Genetic characterization of Trypanosoma brucei circulating in domestic animals of the Fontem sleeping sickness of Cameroon

Novel trypanosomatid species detected in Mongolian pikas (Ochotona pallasi) and their fleas in northwestern China

BACKGROUND

In the family Trypanosomatidae, the genus Trypanosoma contains protozoan parasites that infect a diverse range of hosts, including humans, domestic animals, and wildlife. Wild rodents, as natural reservoir hosts of various pathogens, play an important role in the evolution and emergence of Trypanosomatidae. To date, no reports are available on the trypanosomatid infection of pikas (Lagomorpha: Ochotonidae).

METHODS

In this study, Mongolian pikas and their fleas were sampled at the China-Mongolia border, northwestern China. The samples were analyzed with polymerase chain reaction (PCR) and sequencing for the presence of Trypanosomatidae on the basis of both the 18S ribosomal RNA (18S rRNA) gene and the glyceraldehyde-3-phosphate dehydrogenase (gGAPDH) gene. The morphology of trypomastigotes was also observed in peripheral blood smears by microscopy.

RESULTS

Molecular and phylogenetic analyses revealed a new genotype of the Trypanosoma lewisi clade that was found both in pika blood and flea samples. This genotype, which probably represents a new species, was provisionally designated as "Trypanosoma sp. pika". In addition, a novel genotype belonging to the genus Blechomonas of Trypanosomatidae was detected in fleas. On the basis of its molecular and phylogenetic properties, this genotype was named Blechomonas luni-like, because it was shown to be the closest related to B. luni compared with other flea-associated trypanosomatids.

CONCLUSIONS

To the best of our knowledge, this is the first study to report any trypanosomatid species in Mongolian pikas and their fleas. Further studies are needed to investigate the epidemiology of these protozoan parasites, as well as to evaluate their pathogenicity for humans or domestic animals.

Prevalence of blood and skin trypanosomes in domestic and wild fauna from two sleeping sickness foci in Southern Cameroon

Although studies on African Trypanosomiases revealed a variety of trypanosome species in the blood of various animal taxa, animal reservoirs of Trypanosoma brucei gambiense and anatomical niches such as skin have been overlooked in most epidemiological settings. This study aims to update epidemiological data on trypanosome infections in animals from human African trypanosomiasis (HAT) foci of Cameroon. Blood and skin snips were collected from 291 domestic and wild animals. DNA was extracted from blood and skin snips and molecular approaches were used to identify different trypanosomes species. Immunohistochemical analyses were used to confirm trypanosome infections in skin snips. PCR revealed 137 animals (47.1%) with at least one trypanosome species in the blood and/or in the skin. Of these 137 animals, 90 (65.7%) and 32 (23.4%) had trypanosome infections respectively in the blood and skin. Fifteen (10.9%) animals had trypanosome infections in both blood and skin snip. Animals from the Campo HAT focus (55.0%) were significantly (X2 = 17.6; P< 0.0001) more infected than those (29.7%) from Bipindi. Trypanosomes of the subgenus Trypanozoon were present in 27.8% of animals while T. vivax, T. congolense forest type and savannah type were detected in 16.5%, 10.3% and 1.4% of animals respectively. Trypanosoma b. gambiense infections were detected in the blood of 7.6% (22/291) of animals. No T. b. gambiense infection was detected in skin. This study highlights the presence of several trypanosome species in the blood and skin of various wild and domestic animals. Skin appeared as an anatomical reservoir for trypanosomes in animals. Despite methodological limitations, pigs, sheep, goats and wild animals were confirmed as potential reservoirs of T. b. gambiense. These animal reservoirs must be considered for the designing of control strategies that will lead to sustainable elimination of HAT.

Molecular Identification of Trypanosome Diversity in Domestic Animals Reveals the Presence of Trypanosoma brucei gambiense in Historical Foci of Human African Trypanosomiasis in Gabon

Human African Trypanosomiasis (HAT) is an infectious disease caused by protozoan parasites belonging to the Trypanosoma genus. In sub-Saharan Africa, there is a significant threat as many people are at risk of infection. Despite this, HAT is classified as a neglected tropical disease. Over the last few years, several studies have reported the existence of a wide diversity of trypanosome species circulating in African animals. Thus, domestic and wild animals could be reservoirs of potentially dangerous trypanosomes for human populations. However, very little is known about the role of domestic animals in maintaining the transmission cycle of human trypanosomes in central Africa, especially in Gabon, where serious cases of infection are recorded each year, sometimes leading to hospitalization or death of patients. Komo-Mondah, located within Estuaries (Gabonese province), stays the most active HAT disease focus in Gabon, with a mean of 20 cases per year. In this study, we evaluated the diversity and prevalence of trypanosomes circulating in domestic animals using the Polymerase Chain Reaction (PCR) technique. We found that 19.34% (53/274) of the domestic animals we studied were infected with trypanosomes. The infection rates varied among taxa, with 23.21% (13/56) of dogs, 16.10% (19/118) of goats, and 21.00% (21/100) of sheep infected. In addition, we have observed a global mixed rate of infections of 20.75% (11/53) among infected individuals. Molecular analyses revealed that at least six Trypanosome species circulate in domestic animals in Gabon (T. congolense, T. simiae, T. simiae Tsavo, T. theileri, T. vivax, T. brucei (including T. brucei brucei, and T. brucei gambiense)). In conclusion, our study showed that domestic animals constitute important potential reservoirs for trypanosome parasites, including T. brucei gambiense, which is responsible for HAT.

Spatial meta-analysis of the occurrence and distribution of tsetse-transmitted animal trypanosomiasis in Cameroon over the last 30 years

In Cameroon, >90% of cattle are considered exposed to African animal trypanosomiasis (AAT) infection, with the presence of tsetse rendering cattle husbandry as a very difficult proposition. A systematic review of data on AAT and tsetse from 1990 to 2021 was conducted to develop a national atlas. The review identified 74 relevant scientific documents, with three pathogenic Trypanosoma species (Trypanosoma vivax , T. congolense and T. brucei s.l.) most frequently identified as causing AAT. Trypanosoma grayi , T. theileri , T. simiae and the human African trypanosomiasis causative agent T. brucei gambiense were also identified in a wide range of hosts. The tsetse fly fauna of Cameroon comprises nine species, with Glossina palpalis palpalis and G. fuscipes fuscipes the most widely distributed following their identification in seven and five of the 10 regions, respectively. Two species, Glossina nigrofusca and G. pallicera pallicera appeared to be rare and were restricted to both forest and protected areas. The presence of AAT is associated with the presence of tsetse in the livestock–human–wildlife interface of Cameroon. AAT occurs beyond the tsetse belts of the country where mechanical vectors are abundant. This study provides AAT and tsetse maps to support ongoing interventions in Cameroon.

Molecular identification of Trypanosoma brucei gambiense in naturally infected pigs, dogs and small ruminants confirms domestic animals as potential reservoirs for sleeping sickness in Chad

Human African trypanosomiasis (HAT) has been targeted for zero transmission to humans by 2030. Animal reservoirs of gambiense-HAT could jeopardize these elimination goals. This study was undertaken to identify potential host reservoirs for Trypanosoma brucei gambiense by detecting its natural infections in domestic animals of Chadian HAT foci. Blood samples were collected from 267 goats, 181 sheep, 154 dogs, and 67 pigs. Rapid diagnostic test (RDT) and capillary tube centrifugation (CTC) were performed to search for trypanosomes. DNA was extracted from the buffy coat, and trypanosomes of the subgenus Trypanozoon as well as T. b. gambiense were identified by PCR. Of 669 blood samples, 19.4% were positive by RDT and 9.0% by CTC. PCR revealed 150 animals (22.4%) with trypanosomes belonging to Trypanozoon, including 18 (12%) T. b. gambiense. This trypanosome was found in all investigated animal species and all HAT foci. Between animal species or villages, no significant differences were observed in the number of animals harboring T. b. gambiense DNA. Pigs, dogs, sheep and goats appeared to be potential reservoir hosts for T. b. gambiense in Chad. The identification of T. b. gambiense in all animal species of all HAT foci suggests that these animals should be considered when designing new control strategies for sustainable elimination of HAT. Investigations aiming to decrypt their specific role in each epidemiological setting are important to achieve zero transmission of HAT.

Molecular identification of diminazene aceturate-resistant strains of Trypanosoma congolense in naturally infected domestic animals of Yoko in the centre region of Cameroon

African animal trypanosomiases (AAT) remain the major constraint for livestock production, agriculture and food security in Africa. Although several control measures have been developed to fight AAT, the use of trypanocides remains the main strategy in most affected poor and rural communities. However, several studies have highlighted drug-resistant-trypanosome infections in many African countries, though this phenomenon is still not well described. This study aims to detect trypanosome species and the molecular profiles of drug-resistant-trypanosomes in naturally infected domestic animals of Yoko in the centre region of southern Cameroon. Therefore, in October 2017, 348 animals were blood sampled. The level of packed cell volume (PCV) was evaluated in each animal and trypanosome infections were investigated with the capillary tube centrifugation technique (CTC). Thereafter, DNA was extracted from blood samples and different trypanosome species were identified by PCR. The resistant/sensitive molecular profiles of trypanosomes for diminazene aceturate (DA) and isometamidium chloride (ISM) were investigated by PCR-RFLP. About 18.4% (64/348) of animals analyzed by PCR were found with trypanosome infections including Trypanosoma vivax, Trypanosoma brucei s.l. and Trypanosoma congolense forest and savannah. Trypanosoma congolense savannah was the predominant species with an infection rate of 15.2%. Between villages, significant (p˂0.0001) differences were found in the overall trypanosome infection rates. No molecular profile for ISM resistant-trypanosomes was identified. Conversely, about 88.9% (40/45) of T. congolense positive samples have shown molecular profiles of DA-resistant strains while the remaining 11.1% (5/45) showed mixed molecular profiles of resistant/sensitive strains. Results showed that the molecular profiles of DA-resistant strains of T. congolense in domestic animals of Yoko were widespread. This data needs to be confirmed by testing in vivo the drug susceptibilities of the trypanosome strains herein detected. In conclusion, appropriate future control measures are required. In addition to the intensification of vector control, ISM is advised for the treatment of animals infected by trypanosomes.

The buffy coat method: a tool for detection of blood parasites without staining procedures

BACKGROUND

Blood parasites belonging to the Apicomplexa, Trypanosomatidae and Filarioidea are widespread in birds and have been studied extensively. Microscopical examination (ME) of stained blood films remains the gold standard method for the detection of these infections in birds, particularly because co-infections predominate in wildlife. None of the available molecular tools can detect all co-infections at the same time, but ME provides opportunities for this to be achieved. However, fixation, drying and staining of blood films as well as their ME are relatively time-consuming. This limits the detection of infected hosts during fieldwork when captured animals should be released soon after sampling. It is an obstacle for quick selection of donor hosts for parasite experimental, histological and other investigations in the field. This study modified, tested and described the buffy coat method (BCM) for quick diagnostics (~ 20 min/sample) of avian blood parasites.

METHODS

Blood of 345 birds belonging to 42 species was collected, and each sample was examined using ME of stained blood films and the buffy coat, which was examined after centrifugation in capillary tubes and after being transferred to objective glass slides. Parasite detection using these methods was compared using sensitivity, specificity, positive and negative predictive values and Cohen's kappa index.

RESULTS

Haemoproteus, Leucocytozoon, Plasmodium, microfilariae, Trypanosoma and Lankesterella parasites were detected. BCM had a high sensitivity (> 90%) and specificity (> 90%) for detection of Haemoproteus and microfilariae infections. It was of moderate sensitivity (57%) and high specificity (> 90%) for Lankesterella infections, but of low sensitivity (20%) and high specificity (> 90%) for Leucocytozoon infections. Trypanosoma and Plasmodium parasites were detected only by BCM and ME, respectively. According to Cohen's kappa index, the agreement between two diagnostic tools was substantial for Haemoproteus (0.80), moderate for Lankesterella (0.46) and fair for microfilariae and Leucocytozoon (0.28) infections.

CONCLUSIONS

BCM is sensitive and recommended as a quick and reliable tool to detect Haemoproteus, Trypanosoma and microfilariae parasites during fieldwork. However, it is not suitable for detection of species of Leucocytozoon and Plasmodium. BCM is a useful tool for diagnostics of blood parasite co-infections. Its application might be extended to studies of blood parasites in other vertebrates during field studies.

Expanding our knowledge on African trypanosomes of the subgenus Pycnomonas: A novel Trypanosoma suis-like in tsetse flies, livestock and wild ruminants sympatric with Trypanosoma suis in Mozambique

Among the subgenera of African tsetse-transmitted trypanosomes pathogenic to livestock, the least known is the subgenus Pycnomonas, which contains a single species, Trypanosoma suis (TSU), a pathogen of domestic pigs first reported in 1905 and recently rediscovered in Tanzania and Mozambique. Analysis by Fluorescent Fragment Length Barcoding (FFLB) revealed an infection rate of 20.3% (108 out of 530 tsetse flies) in a recent study in the Gorongosa and Niassa wildlife reserves in Mozambique, and demonstrated two groups of Pycnomonas trypanosomes: one (14.1%, 75 flies) showing an FFLB profile identical to the reference TSU from Tanzania, and the other (6.2%, 33 flies) differing slightly from reference TSU and designated Trypanosoma suis-like (TSU-L). Phylogenetic analyses tightly clustered TSU and TSU-L from Mozambique with TSU from Tanzania forming the clade Pycnomonas positioned between the subgenera Trypanozoon and Nannomonas. Our preliminarily exploration of host ranges of Pycnomonas trypanosomes revealed TSU exclusively in warthogs while TSU-L was identified, for the first time for a member of the subgenus Pycnomonas, in ruminants (antelopes, Cape buffalo, and in domestic cattle and goats). The preferential blood meal sources of tsetse flies harbouring TSU and TSU-L were wild suids, and most of these flies concomitantly harboured the porcine trypanosomes T. simiae, T. simiae Tsavo, and T. godfreyi. Therefore, our findings support the link of TSU with suids while TSU-L remains to be comprehensively investigated in these hosts. Our results greatly expand our knowledge of the diversity, hosts, vectors, and epidemiology of Pycnomonas trypanosomes. Due to shortcomings of available molecular diagnostic methods, a relevant cohort of trypanosomes transmitted by tsetse flies to ungulates, especially suids, has been neglected or most likely misidentified. The method employed in the present study enables an accurate discrimination of trypanosome species and genotypes and, hence, a re-evaluation of the "lost" subgenus Pycnomonas and of porcine trypanosomes in general, the most neglected group of African trypanosomes pathogenic to ungulates.

Genetic structure of Trypanosoma congolense "forest type" circulating in domestic animals and tsetse flies in the South-West region of Cameroon

Despite the economic impact of trypanosome infections, few investigations have been undertaken on the population genetics and transmission dynamics of animal trypanosomes. In this study, microsatellite markers were used to investigate the population genetics of Trypanosoma congolense “forest type”, with the ultimate goal of understanding its transmission dynamics between tsetse flies and domestic animals. Blood samples were collected from pigs, sheep, goats and dogs in five villages in Fontem, South-West region of Cameroon. In these villages, tsetse were captured, dissected and their mid-guts collected. DNA was extracted from blood and tsetse mid-guts and specific primers were used to identify T. congolense “forest type”. All positive samples were genetically characterized with seven microsatellite markers. Genetic analyses were performed on samples showing single infections of T. congolense “forest type”. Of the 299 blood samples, 137 (46%) were infected by T. congolense “forest type”. About 3% (54/1596) of tsetse fly mid-guts were infected by T. congolense “forest type”. Of 182 samples with T. congolense “forest type”, 52 were excluded from the genetic analysis. The genetic analysis on the 130 remaining samples revealed polymorphism within and between subpopulations of the target trypanosome. The dendrogram of genetic similarities was subdivided into two clusters and three sub-clusters, indicating one major and several minor genotypes of T. congolense “forest type” in tsetse and domestic animals. The low F_STvalues suggest low genetic differentiation and no sub-structuration within subpopulations. The same T. congolense genotypes appear to circulate in tsetse and domestic animals.

Population genetics of Trypanosoma brucei circulating in Glossina palpalis palpalis and domestic animals of the Fontem sleeping sickness focus of Cameroon

BACKGROUND

Human African Trypanosomiasis is still a public health threat in Cameroon. To assess Trypanosoma brucei strains circulating in the Fontem sleeping sickness focus, we conducted a genetic structure study using microsatellites to assess genotypes circulating in both tsetse flies and domestic animals.

METHOD

For this study, pyramidal traps were set up and 2695 tsetse flies were collected and 1535 (57%) living flies were dissected and their mid-guts collected. Furthermore, blood samples were collected from 397 domestic animals (pigs, goats, sheep and dogs). DNA was extracted from midguts and blood samples, and specific primers were used to identify trypanosomes of the subgenus Trypanozoon. All positive samples were genetically characterized with seven microsatellite markers.

RESULTS

Seventy five (4.7%) midguts of tsetse flies and 140 (35.2%) domestic animals were found infected by trypanosomes of the subgenus Trypanozoon. The genetic characterization of 215 Trypanozoon positive samples (75 from tsetse and 140 from animals) revealed a genetic diversity between Trypanosoma brucei circulating in tsetse and domestic animals. Of these positive samples, 87 (40.5%) single infections were used here to investigate the population genetics of Trypanosoma brucei circulating in tsetse and domestic animals. The dendrogram illustrating the genetic similarities between Trypanosoma brucei genotypes was subdivided into four clusters. The samples from tsetse belonged to the same cluster whereas the samples from domestic animals and espcially pigs were distributed in the four clusters.

CONCLUSION

Pigs appeared as the animal species harboring the highest number of different Trypanosoma brucei strains. They may play an important role in the propagation of different genotypes. The FST values revealed a sub structuration of Trypanosoma brucei according to hosts and sometimes villages. The data obtained from this study may have considerable importance for the understanding of the transmission and the spread of specific genotypes of Trypanosoma brucei.

A call to arms: on refining Plasmodium vivax microsatellite marker panels for comparing global diversity

BACKGROUND

Microsatellite (MS) markers have become an important tool for studying the population diversity, evolutionary history and multiplicity of infection (MOI) of malaria parasite infections. MS are typically selected on the basis of being highly polymorphic. However, it is known that the polymorphic potential (mutability) of each marker can vary as much as two orders of magnitude, which radically changes how diversity is represented in the genome from one marker to the next. Over the past decade, approximately 240 Plasmodium vivax MS have been published, comprising nine major panels of markers. Inconsistent usage of each panel has resulted in a surfeit of descriptive genetic diversity data that are largely incomparable between populations. The objective of this study was to statistically evaluate the quality of individual MS markers in order to validate a refined panel of markers that will provide a balanced picture of P. vivax population diversity.

METHODS

All previously published data, including genetic diversity indices, MS parameters, and population parameters, were assembled from 18 different global studies into a flat file to facilitate statistical analysis and modelling using JMP® Genomics 6.0 (SAS Institute Inc, Cary, NC, USA). Statistical modeling was employed to down-select markers with extreme variation among the mean number of alleles, expected heterozygosity, maximum repeat length and/or chromosomal location of the repeat. Individual MS were analysed by step-down whole model linear regression and standard least squares fit models, both stratified by annual parasite incidence to identify MS markers with values significantly different from the mean.

RESULTS

Of the 42 MS under evaluation in this study, 18 (nine high priority) were identified as ideal candidates for measuring population diversity between global regions, while five (two high priority) additional markers were identified as candidates for MOI studies.

CONCLUSIONS

MS diversity was found to be a function of endemicity and motif structure. Evaluation of individual MS permitted the assembly of a refined panel of markers that can be reliably utilized in the field to compare population structures between global regions.

Domestic pigs as potential reservoirs of human and animal trypanosomiasis in Northern Tanzania

BACKGROUND

Pig keeping is becoming increasingly common across sub-Saharan Africa. Domestic pigs from the Arusha region of northern Tanzania were screened for trypanosomes using PCR-based methods to examine the role of pigs as a reservoir of human and animal trypanosomiasis.

METHODS

A total of 168 blood samples were obtained from domestic pigs opportunistically sampled across four districts in Tanzania (Babati, Mbulu, Arumeru and Dodoma) during December 2004. A suite of PCR-based methods was used to identify the species and sub-species of trypanosomes including: Internally Transcribed Sequence to identify multiple species; species specific PCR to identify T. brucei s. l. and T. godfreyi and a multiplex PCR reaction to distinguish T. b. rhodesiense from T. brucei s. l.

RESULTS

Of the 168 domestic pigs screened for animal and human infective trypanosome DNA, 28 (16.7%) were infected with one or more species of trypanosome; these included: six pigs infected with Trypanosoma vivax (3.6%); three with Trypanosoma simiae (1.8%); two with Trypanosoma congolense (Forest) (1%) and four with Trypanosoma godfreyi (2.4%). Nineteen pigs were infected with Trypanosoma brucei s. l. (10.1%) of which eight were identified as carrying the human infective sub-species Trypanosoma brucei rhodesiense (4.8%).

CONCLUSION

These results show that in Tanzania domestic pigs may act as a significant reservoir for animal trypanosomiasis including the cattle pathogens T. vivax and T. congolense, the pig pathogen T. simiae, and provide a significant reservoir for T. b. rhodesiense, the causative agent of acute Rhodesian sleeping sickness.

Identification and genetic characterization of Trypanosoma congolense in domestic animals of Fontem in the South-West region of Cameroon

To understand the circulation and the spread of Trypanosoma congolense genotypes in animals of Fontem in the southwest region of Cameroon, T. congolense forest and T. congolense savannah were investigated in 397 domestic animals in eight villages. Out of the 397 domestic animals, 86 (21.7%) were found infected by trypanosomes, using the capillary tube centrifugation test. The PCR with specific primers identified 163 (41.1%) and 81 (20.4%) animals infected by T. congolense forest and T. congolense savannah, respectively; showing for the first time the circulation of T. congolense savannah in the Fontem region. No infection with T. congolense savannah was found in pigs whereas goats and sheep were infected by T. congolense forest and/or T. congolense savannah. The prevalence of trypanosomes varied significantly amongst villages and animal species. The genotyping of T. congolense forest positive samples using microsatellites markers showed that multiple genotypes occurred in 27.2% (44/163) of animals sampled, whereas single genotypes were found in 73.8% (119/163) of samples. Some alleles were found in all animal species as well as in all villages and were responsible for major genotypes, whereas others (rare alleles) were identified only in some animals of few villages. These rare alleles were characteristic of specific genotypes, assimilated to minor genotypes which can be spread in the region through tsetse flies. The microsatellite markers show a low genetic variability and an absence of sub-structuration within T. congolense forest. The analysis of the microsatellite data revealed a predominant clonal reproduction within T. congolense forest. Pigs were the animal species with the highest number of different genotypes of T. congolense forest. They seem to play an important epidemiological role in the propagation and spread of different genotypes of T. congolense.