Detection of infections of Trypanosoma grayi in Glossina fuscipes fuscipes in the Central African Republic

Symbiotic bacteria Sodalis glossinidius, Spiroplasma sp and Wolbachia do not favour Trypanosoma grayi coexistence in wild population of tsetse flies collected in Bobo-Dioulasso, Burkina Faso

BACKGROUND

Tsetse flies, the biological vectors of African trypanosomes, have established symbiotic associations with different bacteria. Their vector competence is suggested to be affected by bacterial endosymbionts. The current study provided the prevalence of three tsetse symbiotic bacteria and trypanosomes in Glossina species from Burkina Faso.

RESULTS

A total of 430 tsetse flies were captured using biconical traps in four different collection sites around Bobo-Dioulasso (Bama, Bana, Nasso, and Peni), and their guts were removed. Two hundred tsetse were randomly selected and their guts were screened by PCR for the presence of Sodalis glossinidius, Spiroplasma sp., Wolbachia and trypanosomes. Of the 200 tsetse, 196 (98.0%) were Glossina palpalis gambiensis and 4 (2.0%) Glossina tachinoides. The overall symbiont prevalence was 49.0%, 96.5%, and 45.0%, respectively for S. glossinidius, Spiroplasma and Wolbachia. Prevalence varied between sampling locations: S. glossinidius (54.7%, 38.5%, 31.6%, 70.8%); Spiroplasma (100%, 100%, 87.7%, 100%); and Wolbachia (43.4%, 38.5%, 38.6%, 70.8%), respectively in Bama, Bana, Nasso and Peni. Noteworthy, no G. tachnoides was infected by S. glossinidius and Wolbachia, but they were all infected by Spiroplasma sp. A total of 196 (98.0%) harbored at least one endosymbionts. Fifty-five (27.5%) carried single endosymbiont. Trypanosomes were found only in G. p. gambiensis, but not G. tachinoides. Trypanosomes were present in flies from all study locations with an overall prevalence of 29.5%. In Bama, Bana, Nasso, and Peni, the trypanosome infection rate was respectively 39.6%, 23.1%, 8.8%, and 37.5%. Remarkably, only Trypanosoma grayi was present. Of all trypanosome-infected flies, 55.9%, 98.3%, and 33.9% hosted S. glossinidius, Spiroplasma sp and Wolbachia, respectively. There was no association between Sodalis, Spiroplasma and trypanosome presence, but there was a negative association with Wolbachia presence. We reported 1.9 times likelihood of trypanosome absence when Wolbachia was present.

CONCLUSION

This is the first survey reporting the presence of Trypanosoma grayi in tsetse from Burkina Faso. Tsetse from these localities were highly positive for symbiotic bacteria, more predominantly with Spiroplasma sp. Modifications of symbiotic interactions may pave way for disease control.

Symbiotic bacteria Sodalis glossinidius, Spiroplasma sp and Wolbachia do not favour Trypanosoma grayi coexistence in wild population of tsetse flies collected in Bobo-Dioulasso, Burkina Faso

Background

Tsetse flies, the biological vectors of African trypanosomes, have established symbiotic associations with different bacteria. Their vector competence is suggested to be affected by bacterial endosymbionts. The current study provided the prevalence of three tsetse symbiotic bacteria and trypanosomes in Glossina species from Burkina Faso.

Results

A total of 430 tsetse flies were captured using biconical traps in four different collection sites around Bobo-Dioulasso (Bama, Bana, Nasso, and Peni), and their guts were removed. Two hundred tsetse were randomly selected and their guts were screened byPCR for the presence of Sodalis glossinidius, Spiroplasmasp., Wolbachia and trypanosomes. Of the 200 tsetse, 196 (98.0%) were Glossina palpalis gambienseand 4 (2.0%) Glossina tachinoides. The overall symbiont prevalence was 49.0%, 96.5%, and 45.0%, respectively for S. glossinidius, Spiroplasma and Wolbachia. Prevalence varied between sampling locations: S. glossinidius(54.7%, 38.5%, 31.6%, 70.8%); Spiroplasma (100%, 100%, 87.7%, 100%); and Wolbachia(43.4%, 38.5%, 38.6%, 70.8%),respectively in Bama, Bana, Nasso and Peni. Noteworthy, no G. tachhnoideswas infected by S. glossinidius and Wolbachia, but they were all infected by Spiroplasma sp. A total of 196 (98.0 %) harbored at least one endosymbionts. Fifty-five (27.5%) carried single endosymbiont. Trypanosomes were found only in G.p. gambiense, but not G. tachinoides. Trypanosomes were present in flies from all study locations with an overall prevalence of 29.5%. In Bama, Bana, Nasso, and Peni, the trypanosome infection rate was respectively 39.6%, 23.1%, 8.8%, and 37.5%. Remarkably, only Trypanosoma grayi was present. Of all trypanosome-infected flies, 55.9%, 98.3%, and 33.9% hosted S. glossinidius, Spiroplasma sp and Wolbachia, respectively. There was no association between Sodalis, Spiroplasma and trypanosome presence, but there was a negative association with Wolbachia presence. We reported1.9 times likelihood of trypanosome absence when Wolbachia was present.

Conclusion

This is the first survey reporting the presence of Trypanosoma grayi in tsetse from Burkina Faso. Tsetse from these localities were highly positive for symbiotic bacteria, more predominantly with Spiroplasma sp. Modifications of symbiotic interactions may pave way for disease control.

Molecular screening of tsetse flies and cattle reveal different Trypanosoma species including T. grayi and T. theileri in northern Cameroon

BACKGROUND

African trypanosomes are mainly transmitted through the bite of tsetse flies (Glossina spp.). The present study investigated the occurrence of pathogenic trypanosomes in tsetse flies and cattle in tsetse fly-infested areas of Northern Cameroon.

RESULTS

Trypanosomes were identified using nested polymerase chain reaction (PCR) analysis of internal transcribed spacer 1 (ITS1) region, both by size estimation and sequencing of PCR products. Apparent density indices recorded in Gamba and Dodeo were 3.1 and 3.6 tsetse flies per trap and day, respectively. Trypanosoma prevalence infection rate for the tsetse fly gut (40%) and proboscis (19%) were recorded. Among the flies where trypanosomes were detected in the gut, 41.7% were positive for T. congolense and 14.6% for T. brucei ssp., whereas in the proboscis 36% harboured T. congolense and 62% contained T. vivax. T. grayi was highly prevalent in tsetse fly gut (58%). The most common mixed infections were the combination of T. congolense and T. grayi. Trypanosome prevalence rate in cattle blood was 6%. Among these, T. vivax represented 26%, T. congolense 35%, T. brucei ssp. 17% and T. theileri 17% of the infections. Surprisingly, in one case T. grayi was found in cattle. The mean packed cell volume (PCV) of cattle positive for trypanosomes was significantly lower (24.1 ± 5.6%; P < 0.05) than that of cattle in which trypanosomes were not detected (27.1 ± 4.9%). Interestingly, the occurrence of T. theileri or T. grayi DNA in cattle also correlated with low PCV at pathological levels.

CONCLUSION

This molecular epidemiological study of Trypanosoma species in Northern Cameroon revealed active foci of trypanosomes in Dodeo and Gamba. These findings are relevant in assessing the status of trypanosomosis in these regions and will serve as a guide for setting the priorities of the government in the control of the disease.

Remarkable richness of trypanosomes in tsetse flies (Glossina morsitans morsitans and Glossina pallidipes) from the Gorongosa National Park and Niassa National Reserve of Mozambique revealed by fluorescent fragment length barcoding (FFLB)

Trypanosomes of African wild ungulates transmitted by tsetse flies can cause human and livestock diseases. However, trypanosome diversity in wild tsetse flies remains greatly underestimated. We employed FFLB (fluorescent fragment length barcoding) for surveys of trypanosomes in tsetse flies (3086) from the Gorongosa National Park (GNP) and Niassa National Reserve (NNR) in Mozambique (MZ), identified as Glossina morsitans morsitans (GNP/NNR=77.6%/90.5%) and Glossina pallidipes (22.4%/9.5%). Trypanosomes were microscopically detected in 8.3% of tsetse guts. FFLB of gut samples revealed (GNP/NNR): Trypanosoma congolense of Savannah (27%/63%), Kilifi (16.7%/29.7%) and Forest (1.0%/0.3%) genetic groups; T. simiae Tsavo (36.5%/6.1%); T. simiae (22.2%/17.7%); T. godfreyi (18.2%/7.0%); subgenus Trypanozoon (20.2%/25.7%); T. vivax/T. vivax-like (1.5%/5.2%); T. suis/T. suis-like (9.4%/11.9%). Tsetse proboscises exhibited similar species composition, but most prevalent species were (GNP/NNR): T. simiae (21.9%/28%), T. b. brucei (19.2%/31.7%), and T. vivax/T. vivax-like (19.2%/28.6%). Flies harboring mixtures of trypanosomes were common (~ 64%), and combinations of more than four trypanosomes were especially abundant in the pristine NNR. The non-pathogenic T. theileri was found in 2.5% while FFLB profiles of unknown species were detected in 19% of flies examined. This is the first report on molecular diversity of tsetse flies and their trypanosomes in MZ; all trypanosomes pathogenic for ungulates were detected, but no human pathogens were detected. Overall, two species of tsetse flies harbor 12 species/genotypes of trypanosomes. This notable species richness was likely uncovered because flies were captured in wildlife reserves and surveyed using the method of FFLB able to identify, with high sensitivity and accuracy, known and novel trypanosomes. Our findings importantly improve the knowledge on trypanosome diversity in tsetse flies, revealed the greatest species richness so far reported in tsetse fly of any African country, and indicate the existence of a hidden trypanosome diversity to be discovered in African wildlife protected areas.

Molecular Characterization of a Novel Family of Trypanosoma cruzi Surface Membrane Proteins (TcSMP) Involved in Mammalian Host Cell Invasion

Background

The surface coat of Trypanosoma cruzi is predominantly composed of glycosylphosphatidylinositol-anchored proteins, which have been extensively characterized. However, very little is known about less abundant surface proteins and their role in host-parasite interactions.

Methodology/ Principal Findings

Here, we described a novel family of T. cruzi surface membrane proteins (TcSMP), which are conserved among different T. cruzi lineages and have orthologs in other Trypanosoma species. TcSMP genes are densely clustered within the genome, suggesting that they could have originated by tandem gene duplication. Several lines of evidence indicate that TcSMP is a membrane-spanning protein located at the cellular surface and is released into the extracellular milieu. TcSMP exhibited the key elements typical of surface proteins (N-terminal signal peptide or signal anchor) and a C-terminal hydrophobic sequence predicted to be a trans-membrane domain. Immunofluorescence of live parasites showed that anti-TcSMP antibodies clearly labeled the surface of all T. cruzi developmental forms. TcSMP peptides previously found in a membrane-enriched fraction were identified by proteomic analysis in membrane vesicles as well as in soluble forms in the T. cruzi secretome. TcSMP proteins were also located intracellularly likely associated with membrane-bound structures. We demonstrated that TcSMP proteins were capable of inhibiting metacyclic trypomastigote entry into host cells. TcSMP bound to mammalian cells and triggered Ca²⁺ signaling and lysosome exocytosis, events that are required for parasitophorous vacuole biogenesis. The effects of TcSMP were of lower magnitude compared to gp82, the major adhesion protein of metacyclic trypomastigotes, suggesting that TcSMP may play an auxiliary role in host cell invasion.

Conclusion/Significance

We hypothesized that the productive interaction of T. cruzi with host cells that effectively results in internalization may depend on diverse adhesion molecules. In the metacyclic forms, the signaling induced by TcSMP may be additive to that triggered by the major surface molecule gp82, further increasing the host cell responses required for infection.

Trypanosoma cruzi is the etiologic agent of Chagas’ disease, which infects 6–7 million people worldwide, mostly in Latin America. Currently, there are no vaccines available, and the drugs used for treatment are toxic and are not fully effective. To infect mammalian hosts, T. cruzi relies on the ability to invade host cells, replicate intracellularly and spread the infection in different organs of the mammalian host. Knowledge of the structure and function of T. cruzi surface molecules is fundamental to understanding the mechanisms by which the parasite interacts with its host. T. cruzi infective forms engage a repertoire of surface and secreted molecules, some of which are involved in triggering signaling pathways both in the parasite and the host cell, leading to intracellular Ca²⁺ mobilization, a process essential for parasite internalization. Here, we described a novel family of T. cruzi surface membrane proteins (TcSMP), including their genomic distribution, expression and cellular localization. We studied the mechanism of action of TcSMP in host-cell invasion and proposed a triggering role for TcSMP in host-cell lysosome exocytosis during metacyclic internalization. TcSMP genes are conserved among different T. cruzi lineages and share orthologs in other Trypanosoma species. These results suggest that the diversification of TcSMP genes in mammalian trypanosomes occurred after continental drift. In T. cruzi this gene family expanded by gene duplication.

The phylogeography of trypanosomes from South American alligatorids and African crocodilids is consistent with the geological history of South American river basins and the transoceanic dispersal of Crocodylus at the Miocene

Background

Little is known about the diversity, phylogenetic relationships, and biogeography of trypanosomes infecting non-mammalian hosts. In this study, we investigated the influence of host species and biogeography on shaping the genetic diversity, phylogenetic relationship, and distribution of trypanosomes from South American alligatorids and African crocodilids.

Methods

Small Subunit rRNA (SSU rRNA) and glycosomal Glyceraldehyde Phosphate Dehydrogenase (gGAPDH) genes were employed for phylogenetic inferences. Trypanosomes from crocodilians were obtained by haemoculturing. Growth behaviour, morphology, and ultrastructural features complement the molecular description of two new species strongly supported by phylogenetic analyses.

Results

The inferred phylogenies disclosed a strongly supported crocodilian-restricted clade comprising three subclades. The subclade T. grayi comprised the African Trypanosoma grayi from Crocodylus niloticus and tsetse flies. The subclade T. ralphi comprised alligatorid trypanosomes represented by Trypanosoma ralphi n. sp. from Melanosuchus niger, Caiman crocodilus and Caiman yacare from Brazilian river basins. T. grayi and T. ralphi were sister subclades. The basal subclade T. terena comprised alligatorid trypanosomes represented by Trypanosoma terena n. sp. from Ca. yacare sharing hosts and basins with the distantly genetic related T. ralphi. This subclade also included the trypanosome from Ca. crocodilus from the Orinoco basin in Venezuela and, unexpectedly, a trypanosome from the African crocodilian Osteolaemus tetraspis.

Conclusion

The close relationship between South American and African trypanosomes is consistent with paleontological evidence of recent transoceanic dispersal of Crocodylus at the Miocene/Pliocene boundaries (4–5 mya), and host-switching of trypanosomes throughout the geological configuration of South American hydrographical basins shaping the evolutionary histories of the crocodilians and their trypanosomes.

Tsetse fly blood meal modification and trypanosome identification in two sleeping sickness foci in the forest of southern Cameroon

The blood meal origins of 222 tsetse flies (213 Glossina palpalis palpalis, 7 Glossina pallicera pallicera, one Glossina nigrofusca and one Glossina caliginea) caught in 2008 in two Human African trypanosomiasis foci (Bipindi and Campo) of south Cameroon were investigated. 88.7% of tsetse flies blood meals were identified using the heteroduplex method and the origin of the remaining blood meals (11.3%) was identified by sequencing the cytochrome B gene. Most of the meals were from humans (45.9%) and pigs (37.4%), 16.7% from wild animals. Interestingly, new tsetse fly hosts including turtle (Trionyx and Kinixys) and snake (Python sebae) were identified. Significant differences were recorded between Bipindi where the blood meals from pigs were predominant (66.7% vs 23.5% from humans) and Campo where blood meals from humans were predominant (62.9% vs 22.7% from pigs). Comparison with the data recorded in 2004 in the same foci (and with the same molecular approach) demonstrated significant modifications of the feeding patterns: increase in blood meals from pigs in Bipindi (66.7% in 2008 vs 44.8% in 2004) and in Campo (20.5% in 2008 vs 6.8% in 2004), decrease in that from human (significant in Bipindi only). 12.6%, 8.1% and 2.7% of the flies were, respectively, Trypanosoma congolense forest type, Trypanosoma congolense savannah type and Trypanosoma brucei gambiense infected. These results demonstrate that tsetse fly feeding patterns can be specific of a given area and can evolve rapidly with time. They show an active circulation of a variety of trypanosomes in sleeping sickness foci of southern Cameroon.

African trypanosomes: celebrating diversity

Recent advances in molecular identification techniques and phylogenetic analysis have revealed the presence of previously unidentified tsetse-transmitted trypanosomes in Africa. This is surprising in a comparatively well-known group of pathogens that includes the causative agents of human and animal trypanosomiasis. Despite levels of genetic divergence that warrant taxonomic recognition, only one of these new trypanosomes has been named as a new species; the increased diversity is largely ignored or regarded as an inconvenient complication. Yet, some of these trypanosomes have demonstrated pathogenicity, whereas others are closely related to known pathogens, and might share this trait. We should first acknowledge that these novel trypanosomes exist and then take steps to investigate their host range, pathogenicity to livestock and response to chemotherapy.

The use of specific and generic primers to identify trypanosome infections of wild tsetse flies in Tanzania by PCR

The accurate identification of trypanosome species and subspecies remains a challenging task in the epidemiology of human and animal trypanosomiasis in tropical Africa. Currently, there are specific PCR tests to identify about 10 different species, subspecies or subgroups of African tsetse-transmitted trypanosomes. These PCR tests have been used here to identify trypanosomes in four species of tsetse (Glossina brevipalpis, G. pallidipes, G. swynnertoni, G. morsitans morsitans) from two areas of Tanzania. PCR using species-specific primers was performed on 1041 dissection-positive proboscides, giving an overall positive identification in 254 (24%). Of these, 61 proboscides (24%) contained two or more trypanosomes. The trypanosome with the greatest overall prevalence at both field sites was Trypanosoma simiae Tsavo, which was identified in a total of 118 infected tsetse proboscides (46%). At Pangani, T. godfreyi was found in G. pallidipes but not in G. brevipalpis, suggesting that these flies might have different susceptibility to this trypanosome or might have fed on a different range of hosts. A high proportion (about 75%) of trypanosome infections remained unidentified. To investigate the identity of these unidentified samples, we used primers complementary to the conserved regions of trypanosomal small subunit ribosomal RNA (ssu rRNA) genes to amplify variable segments of the gene. Amplified DNA fragments were cloned, sequenced and compared with ssu rRNA genes on database of known trypanosome species. In this way, we have tentatively identified two new trypanosomes: a trypanosome related to Trypanosoma vivax and a trypanosome related to T. godfreyi. The T. godfreyi-related trypanosome occurred frequently in the Tanzanian field samples and appears to be widespread. Molecular identification of these two new trypanosomes should now facilitate their isolation and full biological characterisation.

Epidemiology and diagnosis of African trypanosomiasis using DNA probes

The accurate identification of trypanosome species has been a challenging problem in the epidemiology of African trypanosomiasis, both human and animal. The last 10 years have seen great progress through the application of deoxyribonucleic acid (DNA) probe technology, although this has also revealed greater complexity than supposed. While a single repetitive DNA probe can identify all members of the subgenus Trypanosoma (Trypanozoon), including the human pathogens T. brucei gambiense and T. b. rhodesiense as well as the non-tsetse-transmitted trypanosomes T. evansi and T. equiperdum, at least 6 probes are needed to distinguish members of the subgenus Nannomonas, in which only 2 species, T. congolense and T. simiae, were previously recognized. Similarly, the subgenus Duttonella appears to consist of more than one species. Use of this battery of DNA probes to identify the trypanosomes carried by tsetse flies in the field has yielded some surprises about the accuracy (or inaccuracy) of previous identification methods. An unexpectedly high prevalence of mixed infections has been found in all the field studies carried out so far. The large number of infections that remain unidentified by the available probes suggests the existence of other, as yet unknown, trypanosome species. Limited use of the polymerase chain reaction has been made for diagnosis of human and animal trypanosomiasis, due to its high cost.

Microsatellite DNA markers reveal genetic differentiation among populations of Glossina palpalis gambiensis collected in the agro-pastoral zone of Sideradougou, Burkina Faso

Intraspecific genetic variability of Glossina palpalis gambiensis in the area of Sideradougou, Burkina Faso, was studied using polymorphic microsatellite DNA markers. This genetic study was combined with other epidemiological information on the same tsetse: bloodmeal identification, dissection of tsetse and molecular characterization of the trypanosomes detected. There was significant genetic differentiation among flies caught only a few kilometers apart, within the same riverine habitat. These distinct subpopulations were also differentially infected by trypanosomes. In part of the study area, a Factorial Correspondence Analysis undertaken on the genotypes allowed us to detect a Wahlund effect, suggesting the presence of tsetse originating from different source populations coming from two distinct drainage systems. The apparent structuring of populations of G. palpalis gambiensis is discussed relative to appropriate strategies to control African Trypanosomosis.

Isolation of Trypanosoma brucei from the monitor lizard (Varanus niloticus) in an endemic focus of Rhodesian sleeping sickness in Kenya

Monitor lizards were sampled along the shores of Lake Victoria to detect natural infections of potentially human-infective trypanosomes. In an area with endemic rhodesian sleeping sickness, one of 19 lizards was infected (Busia, Kenya). Six of ten lizards also showed indirect evidence of infection with Trypanosoma brucei (antibody ELISA). In an area with no recent history of human disease (Rusinga Island), no parasites were found and no antibodies to T. brucei were detected. The isolate was identified as T. brucei through xenodiagnosis (completion of the life cycle in the salivary glands of tsetse), and through molecular techniques (positive reactions with a PCR primer and a microsatellite DNA probe characteristic of the subgenus Trypanozoon). Experimental infections of monitor lizards were also attempted with a variety of parasites and tsetse species. It was possible to infect monitor lizards with T. brucei but not with forest or savannah genotypes of Trypanosoma congolense. Parasites reached low levels of parasitaemia for a short period without generating any pathology; they also remained infective to tsetse and laboratory rats. The implications of these findings are discussed in relation to the endemicity of sleeping sickness.

Detection and identification of trypanosomes by polymerase chain reaction in wild tsetse flies in Cameroon

The prevalence of various species and subgroups of trypanosomes in infected flies from three sleeping sickness foci in Cameroon was determined by the use of polymerase chain reaction (PCR). The predominant tsetse species found were Glossina palpalis palpalis. Microscopical examination of 943 non-teneral tsetse flies revealed an average infection rate of 10.4%. A total of 90 flies were analyzed for trypanosome identification with primer sets specific for Trypanosoma (Trypanozoon) brucei s.l., T. (Duttonella) vitax, T. (Nannomonas) simiae, and forest type T. (Nannomonas) congolense. PCR succeeded in identifying 52 of the 90 infected flies. Other primers were also tested on microscope positive/PCR-negative infections, and trypanosome subgroups were detected (Kilifi type and savannah type T. congolense). PCR amplification allowed identification of immature infections and revealed mixed-infections. The PCR technique failed to identify 42.2% (38/90) of the parasitologically positive flies and the reasons for this failure are discussed.