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 fies; 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 Trypanosoma vivax, consisting of 899 records from 245 peer-reviewed articles in 41 countries. A total of 232,627 tests were performed on 97 different mammalian hosts, including a wide range of wild animals. Natural infections of T. vivax were recorded in 39 diferent 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 Trypanosoma vivax and demonstrates the potential of this parasite to invade other countries out of Africa and Latin America

The separation of trypanosomes from blood by anion exchange chromatography: From Sheila Lanham's discovery 50 years ago to a gold standard for sleeping sickness diagnosis

Human African trypanosomiasis (HAT), or sleeping sickness, is a neglected tropical disease that is fatal if untreated, caused by Trypanosoma brucei gambiense and T. brucei rhodesiense. In its 2012 roadmap, WHO targeted HAT for elimination as a public health problem in 2020 and for zero transmission in 2030. Diagnosis of HAT is a multistep procedure comprising of clinical suspicion, confirmation, and stage determination. Suspects are identified on clinical signs and/or on screening for specific antibodies. Parasitological confirmation of suspects remains mandatory to avoid unnecessary toxic drug administration. The positive predictive value of the antibody detection tests is low. Simple parasite detection techniques, microscopic examination of lymph node aspirate, or stained thick blood films lack sensitivity, whereas in T. brucei gambiense patients, the number of blood trypanosomes may be very low. Parasite concentration techniques are therefore indispensable. Half a century ago, Sheila Lanham discovered a technique to separate trypanosomes from the blood of infected rodents, based on anion exchange chromatography with diethyl amino ethyl (DEAE) cellulose, a weak anion exchanger. Between pH 6−9, trypanosome surface is less negatively charged than that of blood cells. When blood is poured on top of a DEAE cellulose column, blood cells are retained, whereas parasites pass the column together with the elution buffer. The result is a pure suspension of trypanosomes that retain their morphology and infectivity. Because cell surface charges vary among trypanosome and mammal species, the optimal buffer pH and ionic strength conditions for different combinations of host and trypanosome species were established. Lanham's technique revolutionized the diagnosis of HAT. It is indispensable in the production of the Card Agglutination Test for Trypanosomiasis (CATT), the most used field test for screening in T. brucei gambiense HAT foci and essential to confirm the diagnosis in suspected people. Lumsden and colleagues developed the mini anion exchange centrifugation technique (mAECT). After adaptation for field conditions, its superior diagnostic and analytical sensitivity compared to another concentration technique was demonstrated. It was recommended as the most sensitive test for demonstrating trypanosomes in human blood. At the beginning of the 21st century, the mAECT was redesigned, allowing examination of a larger volume of blood, up to 0.35 ml with whole blood and up to 10 ml with buffy coat. The plastic collector tube in the new kit is also used for detection of trypanosomes in the cerebrospinal fluid. Unfortunately, mAECT also has some disadvantages, including its price, the need to centrifuge the collector tube, and the fact that it is manufactured on a noncommercial basis at only two research institutes. In conclusion, 50 years after Sheila Lanham's discovery, CATT and mAECT have become essential elements in the elimination of HAT

Case of Nigeria-Acquired Human African Trypanosomiasis in United Kingdom, 2016.

Human African trypanosomiasis has not been reported in Nigeria since 2012. Nevertheless, limitations of current surveillance programs mean that undetected infections may persist. We report a recent case of stage 2 trypanosomiasis caused by Trypanosoma brucei gambiense acquired in Nigeria and imported into the United Kingdom

Identification of Mimotopes with Diagnostic Potential for Trypanosoma brucei gambiense Variant Surface Glycoproteins Using Human Antibody Fractions

Background: At present, screening of the population at risk for gambiense human African trypanosomiasis (HAT) is based on detection of antibodies against native variant surface glycoproteins (VSGs) of Trypanosoma brucei (T.b.) gambiense. Drawbacks of these native VSGs include culture of infective T.b. gambiense trypanosomes in laboratory rodents, necessary for production, and the exposure of non-specific epitopes that may cause cross-reactions. We therefore aimed at identifying peptides that mimic epitopes, hence called “mimotopes,” specific to T.b. gambiense VSGs and that may replace the native proteins in antibody detection tests. Methodology/Principal Findings A Ph.D.-12 peptide phage display library was screened with polyclonal antibodies from patient sera, previously affinity purified on VSG LiTat 1.3 or LiTat 1.5. The peptide sequences were derived from the DNA sequence of the selected phages and synthesised as biotinylated peptides. Respectively, eighteen and twenty different mimotopes were identified for VSG LiTat 1.3 and LiTat 1.5, of which six and five were retained for assessment of their diagnostic performance. Based on alignment of the peptide sequences on the original protein sequence of VSG LiTat 1.3 and 1.5, three additional peptides were synthesised. We evaluated the diagnostic performance of the synthetic peptides in indirect ELISA with 102 sera from HAT patients and 102 endemic negative controls. All mimotopes had areas under the curve (AUCs) of ≥0.85, indicating their diagnostic potential. One peptide corresponding to the VSG LiTat 1.3 protein sequence also had an AUC of ≥0.85, while the peptide based on the sequence of VSG LiTat 1.5 had an AUC of only 0.79. Conclusions/Significance: We delivered the proof of principle that mimotopes for T.b. gambiense VSGs, with diagnostic potential, can be selected by phage display using polyclonal human antibodies

The importance of genetic testing in adolescent-onset steroid-resistant nephrotic syndrome - Case report

Approximately 10-20% of children and 40% of adults with idiopathic nephrotic syndrome are steroid resistant and progress to end-stage renal disease requiring dialysis or renal transplantation. In these cases, renal histology typically shows focal segmental glomerulosclerosis. Mutations in NPHS1, NPHS2, WT1, CD2AP and ACTN4 genes located on different chromosomes, expressed by glomerular podocytes, have been identified in patients with steroid-resistant nephrotic syndrome. The authors report two cases of adolescent-onset steroid-resistant nephrotic syndrome. Both cases had similar clinical and histopathological manifestations, with different prognosis and evolution due to different mechanisms leading to proteinuria: an acquired and a genetic form. The first case, a 16 year old girl presented the onset of the disease with massive, generalized edema, secondary hypothyroidism and high blood pressure. Evolution was favorable under cyclosporine therapy. The second case, a 13-years-old adolescent girl, presented an insidious onset of the disease with mild edema. Genetic testing revealed a mutation in the WT1 gene. The patient developed end-stage kidney failure eight months after the onset of the disease and following kidney transplant had a favorable evolution. Histological examination of the renal biopsy specimen showed focal segmental glomerulosclerosis in both cases. Conclusions: Genetic forms of nephrotic syndrome do not respond to immunosuppressive therapy and may progress to end-stage renal disease, but after kidney transplantation relapse is not expected, in contrast to the immune form. The early genetic diagnosis in steroid-resistant nephrotic syndrome is time-consuming, but is important for proper clinical management of the patients, prognosis and genetic counseling of the families

Sensitivity and specifi city of HAT Sero-K-SeT, a rapid diagnostic test for serodiagnosis of sleeping sickness caused by Trypanosoma brucei gambiense: a case-control study

Background Human African trypanosomiasis (HAT) is a life-threatening infection aff ecting rural populations in sub- Saharan Africa. Large-scale population screening by antibody detection with the Card Agglutination Test for Trypanosomiasis (CATT)/Trypanosoma brucei (T b) gambiense helped reduce the number of reported cases of gambiense HAT to fewer than 10 000 in 2011. Because low case numbers lead to decreased cost-eff ectiveness of such active screening, we aimed to assess diagnostic accuracy of a rapid serodiagnostic test (HAT Sero-K-SeT) applicable in primary health-care centres. Methods In our case-control study, we assessed participants older than 11 years who presented for HAT Sero-K-SeT and CATT/T b gambiense at primary care centres or to mobile teams (and existing patients with confi rmed disease status at these centres) in Bandundu Province, DR Congo. We defi ned cases as patients with trypanosomes that had been identifi ed in lymph node aspirate, blood, or cerebrospinal fl uid. During screening, we recruited controls without previous history of HAT or detectable trypanosomes in blood or lymph who resided in the same area as the cases. We assessed diagnostic accuracy of three antibody detection tests for gambiense HAT: HAT Sero-K-SeT and CATT/T b gambiense (done with venous blood at the primary care centres) and immune trypanolysis (done with plasma at the Institute of Tropical Medicine, Antwerp, Belgium). Findings Between June 6, 2012, and Feb 25, 2013, we included 134 cases and 356 controls. HAT Sero-K-SeT had a sensitivity of 0·985 (132 true positives, 95% CI 0·947–0·996) and a specifi city of 0·986 (351 true negatives, 0·968–0·994), which did not diff er signifi cantly from CATT/T b gambiense (sensitivity 95% CI 0·955, 95% CI 0·906–0·979 [128 true positives] and specifi city 0·972, 0·949–0·985 [346 true negatives]) or immune trypanolysis (sensitivity 0·985, 0·947–0·996 [132 true positives] and specifi city 0·980, 0·960–0·990 [349 true negatives]). Interpretation The diagnostic accuracy of HAT Sero-K-SeT is adequate for T b gambiense antibody detection in local health centres and could be used for active screening whenever a cold chain and electricity supply are unavailable and CATT/T b gambiense cannot be done

DIAGNOSTIC TOOLS FOR HUMAN AFRICAN TRYPANOSOMIASIS ELIMINATION AND CLINICAL TRIALS: THE DITECT-HAT PROJECT

Background Trypanosoma brucei gambiense (Tbg) causes human African trypanosomiasis (HAT), one of the neglected tropical diseases targeted for elimination. Integration of diagnosis and case management into the general health system, sustainable monitoring of eliminated foci and development of safe and efficacious drugs, remain important challenges. Methods The DiTECT-HAT project tackles these challenges. For passive case detection, we will determine the diagnostic performance and cost of rapid diagnostic tests (RDTs) performed on clinical suspects in peripheral health centres, whether or not combined with serological and/or molecular tests on filter paper done at regional reference centres. Cost-effective diagnostic algorithms with high positive predictive values might allow test-and-treat scenarios without the need for complicated parasitological confirmations. Secondly, health workers performing house to house visits in foci with very low HAT prevalence can easily collect blood on filter paper and send it to regional HAT reference centres for analysis. The feasibility and cost of diagnostic algorithms with RDTs, serological and molecular high-throughput tests for post-elimination monitoring will be determined. An appropriate threshold will be established to trigger active case finding to avoid re-emergence of HAT, without unnecessarily raising the alarm. Finally, the accuracy of neopterin and RNA detection as early test-of-cure will be determined in therapeutic trials. Earlier treatment outcome assessment will speed up the development of new drugs for HAT, and improve management of relapses in routine care. Results An update of ongoing and planned activities is given. The passive case detection sub-project is being set up in DR Congo, Côte d'Ivoire and Guinea. The inclusions for the early test-of-cure sub-project are ongoing in DR Congo. Conclusions The proposed research will provide evidence to support policies for improved HAT diagnosis and patient management within a context of disease elimination, and will contribute to successful and sustainable HAT elimination

Deep kinetoplast genome analyses result in a novel molecular assay for detecting trypanosoma brucei gambiense-specific minicircles

The World Health Organization targeted Trypanosoma brucei gambiense (Tbg) human African trypanosomiasis for elimination of transmission by 2030. Sensitive molecular markers that specifically detect Tbg type 1 (Tbg1) parasites will be important tools to assist in reaching this goal. We aim at improving molecular diagnosis of Tbg1 infections by targeting the abundant mitochondrial minicircles within the kinetoplast of these parasites. Using Next-Generation Sequencing of total cellular DNA extracts, we assembled and annotated the kinetoplast genome and investigated minicircle sequence diversity in 38 animal- and human-infective trypanosome strains. Computational analyses recognized a total of 241 Minicircle Sequence Classes as Tbg1-specific, of which three were shared by the 18 studied Tbg1 strains. We developed a minicircle-based assay that is applicable on animals and as specific as the TgsGP-based assay, the current golden standard for molecular detection of Tbg1. The median copy number of the targeted minicircle was equal to eight, suggesting our minicircle-based assay may be used for the sensitive detection of Tbg1 parasites. Annotation of the targeted minicircle sequence indicated that it encodes genes essential for the survival of the parasite and will thus likely be preserved in natural Tbg1 populations, the latter ensuring the reliability of our novel diagnostic assay

Trypanosoma brucei gambiense-iELISA : a promising new test for the post-elimination monitoring of human African trypanosomiasis

Background: The World Health Organization targeted Trypanosoma brucei gambiense human African trypanosomiasis (gHAT) for elimination as a public health problem and for elimination of transmission. To measure gHAT elimination success with prevalences close to zero, highly specific diagnostics are necessary. Such a test exists in the form of an antibody-mediated complement lysis test, the trypanolysis test, but biosafety issues and technological requirements prevent its large-scale use. We developed an inhibition ELISA with high specificity and sensitivity that is applicable in regional laboratories in gHAT endemic countries. Methods: The T. b. gambiense inhibition ELISA (g-iELISA) is based on the principle that binding of monoclonal antibodies to specific epitopes of T. b. gambiense surface glycoproteins can be inhibited by circulating antibodies of gHAT patients directed against the same epitopes. Using trypanolysis as reference test, the diagnostic accuracy of the g-iELISA was evaluated on plasma samples from 739 gHAT patients and 619 endemic controls and on dried blood spots prepared with plasma of 95 gHAT and 37 endemic controls. Results: Overall sensitivity and specificity on plasma were respectively 98.0% (95% CI 96.7 - 98.9) and 99.5% (95% CI 98.6-99.9). With dried blood spots, sensitivity was 92.6% (95% CI 85.4 - 97.0), and specificity was 100% (95% CI 90.5 - 100.0). The g-iELISA is stable for at least 8 months when stored at 2-8°C. Conclusion: The g-iELISA might largely replace trypanolysis for monitoring gHAT elimination and for post-elimination surveillance. The g-iELISA kit is available for evaluation in reference laboratories in endemic countries