High prevalence of Trypanosoma cruzi infection in shelter dogs from southern Louisiana, USA

Identification of highly conserved Trypanosoma cruzi antigens for the development of a universal serological diagnostic assay

Chagas Disease is an important neglected tropical disease caused by Trypanosoma cruzi. There is no gold standard for diagnosis and commercial serological tests perform poorly in certain locations. By aligning T. cruzi genomes covering parasite genetic and geographic diversity, we identified highly conserved proteins that could serve as universal antigens for improved diagnosis. Their antigenicity was tested in high-density peptide microarrays using well-characterized plasma samples, including samples presenting true infections but discordant serology. Individual and combination of epitopes were also evaluated in peptide-ELISAs. We identified >1400 highly conserved T. cruzi proteins evaluated in microarrays. Remarkably, T. cruzi positive controls had a different epitope recognition profile compared to serologically discordant samples. In particular, multiple T. cruzi antigens used in current tests and their strain-variants, and novel epitopes thought to be broadly antigenic failed to be recognized by discordant samples. Nonetheless, >2000 epitopes specifically recognized by IgGs from both positive controls and discordant samples were identified. Evaluation of selected peptides in ELISA further illustrated the extensive variation in antibody profiles among subjects and a peptide combination could outperform a commercial ELISA, increasing assay sensitivity from 52.3% to 72.7%. Individual variation in antibody profiles rather than T. cruzi diversity appears to be the main factor driving differences in serological diagnostic performance according to geography, which will be important to further elucidate. ELISA with a combination of peptides recognized by a greater number of individuals could better capture infections, and further development may lead to an optimal antigen mixture for a universal diagnostic assay.

Trypanosoma Cruzi antibody screening in North Texas client owned dogs

Despite multiple screening efforts to identify exposures to Trypanosoma cruzi, in dogs across southern USA, no published studies could be found involving client owned dogs in the North Texas Metroplex area. Therefore, a limited screen was conducted for client owned dogs, seeking routine or preventative care, from participating veterinary practices in the greater Dallas-Fort Worth (DFW) Metroplex from 2019 to 2021. Participants, with owner consent, ranged in age, breed, and length of time at recorded residence. Ninety-nine samples were acquired from participating veterinary practices, initially assessed with the Chagas StatPak, and positive samples were confirmed with IFA (indirect fluorescent antibody test) at the Texas Veterinary Medical Diagnostic Lab (TVMDL), College Station, Texas. Six samples were positive with the StatPak and only two were confirmed positive with IFA. Both animals were senior (10 and 8 years) with no owner reports of previous cardiac issues. The results appear reasonable within the context of previous studies and the seropositivity rate of 2% (n = 99) for client owned dogs included in this study are lower than previously reported rates for shelter dogs from the North Texas area.

Chagas Disease: A Silent Threat for Dogs and Humans

Chagas disease (CD) is a vector-borne Neglected Zoonotic Disease (NZD) caused by a flagellate protozoan, Trypanosoma cruzi, that affects various mammalian species across America, including humans and domestic animals. However, due to an increase in population movements and new routes of transmission, T. cruzi infection is presently considered a worldwide health concern, no longer restricted to endemic countries. Dogs play a major role in the domestic cycle by acting very efficiently as reservoirs and allowing the perpetuation of parasite transmission in endemic areas. Despite the significant progress made in recent years, still there is no vaccine against human and animal disease, there are few drugs available for the treatment of human CD, and there is no standard protocol for the treatment of canine CD. In this review, we highlight human and canine Chagas Disease in its different dimensions and interconnections. Dogs, which are considered to be the most important peridomestic reservoir and sentinel for the transmission of T. cruzi infection in a community, develop CD that is clinically similar to human CD. Therefore, an integrative approach, based on the One Health concept, bringing together the advances in genomics, immunology, and epidemiology can lead to the effective development of vaccines, new treatments, and innovative control strategies to tackle CD.

Abundant triatomines in Texas dog kennel environments: Triatomine collections, infection with Trypanosoma cruzi, and blood feeding hosts

Triatomine insects are vectors of the protozoan parasite Trypanosoma cruzi- the causative agent of Chagas disease. Chagas disease is endemic to Latin America and the southern United States and can cause severe cardiac damage in infected mammals, ranging from chronic disease to sudden death. Identifying interactions among triatomines, T. cruzi discrete typing units (DTUs), and blood feeding hosts is necessary to understand parasite transmission dynamics and effectively protect animal and human health. Through manual insect trapping efforts, kennel staff collections, and with the help of a trained scent detection dog, we collected triatomines from 10 multi-dog kennels across central and south Texas over a one-year period (2018-2019) and tested a subset to determine their T. cruzi infection status and identify the primary bloodmeal hosts. We collected 550 triatomines, including Triatoma gerstaeckeri (n = 515), Triatoma lecticularia (n = 15), Triatoma sanguisuga (n = 6), and Triatoma indictiva (n = 2), with an additional 10 nymphs and 2 adults unable to be identified to species. The trained dog collected 42 triatomines, including nymphs, from areas not previously considered vector habitat by the kennel owners. Using qPCR, we found a T. cruzi infection prevalence of 47 % (74/157), with T. lecticularia individuals more likely to be infected with T. cruzi than other species. Infected insects harbored two T. cruzi discrete typing units: TcI (64 %), TcIV (23 %), and mixed TcI/TcIV infections (13 %). Bloodmeal host identification was successful in 50/149 triatomines, revealing the majority (74 %) fed on a dog (Canis lupus), with other host species including humans (Homo sapiens), raccoons (Procyon lotor), chickens (Gallus gallus), wild pig (Sus scrofa), black vulture (Coragyps atratus), cat (Felis catus), and curve-billed thrasher (Toxostoma curviostre). Given the frequency of interactions between dogs and infected triatomines in these kennel environments, dogs may be an apt target for future vector control and T. cruzi intervention efforts.

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.

Validation of a multiplex microsphere immunoassay for detection of antibodies to Trypanosoma cruzi in dogs

The vector-borne protozoan parasite Trypanosoma cruzi causes Chagas disease in humans, dogs, and many other mammalian hosts. Canine Chagas disease is increasingly diagnosed in dogs of the southern United States where triatomine insect vectors occur, and there are limited veterinary testing options; only the indirect fluorescent antibody (IFA) test is offered at a single accredited diagnostic laboratory. We evaluated a multiplex microsphere immunoassay (MIA) for the detection of antibodies against T. cruzi in dogs and compared it with existing serologic methods to establish cutoff values and relative sensitivity and specificity. We tested 135 canine sera that had been characterized using the IFA and off-label use of 2 commercial rapid assays with our multiplex MIA against 12 antigens: 9 T. cruzi antigens, a negative control recombinant protein (green fluorescent protein, GFP), a Leishmania antigen, and a canine parvovirus antigen (used as an antibody control given near-ubiquitous parvoviral vaccination). The median fluorescence intensity (MFI) ratio between each T. cruzi antigen and GFP was calculated for every sample. Samples with an antigen:GFP MFI ratio > 4 SDs above the mean of 25 known-negative sera were considered positive to that antigen. Samples testing positive to ≥ 2 antigens were considered positive for T. cruzi antibodies. Compared to the IFA, our multiplex MIA had a relative sensitivity of 100% and specificity of 97.0%. Given its precision, high-throughput format, potential for automation, and lack of subjective interpretation, our multiplex MIA should be considered a valid and improved assay for T. cruzi antibodies in dogs.

Metabolomics of developmental changes in Triatoma sanguisuga gut microbiota

Triatoma sanguisuga is one of the major vectors of Trypanosoma cruzi in the southeastern US, where it sustains a robust zoonotic parasite transmission cycle and occasional human infections. A better understanding of triatomine development may allow for alternative approaches to insecticide-based vector control. Indeed, the role of the gut microbiota and bacterial endosymbionts in triatomine development and in their vectorial capacity is emerging. We investigated here the differences in microbiota among nymph and adult T. sanguisuga, to shed light on the metabolomic interactions occurring during development. Microbiota composition was assessed by 16s gene amplification and deep sequencing from field-caught adult bugs and their laboratory-raised progeny. Significant differences in microbiota bacterial diversity and composition were observed between nymphs and adults. Laboratory-raised nymphs showed a higher taxonomic diversity, and at least seven families predominated. On the other hand, field-caught adults had a lower bacterial diversity and four families comprised most of the microbiota. These differences in compositions were associated with differences in predicted metabolism, with laboratory-raised nymphs microbiota metabolizing a limited diversity of carbon sources, with potential for resource competition between bacterial families, and the production of lactic acid as a predominant fermentation product. On the other hand, field-caught adult microbiota was predicted to metabolize a broader diversity of carbon sources, with complementarity rather than competition among taxa, and produced a diverse range of products in a more balanced manner. The restricted functionality of laboratory-raised nymph microbiota may be associated with their poor development in captivity, and further understanding of the metabolic interactions at play may lead to alternative vector control strategies targeting triatomine microbiota.

Effectiveness of fluralaner treatment regimens for the control of canine Chagas disease: A mathematical modeling study

BACKGROUND

Canine Chagas disease is caused by the protozoan parasite Trypanosoma cruzi and transmitted by insect triatomine vectors known as kissing bugs. The agent can cause cardiac damage and long-term heart disease and death in humans, dogs, and other mammals. In laboratory settings, treatment of dogs with systemic insecticides has been shown to be highly efficacious at killing triatomines that feed on treated dogs.

METHOD

We developed compartmental vector-host models of T. cruzi transmission between the triatomine and dog population accounting for the impact of seasonality and triatomine migration on disease transmission dynamics. We considered a single vector-host model without seasonality, and model with seasonality, and a spatially coupled model. We used the models to evaluate the effectiveness of the insecticide fluralaner with different durations of treatment regimens for reducing T. cruzi infection in different transmission settings.

RESULTS

In low and medium transmission settings, our model showed a marginal difference between the 3-month and 6-month regimens for reducing T. cruzi infection among dogs. The difference increases in the presence of seasonality and triatomine migration from a sylvatic transmission setting. In high transmission settings, the 3-month regimen was substantially more effective in reducing T. cruzi infections in dogs than the other regimens. Our model showed that increased migration rate reduces fluralaner effectiveness in all treatment regimens, but the relative reduction in effectiveness is minimal during the first years of treatment. However, if an additional 10% or more of triatomines killed by dog treatment were eaten by dogs, treatment could increase T. cruzi infections in the dog population at least during the first year of treatment.

CONCLUSION

Our analysis shows that treating all peridomestic dogs every three to six months for at least five years could be an effective measure to reduce T. cruzi infections in dogs and triatomines in peridomestic transmission settings. However, further studies at the local scale are needed to better understand the potential impact of routine use of fluralaner treatment on increasing dogs' consumption of dead triatomines.

Genetic diversity of Trypanosoma cruzi infecting raccoons (Procyon lotor) in 2 metropolitan areas of southern Louisiana: implications for parasite transmission networks

Trypanosoma cruzi, the aetiological agent of Chagas disease, exists as an anthropozoonosis in Louisiana. Raccoons are an important reservoir, as they demonstrate high prevalence and maintain high parasitaemia longer than other mammals. Given the complex nature of parasite transmission networks and importance of raccoons as reservoirs that move between sylvatic and domestic environments, detailing the genetic diversity of T. cruzi in raccoons is crucial to assess risk to human health. Using a next-generation sequencing approach targeting the mini-exon, parasite diversity was assessed in 2 metropolitan areas of Louisiana. Sequences were analysed along with those previously identified in other mammals and vectors to determine if any association exists between ecoregion and parasite diversity. Parasites were identified from discrete typing units (DTUs) TcI, TcII, TcIV, TcV and TcVI. DTUs TcII, TcV and TcVI are previously unreported in raccoons in the United States (US). TcI was the most abundant DTU, comprising nearly 80% of all sequences. All but 1 raccoon harboured multiple haplotypes, some demonstrating mixed infections of different DTUs. Furthermore, there is significant association between DTU distribution and level III ecoregion in Louisiana. Finally, while certain sequences were distributed across multiple tissues, others appeared to have tissue-specific tropism. Taken together, these findings indicate that ongoing surveillance of T. cruzi in the US should be undertaken across ecoregions to fully assess risk to human health. Given potential connections between parasite diversity and clinical outcomes, deep sequencing technologies are crucial and interventions targeting raccoons may prove useful in mitigating human health risk.

Technological advances in the serological diagnosis of Chagas disease in dogs and cats: a systematic review

Background

Chagas disease (CD) is caused by Trypanosoma cruzi, which is transmitted mainly through the feces/urine of infected triatomine bugs. The acute phase lasts 2–3 months and is characterized by high parasitemia and nonspecific symptoms, whereas the lifelong chronic phase features symptoms affecting the heart and/or digestive tract occurring in 30–40% of infected individuals. As in humans, cardiac abnormalities are observed in T. cruzi-infected dogs and cats. We reviewed the technological advances in the serological diagnosis of CD in dogs and cats.

Methods

A review of the published literature during the last 54 years (1968–2022) on the epidemiology, clinical features, diagnosis, treatment and prevention of CD in dogs and cats was conducted.

Results

Using predefined eligibility criteria for a search of the published literature, we retrieved and screened 436 publications. Of these, 84 original studies were considered for inclusion in this review. Dogs and cats are considered as sentinels, potentially indicating an active T. cruzi transmission and thus the risk for human infection. Although dogs and cats are reputed to be important for maintaining the T. cruzi domestic transmission cycle, there are no commercial tests to detect past or active infections in these animals. Most published research on CD in dogs and cats have used in-house serological tests prepared with native and/or full-length recombinant antigens, resulting in variable diagnostic performance. In recent years, chimeric antigens have been used to improve the diagnosis of chronic CD in humans with encouraging results. Some of them have high performance values (> 95%) and extremely low cross-reactivity rates for Leishmania spp., especially the antigens IBMP-8.1 to IBMP-8.4. The diagnostic performance of IBMP antigens was also investigated in dogs, showing high diagnostic performance with negligible cross-reactivity with anti-Leishmania infantum antibodies.

Conclusions

The development of a commercial immunodiagnostic tool to identify past or active T. cruzi infections in dogs and cats is urgently needed. The use of chimeric recombinant T. cruzi antigens may help to fill this gap and is discussed in this review.

Graphical Abstract

Supplementary Information

The online version contains supplementary material available at 10.1186/s13071-022-05476-4.

Prediction of molecular mimicry between proteins from Trypanosoma sp. and human antigens associated with systemic lupus erythematosus

The immune response against pathogens induces protection from future infection, however, molecular mimicry between the pathogen and the human host can promote autoreactive responses. Using in silico approaches, we identified molecular mimicry between Trypanosoma sp. and human autoantigens involved in the development of systemic lupus erythematosus (SLE). We retrieved all reported autoantigen amino acid sequences for SLE from the AAgAtlas database to perform PSI-BLAST against the Trypanosoma sp proteome to determine amino acid sequence identity with each other. The antigens given in the Protein Data Bank without a 3D structure were modeled by homology with the "Swiss Modeller Server". Epitopes shared between Trypanosoma sp. and human antigens were identified using the Ellipro server and the Immune Epitope Database (IEDB), and cross-reactive epitopes were assigned to the 3D models. 36 autoantigens involved in SLE showed molecular mimicry with Trypanosoma sp. Antigens Epitope prediction revealed that some autoantigens shared several antigenic.

Trypanosoma cruzi and Other Vector-Borne Infections in Shelter Dogs in Two Counties of Oklahoma, United States

Trypanosoma cruzi is an emerging zoonotic vector-borne parasite infecting dogs and other mammals in the United States. In this study we evaluated shelter dogs in one northeastern and one southeastern county in Oklahoma for prevalence of exposure to T. cruzi. Dogs were tested for antibodies against T. cruzi using the Chagas STAT PAK^® assay and for T. cruzi in circulation by PCR. In addition, dogs were tested for evidence of infection with other vector-borne organisms using the SNAP^® 4Dx^® Plus Test and PCR. Overall, 26 of 197 (13.2%) shelter dogs had detectable antibodies against T. cruzi and 3 of 189 (1.6%) dogs were PCR positive. In addition, we found that 42 of 197 (21.3%) shelter dogs had evidence of exposure to or were infected with at least one vector-borne agent other than T. cruzi based on serology and/or PCR; 9 of 42 (21.4%) of these dogs were also positive for T. cruzi antibodies. Other infections identified in dogs included Anaplasma phagocytophilum, Anaplasma platys, Babesia sp. (Coco), Dirofilaria immitis, Ehrlichia canis, Ehrlichia chaffeensis, Ehrlichia ewingii, and Hepatozoon americanum. This study serves to boost state-wide veterinary and public health awareness of T. cruzi and other vector-borne pathogens infecting shelter dogs in Oklahoma. Results indicate the need for more comprehensive screening of shelter dogs in Oklahoma for exposure to vector-borne agents to enhance surveillance and to identify dogs in need of additional specific veterinary care.

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.

Seroprevalence and detection of Trypanosoma cruzi in dogs living in a non-endemic area for Chagas disease in the legal Amazon region, Brazil

Trypanosoma cruzi, the etiological agent for Chagas disease, is widely distributed in the Americas. Its hosts are humans and wild and domestic mammals, and its vectors are triatomine insects. Studies have indicated that domestic dogs are sentinel animals in the epidemiology of Chagas disease in endemic regions, including states in the Legal Amazon region of Brazil. In São Luís, the capital of Maranhão, a non-endemic state, the existence of a domestic cycle involving domestic rats has been proven, along with a wild cycle maintained by didelphids. However, no studies on T. cruzi infection in domestic animals in this locality have been conducted. The aim of this study was to investigate occurrence of T. cruzi in dogs living in the Itaqui Bacanga district of São Luís, Maranhão, by means of serological and molecular tests. Blood samples were obtained from 330 dogs and structured epidemiological questionnaires were applied to their keepers. These samples were used in the indirect immunofluorescent antibody test (IFAT), enzyme-linked immunosorbent assay (ELISA) and polymerase chain reaction (PCR). Fisher's exact test was used for statistical calculations with the aim of identifying risk factors. Out of the 330 animals, 105 (31.8%) were reactive in IFAT, 46 (13.0%) in ELISA and 20 (6.0%) in both serological tests. The results were not significant (p > 0.05) when submitted to statistical analysis for the studied variables. From PCR, 58 samples (17.5%) were found to be positive and, of these, one (0.3%) showed similarity to T. cruzi after sequencing. These data demonstrate that dogs were exposed to and infected by T. cruzi. Thus, they can be considered sentinel animals for Chagas disease in the locality studied, which signals that there is a need for epidemiological surveillance actions.

High incidence of Trypanosoma cruzi infections in dogs directly detected through longitudinal tracking at 10 multi-dog kennels, Texas, USA

Canine Chagas disease, caused by the protozoan parasite Trypanosoma cruzi, is increasingly recognized as a health concern for dogs in the USA, and infected dogs may signal geographic regions of risk for human disease. Dogs living in multi-dog kennel environments (kennels with more than one dog) where triatomine vectors are endemic may be at high risk for infection. We monitored a cohort of 64 T. cruzi-infected and uninfected dogs across 10 kennels in Texas, USA, to characterize changes in infection status over one year. We used robust diagnostic criteria in which reactivity on multiple independent platforms was required to be considered positive. Among the 30 dogs enrolled as serologically- and/or PCR-positive, all but one dog showed sustained positive T. cruzi diagnostic results over time. Among the 34 dogs enrolled as serologically- and PCR-negative, 10 new T. cruzi infections were recorded over a 12-month period. The resulting incidence rate for dogs initially enrolled as T. cruzi-negative was 30.7 T. cruzi infections per 100 dogs per year. This study highlights the risk of T. cruzi infection to dogs in kennel environments. To protect both dog and human health, there is an urgent need to develop more integrated vector control methods as well as prophylactic and curative antiparasitic treatment options for T. cruzi infection in dogs.

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.

Trypanosoma (Megatrypanum) pestanai in Eurasian badgers (Meles meles) and Ixodidae ticks, Italy

Trypanosomes are haemoflagellate protozoa transmitted by blood-feeding arthropods causing infections in a wide range of mammals, including humans. Adult badgers (Meles meles, n = 2), displaying severe paralysis, ataxia and severe ectoparasite infestation, were rescued from a peri-urban area of Bari (southern Italy). Blood samples and ectoparasites were screened for Trypanosoma spp. by the combined PCR/sequencing approach, targeting a fragment of 18S rRNA gene. Smears of haemolymph, guts and salivary glands of the alive ticks were microscopically observed. No haematological alterations, except thrombocytopenia, were found. Trypomastigotes and epimastigotes were observed in the blood smears of both badgers and Trypanosoma pestanai was molecularly identified. Out of 33 ticks (i.e. n = 31 Ixodes canisuga, n = 2 Ixodes ricinus) and two fleas (Ctenocephalides felis), 11 specimens (n = 5 I. canisuga engorged nymphs, n = 4 engorged females and n = 2 I. ricinus engorged females) tested positive only for T. pestanai DNA. All smears from ticks were negative. The present study firstly revealed T. pestanai in Ixodidae and badgers from Italy, demonstrating the occurrence of the protozoan on the peninsula. Further studies are needed to clarify the occurrence of the only known vector of this parasite, Paraceras melis flea, as well as other putative arthropods involved in the transmission of T. pestanai.

Locally Transmitted Trypanosoma cruzi in a Domestic Llama (Lama glama) in a Rural Area of Greater New Orleans, Louisiana, USA

Trypanosoma cruzi-associated megaesophagus was diagnosed in a domestic Louisiana-born llama with no significant travel history. The llama resided in the same rural area of greater New Orleans, Louisiana, where the first human autochthonous case of Chagas disease was identified in the state. Venous blood from the llama tested positive for T. cruzi kinetoplastid DNA by conventional PCR. The cardiac evaluation was unremarkable, while thoracic radiographs revealed generalized megaesophagus. The llama received supportive care, but was ultimately humanely euthanized. The esophagus was severely distended throughout its length on necropsy, and histologic evaluation showed no microscopic changes in esophageal tissue and minimal to mild lymphoplasmacytic inflammation in cardiac tissue. T. cruzi DNA was detected by conventional PCR in the esophagus, small intestine, and blood despite no protozoan organisms being observed in multiple tissue sections examined. This report contributes to the growing body of evidence of local transmission of T. cruzi in the southern United States, and Chagas disease should be considered a differential diagnosis when evaluating llamas and other large animal species for esophageal dysfunction. There is little research describing megaesophagus or Chagas disease in llamas, and this report aims to increase awareness about this zoonotic disease that is becoming more frequently reported in the southern United States.

Trypanosoma cruzi vectors and reservoirs in Southern Sergipe

INTRODUCTION

Chagas disease is a health problem that affects approximately 7 million people worldwide, according to the World Health Organization. Vector transmission is one of the most important routes in South and Central American countries. Between 2013 and 2019, municipalities of Sergipe sent 507 triatomines for analysis, unveiling the largest records found in the south in the villages of Poço da Clara, Alagoinhas and Pilões, and the municipality of Tobias Barreto. The high prevalence of infected vectors in these localities motivated this epidemiological study.

METHODS

After educational lectures on the vectors and risks of the disease, a structured questionnaire was administered to identify areas and risk factors for transmission of the parasite. The data guided the collection of vectors and blood samples from domestic reservoirs.

RESULTS

The studied region is considered endemic for triatomines infected by Trypanosoma cruzi with three species of vectors; the highest prevalence was Panstrongylus lutzi (54.83%), followed by Triatoma pseudomaculata (43.54%), and Triatoma tibiamaculata (1.61%). In the villages in this study, 100% of the vectors were found intradomically. The coexistence of residents with domestic animals was reported by 62.04% (255) of those surveyed. Forty-one small animals that were actively living with humans at home in the localities were evaluated serologically. No infection was observed in the domestic animals.

CONCLUSIONS

There are favorable conditions for the domiciliation of triatomines in the evaluated locations, contributing to the risk of vectorial transmission of Chagas disease.

Shelter cats host infections with multiple Trypanosoma cruzi discrete typing units in southern Louisiana

Trypanosoma cruzi is a zoonotic parasite endemic in the southern US and the Americas, which may frequently infect dogs, but limited information is available about infections in cats. We surveyed a convenience sample of 284 shelter cats from Southern Louisiana to evaluate T. cruzi infection using serological and PCR tests. Parasites from PCR positive cats were also genotyped by PCR and deep sequencing to assess their genetic diversity. We detected a seropositivity rate for T. cruzi of at least 7.3% (17/234), and 24.6% of cats (70/284) were PCR positive for the parasite. Seropositivity increased with cat age (R² = 0.91, P = 0.011), corresponding to an incidence of 7.2% ± 1.3 per year, while PCR positivity decreased with age (R² = 0.93, P = 0.007). Cats were predominantly infected with parasites from TcI and TcVI DTUs, and to a lesser extent from TcIV and TcV DTUs, in agreement with the circulation of these parasite DTUs in local transmission cycles. These results indicate that veterinarians should have a greater awareness of T. cruzi infection in pets and that it would be important to better evaluate the risk for spillover infections in humans.

Trypanosoma cruzi discrete typing unit TcIV implicated in a case of acute Chagas disease in a domiciliated dog in the western Amazon

Chagas disease is caused by the protozoan Trypanosoma cruzi. Seven lineages have been identified based on different molecular markers, namely TcI, TcII, TcIII, TcIV, TcV, TcVI, and TcBat. Dogs play the role of epidemiological sentinels being domestic reservoirs of T. cruzi. The aim of the current study was to report the first case of CD in a domestic dog in Manaus, Amazonas, Brazil, infected with T. cruzi DTU TcIV. We hope our report encourages veterinarians and surveillance professionals to a take a deeper look at T. cruzi infection in domestic animals.

Assessing Trypanosoma cruzi Parasite Diversity through Comparative Genomics: Implications for Disease Epidemiology and Diagnostics

Chagas disease is an important vector-borne neglected tropical disease that causes great health and economic losses. The etiological agent, Trypanosoma cruzi, is a protozoan parasite endemic to the Americas, comprised by important diversity, which has been suggested to contribute to poor serological diagnostic performance. Current nomenclature describes seven discrete typing units (DTUs), or lineages. We performed the first large scale analysis of T. cruzi diversity among 52 previously published genomes from strains covering multiple countries and parasite DTUs and assessed how different markers summarize this genetic diversity. We also examined how seven antigens currently used in commercial serologic tests are conserved across this diversity of strains. DTU structuration was confirmed at the whole-genome level, with evidence of sub-DTU diversity, associated in part to geographic structuring. We observed very comparable phylogenetic tree topographies for most of the 32 markers investigated, with clear clustering of sequences by DTU, and a few of these markers suggested some degree of intra-lineage diversity. At least three of the currently used antigens represent poorly conserved sequences, with sequences used in tests quite divergent from sequences in many strains. Most markers are well suited for estimating parasite diversity to DTU level, and a few are particularly well-suited to assess intra-DTU diversity. Analysis of antigen sequences across all strains indicates that antigenic diversity is a likely explanation for limited diagnostic performance in Central and North America.

Triatomine Feeding Profiles and Trypanosoma cruzi Infection, Implications in Domestic and Sylvatic Transmission Cycles in Ecuador

Understanding the blood meal patterns of insects that are vectors of diseases is fundamental in unveiling transmission dynamics and developing strategies to impede or decrease human–vector contact. Chagas disease has a complex transmission cycle that implies interactions between vectors, parasites and vertebrate hosts. In Ecuador, limited data on human infection are available; however, the presence of active transmission in endemic areas has been demonstrated. The aim of this study was to determine the diversity of hosts that serve as sources of blood for triatomines in domestic, peridomestic and sylvatic transmission cycles, in two endemic areas of Ecuador (central coastal and southern highland regions). Using conserved primers and DNA extracted from 507 intestinal content samples from five species of triatomines (60 Panstrongylus chinai, 17 Panstrongylus howardi, 1 Panstrongylus rufotuberculatus, 427 Rhodnius ecuadoriensis and 2 Triatoma carrioni) collected from 2006 to 2013, we amplified fragments of the cytb mitochondrial gene. After sequencing, blood meal sources were identified in 416 individuals (146 from central coastal and 270 from southern highland regions), achieving ≥ 95% identity with GenBank sequences (NCBI-BLAST tool). The results showed that humans are the main source of food for triatomines, indicating that human–vector contact is more frequent than previously thought. Although other groups of mammals, such as rodents, are also an available source of blood, birds (particularly chickens) might have a predominant role in the maintenance of triatomines in these areas. However, the diversity of sources of blood found might indicate a preference driven by triatomine species. Moreover, the presence of more than one source of blood in triatomines collected in the same place indicated that dispersal of vectors occurs regardless the availability of food. Dispersal capacity of triatomines needs to be evaluated to propose an effective strategy that limits human–vector contact and, in consequence, to decrease the risk of T. cruzi transmission.

Genetic diversity of Trypanosoma cruzi parasites infecting dogs in southern Louisiana sheds light on parasite transmission cycles and serological diagnostic performance

Background

Chagas disease is a neglected zoonosis of growing concern in the southern US, caused by the parasite Trypanosoma cruzi. We genotyped parasites in a large cohort of PCR positive dogs to shed light on parasite transmission cycles and assess potential relationships between parasite diversity and serological test performance.

Methodology/principal findings

We used a metabarcoding approach based on deep sequencing of T. cruzi mini-exon marker to assess parasite diversity. Phylogenetic analysis of 178 sequences from 40 dogs confirmed the presence of T. cruzi discrete typing unit (DTU) TcI and TcIV, as well as TcII, TcV and TcVI for the first time in US dogs. Infections with multiple DTUs occurred in 38% of the dogs. These data indicate a greater genetic diversity of T. cruzi than previously detected in the US. Comparison of T. cruzi sequence diversity indicated that highly similar T. cruzi strains from these DTUs circulate in hosts and vectors in Louisiana, indicating that they are involved in a shared T. cruzi parasite transmission cycle. However, TcIV and TcV were sampled more frequently in vectors, while TcII and TcVI were sampled more frequently in dogs.

Conclusions/significance

These observations point to ecological host-fitting being a dominant mechanism involved in the diversification of T. cruzi-host associations. Dogs with negative, discordant or confirmed positive T. cruzi serology harbored TcI parasites with different mini-exon sequences, which strongly supports the hypothesis that parasite genetic diversity is a key factor affecting serological test performance. Thus, the identification of conserved parasite antigens should be a high priority for the improvement of current serological tests.

Chagas disease is a neglected zoonosis of growing concern in the southern US, caused by the parasite Trypanosoma cruzi. Here we analyzed the parasite genetic diversity in a large cohort of infected dogs to better understand parasite transmission cycles and assess potential relationships between parasite diversity and serological test performance. We used DNA sequencing of a well characterized T. cruzi genetic marker to assess parasite diversity. We confirmed the presence of T. cruzi lineages TcI and TcIV, and report TcII, TcV and TcVI for the first time in US dogs. Parasite lineages TcIV TcII and TcVI appeared more frequent in dogs compared to insect vectors. Dogs with negative, discordant or confirmed positive T. cruzi serology harbored genetically different TcI parasites, which shows that parasite genetic diversity is a key factor affecting serological test performance. Thus, the identification of parasite antigens conserved across strains and lineages should be a high priority for the improvement of current serological tests.

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.

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.

Nationwide Exposure of U.S. Working Dogs to the Chagas Disease Parasite, Trypanosoma cruzi

Trypanosoma cruzi is a zoonotic protozoan parasite vectored by triatomine insects that are endemic to the Americas, including the southern United States. Surveillance of domestic dogs for T. cruzi exposure allows for the determination of geographic regions of transmission that are relevant for human and animal health. The U.S. Department of Homeland Security (DHS) working dogs provide critical security and detection services across the country, and many train or work in the southern United States, where they are at risk for T. cruzi exposure. We sampled blood from 1,610 working dogs (predominantly Belgian Malinois, German shepherds, and Labrador retrievers) from six task forces (including the Transportation Security Administration, Customs and Border Protection, Secret Service, and more) and two canine training centers across 41 states from 2015 to 2018. Canine sera that were reactive on at least two independent serological assays were considered positive for anti-T.-cruzi antibodies. In addition, up to three independent polymerase chain reaction (PCR) assays were used to detect and type T. cruzi DNA. Overall seroprevalence was 7.5%, and four dogs (0.25%, n = 1,610) had detectable parasite DNA in the blood, comprising parasite discrete taxonomic units (DTUs) TcIV and a coinfection of TcI/TcIV. Dogs that worked within versus outside of the geographic range of established triatomines showed comparable seroprevalence (7.3% and 9.2%, respectively; P = 0.61). Determining the prevalence of T. cruzi in these working dogs and looking at spatially associated risk factors have practical implications for disease risk management and could assist with improved control measures to protect both animal and human health.

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.