Understanding the role of dogs (Canis lupus familiaris) in the transmission dynamics of Trypanosoma cruzi genotypes in Colombia

Trypanosoma cruzi in domestic and wild mammals in the northeast region of Colombia

Trypanosoma cruzi hosts can serve as a source of infection for animals, vectors, and humans, contributing to the establishment of Chagas disease (CD) in a given area. Traditionally, the Department of Córdoba has not been considered a transmission area for CD; however, the report of several acute cases of Chagas disease highlights the importance of studying the dynamics of disease transmission in this region. This study aimed to detect T. cruzi in domestic and wild mammals in the department of Córdoba. In 2017, a cross-sectional descriptive study was conducted in six villages in two municipalities in the department of Córdoba. Blood samples from dogs living in the zones were collected in EDTA vacutainer tubes for domestic mammals. Wild mammals were collected using Sherman and Tomahawk traps and mist nets in crops and peridomiciles. T. cruzi DNA was detected using the kinetoplast DNA (kDNA) variable region and the tandem repeat satellite region of T. cruzi as molecular targets. We sampled 168 dogs and 146 wild mammals. The detected prevalence of T. cruzi was 6.37%; the TcI lineage was found in D. marsupialis, H. anomalus, and one canine. A specimen of D. marsupialis with TcI and TcII lineages was also identified. T. cruzi DNA was detected in domestic and wild animals in the study area, indicating the circulation of the parasite in peridomestic environments. D. marsupialis may represent an important host in maintaining this region's wild and domestic cycle.

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.

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.

Trypanosoma cruzi Parasite Burdens of Several Triatomine Species in Colombia

Trypanosoma cruzi, the causal agent of Chagas disease, is mainly transmitted by insects of the Triatominae subfamily. In Colombia, there are 26 triatomine species, and 16 of them are naturally infected with the parasite. The parasite loads of naturally infected vectors can be significant in targeting specific species that can affect the epidemiology of the disease. Studying their ecology and behavior is vital to understand their role in T. cruzi transmission dynamics. We evaluated the parasite loads of 182 field-collected triatomines corresponding to 10 species in 13 departments across Colombia. We standardized a methodology to quantify T. cruzi DNA in these insects. We obtained a LOD (limit of detection) of 3.05 p-eq/mL. The 82% of triatomines we evaluated were positive for T. cruzi infection, with loads ranging from hundreds to millions of equivalent parasites per milliliter. Panstrongylus geniculatus, Rhodnius prolixus, and Triatoma dimidiata were the species with the highest loads of T. cruzi; however, other species whose role as vectors is still unknown were also found with high loads of parasites. Our results suggest the relevance of secondary species for T. cruzi transmission in Colombia. We hope our data can help improve entomological surveillance and vector control programs in the country and the region.

[Circulación de Leishmania infantum y Trypanosoma cruzi en perros domésticos de áreas urbanas de Sincelejo, región Caribe de Colombia]

Introducción. La enfermedad de Chagas y la leishmaniasis tradicionalmente se han considerado zoonosis endémicas de áreas rurales del país. Sin embargo, la aparición de casos de estas enfermedades en áreas urbanas sugiere nuevos ciclos de circulación de estos parásitos. Por esta razón, se ha propuesto a los perros como centinelas de estos agentes zoonóticos, dado su rol como huéspedes accidentales o reservorios. Objetivo. Evaluar la circulación silenciosa de Leishmania spp. y Trypanosoma cruzi en perros de zonas urbanas de la ciudad de Sincelejo, Sucre. Materiales y métodos. Se analizaron 100 muestras de sangre de perros para amplificar la región ITS1 de Leishmania spp. Las muestras positivas se utilizaron para amplificar la región conservada del minicírculo del ADN del cinetoplasto de Leishmania infantum y para el análisis de polimorfismos de longitud de fragmentos de restricción con la endonucleasa HaeIII. Por otra parte, se amplificó un fragmento del ADN satelital de T. cruzi. Además, se evaluó la presencia de infecciones por Ehrlichia canis y Anaplasma platys, como potencialmente modificadoras de las manifestaciones clínicas. Resultados. De los 100 perros estudiados, se detectó: Leishmania spp. en 32, T. cruzi en 12, ambos parásitos en 7 y L. infantum en 18. Se encontraron infecciones por anaplasmatáceos en 18, y coinfecciones por bacterias y parásitos en 8 de los perros. En general, 47 de los animales estaban infectados por, al menos, un agente etiológico. Conclusión. Se demuestra la circulación de L. infantum y T. cruzi en zonas urbanas de Sincelejo, así como coinfecciones de estos parásitos junto con parásitos de la familia Anaplasmataceae. El presente estudio demuestra la conveniencia del uso de perros en la vigilancia epidemiológica de estos agentes zoonóticos.

Co-infection patterns of vector-borne zoonotic pathogens in owned free-ranging dogs in central Chile

We investigated the co-occurrence of the nine of the most relevant canine vector-borne pathogens (CVBP) using conventional and real-time PCR and evaluated risk factors and potential non-apparent haematological alterations associated with co-infection in 111 rural, owned, free-ranging dogs in the Metropolitan Region of Chile.

At least one pathogen was detected in 75% of the dogs. DNA of Anaplasma platys (Ap; 36%), Candidatus Mycoplasma haematoparvum (CMhp; 31%), Mycoplasma haemocanis (Mhc; 28%), Trypanosoma cruzi (17%), Leishmania spp. (4.5%), and Acanthocheilonema reconditum (1%) was detected. All dogs were negative for Ehrlichia spp., Rickettsia spp., Bartonella spp., Piroplasmida, and Hepatozoon spp. Thirty-eight dogs (34%) were coinfected. CMhp was involved in 71%, Mhc in 58%, and Ap in 50% of the co-infections. The most common co-infection pattern was CMhp–Mhc (37% of the cases). The prevalence of Ap was higher in juvenile than in adult dogs, whereas the opposite was found for CMhp and Mhc. Adult dogs were four times more likely of being co-infected than juveniles. Co-infected animals showed higher white blood cell count, segmented neutrophil count, and GGT levels than non-co-infected dogs. Clinically healthy but infected dogs may act as reservoirs of CVBP, and their free-ranging behavior would facilitate the spread of these pathogens to other dogs as well as human beings or wild carnivores.

Enzootic Trypanosoma cruzi infection by Rhodnius prolixus shows transmission to humans and dogs in Vichada, Colombia

Background

Rhodnius prolixus is considered the most relevant Trypanosoma cruzi vector in Colombia and Venezuela due it is responsible for domestic transmission in both countries. However, a wild population of this species is distributed in the eastern plains of the Orinoco region and Amazonia jungle, where its epidemiological importance has not been sufficiently elucidated. This study aimed to assess epidemiological parameters of T. cruzi transmission in the Department of Vichada, Colombia.

Methods

We determined the characteristics of T. cruzi transmission using entomological studies in domestic and sylvatic ecotopes. We analyzed the T. cruzi infection in triatomine insects, identified blood meal sources, and conducted a serological determination of T. cruzi infection in scholar-aged children, domestic dogs, and wild hosts.

Results

Fifty-four triatomine bugs, 40 T. maculata and 14 R. prolixus were collected in peridomestic and sylvatic ecotopes. Infected R. prolixus was observed in La Primavera, Santa Rosalia, and Cumaribo municipalities. All the T. maculata bugs were not infected. Serological analysis indicated that two of 3,425 children were T. cruzi positive. The seroprevalence in domestic dogs was 10,5% (49/465). Moreover, 22 synanthropic mammals were sampled, being Didelphis marsupialis the most common. TcI genotype was detected in seropositive dogs, R. prolixus, and D. marsupialis.

Conclusion

The present work describes extra domestic R. prolixus and D. marsupialis in a sylvatic T. cruzi transmission cycle with transmission to humans and domestic dogs in Colombia’s Vichada Department.

Interrogating the transmission dynamics of Trypanosoma cruzi (Trypanosomatida, Trypanosomatidae) by Triatoma venosa (Hemiptera: Reduviidae) after the elimination of vector transmission by Rhodnius prolixus in Boyacá eastern Colombia

Chagas disease (CD) is a parasitic zoonosis (Trypanosoma cruzi) that is endemic in Colombia. Vector control of Rhodnius prolixus, the main domestic T. cruzi vector, has been achieved in a large part of the area with historically vector transmission of CD. It is necessary to understand the ecological behavior characteristics of local native vectors to ensure sustainability of the vector control programs. To evaluate the long-term success of a recent vector control campaign in the Boyacá department (Colombia), we used a combined strategy of entomological surveillance with co-existing canine surveillance from ten rural villages within six municipalities of the Tenza valley region (Boyacá, Colombia): Chinavita, Garagoa, Guateque, Somondoco, Sutatenza and Tenza, with historical reports of R. prolixus and secondary vectors. Collected triatomines and canine whole blood were analyzed for T. cruzi infection and genotyping. Triatomine bugs specimens were evaluated for blood meal source. Canine serology was performed using two distinct antibody assays. In total, 101 Triatoma venosa were collected by active search in domestic and peridomestic habitats. A natural infection prevalence of 13.9% (14/101) and four feeding sources were identified: human, dog, rat, and hen. A frequency infection of 46.5% (40/87) was observed from two independent serological tests and T. cruzi DNA was detected in 14 dogs (16.4%). Only TcIsylvatic DTU was detected. The results suggest that T. venosa present eco-epidemiological characteristics to maintain the transmission of T. cruzi in Tenza valley. This species has reinfested the intervened households and it has an active role in domestic and peridomestic transmission of T. cruzi due to their infection rates and feeding behavior. Therefore, this species should be considered as epidemiologically relevant for vector control strategies. Moreover, there is a need for human serological studies to have a close up of risk they are exposed to.

A mixed-methods approach to understanding domestic dog health and disease transmission risk in an indigenous reserve in Guyana, South America

Domestic dogs (Canis lupus familiaris) can transmit a variety of pathogens due to their ubiquitousness in urban, rural and natural environments, and their close interactions with wildlife and humans. In this study, we used a mixed-methods approach to assess the role of domestic dogs as potential intermediaries of disease transmission from wildlife to humans among indigenous Waiwai in the Konashen Community Owned Conservation Area, Guyana. To address these objectives we 1) performed physical examinations and collected biological samples to assess Waiwai domestic dog health, and 2) administered questionnaires to characterize the role of dogs in the community and identify potential transmission pathways between wildlife, dogs, and humans. We observed ectoparasites on all dogs (n = 20), including: fleas (100%), ticks (15%), botflies (30%), and jigger flea lesions (Tunga penetrans) (80%). Ten percent of dogs were seropositive for Ehrlichia canis/ewingii, 10% were positive for Dirofilaria immitis, and one dog was seropositive for Leishmania infantum. All dogs (n = 20) were seronegative for: canine distemper virus, Brucella canis, Leptospira serovars, Trypanosoma cruzi, Anaplasma phagocytophilum/platys and Borrelia burgdorferi. Our questionnaire data revealed that the Waiwai remove ectoparasites from their dogs, clean up dog feces, and administer traditional and/or Western medicine to their dogs. White blood cell, strongyle-type ova, and eosinophil counts were lower in dogs that were not frequently used for hunting, dogs that did receive traditional and/or western medicine, and dogs that were frequently kept in elevated dog houses, although differences were not statistically significant. While our results suggest that the Waiwai have developed cultural practices that may promote dog health and/or prevent zoonotic disease transmission, more research is necessary to determine the efficacy of these practices. Our study provides important data on the health of dogs and the potential for disease transmission to humans in a zoonotic hotspot.

Domestic dogs are found throughout the world and interact closely with both wildlife and humans. Dogs can harbor numerous diseases that can be transmitted to other domestic and wildlife species, and human populations. They can serve as bridges, moving diseases between unconnected populations. Additionally, dogs can help in the early detection of wildlife and human diseases. Therefore, understanding what pathogens domestic dogs harbor can inform both wildlife and human health. In this study, we performed physical examinations, collected biological samples, and administered questionnaires to assess dog health and understand the role of dogs as potential bridges of disease transmission from wildlife to humans among indigenous Waiwai in the Konashen Community Owned Conservation Area, Guyana. On physical exam, we observed ectoparasites on all dogs, however, few pathogens were detected with diagnostic screening. Our questionnaire data revealed that the Waiwai engage in husbandry practices that may promote Waiwai dog health.

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.

The potential risk of enzootic Trypanosoma cruzi transmission inside four training and re-training military battalions (BITER) in Colombia

BACKGROUND

Colombia's National Army is one of the largest military institutions in the country based on the number of serving members and its presence throughout the country. There have been reports of cases of acute or chronic cases of Chagas disease among active military personnel. These may be the result of military-associated activities performed in jungles and other endemic areas or the consequence of exposure to Trypanosoma cruzi inside military establishments/facilities located in endemic areas. The aim of the present study was to describe the circulation of T. cruzi inside facilities housing four training and re-training battalions [Battalions of Instruction, Training en Re-training (BITERs)] located in municipalities with historical reports of triatomine bugs and Chagas disease cases. An entomological and faunal survey of domestic and sylvatic environments was conducted inside each of these military facilities.

METHODS

Infection in working and stray dogs present in each BITER location was determined using serological and molecular tools, and T. cruzi in mammal and triatomine bug samples was determined by PCR assay. The PCR products of the vertebrate 12S rRNA gene were also obtained and subjected to Sanger sequencing to identify blood-feeding sources. Finally, we performed a geospatial analysis to evaluate the coexistence of infected triatomines and mammals with the military personal inside of each BITER installation.

RESULTS

In total, 86 specimens were collected: 82 Rhodnius pallescens, two Rhodnius prolixus, one Triatoma dimidiata and one Triatoma maculata. The overall T. cruzi infection rate for R. pallescens and R. prolixus was 56.1 and 100% respectively, while T. dimidiata and T. maculata were not infected. Eight feeding sources were found for the infected triatomines, with opossum and humans being the most frequent sources of feeding (85.7%). Infection was most common in the common opossum Didelphis marsupialis, with infection levels of 77.7%. Sylvatic TcI was the most frequent genotype, found in 80% of triatomines and 75% of D. marsupialis. Of the samples collected from dogs (n = 52), five (9.6%; 95% confidence interval: 3.20-21.03) were seropositive based on two independent tests. Four of these dogs were creole and one was a working dog. The spatial analysis revealed a sympatry between infected vectors and mammals with the military population.

CONCLUSIONS

We have shown a potential risk of spillover of sylvatic T. cruzi transmission to humans by oral and vectorial transmission in two BITER installations in Colombia. The results indicate that installations where 100,000 active military personnel carry out training activities should be prioritized for epidemiological surveillance of Chagas disease.

Trypanosomes of vectors and domestic dogs in Trypanosoma cruzi transmission areas from Brazilian southwestern amazon: New mammalian host for Trypanosoma janseni

Trypanosoma cruzi is a widespread protozoan in Latin America causing Chagas disease in humans and able to infect several other mammal species. The objective of this study was to investigate the T. cruzi infection in triatomine fauna as well as in dogs from distinct areas of Acre, western Brazilian Amazonia, which recently reported acute cases of human CD as well as an area that have not notify this disease recently. Triatomines were collected and the intestinal contents were evaluated for the presence of trypanosomatids by optical microscopy and polymerase chain reaction (PCR) targeting the mini-exon gene. Blood smear, hemoculture, PCR and serology were performed in the studied mammals. Fecal content of four triatomines were positive (11.6%) in the fresh examination. Molecular analysis identified Trypanosoma cruzi TCI in two specimens. Blood samples from 90 dogs were obtained. Trypanosoma sp. was observed in six blood smears (6/83, 7.22%). Seropositivity for T. cruzi was 8/89 (8.98). One dog's hemoculture was obtained and characterized as T. rangeli. PCR reactions in blood clots resulted in one positive dog (1/75, 1.3%) infected by T. janseni, providing a new mammalian host for a recently described Trypanosoma species. The results demonstrate the low exposition and prevalence for T. cruzi suggesting that dogs are not important to T. cruzi transmission cycle in the studied áreas.

Trypanosoma cruzi infection in domestic and synanthropic mammals such as potential risk of sylvatic transmission in a rural area from north of Antioquia, Colombia

In Colombia, dogs and opossum are the most important mammals in domestic and sylvatic T. cruzi transmission. However, the role of both species has not been evaluated in areas where both species converge in the peridomestic area. To evaluate the infection status of domestic and wild mammals in peridomestic habitats of Puerto Valdivia, Antioquia Department. The infection of domestic dogs and small wild mammals was performed by hemoculture, molecular and serological methods. Additionally, the infection in children under 15 years old and triatomine searches was carried out. We found that 16.07% and 34% dogs, and 59.1% and 61.1% Didelphis marsupialis were found positive by molecular and serological methods respectively. Moreover, in 25% and 75% of the infected dogs were detected TcI_Dom and TcI sylvatic, respectively, while all the D. marsupialis were infected with TcI. Six Rattus rattus and three Proechimys semispinosus were captured but without T. cruzi infection. Finally, none of the 82 children were positive and no triatomine bugs were captured. D. marsupialis and domestics dogs have an important role in the transmission of T. cruzi suggesting a potential risk in T. cruzi transitions areas.

Understanding the oral transmission of Trypanosoma cruzi as a veterinary and medical foodborne zoonosis

Chagas disease is a neglected tropical disease transmitted by the protozoan Trypanosoma cruzi that lately has been highlighted because several outbreaks attributed to oral transmission of the parasite have occurred. These outbreaks are characterized by high mortality rates and massive infections that cannot be related to other types of transmission such as the vectorial route. Oral transmission of Chagas disease has been reported in Brazil, Colombia, Venezuela, Bolivia, Ecuador, Argentina and French Guiana, most of them are massive oral outbreaks caused by the ingestion of beverages and food contaminated with triatomine feces or parasites' reservoirs secretions and considered since 2012 as a foodborne disease. In this review, we present the current status and all available data regarding oral transmission of Chagas disease, highlighting its relevance as a veterinary and medical foodborne zoonosis.

Rhodnius prolixus Colonization and Trypanosoma cruzi Transmission in Oil Palm (Elaeis guineensis) Plantations in the Orinoco Basin, Colombia

Trypanosoma cruzi is the etiological agent of Chagas disease that infects more than seven million people in Latin America. The parasite is transmitted by triatomine insects, of which some species are often associated with palms. The establishment of oil palm plantations (Elaeis guineensis) in the Orinoco region (Colombia) has been rapidly growing, possibly constituting a new environment for the establishment and increase in triatomine populations. In this study, the potential of Rhodnius prolixus to colonize E. guineensis plantations and maintain T. cruzi transmission was assessed. Fieldwork was conducted in two areas located in the department of Casanare for sampling E. guineensis and Attalea butyracea palms, sampling for triatomines to determine their abundance and prevalence of T. cruzi infection. To assess T. cruzi transmission potential in the area, sylvatic and domestic mammals were sampled. Results showed that palm infestation with triatomines was higher in A. butyracea than in E. guineensis palms and T. cruzi infection in triatomines varied between habitats for one study area, but was constant in the other site. Trypanosoma cruzi–infected mammals in the E. guineensis plantations were mainly generalist rodents, suggesting that these mammals could have an important role in T. cruzi transmission in plantations. In conclusion, E. guineensis plantations in the Orinoco region are suitable habitats for R. prolixus and T. cruzi transmission.

Trypanosoma cruzi circulating among dogs and triatomines in the endemic countryside of the State of Rio Grande do Norte, Brazil

Vector transmission of Trypanosoma cruzi occurs in several areas of Brazil, including the northeastern region, and domestic animals can serve as reservoirs of the parasite. The aim of this study was to monitor dogs as domestic reservoirs for infection by T. cruzi, and the main triatomine species involved in parasite transmission in rural areas of municipalities in the State of Rio Grande do Norte, in northeastern, Brazil. Blood samples from dogs (n = 40) and manual triatomine capture were performed in domiciliary and peridomiciliary environments in rural areas of the towns of Acari, Caraúbas and Marcelino Vieira, between 2013 and 2016. Subsequently, infection of dogs was determined by Polymerase Chain Reaction (PCR), Enzyme-Linked Immunosorbent Assay (ELISA) for the detection of IgM and IgG isotypes and Indirect Immunofluorescence (IIF) reactions for detection of IgG. Triatomine infection was determined by PCR. Forty (16/40) percent of the dogs were seropositive for T. cruzi; 20.0% (8/40) of such reactivity indicated the acute phase, and 20.0% (8/40), the chronic phase. PCR was positive in 42.5% (17/40) of the dogs' blood samples. Specimens of Triatoma brasiliensis, Triatoma pseudomaculata, Rhodnius nasutus and Panstrongylus lutzi were found to be infected; however only T. brasiliensis nymphs and adults were infected in both environments. Triatomines evaluation showed 82.5% (94/114) of PCR positivity. Taken together, our results confirm that dogs are domestic reservoirs of T. cruzi in northeastern Brazil and T. brasiliensis is the main triatomine species correlated with parasite transmission in domiciliary environments. There is a continuing need to control peridomiciliary populations of triatomines and to implement continuous surveillance strategies for reservoirs with the help from the community.

Disentangling Trypanosoma cruzi transmission cycle dynamics through the identification of blood meal sources of natural populations of Triatoma dimidiata in Yucatán, Mexico

Background

In the Yucatán Peninsula, Mexico, Triatoma dimidiata is the main vector of Trypanosoma cruzi, the causative agent of Chagas disease. Little effort has been made to identify blood meal sources of T. dimidiata in natural conditions in this region, although this provides key information to disentangle T. cruzi transmission cycles and dynamics and guide the development of more effective control strategies. We identified the blood meals of a large sample of T. dimidiata bugs collected in different ecotopes simultaneously with the assessment of bug infection with T. cruzi, to disentangle the dynamics of T. cruzi transmission in the region.

Methods

A sample of 248 T. dimidiata bugs collected in three rural villages and in the sylvatic habitat surrounding these villages was used. DNA from each bug midgut was extracted and bug infection with T. cruzi was assessed by PCR. For blood meal identification, we used a molecular assay based on cloning and sequencing following PCR amplification with vertebrate universal primers, and allowing the detection of multiple blood meals in a single bug.

Results

Overall, 28.7% of the bugs were infected with T. cruzi, with no statistical difference between bugs from the villages or from sylvatic ecotopes. Sixteen vertebrate species including domestic, synanthropic and sylvatic animals, were identified as blood meal sources for T. dimidiata. Human, dog and cow were the three main species identified, in bugs collected in the villages as well as in sylvatic ecotopes. Importantly, dog was highlighted as the main blood meal source after human. Dog was also the most frequently identified animal together with human within single bugs, and tended to be associated with the infection of the bugs.

Conclusions

Dog, human and cow were identified as the main mammals involved in the connection of sylvatic and domestic transmission cycles in the Yucatán Peninsula, Mexico. Dog appeared as the most important animal in the transmission pathway of T. cruzi to humans, but other domestic and synanthropic animals, which most were previously reported as important hosts of T. cruzi in the region, were evidenced and should be taken into account as part of integrated control strategies aimed at disrupting parasite transmission.

The triad "dogs, conservation and zoonotic diseases" - An old and still neglected problem in Brazil

The presence of domestic/free-ranging dogs in Brazilian protected areas and native vegetation fragments is an important problem, mainly because these animals pose a threat to wild species that live in such areas. In addition, dogs constantly circulate between wildlife environments and urban regions, acting as "bridges" in spillover events. Dogs are traditionally recognized as vectors of zoonoses, which are correct, but their roles as facilitating agents for the "jump" of pathogens from wild animals to humans (and vice versa) are sparsely debated. In this context, this work briefly describes the different roles of dogs in the dynamics and ecology of infectious diseases, using the Brazilian scenario as a study model.

Heterogeneity of Trypanosoma cruzi infection rates in vectors and animal reservoirs in Colombia: a systematic review and meta-analysis

Background

The heterogeneity of Trypanosoma cruzi infection rates among triatomines insects and animal reservoirs has been studied in independent studies, but little information has been systematised to allow pooled and comparative estimates. Unravelling the main patterns of this heterogeneity could contribute to a further understanding of T. cruzi transmission in Colombia.

Methods

A systematic search was conducted in PubMed, Medline, LILACS, Embase, Web of Knowledge, Google Scholar and secondary sources with no filters of language or time and until April 2018. Based on selection criteria, all relevant studies reporting T. cruzi infection rates in reservoirs or triatomines were chosen. For pooled analyses, a random effects model for binomial distribution was used. Heterogeneity among studies is reported as I². Subgroup analyses included: taxonomic classification, ecotope and diagnostic methods. Publication bias and sensitivity analyses were performed.

Results

Overall, 39 studies reporting infection rates in Colombia were found (22 for potential reservoirs and 28 for triatomine insects) for a total sample of 22,838 potential animals and 11,307 triatomines evaluated for T. cruzi infection. We have found evidence of 38/71 different animal species as potential T. cruzi reservoirs and 14/18 species as triatomine vectors for T. cruzi. Among animals, the species with the highest pooled prevalence were opossum (Didelphis marsupialis) with 48.0% (95% CI: 26–71%; I² = 88%, τ² = 0.07, P < 0.01) and domestic dog (Canis lupus familiaris) with 22.0% (95% CI: 4–48%; I² = 96%, τ² = 0.01, P < 0.01). Among triatomines, the highest prevalence was found for Triatoma maculata in the peridomestic ecotope (68.0%, 95% CI: 62–74%; I² = 0%, τ² = 0, P < 0.0001), followed by Rhodnius prolixus (62.0%, 95% CI: 38–84%; I² = 95%, τ² = 0.05, P < 0.01) and Rhodnius pallescens (54.0%, 95% CI: 37–71%; I² = 86%, τ² = 0.035, P < 0.01) in the sylvatic ecotope.

Conclusions

To our knowledge, this is the first systematic and quantitative analyses of triatomine insects and potential animal reservoirs for T. cruzi infection in Colombia. The results highlight a marked heterogeneity between species and provide initial estimates of infection rates heterogeneity.

Electronic supplementary material

The online version of this article (10.1186/s13071-019-3541-5) contains supplementary material, which is available to authorized users.

A review on the occurrence of companion vector-borne diseases in pet animals in Latin America

Companion vector-borne diseases (CVBDs) are an important threat for pet life, but may also have an impact on human health, due to their often zoonotic character. The importance and awareness of CVBDs continuously increased during the last years. However, information on their occurrence is often limited in several parts of the world, which are often especially affected. Latin America (LATAM), a region with large biodiversity, is one of these regions, where information on CVBDs for pet owners, veterinarians, medical doctors and health workers is often obsolete, limited or non-existent. In the present review, a comprehensive literature search for CVBDs in companion animals (dogs and cats) was performed for several countries in Central America (Belize, Caribbean Islands, Costa Rica, Cuba, Dominican Republic, El Salvador, Guatemala, Honduras, Mexico, Nicaragua, Panama, Puerto Rico) as well as in South America (Argentina, Bolivia, Brazil, Chile, Colombia, Ecuador, French Guiana, Guyana (British Guyana), Paraguay, Peru, Suriname, Uruguay, Venezuela) regarding the occurrence of the following parasitic and bacterial diseases: babesiosis, heartworm disease, subcutaneous dirofilariosis, hepatozoonosis, leishmaniosis, trypanosomosis, anaplasmosis, bartonellosis, borreliosis, ehrlichiosis, mycoplasmosis and rickettsiosis. An overview on the specific diseases, followed by a short summary on their occurrence per country is given. Additionally, a tabular listing on positive or non-reported occurrence is presented. None of the countries is completely free from CVBDs. The data presented in the review confirm a wide distribution of the CVBDs in focus in LATAM. This wide occurrence and the fact that most of the CVBDs can have a quite severe clinical outcome and their diagnostic as well as therapeutic options in the region are often difficult to access and to afford, demands a strong call for the prevention of pathogen transmission by the use of ectoparasiticidal and anti-feeding products as well as by performing behavioural changes.

Maintenance of Trypanosoma cruzi, T. evansi and Leishmania spp. by domestic dogs and wild mammals in a rural settlement in Brazil-Bolivian border

Domestic dogs are considered reservoirs hosts for several vector-borne parasites. This study aimed to evaluate the role of domestic dogs as hosts for Trypanosoma cruzi, Trypanosoma evansi and Leishmania spp. in single and co-infections in the Urucum settlement, near the Brazil-Bolivian border. Additionally, we evaluated the involvement of wild mammals’ in the maintenance of these parasites in the study area. Blood samples of dogs (n = 62) and six species of wild mammals (n = 36) were collected in July and August of 2015. The infections were assessed using parasitological, serological and molecular tests. Clinical examination of dogs was performed and their feeding habits were noted. Overall, 87% (54/62) of sampled dogs were positive for at least one trypanosomatid species, in single (n = 9) and co-infections (n = 45). We found that 76% of dogs were positive for T. cruzi, four of them displayed high parasitemias demonstrated by hemoculture, including one strain types TcI, two TcIII and one TcIII/TcV. Around 73% (45/62) of dogs were positive to T. evansi, three with high parasitemias as seen by positive microhematocrit centrifuge technique. Of dogs sampled, 50% (31/62) were positive for Leishmania spp. by PCR or serology. We found a positive influence of (i) T. evansi on mucous pallor, (ii) co-infection by T. cruzi and Leishmania with onychogryphosis, and (iii) all parasites to skin lesions of sampled dogs. Finally, feeding on wild mammals had a positive influence in the Leishmania spp. infection in dogs. We found that 28% (5/18) coati Nasua nasua was co-infected for all three trypanosamatids, demonstrating that it might play a key role in maintenance of these parasites. Our results showed the importance of Urucum region as a hotspot for T. cruzi, T. evansi and Leishmania spp. and demonstrated that dogs can be considered as incidental hosts.

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Observation of high occurrence of dogs co-infected by trypanosomatids.

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Dogs infected by TcI, TcIII and TcIII/TcV.

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Nasua nasua is a key species in the sylvatic cycles of trypanosomatids.

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Direct effect of trypanosomatids' infection in clinical signs of dogs.

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Dogs as sentinels to human infection in the Brazil-Bolivian border.

Considering Dogs as Complementary Targets of Chagas Disease Control

This review describes the role that dogs play in Latin American countries where Chagas disease is endemic. Multiple studies determined the high frequency with which canine populations are infected with Trypanosoma cruzi. The infection prevalence of dogs is greater than that of humans and the presence of infected dogs in households is associated with a higher risk of human infection. Dog infectiousness to triatomine vectors is several-fold higher than that of humans, thereby underscoring their major role in the domestic transmission of T. cruzi. Insecticide spraying of houses is in most cases efficacious but the lack of sustainability hinders this vector-focused strategy. Multi-pronged approaches have been adopted to improve control measures but dog intervention was never included. Experimental evaluation of systemic insecticides or deltamethrin-impregnated collars suggested that dog intervention leading to triatomine killing could curb domestic transmission of T. cruzi. Larger field studies are required to determine its applicability and efficacy. However, the implementation of dog intervention could complement other control measures currently in place, mostly in periods when vector spraying has been interrupted.

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

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

Identification of novel mammalian hosts and Brazilian biome geographic distribution of Trypanosoma cruzi TcIII and TcIV

Trypanosoma cruzi is a parasitic protozoan responsible for Chagas disease. Seven different Discrete Typing Units (DTUs) of T. cruzi are currently identified in nature: TcI-TcVI, and TcBat whose distribution patterns in nature, hosts/reservoirs and eco-epidemiological importance are still little known. Here, we present novel data on the geographic distribution and diversity of mammalian hosts and vectors of T. cruzi DTUs TcIII and TcIV. In this study, we analyzed 61 T. cruzi isolates obtained from 18 species of mammals (five orders) and two Hemiptera genera. Samples were collected from five Brazilian biomes (Pantanal, Caatinga, Cerrado, Atlantic Rainforest, and Amazon) previously characterized as Z3 or mixed infection (TcI-Z3) by mini-exon gene PCR. To identify TcIII and TcIV genotypes, we applied restriction fragment length polymorphism analysis to the PCR-amplified histone 3 gene. DTUs TcIII and TcIV were identified in single and mixed infections from wide dispersion throughout five Brazilian biomes studied, with TcIV being the most common. Pantanal was the biome that displayed the largest number of samples characterized as TcIII and TcIV in single and mixed infections, followed by Atlantic Rainforest and Amazon. Species from the Didelphimorphia order displayed the highest frequency of infection and were found in all five biomes. We report, for the first time, the infection of a species of the Artiodactyla order by DTU TcIII. In addition, we describe new host species: five mammals (marsupials and rodents) and two genera of Hemiptera. Our data indicate that DTUs TcIII and TcIV are more widespread and infect a larger number of mammalian species than previously thought. In addition, they are transmitted in restricted foci and cycles, but in different microhabitats and areas with distinct ecological profiles. Finally, we show that DTUs TcIII and TcIV do not present any specific association with biomes or host species.

Molecular and serological detection of Trypanosoma cruzi in dogs (Canis lupus familiaris) suggests potential transmission risk in areas of recent acute Chagas disease outbreaks in Colombia

Chagas disease is a zoonotic infection widely distributed in tropical and subtropical regions of America, including more than 50% of the Colombian territory. In the last years, an increase of outbreaks of acute Chagas disease has been observed in the east of the country due to environmental changes and mammal movements toward human settlements. Given the importance of dogs (Canis lupus familiaris) as reservoir hosts and sentinels of Trypanosoma cruzi infection across different regions of America, in this study we reported a serological and molecular detection of T. cruzi infection in 242 dogs from an endemic area of Meta department (East of Colombia), with recent emergence of acute Chagas disease outbreaks. The distribution of T. cruzi infection in dogs was not homogeneous, ranging from 0-41.4% and 0-5.1% in different sampling sectors, through serological (ELISA/IFAT) and molecular methods (conventional and real time PCR), respectively. Statistical analysis indicated that dog infection was associated with specific sampling sectors. Our results show a moderate seroprevalence of infection and active circulation of T. cruzi in dogs from this zone, which suggest areas with potential risk of infection to human that must be taken into consideration when Chagas disease control programs need to be implemented.

Epidemiology and Molecular Typing of Trypanosoma cruzi in Naturally-Infected Hound Dogs and Associated Triatomine Vectors in Texas, USA

BACKGROUND

Trypanosoma cruzi is the etiologic agent of Chagas disease throughout the Americas. Few population-level studies have examined the epidemiology of canine infection and strain types of T. cruzi that infect canines in the USA. We conducted a cross-sectional study of T. cruzi infection in working hound dogs in south central Texas, including analysis of triatomine vectors collected within kennel environments.

METHODOLOGY/PRINCIPLE FINDINGS

Paired IFA and Chagas Stat-Pak serological testing showed an overall seroprevalence of 57.6% (n = 85), with significant variation across kennels. Dog age had a marginally significant effect on seropositivity, with one year of age increase associated with a 19.6% increase in odds of being seropositive (odds ratio 95% CI 0.996-1.435; p = 0.055). PCR analyses of blood revealed 17.4% of dogs harbored parasite DNA in their blood, including both seronegative and seropositive dogs. Molecular screening of organs from opportunistically sampled seropositive dogs revealed parasite DNA in heart, uterus, and mammary tissues. Strain-typing showed parasite discrete typing units (DTU) TcI and TcIV present in dog samples, including a co-occurrence of both DTUs in two individual dogs. Bloodmeal analysis of Triatoma gerstaeckeri and Triatoma sanguisuga insects collected from the kennels revealed exclusively dog DNA. Vector infection with T. cruzi was 80.6% (n = 36), in which T. gerstaeckeri disproportionately harbored TcI (p = 0.045) and T. sanguisuga disproportionately harbored TcIV (p = 0.029). Tracing infection status across dog litters showed some seropositive offspring of seronegative dams, suggesting infection of pups from local triatomine vectors rather than congenital transmission.

CONCLUSIONS/SIGNIFICANCE

Canine kennels are high-risk environments for T. cruzi transmission, in which dogs likely serve as the predominant parasite reservoir. Disease and death of working dogs from Chagas disease is associated with unmeasured yet undoubtedly significant financial consequences because working dogs are highly trained and highly valued.

Trypanosoma cruzi diversity in infected dogs from areas of the north coast of Chile

As part of a multi-site research program on the eco-epidemiology and control of Chagas disease in northern Chile, we sought to identify the Trypanosoma cruzi discrete typing units (DTUs) infecting rural and peridomestic dogs, using direct methods without grown of the parasite in the laboratory and thus to assess the use of this species as a sentinel of the disease in well-defined endemic areas of T. cruzi in Chile. Infected dogs (35) from three villages were included in the study. The studied villages were Caleta Río Seco and Caleta San Marcos, both in the Tarapacá Region, and La Serena in the Coquimbo Region. These villages were selected based on previous evidence of Mepraia infection reports of the Chilean Ministry of Health. Amplicons from nested-PCR positive samples were used as targets to determine the infective T. cruzi DTUs circulating in blood using PCR-DNA blotting and hybridization assays with five specific DNA probes (TcI, TcII, TcIII, TcV and TcVI). Results of hybridization with dog samples from Caleta Rio Seco showed single infections in 2 out of 16 and mixed infections in 14 out of 16. TcVI was the most frequent DTU found in this area. A highlight is that for the first time the presence of TcIII is reported in this area. Samples from Caleta San Marcos showed single infections in 5 out of 9 and mixed infections in 4 out of 9. TcVI was the most frequent DTU found in this area. Samples from La Serena showed single infections in 5 out of 10 and mixed infections in 2 out of 10; we were unable to genotype the other 3 samples. Our results indicate that infection by T. cruzi DTUs in dogs is not homogeneously distributed but rather specific to each region of our country, as demonstrated by the differences in the T. cruzi DTU distribution in some localities.

Over Six Thousand Trypanosoma cruzi Strains Classified into Discrete Typing Units (DTUs): Attempt at an Inventory

Trypanosoma cruzi, the causative agent of Chagas disease, presents wide genetic diversity. Currently, six discrete typing units (DTUs), named TcI to TcVI, and a seventh one called TcBat are used for strain typing. Beyond the debate concerning this classification, this systematic review has attempted to provide an inventory by compiling the results of 137 articles that have used it. A total of 6,343 DTU identifications were analyzed according to the geographical and host origins. Ninety-one percent of the data available is linked to South America. This sample, although not free of potential bias, nevertheless provides today's picture of T. cruzi genetic diversity that is closest to reality. DTUs were genotyped from 158 species, including 42 vector species. Remarkably, TcI predominated in the overall sample (around 60%), in both sylvatic and domestic cycles. This DTU known to present a high genetic diversity, is very widely distributed geographically, compatible with a long-term evolution. The marsupial is thought to be its most ancestral host and the Gran Chaco region the place of its putative origin. TcII was rarely sampled (9.6%), absent, or extremely rare in North and Central America, and more frequently identified in domestic cycles than in sylvatic cycles. It has a low genetic diversity and has probably found refuge in some mammal species. It is thought to originate in the south-Amazon area. TcIII and TcIV were also rarely sampled. They showed substantial genetic diversity and are thought to be composed of possible polyphyletic subgroups. Even if they are mostly associated with sylvatic transmission cycles, a total of 150 human infections with these DTUs have been reported. TcV and TcVI are clearly associated with domestic transmission cycles. Less than 10% of these DTUs were identified together in sylvatic hosts. They are thought to originate in the Gran Chaco region, where they are predominant and where putative parents exist (TcII and TcIII). Trends in host-DTU specificities exist, but generally it seems that the complexity of the cycles and the participation of numerous vectors and mammal hosts in a shared area, maintains DTU diversity.

Shelter dogs as sentinels for Trypanosoma cruzi transmission across Texas

Chagas disease, an infection with the parasite Trypanosoma cruzi, is increasingly diagnosed among humans in the southern United States. We assessed exposure of shelter dogs in Texas to T. cruzi; seroprevalence across diverse ecoregions was 8.8%. Canine serosurveillance is a useful tool for public health risk assessment.

Human Trypanosomiasis in the Eastern Plains of Colombia: New Transmission Scenario

Characteristics of Trypanosoma cruzi infection were studied in a rural area of the eastern plains of Colombia. Using enzyme-linked immunosorbent assay and indirect fluorescent-antibody tests, the infection was determined in 11.6% of the inhabitants of 142 dwellings. During 6 months of community surveillance, in 42.3% dwellings, 609 triatomines were collected (597 Rhodnius prolixus and seven, three, one, and one of Panstrongylus geniculatus, Psammolestes arturi, Eratyrus mucronatus, and Triatoma maculata, respectively). Rhodnius prolixus was found in 80% peridomiciliary Attalea butyracea palms examined with baited traps, and its infection with T. cruzi was 30% and 38.5% in dwellings and palms, respectively. Trypanosoma cruzi was isolated in five of 35 triatomines and in one of 24 dogs. The blood of domestic and wild animals was identified in triatomines collected in the intradomicile and in palms. These results support the extension of the wild cycle of T. cruzi to human dwellings and the characterization of a new scenario for transmission in Colombia.

Reservoir host competence and the role of domestic and commensal hosts in the transmission of Trypanosoma cruzi

We review the epidemiological role of domestic and commensal hosts of Trypanosoma cruzi using a quantitative approach, and compiled >400 reports on their natural infection. We link the theory underlying simple mathematical models of vector-borne parasite transmission to the types of evidence used for reservoir host identification: mean duration of infectious life; host infection and infectiousness; and host-vector contact. The infectiousness of dogs or cats most frequently exceeded that of humans. The host-feeding patterns of major vectors showed wide variability among and within triatomine species related to their opportunistic behavior and variable ecological, biological and social contexts. The evidence shows that dogs, cats, commensal rodents and domesticated guinea pigs are able to maintain T. cruzi in the absence of any other host species. They play key roles as amplifying hosts and sources of T. cruzi in many (peri)domestic transmission cycles covering a broad diversity of ecoregions, ecotopes and triatomine species: no other domestic animal plays that role. Dogs comply with the desirable attributes of natural sentinels and sometimes were a point of entry of sylvatic parasite strains. The controversies on the role of cats and other hosts illustrate the issues that hamper assessing the relative importance of reservoir hosts on the basis of fragmentary evidence. We provide various study cases of how eco-epidemiological and genetic-marker evidence helped to unravel transmission cycles and identify the implicated hosts. Keeping dogs, cats and rodents out of human sleeping quarters and reducing their exposure to triatomine bugs are predicted to strongly reduce transmission risks.

Geospatial Risk Factors of Canine American Trypanosomiasis (Chagas Disease) (42 Cases: 2000-2012)

American trypanosomiasis or Chagas disease caused by Trypanosoma cruzi affects many mammals, including humans and dogs, in all Latin American countries outside the Caribbean and increasingly also in the southern United States. Dogs are considered as reliable sentinels and have been identified as an important risk factor for the disease in humans in endemic countries. Factors that determine American trypanosomiasis in dogs may therefore have public health relevance. Associations of different environmental, locational, and pet owner socioeconomic conditions were evaluated retrospectively as potential risk factors for American trypanosomiasis status in dogs in a case-control study. Laboratory-confirmed cases received at the Texas A&M University Veterinary Medical Teaching Hospital between the years 2000 and 2012 and candidate risk factor variables extracted from publicly available environmental data and 2010 US Census Bureau were used. The sample included 42 dogs serologically positive and 82 dogs serologically negative determined by indirect immunofluorescent assay. The diagnostic titer was 1:160 (case). Univariate logistic regressions followed by stepwise multivariate logistic modeling were used for variable screening and to determine the strengths of variable associations with case status. Total Edge Contrast Index (odds ratio [OR] = 3.35, 95% confidence interval [CI] 3.10, 3.62), residing in homes that had rural addresses (OR = 2.48, 95% CI 2.43, 2.53), total number of owner occupied housing units in a neighborhood with a householder who is Hispanic or Latino (OR = 1.66, 95% CI 1.04, 2.66), and the total number of housing units in a neighborhood that were built on or prior to year 1980 (OR = 2.22, 95% CI 1.94, 2.55) were identified as risk factors. Suitable awareness campaigns and future research that considers pet owner housing and socioeconomic circumstances are necessary for effective prevention and control of this disease among dogs.

Eco-epidemiological study of an endemic Chagas disease region in northern Colombia reveals the importance of Triatoma maculata (Hemiptera: Reduviidae), dogs and Didelphis marsupialis in Trypanosoma cruzi maintenance

BACKGROUND

In Colombia, Rhodnius prolixus and Triatoma dimidiata are the main domestic triatomine species known to transmit T. cruzi. However, there are multiple reports of T. cruzi transmission involving secondary vectors. In this work, we carried out an eco-epidemiological study on Margarita Island, located in the Caribbean region of Colombia, where Chagas disease is associated with non-domiciliated vectors.

METHODS

To understand the transmission dynamics of Trypanosoma cruzi in this area, we designed a comprehensive, multi-faceted study including the following: (i) entomological evaluation through a community-based insect-surveillance campaign, blood meal source determination and T. cruzi infection rate estimation in triatomine insects; (ii) serological determination of T. cruzi prevalence in children under 15 years old, as well as in domestic dogs and synanthropic mammals; (iii) evaluation of T. cruzi transmission capacity in dogs and Didelphis marsupialis, and (iv) genetic characterization of T. cruzi isolates targeting spliced-leader intergene region (SL-IR) genotypes.

RESULTS

Out of the 124 triatomines collected, 94% were Triatoma maculata, and 71.6% of them were infected with T. cruzi. Blood-meal source analysis showed that T. maculata feeds on multiple hosts, including humans and domestic dogs. Serological analysis indicated 2 of 803 children were infected, representing a prevalence of 0.25%. The prevalence in domestic dogs was 71.6% (171/224). Domestic dogs might not be competent reservoir hosts, as inferred from negative T. cruzi xenodiagnosis and haemoculture tests. However, 61.5% (8/13) of D. marsupialis, the most abundant synanthropic mammal captured, were T. cruzi-positive on xenodiagnosis and haemocultures.

CONCLUSIONS

This study reveals the role of peridomestic T. maculata and dogs in T. cruzi persistence in this region and presents evidence that D. marsupialis are a reservoir mediating peridomestic-zoonotic cycles. This picture reflects the complexity of the transmission dynamics of T. cruzi in an endemic area with non-domiciliated vectors where active human infection exists. There is an ongoing need to control peridomestic T. maculata populations and to implement continuous reservoir surveillance strategies with community participation.

Retrospective distribution of Trypanosoma cruzi I genotypes in Colombia

Trypanosoma cruzi is the aetiological agent of Chagas disease, which affects approximately eight million people in the Americas. This parasite exhibits genetic variability, with at least six discrete typing units broadly distributed in the American continent. T. cruzi I (TcI) shows remarkable genetic diversity; a genotype linked to human infections and a domestic cycle of transmission have recently been identified, hence, this strain was named TcIDom. The aim of this work was to describe the spatiotemporal distribution of TcI subpopulations across humans, insect vectors and mammalian reservoirs in Colombia by means of molecular typing targeting the spliced leader intergenic region of mini-exon gene. We analysed 101 TcI isolates and observed a distribution of sylvatic TcI in 70% and TcIDom in 30%. In humans, the ratio was sylvatic TcI in 60% and TcIDom in 40%. In mammal reservoirs, the distribution corresponded to sylvatic TcI in 96% and TcIDom in 4%. Among insect vectors, sylvatic TcI was observed in 48% and TcIDom in 52%. In conclusion, the circulation of TcIDom is emerging in Colombia and this genotype is still adapting to the domestic cycle of transmission. The epidemiological and clinical implications of these findings are discussed herein.

Distantiae transmission of Trypanosoma cruzi: a new epidemiological feature of acute Chagas disease in Brazil

BACKGROUND

The new epidemiological scenario of orally transmitted Chagas disease that has emerged in Brazil, and mainly in the Amazon region, needs to be addressed with a new and systematic focus. Belém, the capital of Pará state, reports the highest number of acute Chagas disease (ACD) cases associated with the consumption of açaí juice.

METHODOLOGY/PRINCIPAL FINDINGS

The wild and domestic enzootic transmission cycles of Trypanosoma cruzi were evaluated in the two locations (Jurunas and Val-de Cães) that report the majority of the autochthonous cases of ACD in Belém city. Moreover, we evaluated the enzootic cycle on the three islands that provide most of the açaí fruit that is consumed in these localities. We employed parasitological and serological tests throughout to evaluate infectivity competence and exposure to T. cruzi. In Val-de-Cães, no wild mammal presented positive parasitological tests, and 56% seroprevalence was observed, with low serological titers. Three of 14 triatomines were found to be infected (TcI). This unexpected epidemiological picture does not explain the high number of autochthonous ACD cases. In Jurunas, the cases of ACD could not be autochthonous because of the absence of any enzootic cycle of T. cruzi. In contrast, in the 3 island areas from which the açaí fruit originates, 66.7% of wild mammals and two dogs displayed positive hemocultures, and 15.6% of triatomines were found to be infected by T. cruzi. Genotyping by mini-exon gene and PCR-RFLP (1f8/Akw21I) targeting revealed that the mammals and triatomines from the islands harbored TcI and Trypanosoma rangeli in single and mixed infections.

CONCLUSION/SIGNIFICANCE

These findings show that cases of Chagas disease in the urban area of Belém may be derived from infected triatomines coming together with the açaí fruits from distant islands. We term this new epidemiological feature of Chagas disease as "Distantiae transmission".

High levels of Trypanosoma cruzi DNA determined by qPCR and infectiousness to Triatoma infestans support dogs and cats are major sources of parasites for domestic transmission

The competence of reservoir hosts of vector-borne pathogens is directly linked to its capacity to infect the vector. Domestic dogs and cats are major domestic reservoir hosts of Trypanosoma cruzi, and exhibit a much higher infectiousness to triatomines than seropositive humans. We quantified the concentration of T. cruzi DNA in the peripheral blood of naturally-infected dogs and cats (a surrogate of intensity of parasitemia), and evaluated its association with infectiousness to the vector in a high-risk area of the Argentinean Chaco. To measure infectiousness, 44 infected dogs and 15 infected cats were each exposed to xenodiagnosis with 10-20 uninfected, laboratory-reared Triatoma infestans that blood-fed to repletion and were later individually examined for infection by optical microscopy. Parasite DNA concentration (expressed as equivalent amounts of parasite DNA per mL, Pe/mL) was estimated by real-time PCR amplification of the nuclear satellite DNA. Infectiousness increased steeply with parasite DNA concentration both in dogs and cats. Neither the median parasite load nor the mean infectiousness differed significantly between dogs (8.1Pe/mL and 48%) and cats (9.7Pe/mL and 44%), respectively. The infectiousness of dogs was positively and significantly associated with parasite load and an index of the host's body condition, but not with dog's age, parasite discrete typing unit and exposure to infected bugs in a random-effects multiple logistic regression model. Real-time PCR was more sensitive and less time-consuming than xenodiagnosis, and in conjunction with the body condition index, may be used to identify highly infectious hosts and implement novel control strategies.

Parasite zoonoses and wildlife: One Health, spillover and human activity

This review examines parasite zoonoses and wildlife in the context of the One Health triad that encompasses humans, domestic animals, wildlife and the changing ecosystems in which they live. Human (anthropogenic) activities influence the flow of all parasite infections within the One Health triad and the nature and impact of resulting spillover events are examined. Examples of spillover from wildlife to humans and/or domestic animals, and vice versa, are discussed, as well as emerging issues, particularly the need for parasite surveillance of wildlife populations. Emphasis is given to Trypanosoma cruzi and related species in Australian wildlife, Trichinella, Echinococcus, Giardia, Baylisascaris, Toxoplasma and Leishmania.

Temporal variation of Trypanosoma cruzi discrete typing units in asymptomatic Chagas disease patients

Chagas disease caused by Trypanosoma cruzi is a public health problem in Latin America. This parasite displays a high genetic diversity evidenced in six Discrete Typing Units (DTUs) namely TcI-TcVI. The aim of this study was to observe the temporal variation of the DTUs in asymptomatic patients at three different times (10 days interval). The results showed that intermittence is the rule in the bloodstream of Chagas disease patients. The patients showed different detectable DTUs with short time intervals, which favors the clonal histiotropic model and the multiclonality structure of this parasite.

Detection of Trypanosoma cruzi infection in naturally infected dogs and cats using serological, parasitological and molecular methods

Domestic dogs and cats are major domestic reservoir hosts of Trypanosoma cruzi and a risk factor for parasite transmission. In this study we assessed the relative performance of a polymerase chain reaction assay targeted to minicircle DNA (kDNA-PCR) in reference to conventional serological tests, a rapid dipstick test and xenodiagnosis to detect T. cruzi infection in dogs and cats from an endemic rural area in northeastern Argentina. A total of 43 dogs and 13 cats seropositive for T. cruzi by an immunosorbent assay (ELISA) and an indirect hemagglutination assay (IHA), which had been examined by xenodiagnosis, were also tested by kDNA-PCR. kDNA-PCR was nearly as sensitive as xenodiagnosis for detecting T. cruzi-infectious dogs and cats. kDNA-PCR was slightly more sensitive than xenodiagnosis in seropositive dogs (91% versus 86%, respectively) and cats (77% against 54%, respectively), but failed to detect all of the seropositive individuals. ELISA and IHA detected all xenodiagnosis-positive dogs and both outcomes largely agreed (kappa coefficient, κ=0.92), whereas both assays failed to detect all of the xenodiagnosis-positive cats and their agreement was moderate (κ=0.68). In dogs, the sensitivity of the dipstick test was 95% and agreed closely with the outcome of conventional serological tests (κ=0.82). The high sensitivity of kDNA-PCR to detect T. cruzi infections in naturally infected dogs and cats supports its application as a diagnostic tool complementary to serology and may replace the use of xenodiagnosis or hemoculture.