Trypanosoma evansi and T. equiperdum: distribution, biology, treatment and phylogenetic relationship (a review)

Drug resistance in animal trypanosomiases: Epidemiology, mechanisms and control strategies

Animal trypanosomiasis (AT) is a complex of veterinary diseases known under various names such as nagana, surra, dourine and mal de caderas, depending on the country, the infecting trypanosome species and the host. AT is caused by parasites of the genus Trypanosoma, and the main species infecting domesticated animals are T. brucei brucei, T. b. rhodesiense, T. congolense, T. simiae, T. vivax, T. evansi and T. equiperdum. AT transmission, again depending on species, is through tsetse flies or common Stomoxys and tabanid flies or through copulation. Therefore, the geographical spread of all forms of AT together is not restricted to the habitat of a single vector like the tsetse fly and currently includes almost all of Africa, and most of South America and Asia. The disease is a threat to millions of companion and farm animals in these regions, creating a financial burden in the billions of dollars to developing economies as well as serious impacts on livestock rearing and food production. Despite the scale of these impacts, control of AT is neglected and under-resourced, with diagnosis and treatments being woefully inadequate and not improving for decades. As a result, neither the incidence of the disease, nor the effectiveness of treatment is documented in most endemic countries, although it is clear that there are serious issues of resistance to the few old drugs that are available. In this review we particularly look at the drugs, their application to the various forms of AT, and their mechanisms of action and resistance. We also discuss the spread of veterinary trypanocide resistance and its drivers, and highlight current and future strategies to combat it.

Gallium maltolate, a promising low toxicity drug with curative effect on mice chronically infected with Trypanosoma evansi

Trypanosoma evansi is a flagellate protozoan that infects a wide range of hosts, especially horses. Clinically, the infection is characterized by rapid weight loss, anemia and mobility disorders. This study evaluated the efficacy of treatment gallium maltolate (GaM) in rats infected with T. evansi in the acute and chronic phases of the disease and its influence on the enzyme and blood parameters. 48 animals (Rattus norvegicus) were divided into 8 groups (A-H) of 6 animals each, namely: A: (negative control) uninfected; B: acutely infected positive control; C: chronically infected positive control; D: acutely infected, treated with GaM for 7 days post infection (p.i.); E: acutely infected treated with GaM for 3 days before infection (b.i) and 7 days p.i.; F: chronically infected, treated with GaM for 7 days p.i.; G: chronically infected, treated with GaM for 3 days b.i. and 7 days p.i.; and H: uninfected treated with GaM for 10 days. Acute infected animals (B, D and E) had a progressive increase in parasitemia and were died or euthanized before completing treatment days (5th days p.i.) as they had high parasitemia (over 100 field trypanosomes in the blood smear). Thus, it can be concluded that GaM was not effective against an acute infection. In untreated chronically infected animals (C) the parasitemia also increased progressively and they were euthanized on the 7th day p.i.. The chronically infected and treated animals (F and G) showed low parasitemia and after treatment became negative, showing no trypanosomes in the bloodstream until the 50th day of the experiment. Thus, we conclude that GaM was effective against chronic infections. In uninfected and treated animals (H) hematological, biochemical and enzymatic parameters had no significant changes when compared to the negative control group (A) demonstrating the low toxicity of GaM.

Recent Progress in the Detection of Surra, a Neglected Disease Caused by Trypanosoma evansi with a One Health Impact in Large Parts of the Tropic and Sub-Tropic World

Surra is a wasting disease triggered by infection with Trypanosoma evansi, a protozoan blood parasite that causes mortality and morbidity in a broad spectrum of wild and domestic animals and occasionally humans. Trypanosoma evansi has the widest geographical spread among all pathogenic trypanosomes, inflicting significant worldwide economic problems due to its adverse effects on meat and milk production. For diagnosis, most endemic countries continue to rely on traditional parasitological and serological techniques, such as the analysis of blood smears by microscopy and the Card Agglutination Test for T. evansi (CATT/T. evansi). Although these techniques suffer from a limited positive predictive value (PPV), resource constraints in endemic countries often hinder the adoption of more advanced diagnostic tools such as PCR. This paper addresses diverse diagnostic approaches for identifying T. evansi and assesses their viability in field settings. Moreover, it underscores the urgency of transitioning towards molecular diagnostic techniques such as Loop-Mediated Isothermal Amplification (LAMP) and Recombinase Polymerase Amplification (RPA) for dependable high-PPV point-of-care (POC) diagnostics. Finally, this review delves into strategies to enhance and refine next-generation diagnostics for Surra as part of a One Health approach.

Parasitological and molecular detection of Trypanosoma evansi in a dog from Tocache, San Martin, Peru

This study presents the first case report of canine trypanosomiasis caused by Trypanosoma evansi in Peru. The case was admitted to a veterinary clinic in the Peruvian Amazon region of San Martin with severe clinical symptomatology which resulted in the dog's death. Microscopy screening showed the presence of trypomastigotes in blood and bone marrow and postmortem histopathology found damage at the cardiac, lung, kidney and spleen levels. Collected specimens were tested by nested-PCR which were positive for Trypanosoma spp., but negative for T. cruzi. High-throughput sequencing determined that the infecting species was closely related to T. equiperdom/evansi and subsequent phylogenetic analysis confirmed that the sample was related to T. evansi. The presence of T. evansi in the area highlights the need for increased surveillance to assess the impact of surra in the region and to develop measures to prevent socioeconomic damage resulting from infections in domestic and farm animals as well as prevent zoonotic transmission.

Morphological, serological, molecular detection, and phylogenetic analysis of Trypanosoma evansi in horses of different regions in Iran

Trypanosoma evansi, the causative agent of "surra" is enzootic in Iran. The current study aimed to detect T. evansi in horses from different regions of Iran using morphological, serological, and molecular methods. In 2021, 400 blood samples were collected from horses in eight regions. Eighty horses showed clinical signs such as cachexia (n = 64), fever (n = 36), foot edema (n = 40), and abdominal edema (n = 32), and 320 horses appeared healthy. All samples from the studied regions were evaluated for the presence of trypanosomes using direct analysis of blood smears, mercuric chloride, and PCR-based tests. In total, 12% (95% CI: ± 3.1%), 21% (95% CI: ± 3.9%), and 21% (84) of animals were positive for Trypanosoma in microscopic, serologic, and molecular analyses, respectively. All animals positive for SSU rDNA PCR were from Qom, Semnan, and Golestan regions. Further molecular analyses on 84 PCR-positive horses revealed that 29 horses scored positive in PCR using primers of trypanozoon species and 5 scored positive in PCR using primers of Trypanosoma evansi type A. All samples (n = 5) were from Qom region. The 205-bp fragments of T. evansi RoTat 1.2VSG (accession numbers: ON017789-93) analyzed and compared to other isolates sequence from GenBank BLAST search. It has close similarities with isolates from Pakistan, Egypt, Malaysia, Kenya, and India. Data herein demonstrated that horses from Iran were at high risk of T. evansi infection. Comprehensive control programs, such as those based on the application of repellants and traps, and also, compliance with quarantine standards are recommended for minimizing the risk of the infection.

Variation of sensitivity of Trypanosoma evansi isolates from Isiolo and Marsabit counties of Kenya to locally available trypanocidal drugs

Trypanocidal resistance is a major cause of treatment failure. This study evaluated the sensitivity of Trypanosoma evansi field isolates collected from Marsabit and Isiolo counties, Kenya. A total of 2,750 camels were screened using parasitological tests for trypanosomes. Of the screened camels, 113 tested positive from which 40 T. evansi isolates were tested using the single dose mice sensitivity test. Five treatment groups each comprising of 6 mice were inoculated intraperitoneally with 1x105 trypanosomes of each isolate and treated 24 hours later with isometamidium chloride at 1 mg/kg, homidium chloride at 1mg/kg, diminazene aceturate at 20 mg/kg and quinapyramine sulphate & chloride at 1 mg/kg. The fifth group was left untreated (positive control). The mice were monitored daily for 60 days. A survey on camel owners' practices that influence development of resistance to trypanocidal drugs was then conducted. Results indicated presence of drug resistance in all the 7 study sites that had infected camels. Seven of the isolates tested were resistant to diminazene aceturate whereas, 28, 33 and 34 were resistant to isometamidium chloride, quinapyramine sulphate & chloride and homidium chloride, respectively. Seven (17.5%) isolates of the 40 tested were sensitive to all 4 drugs, whereas, 7.5%, 10%,55% and 10% were resistant to 1,2,3 and 4 drugs, respectively. The prevalence of multiple drug resistance was 75%. Survey data indicated that camel management practices influenced the prevalence and degree of drug resistance. In conclusion, the multiple drug resistance observed in the two counties may not be an indication of total trypanocidal drug failure. Judicious treatment of confirmed trypanosomiasis cases with correct dosage would still be effective in controlling the disease since the observed resistance was at the population and not clonal level. However, integrated control of the disease and the vectors using available alternative methods is recommended to reduce drug use.

PAG3 promotes the differentiation of bloodstream forms in Trypanosoma brucei and reveals the evolutionary relationship among the Trypanozoon trypanosomes

Introduction

Trypanosoma brucei, T. evansi and T. equiperdum are members of the subgenus Trypanozoon and are highly similar morphologically and genetically. The main differences between these three species are their differentiation patterns in the hosts and the role of vectors in their life cycles. However, the mechanisms causing these differences are still controversial.

Methods

PAG3 gene was accessed by PCR amplification in 26 strains of Trypanozoon and sequences were then analyzed by BLAST accompanied with T. evansitype B group. RNA interference and CRISPR/Cas9 were used for revealing possible role of PAG3 in slender to stumpy transformation.

Results

The procyclin associated gene 3 (PAG3) can be found in the pleomorphicspecies, T.brucei, which undergoes differentiation of slender forms to the stumpy form. This differentiation process is crucial for transmission to the tsetse fly vector. However, a homologue of PAG3 was not detected in either T. evansi or in the majority of T. equiperdum strains which are allmonomorphic. Furthere xperiments in T. brucei demonstrated that, when PAG3 was down-regulated or absent, there was a significant reduction in the differentiation from slender to stumpy forms.

Conclusion

Therefore, we conclude that PAG3 is a key nuclear gene involved in the slender to stumpy differentiation pathway of T.brucei in the mammalian host. Loss of this gene might also offer a simple evolutionary mechanism explaining why T. evansi and some T. equiperdum have lost the ability to differentiate and have been driven to adapt to transmission cycles that by pass the tsetse vector or mechanical contact.

Risk factors for equine trypanosomosis and hematological analysis of horses in Paraguay

Animal trypanosomosis, caused by Trypanozoon trypanosomes (Trypanosoma evansi and T. equiperdum), and Trypanosoma vivax, is endemic to South American countries and has a negative impact on the livestock industry. However, the risk factors for trypanosomosis in Paraguay remain unknown. This study aimed to determine the risk factors for equine trypanosomosis in Paraguay based on a PCR-based molecular survey and individual horse sampling data. In this study, 739 blood samples were collected from horses in 16 departments of Paraguay between August 2019 and November 2020. To elucidate the risk factors for trypanosome infection, the relationship between trypanosome infection status detected by PCR and the location, sex, age, breed of horses, and season of sample collection was analyzed. There were no significant differences in trypanosome prevalence in horses between the eastern and western regions, ages, or breeds of horses in Paraguay. Sex and season were identified as risk factors for trypanosome infection in horses in Paraguay in the current study. These results suggest that the rainy-summer season, when vectors increase in number and their blood-sucking activity, could be the most important risk factor for trypanosome infection in Paraguay horses. Preventive measures and treatments should be developed to address these factors.

Oxidative Phosphorylation Is Required for Powering Motility and Development of the Sleeping Sickness Parasite Trypanosoma brucei in the Tsetse Fly Vector

The single-celled parasite Trypanosoma brucei is transmitted by hematophagous tsetse flies. Life cycle progression from mammalian bloodstream form to tsetse midgut form and, subsequently, infective salivary gland form depends on complex developmental steps and migration within different fly tissues. As the parasite colonizes the glucose-poor insect midgut, ATP production is thought to depend on activation of mitochondrial amino acid catabolism via oxidative phosphorylation (OXPHOS). This process involves respiratory chain complexes and F₁F_o-ATP synthase and requires protein subunits of these complexes that are encoded in the parasite's mitochondrial DNA (kDNA). Here, we show that progressive loss of kDNA-encoded functions correlates with a decreasing ability to initiate and complete development in the tsetse. First, parasites with a mutated F₁F_o-ATP synthase with reduced capacity for OXPHOS can initiate differentiation from bloodstream to insect form, but they are unable to proliferate in vitro. Unexpectedly, these cells can still colonize the tsetse midgut. However, these parasites exhibit a motility defect and are severely impaired in colonizing or migrating to subsequent tsetse tissues. Second, parasites with a fully disrupted F₁F_o-ATP synthase complex that is completely unable to produce ATP by OXPHOS can still differentiate to the first insect stage in vitro but die within a few days and cannot establish a midgut infection in vivo. Third, parasites lacking kDNA entirely can initiate differentiation but die soon after. Together, these scenarios suggest that efficient ATP production via OXPHOS is not essential for initial colonization of the tsetse vector but is required to power trypanosome migration within the fly. IMPORTANCE African trypanosomes cause disease in humans and their livestock and are transmitted by tsetse flies. The insect ingests these parasites with its blood meal, but to be transmitted to another mammal, the trypanosome must undergo complex development within the tsetse fly and migrate from the insect's gut to its salivary glands. Crucially, the parasite must switch from a sugar-based diet while in the mammal to a diet based primarily on amino acids when it develops in the insect. Here, we show that efficient energy production by an organelle called the mitochondrion is critical for the trypanosome's ability to swim and to migrate through the tsetse fly. Surprisingly, trypanosomes with impaired mitochondrial energy production are only mildly compromised in their ability to colonize the tsetse fly midgut. Our study adds a new perspective to the emerging view that infection of tsetse flies by trypanosomes is more complex than previously thought.

The Occurrence of Malignancy in Trypanosoma brucei brucei by Rapid Passage in Mice

Pleomorphic Trypanosoma brucei are best known for their tightly controlled cell growth and developmental program, which ensures their transmissibility and host fitness between the mammalian host and insect vector. However, after long-term adaptation in the laboratory or by natural evolution, monomorphic parasites can be derived. The origin of these monomorphic forms is currently unclear. Here, we produced a series of monomorphic trypanosome stocks by artificially syringe-passage in mice, creating snapshots of the transition from pleomorphism to monomorphism. We then compared these artificial monomorphic trypanosomes, alongside several naturally monomorphic T. evansi and T. equiperdum strains, with the pleomorphic T. brucei. In addition to failing to generate stumpy forms in animal bloodstream, we found that monomorphic trypanosomes from laboratory and nature exhibited distinct differentiation patterns, which are reflected by their distinct differentiation potential and transcriptional changes. Lab-adapted monomorphic trypanosomes could still be induced to differentiate, and showed only minor transcriptional differences to that of the pleomorphic slender forms but some accumulated differences were observed as the passages progress. All naturally monomorphic strains completely fail to differentiate, corresponding to their impaired differentiation regulation. We propose that the natural phenomenon of trypanosomal monomorphism is actually a malignant manifestation of protozoal cells. From a disease epidemiological and evolutionary perspective, our results provide evidence for a new way of thinking about the origin of these naturally monomorphic strains, the malignant evolution of trypanosomes may raise some concerns. Additionally, these monomorphic trypanosomes may reflect the quantitative and qualitative changes in the malignant evolution of T. brucei, suggesting that single-celled protozoa may also provide the most primitive model of cellular malignancy, which could be a primitive and inherent biological phenomenon of eukaryotic organisms from protozoans to mammals.

Development of a microsphere-based immunoassay for the serological diagnosis of equine trypanosomosis

Trypanozoon infections in equids are caused by three parasite species in the Trypanozoon subgenus: Trypanosoma equiperdum, T. brucei and T. evansi. They are respectively responsible for infectious diseases dourine, nagana and surra. Due to the threat that Trypanozoon infection represents for international horse trading, accurate diagnostic tests are crucial. Current tests suffer from poor sensitivity and specificity, due in the first case to the transient presence of parasites in the blood and in the second, to antigenic cross-reactivity among Trypanozoon subspecies. This study was designed to develop a microsphere‐based immunoassay for diagnosing equine trypanosomosis. We tested beads coated with eight Trypanosoma spp. recombinant antigens: enolase, GM6, PFR1, PFR2, ISG65, VSGat, RoTat1.2 and JN2118HU. Of these, GM6 was identified as the best candidate for the serological diagnosis of Trypanozoon infections in equids. Using a receiver operating characteristic (ROC) analysis on 349 equine sera, anti-GM6 antibodies were detected with an AUC value of 0.994 offering a sensitivity of 97.9% and a specificity of 96.0%. Our findings show that the GM6 antigen is a good target for diagnosing equine trypanosomosis using a microsphere‐based immunoassay. This promising assay could be a useful alternative to the official diagnostic tool for equine trypanosomosis.

First report of surra (Trypanosoma evansi infection) in Iranian sheep

Clinical trypanosomiasis in sheep is described for the first time in Iran after history taking, complete physical examination and blood samples collected for laboratory investigations. The client emphasised on animal weight loss dating back to one week ago. The clinical examination revealed enlargements of the pre-scapular and pre-femoral lymph nodes and pale mucous membranes. Laboratory investigation showed that the sheep had anaemia with hyperproteinaemia. Thin blood smear examination revealed the presence of Trypanosoma. Treatment included diminazene aceturate (3.5 mg/kg, IM) for three consecutive days, flunixin meglumine (1.1 mg/kg, IM), and oxytetracycline (10 mg/kg, IM). The examination of the blood film after treatment showed no parasite. Trypanosomiasis may occur in our climatic condition in sheep. In two cases studied here, two consecutive doses of diminazene aceturate administration led to clinical cure. The control of trypanosomiasis in farms may be possible through methods for the control of vectors, such as prophylactic treatment and observing of hygiene in husbandry systems for animals at risk

First molecular survey of animal trypanosomes in Paraguayan horses

Despite the epidemic situation of animal trypanosomosis caused by Trypanosoma evansi, Trypanosoma equiperdum and Trypanosoma vivax in South American countries, there are no reports for the prevalence of animal trypanosomes in Paraguay. In this study, 408 blood samples were obtained from apparently healthy horses from sixteen departments of Paraguay, for routine medical check-up from August to September 2019, and a polymerase chain reaction (PCR)-based cross-sectional study was carried out to identify trypanosome prevalence. The prevalence of Trypanozoon (T. evansi and T. equiperdum) and T. vivax was 7.11% (29/408) and 26.23% (107/408), respectively. Mixed infections were detected in 4.90% (20/408) of the samples. Some of the selected trypanosome positive samples were confirmed as T. vivax and T. evansi Type A by sequence analysis of the internal transcribe spacer region and RoTat1.2 variant surface glycoprotein gene, respectively. In conclusion, we found higher prevalence of T. vivax than Trypanozoon in Paraguayan horses. However, the genotypic variation should be verified in further studies.

Redesigned and reversed: architectural and functional oddities of the trypanosomal ATP synthase

Mitochondrial F-type adenosine triphosphate (ATP) synthases are commonly introduced as highly conserved membrane-embedded rotary machines generating the majority of cellular ATP. This simplified view neglects recently revealed striking compositional diversity of the enzyme and the fact that in specific life stages of some parasites, the physiological role of the enzyme is to maintain the mitochondrial membrane potential at the expense of ATP rather than to produce ATP. In addition, mitochondrial ATP synthases contribute indirectly to the organelle's other functions because they belong to major determinants of submitochondrial morphology. Here, we review current knowledge about the trypanosomal ATP synthase composition and architecture in the context of recent advances in the structural characterization of counterpart enzymes from several eukaryotic supergroups. We also discuss the physiological function of mitochondrial ATP synthases in three trypanosomatid parasites, Trypanosoma cruzi, Trypanosoma brucei and Leishmania, with a focus on their disease-causing life cycle stages. We highlight the reversed proton-pumping role of the ATP synthase in the T. brucei bloodstream form, the enzyme's potential link to the regulation of parasite's glycolysis and its role in generating mitochondrial membrane potential in the absence of mitochondrial DNA.

Monomorphic Trypanozoon: towards reconciling phylogeny and pathologies

Trypanosoma brucei evansi and T. brucei equiperdum are animal infective trypanosomes conventionally classified by their clinical disease presentation, mode of transmission, host range, kinetoplast DNA (kDNA) composition and geographical distribution. Unlike other members of the subgenus Trypanozoon, they are non-tsetse transmitted and predominantly morphologically uniform (monomorphic) in their mammalian host. Their classification as independent species or subspecies has been long debated and genomic studies have found that isolates within T. brucei evansi and T. brucei equiperdum have polyphyletic origins. Since current taxonomy does not fully acknowledge these polyphyletic relationships, we re-analysed publicly available genomic data to carefully define each clade of monomorphic trypanosome. This allowed us to identify, and account for, lineage-specific variation. We included a recently published isolate, IVM-t1, which was originally isolated from the genital mucosa of a horse with dourine and typed as T. equiperdum. Our analyses corroborate previous studies in identifying at least four distinct monomorphic T. brucei clades. We also found clear lineage-specific variation in the selection efficacy and heterozygosity of the monomorphic lineages, supporting their distinct evolutionary histories. The inferred evolutionary position of IVM-t1 suggests its reassignment to the T. brucei evansi type B clade, challenging the relationship between the Trypanozoon species, the infected host, mode of transmission and the associated pathological phenotype. The analysis of IVM-t1 also provides, to our knowledge, the first evidence of the expansion of T. brucei evansi type B, or a fifth monomorphic lineage represented by IVM-t1, outside of Africa, with important possible implications for disease diagnosis.

Evolution of the variant surface glycoprotein family in African trypanosomes

An intriguing and remarkable feature of African trypanosomes is their antigenic variation system, mediated by the variant surface glycoprotein (VSG) family and fundamental to both immune evasion and disease epidemiology within host populations. Recent studies have revealed that the VSG repertoire has a complex evolutionary history. Sequence diversity, genomic organization, and expression patterns are species-specific, which may explain other variations in parasite virulence and disease pathology. Evidence also shows that we may be underestimating the extent to what VSGs are repurposed beyond their roles as variant antigens, establishing a need to examine VSG functionality more deeply. Here, we review sequence variation within the VSG gene family, and highlight the many opportunities to explore their likely diverse contributions to parasite survival.

Trypanosome Signaling-Quorum Sensing

African trypanosomes are responsible for important diseases of humans and animals in sub-Saharan Africa. The best-studied species is Trypanosoma brucei, which is characterized by development in the mammalian host between morphologically slender and stumpy forms. The latter are adapted for transmission by the parasite's vector, the tsetse fly. The development of stumpy forms is driven by density-dependent quorum-sensing (QS), the molecular basis for which is now coming to light. In this review, I discuss the historical context and biological features of trypanosome QS and how it contributes to the parasite's infection dynamics within its mammalian host. Also, I discuss how QS can be lost in different trypanosome species, such as T. brucei evansi and T. brucei equiperdum, or modulated when parasites find themselves competing with others of different genotypes or of different trypanosome species in the same host. Finally, I consider the potential to exploit trypanosome QS therapeutically. Expected final online publication date for the Annual Review of Microbiology, Volume 75 is October 2021. Please see http://www.annualreviews.org/page/journal/pubdates for revised estimates.

Epidemiology of Trypanosomiasis in Wildlife-Implications for Humans at the Wildlife Interface in Africa

While both human and animal trypanosomiasis continue to present as major human and animal public health constraints globally, detailed analyses of trypanosome wildlife reservoir hosts remain sparse. African animal trypanosomiasis (AAT) affects both livestock and wildlife carrying a significant risk of spillover and cross-transmission of species and strains between populations. Increased human activity together with pressure on land resources is increasing wildlife–livestock–human infections. Increasing proximity between human settlements and grazing lands to wildlife reserves and game parks only serves to exacerbate zoonotic risk. Communities living and maintaining livestock on the fringes of wildlife-rich ecosystems require to have in place methods of vector control for prevention of AAT transmission and for the treatment of their livestock. Major Trypanosoma spp. include Trypanosoma brucei rhodesiense, Trypanosoma brucei gambiense, and Trypanosoma cruzi, pathogenic for humans, and Trypanosoma vivax, Trypanosoma congolense, Trypanosoma evansi, Trypanosoma brucei brucei, Trypanosoma dionisii, Trypanosoma thomasbancrofti, Trypanosma elephantis, Trypanosoma vegrandis, Trypanosoma copemani, Trypanosoma irwini, Trypanosoma copemani, Trypanosoma gilletti, Trypanosoma theileri, Trypanosoma godfreyi, Trypansoma simiae, and Trypanosoma (Megatrypanum) pestanai. Wildlife hosts for the trypansomatidae include subfamilies of Bovinae, Suidae, Pantherinae, Equidae, Alcephinae, Cercopithecinae, Crocodilinae, Pteropodidae, Peramelidae, Sigmodontidae, and Meliphagidae. Wildlife species are generally considered tolerant to trypanosome infection following centuries of coexistence of vectors and wildlife hosts. Tolerance is influenced by age, sex, species, and physiological condition and parasite challenge. Cyclic transmission through Glossina species occurs for T. congolense, T. simiae, T. vivax, T. brucei, and T. b. rhodesiense, T. b. gambiense, and within Reduviid bugs for T. cruzi. T. evansi is mechanically transmitted, and T. vixax is also commonly transmitted by biting flies including tsetse. Wildlife animal species serve as long-term reservoirs of infection, but the delicate acquired balance between trypanotolerance and trypanosome challenge can be disrupted by an increase in challenge and/or the introduction of new more virulent species into the ecosystem. There is a need to protect wildlife, animal, and human populations from the infectious consequences of encroachment to preserve and protect these populations. In this review, we explore the ecology and epidemiology of Trypanosoma spp. in wildlife.

Two New Antiprotozoal Diterpenes From the Roots of Acacia nilotica

The powdered roots of the medicinal plant Acacia nilotica were extracted with hexane and ethyl acetate, and the extracts were subjected to column chromatography for the isolation of potentially bioactive compounds and their screening against kinetoplastid pathogens. NMR and HREI mass spectrometric analyses identified two new diterpenes, characterized as 16, 19-dihydroxycassa-12-en-15-one (Sandynone, 1) and (5S, 7R, 8R, 9R, 10S, 13Z, 17S)-7,8:7,17:16,17-triepoxy-7,8-seco-cassa-13-ene (niloticane B, 2). The previously reported (5S,7R,8R,9R,10S) -(-)-7,8-seco-7, 8-oxacassa-13,15-diene-7,17-diol (3), (5S,7R,8R,9R,10S) -(-)-7,8-seco-7, 8-oxacassa-13,15-dien-7-ol-17-al (4), and (5S,7R,8R,9R,10S) -(-)-7,8-seco-7, 8-oxacassa-13,15-dien-7-ol (5) a, mixture of stigmasterol (6a) and sitosterol (6b), and lupeol (7) were also isolated. Several column fractions displayed significant activity against a panel of Trypanosoma and Leishmania spp., and from the most active fraction, compound 4 was isolated with high purity. The compound displayed high activity, particularly against T. brucei, T. evansi, and L. mexicana (0.88-11.7 µM) but only a modest effect against human embryonic kidney cells and no cross-resistance with the commonly used melaminophenyl arsenical and diamidine classes of trypanocides. The effect of compound 4 against L. mexicana promastigotes was irreversible after a 5-h exposure, leading to the sterilization of the culture between 24 and 48 h.

Euglenozoa: taxonomy, diversity and ecology, symbioses and viruses

Euglenozoa is a species-rich group of protists, which have extremely diverse lifestyles and a range of features that distinguish them from other eukaryotes. They are composed of free-living and parasitic kinetoplastids, mostly free-living diplonemids, heterotrophic and photosynthetic euglenids, as well as deep-sea symbiontids. Although they form a well-supported monophyletic group, these morphologically rather distinct groups are almost never treated together in a comparative manner, as attempted here. We present an updated taxonomy, complemented by photos of representative species, with notes on diversity, distribution and biology of euglenozoans. For kinetoplastids, we propose a significantly modified taxonomy that reflects the latest findings. Finally, we summarize what is known about viruses infecting euglenozoans, as well as their relationships with ecto- and endosymbiotic bacteria.

Bioenergetic consequences of FoF1-ATP synthase/ATPase deficiency in two life cycle stages of Trypanosoma brucei

Mitochondrial ATP synthase is a reversible nanomotor synthesizing or hydrolyzing ATP depending on the potential across the membrane in which it is embedded. In the unicellular parasite Trypanosoma brucei, the direction of the complex depends on the life cycle stage of this digenetic parasite: in the midgut of the tsetse fly vector (procyclic form), the F_oF₁–ATP synthase generates ATP by oxidative phosphorylation, whereas in the mammalian bloodstream form, this complex hydrolyzes ATP and maintains mitochondrial membrane potential (ΔΨm). The trypanosome F_oF₁–ATP synthase contains numerous lineage-specific subunits whose roles remain unknown. Here, we seek to elucidate the function of the lineage-specific protein Tb1, the largest membrane-bound subunit. In procyclic form cells, Tb1 silencing resulted in a decrease of F_oF₁–ATP synthase monomers and dimers, rerouting of mitochondrial electron transfer to the alternative oxidase, reduced growth rate and cellular ATP levels, and elevated ΔΨm and total cellular reactive oxygen species levels. In bloodstream form parasites, RNAi silencing of Tb1 by ∼90% resulted in decreased F_oF₁–ATPase monomers and dimers, but it had no apparent effect on growth. The same findings were obtained by silencing of the oligomycin sensitivity-conferring protein, a conserved subunit in T. brucei F_oF₁–ATP synthase. However, as expected, nearly complete Tb1 or oligomycin sensitivity-conferring protein suppression was lethal because of the inability to sustain ΔΨm. The diminishment of F_oF₁–ATPase complexes was further accompanied by a decreased ADP/ATP ratio and reduced oxygen consumption via the alternative oxidase. Our data illuminate the often diametrically opposed bioenergetic consequences of F_oF₁–ATP synthase loss in insect versus mammalian forms of the parasite.

Molecular Characterization of Hemoparasites and Hemoplasmas Infecting Domestic Cats of Southern India

In the present study, 111 blood samples were collected from apparently healthy cats belonging to four districts of Kerala, southern India, and they were investigated for the presence of hemoparasites and hemoplasmas by light microscopic examination and polymerase chain reaction (PCR). The microscopic examination of the Giemsa-stained blood smears did not reveal any parasites/organisms. However, PCR followed by nucleotide sequencing could detect 10 (9.01%) out of 111 samples infected with Hepatozoon felis, 3 (2.70%) with Cytauxzoon spp., and 10 (9.01%) with Mycoplasma spp. None of the samples revealed amplicons specific for the Babesia spp. and Trypanosoma evansi. The phylogenetic analysis of 18S ribosomal RNA (rRNA) gene sequences of H. felis revealed the existence of two different populations of H. felis circulating in the blood of infected cats. The phylogenetic tree was constructed based on 18S rRNA gene sequences of Cytauxzoon spp. and revealed that these isolates formed a distinct clade and do not cluster with any of the isolates from other countries. Among the 10 samples positive for Mycoplasma spp. infections, 7 were detected positive for Candidatus Mycoplasma haemominutum, two for Mycoplasma haemofelis, and one for Candidatus Mycoplasma turicensis. Phylogenetic analysis of 16S rRNA gene sequences of Mycoplasma spp. showed no distinct geographical grouping of the sequences. The sequences of M. haemofelis, Candidatus M. haemominutum, and Candidatus M. turicensis identified in the study clustered along with their respective isolates from around the world. To the best of our knowledge, this study forms the first report of molecular detection of Cytauxzoon spp. and Candidatus M. turicensis in cats from India.

Assessment of Trypanosoma evansi prevalence and associated risk factors by immune trypanolysis test in camels from Ghardaïa district, southern Algeria

Trypanosoma evansi (T. evansi) is a flagellated parasite with worldwide distribution, mainly affecting camels, horses, dogs, buffaloes and wild animals. Trypanosomosis caused by T. evansi, known as surra, is a vector borne disease that affects the health and productivity of camels. The aim of our study was to assess the prevalence of trypanosomosis due to T. evansi in camels by the immune trypanolosis test and to identify associated risk factors. Our cross-sectional study was performed on 161 camels from Ghardaïa district, southern Algeria. A structured questionnaire was used to collect data on individual characteristics (age, gender and breed) husbandry management (herd size and activity of animals) and health conditions (history of abortion and clinical symptoms). The immune trypanolysis test revealed an overall seroprevalence of 9.3% (CI 95%, 5.9-14.9). Possible factors associated with T. evansi infection were analysed by univariate and multivariate logistic regression. The results showed that risk factors for camels were history of symptoms (P = 0.002, OR = 21.91, CI95% = 3.48-169.80), racing activities (P = 0.003, OR = 0.01, CI95% = 0.001-0.18) and small herd size (P = 0.013, OR = 8.22, CI95% = 1.64-49.75). In conclusion, this study showed that T. evansi is endemic in camels of Ghardaïa district. To reduce dissemination of the disease to non-endemic areas, it is recommended to minimise risk factors associated with the infection.

Molecular detection of 7SL-derived small RNA is a promising alternative for trypanosomosis diagnosis

Equine trypanosomosis comprises different parasitic diseases caused by protozoa of the subgenus Trypanozoon: Trypanosoma equiperdum (causative agent of dourine), Trypanosoma brucei (nagana) and Trypanosoma evansi (surra). Due to the absence of a vaccine and the lack of efficacy of the few available drugs, these diseases represent a major health and economic problem for international equine trade. Development of affordable, sensitive and specific diagnostic tests is therefore crucial to ensure the control of these diseases. Recently, it has been shown that a small RNA derived from the 7SL gene (7SL-sRNA) is produced in high concentrations in sera of cattle infected with Trypanosoma congolense, Trypanosoma vivax and Trypanosoma brucei. Our objective was to determine whether 7SL-sRNA could serve as a marker of active infection in equids experimentally infected with Trypanosoma equiperdum by analysing the sensitivity, specificity and stability of the 7SL-sRNA. Using a two-step RT-qPCR, we were able to detect the presence of 7SL-sRNA between 2 and 7 days post-infection, whereas seroconversion was detected by complement fixation test between 5 and 14 days post-infection. There was a rapid loss of 7SL-sRNA signal from the blood of infected animals one day post-trypanocide treatment. The 7SL-sRNA RT-qPCR allowed an early detection of a treatment failure revealed by glucocorticoid-induced immunosuppression. In addition, the 7SL-sRNA remains detectable in positive sera after 7 days of storage at either 4°C, room temperature or 30°C, suggesting that there is no need to refrigerate serum samples before analysis. Our findings demonstrate continual detection of 7SL-sRNA over an extended period of experimental infection, with signals detected more than six weeks after inoculation. The detection of a strong and consistent 7SL-sRNA signal even during subpatent parasitemia and the early detection of treatment failure highlight the very promising nature of this new diagnostic method.

Nationwide serological surveillance of non-tsetse-transmitted horse trypanosomoses in Mongolia

In Mongolia, horses play important roles, not only in livestock production, but also in terms of culture, tradition, and Mongolian beliefs. Although the presence of non-tsetse-transmitted horse trypanosomoses, which are caused by infections with Trypanosoma evansi (surra) and T. equiperdum (dourine), has been reported in the country, whether there is a nationwide epidemic of these infectious diseases is unknown. In the present study, a nationwide surveillance of horse trypanosomoses was performed. The sample sizes for each province, the whole country, and male and female horses were, respectively, 96, 2,400, and 316 and 306. In total, 3,641 samples of horse sera were collected by simple random sampling. The rTeGM6-4r-based ELISA, which was applied for surra against cattle and water buffalo and dourine against horse, revealed that the overall sero-prevalence of the diseases in Mongolia was 4.8%. Among them, high sero-prevalences were observed in the central provinces (5.2–11.0%, p < 0.05) of the country. The sero-prevalence was significantly higher in females than in males (6.0% and 4.0%, p < 0.05, respectively) and in non-castrated males (8.4%, p < 0.01) compared with castrated males (3.0%). These results suggested that currently, horse trypanosomoses are a nationwide endemic problem in Mongolia. Knowledge of the nationwide endemic status of non-tsetse-transmitted horse trypanosomoses in Mongolia will be useful to prevent these diseases.

First outbreak of autochthonous "surra" in horses in Santa Catarina State, Brazil: Parasitological, hematological and biochemical characteristics

This study reports the first autochthonous "surra" outbreak in horses in the State of Santa Catarina, southern Brazil. Six horses with clinical suspicion of trypanosomosis had the natural infection by T. evansi confirmed by PCR and rapid serum agglutination test. Clinical, parasitological, and hematology evaluations were performed at initial observation (T0) and 90 days after (T1). At T0, all animals that tested positive for T. evansi in PCR presented with severe clinical signs and out of normal range hematological hematological (hematocrit, leukocytes, platelets, hemoglobin) and serum biochemical parameters (alanine aminotransferase (ALT), creatinine phosphokinase (CPK), lactate dehydrogenase (LDH), creatinine, bilirubin, and glucose). At T1, the progressive clinical recovery of animals, normalization of hemato-biochemical parameters, and negative PCR results for T. evansi were observed. It was not possible to identify the vector/mechanism of transmission through which animals were infected; therefore, the implementation of surveillance and control measures is essential to prevent the spread of this disease in horse herds, as well as to other animal species.

Screening and Identification of Pathogen Box® Compounds with anti-Trypanosoma evansi Activity

The development of new drugs targeting neglected animal diseases is imperative. In Asia and South America, Trypanosoma evansi is a pathogen that affects horses and other species, causing economic losses associated with reduced animal productivity and death. In order to accelerate the identification of drugs with activity against neglected diseases, Medicines for Malaria Venture has developed Pathogen Box®, a library of 400 different molecules. The present work aimed to identify compounds present in the Pathogen Box® library, measuring in vitro activity against T. evansi. Among the 400 compounds, 5 showed anti-T.evansi activity: pentamidine, MMV688410, MMV687273, MMV022478 and auranofin. Suramin, a trypanocidal activity molecule present on the Pathogen Box® reference compound list, demonstrated no anti-T. evansi activity in the in vitro assays. MMV688410 is the most promising candidate because it induces death and reduces the number of parasites in cell culture, and mainly because its mechanism of action is probably associated with inhibition of trypanosomal reductase enzyme, an exclusive target of trypanosomatides. Further in vitro and in vivo assays are needed to determine the efficacy of the compounds identified in this work, especially by associating tissue distribution and the ability of drugs to cross the blood brain barrier, as T. evansi is able to invade the central nervous system.

The current drug discovery landscape for trypanosomiasis and leishmaniasis: Challenges and strategies to identify drug targets

Human trypanosomiasis and leishmaniasis are vector-borne neglected tropical diseases caused by infection with the protozoan parasites Trypanosoma spp. and Leishmania spp., respectively. Once restricted to endemic areas, these diseases are now distributed worldwide due to human migration, climate change, and anthropogenic disturbance, causing significant health and economic burden globally. The current chemotherapy used to treat these diseases has limited efficacy, and drug resistance is spreading. Hence, new drugs are urgently needed. Phenotypic compound screenings have prevailed as the leading method to discover new drug candidates against these diseases. However, the publication of the complete genome sequences of multiple strains, advances in the application of CRISPR/Cas9 technology, and in vivo bioluminescence-based imaging have set the stage for advancing target-based drug discovery. This review analyses the limitations of the narrow pool of available drugs presently used for treating these diseases. It describes the current drug-based clinical trials highlighting the most promising leads. Furthermore, the review presents a focused discussion on the most important biological and pharmacological challenges that target-based drug discovery programs must overcome to advance drug candidates. Finally, it examines the advantages and limitations of modern research tools designed to identify and validate essential genes as drug targets, including genomic editing applications and in vivo imaging.

Comparison of serological and molecular tests for detection of Trypanosoma evansi in domestic animals from Ghardaïa district, South Algeria

Trypanosoma evansi (T. evansi) is a hemoflagellate parasite that affects a broad range of mammalian hosts and that causes a disease called surra. Diagnosis of surra based on clinical symptoms alone is inaccurate. Therefore, a variety of serological and molecular diagnostic tests are used to assist in the detection of T. evansi infections. The aim of this study was to compare the diagnostic performance of four serological tests (CATT/T.evansi, immune trypanolysis, ELISA with purified variant surface glycoprotein RoTat 1.2 and with whole cell lysate) and two molecular PCR tests targeting sequences within the ribosomal genes locus (ITS1 TD PCR and 18S qPCR). Tests were carried out on blood samples from 161 dromedary camels, 93 horses, 129 goats, 168 sheep, 127 bovines and 76 dogs. Latent class analysis was carried out to calculate the sensitivity and specificity of each diagnostic test. Cohen's Kappa test was used to assess the concordance between the different diagnostic tests. Overall positivity rates observed with the serological tests were as follows: 3.1 % with CATT/T.evansi, 4.9 % with ELISA/RoTat 1.2, 3.4 % with ELISA/whole lysate and 2.0 % with immune trypanolysis (TL). Among the 754 samples tested with the molecular tests, 1.7 % were positive with 18S qPCR and 1.3 % with ITS1 TD PCR. Cohen's Kappa test showed agreement ranging from fair to substantial (k = 0.2-0.8) between serological diagnostic tests. However, it showed a perfect agreement (k = 0.868) between molecular diagnostic tests. Latent class analysis showed that all serological tests were 100 % sensitive, in contrast to the molecular tests with 47 % sensitivity. All tests, though, were highly specific (≥ 97 %). Given the persistence of circulating antibodies after cure, detectable by serological tests, it is recommend combining a serological and a molecular diagnostic test for accurate diagnosis of infection with T. evansi in domestic animals.

Prevalence of Trypanosoma evansi in livestock in Palestine

Background

Trypanosoma evansi is the causative agent of surra, a disease that occurs in many animal species. The disease is responsible for substantial losses in global production and can be fatal if not diagnosed early. This study aims to determine the prevalence of T. evansi in livestock, equids and dromedary camels in Palestine.

Methods

Blood samples were collected during 2015–2017 from domesticated animals (n = 259 animals; 77% females and 23% males) including camels (n = 87), horses (n = 46), donkeys (n = 28), mules (n = 2), sheep (n = 49) and goats (n = 48) from eight districts: Ariha (Jericho), Nablus, Bethlehem, Deir Al Balah, Jenin, Rafah, Tubas, and Khan Yunis. Parasite prevalence was determined using PCR and blood smear microscopy. PCR-positive samples were further phylogenetically analyzed using DNA sequences of the 18S ribosomal RNA gene.

Results

The overall infection prevalence was 18% (46/259). The positivity rates according to PCR and microscopy examination were 17% (45/259) and 2.7% (7/259), respectively. The infection rates were as follows: camels, 26/61 (30%); horses, 8/46 (17%); donkeys, 3/28 (11%); mules, 1/2 (50%); sheep, 2/42 (4%); and goats, 6/42 (13%). Phylogenetic analyses of the 18S rRNA gene showed that 24 positive T. evansi samples from Palestine formed a monophyletic cluster with seven T. evansi sequences from Africa, Asia and South America, and three T. brucei sequences from Africa retrieved from GenBank. The spatial analysis showed three statistically significant foci of T. evansi infection in Jenin, Tubas (P = 0.02) and Ariha (Jericho) (P = 0.04). No statistically significant foci were detected in the Gaza Strip.

Conclusions

To the best of our knowledge, this is the first confirmation of high levels of infection with T. evansi as a causative agent of surra in Palestine. Our study emphasizes the need for a stringent surveillance system and risk assessment studies as prerequisites for control measures. Further investigations focusing on vectors and evaluation of risk factors are needed.

Treatment Efficiency of Combination Therapy With Diminazene Aceturate and Quinapyramine Sulfate in a Horse With Dourine

Dourine is a lethal protozoan disease of equids, and it is caused by Trypanosoma equiperdum infection via coitus. To date, treatment strategies against the dourine are not recommended because of the frequent relapses; therefore, the World Organisation for Animal Health recommends the stamping-out policy for the control of dourine. Our previous studies have revealed a number of horses with dourine in Mongolia that is the fifth largest horse-breeding country. It is difficult to apply the stamping-out policy for cases of dourine in Mongolia because of an inadequate livestock guarantee system. Therefore, the development of effective treatment measures is an urgent need. In this study, an 8-year-old stallion was definitely diagnosed with dourine based on clinical signs, molecular analysis, and microscopic examination of trypanosomes. Combination therapy with diminazene aceturate and quinapyramine sulfate was applied. Before the treatment, the characteristic clinical signs of dourine were observed, and trypanosomes were detected in the urogenital tract mucosal swab samples by microscopic examination and polymerase chain reaction (PCR). Moreover, positive serological results were obtained. After the treatment, we observed an improvement in the health of the treated horse and no trypanosome infection in its urogenital tract by microscopic examination and PCR. Moreover, serological tests showed seronegative results. The horse has showed no relapse for at least 2.5 years after the treatment, and its reproductive ability has improved. Our result suggests that trypanosomes did not invade cerebrospinal fluid when we started the therapy. In conclusion, the combination therapy has therapeutic potential against dourine at an early phase.

Indigofera oblongifolia as a fight against hepatic injury caused by murine trypanosomiasis

Trypanosoma evansi is a hazardous pathogenic parasite infecting a broad variety of livestock and affects wildlife worldwide. Trypanosoma evansi has gained resistance to most drugs used; therefore, it requires alternative medicines. The objective of this research was to investigate the impact of Indigofera oblongifolia leaf extract (IE) on T. evansi-induced hepatic injury.

Mice were once infected with 1000 T. evansi. The treated group was gavaged with 100 mg/Kg IE after infection. Histological and biochemical changes in mice hepatic tissue were studied. Also, the oxidative damage in the liver was evaluated through determining the level of glutathione (GSH), Malondialdehyde (MDA), nitric oxide (NO) and catalase (CAT) markers. IE was able to suppress the induced parasitemia due to infection. Also, IE improved the histological liver architecture. Furthermore, the liver enzymes, alanine aminotransferase (ALT), aspartate aminotransferase (AST), and alkaline phosphatase (ALP) activity were improved after IE mice were treated. IE protects against hepatic damage caused by trypanosomiasis in mice. Further studies are needed to isolate the active compounds in IE and to monitor these compunds’ ameliorative function.

Histopathological lesions in reproductive organs, distal spinal cord and peripheral nerves of horses naturally infected with Trypanosoma equiperdum

Background

Dourine, a venereal transmitted trypanosomosis caused by Trypanosoma equiperdum, has different clinical signs related to the reproductive and nervous system. Pathologic tissue changes associated with the disease are poorly described. The present study describes the histopathological lesions in naturally T. equiperdum-infected horses in the chronical stage of dourine.

Results

Four chronically dourine diseased horses underwent a post-mortem examination. They were Woo test negative, but CATT/T. evansi positive, had a low packed cell volume (PCV) and exhibited obvious clinical signs of dourine. Post-mortem examination did not reveal gross lesions in the organs assumed to be responsible for the symptomatology. On histopathology, genital organs were affected, with mononuclear cell infiltration and erosions and degeneration of seminiferous tubules and perivascular lymphoplasmacytic cuffing in the uterus. In the nervous system, mononuclear cell infiltration was located in peripheral nerves, ganglia and in the spinal cord, leading to axonal degeneration. Real-time PCR using ITS primer revealed the presence of trypanosomes in these organs and conventional PCRs using maxicircle and RoTat1.2 primers further confirmed the involvement of T. equiperdum since the DNAs from the vagina, testicle, distal spinal cord, sciatic and obturator nerves found to be positive for maxicircle and negative for RoTat 1.2.

Conclusions

The histopathological lesions in the spinal cord and peripheral nerves explain the incoordination of the hind legs in T. equiperdum-infected horses, whilst its presence in the genital tract exemplifies the venereal transmission.

Equine trypanosomosis: enigmas and diagnostic challenges

Equine trypanosomosis is a complex of infectious diseases called dourine, nagana and surra. It is caused by several species of the genus Trypanosoma that are transmitted cyclically by tsetse flies, mechanically by other haematophagous flies, or sexually. Trypanosoma congolense (subgenus Nannomonas) and T. vivax (subgenus Dutonella) are genetically and morphologically distinct from T. brucei, T. equiperdum and T. evansi (subgenus Trypanozoon). It remains controversial whether the three latter taxa should be considered distinct species. Recent outbreaks of surra and dourine in Europe illustrate the risk and consequences of importation of equine trypanosomosis with infected animals into non-endemic countries. Knowledge on the epidemiological situation is fragmentary since many endemic countries do not report the diseases to the World Organisation for Animal Health, OIE. Other major obstacles to the control of equine trypanosomosis are the lack of vaccines, the inability of drugs to cure the neurological stage of the disease, the inconsistent case definition and the limitations of current diagnostics. Especially in view of the ever-increasing movement of horses around the globe, there is not only the obvious need for reliable curative and prophylactic drugs but also for accurate diagnostic tests and algorithms. Unfortunately, clinical signs are not pathognomonic, parasitological tests are not sufficiently sensitive, serological tests miss sensitivity or specificity, and molecular tests cannot distinguish the taxa within the Trypanozoon subgenus. To address the limitations of the current diagnostics for equine trypanosomosis, we recommend studies into improved molecular and serological tests with the highest possible sensitivity and specificity. We realise that this is an ambitious goal, but it is dictated by needs at the point of care. However, depending on available treatment options, it may not always be necessary to identify which trypanosome taxon is responsible for a given infection.

Reduction of Trypanosoma equiperdum from equine semen by single layer centrifugation

Trypanosoma equiperdum (T. equiperdum) causes dourine, a venereally transmitted infection in horses. Purification of semen by single layer centrifugation (SLC) has been proven to be successful in reducing venereally transmitted diseases when dealing with other pathogens. The objective of this study was to evaluate the purification of T. equiperdum spiked semen by SLC. Semen was spiked using cryopreserved T. equiperdum stabilates (Dodola strain isolate 943). In total, 6 concentrations, varying from 10² to >5 × 10⁶ trypanosomes, were added to semen samples. Subsequently, SLC was performed following standard procedures. The presence of the parasite in the purified semen was checked by wet smear examination, ITS1 PCR and in vivo inoculation in mice. Before SLC, all spiked semen samples, except the negative controls, were positive on PCR analysis. After SLC, all the pellets were found to be negative for T. equiperdum on microscopic examinations. Examination of the pellet by PCR could also not detect any parasite-DNA in the SLC-pellet of semen spiked with the lower number of parasites (10² to10⁴ trypanosomes). However, in the SLC pellets spiked with 10⁴ - 5 × 10⁴ trypanosomes, only 1 out of the 4 replicates was negative for parasite DNA. All groups spiked with >5 × 10⁴ trypanosomes were found to be positive on PCR. All mice in the positive controls exhibited parasitaemia (5/5). Mice inoculated with SLC-purified semen that was spiked with lower than 5 × 10⁴ trypanosomes, remained free of parasitaemia, similar to the negative controls. However inoculation with SLC-pellets from samples with a higher number of trypanosomes (>5 × 10⁴ - 5 × 10⁶ and > 5 × 10⁶), induced parasitaemia in 2 out of 5 and 3 out of 5 mice, respectively. This study indicates that single layer centrifugation can be used to clear T. equiperdum infected semen but that the success is dependent on the number of parasites.

Tissue (re)distribution of Trypanosoma equiperdum in venereal infected and blood transfused horses

Dourine, caused by Trypanosoma equiperdum, is a life-threatening venereal disease in equidae. So far, there is no clear evidence on how and when stallions become infectious, nor which tissues are affected by the parasite in diseased animals. Post-infection, after a transient, temporary phase of parasitaemia, the parasite disperses to different tissues in an unknown distribution pattern. This study describes the distribution of the parasite after infection by artificial insemination (AI) or blood transfusion. Mares (N = 4) were artificially inseminated with T. equiperdum spiked semen whereas stallions (N = 4) were infected by blood transfusion. The course of the disease was monitored by parasitological (Woo) and molecular (PCR) tests and clinical signs and haematological parameters were recorded. At 120 days post infection, horses had a full necropsy, histopathology and PCR. A similar pattern of parasitaemia, disease progression and tissue distribution were seen in all horses. Ejaculated semen in the preclinical stage and epididymal semen in the chronic stage of the disease was positive on PCR and caused infection in mice. Cymelarsan^® treatment in the chronic stage did not result in a clinico-haematological or histopathological improvement. At necropsy, lesions were observed in the nervous and reproductive system. Histopathological lesions were most severe in the peripheral nerves and associated ganglia, the testicles and genital mucosae with multifocal infiltration of lymphocytes, plasma cells and histocytes. The parasites disseminated to several tissues including the nervous system, testicles and semen. The results indicate that transmission of T. equiperdum is possible through semen even from symptomless stallions post-treatment.

Indigofera oblongifolia protects against trypanosomiasis-induced spleen injury

BACKGROUND

Trypanosomiasis is a neglected tropical disease, transmitted by blood-sucking insects and can affect humans and animals, depending on the species of Trypanosoma parasite. Trypanosoma has acquired resistance to the majority of drugs used; hence, alternative medicines are required. Indigofera oblongifolia leaf extract (IOE) has been shown to treat blood stage malaria. Here, IOE was used to demonstrate its effect on Trypanosoma evansi-infected mice.

METHODS

Analysis of IOE by gas chromatography-mass spectrometry showed the presence of many active components like flavonoids and phenolics. The mice were divided into three groups as follows: vehicle control, T. evansi-infected mice and T. evansi-infected-treated mice.

RESULTS

The findings demonstrate a significant effect of IOE treatment on T. evansi-infected mice. Parasitemia was decreased by 70%, weight loss was reduced, and splenomegaly was significantly decreased. Additionally, IOE improved the histological architecture of the spleen, as shown by the improved histological injury score post-treatment. Anemia was apparent during the course of infection in T. evansi-infected mice; this was reversed upon treatment with IOE to almost the normal level of hemoglobin and erythrocytes. Reduced glutathione and catalase were also ameliorated upon IOE treatment compared to T. evansi-infected mice.

CONCLUSION

Overall, this study shows the ameliorative role of IOE against T. evansi-induced spleen injury in mice.

Polyradiculoneuropathy in dourine-affected horses

Dourine is an equine protozoan disease caused by Trypanosoma equiperdum. Dourine-afflicted animals die after developing neurological clinical signs, such as unilateral paresis. The disease has been a problem for many years; however, the pathogenesis regarding the neurological clinical signs of dourine has been unclear. In the present study, we conducted a histopathological examination in order to investigate the mechanisms by which dourine-afflicted horses develop the accompanying neurological clinical signs. Four dourine-afflicted horses in Mongolia were evaluated. An apparently healthy horse exhibited multifocal neuritis without axonal or myelin degeneration. The other horses, which had obvious neurological clinical signs, also exhibited multifocal neuritis. In particular, the nerves that innervated areas associated with neurological clinical signs exhibited neuritis with demyelination in the latter horses. Inflamed, non-demyelinating nerves were infiltrated with B lymphocytes and T lymphocytes; while inflamed, demyelinating nerves were infiltrated with mononuclear phagocytes. Our observations revealed lesion progression in the nerves, such that polyradiculoneuropathy could explain the accompanying neurological clinical signs of dourine. To our knowledge, this is the first report to describe a pathogenic mechanism for the development of the neurological clinical signs found in dourine-afflicted horses.

Epidemiological survey of hemoprotozoan parasites in cattle from low-country wet zone in Sri Lanka

The diseases caused by hemoprotozoan parasites in cattle often result in economic losses. In Sri Lanka, previous studies found that the up-country wet zone, which is located in central Sri Lanka, was characterized by a high rate of Theileria orientalis and a low rate of Theileria annulata compared with the dry zone. In this study, DNA samples were prepared from the blood of 121 cattle in Galle, a coastal district located in low-country wet zone in Sri Lanka, and were PCR-screened for Babesia bovis, Babesia bigemina, T. annulata, T. orientalis, and Trypanosoma theileri. All the parasite species, except B. bovis, were detected among the surveyed cattle. The animals had a high rate of T. orientalis (100%) and a low rate of T. annulata (1.6%), as in the up-country wet zone. Babesia bigemina and Tr. theileri were detected in 19.0% and 20.6% of the animals, respectively, and their infection rates were higher in the animals reared in extensive management systems (32.8% and 27.9%, respectively) than in those managed in intensive/semi-intensive systems (5.0% and 13.3%, respectively). Genotypic analyses found that the T. orientalis mpsp type 5 was predominant similar to up-country wet zone, and that Tr. theileri consisted of seven catl genotypes, including two new genotypes (IL and IM) and four previously detected genotypes (IA, IB, II, and IK). These findings suggest that the hemoprotozoan infection profiles are largely conserved within the wet zone, despite differences in the geography, cattle breeds, and management practices between the up-country and low-country wet zones.

Evaluation and correlation of oxidative stress and haemato-biochemical observations in horses with natural patent and latent trypanosomosis in Punjab state of India

The haemato-biochemical indices and oxidative stress markers in horses naturally infected with Trypanosoma evansi were evaluated by analyzing the level of these parameters between T. evansi infected (microscopically positive patent group and PCR positive latent group) and infection free horses. To compare the hemato-biochemical indices and oxidative stress indicators, horses were divided into three categories based on diagnostic test employed and positive results obtained. These included Romanowsky stained slide positive group (Group I; n = 6), PCR positive group (group II; n = 28) and negative control group (group III, n = 30), revealing parasitologically positive patent, molecular positive latent and disease free status of horses. A significant reductions in total erythrocytes count (TEC, P = 0.01), haemoglobin (Hb, P = 0.01) and packed cell volume (PCV, P = 0.04) was noticed both in group I and group II while significant neutrophilia and lymphocytopenia was observed in group I when compared to negative control group. Substantial increase in creatinine (CRTN, P = 0.032) and gamma glutamyl transferase (GGT, P = 0.012) in group I while significant decrease in glucose (GLU, P = 0.04) and iron (Fe, P = 0.01) were noticed in both group I and group II in comparison to group III. A significant difference in lipid peroxides (LPO, P = 0.01) with highest level in patent group I (15.33 ± 0.53) followed by PCR positive latent group (14.09 ± 1.66) indicates higher lipid peroxidation in erythrocytes and oxidative stress in decreasing order when compared with infection free control horses (9.83 ± 0.97). Catalase (CAT, P = 0.01) was significantly lower in parasitological (0.82 ± 0.14) and molecular positive cases (1.27 ± 0.35) in comparison to control group (3.43 ± 0.96). The levels of superoxide dismutase (SOD, P = 0.01), reduced glutathione (GSH, P = 0.01) and ferric reducing antioxidant power (FRAP, P = 0.01) were significantly lower in parasito-molecular positive cases as compared to infection free control horses. An inverse correlation of RBC count with LPO and GSH and a direct correlation with catalase, SOD and FRAP was revealed. Overall, the observed substantial decreases in the oxidative parameters like catalase CAT, SOD, GSH and FRAP activities with remarkably elevated levels of LPO indicate high exposure of erythrocytes to oxidative damage in T.evansi infected horses.

Glucose deprivation activates a cAMP-independent protein kinase from Trypanosoma equiperdum

Kemptide (sequence: LRRASLG) is a synthetic peptide holding the consensus recognition site for the catalytic subunit of the cAMP-dependent protein kinase (PKA). cAMP-independent protein kinases that phosphorylate kemptide were stimulated in Trypanosoma equiperdum following glucose deprivation. An enriched kemptide kinase-containing fraction was isolated from glucose-starved parasites using sedimentation throughout a sucrose gradient, followed by sequential chromatography on diethylaminoethyl-Sepharose and Sephacryl S-300. The trypanosome protein possesses a molecular mass of 39.07-51.73 kDa, a Stokes radius of 27.4 Ǻ, a sedimentation coefficient of 4.06 S and a globular shape with a frictional ratio f/fo = 1.22-1.25. Optimal enzymatic activity was achieved at 37 °C and pH 8.0, and kinetic studies showed Km values for ATP and kemptide of 11.8 ± 4.1 and 24.7 ± 3.8 µm, respectively. The parasite enzyme uses ATP and Mg2+ and was inhibited by other nucleotides and/or analogues of ATP, such as cAMP, AMP, ADP, GMP, GDP, GTP, CTP, β,γ-imidoadenosine 5'-triphosphate and 5'-[p-(fluorosulfonyl)benzoyl] adenosine, and by other divalent cations, such as Zn2+, Mn2+, Co2+, Cu2+, Ca2+ and Fe2+. Additionally, the trypanosome kinase was inhibited by the PKA-specific heat-stable peptide inhibitor PKI-α. This study is the first biochemical and enzymatic characterization of a protein kinase from T. equiperdum.

Melarsomine hydrochloride (Cymelarsan®) fails to cure horses with Trypanosoma equiperdum OVI parasites in their cerebrospinal fluid

The aim of this study was to evaluate the ability of melarsomine hydrochloride (Cymelarsan^®) to cure horses suffering from a nervous form of dourine, a sexually-transmitted disease caused by Trypanosoma equiperdum. The recently described experimental model for assessing drug efficacy against horse trypanosomosis allowed us to obtain eight horses (Welsh pony mares) infected by T. equiperdum with parasites in their cerebrospinal fluid. The Cymelarsan^® treatment evaluated consisted of the daily administration of 0.5 mg/kg of Cymelarsan^® over 7 days. Two control horses remained untreated, three horses received the treatment 36 days p.i. and three horses received the treatment 16 days p.i. Following treatment, we observed parasite clearance in blood, stabilization of rectal temperature and a relative improvement in the mean packed cell volume levels for all treated horses. However, live parasites were later observed again in the CSF of all treated horses. Our results indicate the inability of Cymelarsan^® to reach Trypanozoon located in the central nervous system of infected horses and thus discourage the use of Cymelarsan^® to treat animals suffering from a nervous form of dourine.

Validation of a new experimental model for assessing drug efficacy against infection with Trypanosoma equiperdum in horses

Trypanosoma equiperdum, the causative agent of dourine, may affect the central nervous system, leading to neurological signs in infected horses. This location protects the parasite from most (if not all) existing chemotherapies. In this context, the OIE terrestrial code considers dourine as a non-treatable disease and imposes a stamping-out policy for affected animals before a country may achieve its dourine-free status. The use of practices as drastic as euthanasia remains controversial, but the lack of a suitable tool for studying a treatment's efficacy against dourine hampers the development of an alternative strategy for dourine infection management. The present study reports on the development of an experimental infection model for assessing drug efficacy against the nervous form of dourine. The model combines the infection of horses by Trypanosoma equiperdum and the search for trypanosomes in the cerebrospinal fluid (CSF) through an ultrasound-guided cervical sampling protocol. After a development phase involving four horses, we established an infection model that consists of inoculating 5 × 10⁴T. equiperdum OVI parasites intravenously into adult Welsh mares (Equus caballus). To evaluate its efficacy, eight horses were infected according to this model. In all these animals, parasites were observed in the blood at 2 days post-inoculation (p.i.) and in CSF (12.5 ± 1.6 days p.i.) and seroconversion was detected (8.25 ± 0.5 days p.i.). All eight animals also developed fever (rectal temperature > 39 °C), low hematocrit (< 27%), and ventral edema (7.9 ± 2.0 days p.i.), together with other inconstant clinical signs such as edema of the vulva (six out of eight horses) or cutaneous plaques (three out of eight horses). This model provides a robust infection protocol that induces an acute trypanosome infection and that allows parasites to be detected in the CSF of infected horses within a period of time compatible with animal experimentation constraints. We conclude that this model constitutes a suitable tool for analyzing the efficacy of anti-Trypanosoma drugs and vaccines.

Unraveling cryptic epizootiology of equid trypanosomosis in Punjab state of India by parasitological and sero-molecular techniques

To unravel equid trypanosomosis caused by Trypanosoma evansi in Punjab state of India, a cross sectional study was designed by utilizing parasitological and sero-molecular tools with objective to assess the prevalence of T. evansi in association with various risk factors in all agroclimatic zones of Punjab state of India. Parasitological Romanowksy stained thin blood smears (RSTBS) to detect patent infection, molecular techniques polymerase chain reaction I (PCR I; TBR 1/2 primers; targeting minichromosomal satellite DNA of T. evansi), polymerase chain reaction II (PCR II; TR 3/4 primers; targeting variable surface glycoprotein region DNA of T. evansi) & LAMP (Loop mediated isothermal amplification) assay to detect latent infection and serological assays card agglutination test (CATT/T. evansi) & ELISA (Enzyme linked immunosorbent assay) to detect exposure status of trypanosomosis were utilized in the present study. A total 429 equid blood and serum samples from all the five agroclimatic zones of Punjab state tested by these techniques showed a prevalence of 1.39% (CL: 0-15.28) by RSTBS, 6.52% (10.94-45.09) by both TBR 1/2 PCR and LAMP assay, 5.82% (11.57-38.42) by TR 3/4 PCR, 15.15% (36.57-135.42) with CATT/T. evansi and 22.84% (17.77-840.22) with ELISA. Interpretation of various risk factors revealed that the donkey/mules population (RR = 5.46, 95% [CI] = 0.15-15.56) was found to be at higher risk of T. evansi infection predominantly at 'unorganized' farms (RR = 4.06, 95% [CI] = 0.12-4.51). Animal used for commercial purposes (RR = 3.25, 95% [CI] = 0.06-7.42), rearing of equids with other domestic animals (RR = 2.36, 95% [CI] = 0.10-17.11) and farms without application of fly repellant/insecticides/net (RR = 3.68, 95% [CI] = 0.08-5.94) made them more prone to the disease. This comprehensive report utilizing the classical, serological and molecular diagnostic tools for epidemiology of T. evansi establishes the endemic stability of this infection in all agro climatic zones of Punjab with LAMP assay to be a promisingly sensitive and specific technique for the diagnosis of T. evansi under isothermal conditions in field situations.

Genome-wide analysis of Excretory/Secretory proteins in Trypanosoma brucei brucei: Insights into functional characteristics and identification of potential targets by immunoinformatics approach

Trypanosoma brucei brucei (T.b.brucei) is an extra-cellular parasite that causes Animal African Trypanosomiasis (AAT) disease in animals. Till day, this disease is more difficult to treat and control due to lack of efficient vaccines and early diagnosis of the parasite infection. T.b.brucei Excretory/Secretory (ES) proteins were involved in pathogenesis and key for understanding the host-parasite interactions. Functions of T.b.brucei's ES proteins were poorly investigated and experimental identification is expensive and time-consuming. Bioinformatics approaches are cost-effective by facilitating the experimental analysis of potential drug targets for parasitic diseases. Here we applied several bioinformatics tools to predict and functionalize the annotation of 1104 ES proteins and immunoinformatics approaches carried out to predict and evaluate the epitopes in T.b.brucei. Secretory information, functional annotations and potential epitopes of each ES proteins were available at http://tbb.insilico.in. This study provides functional information of T.b.brucei for experimental studies to identify potential targets for diagnosis and therapeutics development.

The utility of an rTeGM6-4r-based immunochromatographic test for the serological diagnosis of non-tsetse-transmitted equine trypanosomosis in rural areas of Mongolia

Our previous studies report epidemics of non-tsetse-transmitted equine trypanosomosis in Mongolia. However, the current status of non-tsetse-transmitted equine trypanosomosis endemicity remains to be clarified in some parts of Mongolia. We previously reported the potential application of rTeGM6-4r-based diagnostic tools, an rTeGM6-4r-based immunochromatographic test (ICT) and an enzyme-linked immunosorbent assay (ELISA), in the serological surveillance of equine trypanosomosis in Mongolia. In the present study, the utility of the rTeGM6-4r-based ICT was validated. The rTeGM6-4r-based ICT accurately diagnosed positive reference sera that had been prepared from dourine horses in Mongolia, similarly to the rTeGM6-4r-based ELISA. The diagnostic performance of the rTeGM6-4r-based ICT was maintained when the strips were preserved for at least 2 months under dry conditions. The ICT detected 42 positive serum samples from a total of 1701 equine sera that had been collected from all 21 provinces of Mongolia. The κ-value, sensitivity and specificity of rTeGM6-4r-based ICT were 0.58, 50.0% (95% CI, 37.7-62.3%) and 99.3% (95% CI, 98.7-99.6%), respectively, in comparison to the rTeGM6-4r-based ELISA. Our field-friendly rTeGM6-4r-based ICT was found to be useful for the serological diagnosis of non-tsetse-transmitted equine trypanosomosis in rural areas of Mongolia.