Trypanosoma cruzi Transmission Among Captive Nonhuman Primates, Wildlife, and Vectors

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.

Serial 'deep-sampling' PCR of fragmented DNA reveals the wide range of Trypanosoma cruzi burden among chronically infected hosts and allows accurate monitoring of parasite load following treatment

Infection with the protozoan parasite Trypanosoma cruzi is generally well-controlled by host immune responses, but appears to be rarely eliminated. The resulting persistent, low-level infection results in cumulative tissue damage with the greatest impact generally in the heart in the form of chagasic cardiomyopathy. The relative success in immune control of T. cruzi infection usually averts acute phase death but has the negative consequence that the low-level presence of T. cruzi in hosts is challenging to detect unequivocally. Thus, it is difficult to identify those who are actively infected and, as well, problematic to gauge the impact of treatment, particularly in the evaluation of the relative efficacy of new drugs. In this study we employ DNA fragmentation and high numbers of replicate PCR reaction ('deep-sampling') to extend the quantitative range of detecting T. cruzi in blood by at least 3 orders of magnitude relative to current protocols. When combined with sampling blood at multiple time points, deep sampling of fragmented DNA allowed for detection of T. cruzi in all infected hosts in multiple host species. In addition, we provide evidence for a number of characteristics not previously rigorously quantified in the population of hosts with naturally acquired T. cruzi infection, including, a > 6-log variation between chronically infected individuals in the stable parasite levels, a continuing decline in parasite load during the second and third years of infection in some hosts, and the potential for parasite load to change dramatically when health conditions change. Although requiring strict adherence to contamination-prevention protocols and significant resources, deep-sampling PCR provides an important new tool for assessing new therapies and for addressing long-standing questions in T. cruzi infection and Chagas disease.

Trypanosoma cruzi infection in American black bears (Ursus americanus): A case report in a cub from California and serologic survey for exposure in wild black bears from several states

Trypanosoma cruzi is an important cause of disease and death in humans and dogs, and although wildlife infections are common, less is known about disease manifestations. A 12-week-old male American black bear (Ursus americanus) cub with mild lethargy and anorexia presented to a wildlife rehabilitation center in Lake Tahoe, California. The cub continued to become increasingly weak and showed decreasing interest in play and other activities. The cub was anemic and had increased γ-glutamyltransferase (GGT) liver enzymes. A large number of trypanosomes were noted on a thin blood smear. Trypanosoma cruzi was isolated in culture from a subsequent blood collection. Proliferative bony lesions were noted on radiographs, but this finding was considered unrelated to the T. cruzi infection. The number of parasites observed in thin blood smears dramatically dropped over time, but it remained PCR positive until at least nine months. The cub continued to gain weight and became increasingly active. Serum samples from the cub were positive with three different serologic assays (IFA, ELISA, and ICT). The bear was not treated because of the decreasing parasitemia and the improvement in activity and appetite. Although the bear could not be released due to issues unrelated to T. cruzi, it remains healthy in a captive facility. Sequence analysis of the DHFR-TS and COII-ND1 gene sequences confirmed the bear was infected with DTC TcIV. Following the detection of this clinical case, a serologic survey was conducted to determine the prevalence of T. cruzi exposure of black bears in California, North Carolina, and Pennsylvania. Because no serologic assay has been validated for use in bears, three different assays were used. Marked differences in apparent seroprevalence range from 1% (requiring all three assays to be positive) to ∼20.7% (requiring only one assay to be positive). Black bears are naturally exposed to T. cruzi across the United States. Future studies using PCR testing of tissues or blood would be needed to better understand the prevalence of T. cruzi in wild black bears, lineages most commonly associated with infection, and if T. cruzi represents a health threat to bears.

Genetic Diversity of Trypanosoma cruzi in the United States of America: The Least Endemic Country for Chagas Disease

Chagas disease (CD), caused by Trypanosoma cruzi and endemic in Latin America, has become an emergent health problem in non-endemic countries due to human migration. The United States (US) is the non-Latin American country with the highest CD burden and cannot be considered as non-endemic, since triatomine vectors and reservoir animals have been found. Populations of T. cruzi are divided into genetic subdivisions, which are known as discrete typing units (DTUs): TcI to TcVI and TcBat. Autochthonous human T. cruzi infection in the US is sporadic, but it may change due to environmental factors affecting the geographic distribution of triatomines. We aimed to perform a literature review of the genetic diversity of T. cruzi in triatomine vectors and mammalian hosts, including human cases, in the US. The 34 analyzed studies revealed the presence of T. cruzi in 18 states, which was mainly concentrated in Texas, Louisiana and New Mexico. TcI and TcIV were the principal DTUs identified, being TcI the most genotyped (42.4%; 917/2164). This study represents a first attempt to compile the molecular epidemiology of T. cruzi in the US, which is fundamental for predicting the progression of the infection in the country and could be of great help in its future management.

DIAGNOSIS AND TREATMENT OF A NATURAL INFECTION WITH TRYPANOSOMA CRUZI (CHAGAS DISEASE) IN A SYMPTOMATIC DE BRAZZA'S MONKEY (CERCOPITHECUS NEGLECTUS) IN ALABAMA

Trypanosoma cruzi, the causative agent of Chagas disease, is a zoonotic, vector-borne, protozoan hemoflagellate with a wide host range. An 11-yr-old, captive-bred male De Brazza's monkey (Cercopithecus neglecus) presented with weight loss despite normal appetite. Examination revealed hypoglycemia, nonregenerative anemia, and many trypanosomes on a blood smear. A whole blood sample was PCR-positive for T. cruzi discrete typing unit TcIV and the monkey seroconverted using two different methods. The monkey was treated with the standard human dose of benznidazole twice daily for 60 d; however, blood obtained over the next 1.5 yr posttreatment remained PCR-positive for T. cruzi. A second course of benznidazole at a higher dose but lower frequency for 26 wk was required for the monkey to convert to sustained PCR-negative status. The monkey recovered with no apparent lasting effects.

TRYPANOSOMA CRUZI INFECTION IN THREE SLENDER-TAILED MEERKATS (SURICATA SURICATTA)

Trypanosoma cruzi is a protozoan parasite primarily transmitted by triatomine insects (Hemiptera: subfamily Reduviidae) and is the cause of Chagas disease (CD). This report describes three cases of CD in a mob of five slender-tailed meerkats (Suricata suricatta) living in an outdoor exhibit at one zoological institution in Texas. The index case was a 9.5-yr-old female that presented with ataxia, lethargy, and pleural effusion. This case was diagnosed with CD postmortem via cytology, T. cruzi PCR of whole blood and lung fluid, and histology. Blood was opportunistically collected from the remaining four meerkats 28 d after the death of the index case and tested by PCR and serology. The second case was a clinically normal 7.5-yr-old male that tested PCR and antibody positive and the third case was a clinically normal 9-yr-old female that tested PCR positive. The second animal presented depressed, with pneumonia, and with continuous shivering 53 d after blood collection, and clinically improved after treatment with antibiotics and supportive care. Fifteen days later, the animal was found minimally responsive and died shortly thereafter. Histologic examination revealed Trypanosoma sp. amastigotes in the myocardium and the tissue was positive for T. cruzi DNA. The third meerkat, which received two separate courses of benznidazole over a span of almost 2 yr, was monitored routinely by PCR and serology and appeared clinically normal until found dead on exhibit 93 d after completion of the second treatment. Myocardium was positive for T. cruzi DNA. To the authors' knowledge, this case series is the first to document Chagas disease in meerkats and features associated cytologic and histologic findings.

Exclusion of Horizontal and Vertical Transmission as Major Sources of Trypanosoma Cruzi Infections in a Breeding Colony of Rhesus Macaques (Macaca Mulatta)

The vector-borne protozoal parasite Trypanosoma cruzi causes Chagas disease in humans and animals. This parasite is endemic to the southern United States where outdoor-housed NHP at biomedical facilities are at risk of infection. In addi- tion to the direct morbidity caused by T. cruzi, infected animals are of limited biomedical research use because infections can produce confounding pathophysiologic changes even in animals with no clinical disease. In part due to concerns for direct T. cruzi transmission between animals, infected NHP at some institutions have been culled, removed, or otherwise isolated from uninfected animal populations. However, data that document horizontal or vertical transmission in captive NHP in the United States are not available. To evaluate the potential for inter-animal transmission and to identify environmental factors that affect the distribution of new infections in NHPs, we conducted a retrospective epidemiologic study of a rhesus macaque ( Macaca mulatta ) breeding colony in south Texas. We used archived biologic samples and husbandry records to identify the time and location of macaque seroconversion. These data were used to perform a spatial analysis of how geographic location and animal associations affected the spread of disease and to infer the importance of horizontal or vertical routes of transmission. The majority of T. cruzi infections were spatially clustered, suggesting that environmental factors promoted vector exposure in various areas of the facility. Although we cannot not rule out horizontal transmission, our data suggest that horizontal transmission was not a critical route for spread for the disease. Vertical transmission was not a contributing factor in this colony. In conclusion, our findings suggest that local triatome vectors were the major source of T. cruzi infections in captive macaques in our colony. Therefore, limiting contact with vectors, rather than segregation of infected macaques, is a key strategy for disease prevention at institutions that house macaques outdoors in the southern United States.

Pathologic characteristics of infectious diseases in macaque monkeys used in biomedical and toxicologic studies

Nonhuman primates (NHPs), which have many advantages in scientific research and are often the only relevant animals to use in assessing the safety profiles and biological or pharmacological effects of drug candidates, including biologics. In scientific or developmental experiments, the immune systems of animals can be spontaneously compromised possibly due to background infection, experimental procedure-associated stress, poor physical condition, or intended or unintended mechanisms of action of test articles. Under these circumstances, background, incidental, or opportunistic infections can seriously can significantly complicate the interpretation of research results and findings and consequently affect experimental conclusions. Pathologists and toxicologists must understand the clinical manifestations and pathologic features of infectious diseases and the effects of these diseases on animal physiology and experimental results in addition to the spectrum of infectious diseases in healthy NHP colonies. This review provides an overview of the clinical and pathologic characteristics of common viral, bacterial, fungal, and parasitic infectious diseases in NHPs, especially macaque monkeys, as well as methods for definitive diagnosis of these diseases. Opportunistic infections that can occur in the laboratory setting have also been addressed in this review with examples of cases of infection disease manifestation that was observed or influenced during safety assessment studies or under experimental conditions.

Effective drug discovery in Chagas disease

The Chagas field has gone >50 years without tangible progress toward new therapies. My colleagues and I have recently reported on a benzoxaborole compound that achieves consistent parasitological cure in experimentally infected mice and in naturally infected non-human primates (NHPs). While these results do not assure success in human clinical trials, they significantly de-risk this process and form a strong justification for such trials. Highly effective drug discovery depends on a solid understanding of host and parasite biology and excellent knowledge in designing and validating chemical entities. This opinion piece seeks to provide perspectives on the process that led to the discovery of AN15368, with the hope that this will facilitate the discovery of additional clinical candidates for Chagas disease.

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.

Prevalence of Trypanosoma cruzi, the Etiologic Agent of Chagas Disease, Infection in Texas Skunks (Mammalia: Mephitidae)

Background: Chagas disease is one of the world's most neglected tropical diseases, infecting over six million people across the Americas. The hemoparasite Trypanosoma cruzi is the etiological agent for the disease, circulating in domestic, peridomestic, and sylvatic transmission cycles that are maintained by triatomine vectors and a diversity of wild and synanthropic hosts. Public health and wildlife management interventions targeting the interruption of T. cruzi transmission rely on an understanding of the dynamics driving the ecology of this zoonotic pathogen. One wildlife host that purportedly plays a role in the transmission of Chagas disease within the southern United States is the striped skunk (Mephitis mephitis), although infection prevalence in this species is poorly understood. Materials and Methods: To this end, we conducted a PCR-based surveillance of T. cruzi in 235 wild skunks, representing 4 species, across 76 counties and 10 ecoregions in Texas, United States, along with an evaluation of risk factors associated with the infection. Results: We recovered an overall T. cruzi prevalence of 17.9% for all mephitid taxa aggregated, ranging between 6.7% for plains spotted skunks (Spilogale putorius interrupta) and 42.9% for western spotted skunks (Spilogale gracilis). We report the first cases of T. cruzi infection in plains spotted and American hog-nosed skunks (Conepatus leuconotus), of important note for conservation medicine since populations of both species are declining within Texas. Although not statistically significant, we also detected trends for juveniles to exhibit greater infection risk than adults and for differential sex biases in T. cruzi prevalence between taxa, which align with variations in species-specific seasonal activity patterns. No geographic or taxonomic risk factors were identified. Conclusion: Our study contributed key data for population viability analyses and epidemiologic models in addition to providing a baseline for future T. cruzi surveillance among skunks and other wildlife species.

Discovery of an orally active benzoxaborole prodrug effective in the treatment of Chagas disease in non-human primates

Trypanosoma cruzi, the agent of Chagas disease, probably infects tens of millions of people, primarily in Latin America, causing morbidity and mortality. The options for treatment and prevention of Chagas disease are limited and underutilized. Here we describe the discovery of a series of benzoxaborole compounds with nanomolar activity against extra- and intracellular stages of T. cruzi. Leveraging both ongoing drug discovery efforts in related kinetoplastids, and the exceptional models for rapid drug screening and optimization in T. cruzi, we have identified the prodrug AN15368 that is activated by parasite carboxypeptidases to yield a compound that targets the messenger RNA processing pathway in T. cruzi. AN15368 was found to be active in vitro and in vivo against a range of genetically distinct T. cruzi lineages and was uniformly curative in non-human primates (NHPs) with long-term naturally acquired infections. Treatment in NHPs also revealed no detectable acute toxicity or long-term health or reproductive impact. Thus, AN15368 is an extensively validated and apparently safe, clinically ready candidate with promising potential for prevention and treatment of Chagas disease.

Our Current Understanding of Chagas Disease and Trypanosoma cruzi Infection in the State of Florida — an Update on Research in this Region of the USA

Purpose of Review

Chagas disease (CD) is a neglected tropical disease caused by the protozoan parasite, Trypanosoma cruzi. Parasite transmission primarily occurs through direct interaction with an infected triatomine insect vector (kissing bug), but other routes are known. We aim to review the literature and discuss the unique circumstances of CD in the US state of Florida.

Recent Findings

Florida is home to naturally occurring kissing bugs that are invading homes and harbor T. cruzi. The state is also home to a diverse population of immigrants from Chagas-endemic regions in Latin America. In the USA, Florida is the state with the third highest estimated burden of CD, although the true prevalence is unknown.

Summary

Chagas disease is a chronic infection that often remains silent for decades. Those who manifest chronic disease may eventually die from debilitating cardiac and/or gastrointestinal manifestations. Florida is an opportune region of the USA for the study of CD, due to the existence of endemic transmission cycles in addition to the burden among people born in Chagas-endemic regions.

Discrete typing units of Trypanosoma cruzi: Geographical and biological distribution in the Americas

Chagas disease caused by Trypanosoma cruzi is a public health issue in Latin America. This highly diverse parasite is divided into at least seven discrete typing units (DTUs) TcI-TcVI and Tcbat. Some DTUs have been associated with geographical distribution in epidemiological scenarios and clinical manifestations, but these aspects remain poorly understood. Many studies have focused on studying the parasite and its vectors/hosts, using a wide variety of genetic markers and methods. Here, we performed a systematic review of the literature for the last 20 years to present an update of DTUs distribution in the Americas, collecting ecoepidemiological information. We found that the DTUs are widespread across the continent and that there is a whole gamma of genetic markers used for the identification and genotyping of the parasite. The data obtained in this descriptor could improve the molecular epidemiology studies of Chagas disease in endemic regions.

Measurement(s)	Genotype
Technology Type(s)	Report from Literature

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.

The Influence of Geographical Origin, Age, Sex, and Animal Husbandry on the Spontaneous Histopathology of Laboratory Cynomolgus Macaques (Macaca Fascicularis): A Contemporary Global and Multisite Review of Historical Control Data

To investigate the influence of geographical origin, age, and sex on toxicologically relevant spontaneous histopathology findings in cynomolgus macaques (Macaca fascicularis), we performed a comparative analysis of historical control data (HCD) from 13 test sites that included 3351 animals (1645 females and 1706 males) sourced from Mauritius, China, Vietnam, and Cambodia, aged from 2 to 9.5 years, and from 446 toxicology studies evaluated between 2016 and 2021. The most common findings were mononuclear infiltrates in the kidney, liver, brain, and lung, which showed highest incidences in Mauritian macaques, and heart, salivary glands, and gastrointestinal tract (GIT), which showed highest incidences of mononuclear infiltrates in mainland Asian macaques. Developmental and degenerative findings were more common in Mauritian macaques, while lymphoid hyperplasia and lung pigment showed higher incidences in Asian macaques. Various sex and age-related differences were also present. Despite origin-related differences, the similarities in the nature and distribution of background lesions indicate that macaques from all geographical regions are suitable for toxicity testing and show comparable lesion spectrum. However, in a toxicity study, it is strongly recommended to use animals from a single geographical origin and to follow published guidelines when using HCD to evaluate and interpretate commonly diagnosed spontaneous lesions.

Phylogenetic diversity of two common Trypanosoma cruzi lineages in the Southwestern United States

Trypanosoma cruzi is the causative agent of Chagas disease, a devastating parasitic disease endemic to Central and South America, Mexico, and the USA. We characterized the genetic diversity of Trypanosoma cruzi circulating in five triatomine species (Triatoma gerstaeckeri, T. lecticularia, T.indictiva, T. sanguisuga and T. recurva) collected in Texas and Southern Arizona using multilocus sequence typing (MLST) with four single-copy loci (cytochrome oxidase subunit II- NADH dehydrogensase subunit 1 region (COII-ND1), mismatch-repair class 2 (MSH2), dihydrofolate reductase-thymidylate synthase (DHFR-TS) and a nuclear gene with ID TcCLB.506529.310). All T. cruzi variants fall in two main genetic lineages: 75% of the samples corresponded to T. cruzi Discrete Typing Unit (DTU) I (TcI), and 25% to a North American specific lineage previously labelled TcIV-USA. Phylogenetic and sequence divergence analyses of our new data plus all previously published sequence data from those four loci collected in the USA, show that TcIV-USA is significantly different from any other previously defined T. cruzi DTUs. The significant level of genetic divergence between TcIV-USA and other T. cruzi DTUs should lead to an increased focus on understanding the epidemiological importance of this DTU, as well as its geographical range and pathogenicity in humans and domestic animals. Our findings further corroborate the fact that there is a high genetic diversity of the parasite in North America and emphasize the need for appropriate surveillance and vector control programs for Chagas disease in southern USA and Mexico.

Trypanosoma cruzi genetic diversity: impact on transmission cycles and Chagas disease

Trypanosoma cruzi, the agent of Chagas disease (ChD), exhibits remarkable biological and genetic diversity, along with eco-epidemiological complexity. In order to facilitate communication among researchers aiming at the characterisation of biological and epidemiological aspects of T. cruzi, parasite isolates and strains were partitioned into seven discrete typing units (DTUs), TcI-TcVI and TcBat, identifiable by reproducible genotyping protocols. Here we present the potential origin of the genetic diversity of T. cruzi and summarise knowledge about eco-epidemiological associations of DTUs with mammalian reservoirs and vectors. Circumstantial evidence of a connection between T. cruzi genotype and ChD manifestations is also discussed emphasising the role of the host’s immune response in clinical ChD progression. We describe genomic aspects of DTUs focusing on polymorphisms in multigene families encoding surface antigens that play essential functions for parasite survival both in the insect vector and the mammalian host. Such antigens most probably contributed to the parasite success in establishing infections in different hosts and exploring several niches. Gaps in the current knowledge and challenges for future research are pointed out.

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.

A new subspecies of Trypanosoma cyclops found in the Australian terrestrial leech Chtonobdella bilineata

Previously, it was suggested that haemadipsid leeches represent an important vector of trypanosomes amongst native animals in Australia. Consequently, Chtonobdella bilineata leeches were investigated for the presence of trypanosome species by polymerase chain reaction (PCR), DNA sequencing and in vitro isolation. Phylogenetic analysis ensued to further define the populations present. PCR targeting the 28S rDNA demonstrated that over 95% of C. bilineata contained trypanosomes; diversity profiling by deep amplicon sequencing of 18S rDNA indicated the presence of four different clusters related to the Trypanosoma (Megatrypanum) theileri. Novy–MacNeal–Nicolle slopes with liquid overlay were used to isolate trypanosomes into culture that proved similar in morphology to Trypanosoma cyclops in that they contained a large numbers of acidocalcisomes. Phylogeny of 18S rDNA/GAPDH/ND5 DNA sequences from primary cultures and subclones showed the trypanosomes were monophyletic, with T. cyclops as a sister group. Blood-meal analysis of leeches showed that leeches primarily contained blood from swamp wallaby (Wallabia bicolour), human (Homo sapiens) or horse (Equus sp.). The leech C. bilineata is a host for at least five lineages of Trypanosoma sp. and these are monophyletic with T. cyclops; we propose Trypanosoma cyclops australiensis as a subspecies of T. cyclops based on genetic similarity and biogeography considerations.

Natural infection with Trypanosoma cruzi in three species of non-human primates in southeastern Mexico: A contribution to reservoir knowledge

The mechanisms of infection and dispersion of Trypanosoma cruzi among animals, especially in the sylvatic environment, are still not entirely clear, and various aspects of the transmission dynamics of this parasite in the sylvatic environment are still unknown. T. cruzi is a parasite with a great biological and genetic diversity that infects a wide variety of hosts, therefore, transmission cycles of this parasite are complex. The objective of this study was to determine the prevalence of T. cruzi infection and analyze the genetic variability of the discrete typing units (DTUs) of the parasite in three non-human primate species (Alouatta palliata, Alouatta pigra, and Ateles geoffroyi) in southeastern Mexico. A total of one hundred sixty-four serum samples (42 samples of A. pigra, 41 samples of A. palliata (free-ranging) and 81 samples of A. geoffroyi (hosted in care centers)) were analyzed for the detection of anti-T. cruzi antibodies by ELISA assays. The seroprevalence of infection was 23.39% in A. palliata, 21.40% in A. pigra and 16.27% in A. geoffroyi. Additionally, presence of parasite DNA was assessed by PCR, and the identification of DTUs was performed by real-time PCR coupled to High Resolution Melting (qPCR-HRM). Different DTUs (TcI, TcII, TcIII, TcV and TcVI) were found in the analyzed monkeys. In addition, infection of monkeys was not associated with age or gender, but it was associated with the species. This study reveals the risk of infection in the study area and that the different DTUs of the parasite can coexist in the same habitat, indicating that T. cruzi transmission in the study area is very complex and involves many ecological factors. However, there is a need for long-term studies of host-parasite interactions to provide a solid understanding of the ecology of these species and to understand the dispersion strategies of T. cruzi.

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?

Identification of blood-feeding sources in Panstrongylus, Psammolestes, Rhodnius and Triatoma using amplicon-based next-generation sequencing

BACKGROUND

Triatomines are hematophagous insects that play an important role as vectors of Trypanosoma cruzi, the causative agent of Chagas disease. These insects have adapted to multiple blood-feeding sources that can affect relevant aspects of their life-cycle and interactions, thereby influencing parasitic transmission dynamics. We conducted a characterization of the feeding sources of individuals from the primary circulating triatomine genera in Colombia using amplicon-based next-generation sequencing (NGS).

METHODS

We used 42 triatomines collected in different departments of Colombia. DNA was extracted from the gut. The presence of T. cruzi was identified using real-time PCR, and discrete typing units (DTUs) were determined by conventional PCR. For blood-feeding source identification, PCR products of the vertebrate 12S rRNA gene were obtained and sequenced by next-generation sequencing (NGS). Blood-meal sources were inferred using blastn against a curated reference dataset containing the 12S rRNA sequences belonging to vertebrates with a distribution in South America that represent a potential feeding source for triatomine bugs. Mean and median comparison tests were performed to evaluate differences in triatomine blood-feeding sources, infection state, and geographical regions. Lastly, the inverse Simpson's diversity index was calculated.

RESULTS

The overall frequency of T. cruzi infection was 83.3%. TcI was found as the most predominant DTU (65.7%). A total of 67 feeding sources were detected from the analyses of approximately 7 million reads. The predominant feeding source found was Homo sapiens (76.8%), followed by birds (10.5%), artiodactyls (4.4%), and non-human primates (3.9%). There were differences among numerous feeding sources of triatomines of different species. The diversity of feeding sources also differed depending on the presence of T. cruzi.

CONCLUSIONS

To the best of our knowledge, this is the first study to employ amplicon-based NGS of the 12S rRNA gene to depict blood-feeding sources of multiple triatomine species collected in different regions of Colombia. Our findings report a striking read diversity that has not been reported previously. This is a powerful approach to unravel transmission dynamics at microgeographical levels.

Trypanosoma cruzi infections and associated pathology in urban-dwelling Virginia opossums (Didelphis virginiana)

Trypanosoma cruzi, a zoonotic protozoan parasite, infects a wide range of mammals. The southern United States has endemic sylvatic transmission cycles maintained by several species of wildlife and domestic dogs. We hypothesized that urban-dwelling opossums (Didelphis virginiana) in South Texas are infected with T. cruzi, and that tissue pathology would be associated with infection. In 2017, we collected blood, heart tissue and anal gland secretions from 100 wild opossums across three seasons that were trapped by animal control in South Texas. In addition, anal gland tissue and intercostal muscle were collected from 43 of the 100 opossums for which time allowed the extra tissue collection. All blood, tissue, and secretion samples were screened for T. cruzi DNA using qPCR with confirmation of positive status achieved through one or more additional PCR assays, including a qPCR to determine the parasite discrete typing unit (DTU). T. cruzi DNA was detected in at least one tissue of 15% of the opossums sampled: blood clot (9%), heart tissue (10%), anal gland secretions (12%), intercostal muscle (16.3%), and anal gland tissue (11.6%). Infection was detected in two or more different tissue types in nine of the opossums. The 35 tissues for which parasite DTU was determined were exclusively 'Tcl'- a DTU previously associated with locally-acquired human disease in the United States. T. cruzi-positive opossums were nearly 14 times more likely to exhibit significant heart lesions on histopathology (lympoplasmacytic inflammation±fibrosis) when compared to negative opossums (OR = 13.56, CI = 1.23-751.28, p-value = 0.03). Three triatomines were opportunistically collected from the study site, of which two were infected (66.7%), and bloodmeal analysis revealed canine, opossum, and human bloodmeals. Given the presence of parasite in opossum blood, unique potential for shedding of parasite in anal glad secretions, and evidence of vectors feeding on opossums, it is likely that opossums serve as wild reservoirs around urban dwellings in South Texas.

Reproductive Outcomes in Rhesus Macaques (Macaca mulatta) with Naturally-acquired Trypanosoma cruzi Infection

Chagas disease is a zoonotic vector-borne disease caused by infection with the protozoan parasite Trypanosoma cruzi. T. cruzi is found in Latin America and the Southern United States, where it infects many species, including humans and nonhuman primates (NHPs). NHPs are susceptible to natural infection and can develop clinical symptoms consistent with human disease, including Chagasic cardiomyopathy, gastrointestinal disease and transplacental transmission, leading to congenital infection. Due to evidence of Chagas transmission in Texas, this study hypothesized T. cruzi infection was present in a closed, outdoor-housed breeding colony of rhesus macaques (Macaca mulatta) located at a biomedical research facility in Central Texas. In addition, we questioned whether seropositive female rhesus macaques might experience reproductive complications consistent with maternal-fetal Chagas disease. The seroprevalence of T. cruzi infection in the colony was assessed using an Enzyme Linked Immunosorbant Assay (ELISA) to detect antibodies against Tc24 antigen as a screening assay, and a commercially available immunochromatographic test (Chagas Stat Pak) as a confirmatory assay. Retrospective serologic analysis was performed to confirm the status of all T. cruzi-infected animals between the years 2012 to 2016. The medical history of all seropositive and seronegative breeding females within the colony from 2012 to 2016 was reviewed to determine each animals' level of reproductive fitness. The percentage of T. cruzi-seropositive animals ranged from 6.7% to 9.7% in adult animals and 0% to 0.44% in juveniles or weanling animals, depending on the year. An overall 3.9% seroprevalence of T. cruzi infection was found in the total population. No significant differences in any measure of reproductive outcomes were identified between seropositive and seronegative females from 2012 to 2016. The lack of significant adverse reproductive outcomes reported here may help inform future management decisions regarding seropositive female rhesus macaques within breeding colonies.

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.

Immigration and establishment of Trypanosoma cruzi in Arequipa, Peru

Changing environmental conditions, including those caused by human activities, reshape biological communities through both loss of native species and establishment of non-native species in the altered habitats. Dynamic interactions with the abiotic environment impact both immigration and initial establishment of non-native species into these altered habitats. The repeated emergence of disease systems in urban areas worldwide highlights the importance of understanding how dynamic migratory processes affect the current and future distribution and abundance of pathogens in urban environments. In this study, we examine the pattern of invasion of Trypanosoma cruzi-the causative agent of human Chagas disease-in the city of Arequipa, Peru. Phylogenetic analyses of 136 T. cruzi isolates from Arequipa and other South American locations suggest that only one T. cruzi lineage established a population in Arequipa as all T. cruzi isolated from vectors in Arequipa form a recent monophyletic group within the broader South American phylogeny. We discuss several hypotheses that may explain the limited number of established T. cruzi lineages despite multiple introductions of the parasite.

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.