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

Climate change and Trypanosoma cruzi transmission in North and central America

Trypanosoma cruzi is a protozoan parasite that causes Chagas disease in humans. Transmission of T cruzi by triatomine vectors is dependent on diverse environmental and socioeconomic factors. Climate change, which is disrupting patterns of human habitation and land use, can affect the epidemiology of Chagas disease by influencing the distribution of vector and host species. We conducted a review using triatomine distribution as a proxy for T cruzi transmission in North America (Canada, Mexico, and the USA) and central America (Belize, Costa Rica, El Salvador, Guatemala, Honduras, Nicaragua, and Panama) and investigated the association of T cruzi transmission with climate change, identifying 12 relevant studies. Most studies (n=9) modelled the effect of the scenario of climate change on the distribution of relevant vector species and found that global warming could sometimes favour and sometimes hinder triatomine distribution. There is a need for more research in parasite biology and social sciences to further understand how climate change and socioeconomic factors can affect the epidemiology of this neglected tropical disease.

Development of an operational trap for collection, killing, and preservation of triatomines (Hemiptera: Reduviidae): the kissing bug kill trap

Surveillance of triatomines or kissing bugs (Hemiptera: Reduviidae: Triatominae), the insect vectors of Trypanosoma cruzi, a Chagas disease agent, is hindered by the lack of an effective trap. To develop a kissing bug trap, we made iterative improvements over 3 years on a basic design resulting in 7 trap prototypes deployed across field sites in Texas, United States and Northern Mexico, yielding the capture of 325 triatomines of 4 species (Triatoma gerstaeckeri [Stål], T. sanguisuga [LeConte], T. neotomae [Neiva], and T. rubida [Uhler]). We began in 2019 with vertical transparent tarpaulin panel traps illuminated with artificial light powered by AC current, which were successful in autonomous trapping of flying triatomines, but were expensive, labor-intensive, and fragile. In 2020, we switched to white LED lights powered by a solar cell. We tested a scaled-down version of the vertical panel traps, a commercial cross-vane trap, and a multiple-funnel trap. The multiple-funnel traps captured 2.6× more kissing bugs per trap-day than cross-vane traps and approached the performance of the vertical panel traps in number of triatomines captured, number of triatomines per trap-day and triatomines per arthropod bycatch. Multiple-funnel traps required the least labor, were more durable, and had the highest triatomines per day per cost. Propylene glycol in the collection cups effectively preserved captured triatomines allowing for molecular detection of T. cruzi. The trapping experiments established dispersal patterns for the captured species. We conclude that multiple-funnel traps with solar-powered LED lights should be considered for adoption as surveillance and potentially mass-trapping management tools for triatomines.

Predictor Variables in the Spread of Chagas Disease in Rural Areas

Over a hundred years ago after the discovery of Chagas disease (CD) in Brazil, the World Health Organization estimates a number of 6 to 7 million people infected by Trypanosoma cruzi worldwide. Therefore, the goal of this work was to identify variables related to the spread of infection by T. cruzi in humans living in rural areas, seeking predictor variables. A systematic review of the literature has been conducted, with a search in the Scopus platform, using the search string "Chagas disease" and "rural", resulting in 85 valid and analyzed scientific studies (1977 and 2022). Twenty-seven predictor variables have been acquired, and 19 of them have been grouped, such as: socioeconomic and educational, housing, environmental, sanitary, and cultural; and 8 variables related to T. cruzi seropositive individuals. The predictor variables yielded significant results (p-value < 0.05) in 59.5% of the cases (195/328), with a median of 66.7%. In other words, studies relating to 50% of the 27 variables showed significance equal to or greater than 66.7% of the time. The independent variables with the highest proportion of significant data (p-value < 0.05) were Education (87.6%), Intradomicile building (70%), Domestic animals (69.6%), and Triatomines (69.2%) in the households. Some variables reached 100%; however, few articles were found, indicating the need for further research, especially for Sanitation and Culture. It has been concluded that, in the several contexts found, the social vulnerability and lack of information led the individual to living in environments where inhabitability is inadequate, to perform limited work activity and develop habits and behaviors which impair them in an environmental insalubrity situation, favorable to the access of vectors and pathogens of anthropozoonoses such as CD.

First Report of Chagas Disease Vector Species Triatoma sanguisuga (Hemiptera: Reduviidae) Infected with Trypanosoma cruzi in Delaware

In July and October 2023, two live triatomine bugs were found inside a home in New Castle County, Delaware. The bugs were identified as Triatoma sanguisuga, the most widespread triatomine bug species in the United States. Triatoma sanguisuga is a competent vector of Trypanosoma cruzi, the causative agent of Chagas disease. The two specimens were tested via real-time PCR (qPCR) for infection with T. cruzi, and one of the specimens was positive. Despite T. sanguisuga being endemic to the area, attainment of accurate species identification and T. cruzi testing of the bugs required multiple calls to federal, state, private, and academic institutions over several months. This constitutes the first report of T. sanguisuga infected with T. cruzi in Delaware. In addition, this is the first published report of T. sanguisuga in New Castle County, the northernmost and most densely populated county in Delaware. New Castle County still conforms to the described geographic range of T. sanguisuga, which spans from Texas to the East Coast of the United States. The T. cruzi infection prevalence of the species has not been studied in the northeastern United States, but collections in southern states have found prevalences as high as 60%. The Delaware homeowner's lengthy pursuit of accurate information about the vector highlights the need for more research on this important disease vector in Delaware.

Interesting case from Argentina: Kidney transplant recipient with skin lesions-A Latin American perspective

This is a case of a kidney transplant recipient who presented with skin lesions, low-grade fevers, and pancytopenia 2 months after his transplant.

Highlights, challenges, and perspectives in basic and applied chemical ecology of triatomines

Triatomines are vectors of Chagas disease. Due to failures in their control, there is an urgent need for more efficient and environmentally friendly monitoring and control tools. These hematophagous insects rely heavily on chemical information from the environment to detect hosts and cues/signals from conspecifics. Chemical ecology includes the elucidation of the functional role of chemicals mediating interactions between organisms. Studies on the chemical ecology of triatomines are leading to novel methods for their monitor and control. Thus, laboratory tests to develop chemical attractants and repellents are promissory and have led to the design of, for example, efficient baited traps. However, the monitoring and control tools proposed until now have not been as effective in the field.

Two sticky traps baited with synthetic host odors to capture Triatoma infestans, an important vector of Chagas disease

Chagas disease is a vector-borne disease caused by Trypanosoma cruzi, which is transmitted by triatomine insects. Triatoma infestans is one of the main vectors. Efforts to eliminate T. infestans have often failed in the Gran Chaco, the largest endemic area of this species. Known methods for assessing triatomine house infestation include timed-manual collections by skilled personnel, bug notifications by householders' and/or non-baited detection devices. However, the detection sensitivity of those methods needs to be improved, especially when the bugs are present at low densities. In this work we design and evaluate the performance of two types of sticky traps (pitfall and climbing traps), when baited with a synthetic host odor lure, to capture T. infestans nymphs within an experimental box under semi-controlled laboratory conditions. Nine assays were conducted for each type of trap using a different experimental box per type of trap design and per treatment. These treatments were: test (T, trap baited with the synthetic lure), positive control (C+, trap baited with a mouse) and negative control (C-, empty trap). One hundred percent of the sticky pitfall and 89% of the climbing traps baited with the synthetic lure captured at least one insect. Moreover, the sticky pitfall trap and the sticky climbing trap, both baited with the synthetic lure, captured 30% and 40% of the insects in a single night, respectively. In both cases, the trap with the synthetic lure captured significantly more insects than the non-baited trap. However, the synthetic lure could be improved, as the traps with this lure captured significantly less insects than the traps with a live host. In summary, the two types of synthetically-baited traps tested were able to capture T. infestans nymphs, indicating that both designs are effective under the laboratory experimental conditions and insect abundance used in this work. These traps deserve to be tested in a field setting.

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.

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.

Urban vectors of Chagas disease in the American continent: A systematic review of epidemiological surveys

BACKGROUND

Chagas is a complex and multidimensional socio-environmental health phenomenon, in which different components converge and interact. Historically, this disease was associated with insect vectors found in the rural environment. However, in the Americas, we are currently facing a new paradigm, in which different scenarios allow maintaining the vectorial transmission of the parasite through triatomine populations that either occasionally enter the dwellings or colonize urban environments.

METHODOLOGY/PRINCIPAL FINDINGS

Records of scientific reports available in the PubMed and LILACS search engines were retrieved, using three criteria according to the main triatomine genera of epidemiological importance and to the general scientific production on Chagas disease in urban contexts. Results showed that records on the occurrence of vectors in urban dwellings began to increase in the last three decades. Results also showed that the main species of triatomines collected inside dwellings (18 in total) belong mainly to the genera Triatoma and Panstrongylus, with most species (16/18, 88.8%) infected with the parasite, and that infestation of triatomine species occurs in all types of cities (small, medium and large, including megalopolises), from Argentina to the USA.

CONCLUSIONS/SIGNIFICANCE

Urban Chagas represents a new challenge that adds a different dimension to the problem of Chagas disease due to the particular characteristics of the lifestyle in urban agglomerates. The new scenario will require adaptations of the programs of control of vector to this shift from rural to urban settlements.

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.

Healthcare Workers' Knowledge about Chagas Disease: A Systematic Review

Transmission of Chagas disease (CD) has decreased in recent decades, but the disease remains an important problem in endemic areas. There was an increase in the proportion of nonvector transmission, mainly in non-endemic countries. The aim of this study was to gather evidence concerning healthcare professional's knowledge about CD. Searches were performed through Medline/PubMed, Lilacs, Web of Science databases, and Scielo archives, from which 13/97 articles were selected for a qualitative analysis after full-text reading. Most of the studies were from the United States, the oldest published in 2007 and the most recent in 2020, and most of them used surveys as the evaluation method. Each article used different methods, according to the epidemiological status of vector transmission. Two studies targeted specialty-related questions, and two used focus groups as methods for data gathering. Despite differences between the studies, all of them presented knowledge deficits among healthcare workers, regarding at least one of the evaluated aspects. In comparison with population surveys, healthcare professionals demonstrated higher results related to clinical aspects and awareness of the disease's importance. Most of the articles showed a low perception of CD's knowledge by the participants and a low probability of considering CD in the diagnosis of their patients. A previous contact with the subject was pointed by some studies as capable of improving knowledge of the participants. This study emphasizes the importance of continuing education to address deficits of healthcare professionals' knowledge.

Risk of Trypanosoma cruzi transmission in southern Minas Gerais, Brazil - Data from 2014 to 2020

Trypanosoma cruzi, the etiologic agent of Chagas disease, is widely distributed in the Americas and is transmitted through vectorial, transfusional, and oral routes. This study aimed to evaluate the risk of vectorial transmission of Chagas disease in municipalities located in southern Minas Gerais, Brazil, by analyzing triatomine specimens collected from 2014 to 2020. All 1522 hematophagous triatomines were identified as Panstrongylus megistus, and were subjected to parasitological and molecular examinations. From 2014 to 2016, approximately 10% of insects were positive in the microscopic analysis of intestinal content, and 27% were positive as detected by the quantitative polymerase chain reaction (qPCR) of the same sampling. However, in the last investigated years, an increase in infected triatomines was observed in microscopic analysis (22%) and qPCR methods (41%). This corroborates the findings of acute human Chagas disease cases, which have increased in the study area from a maximum of 2 cases in previous years to 20 cases in 2019, and 17 cases in 2020 through June. Additionally, bloodmeal sources of infected triatomines were investigated; human blood was detected in up to 85.7% of the samples. Moreover, canine blood was also detected in triatomine intestinal content in recent years, reaching 91% of analyzed insects in 2018. Data on bloodmeal sources have demonstrated human-vector contact and have suggested the participation of dogs in the parasite transmission cycle. These results indicate the risk of T. cruzi vectorial transmission in Southern Minas Gerais and São Paulo owing to the boundary between these states. Thus, enhanced surveillance and vector control of Chagas disease are highly recommended in these areas.

In the heart of the city: Trypanosoma cruzi infection prevalence in rodents across New Orleans

BACKGROUND

Trypanosoma cruzi - the causative agent of Chagas disease - is known to circulate in commensal pests, but its occurrence in urban environments is not well understood. We addressed this deficit by determining the distribution and prevalence of T. cruzi infection in urban populations of commensal and wild rodents across New Orleans (Louisiana, USA). We assessed whether T. cruzi prevalence varies according to host species identity and species co-occurrences, and whether T. cruzi prevalence varies across mosaics of abandonment that shape urban rodent demography and assemblage structure in the city.

METHODS

Leveraging city-wide population and assemblage surveys, we tested 1428 rodents comprising 5 species (cotton rats, house mice, Norway rats, rice rats and roof rats) captured at 98 trapping sites in 11 study areas across New Orleans including nine residential neighborhoods and a natural area in Orleans Parish and a neighborhood in St. Bernard Parish. We also assayed Norway rats at one site in Baton Rouge (Louisiana, USA). We used chi-square tests to determine whether infection prevalence differed among host species, among study areas, and among trapping sites according to the number of host species present. We used generalized linear mixed models to identify predictors of T. cruzi infection for all rodents and each host species, respectively.

RESULTS

We detected T. cruzi in all host species in all study areas in New Orleans, but not in Baton Rouge. Though overall infection prevalence was 11%, it varied by study area and trapping site. There was no difference in prevalence by species, but roof rats exhibited the broadest geographical distribution of infection across the city. Infected rodents were trapped in densely populated neighborhoods like the French Quarter. Infection prevalence seasonally varied with abandonment, increasing with greater abandonment during the summer and declining with greater abandonment during the winter.

CONCLUSIONS

Our findings illustrate that T. cruzi can be widespread in urban landscapes, suggesting that transmission and disease risk is greater than is currently recognized. Our findings also suggest that there is disproportionate risk of transmission in historically underserved communities, which could reinforce long-standing socioecological disparities in New Orleans and elsewhere.

Low Trypanosoma cruzi transmission risk to humans in the Trans-Pecos region of Texas

In the Trans-Pecos region of Texas, reports of domestic triatomine bites were common (67%), with 36% of residentially collected triatomines positive for Trypanosoma cruzi. Despite the transmission potential, no human infections were detected. Collected Triatoma rubida species were themselves frequently parasitized with mites.

Taxonomic integrative and phylogenetic identification of the first recorded Triatoma rubrofasciata in Zhangzhou, Fujian Province and Maoming, Guangdong Province, China

BACKGROUND

Most species of Triatominae live exclusively in Latin America. However, one species, Triatoma rubrofasciata, has been recorded in the Americas as well as in various port areas in Africa and Asia. An increasing number of T. rubrofasciata have been reported in southern China in recent years. However, the origin of this invasive insect vector in China remains unknown, therefore, accurate identification and phylogenetic analysis of the bugs are urgently needed.

METHODS

A total of seven triatomine insect specimens were found and collected from Maoming City, Guangdong Province, China (GDMM) and Zhangzhou City, Fujian Province, China (FJZZ), respectively. The obtained insect vector specimens were observed under a dissecting microscope for morphological classification and then the genomic DNA was extracted, and the 16S ribosomal RNA (rRNA), 28S rRNA as well as cytochrome oxidase subunit I (COI) genes of the species were amplified and sequenced. Subsequently, molecular phylogenetic analyses based on multiple alignments of the above genes were conducted in order to identify the species and determine the phylogenetic origin approximation accurately.

RESULTS

The triatomine insects collected from GDMM and FJZZ were identified as Triatoma rubrofasciata using morphological and genetic analyses. All of the Chinese T. rubrofasciata captured in FJZZ, GDMM and other localities in southern China, together with a Vietnamese and Brazilian strain, formed a new, cohesive clade. T. rubrofasciata in GDMM and FJZZ are likely derived from strains found in Vietnam or Brazil.

CONCLUSIONS

To the best of our knowledge, this is the first record of the invasive insect T. rubrofasciata, which is likely derived from strains native to Vietnam or Brazil, in both Maoming City, Guangdong Province and Zhangzhou City, Fujian Province of China. A comparison of the DNA sequences of the 16 s rRNA, 28 s rRNA and COI genes confirmed the specific identification of T. rubrofasciata, and its potential origin in China is based on the phylogenetic analyses undertaken in this study. More targeted interventions and improved entomological surveillance are urgently needed to control the spread of this haematophagous insect in China.