084 for TX and NM. In contrast, seropositivity decayed to zero as dogs aged in AZ and CA. These results suggest that dogs are likely infected by T. cruzi during their training in western TX, with a force of infection large enough for keeping R0 above 1, i.e., the disease endemically established, in TX and NM. In AZ and CA, a lower force of infection, probably associated with different vector species communities and associated vectorial capacity and/or different lineages of T. cruzi, results in dogs decreasing their seropositivity with age.

Coconut fatty acids exhibit strong repellency and week-long efficacy against several urban pest arthropods of the southwestern United States

BACKGROUND

The southwestern United States is home to a variety of arthropods including Turkestan cockroaches, Blatta lateralis (Walker); hematophagous kissing bugs, Tritoma rubida (Uhler); and Arizona bark scorpions, Centruroides sculpturatus Ewing. These arthropods cause medical concern when they become established around homes and/or invade indoors. Traditionally, the management of these pests has relied primarily on the use of chemical insecticides; however, they offer poor prospects for control owing to their lack of efficacy as well as the effects of insecticides on humans and the environment. Botanical repellents are an option that has not been fully investigated for the management of these pests. Here, we investigated the behavioral responses of common urban pests of the southwestern USA to recently discovered coconut fatty acids (CFAs), to establish the potential use of these compounds as repellents.

RESULTS

Fresh residues of CFA mixture (CFAm) and their constituents caprylic acid, capric acid, capric acid methyl ester, lauric acid, and lauric acid methyl ester, tested at a concentration of 1 mg cm-2 , strongly repelled all arthropods. The repellent activity of CFAm lasted for at least 7 days, and the addition of lavender oil, used as an odor-masking agent, did not decrease this effect. Concentrations of CFAm ten times lower (0.1 mg cm-2 ) still repelled Turkestan cockroaches, and concentrations 100 times lower (0.01 mg cm-2 ) repelled T. rubida and scorpions.

CONCLUSIONS

CFAm and some of their constituents are efficacious, economical, and logistically feasible for inclusion in integrated pest management programs for these important urban pests of the southwestern USA. © 2023 Society of Chemical Industry.

Integrated pest management strategies targeting the Florida kissing bug, Triatoma sanguisuga: Preventing this vector of Chagas disease from invading your home

Triatomines (Hemiptera: Reduviidae: Triatominae), commonly called "kissing bugs", are blood-sucking pests and vectors of the protozoan parasite Trypanosoma cruzi, the causative agent of Chagas disease (CD). Eleven species of kissing bugs occur throughout the southern half of the USA, four of which are well known to invade human dwellings. Certain kissing bugs in the USA are known to transmit T. cruzi to humans and other animals and their bites can also lead to serious allergic reactions, including anaphylaxis. In Florida, the kissing bug Triatoma sanguisuga frequently invades homes, bites residents, and has been found infected with T. cruzi, placing humans and companion animals at risk for CD. This review outlines integrated pest management (IPM) strategies for minimizing human exposure to T. sanguisuga and CD. A comprehensive IPM plan for kissing bugs includes detailed inspections, removal of vertebrate host nesting areas, and kissing bug harborage, home improvements to exclude kissing bugs from entering structures, pest removal, and judicious use of pesticides. This approach can limit or eliminate kissing bug entry into residential structures, thereby preventing kissing bug bites, and CD infections in humans and companion animals.

Detection of Bartonella in kissing bugs Triatoma rubrofasciata collected from Huizhou City, South China

Background

The blood-feeding behavior of kissing bugs (subfamily Triatominae, family Reduviidae, order Hemiptera) means they are potential vectors of multiple humans pathogens. However, investigations of vector-borne pathogens harbored by kissing bugs are rare.

Methods

In the current study, 22 adult kissing bugs (Triatoma rubrofasciata) were captured in Huizhou City, Guangdong Province, south China. The presence of vector-borne pathogens in the kissing bugs was tested, and the genetic diversity of these potential pathogens was investigated.

Results

All the kissing bugs were negative for Anaplasmataceae bacteria, Rickettsia, and Coxiella. Bartonella DNA was detected in 36.4% (8/22) of the kissing bugs. The sequences of the Bartonella gltA genes divided into two clades in a phylogenetic tree, with close relationships to B. tribocorum and uncultured Bartonella sp. clone MYR-283, respectively. All the groEL sequences were closely related to those of B. kosoyi (identity 98.75%-100%). The ftsZ and rpoB sequences were most closely related to those of B. elizabethae, a recognized human pathogen, with nucleotide similarities of 98.70%-100% and 99.45%-100%, respectively.

Conclusions

We report the detection of Bartonella DNA in Triatoma kissing bugs in southern China. Although the sample size is limited, the high positive rate of detection of Bartonella DNA, the close relationship of the gene sequences to those of zoonotic Bartonella species, and the distribution of the kissing bugs near human residences, hint at a risk to public health.

Identifying Barriers and Facilitators for Home Reconstruction for Prevention of Chagas Disease: An Interview Study in Rural Loja Province, Ecuador

BACKGROUND

Chagas disease (CD) is a tropical parasitic disease spread by triatomine bugs, which are bugs that tend to infest precarious housing in rural and impoverished areas. Reducing exposure to the bugs, and thus the parasite they can carry, is essential to preventing CD in these areas. One promising long-term sustainable solution is to reconstruct precarious houses. Implementing home reconstruction requires an understanding of how householders construct barriers and facilitators they might encounter when considering whether to rebuild their homes.

METHODS

To understand barriers and facilitators to home reconstruction, we performed in-depth qualitative interviews with 33 residents of Canton Calvas, Loja, Ecuador, a high-risk endemic region. Thematic analysis was used to identify these barriers and facilitators.

RESULTS

The thematic analysis identified three facilitators (project facilitators, social facilitators, and economic facilitators) and two major barriers (low personal economy and extensive deterioration of existing homes).

CONCLUSIONS

The study findings provide important loci for assisting community members and for agents of change in home reconstruction projects to prevent CD. Specifically, the project and social facilitators suggest that collective community efforts (minga) are more likely to support home reconstruction intentions than individualist efforts, while the barriers suggest that addressing structural issues of economy and affordability are necessary.

Collection of triatomines from sylvatic habitats by a Trypanosoma cruzi-infected scent detection dog in Texas, USA

BACKGROUND

Triatomine insects, vectors of the etiologic agent of Chagas disease (Trypanosoma cruzi), are challenging to locate in sylvatic habitats. Collection techniques used in the United States often rely on methods to intercept seasonally dispersing adults or on community scientists' encounters. Neither method is suited for detecting nest habitats likely to harbor triatomines, which is important for vector surveillance and control. Furthermore, manual inspection of suspected harborages is difficult and unlikely to reveal novel locations and host associations. Similar to a team that used a trained dog to detect sylvatic triatomines in Paraguay, we worked with a trained scent detection dog to detect triatomines in sylvatic locations across Texas.

PRINCIPLE METHODOLOGY/FINDINGS

Ziza, a 3-year-old German Shorthaired Pointer previously naturally infected with T. cruzi, was trained to detect triatomines. Over the course of 6 weeks in the fall of 2017, the dog and her handler searched at 17 sites across Texas. The dog detected 60 triatomines at 6 sites; an additional 50 triatomines were contemporaneously collected at 1 of these sites and 2 additional sites without the assistance of the dog. Approximately 0.98 triatomines per hour were found when only humans were conducting searches; when working with the dog, approximately 1.71 triatomines per hour were found. In total, 3 adults and 107 nymphs of four species (Triatoma gerstaeckeri, Triatoma protracta, Triatoma sanguisuga, and Triatoma indictiva) were collected. PCR testing of a subset revealed T. cruzi infection, including DTUs TcI and TcIV, in 27% of nymphs (n = 103) and 66% of adults (n = 3). Bloodmeal analysis of a subset of triatomines (n = 5) revealed feeding on Virginia opossum (Didelphis virginiana), Southern plains woodrat (Neotoma micropus), and eastern cottontail (Sylvilagus floridanus).

CONCLUSION/SIGNIFICANCE

A trained scent detection dog enhanced triatomine detections in sylvatic habitats. This approach is effective at detecting nidicolous triatomines. Control of sylvatic sources of triatomines is challenging, but this new knowledge of specific sylvatic habitats and key hosts may reveal opportunities for novel vector control methods to block the transmission of T. cruzi to humans and domestic animals.

Southwestern national park service employee risk, knowledge, and concern for triatomine exposure: A qualitative analysis using a novel knowledge, attitudes, and practices survey

Chagas disease (CD), caused by the parasite Trypanosoma cruzi, is a neglected parasitic infection in the United States (US). In the Southwestern US, National Park Service (NPS) employees are a unique population with potential exposure to CD. This population lives in close contact with several species of sylvatic triatomine bugs, the vectors of T. cruzi, that may enter residential buildings at night. Despite the higher potential risk of CD transmission for southwestern NPS employees, the socio-cultural factors that impact autochthonous CD transmission in the US remain unknown. To address this gap, we investigated how NPS employee knowledge and attitudes impact their triatomine preventive behaviors. We distributed a 42-item online questionnaire to NPS employees at four national parks in Arizona and Texas. We detected high self-reported bite exposure in NPS housing, despite moderate- to high-frequency of prevention behaviors. Specific behaviors, such as often or always repairing window screens, were associated with a decreased risk of putative triatomine bug exposure. Additionally, NPS employees had low knowledge of CD. For those with greater knowledge of CD, it was not associated with increased frequency of prevention behavior. We found that increased CD anxiety was associated with increased personal agency to reduce the risk of CD. These results demonstrate the influence of knowledge and attitudes regarding CD on triatomine prevention behavior within a potential high-risk population in the US, and the importance of utilizing strategies beyond provision of education to influence behaviors.

Chagas disease (CD), a neglected vector-borne disease, negatively impacts 300,000 United States citizens in present time. The parasite that causes CD, Trypanosoma cruzi, is spread through the infected feces of triatomine bugs. Vector-borne transmission risk is considered highest in the southwestern United States, where there is greater triatomine diversity. Southwestern National Park Service (NPS) employees are a unique population regarding human-CD risk because they live in close contact with several species of triatomines. However, CD transmission does not solely result from biological factors; sociocultural factors, including what human populations understand and what they do in response to a disease, are integral for vector-borne agent spread. Therefore, we investigated how NPS employee knowledge and attitudes impact their triatomine preventive behaviors. We detected high self-reported triatomine bug bite exposure in southwestern national parks. Additionally, NPS employees overall had low knowledge of CD, but greater knowledge of CD was not associated with better practices. Human emotions, behavior, and environmental factors are deeply rooted within the CD transmission cycle. This research adds to the growing body of literature on the CD knowledge, attitudes, and practices of a high-risk population in the US.

Characterization of triatomine bloodmeal sources using direct Sanger sequencing and amplicon deep sequencing methods

Knowledge of host associations of blood-feeding vectors may afford insights into managing disease systems and protecting public health. However, the ability of methods to distinguish bloodmeal sources varies widely. We used two methods—Sanger sequencing and amplicon deep sequencing—to target a 228 bp region of the vertebrate Cytochrome b gene and determine hosts fed upon by triatomines (n = 115) collected primarily in Texas, USA. Direct Sanger sequencing of PCR amplicons was successful for 36 samples (31%). Sanger sequencing revealed 15 distinct host species, which included humans, domestic animals (Canis lupus familiaris, Ovis aries, Gallus gallus, Bos taurus, Felis catus, and Capra hircus), wildlife (Rattus rattus, Incilius nebulifer, Sciurus carolinensis, Sciurus niger, and Odocoileus virginianus), and captive animals (Panthera tigris, Colobus spp., and Chelonoidis carbonaria). Samples sequenced by the Sanger method were also subjected to Illumina MiSeq amplicon deep sequencing. The amplicon deep sequencing results (average of 302,080 usable reads per sample) replicated the host community revealed using Sanger sequencing, and detected additional hosts in five triatomines (13.9%), including two additional blood sources (Procyon lotor and Bassariscus astutus). Up to four bloodmeal sources were detected in a single triatomine (I. nebulifer, Homo sapiens, C. lupus familiaris, and S. carolinensis). Enhanced understanding of vector-host-parasite networks may allow for integrated vector management programs focusing on highly-utilized and highly-infected host species.

Seasonal Flight Pattern of the Kissing Bugs Triatoma rubida and T. protracta (Hemiptera: Reduviidae: Triatominae) in Southern Arizona, United States

The two most common kissing bugs, Triatoma rubida and T. protracta, in the Sonoran Desert around Tucson, Arizona are hematophagous vectors of Chagas disease and can induce potentially life-threatening allergic reactions. They were surveyed during their summer dispersal flight period to determine which environmental factors are correlated with flight activity. The two most important factors governing flights of T.rubida were temperatures in the range of 26–35 °C and wind speeds below 14 km/h (9 miles/h). Flights were reduced below or above those temperatures, or when wind speeds exceeding 14km/h. Relative humidity and presence or absence of moonshine appeared unimportant. During their dispersal flight periods of May through July and, especially, between the peak of the flight season, 20 June to 5 July, biologists seeking to collect bugs and homeowners wishing to exclude these biting bugs from entering their homes should be most attentive during evenings of average temperature and low wind speed.

Chagas Disease Ecology in the United States: Recent Advances in Understanding Trypanosoma cruzi Transmission Among Triatomines, Wildlife, and Domestic Animals and a Quantitative Synthesis of Vector-Host Interactions

Chagas disease, a neglected tropical disease present in the Americas, is caused by the parasite Trypanosoma cruzi and is transmitted by triatomine kissing bug vectors. Hundreds of vertebrate host species are involved in the ecology of Chagas disease. The sylvatic nature of most triatomines found in the United States accounts for high levels of animal infections but few reports of human infections. This review focuses on triatomine distributions and animal infections in the southern United States. A quantitative synthesis of available US data from triatomine bloodmeal analysis studies shows that dogs, humans, and rodents are key taxa for feeding triatomines. Imperfect and unvalidated diagnostic tools in wildlife complicate the study of animal T. cruzi infections, and integrated vector management approaches are needed to reduce parasite transmission in nature. The diversity of animal species involved in Chagas disease ecology underscores the importance of a One Health approach for disease research and management. Expected final online publication date for the Annual Review of Animal Biosciences, Volume 10 is February 2022. Please see http://www.annualreviews.org/page/journal/pubdates for revised estimates.

Drug repurposing for Chagas disease: In vitro assessment of nimesulide against Trypanosoma cruzi and insights on its mechanisms of action

Chagas disease is a neglected illness caused by Trypanosoma cruzi and its treatment is done only with two drugs, nifurtimox and benznidazole. However, both drugs are ineffective in the chronic phase, in addition to causing serious side effects. This context of therapeutic limitation justifies the continuous research for alternative drugs. Here, we study the in vitro trypanocidal effects of the non-steroidal anti-inflammatory drug nimesulide, a molecule that has in its chemical structure a toxicophoric nitroaromatic group (NO2). The set of results obtained in this work highlights the potential for repurposing nimesulide in the treatment of this disease that affects millions of people around the world.

A Southwestern United States Pilot Investigation of Triatomine-Mite Prevalence

Simple Summary

An estimated 70 million persons in the Western Hemisphere are living at risk for Chagas disease, a parasitic infection transmitted to humans by over 156 different competent triatomine insect vector species. Prior Pan American Health Organization insecticide campaigns throughout Latin America in the 1990s and 2000s demonstrated that domestic insecticide spraying had temporary effects, which resulted in the re-establishment of triatomine species within a few years. Serendipitously, our team found ectoparasitic mites parasitizing triatomines collected from the field in multiple locations in the southwestern United States, where human–triatomine interaction was high but human parasite infection remains low. Upon further investigation of 408 triatomines collected across multiple field sampling sites in Arizona and New Mexico, 13% were found to be parasitized by mites. Mites were found on both Triatoma rubida and Triatoma protracta species and corporally dispersed on the head, thorax, abdomen and legs of these species. Interestingly, there was no statistical difference in Trypanosoma cruzi infection status between parasitized and unparasitized triatomines. Upon further review of the scientific literature, two Latin American-based studies suggest that the presence of mites on triatomines might reduce vector competency via decreased fitness and fecundity. This study provides the first contemporary report of triatomine ectoparasitism, which warrants further investigation as the biologic role of this host-attached mites on Trypanosoma cruzi transmission efficacy.

Abstract

Background: Chagas disease is a leading cause of cardiac failure in Latin America. Due to poor safety profiles and efficacy of currently available therapeutics, prevention is a priority for the millions living at risk for acquiring this clinically important vector-borne disease. Triatomine vectors of the Chagas disease parasite, Trypanosoma cruzi, are found in the southwestern United States, but risk for autochthonous transmission is thought to be low. The role of ectoparasitic mites is under-explored regarding the ecology of triatomines and Chagas disease transmission. Methods: Triatomine collections were performed using three common entomologic techniques in 2020–2021 from four different locations in southern Arizona and New Mexico. Triatomines were analyzed visually under a 112.5× microscope for the presence of externally attached mites. Following mite removal, triatomines were tested for T. cruzi infection by PCR. Results: Approximately 13% of the collected triatomines had mites securely attached to their head, thorax, abdomen, and legs. More than one mite attached was a common finding among ectoparasitized triatomines. Mite presence, however, did not statistically influence triatomine T. cruzi status. Conclusions: Our findings add to a growing body of literature demonstrating the sustainability of mite-infested triatomine populations throughout the Western Hemisphere. Future investigations are warranted to better understand the biologic impact of triatomine mites and their potential to serve as a potential biological control tool.

High variation in immune responses and parasite phenotypes in naturally acquired Trypanosoma cruzi infection in a captive non-human primate breeding colony in Texas, USA

Trypanosoma cruzi, the causative agent of human Chagas disease, is endemic to the southern region of the United States where it routinely infects many host species. The indoor/outdoor housing configuration used in many non-human primate research and breeding facilities in the southern of the USA provides the opportunity for infection by T. cruzi and thus provides source material for in-depth investigation of host and parasite dynamics in a natural host species under highly controlled and restricted conditions. For cynomolgus macaques housed at such a facility, we used a combination of serial blood quantitative PCR (qPCR) and hemoculture to confirm infection in >92% of seropositive animals, although each method alone failed to detect infection in >20% of cases. Parasite isolates obtained from 43 of the 64 seropositive macaques were of 2 broad genetic types (discrete typing units, (DTU's) I and IV); both within and between these DTU groupings, isolates displayed a wide variation in growth characteristics and virulence, elicited host immune responses, and susceptibility to drug treatment in a mouse model. Likewise, the macaques displayed a diversity in T cell and antibody response profiles that rarely correlated with parasite DTU type, minimum length of infection, or age of the primate. This study reveals the complexity of infection dynamics, parasite phenotypes, and immune response patterns that can occur in a primate group, despite being housed in a uniform environment at a single location, and the limited time period over which the T. cruzi infections were established.

Autochthonous Chagas Disease in the United States: How Are People Getting Infected?

In the United States, Chagas disease is diagnosed in less than 1% of the estimated > 300,000 people who have the disease. However, the actual prevalence remains unknown, and these estimates may be wide of the mark (too high or too low). The greater part of those living with the disease acquired the infection in an endemic region of Latin America, but autochthonous transmission in the United States is increasingly being described. These cases are considered rare, and the transmission routes are largely unknown. Although triatomines or "kissing bugs" harbor Trypanosoma cruzi in North America, most autochthonous cases are presumed rather than confirmed exposures to naturally infected kissing bugs. Public knowledge of Chagas is growing, and efforts are underway to provide greater awareness, but what are the risk factors for human transmission of Chagas disease in the United States?

Interactions among Triatoma sanguisuga blood feeding sources, gut microbiota and Trypanosoma cruzi diversity in southern Louisiana

Integrating how biodiversity and infectious disease dynamics are linked at multiple levels and scales is highly challenging. Chagas disease is a vector-borne disease, with specificities of the triatomine vectors and Trypanosoma cruzi parasite life histories resulting in a complex multihost and multistrain life cycle. Here, we tested the hypothesis that T. cruzi transmission cycles are shaped by triatomine host communities and gut microbiota composition by comparing the integrated interactions of Triatoma sanguisuga in southern Louisiana with feeding hosts, T. cruzi parasite and bacterial microbiota in two habitats. Bugs were collected from resident's houses and animal shelters and analysed for genetic structure, blood feeding sources, T. cruzi parasites, and bacterial diversity by PCR amplification of specific DNA markers followed by next-generation sequencing, in an integrative metabarcoding approach. T. sanguisuga feeding host communities appeared opportunistic and defined by host abundance in each habitat, yielding distinct parasite transmission networks among hosts. The circulation of a large diversity of T. cruzi DTUs was also detected, with TcII and TcV detected for the first time in triatomines in the US. The bacterial microbiota was highly diverse and varied significantly according to the DTU infecting the bugs, indicating specific interactions among them in the gut. Expanding such studies to multiple habitats and additional triatomine species would be key to further refine our understanding of the complex life cycles of multihost, multistrain parasites such as T. cruzi, and may lead to improved disease control strategies.

Contemporary autochthonous human Chagas disease in the USA

Chagas disease is a leading cause of non-ischemic cardiomyopathy in Latin America and an infection of emerging importance in the USA. Recent studies have uncovered evidence of an active peridomestic cycle in southern states, yet autochthonous transmission to humans has been rarely reported. We conducted a systematic review of the literature and public health department reports to investigate suspected or confirmed locally acquired cases of Chagas in the USA. We found 76 cases of contemporary suspected or confirmed locally acquired Chagas disease, nearly ten times the case counts cited in the prior 50 years of scientific literature. Shared risk factors among cases include rural residence, history of hunting or camping, and agricultural or outdoor work. The results of this review suggest that the disease burden and risk of autochthonous Chagas infection is potentially higher in the USA than previously recognized.

Raccoons As an Important Reservoir for Trypanosoma cruzi: A Prevalence Study from Two Metropolitan Areas in Louisiana

Raccoons are an important reservoir for Trypanosoma cruzi infection, having been reported to maintain a high and lengthy parasitemia. Although raccoon populations have historically been abundant in Louisiana, the prevalence rate of T. cruzi infection in raccoons in this state is unknown. Here, we tested raccoon tissues from two urban areas in Louisiana, namely Orleans Parish (OP) and East Baton Rouge Parish (EBRP), to investigate prevalence in these areas using direct detection through polymerase chain reaction. Overall, 33.6% of raccoons tested were positive. The prevalence in OP (42.9%) was significantly higher than the prevalence in EBRP (23.2%). There was no significant difference in prevalence between sexes or based on age, but there was a significant difference in infection prevalence based on season of trapping. These results suggest the importance of raccoons as a reservoir host, maintaining T. cruzi infection and potentially posing a risk to human health.

Chagas Disease in the United States: a Public Health Approach

Trypanosoma cruzi is the etiological agent of Chagas disease, usually transmitted by triatomine vectors. An estimated 20 to 30% of infected individuals develop potentially lethal cardiac or gastrointestinal disease. Sylvatic transmission cycles exist in the southern United States, involving 11 triatomine vector species and infected mammals such as rodents, opossums, and dogs. Nevertheless, imported chronic T. cruzi infections in migrants from Latin America vastly outnumber locally acquired human cases. Benznidazole is now FDA approved, and clinical and public health efforts are under way by researchers and health departments in a number of states. Making progress will require efforts to improve awareness among providers and patients, data on diagnostic test performance and expanded availability of confirmatory testing, and evidence-based strategies to improve access to appropriate management of Chagas disease in the United States.

Evidence of Likely Autochthonous Transmission of Chagas Disease in Arizona

A healthy 16-year-old girl born and raised in Tucson, AZ, had screening and confirmatory testing revealing Chagas disease; clinical evaluation established that she had the indeterminate form of chronic Chagas disease with evidence of likely autochthonous transmission. Trypanosoma cruzi DNA was detected by conventional polymerase chain reaction in Triatoma rubida captured at her home.

Protein mass spectrometry detects multiple bloodmeals for enhanced Chagas disease vector ecology

Chagas disease, a neglected tropical disease endemic in Latin America, is caused by the protozoan parasite Trypanosoma cruzi and is responsible for significant health impacts, especially in rural communities. The parasite is transmitted by insect vectors in the Triatominae subfamily and due to lack of vaccines and limited treatment options, vector control is the main way of controlling the disease. Knowing what vectors are feeding on directly enhances our understanding of the ecology and biology of the different vector species and can potentially aid in engaging communities in active disease control, a concept known as Ecohealth management. We evaluated bloodmeals in rural community, house-caught insect vectors previously evaluated for bloodmeals via DNA analysis as part of a larger collaborative project from three countries in Central America, including Guatemala. In addition to identifying bloodmeals in 100% of all samples using liquid chromatography tandem mass spectrometry (LC-MS/MS) (n = 50), strikingly for 53% of these samples there was no evidence of a recent bloodmeal by DNA-PCR. As individual vectors often feed on multiple sources, we developed an enhanced detection pipeline, and showed the ability to quantify a bloodmeal using stable-isotope-containing synthetic references peptides, a first step in further exploration of species-specific bloodmeal composition. Furthermore, we show that a lower resolution mass spectrometer is sufficient to correctly identify taxa from bloodmeals, an important and strong attribute of our LC-MS/MS-based method, opening the door to using proteomics in countries where Chagas disease is endemic.

Trypanosoma cruzi diversity in naturally infected nonhuman primates in Louisiana assessed by deep sequencing of the mini-exon gene

BACKGROUND

Trypanosoma cruzi is a zoonotic pathogen of increasing relevance in the USA, with a growing number of autochthonous cases identified in recent years. The identification of parasite genotypes is key to understanding transmission cycles and their dynamics and consequently human infection. Natural T. cruzi infection is present in captive nonhuman primate colonies in the southern USA.

METHODS

We investigated T. cruzi genetic diversity through a metabarcoding and next-generation sequencing approach of the mini-exon gene to characterize the parasite genotypes circulating in nonhuman primates in southern Louisiana.

RESULTS

We confirmed the presence of T. cruzi in multiple tissues of 12 seropositive animals, including heart, liver, spleen and gut. The TcI discrete typing unit (DTU) predominated in these hosts, and specifically TcIa, but we also detected two cases of coinfections with TcVI and TcIV parasites, unambiguously confirming the circulation of TcVI in the USA. Multiple mini-exon haplotypes were identified in each host, ranging from 6 to 11.

CONCLUSIONS

The observation of multiple T. cruzi sequence haplotypes in each nonhuman primate indicates possible multiclonal infections. These data suggest the participation of these nonhuman primates in local parasite transmission cycles and highlight the value of these naturally infected animals for the study of human Chagas disease.

Identification of Triatomines and Their Habitats in a Highly Developed Urban Environment

Eleven triatomine species, the vector for Chagas disease, are endemic in the southern U.S. While traditionally thought to only occur in rural habitats and sylvatic transmission cycles, recent studies provide compounding evidence that triatomines could exist in urban habitats and domestic transmission cycles in Texas. We conducted a study of active and passive surveillance techniques over 3 years (2016-2018) in the City of Houston, Harris County, Texas to determine the presence of triatomines in this metroplex. Active surveillance methods uncovered Triatoma sanguisuga nymphs from two locations in downtown Houston city parks. We also documented the first Trypanosoma cruzi positive kissing bug collected in an urban environment of Harris County, Texas. Our findings provide evidence that triatomines can be found in heavily populated U.S. urban environments, and warrant public health support for expanded triatomine and Chagas disease surveillance in city settings.

Toward an Ecological Framework for Assessing Reservoirs of Vector-Borne Pathogens: Wildlife Reservoirs of Trypanosoma cruzi across the Southern United States

Wildlife species are critical for both feeding vectors and serving as reservoirs of zoonotic vector-borne pathogens. Transmission pathways leading to disease in humans or other target taxa might be better understood and managed given a complete understanding of the relative importance of different reservoir species in nature. Using the conceptual framework of “reservoir potential,” which considers elements of both reservoir competence and vector-host contact, we review the wildlife reservoirs of Trypanosoma cruzi in the southern United States, where many species of triatomine vectors occur and wildlife maintain enzootic cycles that create a risk of spillover to humans, domestic dogs, and captive nonhuman primates that may develop Chagas disease. We reviewed 77 published reports of T. cruzi infection in at least 26 wildlife species across 15 southern states. Among the most well-studied and highly infected reservoirs are raccoon (Procyon lotor), woodrat (Neotoma spp.), and opossum (Didelphis virginiana), with aggregate overall infection prevalences of 36.4, 34.7, and 22.9%, respectively. Just over 60% of studies utilized methods from which an infectiousness index could be generated and show that raccoons and striped skunk (Mephitis mephitis) are among the most infectious wildlife hosts. Triatomine-host contact has sparsely been quantified in the southern United States, but 18 of the 24 host species previously identified to have been fed upon by triatomines are wildlife. Future studies to parameterize the reservoir potential model, especially to quantify wildlife infectiousness, vector-host contact, and the epidemiological importance of parasite strains maintained by wildlife, could open new doors for managing enzootic cycles and reducing T. cruzi spillover risk.

Identification and characterization of the causative triatomine bugs of anaphylactic shock in Zhanjiang, China

Background

Two health concerns primarily related to triatomine bugs are transmission of Trypanosoma cruzi through infective feces, and allergic reactions induced by triatomine bites. In the Southwestern United States, reduviid bugs bites commonly cause insect allergy. In South China, four cases of anaphylactic shock have been reported after this bite exposure. To further classify the species of these bugs and confirm the sensitization of the triatomine saliva, we caught triatomine bugs from the region where the bites occurred and performed phylogenetic and immunohistochemical (IHC) analysis.

Methods

Triatomine bugs were collected in Donghai Island of Zhanjiang City in South China. The genomic DNA was extracted from three legs of the bugs. The fragments of mitochondrial 16S rRNA, cytochrome c oxidase subunit I (COI) gene and nuclear ribosomal 18S and 28S rRNA genes were obtained by PCR and sequenced. A phylogenetic tree was constructed based on the sequence of 16S rRNA gene using a maximum likelihood method with MEGA 7.0 software. Trypanosomal specific fragments and vertebrate COI genes were amplified from the fecal DNA to detect the infection of trypanosomes and analyze the blood feeding patterns, respectively. Paraffin-embedded sections were then prepared from adult triatomines and sent for IHC staining.

Results

We collected two adult triatomine bugs in Donghai Island. Morphological and molecular analyses indicated that the triatomines were Triatoma rubrofasciata. No fragments of T. cruzi or other trypanosomes were detected from the fecal DNA. Mitochondrial gene segments of Homo sapiens and Mus musculus were successfully amplified. The allergens which induced specific IgE antibodies in human serum were localized in the triatomine saliva by IHC assay.

Conclusions

The two triatomine bugs from Donghai Island were T. rubrofasciata. They had bitten humans and mice. Their saliva should contain the allergens related to the allergic symptoms and even anaphylactic shock of exposed residents. Great consideration should be given to this triatomine bugs due to their considerable distribution and potential threat to public health in South China.

Parasitic interactions among Trypanosoma cruzi, triatomine vectors, domestic animals, and wildlife in Big Bend National Park along the Texas-Mexico border

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.

Detailed ecological associations of triatomines revealed by metabarcoding and next-generation sequencing: implications for triatomine behavior and Trypanosoma cruzi transmission cycles

Trypanosoma cruzi is the agent of Chagas disease, transmitted by hematophagous triatomine vectors. Establishing transmission cycles is key to understand the epidemiology of the disease, but integrative assessments of ecological interactions shaping parasite transmission are still limited. Current approaches also lack sensitivity to assess the full extent of this ecological diversity. Here we developed a metabarcoding approach based on next-generation sequencing to identify triatomine gut microbiome, vertebrate feeding hosts, and parasite diversity and their potential interactions. We detected a dynamic microbiome in Triatoma dimidiata, including 23 bacterial orders, which differed according to blood sources. Fourteen vertebrate species served as blood sources, corresponding to domestic, synantropic and sylvatic species, although four (human, dog, cow and mice) accounted for over 50% of blood sources. Importantly, bugs fed on multiple hosts, with up to 11 hosts identified per bug, indicating very frequent host-switching. A high clonal diversity of T. cruzi was detected, with up to 20 haplotypes per bug. This analysis provided much greater sensitivity to detect multiple blood meals and multiclonal infections with T. cruzi, which should be taken into account to develop transmission networks, and characterize the risk for human infection, eventually leading to a better control of disease transmission.

Clair RM, Vincent JJ, Monroy MC, Stevens L. Chagas disease vector blood meal sources identified by protein mass spectrometry

Chagas disease is a complex vector borne parasitic disease involving blood feeding Triatominae (Hemiptera: Reduviidae) insects, also known as kissing bugs, and the vertebrates they feed on. This disease has tremendous impacts on millions of people and is a global health problem. The etiological agent of Chagas disease, Trypanosoma cruzi (Kinetoplastea: Trypanosomatida: Trypanosomatidae), is deposited on the mammalian host in the insect’s feces during a blood meal, and enters the host’s blood stream through mucous membranes or a break in the skin. Identifying the blood meal sources of triatomine vectors is critical in understanding Chagas disease transmission dynamics, can lead to identification of other vertebrates important in the transmission cycle, and aids management decisions. The latter is particularly important as there is little in the way of effective therapeutics for Chagas disease. Several techniques, mostly DNA-based, are available for blood meal identification. However, further methods are needed, particularly when sample conditions lead to low-quality DNA or to assess the risk of human cross-contamination. We demonstrate a proteomics-based approach, using liquid chromatography tandem mass spectrometry (LC-MS/MS) to identify host-specific hemoglobin peptides for blood meal identification in mouse blood control samples and apply LC-MS/MS for the first time to Triatoma dimidiata insect vectors, tracing blood sources to species. In contrast to most proteins, hemoglobin, stabilized by iron, is incredibly stable even being preserved through geologic time. We compared blood stored with and without an anticoagulant and examined field-collected insect specimens stored in suboptimal conditions such as at room temperature for long periods of time. To our knowledge, this is the first study using LC-MS/MS on field-collected arthropod disease vectors to identify blood meal composition, and where blood meal identification was confirmed with more traditional DNA-based methods. We also demonstrate the potential of synthetic peptide standards to estimate relative amounts of hemoglobin acquired when insects feed on multiple blood sources. These LC-MS/MS methods can contribute to developing Ecohealth control strategies for Chagas disease transmission and can be applied to other arthropod disease vectors.

Prevalence and Seroprevalence of Trypanosoma cruzi Infection in a Military Population in Texas

Recent biosurveillance findings at Joint Base San Antonio (JBSA), a large military installation located in south-central Texas, indicate the potential for vector-borne human Chagas disease. A cross-sectional study was conducted to determine the prevalence and seroprevalence of Trypanosoma cruzi infection in highest risk subpopulations on the installation, including students and instructors who work and sleep in triatomine-endemic field settings. Real-time polymerase chain reaction, enzyme-linked immunosorbent assay, and indirect immunofluorescent antibody assay were performed on enrolled subjects (N = 1,033), none of whom tested positive for T. cruzi or anti-T. cruzi antibodies. Current countermeasures used during field training on JBSA appear to be sufficient for preventing autochthonous human Chagas disease.

Molecular identification and genotyping of Trypanosoma cruzi DNA in autochthonous Chagas disease patients from Texas, USA

The parasitic protozoan Trypanosoma cruzi, the causative agent of Chagas disease, is widely distributed throughout the Americas, from the southern United States (US) to northern Argentina, and infects at least 6 million people in endemic areas. Much remains unknown about the dynamics of T. cruzi transmission among mammals and triatomine vectors in sylvatic and peridomestic eco-epidemiological cycles, as well as of the risk of transmission to humans in the US. Identification of T. cruzi DTUs among locally-acquired cases is necessary for enhancing our diagnostic and clinical prognostic capacities, as well as to understand parasite transmission cycles. Blood samples from a cohort of 15 confirmed locally-acquired Chagas disease patients from Texas were used for genotyping T. cruzi. Conventional PCR using primers specific for the minicircle variable region of the kinetoplastid DNA (kDNA) and the highly repetitive genomic satellite DNA (satDNA) confirmed the presence of T. cruzi in 12/15 patients. Genotyping was based on the amplification of the intergenic region of the miniexon gene of T. cruzi and sequencing. Sequences were analyzed by BLAST and phylogenetic analysis by Maximum Likelihood method allowed the identification of non-TcI DTUs infection in six patients, which corresponded to DTUs TcII, TcV or TcVI, but not to TcIII or TcIV. Two of these six patients were also infected with a TcI DTU, indicating mixed infections in those individuals. Electrocardiographic abnormalities were seen among patients with single non-TcI and mixed infections of non-TcI and TcI DTUs. Our results indicate a greater diversity of T. cruzi DTUs circulating among autochthonous human Chagas disease cases in the southern US, including for the first time DTUs from the TcII-TcV-TcVI group. Furthermore, the DTUs infecting human patients in the US are capable of causing Chagasic cardiac disease, highlighting the importance of parasite detection in the population.

Trypanosoma cruzi Infection Prevalence and Bloodmeal Analysis in Triatomine Vectors of Chagas Disease From Rural Peridomestic Locations in Texas, 2013-2014

Protozoan pathogen Trypanosoma cruzi (Chagas, 1909) is the etiologic agent of Chagas disease, which affects millions of people in Latin America. Recently, the disease has been gaining attention in Texas and the southern United States. Transmission cycle of the parasite involves alternating infection between insect vectors and vertebrate hosts (including humans, wildlife, and domestic animals). To evaluate vector T. cruzi parasite burden and feeding patterns, we tested triatomine vectors from 23 central, southern, and northeastern counties of Texas. Out of the 68 submitted specimens, the majority were genetically identified as Triatoma gerstaeckeri (Stal, 1859), with a few samples of Triatoma sanguisuga (LeConte, 1855), Triatoma lecticularia (Stal, 1859), Triatoma rubida (Uhler, 1894), and Triatoma protracta woodi (Usinger, 1939). We found almost two-thirds of the submitted insects were polymerase chain reaction-positive for T. cruzi Bloodmeal sources were determined for most of the insects, and 16 different species of mammals were identified as hosts. The most prevalent type of bloodmeal was human, with over half of these insects found to be positive for T. cruzi High infection rate of the triatomine vectors combined with high incidence of feeding on humans highlight the importance of Chagas disease surveillance in Texas. With our previous findings of autochthonous transmission of Chagas disease, urgent measures are needed to increase public awareness, vector control in and around homes, and Chagas screening of residents who present with a history of a triatomine exposure.

Triatominae (Hemiptera, Reduviidae) in the Pantanal region: association with Trypanosoma cruzi, different habitats and vertebrate hosts

INTRODUCTION

The transmission cycle of Trypanosoma cruzi in the Brazilian Pantanal region has been studied during the last decade. Although considerable knowledge is available regarding the mammalian hosts infected by T. cruzi in this wetland, no studies have investigated its vectors in this region. This study aimed to investigate the presence of sylvatic triatomine species in different habitats of the Brazilian Pantanal region and to correlate their presence with the occurrences of vertebrate hosts and T. cruzi infection.

METHODS

The fieldwork involved passive search by using light traps and Noireau traps and active search by visual inspection. The light traps were placed at five selected points along forested areas for seven nights during each of the nine excursions. At each point where a light trap was set, eight Noireau traps were placed in palm trees and bromeliads.

RESULTS

In all, 88 triatomine bugs were collected: two and one individuals from light traps and Noireau traps, respectively; three from peridomestic areas; 23 in coati nests; and 59 in thornbird nests. In this study, active search in microhabitats showed higher efficiency than passive search, since 95% of the triatomine bugs were caught in nests. Further, triatomine bugs were only found to be infected by T. cruzi in coati nests.

CONCLUSIONS

Coati nests might act as a point of convergence and dispersion for triatomine bugs and mammal hosts infected by T. cruzi, thereby playing an important role in the sylvatic cycle of T. cruziin the Pantanal region.

Molecular Diversity of Trypanosoma cruzi Detected in the Vector Triatoma protracta from California, USA

BACKGROUND

Trypanosoma cruzi, causative agent of Chagas disease in humans and dogs, is a vector-borne zoonotic protozoan parasite that can cause fatal cardiac disease. While recognized as the most economically important parasitic infection in Latin America, the incidence of Chagas disease in the United States of America (US) may be underreported and even increasing. The extensive genetic diversity of T. cruzi in Latin America is well-documented and likely influences disease progression, severity and treatment efficacy; however, little is known regarding T. cruzi strains endemic to the US. It is therefore important to expand our knowledge on US T. cruzi strains, to improve upon the recognition of and response to locally acquired infections.

METHODOLOGY/PRINCIPLE FINDINGS

We conducted a study of T. cruzi molecular diversity in California, augmenting sparse genetic data from southern California and for the first time investigating genetic sequences from northern California. The vector Triatoma protracta was collected from southern (Escondido and Los Angeles) and northern (Vallecito) California regions. Samples were initially screened via sensitive nuclear repetitive DNA and kinetoplast minicircle DNA PCR assays, yielding an overall prevalence of approximately 28% and 55% for southern and northern California regions, respectively. Positive samples were further processed to identify discrete typing units (DTUs), revealing both TcI and TcIV lineages in southern California, but only TcI in northern California. Phylogenetic analyses (targeting COII-ND1, TR and RB19 genes) were performed on a subset of positive samples to compare Californian T. cruzi samples to strains from other US regions and Latin America. Results indicated that within the TcI DTU, California sequences were similar to those from the southeastern US, as well as to several isolates from Latin America responsible for causing Chagas disease in humans.

CONCLUSIONS/SIGNIFICANCE

Triatoma protracta populations in California are frequently infected with T. cruzi. Our data extend the northern limits of the range of TcI and identify a novel genetic exchange event between TcI and TcIV. High similarity between sequences from California and specific Latin American strains indicates US strains may be equally capable of causing human disease. Additional genetic characterization of Californian and other US T. cruzi strains is recommended.

Historical Perspectives on the Epidemiology of Human Chagas Disease in Texas and Recommendations for Enhanced Understanding of Clinical Chagas Disease in the Southern United States

Chagas disease (Trypanosoma cruzi infection) has recently been identified as an important neglected tropical disease in the United States. Anecdotally referred to as a "silent killer," it leads to the development of potentially fatal cardiac disease in approximately 30% of those infected. In an attempt to better understand the potential of Chagas disease as a significant underlying cause of morbidity in Texas, we performed a historical literature review to assess disease burden. Human reports of triatomine bites and disease exposure were found to be prevalent in Texas. Despite current beliefs that Chagas disease is a recently emerging disease, we report historical references dating as far back as 1935. Both imported cases and autochthonous transmission contribute to the historical disease burden in Texas. We end by discussing the current knowledge gaps, and recommend priorities for advancing further epidemiologic studies and their policy implications.

Triatoma sanguisuga blood meals and potential for Chagas disease, Louisiana, USA

To evaluate human risk for Chagas disease, we molecularly identified blood meal sources and prevalence of Trypanosoma cruzi infection among 49 Triatoma sanguisuga kissing bugs in Louisiana, USA. Humans accounted for the second most frequent blood source. Of the bugs that fed on humans, ≈40% were infected with T. cruzi, revealing transmission potential.

Sources of blood meals of sylvatic Triatoma guasayana near Zurima, Bolivia, assayed with qPCR and 12S cloning

Background

In this study we compared the utility of two molecular biology techniques, cloning of the mitochondrial 12S ribosomal RNA gene and hydrolysis probe-based qPCR, to identify blood meal sources of sylvatic Chagas disease insect vectors collected with live-bait mouse traps (also known as Noireau traps). Fourteen T. guasayana were collected from six georeferenced trap locations in the Andean highlands of the department of Chuquisaca, Bolivia.

Methodology/Principal Findings

We detected four blood meals sources with the cloning assay: seven samples were positive for human (Homo sapiens), five for chicken (Gallus gallus) and unicolored blackbird (Agelasticus cyanopus), and one for opossum (Monodelphis domestica). Using the qPCR assay we detected chicken (13 vectors), and human (14 vectors) blood meals as well as an additional blood meal source, Canis sp. (4 vectors).

Conclusions/Significance

We show that cloning of 12S PCR products, which avoids bias associated with developing primers based on a priori knowledge, detected blood meal sources not previously considered and that species-specific qPCR is more sensitive. All samples identified as positive for a specific blood meal source by the cloning assay were also positive by qPCR. However, not all samples positive by qPCR were positive by cloning. We show the power of combining the cloning assay with the highly sensitive hydrolysis probe-based qPCR assay provides a more complete picture of blood meal sources for insect disease vectors.

The World Health Organization (WHO) estimates that 7 to 8 million people are currently infected with Trypanosoma cruzi, the parasite that causes Chagas disease. The WHO recommends insect vector control as the primary prevention method; and insecticide spraying is the most commonly used intervention technique. Sylvatic insect vectors are a special concern because they are a source of reinfestation after insecticides have been applied to living quarters (domestic) and immediate surroundings (peridomestic). To better understand sylvatic insect vector movement, we used two molecular biology techniques to detect the blood meal sources of sylvatic insect vectors. The first technique, cloning of 12S PCR products, allows us to cast a wide net and detect blood meal sources with no previous knowledge of vertebrates or mammals in the study site. After acquiring knowledge of vertebrates in the study site (either through the aforementioned cloning technique, literature review or survey of the area), the second technique, the species-specific hydrolysis probe-based qPCR provides a highly sensitive assay for particular taxa.

Towards a phylogenetic approach to the composition of species complexes in the North and Central American Triatoma, vectors of Chagas disease

Phylogenetic relationships of insect vectors of parasitic diseases are important for understanding the evolution of epidemiologically relevant traits, and may be useful in vector control. The sub-family Triatominae (Hemiptera:Reduviidae) includes ∼140 extant species arranged in five tribes comprised of 15 genera. The genus Triatoma is the most species-rich and contains important vectors of Trypanosoma cruzi, the causative agent of Chagas disease. Triatoma species were grouped into complexes originally by morphology and more recently with the addition of information from molecular phylogenetics (the four-complex hypothesis); however, without a strict adherence to monophyly. To date, the validity of proposed species complexes has not been tested by statistical tests of topology. The goal of this study was to clarify the systematics of 19 Triatoma species from North and Central America. We inferred their evolutionary relatedness using two independent data sets: the complete nuclear internal transcribed spacer-2 ribosomal DNA (ITS-2 rDNA) and head morphometrics. In addition, we used the Shimodaira-Hasegawa statistical test of topology to assess the fit of the data to a set of competing systematic hypotheses (topologies). An unconstrained topology inferred from the ITS-2 data was compared to topologies constrained based on the four-complex hypothesis or one inferred from our morphometry results. The unconstrained topology represents a statistically significant better fit of the molecular data than either the four-complex or the morphometric topology. We propose an update to the composition of species complexes in the North and Central American Triatoma, based on a phylogeny inferred from ITS-2 as a first step towards updating the phylogeny of the complexes based on monophyly and statistical tests of topologies.

Kissing bugs in the United States: risk for vector-borne disease in humans

Eleven species of kissing bugs are found in the United States. Their home ranges may be expanding northward, perhaps as a consequence of climate change. At least eight of the species, perhaps all, are reported to harbor Trypanosoma cruzi, the parasite that causes Chagas disease. Because humans are encroaching on kissing bug habitat, there is concern for vector-transmitted Chagas disease in the United States. To date, documented autochthonous cases of Chagas in humans in the United States are rare. Kissing bugs are capable of adapting to new habitats such as human domiciles; however, they do not colonize homes in the United States as in Central and South America. We review the biology, behavior, and medical importance of kissing bugs and the risk they pose for transmission of Chagas disease in the United States. Where possible, descriptions of US species are compared to the epidemiologically important Latin American species.