Genome-scale multilocus microsatellite typing of Trypanosoma cruzi discrete typing unit I reveals phylogeographic structure and specific genotypes linked to human infection

Trypanosoma cruzi is the most important parasitic infection in Latin America and is also genetically highly diverse, with at least six discrete typing units (DTUs) reported: Tc I, IIa, IIb, IIc, IId, and IIe. However, the current six-genotype classification is likely to be a poor reflection of the total genetic diversity present in this undeniably ancient parasite. To determine whether epidemiologically important information is "hidden" at the sub-DTU level, we developed a 48-marker panel of polymorphic microsatellite loci to investigate population structure among 135 samples from across the geographic distribution of TcI. This DTU is the major cause of resurgent human disease in northern South America but also occurs in silvatic triatomine vectors and mammalian reservoir hosts throughout the continent. Based on a total dataset of 12,329 alleles, we demonstrate that silvatic TcI populations are extraordinarily genetically diverse, show spatial structuring on a continental scale, and have undergone recent biogeographic expansion into the southern United States of America. Conversely, the majority of human strains sampled are restricted to two distinct groups characterised by a considerable reduction in genetic diversity with respect to isolates from silvatic sources. In Venezuela, most human isolates showed little identity with known local silvatic strains, despite frequent invasion of the domestic setting by infected adult vectors. Multilocus linkage indices indicate predominantly clonal parasite propagation among all populations. However, excess homozygosity among silvatic strains and raised heterozygosity among domestic populations suggest that some level of genetic recombination cannot be ruled out. The epidemiological significance of these findings is discussed.

Infection rates and genotypes of Trypanosoma rangeli and T. cruzi infecting free-ranging Saguinus bicolor (Callitrichidae), a critically endangered primate of the Amazon Rainforest

Parasites of wild primates are important for conservation biology and human health due to their high potential to infect humans. In the Amazon region, non-human primates are commonly infected by Trypanosoma cruzi and T. rangeli, which are also infective to man and several mammals. This is the first survey of trypanosomiasis in a critically endangered species of tamarin, Saguinus bicolor (Callitrichidae), from the Brazilian Amazon Rainforest. Of the 96 free-ranging specimens of S. bicolor examined 45 (46.8%) yielded blood smears positive for trypanosomes. T. rangeli was detected in blood smears of 38 monkeys (39.6%) whereas T. cruzi was never detected. Seven animals (7.3%) presented trypanosomes of the subgenus Megatrypanum. Hemocultures detected 84 positive tamarins (87.5%). Seventy-two of 84 (85.7%) were morphologically diagnosed as T. rangeli and 3 (3.1%) as T. cruzi. Nine tamarins (9.4%) yielded mixed cultures of these two species, which after successive passages generated six cultures exclusively of T. cruzi and two of T. rangeli, with only one culture remaining mixed. Of the 72 cultures positive for T. rangeli, 62 remained as established cultures and were genotyped: 8 were assigned to phylogenetic lineage A (12.9%) and 54 to lineage B (87.1%). Ten established cultures of T. cruzi were genotyped as TCI lineage (100%). Transmission of both trypanosome species, their potential risk to this endangered species and the role of wild primates as reservoirs for trypanosomes infective to humans are discussed.

Molecular genetics reveal that silvatic Rhodnius prolixus do colonise rural houses

BACKGROUND

Rhodnius prolixus is the main vector of Chagas disease in Venezuela. Here, domestic infestations of poor quality rural housing have persisted despite four decades of vector control. This is in contrast to the Southern Cone region of South America, where the main vector, Triatoma infestans, has been eliminated over large areas. The repeated colonisation of houses by silvatic populations of R. prolixus potentially explains the control difficulties. However, controversy surrounds the existence of silvatic R. prolixus: it has been suggested that all silvatic populations are in fact Rhodnius robustus, a related species of minor epidemiological importance. Here we investigate, by direct sequencing (mtcytb, D2) and by microsatellite analysis, 1) the identity of silvatic Rhodnius and 2) whether silvatic populations of Rhodnius are isolated from domestic populations.

METHODS AND FINDINGS

Direct sequencing confirmed the presence of R. prolixus in palms and that silvatic bugs can colonise houses, with house and palm specimens sharing seven cytb haplotypes. Additionally, mitochondrial introgression was detected between R. robustus and R. prolixus, indicating a previous hybridisation event. The use of ten polymorphic microsatellite loci revealed a lack of genetic structure between silvatic and domestic ecotopes (non-significant F(ST) values), which is indicative of unrestricted gene flow.

CONCLUSIONS

Our analyses demonstrate that silvatic R. prolixus presents an unquestionable threat to the control of Chagas disease in Venezuela. The design of improved control strategies is essential for successful long term control and could include modified spraying and surveillance practices, together with housing improvements.

Evolutionary and geographical history of the Leishmania donovani complex with a revision of current taxonomy

Leishmaniasis is a geographically widespread severe disease, with an increasing incidence of two million cases per year and 350 million people from 88 countries at risk. The causative agents are species of Leishmania, a protozoan flagellate. Visceral leishmaniasis, the most severe form of the disease, lethal if untreated, is caused by species of the Leishmania donovani complex. These species are morphologically indistinguishable but have been identified by molecular methods, predominantly multilocus enzyme electrophoresis. We have conducted a multifactorial genetic analysis that includes DNA sequences of protein-coding genes as well as noncoding segments, microsatellites, restriction-fragment length polymorphisms, and randomly amplified polymorphic DNAs, for a total of approximately 18,000 characters for each of 25 geographically representative strains. Genotype is strongly correlated with geographical (continental) origin, but not with current taxonomy or clinical outcome. We propose a new taxonomy, in which Leishmania infantum and L. donovani are the only recognized species of the L. donovani complex, and we present an evolutionary hypothesis for the origin and dispersal of the species. The genus Leishmania may have originated in South America, but diversified after migration into Asia. L. donovani and L. infantum diverged approximately 1 Mya, with further divergence of infraspecific genetic groups between 0.4 and 0.8 Mya. The prevailing mode of reproduction is clonal, but there is evidence of genetic exchange between strains, particularly in Africa.

Glycoprotein 63 (gp63) genes show gene conversion and reveal the evolution of Old World Leishmania

Species of the subgenus Leishmania (Leishmania) cause the debilitating disease leishmaniasis on four continents. Species grouped within the Leishmania donovani complex cause visceral leishmaniasis, a life-threatening disease, often associated with poverty, and affecting some 0.5 million people each year. The Leishmania glycoprotein GP63, or major surface protease, is a metalloprotease involved in parasite survival, infectivity and virulence. Here, we show that evolution of the gp63 multigene family is influenced by mosaic or fragmental gene conversion. This is a major evolutionary force for both homogenisation and for generating diversity, even in the absence of sexual reproduction. We propose here that the high GC content at the third codon position in the gp63 family of Old World Leishmania may be higher in multicopy regions, under the biased gene conversion model, because increased copy numbers may lead to increased rates of recombination. We confirm that one class of gp63 genes with an extended 3'end signal, gp63(EXT), reveals genetic groups within the complex and gives insights into evolution and host associations. Gp63(EXT) genes can also provide the basis for rapid and reliable genotyping of strains in the L. donovani complex. Our results confirmed that a more stringent definition of Leishmania infantum is required and that the species Leishmania archibaldi should be suppressed.

Multiple hybrid genotypes of Leishmania (viannia) in a focus of mucocutaneous Leishmaniasis

The principal agent of mucocutaneous leishmaniasis (MCL) is the South American protozoan parasite Leishmania (Viannia) braziliensis. This organism is generally considered to be clonal, that is, it does not to undergo genetic exchange. Nevertheless, apparent hybrids between several Leishmania species have been reported in the New World and the Old World. When we characterized isolates of Leishmania (Viannia) from a single focus of cutaneous leishmaniasis (CL) and MCL, we found a remarkable phenotypic and genotypic diversity, with 12 zymodemes and 20 microsatellite genotypes. Furthermore, 26 of the 59 isolates were L. braziliensis/L. peruviana phenotypic hybrids that displayed 7 different microsatellite genotypes. A hybrid genotype was the only organism isolated from 4 patients with MCL. Thus hybrids must be included among the potential agents of MCL. Despite the propensity for clonality, hybrids are also an important feature of Leishmania (Viannia) and may give rise to epidemiologically important emergent genotypes.

The Leishmania donovani complex: Genotypes of five metabolic enzymes (ICD, ME, MPI, G6PDH, and FH), new targets for multilocus sequence typing

Flagellates of the Leishmania donovani complex are causative agents of human cutaneous and visceral leishmaniasis. The complex is comprised of L. donovani, Leishmania infantum and Leishmania archibaldi, although the latter is not now considered to be a valid species. Morphological distinction of Leishmania species is impractical, so biochemical, immunological and DNA-based criteria were introduced. Multilocus enzyme electrophoresis (MLEE) is the present gold standard. We have sequenced the genes encoding five metabolic enzymes used for MLEE, both to resolve the DNA diversity underlying isoenzyme mobility differences and to explore the potential of these targets for higher resolution PCR-based multilocus sequence typing. The genes sequenced were isocitrate dehydrogenase, malic enzyme, mannose phosphate isomerase, glucose-6-phosphate dehydrogenase, and fumarate hydratase, for 17 strains of L. infantum, seven strains of L. donovani, and three strains of L. archibaldi. Protein mobilities predicted from amino acid sequences did not always accord precisely with reported MLEE profiles. A high number of heterozygous sites was detected. Heterozygosity was particularly frequent in some strains and indirectly supported the presence of genetic exchange in Leishmania. Phylogenetic analysis of a concatenated alignment based on a total of 263 kb protein-coding sequences showed strong correlation of genotype with geographical origin. Europe and Africa appear to represent independent evolutionary centres.

Resolution of multiclonal infections of Trypanosoma cruzi from naturally infected triatomine bugs and from experimentally infected mice by direct plating on a sensitive solid medium

The isolation of biological clones of Trypanosoma cruzi by microscopically dispensing individual organisms or by serial dilution is laborious and time consuming. The inability to resolve mixed T. cruzi infections, from vectors and hosts, and to isolate clones of slow growing genotypes by efficient plating on solid media, has hindered characterisation studies and downstream applications. We have devised and validated a sensitive, solid medium plating technique for rapid in vitro isolation of clones representative of all the recognised T. cruzi lineages (TCI, TCIIa-e), including the slow growing strain CANIII (TC IIa) and Trypanosoma rangeli, with high plating efficiencies. Furthermore, the method is effective for the isolation of clones directly from silvatic triatomine bugs and from experimentally infected mice harbouring mixed infections, allowing resolution of multiclonal infections from varied sources.

Towards multilocus sequence typing of the Leishmania donovani complex: Resolving genotypes and haplotypes for five polymorphic metabolic enzymes (ASAT, GPI, NH1, NH2, PGD)

Multilocus enzyme electrophoresis is the gold standard for identification of Leishmania species and strains. Drawbacks include: only amino acid polymorphisms affecting electrophoretic mobility are detected; distinct allozymes can have coincident mobilities; few characters are available; and parasites must be cultured in bulk. So far, thousands of Leishmania strains have been phenotyped by multilocus enzyme electrophoresis. Here, we sequence enzyme-coding genes to provide a PCR-based higher resolution equivalent of multilocus enzyme electrophoresis, particularly for Leishmania infantum. Of 15 enzymes used for multilocus enzyme electrophoresis (MON typing) we have sequenced aspartate aminotransferase, glucose-6-phosphate isomerase, nucleoside hydrolase 1, nucleoside hydrolase 2 and 6-phosphogluconate dehydrogenase. Heterozygous alleles were common, with multiple heterozygous sites within a single locus for several of the genes. Haplotypes were resolved by allele-specific PCR and allele-specific sequencing. Heterozygous haplotypes conformed to the haplotypes of putative parents. One strain appeared to be hybrid across two genetic groups of the Leishmania donovani complex. In most cases, a single amino acid polymorphism was responsible for change in enzyme mobility. Some indistinguishable phenotypes were produced by distinct genotypes. Silent genetic polymorphisms provided enhanced discrimination over multilocus enzyme electrophoresis, for example, by subdividing the zymodeme MON-1. The PCR-based genotyping that we describe could be applied directly to clinical samples or to small volume cultures and in a multilocus sequence typing format. Furthermore, it can be used to detect recombination indirectly and for population genetics studies.

Field ecology of sylvatic Rhodnius populations (Heteroptera, Triatominae): risk factors for palm tree infestation in western Ecuador

Most Rhodnius species (Triatominae) are primarily associated with palm trees. They maintain enzootic Trypanosoma cruzi transmission and are responsible for human infection (causing Chagas disease) through the Neotropics. Assessing whether individual palm traits (ecological and/or botanical) may increase the risk of palm infestation by triatomines is relevant in areas where bugs invade houses flying from peridomestic palms. We developed a novel fieldwork approach with that objective, and applied it to study infestation by sylvatic Rhodnius ecuadoriensis in 110 tagua palms (Phytelephas aequatorialis). Palm infestation (23% overall) was non-randomly distributed in our sample. Palms located in anthropic landscapes were frequently infested (>27%, n=92), whereas no bugs were collected from palms surveyed within forest remnants (n=18; P=0.01). The presence of abundant decaying vegetable matter (P=0.001) and (to a lesser extent) epiphytic plants (P=0.049) on palm crowns and stems increased the probability of infestation and was positively correlated with the apparent density of bug colonies (R2=0.68). A trend towards higher infestation rates in male palms (34% vs. 18%) could relate to female palm management (removal of infrutescences and vegetable debris) in areas where palm seeds are harvested. An outline of 'risk palm ecotopes' and environmental management-based strategies for the control of peridomestic, palm tree-living vector populations are proposed.

First detection of Leishmania major in peridomestic Phlebotomus papatasi from Isfahan province, Iran: comparison of nested PCR of nuclear ITS ribosomal DNA and semi-nested PCR of minicircle kinetoplast DNA

Two PCR methods were compared for their sensitivity in detecting cultured Leishmania major, before being used to estimate infection rates in female sandflies (Phlebotomus papatasi) collected from peridomestic animal shelters and the nearby burrows of the gerbil reservoir hosts, Rhombomys opimus, in Isfahan province, central Iran. A semi-nested PCR was used to amplify a fragment of minicircle kinetoplast (k) DNA with a length and sequence diagnostic for L. major, and a nested PCR was developed to amplify a fragment containing the internal transcribed spacers of the ribosomal RNA genes (ITS-rDNA) with a sequence diagnostic for L. major. The semi-nested PCR was less sensitive than the nested PCR when using DNA extracted from cultured promastigotes of L. major, but it was more sensitive for detecting L. major in wild-caught sandflies. At the edges of two Isfahan villages, infection rates were significantly higher in P.papatasi collected outside gerbil burrows (14/28) compared with those from peridomestic animal shelters (2/21). This is the first record of L. major detected in P.papatasi from peridomestic sites in Isfahan province.

Origins of Chagas disease: Didelphis species are natural hosts of Trypanosoma cruzi I and armadillos hosts of Trypanosoma cruzi II, including hybrids

Trypanosoma cruzi, the causative agent of Chagas disease, has at least two principal intraspecific subdivisions, T. cruzi I (TCI) and T. cruzi II (TCII), the latter containing up to five subgroups (a-e). Whilst it is known that TCI predominates from the Amazon basin northwards and TCII to the South, where the disease is considered to be clinically more severe, the precise clinical and evolutionary significance of these divisions remains enigmatic. Here, we present compelling evidence of an association between TCI and opossums (Didelphis), and TCII and armadillos, on the basis of key new findings from the Paraguayan Chaco region, together with a comprehensive analysis of historical data. We suggest that the distinct arboreal and terrestrial ecologies, respectively, of these mammal hosts provide a persuasive explanation for the extant T. cruzi intraspecific diversity in South America, and for separate origins of Chagas disease in northern South America and in the southern cone countries.

The discovery of Chagas disease: progress and prejudice

The discovery of Chagas disease makes an extraordinary story. It encompasses the pinnacle of scientific achievement and has some unique features. In addition, there is a background story line of controversy, jealousy, and power politics. This article provides a synopsis of all these fascinating aspects of the discovery.

Genetic polymorphism within the leishmania donovani complex: correlation with geographic origin

Random amplified polymorphic DNA (RAPD) was used to detect intraspecific diversity for the Leishmania donovani complex. Fifty-two decameric to 21-meric primers of arbitrary sequence were applied to 15 strains that belong to nine zymodemes. Strains belonging to the species L. major and L. tropica were used as outgroups. A total of 902 amplicons generated by RAPD were scored. Most primers produced species-specific profiles, only 0.6% amplicons were shared by all species, while 4.3% amplicons were common for all 15 strains of the L. donovani complex. Well-supported trees have been constructed, which show a rather strong correlation between the genetic polymorphism of studied strains and their geographic origin. In all obtained trees, L. infantum was paraphyletic. The RAPD profiles suggest that MON-30 belongs to L. donovani. Moreover, the genetic distance between the L. archibaldi strain and other leishmanias does not warrant existence of a separate species.

Leishmania donovanicomplex: genotyping with the ribosomal internal transcribed spacer and the mini-exon

Intergenic region typing by restriction analysis of the ribosomal internal transcribed spacer (ITS) and mini-exon provide diagnostic markers for someLeishmania. Here, we evaluate restriction analysis of these targets for genotyping and phylogenetic analysis within theLeishmania donovanicomplex (agents of visceral leishmaniasis). Each method was useful for genotyping of bothL. donovanicomplex strains and Old WorldLeishmaniaspecies. The targets produced less robust groups than gp63 intergenic regions, but support the need for re-evaluation of the taxonomy of theL. donovanicomplex.

American trypanosomiasis (Chagas' disease) and the role of molecular epidemiology in guiding control strategies

Chagas' disease is a parasitic infection that has far reaching consequences for public health and national economies in Latin America. The latest molecular typing methods may help in developing targeted, effective control programmes

Mechanism of genetic exchange in American trypanosomes

The kinetoplastid Protozoa are responsible for devastating diseases. In the Americas, Trypanosoma cruzi is the agent of Chagas' disease--a widespread disease transmissible from animals to humans (zoonosis)--which is transmitted by exposure to infected faeces of blood-sucking triatomine bugs. The presence of genetic exchange in T. cruzi and in Leishmania is much debated. Here, by producing hybrid clones, we show that T. cruzi has an extant capacity for genetic exchange. The mechanism is unusual and distinct from that proposed for the African trypanosome, Trypanosoma brucei. Two biological clones of T. cruzi were transfected to carry different drug-resistance markers, and were passaged together through the entire life cycle. Six double-drug-resistant progeny clones, recovered from the mammalian stage of the life cycle, show fusion of parental genotypes, loss of alleles, homologous recombination, and uniparental inheritance of kinetoplast maxicircle DNA. There are strong genetic parallels between these experimental hybrids and the genotypes among natural isolates of T. cruzi. In this instance, aneuploidy through nuclear hybridization results in recombination across far greater genetic distances than mendelian genetic exchange. This mechanism also parallels genome duplication.

The Trypanosoma cruzi enzyme TcGPXI is a glycosomal peroxidase and can be linked to trypanothione reduction by glutathione or tryparedoxin

Trypanosoma cruzi glutathione-dependent peroxidase I (TcGPXI) can reduce fatty acid, phospholipid, and short chain organic hydroperoxides utilizing a novel redox cycle in which enzyme activity is linked to the reduction of trypanothione, a parasite-specific thiol, by glutathione. Here we show that TcGPXI activity can also be linked to trypanothione reduction by an alternative pathway involving the thioredoxin-like protein tryparedoxin. The presence of this new pathway was first detected using dialyzed soluble fractions of parasite extract. Tryparedoxin was identified as the intermediate molecule following purification, sequence analysis, antibody studies, and reconstitution of the redox cycle in vitro. The system can be readily saturated by trypanothione, the rate-limiting step being the interaction of trypanothione with the tryparedoxin. Both tryparedoxin and TcGPXI operate by a ping-pong mechanism. Overexpression of TcGPXI in transfected parasites confers increased resistance to exogenous hydroperoxides. TcGPXI contains a carboxyl-terminal tripeptide (ARI) that could act as a targeting signal for the glycosome, a kinetoplastid-specific organelle. Using immunofluorescence, tagged fluorescent proteins, and biochemical fractionation, we have demonstrated that TcGPXI is localized to both the glycosome and the cytosol. The ability of TcGPXI to use alternative electron donors may reflect their availability at the corresponding subcellular sites.

Nuclear rDNA ITS-2 sequences reveal polyphyly of Panstrongylus species (Hemiptera: Reduviidae: Triatominae), vectors of Trypanosoma cruzi

Panstrongylus species are widely distributed throughout the Americas, where they act as vectors of Trypanosoma cruzi, agent of Chagas disease. Their intraspecific relationships, taxonomic position and phylogeny in relation to other Triatomini were explored using ribosomal DNA (rDNA) internal transcribed spacer 2 (ITS-2) sequence polymorphisms and maximum parsimony, distance and maximum likelihood analyses of 10 populations representing six species of the genus (P. megistus, P. geniculatus, P. rufotuberculatus, P. lignarius, P. herreri and P. chinai). At the subspecific level, P. megistus appeared more homogeneous than P. rufotuberculatus and P. geniculatus (both with broader distribution). Several dinucleotide microsatellites were detected in the sequences of given species. Many of these microsatellites (GC, TA, GT and AT) showed different number of repeats in different populations and thus, may be very useful for population differentiation and dynamics analyses in future studies. The sequences of P. lignarius (considered sylvatic) and P. herreri (a major disease vector in Peru) were identical, suggesting that these species should be synonymised. Intrageneric analysis showed a clear separation of P. rufotuberculatus, with closest relationships between P. geniculatus and P. chinai, and P. megistus occupying a separate branch. Genetic distances between Panstrongylus species (0.11585-0.22131) were higher than those between Panstrongylus and other Triatomini (16 species from central and North America and South America) (0.08617-0.11039). The distance between P. megistus and P. lignarius/herreri (0.22131) was the largest so far recorded in the tribe. The pronounced differences in length and nucleotide composition suggest a relatively old divergence of Panstrongylus species. P. rufotuberculatus was closer to Mesoamerican Triatoma, Meccus and Dipetalogaster species than to other Panstrongylus. All Panstrongylus clustered with the Mesoamerican clade; P. rufotuberculatus clustered with the phyllosoma complex and T. dimidiata, with D. maxima and T. barberi in a basal position. The rest of Panstrongylus appeared paraphyletically in the tree. This is evidence suggesting polyphyly within the genus Panstrongylus, whose species may be related to the ancestors giving rise to central and North American Triatomini.

An insect molecular clock dates the origin of the insects and accords with palaeontological and biogeographic landmarks

A unified understanding of >390 Myr of insect evolution requires insight into their origin. Molecular clocks are widely applied for evolutionary dating, but clocks for the class Insecta have remained elusive. We now define a robust nucleotide and amino acid mitochondrial molecular clock encompassing five insect orders, including the Blattaria (cockroaches), Orthoptera (crickets and locusts), Hemiptera (true bugs), Diptera, and Lepidoptera (butterflies and moths). Calibration of the clock using one of the earliest, most extensive fossil records for insects (the early ancestors of extant Blattaria) was congruent with all available insect fossils, with biogeographic history, with the Cambrian explosion, and with independent dating estimates from Lepidopteran families. In addition, dates obtained from both nucleotide and amino acid clocks were congruent with each other. Of particular interest to vector biology is the early date of the emergence of triatomine bugs (99.8-93.5 MYA), coincident with the formation of the South American continent during the breakup of Gondwanaland. More generally, we reveal the insects arising from a common ancestor with the Anostraca (fairy shrimps) at around the Silurian-Ordovician boundary (434.2-421.1 MYA) coinciding with the earliest plant megafossil. We explore Tilyard's theory proposing that the terrestrial transition of the aquatic arthropod ancestor to the insects is associated with a particular plant group (early vascular plants). The major output of the study is a comprehensive series of dates for deep-branching points within insect evolution that can act as calibration points for further dating studies within insect families and genera.

Emerging Chagas disease in Amazonian Brazil

In the Amazon Basin, Trypanosoma cruzi infection is enzootic, involving a variety of wild mammals and at least 10 of the 16 reported silvatic triatomine bug species. Human cases of Chagas disease are increasing, indicating that the disease may be emerging as a wider public health problem in the region: 38 cases from 1969 to 1992, and 167 in the past eight years. This article reviews the status of Chagas disease in Amazonian Brazil, including known reservoirs and vectors, and the genetic diversity of T. cruzi. At least three subspecific groups of T. cruzi-T. cruzilZ1, T. cruziZ3 and T. cruziZ3/Z1 ASAT--are present. It appears that T. cruzil has an extant capacity for genetic exchange. Attention is also drawn to the risk of domestic endemicity, in addition to the tasks facing the disease control authorities.

The triatomines of northern Peru, with emphasis on the ecology and infection by trypanosomes of Rhodnius ecuadoriensis (Triatominae)

Information on the distribution and synanthropic behaviour of triatomines is essential for Chagas disease vector control. This work summarises such information from northern Peru, and presents new data on Rhodnius ecuadoriensis - an important local vector infesting 10-35% of dwellings in some zones. Three species are strongly synanthropic and may be suitable targets for chemical control of domestic/peridomestic bug populations. Panstrongylus herreri, the main domestic vector in the area, is probably present in sylvatic ecotopes in the Marañón river system. R. ecuadoriensis and Triatoma dimidiata seem exclusively domestic; biogeographical and ecological data suggest they might have spread in association with humans in northern Peru. Confirmation of this hypothesis would result in a local eradication strategy being recommended. Presence of trypanosome natural infection was assessed in 257 R. ecuadoriensis; Trypanosoma rangeli was detected in 4% of bugs. Six further triatomine species are potential disease vectors in the region (T. carrioni, P. chinai, P. rufotuberculatus, P. geniculatus, R. pictipes, and R. robustus), whilst Eratyrus mucronatus, E. cuspidatus, Cavernicola pilosa, Hermanlentia matsunoi, and Belminus peruvianus have little or no epidemiological significance. A strong community-based entomological surveillance system and collaboration with Ecuadorian public health authorities and researchers are recommended.