The use of the acridine orange QBC technique in the diagnosis of African trypanosomiasis

Evaluation of ITS1 rDNA primers for the detection and identification of African trypanosomes in mammalian hosts and tsetse flies

Although several primers targeted to the internal transcribed-spacer 1 (ITS1) of the ribosomal DNA (rDNA) have been designed to improve the detection of African trypanosomes, no study tried to compare their agreement level and ability to amplify different trypanosome species in tsetse flies and mammals in various epidemiological settings. This study was designed to fill this gap, by targeting tsetse-infested areas of Cameroon. For this, archived DNA samples reporting at-least one trypanosome species with species-specific PCR primers were reviewed. Ten sets of primers targeting different ITS1 rDNA sequences of trypanosomes were selected for assessment using single-round and nested-PCR method. Amplification rates (sensitivity) and agreement level of different ITS1 assays were compared using Cohen's-Kappa and McNemar's x2 statistic. Little agreement level (k = 0.05-0.52) were observed between different ITS1-primers PCRs detection of African trypanosome species despite significant (X2=54.3, p = 0.0001) high amplification rate 91.6 % (339/370). This sensitivity varied from quite low for T. simiae (11.9 %) and T. vivax (27.3 %) to fairly good for T. congolence (51.9 %), Trypanozoon (32.4 %) and T. theileri (40.3 %). Primers set targeting ITS1-A sequence of trypanosome species recorded the highest sensitivity (50.5 %) with fairly good agreement compared to 39.2 % for ITS1-C (k = 0.52), 32.4 % for ITS1-R (k = 0.47), 29.7 % for ITS1-N (k = 0.48) and 23.0 % for ITS1-KIN (k = 0.43) respectively. This study revealed a diversity in the sensitivity of different trypanosome species with different sets of ITS-primers enhancing the need to use the same sets of primers in different bio-ecological settings. The use of nested-PCR instead of single-round PCR enabled improvement of trypanosome infections detection in both tsetse and mammals. Among the sets of ITS1-primers tested, those designed by to amplify ITS1-A can be considered as the most appropriate for the detection of trypanosome infections in mammals and tsetse flies.

The fully automated Sysmex XN-31 hematology analyzer can detect bloodstream form Trypanosoma brucei

BACKGROUND

For fully automated detection and quantification of Plasmodium parasites, Sysmex developed the XN-31 hemocytometer. This study investigated whether the XN-31 can also detect and quantify bloodstream form trypanosomes (trypomastigotes).

METHODS

Axenic cultures of Trypanosoma brucei brucei were used to prepare two dilution series of trypomastigotes in the whole blood of a healthy donor, which were subsequently examined by the XN-31 as well as by microscopic examination of thin and thick blood films. Trypomastigote intactness during the procedures was evaluated by microscopy.

RESULTS

The XN-31 hemocytometer detected trypomastigotes with a detection limit of 26 trypomastigotes/μL. Scattergram patterns of Trypanosoma and Plasmodium parasites were clearly distinct, but current interpretation settings do not allow the identification of trypomastigotes yet, and therefore, need future refinement.

CONCLUSION

Proof of concept was provided for an automated fluorescent flow cytometry method that can detect and quantify Plasmodium spp., as well as Trypanosoma brucei trypomastigotes.

Pocket MUSE: an affordable, versatile and high-performance fluorescence microscope using a smartphone

Smartphone microscopes can be useful tools for a broad range of imaging applications. This manuscript demonstrates the first practical implementation of Microscopy with Ultraviolet Surface Excitation (MUSE) in a compact smartphone microscope called Pocket MUSE, resulting in a remarkably effective design. Fabricated with parts from consumer electronics that are readily available at low cost, the small optical module attaches directly over the rear lens in a smartphone. It enables high-quality multichannel fluorescence microscopy with submicron resolution over a 10× equivalent field of view. In addition to the novel optical configuration, Pocket MUSE is compatible with a series of simple, portable, and user-friendly sample preparation strategies that can be directly implemented for various microscopy applications for point-of-care diagnostics, at-home health monitoring, plant biology, STEM education, environmental studies, etc.

Identification of human African Trypanosomiasis foci using school-going children in post-conflict era in Nwoya District, Northern Uganda: A cross-sectional study

Background: Human African Trypanosomiasis (HAT) is fatal if untreated; the drugs to treat it are toxic making its management difficult and diagnosis complex. Nwoya district has a long history of sleeping-sickness dating back to pre-colonial times. The civil war of 1986-2008 displaced many who upon return complained of cattle and dogs dying of unknown causes alongside increased tsetse flies infestation hence, the needs for the study. Methods: We enrolled local 3,040 pupils and recorded their social-demographic characteristics and access to different domesticated animals/fowls in their homes. Screening for HAT using the card agglutination test for trypanosomiasis (CATT) was performed; positive individuals had their titres determined, followed by microscopy and loop mediated isothermal amplification analysis (LAMP). R was used for analysis where associations were sought between dependent and independent variables. Any factor with P-value <0.05 was taken as statistically significant. Results: HAT serological prevalence of 1.2% (95% CI 0.8-1.6) was obtained, 58.3% being boys while 41.7% were girls with titres ranging from 1:2 - 1:16. Two schools alone, constituted 47% of the CATT positive cases. Pupils who came from homes with dogs were more likely to be CATT/ Trypanosoma brucei gambiense positive; (adjusted odds ratio = 3.12, 95% CI 1.41-6.99 & p=0.005). Conclusions: Though no parasites were detected, with prevalence of CATT positive at 1.2%, active surveillance in the district is still recommended. CATT positive cases needs follow-ups were immune trypanolysis test done to ascertain their exposure.

Green fluorescent diamidines as diagnostic probes for trypanosomes

Light-emitting diode (LED) fluorescence microscopy offers potential benefits in the diagnosis of human African trypanosomiasis and in other aspects of diseases management, such as detection of drug-resistant strains. To advance such approaches, reliable and specific fluorescent markers to stain parasites in human fluids are needed. Here we describe a series of novel green fluorescent diamidines and their suitability as probes with which to stain trypanosomes.

Characterization ofTrypanosoma bruceis.l. infecting asymptomatic sleeping-sickness patients in Côte d'Ivoire: a new genetic group?

Six villagers in the Sinfra focus of sleeping sickness in Côte d'Ivoire who in 1995 were asymptomatic and refusing treatment, despite then being serologically and parasitologically positive for trypanosomes, were followed-up, while still refusing treatment, until 2002. In 2002, five of the six cases remained serologically positive but no trypanosomes could be found in any of them by use of the classical parasitological methods. A PCR-based assay, however, revealed that all six had the DNA of Trypanosoma brucei s.l. in their blood, so confirming the low sensitivity of the classical parasitological tests. The analysis of satellite, minisatellite and microsatellite markers indicated that, in 2002, all six cases were infected with a 'new' distinct genetic group of T. brucei s.l. and four were co-infected with T. b. gambiense group 1. The epidemiological consequences of such co-infections are discussed. The 'new' group of T. brucei had a molecular pattern that differed from those of the classical T. b. gambiense group 1 and the 'bouaflé' group.

Human African trypanosomiasis

Human African trypanosomiasis or sleeping sickness is a neglected tropical disease that affects populations in sub-Saharan Africa. The disease is caused by infection with the gambiense and rhodesiense subspecies of the extracellular parasite Trypanosoma brucei, and is transmitted to humans by bites of infected tsetse flies. The disease evolves in two stages, the hemolymphatic and meningoencephalitic stages, the latter being defined by central nervous system infection after trypanosomal traversal of the blood-brain barrier. African trypanosomiasis, which leads to severe neuroinflammation, is fatal without treatment, but the available drugs are toxic and complicated to administer. The choice of medication is determined by the infecting parasite subspecies and disease stage. Clinical features include a constellation of nonspecific symptoms and signs with evolving neurological and psychiatric alterations and characteristic sleep-wake disturbances. Because of the clinical profile variability and insidiously progressive central nervous system involvement, disease staging is currently based on cerebrospinal fluid examination, which is usually performed after the finding of trypanosomes in blood or other body fluids. No vaccine being available, control of human African trypanosomiasis relies on diagnosis and treatment of infected patients, assisted by vector control. Better diagnostic tools and safer, easy to use drugs are needed to facilitate elimination of the disease.

Human african trypanosomiasis diagnosis in first-line health services of endemic countries, a systematic review

While the incidence of Human African Trypanosomiasis (HAT) is decreasing, the control approach is shifting from active population screening by mobile teams to passive case detection in primary care centers. We conducted a systematic review of the literature between 1970 and 2011 to assess which diagnostic tools are most suitable for use in first-line health facilities in endemic countries. Our search retrieved 16 different screening and confirmation tests for HAT. The thermostable format of the Card Agglutination Test for Trypanosomiasis (CATT test) was the most appropriate screening test. Lateral flow antibody detection tests could become alternative screening tests in the near future. Confirmation of HAT diagnosis still depends on visualizing the parasite in direct microscopy. All other currently available confirmation tests are either technically too demanding and/or lack sensitivity and thus rather inappropriate for use at health center level. Novel applications of molecular tests may have potential for use at district hospital level.

The detection and treatment of human African trypanosomiasis

Human African trypanosomiasis (HAT) is caused by the injection of Trypanosoma brucei (T. b.) gambiense or T. b. rhodesiense by Glossina, the tsetse fly. Three historical eras followed the exclusive clinical approach of the 19th century. At the turn of the century, the "initial research" era was initiated because of the dramatic spread of HAT throughout intertropical Africa, and scientists discovered the agent and its vector. Two entities, recurrent fever and sleeping sickness, were then considered a continuum between hemolymphatic stage 1 and meningoencephalitic stage 2. Treatments were developed. Soon after World War I, specific services and mobile teams were created, initiating the "epidemiological" era, during which populations were visited, screened, and treated. As a result, by 1960, annual new cases were rare. New mass screening and staging tools were then developed in a third, "modern" era, especially to counter a new epidemic wave. Currently, diagnosis still relies on microscopic detection of trypanosomes without (wet and thick blood films) or with concentration techniques (capillary tube centrifugation, miniature anion-exchange centrifugation technique). Staging is a vital step. Stage 1 patients are treated on site with pentamidine or suramin. However, stage 2 patients are treated in specialized facilities, using drugs that are highly toxic and/or that require complex administration procedures (melarsoprol, eflornithine, or nifurtimox-eflornithine combination therapy). Suramin and melarsoprol are the only medications active against Rhodesian HAT. Staging still relies on cerebrospinal fluid examination for trypanosome detection and white blood cell counts: stage 1, absence of trypanosomes, white blood cell counts ≤ 5/µL; stage 2, presence of trypanosomes, white blood cell counts ≥ 20/µL; T. b. gambiense HAT intermediate stage, between these still controversial thresholds. Our group has proposed the use of noninvasive ambulatory polysomnography to identify sleep-wake abnormalities characteristic of stage 2 of the disease. Only patients with abnormal sleep-wake patterns would then undergo confirmative lumbar puncture.

Improved detection of Trypanosoma brucei by lysis of red blood cells, concentration and LED fluorescence microscopy

Confirmatory diagnosis of African trypanosomiasis relies on demonstration of parasites in body fluids by bright field microscopy. The parasitaemia in infected patients and animals is usually low, and concentration methods are used to try and increase the chances of seeing parasites. Recently, fluorescence microscopes using light-emitting diodes (LED) have been developed. Since they emit strong light, their use does not require a dark room, making field application a possibility. We have combined LED fluorescence microscopy with lysis of red blood cells (RBC) to improve the sensitivity and speed of detecting trypanosomes. In studies conducted at four centers in Uganda and the Democratic Republic of the Congo, parasitaemic blood was serially diluted and the RBCs lysed using commercial buffer. Samples were then concentrated by centrifugation, and different volumes of the sediment used to make thin and thick smears. Next, these were stained with acridine orange or Giemsa, and examined using an LED microscope under fluorescence or bright light, respectively. Detection of parasites was significantly improved by RBC lysis and concentration, regardless of the staining and microscopy method used. Further improvements were made when smears were prepared using larger volumes of sediment. The best results were obtained with thin smears prepared using 20 μl of sediment and stained with acridine orange. The time taken to see the first parasite was dramatically reduced when smears were examined by LED fluorescence microscopy, compared to bright light. LED fluorescence microscopy was found to be easier and requiring less visual effort than bright field microscopy. These studies demonstrate the potential for incremental improvement in detection of Trypanosoma brucei by combining LED fluorescence microscopy with RBC lysis and concentration. The lysis and concentration method may also be useful in sample preparation for other diagnostic tests for trypanosomiasis.

Accuracy of five algorithms to diagnose gambiense human African trypanosomiasis

Background

Algorithms to diagnose gambiense human African trypanosomiasis (HAT, sleeping sickness) are often complex due to the unsatisfactory sensitivity and/or specificity of available tests, and typically include a screening (serological), confirmation (parasitological) and staging component. There is insufficient evidence on the relative accuracy of these algorithms. This paper presents estimates of the accuracy of five algorithms used by past Médecins Sans Frontières programmes in the Republic of Congo, Southern Sudan and Uganda.

Methodology and Principal Findings

The sequence of tests in each algorithm was programmed into a probabilistic model, informed by distributions of the sensitivity, specificity and staging accuracy of each test, constructed based on a literature review. The accuracy of algorithms was estimated in a baseline scenario and in a worst-case scenario introducing various near worst-case assumptions. In the baseline scenario, sensitivity was estimated as 85–90% in all but one algorithm, with specificity above 99.9% except for the Republic of Congo, where CATT serology was used as independent confirmation test: here, positive predictive value (PPV) was estimated at <50% in realistic active screening prevalence scenarios. Furthermore, most algorithms misclassified about one third of true stage 1 cases as stage 2, and about 10% of true stage 2 cases as stage 1. In the worst-case scenario, sensitivity was 75–90% and PPV no more than 75% at 1% prevalence, with about half of stage 1 cases misclassified as stage 2.

Conclusions

Published evidence on the accuracy of widely used tests is scanty. Algorithms should carefully weigh the use of serology alone for confirmation, and could enhance sensitivity through serological suspect follow-up and repeat parasitology. Better evidence on the frequency of low-parasitaemia infections is needed. Simulation studies should guide the tailoring of algorithms to specific scenarios of HAT prevalence and availability of control tools.

Gambiense human African trypanosomiasis (HAT, sleeping sickness) usually features low prevalence. The two stages of the disease require different treatments, and stage 2 is fatal if untreated. HAT diagnosis must therefore be highly sensitive (i.e., detect as many true cases as possible) and specific (i.e., minimize false positives). HAT diagnostic algorithms are complex and involve several tests to screen for, confirm and stage infection. We analyzed five algorithms used by Médecins Sans Frontières HAT programmes. We combined published data on the accuracy of each test in the algorithm with a computer program that simulates all possible algorithm branches. We found that all algorithms had reasonable sensitivity (85–90%); specificity was high (>99.9%) except for the Republic of Congo, where confirmation did not rely on microscopic evidence, resulting in frequent false positives (but also higher sensitivity). Algorithms misclassified about one third of stage 1 cases as stage 2, but stage 2 classification was highly accurate. The use of serology alone for confirmation merits caution. HAT diagnosis could be made more sensitively by following up serological suspects and repeating microscopic examinations. Computer simulations can help to adapt algorithms to local conditions in each HAT programme, such as the prevalence of infection and operational constraints.

Nifurtimox-eflornithine combination therapy for second-stage African Trypanosoma brucei gambiense trypanosomiasis: a multicentre, randomised, phase III, non-inferiority trial

BACKGROUND

Human African trypanosomiasis (HAT; sleeping sickness) caused by Trypanosoma brucei gambiense is a fatal disease. Current treatment options for patients with second-stage disease are toxic, ineffective, or impractical. We assessed the efficacy and safety of nifurtimox-eflornithine combination therapy (NECT) for second-stage disease compared with the standard eflornithine regimen.

METHODS

A multicentre, randomised, open-label, active control, phase III, non-inferiority trial was done at four HAT treatment centres in the Republic of the Congo and the Democratic Republic of the Congo. Patients aged 15 years or older with confirmed second-stage T b gambiense infection were randomly assigned by computer-generated randomisation sequence to receive intravenous eflornithine (400 mg/kg per day, every 6 h; n=144) for 14 days or intravenous eflornithine (400 mg/kg per day, every 12 h) for 7 days with oral nifurtimox (15 mg/kg per day, every 8 h) for 10 days (NECT; n=143). The primary endpoint was cure (defined as absence of trypanosomes in body fluids and a leucocyte count </=20 cells per muL) 18 months after treatment. Efficacy analyses were done in the intention-to-treat (ITT), modified ITT, and per-protocol (PP) populations. The non-inferiority margin for the difference in cure rates was defined as 10%. This study is registered with ClinicalTrials.gov, number NCT00146627.

FINDINGS

One patient from the eflornithine group absconded after receiving the first dose, without any type of assessment done, and was excluded from all analyses. In the ITT population, 131 (91.6%) of 143 patients assigned to eflornithine and 138 (96.5%) of 143 patients assigned to NECT were cured at 18 months (difference -4.9%, one-sided 95% CI -0.3; p<0.0001). In the PP population, 122 (91.7%) of 133 patients in the eflornithine group and 129 (97.7%) of 132 in the NECT group were cured at 18 months (difference -6.0%, one-sided 95% CI -1.5; p<0.0001). Drug-related adverse events were frequent in both groups; 41 (28.7%) patients in the eflornithine group and 20 (14.0%) in the NECT group had major (grade 3 or 4) reactions, which resulted in temporary treatment interruption in nine and one patients, respectively. The most common major adverse events were fever (n=18), seizures (n=6), and infections (n=5) in the eflornithine group, and fever (n=7), seizures (n=6), and confusion (n=2) in the NECT group. There were four deaths, which were regarded as related to study drug (eflornithine, n=3; NECT, n=1).

INTERPRETATION

The efficacy of NECT is non-inferior to that of eflornithine monotherapy. Since this combination treatment also presents safety advantages, is easier to administer (ie, infusion every 12 h for 7 days vs every 6 h for 14 days), and potentially protective against the emergence of resistant parasites, it is suitable for first-line use in HAT control programmes.

FUNDING

Médecins Sans Frontières (Dutch section), Médecins Sans Frontières International, and the Drugs for Neglected Diseases Initiative.

Nucleic acid sequence-based amplification with oligochromatography for detection of Trypanosoma brucei in clinical samples

Molecular tools, such as real-time nucleic acid sequence-based amplification (NASBA) and PCR, have been developed to detect Trypanosoma brucei parasites in blood for the diagnosis of human African trypanosomiasis (HAT). Despite good sensitivity, these techniques are not implemented in HAT control programs due to the high cost of the equipment, which is unaffordable for laboratories in developing countries where HAT is endemic. In this study, a simplified technique, oligochromatography (OC), was developed for the detection of amplification products of T. brucei 18S rRNA by NASBA. The T. brucei NASBA-OC test has analytical sensitivities of 1 to 10 parasites/ml on nucleic acids extracted from parasite culture and 10 parasites/ml on spiked blood. The test showed no reaction with nontarget pathogens or with blood from healthy controls. Compared to the composite standard applied in the present study, i.e., parasitological confirmation of a HAT case by direct microscopy or by microscopy after concentration of parasites using either a microhematocrit centrifugation technique or a mini-anion-exchange centrifugation technique, NASBA-OC on blood samples had a sensitivity of 73.0% (95% confidence interval, 60 to 83%), while standard expert microscopy had a sensitivity of 57.1% (95% confidence interval, 44 to 69%). On cerebrospinal fluid samples, NASBA-OC had a sensitivity of 88.2% (95% confidence interval, 75 to 95%) and standard microscopy had a sensitivity of 86.2% (95% confidence interval, 64 to 88%). The T. brucei NASBA-OC test developed in this study can be employed in field laboratories, because it does not require a thermocycler; a simple heat block or a water bath maintained at two different temperatures is sufficient for amplification.

Safety and effectiveness of first line eflornithine for Trypanosoma brucei gambiense sleeping sickness in Sudan: cohort study

OBJECTIVE

To assess the safety and effectiveness of eflornithine as first line treatment for human African trypanosomiasis.

DESIGN

Cohort study.

SETTING

Control programme in Ibba, southern Sudan.

PARTICIPANTS

1055 adults and children newly diagnosed with second stage disease in a 16 month period.

MAIN OUTCOME MEASURES

Deaths, severe drug reactions, and cure at 24 months.

RESULTS

1055 patients received eflornithine for 14 days (400 mg/kg/day in adults and 600 mg/kg/day in a subgroup of 96 children). Overall, 2824 drug reactions (2.7 per patient) occurred during hospital stay, 1219 (43.2%) after the first week. Severe reactions affected 138 (13.1%) patients (mainly seizures, fever, diarrhoea, and bacterial infections), leading to 15 deaths. Risk factors for severe reactions included cerebrospinal fluid leucocyte counts > or =100x10(9)/l (adults: odds ratio 2.6, 95% confidence interval 1.5 to 4.6), seizures (adults: 5.9, 2.0 to 13.3), and stupor (children: 9.3, 2.5 to 34.2). Children receiving higher doses did not experience increased toxicity. Follow-up data were obtained for 924 (87.6%) patients at any follow-up but for only 533 (50.5%) at 24 months. Of 924 cases followed, 16 (1.7%) died during treatment, 70 (7.6%) relapsed, 15 (1.6%) died of disease, 403 (43.6%) were confirmed cured, and 420 (45.5%) were probably cured. The probability of event free survival at 24 months was 0.88 (0.86 to 0.91). Most (65.8%, 52/79) relapses and disease related deaths occurred after 12 months. Risk factors for relapse included being male (incidence rate ratio 2.42, 1.47 to 3.97) and cerebrospinal fluid leucocytosis: 20-99x10(9)/l (2.35, 1.36 to 4.06); > or =100x10(9)/l (1.87, 1.07 to 3.27). Higher doses did not yield better effectiveness among children (0.87 v 0.85, P=0.981). Conclusions Eflornithine shows acceptable safety and effectiveness as first line treatment for human African trypanosomiasis. Relapses did occur more than 12 months after treatment. Higher doses in children were well tolerated but showed no advantage in effectiveness.

Nifurtimox-eflornithine combination therapy for second-stage Trypanosoma brucei gambiense sleeping sickness: a randomized clinical trial in Congo

BACKGROUND

Human African trypanosomiasis caused by Trypanosoma brucei gambiense is a fatal disease. Current treatment options for patients with second-stage disease are either highly toxic or impracticable in field conditions. We compared the efficacy and safety of the nifurtimox-eflornithine drug combination with the standard eflornithine regimen for the treatment of second-stage disease.

METHODS

A randomized, open-label, active-control, phase III clinical trial comparing 2 arms was conducted at the Sleeping Sickness Treatment Center, which was run by Medecins Sans Frontieres, in Nkayi, Bouenza Province, Republic of Congo. Patients were screened for inclusion and randomly assigned to receive eflornithine alone (400 mg/kg per day given intravenously every 6 h for 14 days) or eflornithine (400 mg/kg per day given intravenously every 12 h for 7 days) plus nifurtimox (15 mg/kg per day given orally every 8 h for 10 days). Patients were observed for 18 months. The study's outcomes were cure and adverse events attributable to treatment.

RESULTS

A total of 103 patients with second-stage disease were enrolled. Cure rates were 94.1% for the eflornithine group and 96.2% for the nifurtimox-eflornithine group. Drug reactions were frequent in both arms, and severe reactions affected 25.5% of patients in the eflornithine group and 9.6% of those in the nifurtimox-eflornithine group, resulting in 2 and 1 treatment suspensions, respectively. There was 1 death in the eflornithine arm and no deaths in the nifurtimox-eflornithine arm.

CONCLUSIONS

The nifurtimox-eflornithine combination appears to be a promising first-line therapy for second-stage sleeping sickness. If our findings are corroborated by ongoing findings from additional sites (a multicenter extension of this study), the new nifurtimox-eflornithine combination therapy will mark a major and multifaceted advance over current therapies.

Detection of trypanosome-specific antibodies in saliva, towards non-invasive serological diagnosis of sleeping sickness

OBJECTIVE

The detection of trypanosome-specific antibodies in saliva is technically feasible, and, if clinically validated, could become an attractive option for non-invasive diagnosis of sleeping sickness. We wanted to optimize the test format of an enzyme-linked immunosorbent assay (ELISA)-based antibody detection system.

METHODS

Different ELISA formats for antibody detection in serum and saliva were developed and standardized. Saliva and serum samples were collected from 78 patient and 128 endemic control samples, and sensitivity and specificity of saliva ELISAs, serum ELISAs and the card agglutination test for trypanosomiasis (CATT), were evaluated.

RESULTS

All ELISA formats showed sensitivity and specificity above 90%. Saliva ELISAs showed a similar test performance as serum ELISAs and the CATT on whole blood or serum.

CONCLUSIONS

This study confirms the potential of trypanosome-specific antibody detection in saliva.

High prevalence of Trypanosoma brucei gambiense group 1 in pigs from the Fontem sleeping sickness focus in Cameroon

To understand the importance of domestic pigs in the epidemiology of human trypanosomiasis, PCR was used to identify trypanosome populations in 133 pigs from the Fontem sleeping sickness focus of Cameroon. The results from this study show that 73.7% (98/133) of pigs from the Fontem area carry at least one trypanosome species. Trypanosoma vivax, T. brucei s.l. and T. congolense forest were found in 34.6% (46/133), 40.0% (53/133) and 46.0% (61/133) of the pigs respectively. T. simiae and T. congolense savannah were not identified in these animals. The use of repeated DNA sequences detected T. b. gambiense group 1 in 14.8% (15/101) of the pigs. Such pigs can be possible reservoir hosts for T. b. gambiense group 1 and contribute to the maintenance of the disease in the area. Mixed infections were revealed in 35.3% (47/133) of the pigs. Furthermore, we observed that under natural conditions, 52.4% (11/21) of the pigs from the Fontem focus carry mixed infections with T. b. gambiense group 1. No significant difference was observed between the percentage of T. b. gambiense group 1 single and mixed infections, and between the prevalence of this trypanosome in pigs from villages with and without sleeping sickness patients.

Wild fauna as a probable animal reservoir for Trypanosoma brucei gambiense in Cameroon

In order to study the existence of a wild animal reservoir for Trypanosoma brucei gambiense in South Cameroon, blood was collected from wild animals in three human African trypanosomiasis foci and from a nonendemic control area. The 1142 wild animals sampled belonged to 36 different species pertaining to eight orders (407 primates, 347 artiodactyls, 265 rodents, 54 pangolins, 53 carnivores, 11 saurians and crocodilians, and five hyraxes). QBC and KIVI tests detected trypanosomes on 1.7% (13/762) and 18.4% (43/234) of animals examined, respectively. Using specific primers, T. brucei non-gambiense group 1 DNA was detected on 56 animals (4.9%). This infection rate was 5.3% in the endemic zone and 3.8% in the control zone. Of the 832 animals of the endemic zone, PCR revealed T. b. gambiense group 1 DNA in 18 (2.2%). These hosts included two rodents, two artiodactyls, two carnivores and two primates. T. b. gambiense group 1 was absent from animals from the nonendemic zone. A decrease in the prevalence of T. b. gambiense group 1 was observed in wild animals from the Bipindi sleeping sickness focus after a medical survey and vector control in this area. The epidemiological implications of these findings remain to be determined with further investigations.

Spontaneous cure of domestic pigs experimentally infected by Trypanosoma brucei gambiense. Implications for the control of sleeping sickness

The existence of a pig reservoir for human African trypanosomosis (HAT) due to Trypanosoma brucei gambiense complicates the fight against this disease. This study, reports results obtained from pigs, which were inoculated with the blood of a person, suffering from HAT in Cameroon. The pigs were reared and kept in the shelter from all contact with Glossina, and monitored for 188 days. The seroconversion was checked by agglutination assays for trypanosomosis (CATT 1.3 and LATEX/T.b.gambiense). The parasitemia was measured by quantitative buffy coat method (QBC) and by polymerase chain reaction method (PCR). In addition, growth was recorded as well as blood counting and blood formulas. The results showed that the pigs were trypanotolerant and cure themselves in less than 6 months. It is concluded that sterilisation of this reservoir could be achieved by tsetse-control measures in 1 year. It confirms the strategy to complement screening and treatment of HAT with tsetse fly control measures.

African trypanosomiasis: Changing epidemiology and consequences

Human African trypanosomiasis has re-emerged as a serious public health threat after near-elimination because of diminished investment in previously successful control programs. The continued, occasional importation of African trypanosomiasis to the United States can be expected as tourists and immigrants travel from high-risk areas. No vaccine or chemoprophylaxis is available for this disease, and travelers to affected areas should be counseled on tsetse fly avoidance. New diagnostic and staging tests are promising but have not replaced the classical method of examining body fluids for trypanosomes. Prompt diagnosis and staging is essential because if untreated, East African and West African sleeping sickness are fatal. Drug regimens are toxic and cumbersome, and short-term prospects for therapeutic advances are limited.

Options for field diagnosis of human african trypanosomiasis

Human African trypanosomiasis (HAT) due to Trypanosoma brucei gambiense or T. b. rhodesiense remains highly prevalent in several rural areas of sub-Saharan Africa and is lethal if left untreated. Therefore, accurate tools are absolutely required for field diagnosis. For T. b. gambiense HAT, highly sensitive tests are available for serological screening but the sensitivity of parasitological confirmatory tests remains insufficient and needs to be improved. Screening for T. b. rhodesiense infection still relies on clinical features in the absence of serological tests available for field use. Ongoing research is opening perspectives for a new generation of field diagnostics. Also essential for both forms of HAT is accurate determination of the disease stage because of the high toxicity of melarsoprol, the drug most widely used during the neurological stage of the illness. Recent studies have confirmed the high accuracy of raised immunoglobulin M levels in the cerebrospinal fluid for the staging of T. b. gambiense HAT, and a promising simple assay (LATEX/IgM) is being tested in the field. Apart from the urgent need for better tools for the field diagnosis of this neglected disease, improved access to diagnosis and treatment for the population at risk remains the greatest challenge for the coming years.

[Contributions and limits of the diagnosis of human African trypanosomiasis]

Human African trypanosomiasis, or sleeping sickness, is still a worrying problem in Africa. Sleeping sickness is a disease for which a systematic monitoring is necessary, particularly for the trypanosomiasis caused by Trypanosoma brucei gambiense, which is characterized by a long asymptomatic stage. In the absence of specific clinical signs, mass screening of populations remains the only way to control the disease and to avoid its spreading. The lack of sensitivity and specificity of the diagnosis tests classically used led to the development of molecular tools. PCR amplification of parasite specific sequences has considerably improved the diagnostic of the parasitic infection, the stage diagnosis as well as the post-therapeutic follow-up. But there are limits with a use in routine and research is still necessary to make PCR a real tool for control of sleeping sickness.

Infection rate of Trypanosoma brucei s.l., T. vivax, T. congolense "forest type", and T. simiae in small wild vertebrates in south Cameroon

In order to identify the infection rate of trypanosome species infecting wild animals in four localities (Bipindi, Campo, Fontem and Nditam) of southern Cameroon, 1,141 wild animals were sampled. These animals belonged to 36 species grouped in 8 orders including 407 primates, 347 artiodactyls, 264 rodents, 54 pangolins, 53 small carnivores, 11 saurians and crocodilians and 5 hyraxes. PCR using specific primers for Trypanosoma vivax, T. brucei s.l., T. congolense "forest type", and T. simiae showed that 18.7% of the animals were infected by at least one of these trypanosome species. A positive PCR result may not indicate absolutely an active infection because PCR can detect also transient infections. T. vivax (Duttonella) had the highest infection rate (9.5%) and was found in almost all the host orders studied. T. brucei s.l. mostly infected primates, rodents and some duikers (Cephalophus dorsalis and C. monticola). Trypanosomes of the subgenus Nannomonas had a lower infection rate of 5.5% (2.4% for T. simiae and 3.1% for T. congolense "forest type"). They were harboured mainly by primates, ungulates and rodents. Trypanosome infection rates were highest in Nditam (24.5%) and Bipindi (21%). T. brucei s.l. (Trypanozoon) had its maximum infection rate of 10.4% in Bipindi. The "Quantitative Buffy Coat" (QBC) and Kit for in vitro isolation techniques were used to identify 48 (6.1%) infected animals. 13 were positive using QBC, and 42 were positive by KIVI. However, PCR was negative on 16 of these infected animals, probably due to infections with other trypanosome species. This study showed that trypanosomes of the subgenera Duttonella, Nannomonas and Trypanozoon could infect small wild vertebrates as has been shown for large ungulates and carnivores. The presence of T. brucei s.l. in a large range of wild animals strengthens the hypothesis of the existence of a wild animal reservoir of T. b. gambiense in Cameroon.

The effectiveness of active population screening and treatment for sleeping sickness control in the Democratic Republic of Congo

BACKGROUND

The human African trypanosomiasis (HAT) control programme of the Democratic Republic of Congo (DRC) uses mass screening with the card agglutination test for trypanosomes (CATT). We looked at the contribution of CATT and improved parasitological confirmation to the effectiveness of screening and treatment.

METHOD

The effectiveness of the screening and treatment process is measured by the percentage of HAT cases that is effectively cured after a single round of screening. The process is analysed in five steps: (i) the attendance at the screening, (ii) the sensitivity of the screening procedure, (iii) the sensitivity of the parasitological confirmation, (iv) the proportion of the confirmed cases that effectively receive treatment and (v) the cure rate of the treatment. We used a simplified model that multiplies proportions of infected persons that go through each step. We estimated these parameters using a combination of routine data collected by the national control programme over the period January 1997 to December 1998 and published data. For varying attendance rates we compared the effectiveness of screening strategies based on CATT or on CATT combined with improved parasitological confirmation by mini anion exchange column technique (mAECT) with the previously used strategy based on palpation of neck glands and microscopy alone.

RESULTS

The model shows that overall effectiveness of the active case detection and treatment strategy is <50% under most scenarios. Attendance rates averaged 74% but showed considerable regional variability and are a major problem in some areas of DRC. The CATT and replacing traditional parasitology by mAECT increases the sensitivity of the screening but a substantial part of the gains are lost at other stages of the screening process.

CONCLUSION

Improvements of the HAT screening process such as introduction of CATT or mAECT only make sense if other parameters and attendance rate in particular are optimized at the same time.

Evaluation of LATEX/T.b.gambiense for mass screening of Trypanosoma brucei gambiense sleeping sickness in Central Africa

We compared the Card Agglutination Test for Trypanosomiasis (CATT), which consists of lyophilized bloodstream form trypomastigotes of Trypanosoma brucei gambiense (T.b.g.) variable antigen type LiTat 1.3, with LATEX/T.b.g., which consists of a lyophilized suspension of latex particles coated with variable surface glycoproteins of T.b.g. variable antigen types LiTat 1.3, 1.5 and 1.6. This study was carried out during two mass screening surveys in 1998 in Campo, a sleeping sickness focus in Cameroon, with a low prevalence (0.3%) and in 1999 in Batangafo which belongs to the Central African focus of Ouham which has a higher prevalence (3%). In Campo, we compared the CATT performed on whole blood with the LATEX/T.b.g. on diluted blood. In Batangafo, both tests were performed on diluted blood. In all circumstances, the specificity of the LATEX/T.b.g. was higher than of CATT. The use of LATEX/T.b.g. on diluted blood instead of CATT results in an important decrease of workload and as a consequence, of costs related to parasitological examinations. In the case of Campo the workload was up to 12 times less than when using CATT 1.3 on whole blood and the cost divided by 3. In Batangafo the workload was decreased by nearly 20% with the LATEX/T.b.g. Finally, it should be noted that in Batangafo, one of the parasitologically confirmed sleeping sickness patients was negative in CATT and positive in LATEX/T.b.g. and that the reading of the test result in LATEX/T.b.g. is easier than in CATT.

Characterization of Trypanosoma brucei s.l. subspecies by isoenzymes in domestic pigs from the Fontem sleeping sickness focus of Cameroon

Though it has been established that domestic animals (especially the pig) are potential reservoir hosts for Trypanosoma brucei gambiense in West Africa, there is little data to this effect concerning Central Africa. Instead, some previous authors report the absence of Trypanozoon type trypanosomes in domestic animals in Cameroon. Thirty-two domestic pigs were sampled by KIVI (kit for in vitro isolation) of trypanosomes in the northern region (Bechati) of the Fontem sleeping sickness focus of Cameroon. Twenty-one of these were found positive, from 15 of which 17 isolates were successfully obtained. Isoenzyme characterization revealed that isolates from 4 of the 15 pigs belonged to zymodemes associated with T. brucei gambiense group 1. The prevalence of this disease in the local human population is, however, very low. It is evident from this study that the domestic pig may be a potential reservoir host for T. brucei gambiense in the Fontem focus. There is, however, need for an extensive study on domestic animals in Cameroon and other neighbouring countries for a better comprehension of the epidemiology of sleeping sickness within the Central African region.

Infectious diseases manifested in the peripheral blood

Although primary diagnosis of infectious disease is uncommonly made from morphologic examination of a blood smear in the United States, knowledge of the distinctive morphologic features of various organisms, coupled with an understanding of the clinical and epidemiologic features of various disorders, permits recognition and diagnosis of uncommonly encountered infections. Furthermore, nonspecific manifestations of infection may provide an important clue in guiding a further diagnostic work-up.

QBC for the diagnosis of human and canine american visceral leishmaniasis: preliminary data

"Quantitative Buffy Coat" (QBC) is a direct and fast fluorescent method used for the identification of blood parasites. Since Leishmania chagasi circulates in blood, we decided to test it in American visceral leishmaniasis (AVL). Bone marrow (BM) and peripheral blood (PB) of 49 persons and PB of 31 dogs were analyzed. QBC was positive in BM of 11/11 patients with AVL and in 1/6 patients with other diseases. Amastigotes were identified in PB of 18/22 patients with AVL and in none without AVL. The test was positive in 30 out of the 31 seropositive dogs and in 28/28 dogs with Leishmania identified in other tissues. QBC is a promising method for diagnosis of human AVL, and possibly for the exam of PB of patients with AVL/AIDS, for the control of the cure and for the identification of asymptomatic carriers. Because it is fast and easy to collect and execute, QBC should be evaluated for programs of reservoir control.

Follow-up of Card Agglutination Trypanosomiasis Test (CATT) positive but apparently aparasitaemic individuals in Côte d'Ivoire: evidence for a complex and heterogeneous population

The aetiological diagnosis of human African trypanosomiasis (HAT) is based on the detection of the parasite, but currently available parasitological tests have low sensitivity and are hampered by fluctuating parasitaemia. The identification of seropositive individuals on whom to focus parasitological examination is based on antibody detection by means of the Card Agglutination Trypanosomiasis Test (CATT/T.b.gambiense). A complicating phenomenon is the occurrence of serologically positive but parasitologically unconfirmed results (isolated CATT positivity). This work presents a two-year longitudinal serological, parasitological and molecular follow-up of CATT-positive individuals including repeated examinations of each individual, to study the evolution over time of seropositivity at both the population and the individual levels. At the population level, the rate of seropositivity decreased during the first months of the survey, and afterwards showed remarkable stability. At the individual level, the results reveal the extreme heterogeneity of this population, with subjects showing fluctuating results, others with a short transient CATT positivity, and subjects that maintain their seropositivity over time. The stability of seropositivity and the pattern of results obtained with both immunological and parasitological examinations support the view that individual factors, such as immune response to infection, might be involved in the isolated CATT positivity phenomenon.

Preliminary evaluation of LATEX/T. b. gambiense and alternative versions of CATT/T. b. gambiense for the serodiagnosis of human african trypanosomiasis of a population at risk in Côte d'Ivoire: considerations for mass-screening

A study was conducted to compare classical card agglutination test for trypanosomiasis (CATT)/T. b. gambiense with CATT-EDTA and LATEX/T. b. gambiense as alternative field tests for serodiagnosis of Human African Trypanosomiasis. The tests were performed on freshly collected blood in an endemic and a low prevalence area in Côte d'Ivoire. Diagnostic performance of each test was assessed using Quantitative Buffy Coat as the parasitological reference and immune trypanolysis as the serological reference test. According to the parasitological data, CATT-EDTA on 10 microl and LATEX/T. b. gambiense on blood diluted 1:4, detecting all confirmed cases with good specificity (respectively 94.6% and 98.1%) yielded better results than the classical CATT did (one false negative and 92.5% specific). However, when immune trypanolysis data and feasibility are taken into account, the classical CATT remains the test of choice for mass screening under the given field conditions.

Diagnosis of human trypanosomiasis, due to Trypanosoma brucei gambiense in central Africa, by the polymerase chain reaction

During a mass screening of sleeping sickness conducted in 1998 and 1999, and involving 27,932 persons in Cameroon and the Central African Republic, we tested the polymerase chain reaction (PCR) on whole blood for the diagnosis of human African trypanosomiasis due to Trypanosoma brucei gambiense. The 1858 samples obtained were from 4 groups: 155 infected patients, 1432 serological suspects detected by the card agglutination test for trypanosomiasis (CATT), 222 negative controls living in the prospected area (negative with the CATT and parasitological methods), and 49 negative controls (CATT and parasitological methods) and unexposed to the disease (Europeans). The technique of DNA extraction used made it possible to preserve the blood samples in the field. The primers used were specific for T. brucei s.l. Only 1 patient was PCR negative, and 3 of the negative controls, exposed to the disease, were PCR positive. Among the 1432 serological suspects, only 50 were PCR positive. During the 6-month follow-up after the surveys, the 3 negative controls, who were initially positive by PCR, were found to be negative. These initial positive PCR results are unlikely to have been due to a cross-reaction with T. brucei brucei, which is non-pathogenic for man, but are more likely to have resulted from a mislabelling of sample tubes. All control individuals, exposed or not to the disease, were negative by PCR. The PCR-negative patient was possibly a registration error. Among 50 PCR positive serological suspects, 39 of them were re-examined. Five were found to be positive by the kit for in-vitro isolation of trypanosomes, representing an increase in patients of almost 13%. At the end of the study, 160 patients were diagnosed, and the PCR was positive for 159 of them (99.4%). Moreover, the PCR made it possible to reduce the number of suspects to be re-examined (50 instead of 1432; a reduction of 96.5%).

Isolation of Trypanosoma brucei gambiense from northern Uganda: evaluation of the kit for in vitro isolation (KIVI) in an epidemic focus

867 individuals from 3 sites near the town of Adjumani in the East Moyo region of north-west Uganda were investigated clinically and serologically for evidence of current trypanosome infections. Blood samples were taken from 94 persons with a positive card agglutination test for trypanosomiasis (CATT) and clinical suspects and inoculated into the kit for in vitro isolation of Trypanosoma brucei gambiense (KIVI). Amongst this group, 30 parasitaemic individuals were identified by microhaematocrit centrifugation and the quantitative buffy coat technique (QBC). Only 80% of these isolates, and one isolate from an aparasitaemic individual, grew in culture. The success or failure of cultures from parasitaemic patients was unrelated to the size of the trypanosome inoculum. The implications of these results and possible reasons for the failure of KIVI are discussed.

A comparison of parasitological methods for the diagnosis of gambian trypanosomiasis in an area of low endemicity in Côte d'Ivoire

The card agglutination test for trypanosomiasis (CATT) was used to examine 8974 inhabitants in 14 village areas south-west of Daloa, Côte d'Ivoire; 114 (1.3%) were CATTT or +/-, and were further examined by one or more of 6 methods for the direct detection of trypanosomes: lymphatic gland puncture, stained thick blood film (TBF), haematocrit centrifugation technique (HCT), mini-anion exchange column (MAEC), quantitative buffy coat method (QBC), and kit for in vitro isolation of trypanosomes (KIVI). Trypanosomes were seen by at least one method in 16 (14.0%) of the CATT+ group. Blood from 356 of the 8860 CATT- group was inoculated into KIVI; trypanosomes grew from the blood of 1 person. Eleven of the 17 patients with detectable trypanosomes were screened by all 6 methods: 6 were HCT+; 7 were gland+; 10 were MAEC+; 10 were KIVI+; 11 were both TBF+ and QBC+. One CATT+ patient was KIVI+ but otherwise negative, although TBF was not done. The overall prevalence of trypanosomes was 0.2% rising to 0.8% in one village area. The results support previous evidence that a reappraisal of procedures is required in the customary system of surveillance for gambian sleeping sickness.

The quantitative buffy coat for the diagnosis of trypanosomes

The use of quantitative buffy coat (QBC) tubes developed for malaria diagnosis is described in the diagnosis of African trypanosomiasis. One hundred and thirty-four patients with Trypanosoma gambiense were examined using QBC plus either haematocrit (HCT) or mini anion exchange centrifugation (MAEC) or both. QBC was the only method that detected all 134 patients. QBC proved to be the most sensitive diagnostic test for the detection of trypanosomes in blood. It is simple to use, gives fast results and would be a useful test at the district hospital level.

Isoenzyme comparison of Trypanozoon isolates from two sleeping sickness areas of south-eastern Uganda

The study characterized 151 Trypanozoon isolates from south-east Uganda by isoenzyme electrophoresis. Stocks were from a range of hosts, including man, cattle, pigs, dogs and Glossina fuscipes fuscipes: 104 isolates were from the Busoga area, 47 were from the Tororo district. Stocks were characterized on thin layer starch gel using eight enzyme systems: ALAT, ASAT, ICD, MDH, ME, NHD, NHI, PGM. Enzyme profiles were generally typical of East Africa; new patterns for ICD and ME were detected. Trypanosomes were classified on the basis of their profile by similarity coefficient analysis and the unweighted pair-group method using arithmetic averages (UPGMA). The majority of trypanosomes were classified in one or other of two genetically distinct groups which corresponded to the strain groups busoga and zambezi, both of which are associated with Rhodesian sleeping sickness in East Africa. Contingency table analyses indicated associations between certain isoenzymes of ICD and PGM, according to host and geographical origin. Significant relationships between trypanosome strain group and geographic origin were also demonstrated for some host groups.

Use of the Quantitative Buffy Coat system for detection of parasitemia in patients with babesiosis

Quantitative Buffy Coat analysis and blood smears were performed on a total of 47 blood samples. The technique showed 100% correlation with the blood smears in 9 samples containing babesia and 10 samples containing malaria, with some differential features distinguishing the two infections. Quantitative Buffy Coat analysis provides a simple and rapid method for the detection of parasitemia in cases of babesiosis.