The identification of two Trypanosoma cruzi I genotypes from domestic and sylvatic transmission cycles in Colombia based on a single polymerase chain reaction amplification of the spliced-leader intergenic region

A single polymerase chain reaction (PCR) reaction targeting the spliced-leader intergenic region of Trypanosoma cruzi I was standardised by amplifying a 231 bp fragment in domestic (TcI_DOM) strains or clones and 450 and 550 bp fragments in sylvatic strains or clones. This reaction was validated using 44 blind coded samples and 184 non-coded T. cruzi I clones isolated from sylvatic triatomines and the correspondence between the amplified fragments and their domestic or sylvatic origin was determined. Six of the nine strains isolated from acute cases suspected of oral infection had the sylvatic T. cruzi I profile. These results confirmed that the sylvatic T. cruzi I genotype is linked to cases of oral Chagas disease in Colombia. We therefore propose the use of this novel PCR reaction in strains or clones previously characterised as T. cruzi I to distinguish TcI_DOMfrom sylvatic genotypes in studies of transmission dynamics, including the verification of population selection within hosts or detection of the frequency of mixed infections by both T. cruzi I genotypes in Colombia.     

Prevalence and distribution of parasites and pathogens of Triatominae from Argentina, with emphasis on Triatoma infestans and Triatoma virus TrV

Chagas’ disease is the most important endemic arthropod-zoonosis in Argentina with an estimated 1.6 million people infected with the causative agent Trypanosoma cruzi. Triatoma infestans is the main vector of Chagas’ disease in Argentina. A survey for parasites and pathogens of Triatominae was conducted from August 2002 to February 2005. Collections of insects were made in domiciles, peridomiciles, and in the natural habitats of the Triatominae. Insects from these collections were dissected and their organs and tissues examined for flagellates. Frass from these insects was collected and examined for detection of the entomopathogenic virus Triatoma virus (TrV) using AC-ELISA and PCR. Triatominae belonging to four species, T. infestans (n = 1646), Triatoma guasayana (n = 4), Triatoma platensis (n = 1) and Triatoma sordida (n = 5) were collected from 62 sites located in 13 provinces of Argentina. Triatoma virus and two protozoan species, Blastocrithidia triatomae and T. cruzi, the etiological agent of Chagas disease, were found infecting Triatominae. The total prevalence of TrV in 1646 T. infestans analyzed by ELISA was 9.66% (159/1646) from 7 to 13 provinces where collections were made. Triatoma virus positive triatomines were found in 17 of 62 populations when examined by AC-ELISA but in 38 of 62 populations when PCR was used for detection. The prevalence of B. triatomae in T. infestans was 0.43% (7/1646), while the prevalence of T. cruzi was 1.3% (21/1646). This is the first study on the diversity, distribution and prevalence of flagellated protozoa and TrV of Triatominae in endemic Chagas’ disease regions of Argentina.     

Trypanosoma cruzi: Biological characterization of lineages I and II supports the predominance of lineage I in Colombia

The causes of the particular distribution of both Trypanosoma cruzi lineages throughout the American continent remain unknown. In Colombia, T. cruzi I is the predominant group in both domestic and sylvatic cycles. Here, we present the biological characterization of T. cruzi parasites belonging to both T. cruzi I and T. cruzi IIb groups. Our results show the inability of the T. cruzi IIb clones to infect mammalian cells, produce trypomastigotes and replicate in Rhodnius prolixus, the main vector species in this country. Moreover, this result was confirmed when other species from the same genus, such as R. pallescens and R. robustus, were infected with the same TcIIb clone and its parental strain, while the infection in other genera such as Triatoma and Panstrongylus was successful. Furthermore, the growth kinetics and duplication time in vitro suggest that the high prevalence of T. cruzi I in Colombia results from more successful interactions between parasite lineage, vector, and host species. This type of study may help to understand the factors influencing the particular epidemiological patterns of Chagas disease transmission in different endemic regions.     

Trypanosoma cruzi: variability of stocks from Colombia determined by molecular karyotype and minicircle Southern blot analysis

Nineteen Trypanosoma cruzi stocks, most of them of wild origin, and four Trypanosoma rangeli stocks from Colombia were analysed by molecular karyotype analysis with cloned DNA cruzipain as the probe. Another 27 cloned stocks of T. cruzi from different geographic areas of South America were used as reference for T. cruzi lineages. Phenetic analysis of chromosome size polymorphism demonstrated a great variability of Colombian T. cruzi stocks, suggesting that most belong to lineage I, although two of them belong to lineage II. The 2 lineage II T. cruzi, 17 T. cruzi lineage I, and 3 T. rangeli stocks from Colombia were studied further by Southern blot analysis with a panel of kinetoplast DNA minicircle probes. Hybridisation results indicate that the two T. cruzi II stocks are genetically distant from each other and from T. cruzi lineages IIb, IId, and IIe from Chile. Finally, T. cruzi minicircle probes do not cross-hybridise in any stringency condition tested with T. rangeli minicircles, a clear indication that these parasites can be easily distinguished by this method.     

The impact of climate change on the geographical distribution of two vectors of Chagas disease: implications for the force of infection

Chagas disease, caused by the parasite Trypanosoma cruzi, is the most important vector-borne disease in Latin America. The vectors are insects belonging to the Triatominae (Hemiptera, Reduviidae), and are widely distributed in the Americas. Here, we assess the implications of climatic projections for 2050 on the geographical footprint of two of the main Chagas disease vectors: Rhodnius prolixus (tropical species) and Triatoma infestans (temperate species). We estimated the epidemiological implications of current to future transitions in the climatic niche in terms of changes in the force of infection (FOI) on the rural population of two countries: Venezuela (tropical) and Argentina (temperate). The climatic projections for 2050 showed heterogeneous impact on the climatic niches of both vector species, with a decreasing trend of suitability of areas that are currently at high-to-moderate transmission risk. Consequently, climatic projections affected differently the FOI for Chagas disease in Venezuela and Argentina. Despite the heterogeneous results, our main conclusions point out a decreasing trend in the number of new cases of Tr. cruzi human infections per year between current and future conditions using a climatic niche approach.     

Trypanosoma cruzi I genotypes in different geographical regions and transmission cycles based on a microsatellite motif of the intergenic spacer of spliced-leader genes

The intergenic region of spliced-leader (SL-IR) genes from 105 Trypanosoma cruzi I (Tc I) infected biological samples, culture isolates and stocks from 11 endemic countries, from Argentina to the USA were characterised, allowing identification of 76 genotypes with 54 polymorphic sites from 123 aligned sequences. On the basis of the microsatellite motif proposed by Herrera et al. (2007) to define four haplotypes in Colombia, we could classify these genotypes into four distinct Tc I SL-IR groups, three corresponding to the former haplotypes Ia (11 genotypes), Ib (11 genotypes) and Id (35 genotypes); and one novel group, Ie (19 genotypes). Genotypes harbouring the Tc Ic motif were not detected in our study. Tc Ia was associated with domestic cycles in southern and northern South America and sylvatic cycles in Central and North America. Tc Ib was found in all transmission cycles from Colombia. Tc Id was identified in all transmission cycles from Argentina and Colombia, including Chagas cardiomyopathy patients, sylvatic Brazilian samples and human cases from French Guiana, Panama and Venezuela. Tc Ie gathered five samples from domestic Triatoma infestans from northern Argentina, nine samples from wild Mepraia spinolai and Mepraia gajardoi and two chagasic patients from Chile and one from a Bolivian patient with chagasic reactivation. Mixed infections by Tc Ia + Tc Id, Tc Ia + Tc Ie and Tc Id + Tc Ie were detected in vector faeces and isolates from human and vector samples. In addition, Tc Ia and Tc Id were identified in different tissues from a heart transplanted Chagas cardiomyopathy patient with reactivation, denoting histotropism. Trypanosoma cruzi I SL-IR genotypes from parasites infecting Triatoma gerstaeckeri and Didelphis virginiana from USA, T. infestans from Paraguay, Rhodnius nasutus and Rhodnius neglectus from Brazil and M. spinolai and M. gajardoi from Chile are to our knowledge described for the first time.     

Triatominae in furnariid nests of the Argentine Gran Chaco

Triatomines (Hemiptera, Reduviidae) are bloodsucking insects involved in the transmission of Trypanosoma cruzi, the causative agent of Chagas disease, an important public health problem in Latin America. The triatomine species found in sylvatic habitats generally play a limited epidemiological role compared to domestic species, but they may act as a reinfestation source of dwellings after insecticide spraying and have to be carefully considered in control strategies of Chagas disease transmission. The objectives of this work were to carry out a survey of the sylvatic triatomine species colonizing Furnariidae nests in a typical area of the Chaco region of Argentina during the winter and to study the parasites and natural enemies associated with the collected triatomines. Sixty‐three triatomine specimens were collected from Furnariidae nests (Coryphistera alaudina and Phacellodomus sibilatrix) randomly selected within the study area. Fifty‐four were identified as Psammolestes coreodes, seven as Triatoma platensis, and two as Triatoma infestans. Specimens of T. infestans and T. platensis were found in one nest. The first finding of instar nymphs of T. infestans x T. platensis in a sylvatic habitat is reported. For the first time, sylvatic collected specimens of T. platensis were found infected by T. cruzi. Triatoma virus was found in one Ps. coreodes specimen.     

Risk factors associated with Trypanosoma cruzi exposure in domestic dogs from a rural community in Panama

Chagas disease, caused by Trypanosoma cruzi infection, is a zoonosis of humans, wild and domestic mammals, including dogs. In Panama, the main T. cruzi vector is hodnius pallescens, a triatomine bug whose main natural habitat is the royal palm, Attalea butyracea. In this paper, we present results from three T. cruzi serological tests (immunochromatographic dipstick, indirect immunofluorescence and ELISA) performed in 51 dogs from 24 houses in Trinidad de Las Minas, western Panama. We found that nine dogs were seropositive (17.6% prevalence). Dogs were 1.6 times more likely to become T. cruzi seropositive with each year of age and 11.6 times if royal palms where present in the peridomiciliary area of the dog''s household or its two nearest neighbours. Mouse-baited-adhesive traps were employed to evaluate 12 peridomestic royal palms. All palms were found infested with R. pallescens with an average of 25.50 triatomines captured per palm. Of 35 adult bugs analysed, 88.6% showed protozoa flagellates in their intestinal contents. In addition, dogs were five times more likely to be infected by the presence of an additional domestic animal species in the dog''s peridomiciliary environment. Our results suggest that interventions focused on royal palms might reduce the exposure to T. cruzi infection.     

Trypanosoma cruzi: Multiplex PCR to detect and classify strains according to groups I and II

A multiplex PCR was developed for simultaneous detection of Trypanosoma cruzi DNA and classification of the parasite strain into groups I and II. As little as 10 fg of T. cruzi DNA could be detected by multiplex PCR. The technique was shown to be specific for T. cruzi DNA, since no PCR amplification products were obtained with DNA from other tripanosomatid species. Multiplex PCR was validated by assaying genomic DNA from 34 strains of T. cruzi that had been previously characterized; 24 blood samples from experimentally-infected mice and non-infected controls; 20 buffy coat samples from patients in the acute phase of Chagas disease and non-infected individuals, and 15 samples of feces from naturally-infected Triatoma infestans. T. cruzi samples from patients and from Y strain-infected mice were classified by multiplex PCR as T. cruzi II and samples from T. infestans and Colombiana strain-infected mice as T. cruzi I.     

Hosts and habitats of Trichinella spiralis and Trichinella britovi in Europe

Trichinella spiralis and Trichinella britovi are the two most common species of Trichinella circulating in Europe. Based on data provided to the International Trichinella Reference Centre over the past 20 years (data referring to 540 isolates of T. spiralis and 776 isolates of T. britovi), we describe the host species and habitat characteristics for these two pathogens in Europe. A Geographical Information System was constructed using administrative boundaries, a Corine Land Cover (CLC) map, and an elevation map. In most countries, T. britovi is more widespread (62.5-100% of the isolates) than T. spiralis (0.0-37.5%), although in Finland, Germany, Poland and Spain, T. spiralis is more prevalent (56.3-84.2% of the isolates). Trichinella britovi is more widespread than T. spiralis in sylvatic carnivores (89% versus 11%), whereas T. spiralis is prevalent in both wild boars (62% versus 38%) and domestic swine (82% versus 18%), as well as in rodents (75% versus 25%). Trichinella spiralis and T. britovi circulate in the same environments: 41.1% and 46.0%, respectively, in agricultural areas, and 45.5% and 46.6% in forested and semi-natural areas. Although both pathogens can be transmitted by domestic and sylvatic cycles, their epidemiology is strongly influenced by the higher adaptability of T. spiralis to swine and of T. britovi to carnivores. These results are important because they include information on the countries at risk for these pathogens, the role played by specific species as reservoirs, the role of the pathogens in domestic and sylvatic cycles, and the role of the habitat in their circulation. The results can also be used to identify the most suitable animal species for the monitoring of these pathogens in Europe.     

Within-host dynamics of Trichinella spiralis predict persistent parasite transmission in rat populations

Trichinella spiralis is transmitted and maintained in both a domestic and sylvatic cycle, whereby rats contribute to the spread of T. spiralis from domestic to sylvatic animals and vice versa. As a model for T. spiralis transmission in wildlife, we studied the potential of rats to act as a reservoir species for T. spiralis, by assessing experimentally its within-host infection dynamics, and simulating the between-host dynamics by a Monte Carlo approach. The distribution of parasite burden in individual rats is mathematically defined by roots of the dose response equation intersecting with the diagonal. In simulated between-host dynamics, up to 10⁴ events of uninterrupted parasite transmission were observed. Histograms of parasite burdens per individual rat matched closely with the mixture of two gamma distributions, which were derived from the within-host infection dynamics. In conclusion, T. spiralis transmission persists in a population of rats when they cannibalize their own species. Rats should be included in the minimal set of wildlife species that maintain the life cycle of T. spiralis.     

Trypanosoma cruzi from the Paraguayan Chaco: Isoenzyme Profiles of Strains Isolated at Makthlawaiya1

At Makthlawaiya, in the Paraguayan Chaco, the prevalence of Trypanosoma (Schizotrypanum) cruzi infection among both domestic Triatoma infestans and domestic dogs was 38%, and IgG anti-T. cruzi antibody was detected by the quantitative enzyme-linked immunosorbent assay (ELISA) in 80% (105/133) of human sera. Ninety percent (25/28) of T. cruzi strains isolated from both T. infestans and dogs showed heterozygous isoenzyme profiles for glucose phosphate isomerase, phosphoglucomutase and 6-phosphogluconate dehydrogenase. These strains appeared to be closely related to Bolivian zymodeme 2. Three Paraguayan T. cruzi strains showed homozygous isoenzyme profiles, similar to those of major Brazilian zymodemes. It was concluded that T. cruzi strains with heterozygous isoenzyme profiles predominate in domestic transmission cycles in this highly endemic area of the Paraguayan Chaco.     

Extraordinary Trypanosoma cruzi diversity within single mammalian reservoir hosts implies a mechanism of diversifying selection

Trypanosoma cruzi is an evolutionarily ancient parasitic protozoan endemic to the Americas. Multiple genetic and phenotypic markers indicate that this parasite is highly diverse, with several divergent and discrete major genotypes reported. Infection multiclonality has been observed among numerous metazoan and unicellular endoparasitic species. However, few studies report the complexity of mixed infections within an individual host in any detail or consider their ecological and biological implications. Here we report extraordinary genetic diversity within single reservoir hosts of T. cruzi I using nine polymorphic microsatellite markers across 211 clones from eight mammals from three different sylvatic foci in South America. Forty-nine distinct multilocus genotypes were defined, with as many as 10 isolated from the same host. We discuss our data in the light of previous population genetic studies of this and related parasitic protozoa and contrast high levels of diversity within each host with the precarious nature of T. cruzi contaminative vectorial transmission. Finally, we propose that non-neutral processes could easily account for the diversity we observe and suggest a functional link with survival in the host.     

A new method for forensic DNA analysis of the blood meal in chagas disease vectors demonstrated using Triatoma infestans from Chuquisaca, Bolivia

Background

Feeding patterns of the vector are important in the epidemiology of Chagas disease, the leading cause of heart disease in Latin America. Chagas disease is caused by the parasite, Trypanasoma cruzi, which is transmitted by blood feeding insects. Historically, feeding behaviours of haematophagous insects have been investigated using serological reactions, which have detection limits in terms of both taxonomic resolution, and quantity and quality of the blood meal. They are labor intensive, require technical expertise, need fresh or frozen samples and antibodies often are either not available commercially or the resources for synthesis and purification are not available. We describe an assay to identify vertebrate blood meal sources, and the parasite T. cruzi using species-specific PCR assays from insect vectors and use the method to provide information regarding three questions: (1) Do domestic and peri-domestic (chicken coop and animal corral) habitats vary in the blood meals detected in the vectors? (2) What is the pattern of multiple blood meals? (3) Does the rate of T. cruzi infection vary among habitats and is it associated with specific blood meal types?

Methodology/Principal Findings

Assays based on the polymerase chain reaction were evaluated for identification of the blood meal source in the heamatophagous Chagas disease vector Triatoma infestans. We evaluate a technique to identify 11 potential vertebrate food sources from the complex mixture extracted from the vector''s abdomen. We tested the assay on 81 T. infestans specimens collected from the Andean highlands in the department of Chuquisaca, located in central Bolivia, one of the regions in South America where sylvatic T. infestans have been reported. This area is suggested to be the geographic origin of T. infestans and has very high human infection rates that may be related to sylvatic vector populations.

Conclusion/Significance

The results of the assays revealed that a high percentage of insects collected in human dwellings had fed on peri-domestic animals. In contrast, one insect from a chicken coop but no bugs from corrals tested positive for human blood. Forty-eight percent of insects tested positive for more than one vertebrate species. T. cruzi infection was detected in 42% of the specimens. From the epidemiological point of view, the results reveal an overall pattern of movement from peri-domestic structures to human habitations for T. infestans in this region of Bolivia as well as the important role of pigs, dogs, chickens and guinea pigs in the dynamics of T. cruzi infection.     

Trypanosoma cruzi in Brazilian Amazonia: Lineages TCI and TCIIa in wild primates, Rhodnius spp. and in humans with Chagas disease associated with oral transmission

In this study, we provide phylogenetic and biogeographic evidence that the Trypanosoma cruzi lineages T. cruzi I (TCI) and T. cruzi IIa (TCIIa) circulate amongst non-human primates in Brazilian Amazonia, and are transmitted by Rhodnius species in overlapping arboreal transmission cycles, sporadically infecting humans. TCI presented higher prevalence rates, and no lineages other than TCI and TCIIa were found in this study in wild monkeys and Rhodnius from the Amazonian region. We characterised TCI and TCIIa from wild primates (16 TCI and five TCIIa), Rhodnius spp. (13 TCI and nine TCIIa), and humans with Chagas disease associated with oral transmission (14 TCI and five TCIIa) in Brazilian Amazonia. To our knowledge, TCIIa had not been associated with wild monkeys until now. Polymorphisms of ssrDNA, cytochrome b gene sequences and randomly amplified polymorphic DNA (RAPD) patterns clearly separated TCIIa from TCIIb-e and TCI lineages, and disclosed small intra-lineage polymorphisms amongst isolates from Amazonia. These data are important in understanding the complexity of the transmission cycles, genetic structure, and evolutionary history of T. cruzi populations circulating in Amazonia, and they contribute to both the unravelling of human infection routes and the pathological peculiarities of Chagas disease in this region.     

The peri-urban interface and house infestation with Triatoma infestans in the Argentine Chaco: an underreported process?

Peri-urban infestations with triatomine bugs, their sources and their dynamics have rarely been investigated. Here, we corroborated the reported occurrence of Triatoma infestans in a peri-urban area and in neighbouring rural houses in Pampa del Indio, in the Argentine Chaco, and identified its putative sources using spatial analysis and demographic questionnaires. Peri-urban householders reported that 10% of their premises had triatomines, whereas T. infestans was collected by timed manual searches or community-based surveillance in only nine (3%) houses. Trypanosoma cruzi-infected T. infestans and Triatoma sordida were collected indoors only in peri-urban houses and were infected with TcV and TcI, respectively. The triatomines fed on chickens, cats and humans. Peri-urban infestations were most frequent in a squatter settlement and particularly within the recently built mud houses of rural immigrants, with large-sized households, more dogs and cats and more crowding. Several of the observed infestations were most likely associated with passive bug transport from other sources and with active bug dispersal from neighbouring foci. Thus, the households in the squatter settlement were at a greater risk of bug invasion and colonisation. In sum, the incipient process of domestic colonisation and transmission, along with persistent rural-to-urban migratory flows and unplanned urbanisation, indicate the need for active vector surveillance and control actions at the peri-urban interface of the Gran Chaco.     

Sarcocystis neurona: molecular characterization of enolase domain I region and a comparison to other protozoa

Sarcocystis neurona causes protozoal myeloencephalitis and has the ability to infect a wide host range in contrast to other Sarcocystis species. In the current study, five S. neurona isolates from a variety of sources, three Sarcocystis falcatula, one Sarcocystis dasypi/S. neurona-like isolate, and one Besnoitia darlingi isolate were used to compare the enolase 2 gene segment containing the domain I region to previously sequenced enolase genes from Neospora caninum, Neospora hughesi, Toxoplasma gondii, Plasmodium falciparum, and Trypanosoma cruzi; enolase 2 segment containing domain I region is highly conserved amongst these parasites of veterinary and medical importance. Immunohistochemistry results indicates reactivity of T. gondii enolase 1 and 2 antibodies to S. neurona merozoites and metrocytes, but no reactivity of anti-enolase 1 to the S. neurona bradyzoite stage despite reactivity to T. gondii bradyzoites, suggesting expression differences between organisms.     

Ecological Connectivity of Trypanosoma cruzi Reservoirs and Triatoma pallidipennis Hosts in an Anthropogenic Landscape with Endemic Chagas Disease

Traditional methods for Chagas disease prevention are targeted at domestic vector reduction, as well as control of transfusion and maternal-fetal transmission. Population connectivity of Trypanosoma cruzi-infected vectors and hosts, among sylvatic, ecotone and domestic habitats could jeopardize targeted efforts to reduce human exposure. This connectivity was evaluated in a Mexican community with reports of high vector infestation, human infection, and Chagas disease, surrounded by agricultural and natural areas. We surveyed bats, rodents, and triatomines in dry and rainy seasons in three adjacent habitats (domestic, ecotone, sylvatic), and measured T. cruzi prevalence, and host feeding sources of triatomines. Of 12 bat and 7 rodent species, no bat tested positive for T. cruzi, but all rodent species tested positive in at least one season or habitat. Highest T. cruzi infection prevalence was found in the rodents, Baiomys musculus and Neotoma mexicana. In general, parasite prevalence was not related to habitat or season, although the sylvatic habitat had higher infection prevalence than by chance, during the dry season. Wild and domestic mammals were identified as bloodmeals of T. pallidipennis, with 9% of individuals having mixed human (4.8% single human) and other mammal species in bloodmeals, especially in the dry season; these vectors tested >50% positive for T. cruzi. Overall, ecological connectivity is broad across this matrix, based on high rodent community similarity, vector and T. cruzi presence. Cost-effective T. cruzi, vector control strategies and Chagas disease transmission prevention will need to consider continuous potential for parasite movement over the entire landscape. This study provides clear evidence that these strategies will need to include reservoir/host species in at least ecotones, in addition to domestic habitats.     

Sex, subdivision, and domestic dispersal of Trypanosoma cruzi lineage I in southern Ecuador

Background

Molecular epidemiology at the community level has an important guiding role in zoonotic disease control programmes where genetic markers are suitably variable to unravel the dynamics of local transmission. We evaluated the molecular diversity of Trypanosoma cruzi, the etiological agent of Chagas disease, in southern Ecuador (Loja Province). This kinetoplastid parasite has traditionally been a paradigm for clonal population structure in pathogenic organisms. However, the presence of naturally occurring hybrids, mitochondrial introgression, and evidence of genetic exchange in the laboratory question this dogma.

Methodology/Principal Findings

Eighty-one parasite isolates from domiciliary, peridomiciliary, and sylvatic triatomines and mammals were genotyped across 10 variable microsatellite loci. Two discrete parasite populations were defined: one predominantly composed of isolates from domestic and peridomestic foci, and another predominantly composed of isolates from sylvatic foci. Spatial genetic variation was absent from the former, suggesting rapid parasite dispersal across our study area. Furthermore, linkage equilibrium between loci, Hardy-Weinberg allele frequencies at individual loci, and a lack of repeated genotypes are indicative of frequent genetic exchange among individuals in the domestic/peridomestic population.

Conclusions/Significance

These data represent novel population-level evidence of an extant capacity for sex among natural cycles of T. cruzi transmission. As such they have dramatic implications for our understanding of the fundamental genetics of this parasite. Our data also elucidate local disease transmission, whereby passive anthropogenic domestic mammal and triatomine dispersal across our study area is likely to account for the rapid domestic/peridomestic spread of the parasite. Finally we discuss how this, and the observed subdivision between sympatric sylvatic and domestic/peridomestic foci, can inform efforts at Chagas disease control in Ecuador.     

Tritrichomonas foetus from domestic cats and cattle are genetically distinct

The genetic relationship amongst Tritrichomonas foetus isolated from domestic cats and cattle was investigated by DNA sequencing of the internal transcribed region of the ribosomal DNA unit and the TR7/TR8 variable-length repeat. The results reject the hypothesis that T. foetus from domestic cats is genetically identical to T. foetus in cattle. We suggest recognition of a ‘cat genotype’ and a ‘cattle genotype’ of T. foetus. Review of public nucleotide repositories revealed that the ‘cat genotype’ has not been isolated from cattle nor the ‘cattle genotype’ recovered from cats. However, at least one cat isolate has been shown to induce disease in experimentally infected cattle. We conclude that these genotypes fall within the single species T. foetus.