Molecular identification of the Trypanosoma (Herpetosoma) lewisi clade in black rats (Rattus rattus) from Australia.

Invasive rodent species are known hosts for a diverse range of infectious microorganisms and have long been associated with the spread of disease globally. The present study describes molecular evidence for the presence of a Trypanosoma sp. from black rats (Rattus rattus) in northern Sydney, Australia. Sequences of the 18S ribosomal RNA (rRNA) locus were obtained in two out of eleven (18%) blood samples with subsequent phylogenetic analysis confirming the identity within the Trypanosoma lewisi clade.

Predictors of Trypanosoma lewisi in Rattus norvegicus from Durban, South Africa.

This study investigated associations between Trypanosoma lewisi and Xenopsylla cheopis, a common cyclical vector of T. lewisi; Polyplax spinulosa, a reported mechanical vector; and Laelaps echidnina and Laelaps lamborni, 2 rodent mites of Rattus norvegicus in Durban, South Africa. In total, 379 R. norvegicus individuals were live-trapped at 48 sites in 4 locality types around Durban during a 1-yr period. Rats were euthanized, cardiac blood was taken to check for hemoparasites, and ectoparasites were removed for identification. Parasite species richness was higher in pups (2.11) and juveniles (1.02) than adults (0.87). Most rats in the study harbored 1 or 2 of the 5 parasites surveyed. Rats with trypanosomes and fleas were more prevalent in the city center and harbor, where juveniles were most affected. Rats with lice were more prevalent in informal settlements and urban/peri-urban areas, where pups had the highest infestations. There was a significant positive association between rats with fleas and trypanosomes and a negative association between rats with lice and trypanosomes. Location and rat age were significant predictors of T. lewisi, X. cheopis, and P. spinulosa. Mites showed no strong association with trypanosomes. Ectoparasite associations are possibly habitat and life-cycle related. We conclude that Durban's city center, which offers rats harborage, an unsanitary environment, and availability of food, is a high-transmission area for fleas and trypanosomes, and consequently a potential public health risk.

Landscape epidemiology in urban environments: The example of rodent-borne Trypanosoma in Niamey, Niger.

Trypanosomes are protozoan parasites found worldwide, infecting humans and animals. In the past decade, the number of reports on atypical human cases due to Trypanosoma lewisi or T. lewisi-like has increased urging to investigate the multiple factors driving the disease dynamics, particularly in cities where rodents and humans co-exist at high densities. In the present survey, we used a species distribution model, Maxent, to assess the spatial pattern of Trypanosoma-positive rodents in the city of Niamey. The explanatory variables were landscape metrics describing urban landscape composition and physiognomy computed from 8 land-cover classes. We computed the metrics around each data location using a set of circular buffers of increasing radii (20m, 40m, 60m, 80m and 100m). For each spatial resolution, we determined the optimal combination of feature class and regularization multipliers by fitting Maxent with the full dataset. Since our dataset was small (114 occurrences) we expected an important uncertainty associated to data partitioning into calibration and evaluation datasets. We thus performed 350 independent model runs with a training dataset representing a random subset of 80% of the occurrences and the optimal Maxent parameters. Each model yielded a map of habitat suitability over Niamey, which was transformed into a binary map implementing a threshold maximizing the sensitivity and the specificity. The resulting binary maps were combined to display the proportion of models that indicated a good environmental suitability for Trypanosoma-positive rodents. Maxent performed better with landscape metrics derived from buffers of 80m. Habitat suitability for Trypanosoma-positive rodents exhibited large patches linked to urban features such as patch richness and the proportion of landscape covered by concrete or tarred areas. Such inferences could be helpful in assessing areas at risk, setting of monitoring programs, public and medical staff awareness or even vaccination campaigns.

Diagnosis and genetic analysis of the worldwide distributed Rattus-borne Trypanosoma (Herpetosoma) lewisi and its allied species in blood and fleas of rodents.

Trypanosoma (Herpetosoma) lewisi is a cosmopolitan parasite of rodents strongly linked to the human dispersal of Rattus spp. from Asia to the rest of the world. This species is highly phylogenetically related to trypanosomes from other rodents (T. lewisi-like), and sporadically infects other mammals. T. lewisi may opportunistically infect humans, and has been considered an emergent rat-borne zoonosis associated to poverty. We developed the THeCATL-PCR based on Cathepsin L (CATL) sequences to specifically detect T. (Herpetosoma) spp., and assess their genetic diversity. This method exhibited high sensitivity using blood samples, and is the first molecular method employed to search for T. lewisi in its flea vectors. THeCATL-PCR surveys using simple DNA preparation from blood preserved in ethanol or filter paper detected T. lewisi in Rattus spp. from human dwellings in South America (Brazil and Venezuela), East Africa (Mozambique), and Southeast Asia (Thailand, Cambodia and Lao PDR). In addition, native rodents captured in anthropogenic and nearby human settlements in natural habitats harbored T. (Herpetosoma) spp. PCR-amplified CATL gene fragments (253bp) distinguish T. lewisi and T. lewisi-like from other trypanosomes, and allow for assessment of genetic diversity and relationships among T. (Herpetosoma) spp. Our molecular surveys corroborated worldwide high prevalence of T. lewisi, incriminating Mastomys natalensis as an important carrier of this species in Africa, and supported its spillover from invader Rattus spp. to native rodents in Brazil and Mozambique. THeCATL-PCR provided new insights on the accurate diagnosis and genetic repertoire of T. (Herpetosoma) spp. in rodent and non-rodent hosts, revealing a novel species of this subgenus in an African gerbil. Phylogenetic analysis based on CATL sequences from T. (Herpetosoma) spp. and other trypanosomes (amplified using pan-trypanosome primers) uncovered rodents harboring, beyond mammal trypanosomes of different subgenera, some species that clustered in the lizard-snake clade of trypanosomes.

Molecular survey of rodent-borne Trypanosoma in Niger with special emphasis on T. lewisi imported by invasive black rats.

Invading rodent species can harbor parasites with potential transmission to native rodents and/or humans. To investigate trypanosomes prevalence in rodents, the spleen of 76 rodents from Niger identified by their karyotype was used as a DNA source for Trypanosoma detection using a newly developed qPCR assay. Of the invasive black rat, Rattus rattus, 71% (10/14) were PCR positive as well as 6% (4/62) of native African rodents. Sequences of ~400bp of the SSU rDNA gene identified phylogenetically close Trypanosoma lineages. Trypanosoma lewisi was present in all positive black rats and the sequences displayed 100% similarity with T. lewisi-infected humans in Senegal. T. lewisi was also detected in one Acomys johannis, suggesting a possible transmission to native species. In addition to improved knowledge of Trypanosoma diversity in rodents, our data underscore the introduction of the potentially pathogenic T. lewisi kinetoplastid through the human-mediated invasion of black rats all over West Africa.

Diagnosis of a Trypanosoma lewisi-like (Herpetosoma) infection in a sick infant from Thailand.

Trypanosomes were observed in a peripheral blood smear from a 45-day-old Thai infant displaying fever, anaemia, cough and anorexia. Human trypanosomiasis is not endemic to Thailand, so parasite identification was undertaken to determine likely sources of the infection. Several morphological parameters of the trypanosomes were similar to those of Trypanosoma evansi and statistically different from those of Trypanosoma lewisi-like parasites from a naturally infected indigenous rat. However, duplicate PCR assays with primers flanking trypanosome rRNA internal transcribed spacer 1 (ITS1) resulted in amplicons of approximately 623 bp that corresponded to the expected size for T. lewisi-like parasites. The ITS1 sequence from the infant's blood was 98 and 49 % identical to T. lewisi and T. evansi sequences, respectively. Based on molecular results, it was concluded that the infant was infected with a T. lewisi-like (Herpetosoma) species.

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.

[The cases of infection of brown rats Rattus norvegicus with Trypanosoma lewisi (Kent, 1880) Laveran i Mesnil, 1901, in the area of Warsaw agglomeration]. / Przypadki zarazenia szczurów wedrownych Rattus norvegicus (Berkenhout, 1769) swidrowcem Trypanosoma lewisi (Kent, 1880) Laveran i Mesnil, 1901, na terenie aglomeracji warszawskiej.

Two from three brown rats (Rattus norvegicus) catched in Milan6wek near Warsaw, and one catched in the centre of Warsaw were infected with Trypanosoma lewisi. The morphometric features of trypanosomes were in accordance with the features of T. lewisi gived by other authors. This is first note about infection of free living rats with T. lewisi in Poland.

An unusual morphological type of Trypanosoma (Herpetosoma) lewisi (Kent, 1880) detected in the blood of Rattus norvegicus in India.

An unusual morphological type of Trypanosoma (Herpetosoma) lewisi (Kent, 1880) which was detected in Rattus norvegicus in India is reported in the present study. This type is different from known types of T. lewisi in that the kinetoplast is at a greater distance from the posterior end (P-K) than the usual type. The total length, including the free flagellum, is 35.3-39.3 microns and P-K is 11.9-15.0 as against total length of 21 to 36.5 microns in the normal form.

Isoenzyme characterization of trypanosomes of the subgenus Herpetosoma.

Isoenzyme analysis was used to characterize 6 species of trypanosomes of the subgenus Herpetosoma using 13 different enzyme systems. The species studied were Trypanosoma lewisi, T. musculi, T. grosi, T. microti, T. evotomys and T. nabiasi which cannot be distinguished on morphological grounds. Extracts for thin-layer starch-gel electrophoresis were prepared from cultures of insect forms in either Schneider's Drosophila or Grace's insect tissue culture media with foetal calf serum or a nutrient agar medium. Extracts of T. lewisi and T. musculi bloodstream forms were also run for comparison. All parasites gave distinct patterns which enabled them to be differentiated on one or more enzyme systems. Two types of computer analysis were used to group the parasites; using these techniques the murine parasites T. lewisi, T. musculi and T. grosi fell into one broad group, and T. microti and T. evotomys of microtine rodents formed another. These findings are in accord with earlier observations on the behavioural characteristics of these parasites in their mammalian host and their vector (fleas). The clear differences observed provide the basis for the application of other biochemical and immunological techniques for differentiation within this subgenus of trypanosomes.