Stéphane Herder

First isolation of Enterobacter, Enterococcus, and Acinetobacter spp. as inhabitants of the tsetse fly (Glossina palpalis palpalis) midgut

This paper reports the first evidence of the presence of bacteria, other than the three previously described as symbionts, Wigglesworthia glossinidia, Wolbachia, and Sodalis glossinidius, in the midgut of Glossina palpalis palpalis, the tsetse fly, a vector of the chronic form of human African trypanosomiasis in sub-Saharan African countries. Based on the morphological, nutritional, physiological, and phylogenetic results, we identified Enterobacter, Enterococcus, and Acinetobacter spp. as inhabitants of the midgut of the tsetse fly from Angola. Enterobacter spp. was the most frequently isolated. The role of these bacteria in the gut, in terms of vector competence of the tsetse fly, is discussed, as is the possibility of using these bacteria to produce in situ trypanolytic molecules.

A Clinical and Epidemiological Investigation of the First Reported Human Infection With the Zoonotic Parasite Trypanosoma evansi in Southeast Asia

We show that the bovid-associated parasite Trypanosoma evansi is endemic in Vietnam and has zoonotic potential. Our study describes the first laboratory-confirmed human case of T. evansi in a previously healthy individual without apolipoprotein L1 deficiency.

Molecular prevalence of Trypanosoma spp. in wild rodents of Southeast Asia: influence of human settlement habitat.

SUMMARYnThis study investigated the molecular prevalence of Trypanosoma lewisi and T. evansi in wild rodents from Cambodia, Lao PDR and Thailand. Between 2008 and 2012, rodents (and shrews) were trapped in nine locations and 616 of these were tested using three sets of primers: TRYP1 (amplifying ITS1 of ribosomal DNA of all trypanosomes), TBR (amplifying satellite genomic DNA of Trypanozoon parasites) and LEW1 (amplifying ITS1 of ribosomal DNA of T. lewisi). Based on the size of the PCR products using TRYP1, 17% were positive for T. lewisi and 1·0% positive for Trypanozoon. Results were confirmed by sequencing PCR products and by using more specific primers (LEW1 and TBR). The specificity of TRYP1 primers, however, failed as rodent DNA was amplified in some instances, giving unexpected product sizes. Using LEW1 primers, 13·3% of the samples were confirmed positive for T. lewisi, both by PCR and sequencing. In Thailand, T. lewisi was found in Rattus tanezumi, R. exulans and Berylmys; in Lao PDR, in R. tanezumi and R. exulans, and in Cambodia in R. tanezumi, R. exulans and R. norvegicus. Using TBR, 1·3% of the samples tested positive for Trypanozoon by PCR and sequencing; T. evansi is the only species of the Trypanozoon subgenus possibly present in wild Asian rodents. These results confirmed its presence in rodents from Thailand (R. tanezumi), Lao PDR (R. tanezumi, R. nitidus) and Cambodia (R. tanezumi, Niviventer fulvescens, Maxomys surifer). Based on the information related to rodent trapping, it was found that rodent species trapped in and around human dwellings had a higher prevalence of T. lewisi infection. R. tanezumi and R. exulans, two synanthropic species, were mainly found infected in this habitat suggesting a role as a reservoir and thus a potential source of T. lewisi for human infection.

From clonal to sexual: a step in T. congolense evolution?

Although clearly demonstrated in Trypanosoma brucei, genetic exchange remains controversial in other trypanosome species. Recently, Morrison and co-workers applied a population-genetics analysis, and established the existence of mating in Trypanosoma congolense. Starting from this original discovery, we focus here on the important question of how mating is induced during the trypanosome life cycle and discuss the use of statistics to evidence this type of non-obligatory biological process.

Comparison of the Performances of Five Primer Sets for the Detection and Quantification of Plasmodium in Anopheline Vectors by Real-Time PCR

Quantitative real-time polymerase chain reaction (qrtPCR) has made a significant improvement for the detection of Plasmodium in anopheline vectors. A wide variety of primers has been used in different assays, mostly adapted from molecular diagnosis of malaria in human. However, such an adaptation can impact the sensitivity of the PCR. Therefore we compared the sensitivity of five primer sets with different molecular targets on blood stages, sporozoites and oocysts standards of Plasmodium falciparum (Pf) and P. vivax (Pv). Dilution series of standard DNA were used to discriminate between methods at low concentrations of parasite and to generate standard curves suitable for the absolute quantification of Plasmodium sporozoites. Our results showed that the best primers to detect blood stages were not necessarily the best ones to detect sporozoites. Absolute detection threshold of our qrtPCR assay varied between 3.6 and 360 Pv sporozoites and between 6 and 600 Pf sporozoites per mosquito according to the primer set used in the reaction mix. In this paper, we discuss the general performance of each primer set and highlight the need to use efficient detection methods for transmission studies.

Identification of subspecies specific genes differentially expressed in procyclic forms of Trypanosoma brucei subspecies

Trypanosoma brucei subspecies undergo establishment and maturation in tsetse flies mid-gut and salivary glands, respectively. Successful establishment of trypanosomes in tsetse mid-gut as well as their migration to saliva gland depends on the ability of these parasites to adapt rapidly to new environmental conditions and to negotiate the physical barriers. To identify subspecies specific genes which are differentially regulated during the establishment of T. brucei subspecies in tsetse flies mid-gut, a comparative genomic analysis between different T. brucei subspecies was performed using microarrays containing about 23040 T. brucei shotgun fragments. The whole genome analyses of RNA expression profiles revealed about 274 significantly differentially expressed genes between T. brucei subspecies. About 7% of the differentially regulated clones did not match to any T. brucei predicted genes. Most of the differentially regulated transcripts are involved in transport across cell membrane and also in the purines metabolism. The genes selectively up regulated in T. brucei gambiense and T. brucei rhodesiense (human infective T. brucei) like snoRNA and HSP70 are expressed in response to stress. The high failure rate in the process of establishment and maturation of T. brucei gambiense during cyclical transmission in tsetse flies may result from the incapacity of this parasite to regulate its growth due to the expression of a variety of chaperones or heat shock proteins. Genes selectively up regulated in T. brucei brucei like NT8.1 nucleoside/nucleobase transporters and S-adenosylmethionine synthetase may favour the establishment of this subspecies in tsetse mid-gut. These genes appear as potential targets for investigations on the development of vaccine blocking the transmission of trypanosomes in tsetse flies.

Zoonotic trypanosomes in South East Asia: Attempts to control Trypanosoma lewisi using veterinary drugs.

A growing number of atypical human infections due to the livestock parasite Trypanosoma evansi, or to the rat parasite Trypanosoma lewisi, are reported in humans in Asia. In some cases, clinical evolutions request treatments, however, so far, there were very few attempts to control T.xa0lewisi using trypanocidal drugs. In a study published elsewhere, the efficacy of human trypanocides is evaluated in laboratory rats, and it concludes that none of them is able to cure rats experimentally infected with T.xa0lewisi. Control of T.xa0lewisi in rat would be a step for identification of drugs against this parasite. In the present study, 4 veterinary drugs: diminazene aceturate, isometamidium chloride, melarsomine hydrochloride and quinapyramine sulfate and chloride, were evaluated at low and high doses, in intra-muscular injections to normal rats experimentally infected with a stock of T.xa0lewisi from Thailand. None of these treatments being efficient, a trial was also made using melarsomine hydrochloride in T.xa0evansi infected rats and in mixed T.xa0lewisi and T.xa0evansi infected rats, in order to demonstrate the efficacy of the drugs under the present protocol. T.xa0evansi was cleared from the rats blood the day after the treatment, while, T.xa0lewisi remained unaffected until the end of the experiment. These observations clearly demonstrated the efficacy of melarsomine hydrochloride against T.xa0evansi and its inefficacy against T.xa0lewisi. In conclusion none of the veterinary drugs was efficient against this stock of T.xa0lewisi. Other protocols using higher doses or other drugs and T.xa0lewisi stocks should be investigated in further studies. The control of T.xa0lewisi infection in Wistar rats, using veterinary trypanocidal drugs, remains so far unsuccessful.

Trypanosoma rangeli is phylogenetically closer to Old World trypanosomes than to Trypanosoma cruzi

Trypanosoma rangeli and Trypanosoma cruzi are generalist trypanosomes sharing a wide range of mammalian hosts; they are transmitted by triatomine bugs, and are the only trypanosomes infecting humans in the Neotropics. Their origins, phylogenetic relationships, and emergence as human parasites have long been subjects of interest. In the present study, taxon-rich analyses (20 trypanosome species from bats and terrestrial mammals) using ssrRNA, glycosomal glyceraldehyde-3-phosphate dehydrogenase (gGAPDH), heat shock protein-70 (HSP70) and Spliced Leader RNA sequences, and multilocus phylogenetic analyses using 11 single copy genes from 15 selected trypanosomes, provide increased resolution of relationships between species and clades, strongly supporting two main sister lineages: lineage Schizotrypanum, comprising T. cruzi and bat-restricted trypanosomes, and Tra[Tve-Tco] formed by T. rangeli, Trypanosoma vespertilionis and Trypanosoma conorhini clades. Tve comprises European T. vespertilionis and African T. vespertilionis-like of bats and bat cimicids characterised in the present study and Trypanosoma sp. Hoch reported in monkeys and herein detected in bats. Tco included the triatomine-transmitted tropicopolitan T. conorhini from rats and the African NanDoum1 trypanosome of civet (carnivore). Consistent with their very close relationships, Tra[Tve-Tco] species shared highly similar Spliced Leader RNA structures that were highly divergent from those of Schizotrypanum. In a plausible evolutionary scenario, a bat trypanosome transmitted by cimicids gave origin to the deeply rooted Tra[Tve-Tco] and Schizotrypanum lineages, and bat trypanosomes of diverse genetic backgrounds jumped to new hosts. A long and independent evolutionary history of T. rangeli more related to Old World trypanosomes from bats, rats, monkeys and civets than to Schizotrypanum spp., and the adaptation of these distantly related trypanosomes to different niches of shared mammals and vectors, is consistent with the marked differences in transmission routes, life-cycles and host-parasite interactions, resulting in T. cruzi (but not T. rangeli) being pathogenic to humans.

Zoonotic trypanosomes in South East Asia: Attempts to control Trypanosoma lewisi using human and animal trypanocidal drugs

Beside typical human trypanosomes responsible of sleeping sickness in Africa and Chagas disease in Latin America, there is a growing number of reported atypical human infections due to Trypanosoma evansi, a livestock parasite, or Trypanosoma lewisi, a rat parasite, especially in Asia. Drugs available for the treatment of T. brucei ssp. in humans are obviously of choice for the control of T. evansi because it is derived from T. brucei. However, concerning T. lewisi, there is an urgent need to determine the efficacy of trypanocidal drugs for the treatment in humans. In a recent study, pentamidine and fexinidazole were shown to have the best efficacy against one stock of T. lewisi in rats. In the present study suramin, pentamidine, eflornitine, nifurtimox, benznidazole and fexinidazole, were evaluated at low and high doses, in single day administration to normal rats experimentally infected with a stock of T. lewisi recently isolated in Thailand. Because none of these treatments was efficient, a trial was made with the most promising trypanocide identified in a previous study, fexinidazole 100mg/kg, in 5 daily administrations. Results observed were unclear. To confirm the efficacy of fexinidazole, a mixed infection protocol was set up in cyclophosphamide immunosuppressed rats. Animals were infected successively by T. lewisi and T. evansi, and received 10 daily PO administrations of 200mg/kg fexinidazole. Drastic effects were observed against T. evansi which was cleared from the rats blood within 24 to 48h; however, the treatment did not affect T. lewisi which remained in high number in the blood until the end of the experiment. This mixed infection/treatment protocol clearly demonstrated the efficacy of fexinidazole against T. evansi and its inefficacy against T. lewisi. Since animal trypanocides were also recently shown to be inefficient, other protocols as well as other T. lewisi stocks should be investigated in further studies.