Field detection of resistance to isometamidium chloride and diminazene aceturate in Trypanosoma vivax from the region of the Boucle du Mouhoun in Burkina Faso

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.

Ethnoveterinary survey of trypanocidal medicinal plants of the beninese pharmacopoeia in the management of bovine trypanosomosis in North Benin (West Africa)

Cattle breeding is of great socio-economic importance for Benin's cattle farmers in general and those of North Benin in particular. The objective of this study is to inventory the natural products of medicinal plants of the Beninese pharmacopoeia for the management of trypanosomes in cattle in North Benin. The methodology consisted of individual and semi-structured interviews with cattle farmers on the use of medicinal plants. A total of 360 cattle farmers were selected and interviewed in twelve villages in four municipalities (Tchaourou, N'dali, Bembèrèkè and Gogounou) in northern Benin. Different quantitative ethnobotanical indices were calculated to determine the level of use of plant species. The Relative Frequency of Citation (RFC), the Informant Consensus Factor (ICF = 0.918) and the Generic Coefficient (Rg = 1.04) were evaluated. The knowledge of medicinal plants was influenced by the level of education and the main activity of those who practiced animal husbandry. The results yielded 48 medicinal plants for veterinary use belonging to 46 genera and 28 families. The Leguminosae family (12.50%) was the most represented. The most cited plants with a RFC above 10% were K. senegalensis, P. africana, K. africana, M. inermis, S. latifolius, M. polyandra. The parts used were leaves (46.15%); barks (24.62%) and roots (15.38%). Decoction (53.23%), plundering (32.26%) and maceration (11.26%) were the main methods of preparation. The administration was mainly by oral route. The calculated indices show a high diversity of medicinal plants with trypanocidal properties in the control of cattle trypanosomosis in the Sudanese and Sudano-Guinean zones of northern Benin. Plant species with high citation and RFC values should be selected for comprehensive pharmacological and phytochemical research to validate this ethnomedical knowledge in the management of cattle trypanosomosis.

Phytochemical Screening, Antioxidant Activity, and Acute Toxicity Evaluation of Senna italica Extract Used in Traditional Medicine

Medicinal plants such as Senna italica are increasingly used for their purgative virtues to treat stomach aches, fever, and jaundice. This study aims to screen the phytochemical compounds and to assess the antioxidant activity in vitro and the acute oral toxicity in vivo of Senna italica leaves. The plant was harvested, dried, pulverized, and preserved. Phytochemical screening was performed using different laboratory protocols. Ethanolic and aqueous extracts were, respectively, obtained by maceration and decoction technics. The assay for free radical scavenging was used to examine the antioxidant activity using DPPH. Acute oral toxicity was performed with aqueous and ethanolic extracts at 5000 mg/kg of body weight on female albinos Wistar rats, weighing 152.44 ± 3.68 g. Subjects were checked for any signs of mortality and macroscopy toxicity during the 14 days of the study. Biochemical and hematological parameters were measured to assess liver and kidney functions, and histological analysis of these organs was conducted. Phytochemical analysis highlighted the presence of total phenols, flavones, tannins, alkaloids, and quinone derivatives. Semiethanolic (78 μg/mL), ethanolic (9.7 μg/mL), and aqueous extract (9.2 μg/mL) showed an interesting antioxidant activity. Biochemical and hematological parameters were normal and not significantly different (p > 0.05). The plant extracts did not produce any toxic effect or mortality at the provided dose. Senna italica extracts induced an increase in the volume of liver and kidney tissues but no necrosis. Thus, lethal dose 50 of Senna italica leaf extract is probably higher than 5000 mg/kg.

Therapeutic Efficacy of Orally Administered Nitrofurantoin against Animal African Trypanosomosis Caused by Trypanosoma congolense Infection

Animal African trypanosomosis (AAT) leads to emaciation and low productivity in infected animals. Only six drugs are commercially available against AAT; they have severe side effects and face parasite resistance. Thus, the development of novel trypanocidal drugs is urgently needed. Nitrofurantoin, an antimicrobial, is used for treating bacterial urinary tract infections. Recently, we reported the trypanocidal effects of nitrofurantoin and its analogs in vitro. Furthermore, a nitrofurantoin analog, nifurtimox, is currently used to treat Chagas disease and chronic human African trypanosomiasis. Thus, this study was aimed at evaluating the in vivo efficacy of nitrofurantoin in treating AAT caused by Trypanosoma congolense. Nitrofurantoin was orally administered for 7 consecutive days from 4 days post-infection in T. congolense-infected mice, and the animals were observed for 28 days. Compared to the control group, the treatment group showed significantly suppressed parasitemia at 6 days post-infection. Furthermore, survival was significantly prolonged in the group treated with at least 10 mg/kg nitrofurantoin. Moreover, 100% survival and cure was achieved with a dose of nitrofurantoin higher than 30 mg/kg. Thus, oral nitrofurantoin administration has potential trypanocidal efficacy against T. congolense-induced AAT. This preliminary data will serve as a benchmark when comparing future nitrofurantoin-related compounds, which can overcome the significant shortcomings of nitrofurantoin that preclude its viable use in livestock.

An atlas to support the progressive control of tsetse-transmitted animal trypanosomosis in Burkina Faso

Background

African animal trypanosomosis (AAT), transmitted by tsetse flies, is arguably the main disease constraint to integrated crop-livestock agriculture in sub-Saharan Africa, and African heads of state and governments adopted a resolution to rid the continent of this scourge. In order to sustainably reduce or eliminate the burden of AAT, a progressive and evidence-based approach is needed, which must hinge on harmonized, spatially explicit information on the occurrence of AAT and its vectors.

Methods

A digital repository was assembled, containing tsetse and AAT data collected in Burkina Faso between 1990 and 2019. Data were collected either in the framework of control activities or for research purposes. Data were systematically verified, harmonized, georeferenced and integrated into a database (PostgreSQL). Entomological data on tsetse were mapped at the level of individual monitoring traps. When this was not possible, mapping was done at the level of site or location. Epidemiological data on AAT were mapped at the level of location or village.

Results

Entomological data showed the presence of four tsetse species in Burkina Faso. Glossina tachinoides, present from the eastern to the western part of the country, was the most widespread and abundant species (56.35% of the catches). Glossina palpalis gambiensis was the second most abundant species (35.56%), and it was mainly found in the west. Glossina morsitans submorsitans was found at lower densities (6.51%), with a patchy distribution in the southern parts of the country. A single cluster of G. medicorum was detected (less than 0.25%), located in the south-west. Unidentified tsetse flies accounted for 1.33%. For the AAT component, data for 54,948 animal blood samples were assembled from 218 geographic locations. The samples were tested with a variety of diagnostic methods. AAT was found in all surveyed departments, including the tsetse-free areas in the north. Trypanosoma vivax and T. congolense infections were the dominant ones, with a prevalence of 5.19 ± 18.97% and 6.11 ± 21.56%, respectively. Trypanosoma brucei infections were detected at a much lower rate (0.00 ± 0.10%).

Conclusions

The atlas provides a synoptic view of the available information on tsetse and AAT distribution in Burkina Faso. Data are very scanty for most of the tsetse-free areas in the northern part of the country. Despite this limitation, this study generated a robust tool for targeting future surveillance and control activities. The development of the atlas also strengthened the collaboration between the different institutions involved in tsetse and AAT research and control in Burkina Faso, which will be crucial for future updates and the sustainability of the initiative.

Graphical Abstract

Supplementary Information

The online version contains supplementary material available at 10.1186/s13071-021-05131-4.

New Series of Imidazoles Showed Promising Growth Inhibitory and Curative Potential Against Trypanosoma Infection

The Trypanosoma spp. cause animal and human trypanosomiasis characterized with appreciable health and economic burden mostly in developing nations. There is currently no effective therapy for this parasitic disease, due to poor drug efficacy, drug resistance, and unwanted toxicity, etc. Therefore, new anti-Trypanosoma agents are urgently needed. This study explored new series of imidazoles for anti-Trypanosoma properties in vitro and in vivo. The imidazoles showed moderate to strong and specific action against growth of T. congolense. For example, the efficacy of the imidazole compounds to restrict Trypanosoma growth in vitro was ≥ 12-fold specific towards T. congolense relative to the mammalian cells. Additionally, the in vivo study revealed that the imidazoles exhibited promising anti-Trypanosoma efficacy corroborating the in vitro anti-parasite capacity. In particular, three imidazole compounds (C1, C6, and C8) not only cleared the systemic parasite burden but cured infected rats after no death was recorded. On the other hand, the remaining five imidazole compounds (C2, C3, C4, C5, and C7) drastically reduced the systemic parasite load while extending survival time of the infected rats by 14 days as compared with control. Untreated control died 3 days post-infection, while the rats treated with diminazene aceturate were cured comparable to the results obtained for C1, C6, and C8. In conclusion, this is the first study demonstrating the potential of these new series of imidazoles to clear the systemic parasite burden in infected rats. Furthermore, a high selectivity index of imidazoles towards T. congolensein vitro and the oral LD₅₀ in rats support anti-parasite specific action. Together, findings support the anti-parasitic prospects of the new series of imidazole derivatives.

Diminazene resistance in Trypanosoma congolense is not caused by reduced transport capacity but associated with reduced mitochondrial membrane potential

Trypanosoma congolense is a principal agent causing livestock trypanosomiasis in Africa, costing developing economies billions of dollars and undermining food security. Only the diamidine diminazene and the phenanthridine isometamidium are regularly used, and resistance is widespread but poorly understood. We induced stable diminazene resistance in T. congolense strain IL3000 in vitro. There was no cross-resistance with the phenanthridine drugs, melaminophenyl arsenicals, oxaborole trypanocides, or with diamidine trypanocides, except the close analogs DB829 and DB75. Fluorescence microscopy showed that accumulation of DB75 was inhibited by folate. Uptake of [³ H]-diminazene was slow with low affinity and partly but reciprocally inhibited by folate and by competing diamidines. Expression of T. congolense folate transporters in diminazene-resistant Trypanosoma brucei brucei significantly sensitized the cells to diminazene and DB829, but not to oxaborole AN7973. However, [³ H]-diminazene transport studies, whole-genome sequencing, and RNA-seq found no major changes in diminazene uptake, folate transporter sequence, or expression. Instead, all resistant clones displayed a moderate reduction in the mitochondrial membrane potential Ψm. We conclude that diminazene uptake in T. congolense proceed via multiple low affinity mechanisms including folate transporters; while resistance is associated with a reduction in Ψm it is unclear whether this is the primary cause of the resistance.

Global distribution, host range and prevalence of Trypanosoma vivax: a systematic review and meta-analysis

BACKGROUND

Trypanosomosis caused by Trypanosoma vivax is one of the diseases threatening the health and productivity of livestock in Africa and Latin America. Trypanosoma vivax is mainly transmitted by tsetse flies; however, the parasite has also acquired the ability to be transmitted mechanically by hematophagous dipterans. Understanding its distribution, host range and prevalence is a key step in local and global efforts to control the disease.

METHODS

The study was conducted according to the methodological recommendations of the Preferred Reporting Items for Systematic Reviews and Meta-Analyses (PRISMA) checklist. A systematic literature search was conducted on three search engines, namely PubMed, Scopus and CAB Direct, to identify all publications reporting natural infection of T. vivax across the world. All the three search engines were screened using the search term Trypanosoma vivax without time and language restrictions. Publications on T. vivax that met our inclusion criteria were considered for systematic review and meta-analysis.

RESULT

The study provides a global database of T. vivax, consisting of 899 records from 245 peer-reviewed articles in 41 countries. A total of 232, 6277 tests were performed on 97 different mammalian hosts, including a wide range of wild animals. Natural infections of T. vivax were recorded in 39 different African and Latin American countries and 47 mammalian host species. All the 245 articles were included into the qualitative analysis, while information from 186 cross-sectional studies was used in the quantitative analysis mainly to estimate the pooled prevalence. Pooled prevalence estimates of T. vivax in domestic buffalo, cattle, dog, dromedary camel, equine, pig, small ruminant and wild animals were 30.6%, 6.4%, 2.6%, 8.4%, 3.7%, 5.5%, 3.8% and 12.9%, respectively. Stratified according to the diagnostic method, the highest pooled prevalences were found with serological techniques in domesticated buffalo (57.6%) followed by equine (50.0%) and wild animals (49.3%).

CONCLUSION

The study provides a comprehensive dataset on the geographical distribution and host range of T. vivax and demonstrates the potential of this parasite to invade other countries out of Africa and Latin America.

Molecular Identification of ABC2 Transporter Gene Encode Protein Ngawi Trypanosoma evansi Isolate that suspected resistance to Isometamidium Chloride

This study aims to determine the profile of the ABC2 encoding transporter on Trypanosoma evansi (T. evansi) Ngawi isolates, Indonesia, exposed with Isometamidium Chloride (ISM). This study used blood samples of mice containing Trypanosoma evansi that had been exposed with ISM 0.05 mg/kg BW, ISM 0.1 mg/kg BW and ISM 0.3 mg/kg BW for 4 weeks, and control group. Blood samples were extracted and amplified using primers. ABC2 F 5 ’GCTTGTCCGACCATCTTGCA 3’ and ABC2 R 5 ’AGGTCCACTCCCATGCTACA 3’ that produced 350 basepairs (bp). The sequencing results were then analyzed using BLAST and MEGA 7.0. There was 1 deference nucleotide (107) derived from multiple alignments, while in amino acids there was no difference in all samples. Trypanosoma evansi which was exposed with ISM does not have many differences in nucleotide or amino acid and only one type of mutation. The ABC2 Transporters of four groups of T.evansi have high similarity to ABC Transporters of T. brucei gambiense, T. brucei brucei, and T. brucei brucei (Tbabc2). Therefore, further research on the ABC2 Transporter gene is needed.

A meta-analysis of the prevalence of bovine trypanosomiasis in some African countries from 2000 to 2018

Bovine trypanosomiasis is a disease of cattle. In sub-Saharan Africa, the disease mean prevalence estimates are unknown in most endemic countries. We therefore performed a meta-analysis with the aim of estimating national mean prevalence of bovine trypanosomiasis in endemic countries across sub-Saharan Africa. Relevant articles reporting bovine trypanosomiasis prevalence were retrieved through systematic literature search and scanning of articles reference-lists. Eligibility criteria included that articles reported sample size, prevalence, and diagnostic technique adopted. Overall, data from 180 eligible articles from 19 countries satisfied the inclusion criteria. Meta-analysis of prevalence data based on the random-effects model resulted in an overall mean prevalence of 15.10% (95% CI: 13.22-17.08). National prevalence estimates were generally high except those of Benin and Senegal where estimates ranked below 10.00%. Significant heterogeneity (I² = 98.75%. p = <0.0001) was noted between studies, and univariate meta-regression analysis identified choice of diagnostic method being major contributor to observed heterogeneity (R² = 36.37%); while country of study (R² = 9.57%) and sample size (R² = 3.47%) had marginal effect on heterogeneity. In spite of past and ongoing control activities, bovine trypanosomiasis remains highly prevalent in most endemic sub-Saharan African countries. Nevertheless, dearth of epidemiological data in some countries and the use of less sensitive diagnostic tools limit reliable estimation of the disease prevalence. Therefore, there is the need to intensify efforts in aspects of surveillance and increased application of molecular diagnostic tool(s) across endemic locations as this would raise the chances of achieving a near-accurate estimate of the disease prevalence which is the first step to attempting eradication.

Impact of an integrated control campaign on tsetse populations in Burkina Faso

BACKGROUND

Tsetse flies are the sole vectors of human and animal trypanosomosis. In Burkina Faso, a project aiming to create zones free of tsetse flies and trypanosomosis was executed from June 2006 to December 2013. After the determination of tsetse distribution in the intervention area from December 2007 to November 2008, the control campaign was launched in November 2009 and ended in December 2013. The goal was to eliminate tsetse flies from 40,000 km2 of area, through an integrated control campaign including insecticide targets, traps and cattle, sequential aerial treatment (SAT) and the mass treatment of livestock using trypanocides. The campaign involved assistance of the beneficiary communities at all the steps of the control strategy with insecticide impregnated targets.

METHODS

This study was carried out to assess the impact of the control project on tsetse apparent density per trap per day (ADT). To evaluate the effectiveness of tsetse control, 201 sites were selected based on the baseline survey results carried out from December 2007 to November 2008. These sites were monitored bi-monthly from January 2010 to November 2012. At the end-of-study in 2013 a generalized entomological survey was carried out in 401 infested sites found during the longitudinal survey done before the control. Barrier and tsetse persistence areas were treated by ground spraying and evaluated. Controls were also done before and after aerial spraying.

RESULTS

In the insecticide-impregnated target area, the control showed that ADT of tsetse flies declined from 10.73 (SD 13.27) to 0.43 (SD 2.51) fly/trap/day from the third month of campaign onwards (P < 0.0001) and remained low thereafter. At the end of the campaign in 2013, an 83% reduction of ADT was observed for Glossina palpalis gambiensis and a 92% reduction for G. tachinoides. Tsetse flies were captured only in 29% of the sites found infested in 2008.

CONCLUSIONS

Tsetse flies could be suppressed efficiently but their elimination from the targeted area may require the use integrated methods including the Sterile Insect Technique, which is programmed through the development of the Pan African Tsetse and Trypanosomiasis Eradication Campaign (PATTEC Burkina) insectarium. The challenge will remain the sustainability of the achievement.

Haematology of N'Dama and West African Shorthorn cattle herds under natural Trypanosoma vivax challenge in Ghana

Background: Animal trypanosomosis is a major cause of economic loss in livestock production in Africa. A suggested control measure is to use breeds with traits of trypanotolerance. The study examines the effect of natural Trypanosoma vivax challenge on haematological parameters in two trypanotolerant cattle [N’Dama and West African Shorthorn (WASH)] herds.

Methods: Trypanosoma vivax-specific primers were used to diagnose T. vivax infection in an N’Dama herd at Cape Coast in southern Ghana and a WASH herd at Chegbani in northern Ghana from May to July 2011 in a cross-sectional study. Levels of haematological parameters comprising packed cell volume (PCV), haemoglobin (Hb) concentration and red blood cell (RBC) and total white blood cell (TWBC) counts; differential WBC counts (neutrophils, lymphocytes, eosinophils, monocytes and basophils); and RBC indices of mean corpuscular volume (MCV), mean corpuscular haemoglobin (MCH) and mean corpuscular haemoglobin concentration (MCHC) were determined in blood samples and then compared between infected and uninfected cattle.

Results: We found that haematological indices for infected and uninfected animals in both breeds were within the normal range. However, the mean PCV values for T. vivax-infected WASH and N’Dama were lower in infected compared to uninfected animals. The difference was significant ( p< 0.05) in N’Dama but not in WASH.

Conclusion: Despite the presence of infection by T. vivax, N’Dama and WASH cattle maintained their haematological parameters within acceptable normal ranges,  which confirms their trypanotolerant trait. This highlights the need for low-input traditional African farmers in medium, high and severe tsetse challenge areas to be educated on the advantages of N’Dama and WASH breeds to increase their utilization in integrated tsetse and trypanosomosis control programmes.

Genomic analysis of Isometamidium Chloride resistance in Trypanosoma congolense

Isometamidium Chloride (ISM) is one of the principal drugs used to counteract Trypanosoma congolense infection in livestock, both as a prophylactic as well as a curative treatment. However, numerous cases of ISM resistance have been reported in different African regions, representing a significant constraint in the battle against Animal African Trypanosomiasis. In order to identify genetic signatures associated with ISM resistance in T. congolense, the sensitive strain MSOROM7 was selected for induction of ISM resistance in a murine host. Administered ISM concentrations in immune-suppressed mice were gradually increased from 0.001 mg/kg to 1 mg/kg, the maximal dose used in livestock. As a result, three independent MSOROM7 lines acquired full resistance to this concentration after five months of induction, and retained this full resistant phenotype following a six months period without drug pressure. In contrast, parasites did not acquire ISM resistance in immune-competent animals, even after more than two years under ISM pressure, suggesting that the development of full ISM resistance is strongly enhanced when the host immune response is compromised. Genomic analyses comparing the ISM resistant lines with the parental sensitive line identified shifts in read depth at heterozygous loci in genes coding for different transporters and transmembrane products, and several of these shifts were also found within natural ISM resistant isolates. These findings suggested that the transport and accumulation of ISM inside the resistant parasites may be modified, which was confirmed by flow cytometry and ex vivo ISM uptake assays that showed a decrease in the accumulation of ISM in the resistant parasites.

In Vitro, Ex Vivo, and In Vivo Activities of Diamidines against Trypanosoma congolense and Trypanosoma vivax

African animal trypanosomosis (AAT) is caused by the tsetse fly-transmitted protozoans Trypanosoma congolense and T. vivax and leads to huge agricultural losses throughout sub-Saharan Africa. Three drugs are available to treat nagana in cattle (diminazene diaceturate, homidium chloride, and isometamidium chloride). With increasing reports of drug-resistant populations, new molecules should be investigated as potential candidates to combat nagana. Dicationic compounds have been demonstrated to have excellent efficacy against different kinetoplastid parasites. This study therefore evaluated the activities of 37 diamidines, using in vitro and ex vivo drug sensitivity assays. The 50% inhibitory concentrations obtained ranged from 0.007 to 0.562 μg/ml for T. congolense and from 0.019 to 0.607 μg/ml for T. vivax On the basis of these promising results, 33 of these diamidines were further examined using in vivo mouse models of infection. Minimal curative doses of 1.25 mg/kg of body weight for both T. congolense- and T. vivax-infected mice were seen when the diamidines were administered intraperitoneally (i.p.) over 4 consecutive days. From these observations, 15 of these 33 diamidines were then further tested in vivo, using a single bolus dose for administration. The total cure of mice infected with T. congolense and T. vivax was seen with single i.p. doses of 5 and 2.5 mg/kg, respectively. This study identified a selection of diamidines which could be considered lead compounds for the treatment of nagana.

Prevalence of bovine trypanosomosis and assessment of trypanocidal drug resistance in tsetse infested and non-tsetse infested areas of Northwest Ethiopia

The Northwestern region of Ethiopia is affected by both tsetse and non-tsetse transmitted trypanosomosis with a significant impact on livestock productivity. The control of trypanosomosis in Ethiopia relies on either curative or prophylactic treatment of animals with diminazene aceturate (DA) or isometamidium chloride (ISM). In the present work; questionnaire survey, cross-sectional and experimental studies were carried out to; a) assess the utilization of trypanocidal drugs; b) determine the prevalence of bovine trypanosomosis and; c) assess the drug resistant problems respectively in Tsetse and non-tsetse infested areas on NW Ethiopia. A total of 100 respondents were included for the survey and the questionnaires focused on the drug utilization practices for the control of Trypanosomosis. Blood from cattle 640 (324 cattle tested in 2011, 316 cattle tested in 2012) and 795 (390 cattle tested in 2011, 405 cattle tested in 2012) were examined from tsetse infested and non-tsetse infested areas respectively using the buffy coat technique and thin blood smear for the detection of trypanosomes and measurement of packed cell volume (PCV). For the assessment of trypanocidal drug resistance three isolates, one from tsetse (TT) and two from non-tsetse (NT) areas were used on thirty six trypanosome naïve calves. The experimental animals were divided randomly into six groups of six animals (TT-ETBS2-DA, TT-ETBS2-ISM, NT-ETBD2-DA, NT-ETBD2-ISM, NT-ETBD3-DA and NT-ETBD3-ISM), which were infected with T. vivax isolated from a tsetse-infested or non-tsetse infested area with 2 × 10⁶ trypanosomes from donor animals, and in each case treated with higher dose of DA or ISM. The results of the questionnaire survey showed trypanosomosis was a significant animal health constraint for 84% and 100% of the farmers questioned in non-tsetse and tsetse infested areas of Northwest Ethiopia respectively. Responses on trypanocidal drug utilization practices indicated that risk factors for the development of drug resistance are common and treatment failures are frequently seen. Accordingly, the majority of farmers in tsetse infested area get trypanocides from drug stores and unauthorized sources whereas those from non-tsetse area get from veterinary clinics. Moreover, treatment administration is mainly by animal health personnel and treatment frequency is a maximum of three times/year/animal in non-tsetse area whereas it is administered mainly by the farmers more than seven times/year/animal in tsetse infested area. The prevalence of trypanosomosis varied from 17.59% in 2011 to 25.0% in 2012 in tsetse infested areas with a significant (P = 0.023) difference. Similarly, in non-tsetse infested area the prevalence was varied from 3.85% in 2011 to 5.93% in 2012 without significant rise. Trypanosoma congolense (75%) was the most prevalent followed by T. vivax (20.58%) and mixed infections (4.41%) in tsetse infested area while in non-tsetse infested area only T. vivax was detected. The overall mean PCV in parasitaemic animals (20 ± 2.3 SD) was significantly (P < 0.001) lower than that of aparasitaemic animals (27 ± 4.3 SD). The assessment of trypanocidal drug resistance tests revealed one isolate of non-tsetse infested area against DA in group NT-ETBD2-DA is resistant to the higher dose used with 3 relapsing animals (50% relapses) in the group. Another two relapses were detected one against ISM for the isolate from tsetse infested area (TT-ETBS2-ISM) and one against DA for another isolate (NT-ETBD3-DA) from the non-tsetse area. In conclusion, trypanosomosis is widely prevalent in both study areas causing significant reduction in the mean PCV values. Farmers' trypanocidal utilization practices appear to pose risks of drug resistance problems. The in vivo drug resistance tests indicated the presence of resistant parasites with the higher dose against DA for NT-ETBD2 isolate and suspected resistance problems were detected against ISM and DA for TT-ETBS2 and NT-ETBD3 isolates respectively. Therefore, trypanosomosis is a major constraint in Northwest Ethiopia and drug resistance is a threat in the control of trypanosomosis in both study areas.

Cattle breeding, trypanosomosis prevalence and drug resistance in Northern Togo

African Animal Trypanosomosis (AAT) is a major disease of cattle in Togo and its control is essentially based on chemotherapy. However, because of excessive use of trypanocides during the past decades, chemo-resistance in the parasites has developed. In order to assess the current situation of AAT and resistance to trypanocidal drugs in Northern Togo, a study was conducted on cattle from December 2012 to August 2013 in the regions of Kara and Savanes. An initial cross-sectional survey was carried out in 40 villages using the Haematocrit Centrifugation Technique (HCT). Out of these, 5 villages with a trypanosome prevalence of >10% were selected for a block treatment study (BT) with diminazene diaceturate (DA: 3.5mg/kg for a 14-day follow-up) and isometamidium chloride (ISM: 0.5mg/kg for a 28-day follow-up). Positive blood samples collected during the parasitological surveys and an equivalent number of negatives were further analyzed by PCR-RFLP for trypanosome species confirmation and molecular diagnosis of resistance to DA in Trypanosoma congolense. The results from 1883 bovine blood samples confirmed a high overall trypanosome prevalence of 10.8% in Northern Togo. PCR-RFLP revealed that T. congolense is the dominant pathogenic trypanosome species (50.5%) followed by T. vivax (27.3%), and T. brucei (16.2%). The BT showed varying levels of treatment failures ranging from 0 to 30% and from 0 to 50% for DA and for ISM respectively, suggesting the existence of resistant trypanosome populations in the study area. Our results show that AAT still represents a major obstacle to the development of cattle husbandry in Northern Togo. In areas of high AAT risk, a community-based integrated strategy combining vector control, rational use of trypanocidal drugs and improving the general condition of the animals is recommended to decision makers.

In vivo experimental drug resistance study in Trypanosoma vivax isolates from tsetse infested and non-tsetse infested areas of Northwest Ethiopia

Ethiopia, particularly in the Northwest region, is affected by both tsetse fly and non-tsetse fly transmitted trypanosomosis with a significant impact on livestock productivity. The control of trypanosomosis in Ethiopia relies on either curative or prophylactic treatment of animals with diminazene aceturate (DA) or isometamidium chloride (ISM), respectively. However, since these two trypanocides have been on the market for more than 40 years, this may have resulted in drug-resistance. Therefore, in vivo drug resistance tests on two Ethiopian isolates of Trypanosoma vivax were completed, one from an area where tsetse flies are present and one from an area where tsetse flies are not present. Twenty four cattle (Bos indicus) aged between 6 and 12 months, purchased from a trypanosome-free area (Debre Brehan: Northcentral Ethiopia) and confirmed to be trypanosome-negative, were randomly assigned into four groups of six animals, which were infected with T. vivax isolated from a tsetse-infested or non-tsetse infested area, and in each case treated with curative doses of DA or ISM. Each animal were inoculated intravenously 3×10(6) trypanosomes from donor animals. Parasitaemia became patent earlier in infections with non-tsetse T. vivax (∼7 days post-infection) than tsetse (∼14 days post-infection). Both groups were treated at the highest peak parasitaemia with DA or ISM and nine cattle, four with non-tsetse T. vivax (two ISM- and two DA-treated) and five with tsetse T. vivax (three ISM- and two DA-treated) showed relapses of parasitaemia. Moreover, treatment did not improve diagnostic host markers of trypanosome infections in these animals. In conclusion, in vivo drug tests indicated the presence of resistant parasites (>20% of treated animals in each group relapsed) against recommended doses of both available trypanocidal drugs.

Erythrophagocytosis of desialylated red blood cells is responsible for anaemia during Trypanosoma vivax infection

Trypanosomal infection-induced anaemia is a devastating scourge for cattle in widespread regions. Although Trypanosoma vivax is considered as one of the most important parasites regarding economic impact in Africa and South America, very few in-depth studies have been conducted due to the difficulty of manipulating this parasite. Several hypotheses were proposed to explain trypanosome induced-anaemia but mechanisms have not yet been elucidated. Here, we characterized a multigenic family of trans-sialidases in T. vivax, some of which are released into the host serum during infection. These enzymes are able to trigger erythrophagocytosis by desialylating the major surface erythrocytes sialoglycoproteins, the glycophorins. Using an ex vivo assay to quantify erythrophagocytosis throughout infection, we showed that erythrocyte desialylation alone results in significant levels of anaemia during the acute phase of the disease. Characterization of virulence factors such as the trans-sialidases is vital to develop a control strategy against the disease or parasite.