Phylogenetic, morphological and behavioural analyses support host switching of Trypanosoma (Herpetosoma) lewisi from domestic rats to primates

We characterized four Brazilian trypanosomes isolated from domestic rats and three from captive non-human primates that were morphologically similar to T. lewisi, a considered non-pathogenic species restricted to rodents and transmitted by fleas, despite its potential pathogenicity for infants. These isolates were identified as T. lewisi by barcoding using V7V8 SSU rDNA sequences. In inferred phylogenetic trees, all isolates clustered tightly with reference T. lewisi and T. lewisi-like trypanosomes from Europe, Asia and Africa and despite their high sequence conservation formed a homogeneous clade separate from other species of the subgenus T. (Herpetosoma). With the aim of clearly resolving the relationships between the Brazilian isolates from domestic rats and primates, we compared sequences from more polymorphic ITS rDNA. Results corroborated that isolates from Brazilian rats and monkeys were indeed of the same species and quite close to T. lewisi isolates of humans and rats from different geographical regions. Morphology of the monkey isolates and their behaviour in culture and in experimentally infected rats were also compatible with T. lewisi. However, infection with T. lewisi is rare among monkeys. We have examined more than 200 free-ranging and 160 captive monkeys and found only three infected individuals among the monkeys held in captivity. The findings of this work suggest that proximity of monkeys and infected rats and their exposure to infected fleas may be responsible for the host switching of T. lewisi from their natural rodent species to primates. This and previous studies reporting T. lewisi in humans suggest that this trypanosome can cause sporadic and opportunistic flea-borne infection in primates.

Infection by Trypanosoma vivax in goats and sheep in the Brazilian semiarid region: from acute disease outbreak to chronic cryptic infection

A study was undertaken to investigate the role of Trypanosoma vivax in sheep and goat mortality and abortions in the Brazilian semiarid region, where outbreaks had been previously reported in bovines. For this purpose, 177 goats and 248 sheep (20% of herds) were randomly sampled on four farms in the State of Paraiba in May and October 2008. The animals were screened for trypanosomes by the buffy coat technique (BCT) and PCR. Infected animals, approximately 25% in both surveys, manifested apathy, pale mucous membranes, enlarged lymph nodes, weakness, weight loss, opacity of the cornea, blindness and abortion. However, the animals with acute and severe disease showing the highest levels of parasitemia and fever, which many times resulted in death, were only detected in the first survey. These severely diseased animals exhibited progressive weight loss and had the smallest packed cell volume (PCV) values. During survey 2, done in October 2008 on the same farms, only animals with low parasitemia and normal temperatures, PCV values and body weights were detected. Therefore, animals that spontaneously recovered from acute infection developed chronic and asymptomatic disease. This finding demonstrated for the first time that sheep and goats, which are the most important livestock in the semiarid region of Brazil, may be severely injured by T. vivax infection and also play a role as asymptomatic carriers and important sources of T. vivax to ruminants in general.

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.

Comparative phylogeography of Trypanosoma rangeli and Rhodnius (Hemiptera: Reduviidae) supports a long coexistence of parasite lineages and their sympatric vectors

To make reliable interpretations about evolutionary relationships between Trypanosoma rangeli lineages and their insect vectors (triatomine bugs of the genus Rhodnius) and, thus, about the determinant factors of lineage segregation within T. rangeli, we compared phylogenies of parasite isolates and vector species. Sixty-one T. rangeli isolates from invertebrate and vertebrate hosts were initially evaluated in terms of polymorphism of the spliced-leader gene (SL). Further analysis based on SL and SSUrRNA sequences from 33 selected isolates, representative of the overall phylogenetic diversity and geographical range of T. rangeli, supported four phylogenetic lineages within this species. By comparing the phylogeny of Rhodnius species with that inferred for T. rangeli isolates and through analysis of the geographical range of the isolates, we showed that there is a very significant overlap in the distribution of Rhodnius species and T. rangeli lineages. Congruence between phylogeographical analysis of both T. rangeli lineages and complexes of Rhodnius species are consistent with the hypothesis of a long coexistence of parasites and their vectors, with lineage divergence associated with sympatric species of Rhodnius apparently without association with particular vertebrate hosts. Separation of T. rangeli isolates from vectors of distinct complexes living in sympatry favours the absence of gene flow between the lineages and suggests evolution of T. rangeli lineages in independent transmission cycles, probably associated to specific Rhodnius spp. ecotopes. A polymerase chain reaction assay based on SL intergenic sequences was developed for simultaneous identification and lineage genotyping of T. rangeli in epidemiological surveys.

Morphological and molecular diversity and phylogenetic relationships among anuran trypanosomes from the Amazonia, Atlantic Forest and Pantanal biomes in Brazil

We examined for the presence of trypanosomes in blood samples from 259 anurans (47 species from 8 families), the majority of which were from the Brazilian Amazonia, Atlantic Forest and Pantanal biomes. Trypanosomes were detected by a combination of microhaematocrit and haemoculture methods in 45% of the anurans, and 87 cultures were obtained: 44 from Hylidae, 22 from Leptodactylidae, 15 from Bufonidae, 5 from Leiuperidae and 1 from an unidentified anuran. High morphological diversity (11 morphotypes) was observed among blood trypanosomes from anurans of different species and of the same species as well as among trypanosomes from the same individual. Conversely, morphologically similar trypanosomes were found in anurans from distinct species and biomes. ITS and SSU rDNA polymorphisms revealed high diversity among the 82 isolates examined.† Twenty-nine genotypes could be distinguished, the majority distributed in 11 groups. Phylogenetic relationships based on rDNA sequences indicated that isolates from more phylogenetically related anurans are more closely related. Comparison of anuran trypanosomes from Brazil and other countries revealed several new species among the isolates examined in this study. Phylogenetic relationships suggest that host restriction, host switching and overall ecogeographical structure may have played a role in the evolution of the anuran trypanosomes.

Trypanosomiasis by Trypanosoma vivax in cattle in the Brazilian semiarid: Description of an outbreak and lesions in the nervous system

An outbreak of trypanosomiasis by Trypanosoma vivax is reported in the semiarid of Paraíba, Northeastern Brazil from May to August 2002. Sixty-four cows out of 130 were affected; 11 died and the other recovered after treatment with diminazene aceturate. Affected animals had fever, anemia, weight loss, hypoglycemia, increased serum levels of aspartate aminotransferase and, in nine cows, nervous signs. All cows with nervous signs died; six of them recovered after treatment, but the disease relapsed. Six cows aborted and one delivered a calf that died immediately after parturition. Thirty-two out of 100 calves were affected and five died. Nervous signs were not observed in the calves. Gross lesions were thickening of the meninges, enlarged lymph nodes and prominent white pulp of the spleen. The main histological lesion was meningoencephalitis and malacia in the brain of cows with nervous signs. No antibodies against trypanosomes were found in 33 blood samples collected before the outbreak in the affected farm and in 29 samples collected at the same time in two other neighbor farms. Until January 2003, all 89 animals tested had antibodies against T. vivax, suggesting the occurrence of sub clinical infections in cattle without clinical signs. Only two out of 85 serum samples collected on April 2004 were positive for T. vivax antibodies. Data obtained suggested that the semiarid region is non-endemic for trypanosomiasis and that disease occurred due to introduction of the parasite in a susceptible population after an apparent rise in the Tabanus spp. population.

The taxonomic and phylogenetic relationships of Trypanosoma vivax from South America and Africa

The taxonomic and phylogenetic relationships of Trypanosoma vivax are controversial. It is generally suggested that South American, and East and West African isolates could be classified as subspecies or species allied to T. vivax. This is the first phylogenetic study to compare South American isolates (Brazil and Venezuela) with West/East African T. vivax isolates. Phylogeny using ribosomal sequences positioned all T. vivax isolates tightly together on the periphery of the clade containing all Salivarian trypanosomes. The same branching of isolates within T. vivax clade was observed in all inferred phylogenies using different data sets of sequences (SSU, SSU plus 5.8S or whole ITS rDNA). T. vivax from Brazil, Venezuela and West Africa (Nigeria) were closely related corroborating the West African origin of South American T. vivax, whereas a large genetic distance separated these isolates from the East African isolate (Kenya) analysed. Brazilian isolates from cattle asymptomatic or showing distinct pathology were highly homogeneous. This study did not disclose significant polymorphism to separate West African and South American isolates into different species/subspecies and indicate that the complexity of T. vivax in Africa and of the whole subgenus Trypanosoma (Duttonella) might be higher than previously believed.

Phylogeny of Trypanosoma ( Megatrypanum ) theileri and related trypanosomes reveals lineages of isolates associated with artiodactyl hosts diverging on SSU and ITS ribosomal sequences

SSU ribosomal sequences of trypanosomes from Brazilian cattle and water buffalo were used to infer phylogenetic relationships between non-pathogenic T. theileri and allied species parasitic in artiodactyls. T. theileri trypanosomes from distinct geographical regions in Brazil and from other countries were tightly clustered into the 'clade T. theileri' distant from the 'T. brucei clade' of pathogenic parasites of artiodactyls, and also distinct from trypanosomes of other mammals. The existence of this monophyletic assemblage (T. theileri clade) composed only by isolates from artiodactyl species justifies the continued recognition of the subgenus T. (Megatrypanum) with T. theileri as its type species. Phylogenies based on SSU and ITS1 ribosomal sequences produced the same branching pattern with isolates from different mammalian hosts clustered in 5 lineages: A, related to water buffalo; B, C and D, to cattle; E, to fallow deer. The pattern of host specificity allied to some congruence between host and parasite phylogenies suggested association of these trypanosomes with their respective hosts. Segregation of cattle isolates into three lineages revealed an overall geographical structure. Moreover, positioning of trypanosomes infecting tabanids in the T. theileri clade is consistent with the role of these flies as important vectors of these trypanosomes.

Phylogeny, taxonomy and grouping of Trypanosoma rangeli isolates from man, triatomines and sylvatic mammals from widespread geographical origin based on SSU and ITS ribosomal sequences

Phylogenetic relationships among Trypanosoma rangeli isolates from man, wild mammals and triatomine bugs from widespread geographical origin were inferred by comparison of the small subunit of ribosomal gene sequences. The phylogenetic trees indicated that the subgenus Herpetosoma is polyphyletic and strongly supported division of this group into two monophyletic lineages, one made up of T. rangeli, T. rangeli-like and allied species and other consisting of T. lewisi and related taxa. Based on phylogenetic analysis, morphology, behaviour in vertebrate and invertebrate hosts and epidemiology we propose: a) the validation of Herpetosoma as a taxon comprised only for species of group lewisi and the maintenance of T. lewisi as the type-species of this subgenus; b) the classification of T. rangeli, T. rangeli-like and allied species into a ‘T. rangeli-clade’ more closely related to Schizotrypanum than to T. lewisi or T. brucei. The phylogenetic tree disclosed at least 4 groups within the clade T. rangeli, all confirmed by polymorphism of the internal transcribed spacer, thus conferring for the first time phylogenetic support to groups of T. rangeli and corroborating the high complexity of this taxon. Grouping was independent of their mammalian host-species and geographical origin, indicating that other factors are determining this segregation.

Randomly amplified polymorphic DNA analysis of Trypanosoma rangeli and allied species from human, monkeys and other sylvatic mammals of the Brazilian Amazon disclosed a new group and a species-specific marker

We characterized 14 trypanosome isolates from sylvatic mammals (9 from primates, 1 from sloth, 2 from anteaters and 2 from opossum) plus 2 human isolates of Brazilian Amazon. These isolates were proven to be Trypanosoma rangeli by detection of metacyclic trypomastigotes in the salivary glands of triatomines and by a specific PCR assay. Polymorphism determined by randomly amplified polymorphic DNA (RAPD) revealed that most (12) of the Brazilian T. rangeli isolates from the Amazon differed from those of other geographical regions, thus constituting a new group of T. rangeli. Four Brazilian isolates clustered together with a previously described group (A) that was described as being composed of being isolates from Colombia and Venezuela. Isolates from Panama and El Salvador form another group. The isolate from Southern Brazil did not cluster to any of the above-mentioned groups. This is the first study that assesses the genetic relationship of a large number of isolates from wild mammals, especially from non-human primates. A randomly-amplified DNA fragment (Tra625) exclusive to T. rangeli was used to develop a PCR assay able to detect all T. rangeli groups.

Brazilian isolates of Trypanosoma (Megatrypanum) theileri: diagnosis and differentiation of isolates from cattle and water buffalo based on biological characteristics and randomly amplified DNA sequences

We detected and cultivated isolates of Trypanosoma (Megatrypanum) theileri from cattle and water buffaloes in São Paulo state, southeastern Brazil, which were characterized by comparing morphological, growth and molecular features. Although isolates from cattle and water buffalo were morphologically indistinguishable, they differed in their growth characteristics. A dendrogram based on randomly amplified polymorphic DNA (RAPD) patterns indicated close-genetic relationships among all isolates from both species, which were all tightly clustered together and distant from Megatrypanum species from wild mammals. In addition, isolates within the T. theileri-cluster were clearly segregated into two host-associated groups. The sequence of a synapomorphic RAPD-derived DNA fragment (Tth625), which was shared by all T. theileri trypanosomes from cattle and buffalo but not detected in any of 13 other trypanosome species, was used as target for a conventional T. theileri-specific PCR assay. We also defined RAPD fragments (Tthc606 and Tthb606) that distinguished cattle from buffalo isolates. Thus, distinct growth features and genetic variability distinguished between isolates from cattle and water buffaloes of the same geographic origin, suggesting an association of these isolates with their host species. The trypanosomes from water buffalo reported here are the first T. theileri-like isolates from the Asiatic buffalo (Bubalus bubalis) to be continuously cultured and compared with cattle isolates using biological and molecular methods.

Genetic relatedness among Trypanosoma evansi stocks by random amplification of polymorphic DNA and evaluation of a synapomorphic DNA fragment for species-specific diagnosis

In this study we employed randomly amplified polymorphic DNA patterns to assess the genetic relatedness among 14 Brazilian Trypanosoma evansi stocks from domestic and wild hosts, which are known to differ in biological characteristics. These akinetoplastic stocks were compared with one another, to three Old World (Ethiopia, China and Philippines) dyskinetoplastic stocks of T. evansi, and also with Trypanosoma equiperdum, Trypanosoma brucei brucei, Trypanosoma brucei gambiense and Trypanosoma brucei rhodesiense. Randomly amplified polymorphic DNA analysis showed limited heterogeneity in T. evansi stocks from different hosts and geographical regions of the world, or in other species of the subgenus Trypanozoon. However, minor variations generated random amplification of polymorphic DNA analysis disclosed a pattern consisting of a unique synapomorphic DNA fragment (termed Te664) for the T. evansi cluster that was not detected in any other trypanosome species investigated. Pulsed field gel electrophoresis analysis demonstrated that the Te664 fragment is a repetitive sequence, dispersed in intermediate and minichromosomes of T. evansi. Based on this sequence, we developed a conventional PCR assay for the detection of T. evansi using crude preparations of blood collected either on glass slides or on filter paper as template DNA. Our results showed that this assay may be useful as a diagnostic tool for field-epidemiological studies of T. evansi.