Polymerase chain reaction and DNA probe hybridization to assess the efficacy of diminazene treatment in Trypanosoma brucei-infected cattle

First report of Trypanosoma vivax infection in sheep from Nicaragua

In Central America, outbreaks of trypanosomiasis by Trypanosoma vivax have been recorded only in cattle. This is the first report of an outbreak of trypanosomiasis by T. vivax in 30 Pelibuey sheep (2 to 7 years old, male and female) from Nicaragua, which occurred in 2009. Clinical signs included fever, apathy, pale mucous membranes, weakness, progressive weight loss, and sudden death. Infection by T. vivax was detected in 22 (73.3%) sheep by blood smear analysis and/or PCR. Trypanosomes were morphologically identified in 11 (36.7%) blood smear samples, whereas 17 (85%) of the 20 samples subjected to PCR were positive for T. vivax. Eighteen (81.8%) of the 22 infected sheep presented a packed red cell volume (PCV) lower than 25%. Upon diagnosis, the treated animals were clinically recovered and no parasites could be observed in subsequent examinations. Tabanids were potential mechanical vectors of T. vivax in the farm. This is the first report of T. vivax in Nicaragua and for the first time this haemoparasite is recorded in sheep in Central America.

Response of Three Nigerian Breeds of Sheep Experimentally Infected with Trypanosoma vivax to Diminazene Aceturate Therapy

The efficacy of diminazene aceturate in three Nigerian breeds of sheep [West African Dwarf (WAD), Yankassa and Ouda] experimentally infected with Trypanosoma vivax was studied. Five rams of each breed were administered 0.5 ml of goat blood containing 2.5 × 106 T. vivax per millilitre intravenously, while three rams of each breed served as uninfected controls. The treatment with diminazene aceturate was intramuscularly administered to the infected sheep, when their packed cell volume (PCV) fell to 15 %, at a dosage of 7 mg.kg−1 b. w. The parameters measured were parasitaemia, live weight gain and PCV. By 24 hours post treatment (pt.), no trypanosomes were detected by either the Haematocrit Concentration Technique (HCT) or the Polymerase Chain Reaction (PCR) in the blood of any of the treated sheep. However, a relapse of parasitaemia occurred 17 to 32 days pt. in 46.7 % of the treated rams and these were retreated with 14 mg.kg−1 b. w. diminazene aceturate. There were gradual increments in the live weight gain and the PCV of the treated rams until the resurgence of parasitaemia. Ouda had the highest cases of relapse (80 %), the least mean live weight gain and was the only breed in which mortality was recorded despite the treatment. In conclusion, diminazene aceturate administered at 7 mg.kg−1 b. w. cleared the trypanosomes in the blood of all the treated sheep within 24 hours and this was accompanied by the restoration of lost weight and the reversal of anaemia. However, the subsequent resurgence of parasitaemia indicated that a dosage of 7 mg.kg−1 b. w. was no longer reliable for complete elimination of trypanosomes from all the tissues of the host.

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.

Sustaining Efforts of Controlling Zoonotic Sleeping Sickness in Uganda Using Trypanocidal Treatment and Spray of Cattle with Deltamethrin

In 2005, the zoonotic acute sleeping sickness was spreading rapidly from the endemic areas of southeastern Uganda with potential for merger into areas affected by the chronic form of the disease in northwest Uganda. Movement of cattle reservoirs due to restocking was blamed for the rapid spread. To stop the spread of the zoonotic sleeping sickness, cattle in the disease endemic areas had to be treated with trypanocidal drugs and sprayed with deltamethrin to promote the live bait technology that helps suppress the tsetse vector. The initiative that started in five high-risk districts in 2006 with a mix of using several undergraduate veterinary students has now been integrated in the local government veterinary service delivery in 23 high-risk districts. By 2016, the annual spray of cattle with deltamethrin and treatment with diminazene aceturate had reached one million with 1,065,444 cattle sprayed in the reporting year July 1, 2016 to June 30, 2017. This is believed to have contributed significantly to the reduction in the number of Trypanosoma brucei rhodesiense sleeping sickness cases (from 473 recorded in 2005 to 14 in 2016, and only about 10 reported to the Coordinating Office for Control of Trypanosomiasis in Uganda [COCTU] in 2017). The initiative that started as the Stamp Out Sleeping Sickness Consortium with a public good approach, implemented in a public-private partnership with the faculty of Veterinary Medicine, Makerere University, has today been integrated in both private and public sectors to fast-track the elimination of T. b. rhodesiense sleeping sickness with active financial contribution from the affected communities in sustaining the delivery of live bait technology.

Experiences with an in-training community service model in the control of zoonotic sleeping sickness in Uganda

By 2006, the acute and zoonotic Tripanosoma brucei rhodesiense sleeping sickness in Uganda was spreading northward, leading to fear of a merger with the chronic Tripanosoma brucei gambiese type that affects people in the northwest of the country. Eliminating infection in cattle was urgent because they had been confirmed to be spreading the zoonotic type, and eliminating infection would reduce the animal reservoir and subsequently reduce transmission of sleeping sickness. In this article, we describe how the staff and students of the Faculty of Veterinary Medicine, Makerere University, adjusted their approach to training veterinary students who could provide the urgently needed manpower to enable the community to halt the disease's spread. Because it was not usual for university staff and students to implement disease control activities, the government of Uganda had to delegate this responsibility to Makerere University. In turn, the university had to explore available opportunities in its training and outreach mandates. A model was developed that proved to be an effective hands-on training strategy while helping to control a disease that was threatening the health of people in a community that was just recovering from an armed rebellion. In total, 66 students and supervisors participated in the 10-week-long mass treatment activities in the target area and treated more than 190,000 out of 220,000 targeted (>86%) cattle with diminazene aceturate and deltamethrin. Also, the graduates' performance improved, as indicated by 43.5% of graduates securing employment within less than a month after completing the course.

The Application of DNA-Biosensors and Differential Scanning Calorimetry to the Study of the DNA-Binding Agent Berenil

The in situ DNA-damaging capacity of berenil (1) has been investigated usingan electrochemical approach employing double stranded (ds) DNA-modified glassy carbonelectrode biosensors. Electrochemical voltammetric sensing of damage caused by 1 todsDNA was monitored by the appearance of peaks diagnostic of the oxidation of guanineand adenine. When 1 was incorporated directly onto the biosensor surface, DNA damagecould be observed at concentrations of additive as low as 10 μM. In contrast, when thedsDNA-modified biosensor was exposed to 1, in acetate buffer solution, the method wasmuch less sensitive and DNA damage could be detected only in the presence of 100 μMberenil. When mixed solutions of 1 and single stranded (ss) DNA, polyguanylic acid orpolyadenylic acid were submitted to voltammetric study, the oxidation signals of therespective bases decreased in a concentration-dependent manner and the major variation ofthe adenine current peak indicated preferential binding of 1 to adenine. The electrochemical results were in close agreement with those deriving from a differentialscanning calorimetric study of the DNA-berenil complex.

Epidemiological studies on tick-borne diseases of cattle in Central Equatoria State, Southern Sudan

A herd-based study was carried out in Central Equatoria State, Southern Sudan, to study epidemiological aspects of tick-borne diseases. Six herds of cattle situated in three different locations were selected and investigated every 3 months during the year 2005. Blood smears for Giemsa staining and blood spots on filter paper for deoxyribonucleic acid extraction were collected from 600 apparently healthy indigenous cattle. A total of 69 (11.5%) samples showed the presence of piroplasms in Giemsa-stained blood smears, and polymerase chain reaction increased the detection limit to 297 (49.5%). Using reverse line blot, it was possible to detect and differentiate eight different piroplasms namely, Theileria parva (71.2%), Theileria mutans (73%), Theileria velifera (45.3%), Theileria taurotragi (2.7%), Theileria buffeli (0.5%), Theileria annulata (0.2%), Babesia bovis (1.7%), and Babesia bigemina (0.3%). Mixed infections were detected in 406 samples (67.7%) accounting for 17 different combinations. High infection of Theileria parva was reported among young calves compared to older cattle. The highest prevalence of Theileria parva was reported in the rainy season (October). The implications of these results on the epidemiology of tick-borne diseases are discussed with emphasis on East Coast fever.

Comparing FAMACHA eye color chart and Hemoglobin Color Scale tests for detecting anemia and improving treatment of bovine trypanosomosis in West Africa

African animal trypanosomosis (AAT) is considered the most important cattle disease in sub-Saharan Africa but its diagnosis in the field is difficult, resulting in inappropriate treatments, excessive delay in treatments and under-treatment. A field study in West Africa investigated the usefulness of anemia in the diagnosis of trypanosomosis. A total of 20,772 cattle blood samples were taken from 121 villages in 3 countries. The average packed cell volume (PCV) of trypanosomosis positive cattle was 23%, versus 28% for negative cattle. In a sub-set of animals, other causes of anemia were investigated showing most of the anemia burden was attributable to trypanosomosis. Anemia was a reasonably accurate indicator of trypanosomosis in the study area, with a sensitivity of 56% and a specificity of 80% and a diagnostic odds ratio of 4.2, the highest of all the signs evaluated (anemia, emaciation, staring coat, lymphadenopathy, fever, lacrimation and salivary or nasal discharge). Having confirmed the usefulness of anemia as a predictor of trypanosomosis, two potential pen-side tests for anemia were evaluated (the first reported trial of their use in cattle), firstly a color chart developed for anemia detection in sheep through visual inspection of conjunctival membranes (FAMACHA) and secondly the Hemoglobin Color Scale (HbCS) developed for assessing hemoglobin levels in human patients by comparing blood drops on filter paper with color standards. In a population of cattle suspected by their owners to be sick with trypanosomosis (n=898) the sensitivity of the HbCS test was 56% and the specificity was 77%, while the sensitivity of the FAMACHA test was 95% and the specificity was 22%. The higher sensitivity but lower specificity suggests the FAMACHA may be useful as a screening test and the HbCS as a confirmatory test. The two tests were also evaluated in cattle randomly selected from the village herd. Using cut-off points to optimize test performance, the HbCS test had a sensitivity of 81% and a specificity of 62% (n=505 cattle), while the FAMACHA had a sensitivity of 92% and a specificity of 30% (n=298 cattle). Recommendations are made for the appropriate use of these tests in the West African region.

Trypanocidal failure suggested by PCR results in cattle field samples

The aim of this study was to assess, whether polymerase chain reaction (PCR) allows sensitive screening of treatment failure suspicions in areas, where drug resistance against African animal trypanosomosis (AAT) appears to be a problem. PCR was used to detect trypanosome infections prior to, 14 and 28 days after controlled treatment of 738 cattle from 10 villages in Kénédougou, Burkina Faso with isometamidium chloride and diminazene aceturate. Using three sets of primers, PCR was three-four times more sensitive and better at species identification, than standard microscopic examination. The better sensitivity and species specificity of PCR have important advantages for drug resistance studies in the field.

Bovine trypanosomiasis in south-western Uganda: packed-cell volumes and prevalences of infection in the cattle

Following confirmed cases of trypanosomiasis ('nagana') and reports of trypanosome-attributable deaths among local cattle, a cross-sectional study was undertaken to determine the prevalence of bovine infection with trypanosomes in south-western Uganda. Cattle from 10 different localities were checked by the microscopical examination of wet bloodsmears and thin, stained bloodsmears, and by blood centrifugation followed by the examination of the resultant buffy coats. Of the 1309 cattle investigated, 6.42% (5.56% and 7.26% of those from the Mbarara and Mubende districts, respectively) were found to be infected. Of the positive animals, 71 (84.5%), 11 (13.1%) and two (2.4%) appeared to be infected with Trypanosoma vivax only, T. congolense only and both T. vivax and T. congolense, respectively. The prevalence of infection with T. vivax was significantly higher than that with T. congolense (P<0.001). The mean packed-cell volumes (PCV) for the trypanosome-positive animals were lower than those for the trypanosome-negative, whether the cattle considered were all those investigated (22.3% v. 29.0%; P<0.001) or just those from the Mbarara (22.8% v. 28.2%) or Mubende (21.5% v. 29.7%) districts. South-western Uganda has been relatively free of both human and bovine trypanosomiasis for the past three decades. The factors leading to the current resurgence of bovine trypanosomiasis need further investigation.

Using PCR for unraveling the cryptic epizootiology of livestock trypanosomosis in the Pantanal, Brazil

Trypanosoma vivax and Trypanosoma evansi are livestock parasites of economic importance in Africa, Asia and South America. In the Pantanal, Brazil, they cause economic losses in both cattle and equines. Little is known of their maintenance and spread in nature, particularly in terms of reservoirs and means of mechanical transmission. Here we report for the first time the use of PCR for the detection of T. vivax and T. evansi in bovines, buffaloes and sheep. Whereas parasitological diagnosis detected only two T. vivax infections, one in buffalo and another in a cow, PCR detected infections in 34.8% buffaloes, 44.7% bovines and 37.3% sheep. Trypanozoon primers detected 41.8% infections in buffaloes and 8.1% in cattle. PCR revealed 6.9% mixed infections in buffaloes and 5.3% in cattle. The potential role of cattle and buffaloes as hosts and reservoirs of T. vivax is discussed, as well as the implications of possible extravascular foci in the maintenance of livestock trypanosomosis.

A field study to estimate the prevalence of Trypanosoma equiperdum in Mongolian horses

From May to July 2000, a cross-sectional study was conducted to estimate the prevalence of Trypanosoma equiperdum in the horse population of the central province (Tuv aimag) of Mongolia. On average, four herds were selected from each of the 29 aimag subdivisions (119 herds). From each herd, 10 horses were sampled in proportion to sex and age categories in the respective herds (1190 horses). Sera from 1122 horses were analysed for T. equiperdum antibodies using two serological assays, the complement fixation test (CFT) and the enzyme-linked immunosorbent assay (ELISA). The crude estimate of the CFT and the ELISA seroprevalence was 7.6 and 6.7%, respectively. Concordance between the CFT and ELISA results was high (96%). The highest number of CFT positive animals was detected in one herd in Möngönmorit (6/10), followed by herds in Bayandelger (5/10) and in Bayantsagaan (5/10). Poor body condition was significantly correlated with positive serological status in both CFT and ELISA. A history of abortion appeared to be a risk factor for both CFT and ELISA seropositivity. Blood samples of all horses belonging to herds with at least three (3/10) seropositive animals (CFT and/or ELISA) were analysed by light microscopy and by PCR using a Trypanosoma (Trypanozoon) brucei specific primer pair. No trypanosomes or any other haemoparasites could be detected in Giemsa stained thin blood smears. Eight out of the 130 samples (6.2%) analysed by PCR gave positive signals. Seven out of the eight PCR positive horses were also serologically positive. One PCR (and ELISA) positive stallion from Möngönmorit showed emaciation, scrotal and preputial oedema and an oedematous skin plaque. From the serological and DNA-based results it is concluded, that trypanosome infections occur in horses in the Tuv aimag of Mongolia. Since at present neither serological nor DNA-based tests allow a subspecies specific identification within the subgenus Trypanozoon, no definitive diagnosis can be given for T. equiperdum. Whether the examined herds are infected with T. equiperdum or with T. evansi, the causative agent of surra, remains an open question. However, based on the clinical findings, the negative parasitological results and the concentration of conspicuous seroprevalences in single herds, circumstantial evidence supports the existence of infections with the causative agent of dourine.

Applications of PCR-based tools for detection and identification of animal trypanosomes: a review and perspectives

This paper aims to review the applications of the polymerase chain reaction (PCR) for the detection and identification of trypanosomes in animals. The diagnosis of trypanosomes, initially based on microscopic observations and the host range of the parasites, has been improved, since the 1980s, by DNA-based identification. These diagnostic techniques evolved successively through DNA probing, PCR associated to DNA probing, and currently to PCR alone. Several DNA sequences have been investigated as possible targets for diagnosis, especially multi-copy genes such as mini-exon, kinetoplastid mini-circles, etc., but the most favoured target is the nuclear satellite DNA of mini-chromosomes, which presents the advantages, and the drawbacks, of highly repetitive short sequences (120-600 bp). Several levels of specificity have been achieved from sub-genus to species, sub-species and even types. Random priming of trypanosome DNA has even allowed "isolate specific" identification. Other work based on microsatellite sequences has provided markers for population genetic studies. For regular diagnosis, the sensitivity of PCR has increased with the advancement of technologies for sample preparation, to reach a level of 1 trypanosome/ml of blood, which has brought to field samples a sensitivity two to three times higher than microscopic observation of the buffy coat. Similarly, PCR has allowed an increase in the specificity and sensitivity of diagnosis in vectors such as tsetse flies. However, because of the diversity of Trypanosoma species potentially present in a single host, PCR diagnosis carried out on host material requires several PCR reactions; for example, in cattle, up to five reactions per sample may be required. Research is now focusing on a diagnosis based on the amplification of the internal transcribed spacer-1 (ITS-1) of ribosomal DNA which presents the advantages of being a multi-copy locus (100-200), having a small size (300-800 bp), which varies from one taxon to another but is conserved in size in a given taxon. This may lead to the development of a multi-species-specific diagnostic protocol using a single PCR. By reducing the cost of the PCR diagnosis, this technique would allow a greater number of field samples to be tested in epidemiological studies and/or would increase the variety of Trypanosoma species that could be detected. Further investigations are required to develop and optimise multi-species-specific diagnostic tools for trypanosomes, which could also serve as a model for such tools in other pathogens.

Heterogeneous DNA binding modes of berenil

Isothermal titration calorimetry (ITC) profiles of berenil bound to different DNAs show that, despite the strong preference of berenil for AT-rich regions in DNA, it can bind to other DNA sequences significantly. The ITC results were used to quantify the binding of berenil, and the thermodynamic profiles were obtained using natural DNAs as well as synthetic polynucleotides. ITC binding isotherms cannot be simply described when a single set of identical binding sites is considered, except for poly[d(A-T)2]. Ultraviolet melting of DNA and differential scanning calorimetry were also used to quantify several aspects of the binding of berenil to salmon testes DNA. We present evidence for secondary binding sites for berenil in DNA, corresponding to G+C rich sites. Berenil binding to poly[d(G-C)2] is also observed. Circular dichroism experiments showed that binding to GC-rich sites involves drug intercalation. Using a molecular modeling approach we demonstrate that intercalation of berenil into CpG steps is sterically feasible.

A comparative evaluation of parasitological tests and a PCR for Trypanosoma evansi diagnosis in experimentally infected water buffaloes

In this study five parasitological methods and a polymerase chain reaction (PCR) were compared for the diagnostic sensitivity for Trypanosoma evansi in experimentally infected water buffaloes over a period of 15 weeks. The combined estimates of sensitivity (CE(se)) of the PCR proved to be highest at 78.2%, closely followed by the mouse inoculation (MI), the micro-haematocrite centrifugation technique (MHCT) and the mini-anion-exchange centrifugation technique (MAECT) with CE(se) of, respectively, 74.0, 69.6 and 62.4%. The CE(se) of the buffy-coat technique (BCT) at 38.6% and the sodium dodecyl sulfate (SDS) clarification technique at 25.1% were considerably lower. PCR detected consistently all buffaloes infected from week 3 post-infection (PI) onwards. For MI this occurred after 5 weeks PI while for MHCT and MAECT these sustainable high levels were reached in the 7th week PI. BCT and SDS never detected all buffaloes infected. The influence of time and temperature on the viability of T. evansi in heparinized blood from water buffalo was also studied. In general we observed that the survival time tends to be longer when blood is kept at 4 degrees C. In samples kept in direct sunlight parasites became undetectable with the MHCT after 30min. After treatment of the water buffaloes with diminazene aceturate, the PCR signal disappeared within 24h.

Validation of a polymerase chain reaction assay for monitoring the therapeutic efficacy of diminazene aceturate in trypanosome-infected sheep

The diagnostic performance of a polymerase chain reaction assay (PCR) for monitoring the effectiveness of aceturate diminazene treatment was compared with those of an antibody-detection ELISA test and the buffy-coat technique using sheep experimentally infected with either savannah-type or forest-type Trypanosoma congolense or T. vivax. Within the period of infection, the PCR using specific savannah-type T. congolense primers showed a significant higher diagnostic sensitivity (p<0.05) than the buffy-coat technique. Both techniques gave closed results for detecting forest-type T. congolense or T. vivax infections. Following trypanocidal treatment, the PCR showed that specific product disappeared definitively 1 or 2 days later in animals in which a decrease of the antibody level and a significant improvement of the red packed cell volume were observed. The occurrence of relapse infection was detected by the PCR in one animal infected by T. vivax on day 19 post-treatment and confirmed by the persistence and increasing antibody level whereas the buffy-coat technique detected parasites 42 days later. Then, the PCR signals remained positive on several occasions while parasitaemia was detected only two times.The application of PCR combined with the antibody detection appeared to provide a useful tool as compared to the buffy-coat technique for monitoring the effectiveness of trypanocidal treatment.