Diagnosis of human sleeping sickness: sense and sensitivity

A Systematic Review on Suitability of Molecular Techniques for Diagnosis and Research into Infectious Diseases of Concern in Resource-Limited Settings

Infectious diseases significantly impact the health status of developing countries. Historically, infectious diseases of the tropics especially have received insufficient attention in worldwide public health initiatives, resulting in poor preventive and treatment options. Many molecular tests for human infections have been established since the 1980s, when polymerase chain reaction (PCR) testing was introduced. In spite of the substantial innovative advancements in PCR technology, which currently has found wide application in most viral pathogens of global concern, the development and application of molecular diagnostics, particularly in resource-limited settings, poses potential constraints. This review accessed data from sources including PubMed, Google Scholar, the Web of Knowledge, as well as reports from the World Health Organization’s Annual Meeting on infectious diseases and examined these for current molecular approaches used to identify, monitor, or investigate some neglected tropical infectious diseases. This review noted some growth efforts in the development of molecular techniques for diagnosis of pathogens that appear to be common in resource limited settings and identified gaps in the availability and applicability of most of these molecular diagnostics, which need to be addressed if the One Health goal is to be achieved.

Electrochemical biosensors for neglected tropical diseases: A review

A group of infectious and parasitic diseases with prevalence in tropical and subtropical regions of the planet, especially in places with difficult access, internal conflicts, poverty, and low visibility from the government and health agencies are classified as neglected tropical diseases. While some well-intentioned isolated groups are making the difference on a global scale, the number of new cases and deaths is still alarming. The development and employment of low-cost, miniaturized, and easy-to-use devices as biosensors could be the key to fast diagnosis in such areas leading to a better treatment to further eradication of such diseases. Therefore, this review contains useful information regarding the development of such devices in the past ten years (2010-2020). Guided by the updated list from the World Health Organization, the work evaluated the new trends in the biosensor field applied to the early detection of neglected tropical diseases, the efficiencies of the devices compared to the traditional techniques, and the applicability on-site for local distribution. So, we focus on Malaria, Chagas, Leishmaniasis, Dengue, Zika, Chikungunya, Schistosomiasis, Leprosy, Human African trypanosomiasis (sleeping sickness), Lymphatic filariasis, and Rabies. Few papers were found concerning such diseases and there is no available commercial device in the market. The works contain information regarding the development of point-of-care devices, but there are only at proof of concepts stage so far. Details of electrode modification and construction of electrochemical biosensors were summarized in Tables. The demand for the eradication of neglected tropical diseases is increasing. The use of biosensors is pivotal for the cause, but appliable devices are scarce. The information present in this review can be useful for further development of biosensors in the hope of helping the world combat these deadly diseases.

Evidence of the absence of human African trypanosomiasis in two northern districts of Uganda: Analyses of cattle, pigs and tsetse flies for the presence of Trypanosoma brucei gambiense

BACKGROUND

Large-scale control of sleeping sickness has led to a decline in the number of cases of Gambian human African trypanosomiasis (g-HAT) to <2000/year. However, achieving complete and lasting interruption of transmission may be difficult because animals may act as reservoir hosts for T. b. gambiense. Our study aims to update our understanding of T. b. gambiense in local vectors and domestic animals of N.W. Uganda.

METHODS

We collected blood from 2896 cattle and 400 pigs and In addition, 6664 tsetse underwent microscopical examination for the presence of trypanosomes. Trypanosoma species were identified in tsetse from a subsample of 2184 using PCR. Primers specific for T. brucei s.l. and for T. brucei sub-species were used to screen cattle, pig and tsetse samples.

RESULTS

In total, 39/2,088 (1.9%; 95% CI = 1.9-2.5) cattle, 25/400 (6.3%; 95% CI = 4.1-9.1) pigs and 40/2,184 (1.8%; 95% CI = 1.3-2.5) tsetse, were positive for T. brucei s.l.. Of these samples 24 cattle (61.5%), 15 pig (60%) and 25 tsetse (62.5%) samples had sufficient DNA to be screened using the T. brucei sub-species PCR. Further analysis found no cattle or pigs positive for T. b. gambiense, however, 17/40 of the tsetse samples produced a band suggestive of T. b. gambiense. When three of these 17 PCR products were sequenced the sequences were markedly different to T. b. gambiense, indicating that these flies were not infected with T. b. gambiense.

CONCLUSION

The lack of T. b. gambiense positives in cattle, pigs and tsetse accords with the low prevalence of g-HAT in the human population. We found no evidence that livestock are acting as reservoir hosts. However, this study highlights the limitations of current methods of detecting and identifying T. b. gambiense which relies on a single copy-gene to discriminate between the different sub-species of T. brucei s.l.

Integrating innovations: a qualitative analysis of referral non-completion among rapid diagnostic test-positive patients in Uganda's human African trypanosomiasis elimination programme

BACKGROUND

The recent development of rapid diagnostic tests (RDTs) for human African trypanosomiasis (HAT) enables elimination programmes to decentralise serological screening services to frontline health facilities. However, patients must still undertake multiple onwards referral steps to either be confirmed or discounted as cases. Accurate surveillance thus relies not only on the performance of diagnostic technologies but also on referral support structures and patient decisions. This study explored why some RDT-positive suspects failed to complete the diagnostic referral process in West Nile, Uganda.

METHODS

Between August 2013 and June 2015, 85% (295/346) people who screened RDT-positive were examined by microscopy at least once; 10 cases were detected. We interviewed 20 RDT-positive suspects who had not completed referral (16 who had not presented for their first microscopy examination, and 4 who had not returned for a second to dismiss them as cases after receiving discordant [RDT-positive, but microscopy-negative results]). Interviews were analysed thematically to examine experiences of each step of the referral process.

RESULTS

Poor provider communication about HAT RDT results helped explain non-completion of referrals in our sample. Most patients were unaware they were tested for HAT until receiving results, and some did not know they had screened positive. While HAT testing and treatment is free, anticipated costs for transportation and ancillary health services fees deterred many. Most expected a positive RDT result would lead to HAT treatment. RDT results that failed to provide a definitive diagnosis without further testing led some to question the expertise of health workers. For the four individuals who missed their second examination, complying with repeat referral requests was less attractive when no alternative diagnostic advice or treatment was given.

CONCLUSIONS

An RDT-based surveillance strategy that relies on referral through all levels of the health system is inevitably subject to its limitations. In Uganda, a key structural weakness was poor provider communication about the possibility of discordant HAT test results, which is the most common outcome for serological RDT suspects in a HAT elimination programme. Patient misunderstanding of referral rationale risks harming trust in the whole system and should be addressed in elimination programmes.

Trypanosoma brucei triggers a marked immune response in male reproductive organs

African trypanosomiasis is caused by the protozoan parasite Trypanosoma brucei, transmitted between mammals by the bite of a tsetse. It has been recently shown that parasites accumulate in large numbers in various organs and tissues, including the mouse testis. Whether parasites are protected from the immune system in the male reproductive organ or can be transmitted through sexual route remains unknown. Here we show that parasites can be detected by fine needle aspiration cytology of the male reproductive system in mice, and histopathological analysis revealed that T. brucei accumulates in the stroma of the epididymis, epididymal adipose tissue and fibrous tunics of the testis. No parasites were found in the lumen of intact epididymal ducts or seminiferous tubules of the testis, indicating that the large majority of the parasites are not located in immune-privileged sites. In fact, these parasites are associated with marked inflammatory cell infiltration, parasite degeneration, and severe tissue damage and rupture of epididymal ducts, which may be related with reduced fertility. Overall, we show that just like in the bloodstream and most other tissues, in the male reproductive organs, T. brucei are exposed to a strong immune response. The detection of a very high number of parasites in this organ and its accessibility opens the possibility of using fine needle aspiration cytology as a complementary diagnostic tool in Animal African Trypanosomiasis.

A meta-analysis of the prevalence of African animal trypanosomiasis in Nigeria from 1960 to 2017

BACKGROUND

African animal trypanosomiasis is an economically significant disease that affects the livestock industry in Nigeria. It is caused by several parasites of the genus Trypanosoma. National estimates of the disease prevalence in livestock and tsetse flies are lacking, therefore a systematic review and meta-analysis were performed to understand the trend of the disease prevalence over the years.

METHODS

Publications were screened in Web of Science, Ovid MEDLINE, Global Health, EMBASE and PubMed databases. Using four-stage (identification, screening, eligibility and inclusion) process in the PRIMSA checklist, only studies that met the inclusion criteria for AAT and tsetse infections were analysed. Point estimates prevalence and subgroup analyses based on diagnostic techniques in livestock were evaluated at 95% confidence interval (CI).

RESULTS

A total of 74 eligible studies published between 1960 and 2017 were selected for meta-analysis. This covers the six geopolitical zones, involving a total of 53,924 animals. The overall prevalence of AAT was 16.1% (95% CI: 12.3-20.3%). Based on diagnostic techniques, the prevalence of AAT in cattle was highest in PCR followed by serology and microscopy while the highest prevalence in pigs was observed with serology. Out of 12,552 tsetse flies examined from 14 eligible studies, an overall prevalence of 17.3% (95% CI: 4.5-36.0%) and subgroup prevalence of 49.7% (95% CI: 30.7-68.8%), 11.5% (95% CI: 6.1-18.5) and 4.5% (95% CI: 1.8-8.8%) in G. morsitans, G. tachinoides and G. palpalis, respectively, were observed using the random effects-model.

CONCLUSIONS

The prevalence of trypanosomes in both vectors and animal hosts was high in Nigeria. Therefore, further research on risk factors, seasonal and transhumance effects, vectoral capacity and competence are warranted for an effective control of AAT in Nigeria.

Barcoding in trypanosomes

Trypanosomes (genus Trypanosoma) are parasites of humans, and wild and domestic mammals, in which they cause several economically and socially important diseases, including sleeping sickness in Africa and Chagas disease in the Americas. Despite the development of numerous molecular diagnostics and increasing awareness of the importance of these neglected parasites, there is currently no universal genetic barcoding marker available for trypanosomes. In this review we provide an overview of the methods used for trypanosome detection and identification, discuss the potential application of different barcoding techniques and examine the requirements of the 'ideal' trypanosome genetic barcode. In addition, we explore potential alternative genetic markers for barcoding Trypanosoma species, including an analysis of phylogenetically informative nucleotide changes along the length of the 18S rRNA gene.

Estimating the economic and social consequences for patients diagnosed with human African trypanosomiasis in Muchinga, Lusaka and Eastern Provinces of Zambia (2004-2014)

BACKGROUND

Acute human African trypanosomiasis (rHAT) caused by Trypanosoma brucei rhodesiense is associated with high mortality and is fatal if left untreated. Only a few studies have examined the psychological, social and economic impacts of rHAT. In this study, mixed qualitative and quantitative research methods were used to evaluate the socio-economic impacts of rHAT in Mambwe, Rufunsa, Mpika and Chama Districts of Zambia.

METHODS

Individuals diagnosed with rHAT from 2004 to 2014 were traced using hospital records and discussions with communities. Either they, or their families, were interviewed using a structured questionnaire and focus group discussions were conducted with affected communities. The burden of the disease was investigated using disability adjusted life years (DALYs), with and without discounting and age-weighting. The impact of long-term disabilities on the rHAT burden was also investigated.

RESULTS

Sixty four cases were identified in the study. The majority were identified in second stage, and the mortality rate was high (12.5%). The total number of DALYs was 285 without discounting or age-weighting. When long-term disabilities were included this estimate increased by 50% to 462. The proportion of years lived with disability (YLD) increased from 6.4% to 37% of the undiscounted and un-age-weighted DALY total. When a more active surveillance method was applied in 2013-2014 the cases identified increased dramatically, suggesting a high level of under-reporting. Similarly, the proportion of females increased substantially, indicating that passive surveillance may be especially failing this group. An average of 4.9 months of productive time was lost per patient as a consequence of infection. The health consequences included pain, amnesia and physical disability. The social consequences included stigma, dropping out of education, loss of friends and self-esteem. Results obtained from focus group discussions revealed misconceptions among community members which could be attributed to lack of knowledge about rHAT.

CONCLUSIONS

The social and economic impact of rHAT on rural households and communities is substantial. Improved surveillance and strengthening of local medical services are needed for early and accurate diagnosis. Disease prevention should be prioritised in communities at risk of rHAT, and interventions put in place to prevent zoonotic disease spill over from domestic animals and wildlife. Supportive measures to mitigate the long-term effects of disability due to rHAT are needed.

Prevalence of trypanosome infection in tsetse flies from Oji River and Emene axis of Enugu State, Nigeria: A preliminary report

INTRODUCTION

Trypanosomes are protozoan parasites of vertebrates transmitted by blood-sucking tsetse fly. Trypanosomes remain a constant threat to the lives of humans and animals throughout large regions of Africa.

AIMS AND OBJECTIVES

This study investigated the presence, prevalence, and species of trypanosome parasite in tsetse flies caught in two areas of no previous documented history of trypanosome infection.

MATERIALS AND METHODS

For this purpose, 63 and 77 nonterenal tsetse flies were collected from Oji River and Emene areas of Enugu State Nigeria, respectively. Genomic DNA was isolated from the whole tsetse fly using genomic DNA extraction kit. Identification and characterization of trypanosome were done using two approaches: the amplification of internal transcribed spacer 1 of ribosomal DNA and the use of primers specific to Trypanozoon.

RESULTS

In Oji River, of 63 tsetse flies collected, the identification of trypanosome parasite was done on 57 flies and 6 (10.71%) tsetse flies were infected with trypanosome parasite. Six flies were infected with Trypanosoma Congolense, 2 with Trypanosoma Vivax, and 1 with Trypanosoma brucei. Two mixed infections of T. vivax and T. congolense and 1 mixed infection of T. brucei and T. congolense was also identified. In Emene, of 77 tsetse flies collected, the identification of trypanosome parasite was done on 66 flies and 11 (16.6%) tsetse flies were infected with trypanosome parasite. Nine flies were infected with T. congolense, 2 with T. vivax, and 3 with T. brucei. Mixed infections identified include 2 mixed infections of T. brucei and T. congolense and 1 mixed infections of T. vivax and T. brucei. None of the subspecies of T. brucei were detected using species specific primers.

DISCUSSION

This study shows the parasitological evidence on the occurrence of animal African trypanosomiasis and also demonstrated that there is likely no active transmission of human African trypanosomiasis in the study areas.

CONCLUSION

This study shows that there is likely no active transmission of human African trypanosomiasis going on in these localities since no human infective form of the parasite was detected.

Molecular occurrence of trypanosomes, erythrocyte and serum sialic acid concentrations of Muturu and Bunaji cattle in Benue State, Nigeria

One hundred each, of Muturu and Bunaji cattle were screened, using polymerase chain reaction (PCR), for trypanosomes in Makurdi and Gboko Local Government Areas of Benue State, Nigeria. Erythrocyte surface sialic acid (ESSA) and free serum sialic acid (FSSA) concentrations were determined and compared in both breeds with the aim of providing baseline data for research and diagnostic purposes. Five per cent (5%) and 23% of the Muturu and Bunaji cattle, respectively, were positive for trypanosomes. The result at p=0.005 was significantly different, with p value of 0.0002 and odd ratio of 0.1762. The Trypanosoma species circulating in Benue State, as detected in the two breeds of cattle, were Trypanosoma congolense, T. vivax, T. brucei and T. evansi. This study, therefore, reports for the first time a natural infection of cattle with T. evansi and the use of a novel PCR in the diagnosis of trypanosome infections in cattle in Benue State, Nigeria. The determination of the ESSA and FSSA concentrations in Muturu cattle in Nigeria is also reported for the first time. The Muturu cattle have a significantly higher ESSA than the Bunaji cattle, this may be responsible for their relative trypanotolerance.

Factors influencing passive surveillance for T. b. rhodesiense human african trypanosomiasis in Uganda

INTRODUCTION

Sleeping sickness or Human African Trypanosomiasis (HAT) is a neglected tropical disease of public health importance across much of Sub-Saharan Africa. In Uganda, chronic T. b. gambiense HAT (gHAT) and acute T. b. rhodesiense HAT (rHAT) occur in two large but discrete geographical foci. Both forms are difficult to diagnose, expensive to treat and ultimately fatal in the absence of treatment. The area affected by zoonotic rHAT has been steadily expanding, placing a high burden on local health systems. HAT is a disease of neglected populations and is notorious for being under-reported. Here we examine the factors that influence passive rHAT surveillance within the district health system in four Ugandan districts into which the disease had recently been introduced, focusing on staff knowledge, infrastructure and data management.

METHODS

A mixed methods study was undertaken between 2011 and 2013 in Dokolo, Kaberamaido, Soroti and Serere districts to explore health facility capacity and clinical service provision, diagnostic capacity, HAT knowledge and case reporting. Structured interviews were undertaken with 86 medical personnel, including clinicians, nurses, midwives and technicians across 65 HC-II and HC-III medical facilities, where the health infrastructure was also directly observed. Eleven semi-structured interviews were undertaken with medical staff in each of the three designated HAT treatment facilities (Dokolo, Lwala and Serere HC-IV) in the area. HAT treatment centre case records, collected between 2009 and 2012, were analyzed.

RESULTS

Most medical staff in HC-II and HC-III facilities had been made aware of HAT from radio broadcasts, newspapers and by word of mouth, suggestive of a lack of formal training. Key knowledge as regards the causative agent, clinical signs and that HAT drugs are provided free of charge was lower amongst HC-II than HC-III staff. Many respondents did not know whether HAT was endemic in their district. In rHAT specialist treatment centres, staff were knowledgeable of HAT and were confident in their ability to diagnose and manage cases. Between 2009-2012, 342 people were diagnosed in the area, 54% in the late stage of the disease. Over the period of this study the proportion of rHAT cases identified in early stage fell and by 2012 the majority of cases identified were diagnosed in the late stage.

CONCLUSION

This study illustrates the critical role of the district health system in HAT management. The increasing proportion of cases identified at a late stage in this study indicates a major gap in lower tier levels in patient referral, diagnosis and reporting that urgently needs to be addressed. Integrating HAT diagnosis into national primary healthcare programs and providing training to medical workers at all levels is central to the new 2030 WHO HAT elimination goal. Given the zoonotic nature of rHAT, joined up active surveillance in human and animal populations in Uganda is also needed. The role of the Coordinating Office for Control of Trypanosomiasis in Uganda in implementing a One Health approach will be key to sustainable management of zoonotic HAT.

Trypanosoma brucei gambiense Infections in Mice Lead to Tropism to the Reproductive Organs, and Horizontal and Vertical Transmission

Trypanosoma brucei gambiense, transmitted by the tsetse fly, is the main causative agent of Human African trypanosomosis in West Africa and poses a significant health risk to 70 million people. Disease progression varies depending on host immunity, but usually begins with a haemo-lymphatic phase, followed by parasite invasion of the central nervous system.

In the current study, the tropism of T. b. gambiense 1135, causing a low level chronic ‘silent’ infection, was monitored in a murine model using bioluminescence imaging and PCR. A tropism to the reproductive organs, in addition to the central nervous system, after 12–18 months of infection was observed. Bioluminescent analysis of healthy females crossed with infected males showed that 50%, 62.5% and 37.5% of the female mice were subsequently positive for parasites in their ovaries, uteri and brain respectively. Although PCR confirmed the presence of parasites in the uterus of one of these mice, the blood of all mice was negative by PCR and LAMP. Subsequently, bioluminescent imaging of the offspring of infected female mice crossed with healthy males indicated parasites were present in the reproductive organs of both male (80%) and female (60%) offspring.

These findings imply that transmission of T. b. gambiense 1135 occurs horizontally, most probably via sexual contact, and vertically in a murine model, which raises the possibility of a similar transmission in humans. This has wide reaching implications. Firstly, the observations made in this study are likely to be valid for wild animals acting as a reservoir for T. b. gambiense. Also, the reproductive organs may act as a refuge for parasites during drug treatment in a similar manner to the central nervous system. This could leave patients at risk of a relapse, ultimately allowing them to act as a reservoir for subsequent transmission by tsetse and possibly, horizontally and vertically.

Human African trypanosomosis (HAT) caused by Trypanosoma brucei gambiense is a serious disease threatening 70 million people in West Africa. The parasite is transmitted by the tsetse fly, and initially multiplies in the bloodstream of the mammalian host, before progressing to the central nervous system. Using a strain of T. b. gambiense transfected with a gene for luminescent detection that causes a chronic infection with very low parasitaemia, we found that the parasite is capable of entering the reproductive organs of both male and female mice. Subsequently, crossing infected male mice with healthy females resulted in some female mice becoming infected. Furthermore, female mice infected directly with T. b. gambiense parasites and crossed with healthy males, produced offspring which were also shown to be positive for parasites. These experiments demonstrated that T. b. gambiense 1135 is transmitted both horizontally, most probably by sexual contact, and vertically in mice. If these alternate modes of transmission are analogous to the situation in humans, this has drastic implications for future control measures of HAT as parasites may avoid the immune system and treatment by accumulating in the reproductive organs as well as the CNS.

Detection and identification of pathogenic trypanosome species in tsetse flies along the Comoé River in Côte d'Ivoire

In order to identify pathogenic trypanosomes responsible for African trypanosomiasis, and to better understand tsetse-trypanosome relationships, surveys were undertaken in three sites located in different eco-climatic areas in Côte d’Ivoire during the dry and rainy seasons. Tsetse flies were caught during five consecutive days using biconical traps, dissected and microscopically examined looking for trypanosome infection. Samples from infected flies were tested by PCR using specific primers for Trypanosoma brucei s.l., T. congolense savannah type, T. congolense forest type and T. vivax. Of 1941 tsetse flies caught including four species, i.e. Glossina palpalis palpalis, G. p. gambiensis, G. tachinoides and G. medicorum, 513 (26%) were dissected and 60 (12%) were found positive by microscopy. Up to 41% of the infections were due to T. congolense savannah type, 30% to T. vivax, 20% to T. congolense forest type and 9% due to T. brucei s.l. All four trypanosome species and subgroups were identified from G. tachinoides and G. p. palpalis, while only two were isolated from G. p. gambiensis (T. brucei s.l., T. congolense savannah type) and G. medicorum (T. congolense forest, savannah types). Mixed infections were found in 25% of cases and all involved T. congolense savannah type with another trypanosome species. The simultaneous occurrence of T. brucei s.l., and tsetse from the palpalis group may suggest that human trypanosomiasis can still be a constraint in these localities, while high rates of T. congolense and T. vivax in the area suggest a potential risk of animal trypanosomiasis in livestock along the Comoé River.

Iron Homeostasis and Trypanosoma brucei Associated Immunopathogenicity Development: A Battle/Quest for Iron

African trypanosomosis is a chronic debilitating disease affecting the health and economic well-being of developing countries. The immune response during African trypanosome infection consisting of a strong proinflammatory M1-type activation of the myeloid phagocyte system (MYPS) results in iron deprivation for these extracellular parasites. Yet, the persistence of M1-type MYPS activation causes the development of anemia (anemia of chronic disease, ACD) as a most prominent pathological parameter in the mammalian host, due to enhanced erythrophagocytosis and retention of iron within the MYPS thereby depriving iron for erythropoiesis. In this review we give an overview of how parasites acquire iron from the host and how iron modulation of the host MYPS affects trypanosomosis-associated anemia development. Finally, we also discuss different strategies at the level of both the host and the parasite that can/might be used to modulate iron availability during African trypanosome infections.

Determination of the prevalence of trypanosome species in cattle from Monduli district, northern Tanzania, by loop mediated isothermal amplification

Bovine African trypanosomosis (BAT) remains one of the major vector-borne diseases with serious impediment to cattle production and economic advancement in sub-Saharan Africa. The present study evaluated the performance of the trypanosome-species-specific loop-mediated isothermal amplification (LAMP), using parasite DNA obtained from 295 indigenous Tanzanian short horn Zebu (TSHZ) and Boran crosses in Monduli district within northern Tanzania, against routine microscopy on Giemsa-stained blood films. Compared to parasitological data in which the prevalence of BAT was estimated at 2.4% (95% CI 0.7-4.1%), LAMP increased the prevalence to 27.8% (95% CI 22.3-32.5%), of which 11.9% (95% CI 8.2-15.6%) were monolytic infections with Trypanosoma vivax, while 13.6% (95% CI 9.7-17.5%) were coinfections of either T. vivax and Trypanosoma brucei subspecies or T. vivax and Trypanosoma congolense, respectively. Among the T. brucei subspecies detected, 0.7% (95% CI 0-1.7%) were human-infective Trypanosoma brucei rhodesiense. Our study is in concordance with previous reports and suggests that LAMP is a potential tool for routine diagnosis of trypanosomes in domestic animals in BAT endemic regions. According to LAMP, T. vivax seems to be the predominant trypanosome species circulating among the indigenous Monduli cattle. Importantly, the detection of T. b. rhodesiense in cattle in such wildlife-domestic-animal-human-interface areas poses a risk of contracting human African trypanosomiasis (HAT) by local communities and tourists. Continuous trypanosome surveillances in domestic animals, humans, and tsetse flies using sensitive and specific tests such as LAMP are recommended.

Equine trypanosomosis in central and western Punjab: prevalence, haemato-biochemical response and associated risk factors

The detection of Trypanosoma evansi in blood is intricate, primarily in chronic stage of infection, as the parasitaemia is often low and fluctuating. The climatic conditions of the target area of Punjab (a province of India with a total of 34,000 horses and ponies used for sports and transport) are conducive for the parasite propagation. The objective of present investigation was to assess the prevalence of T. evansi in central and western Punjab by PCR and card agglutination test (CATT/T. evansi) in relation to clinico-haematobiochemical alterations and risk factors associated with latent trypanosomosis. A total of 169 equine blood and serum samples tested by CATT/T. evansi revealed 16 cases positive, with 6.8% from central plain and 13.63% from western zone. To assess the specificity of serological test, PCR1 was performed using established primer pair TR3 5'-GCG CGG ATT CTT TGC AGA CGA-3' and TR4 5'-TGC AGA CAC TGG AAT GTT ACT-3' for T. evansi. PCR2 applied with primer pair RoTat1.2F: 5'-ATG TCA ACG ATG CCT GTT ACA TTA CGC AC-3' and RoTat1.2R: 5'-TAA ATA TCA CTG TCA AGA CCT GCT GCG G-3' to rule out the consensus between the finding of the two PCR assays and agglutination test for T. evansi, which displayed results in concordance with PCR1. PCR assays showed 1.92 and 1.51% positive samples from central plain and western zone, respectively. With respect to PCR assay, CATT/T. evansi showed 100% sensitivity and 92.1% specificity. Microscopy showed a very low prevalence rate of 0.59% with only one sample positive with teaming parasitaemia. Comparison between sexes revealed higher positivity in mares by the three tests (BSE: 0.95%, PCR: 2.88%, CATT/T. evansi: 14.42%). The haemato-biochemical factors were found to be altered in PCR positive cases, while the mean value of vital parameters lied in normal range in seropositive cases. The female horse (RR=0.0937, 95% CI=1.388-190.223%) population was found to be at the highest risk of seropositivity for T. evansi, particularly in the unorganized farms (RR=19.726, 95% CI=2.918-400.221%).

Identification of sVSG117 as an immunodiagnostic antigen and evaluation of a dual-antigen lateral flow test for the diagnosis of human African trypanosomiasis

BACKGROUND

The diagnosis of human African trypanosomiasis (HAT) caused by Trypanosoma brucei gambiense relies mainly on the Card Agglutination Test for Trypanosomiasis (CATT). There is no immunodiagnostic for HAT caused by T. b. rhodesiense. Our principle aim was to develop a prototype lateral flow test that might be an improvement on CATT.

METHODOLOGY/PRINCIPLE FINDINGS

Pools of infection and control sera were screened against four different soluble form variant surface glycoproteins (sVSGs) by ELISA and one, sVSG117, showed particularly strong immunoreactivity to pooled infection sera. Using individual sera, sVSG117 was shown to be able to discriminate between T. b. gambiense infection and control sera by both ELISA and lateral flow test. The sVSG117 antigen was subsequently used with a previously described recombinant diagnostic antigen, rISG65, to create a dual-antigen lateral flow test prototype. The latter was used blind in a virtual field trial of 431 randomized infection and control sera from the WHO HAT Specimen Biobank.

CONCLUSION/SIGNIFICANCE

In the virtual field trial, using two positive antigen bands as the criterion for infection, the sVSG117 and rISG65 dual-antigen lateral flow test prototype showed a sensitivity of 97.3% (95% CI: 93.3 to 99.2) and a specificity of 83.3% (95% CI: 76.4 to 88.9) for the detection of T. b. gambiense infections. The device was not as good for detecting T. b. rhodesiense infections using two positive antigen bands as the criterion for infection, with a sensitivity of 58.9% (95% CI: 44.9 to 71.9) and specificity of 97.3% (95% CI: 90.7 to 99.7). However, using one or both positive antigen band(s) as the criterion for T. b. rhodesiense infection improved the sensitivity to 83.9% (95% CI: 71.7 to 92.4) with a specificity of 85.3% (95% CI: 75.3 to 92.4). These results encourage further development of the dual-antigen device for clinical use.

Quantifying the association between bovine and human trypanosomiasis in newly affected sleeping sickness areas of Uganda

BACKGROUND

Uganda has active foci of both chronic and acute HAT with the acute zoonotic form of disease classically considered to be restricted to southeast Uganda, while the focus of the chronic form of HAT was confined to the northwest of the country. Acute HAT has however been migrating from its traditional disease focus, spreading rapidly to new districts, a spread linked to movement of infected cattle following restocking. Cattle act as long-term reservoirs of human infective T. b. rhodesiense showing few signs of morbidity, yet posing a significant risk to human health. It is important to understand the relationship between infected cattle and infected individuals so that an appropriate response can be made to the risk posed to the community from animals infected with human pathogens in a village setting.

METHODOLOGY/PRINCIPAL FINDINGS

This paper examines the relationship between human T. b. rhodesiense infection and human infective and non-human T. brucei s.l. circulating in cattle at village level in Kaberamaido and Dokolo Districts, Uganda. The study was undertaken in villages that had reported a case of sleeping sickness in the six months prior to sample collection and those villages that had never reported a case of sleeping sickness.

CONCLUSIONS AND SIGNIFICANCE

The sleeping sickness status of the villages had a significant effect with higher odds of infection in cattle from case than from non-case villages for T. brucei s.l. (OR: 2.94, 95%CI: 1.38-6.24). Cattle age had a significant effect (p<0.001) on the likelihood of T. brucei s.l. infection within cattle: cattle between 18-36 months (OR: 3.51, 95%CI: 1.63-7.51) and cattle over 36 months (OR: 4.20, 95%CI: 2.08-8.67) had significantly higher odds of T. brucei s. l. infection than cattle under 18 months of age. Furthermore, village human sleeping sickness status had a significant effect (p<0.05) on the detection of T. b. rhodesiense in the village cattle herd, with significantly higher likelihood of T. b. rhodesiense in the village cattle of case villages (OR: 25, 95%CI: 1.2-520.71). Overall a higher than average T. brucei s.l. prevalence (>16.3%) in a village herd over was associated with significantly higher likelihood of T. b. rhodesiense being detected in a herd (OR: 25, 95%CI: 1.2-520.71).

Facile Synthesis and Preliminary Structure-Activity Analysis of New Sulfonamides Against Trypanosoma brucei

The high throughput screening of a library of over 87,000 drug-like compounds against the African sleeping sickness parasite resulted in the discovery of hits with a wide range of molecular diversity. We report here the medicinal chemistry development of one such hit, a tetrahydroisoquinoline disulfonamide, with the synthesis and testing of 26 derivatives against the trypanosome subspecies. Activities in the 2-4 μM range were revealed with a selectivity index suitable for further development.

Molecular diagnosis in clinical parasitology: When and why?

Microscopic detection and morphological identification of parasites from clinical specimens are the gold standards for the laboratory diagnosis of parasitic infections. The limitations of such diagnostic assays include insufficient sensitivity and operator dependence. Immunoassays for parasitic antigens are not available for most parasitic infections and have not significantly improved the sensitivity of laboratory detection. Advances in molecular detection by nucleic acid amplification may improve the detection in asymptomatic infections with low parasitic burden. Rapidly accumulating genomic data on parasites allow the design of polymerase chain reaction (PCR) primers directed towards multi-copy gene targets, such as the ribosomal and mitochondrial genes, which further improve the sensitivity. Parasitic cell or its free circulating parasitic DNA can be shed from parasites into blood and excreta which may allow its detection without the whole parasite being present within the portion of clinical sample used for DNA extraction. Multiplex nucleic acid amplification technology allows the simultaneous detection of many parasitic species within a single clinical specimen. In addition to improved sensitivity, nucleic acid amplification with sequencing can help to differentiate different parasitic species at different stages with similar morphology, detect and speciate parasites from fixed histopathological sections and identify anti-parasitic drug resistance. The use of consensus primer and PCR sequencing may even help to identify novel parasitic species. The key limitation of molecular detection is the technological expertise and expense which are usually lacking in the field setting at highly endemic areas. However, such tests can be useful for screening important parasitic infections in asymptomatic patients, donors or recipients coming from endemic areas in the settings of transfusion service or tertiary institutions with transplantation service. Such tests can also be used for monitoring these recipients or highly immunosuppressed patients, so that early preemptive treatment can be given for reactivated parasitic infections while the parasitic burden is still low.

A comparative evaluation of PCR- based methods for species- specific determination of African animal trypanosomes in Ugandan cattle

Background

In recent years, PCR has been become widely applied for the detection of trypanosomes overcoming many of the constraints of parasitological and serological techniques, being highly sensitive and specific for trypanosome detection. Individual species-specific multi-copy trypanosome DNA sequences can be targeted to identify parasites. Highly conserved ribosomal RNA (rRNA) genes are also useful for comparisons between closely related species. The internal transcribed spacer regions (ITS) in particular are relatively small, show variability among related species and are flanked by highly conserved segments to which PCR primers can be designed. Individual variations in inter-species length makes the ITS region a useful marker for identification of multiple trypanosome species within a sample.

Methods

Six hundred blood samples from cattle collected in Uganda on FTA cards were screened using individual species-specific primers for Trypanosoma congolense, Trypanosoma brucei and Trypanosoma vivax and compared to a modified (using eluate extracted using chelex) ITS-PCR reaction.

Results

The comparative analysis showed that the species-specific primer sets showed poor agreement with the ITS primer set. Using species-specific PCR for Trypanozoon, a prevalence of 10.5% was observed as compared to 0.2% using ITS PCR (Kappa = 0.03). For Trypanosoma congolense, the species-specific PCR reaction indicated a prevalence of 0% compared to 2.2% using ITS PCR (Kappa = 0). For T. vivax, species-specific PCR detected prevalence of 5.7% compared to 2.8% for ITS PCR (Kappa = 0.29).

Conclusions

When selecting PCR based tools to apply to epidemiological surveys for generation of prevalence data for animal trypanosomiasis, it is recommended that species-specific primers are used, being the most sensitive diagnostic tool for screening samples to identify members of Trypanozoon (T. b. brucei s.l). While ITS primers are useful for studying the prevalence of trypanosomes causing nagana (in this study the species-specific primers did not detect the presence of T. congolense) there were discrepancies between both the species-specific primers and ITS for the detection of T. vivax.

Challenges in the control of human African trypanosomiasis in the Mpika district of Zambia

Background

Human African Trypanosomiasis is one of the Neglected Tropical Diseases that is targeted for elimination by the World Health Organization. Strong health delivery system in endemic countries is required for a control program to eliminate this disease. In Zambia, Human African Trypanosomiasis is lowly endemic in the northeastern part of the country.

Findings

We conducted a cross-sectional survey of health institutions in Mpika district in Northern Province of Zambia from 9^th to 23^rd November 2011. The aim of this study was to assess current health delivery system in the management of Human African Trypanosomiasis cases in Mpika district, Northern Province of Zambia. Ten health institutions were covered in the survey. Two structured questionnaires targeting health workers were used to collect the data on general knowledge on HAT and state of health care facilities in relation to HAT management from the surveyed health institution.

Only 46% of the 28 respondents scored more than 50% from the questionnaire on general knowledge about Human African Trypanosomiasis disease. None of the respondents knew how to differentiate the two clinical stages of Human African Trypanosomiasis disease. There were only three medical doctors to attend to all Human African Trypanosomiasis cases and other diseases at the only diagnostic and treatment hospital in Mpika district. The supply of antitrypanosomal drugs to the only treatment centre was erratic. Only one refresher course on Human African Trypanosomiasis case diagnosis and management for health staff in the district had been organized by the Ministry of Health in conjunction with the World Health Organization in the district in 2009. The referral system for suspected Human African Trypanosomiasis cases from Rural Health Centres (RHCs) to the diagnostic/treatment centre was inefficient.

Conclusions

There are a number of challenges that have been identified and need to be addressed if Human African Trypanosomiasis is to be eliminated in a lowly endemic country such as Zambia. These include shortage of trained health workers, inadequate diagnostic and treatment centres, lack of more sensitive laboratory diagnostic techniques, shortage of trypanosomicides among others discussed in detail here.

Drug resistance in African trypanosomiasis: the melarsoprol and pentamidine story

Melarsoprol and pentamidine represent the two main classes of drugs, the arsenicals and diamidines, historically used to treat the diseases caused by African trypanosomes: sleeping sickness in humans and Nagana in livestock. Cross-resistance to these drugs was first observed over 60 years ago and remains the only example of cross-resistance among sleeping sickness therapies. A Trypanosoma brucei adenosine transporter is well known for its role in the uptake of both drugs. More recently, aquaglyceroporin 2 (AQP2) loss of function was linked to melarsoprol-pentamidine cross-resistance. AQP2, a channel that appears to facilitate drug accumulation, may also be linked to clinical cases of resistance. Here, we review these findings and consider some new questions as well as future prospects for tackling the devastating diseases caused by these parasites.

Proteomic selection of immunodiagnostic antigens for human African trypanosomiasis and generation of a prototype lateral flow immunodiagnostic device

Background

The diagnosis of Human African Trypanosomiasis relies mainly on the Card Agglutination Test for Trypanosomiasis (CATT). While this test is successful, it is acknowledged that there may be room for improvement. Our aim was to develop a prototype lateral flow test based on the detection of antibodies to trypanosome antigens.

Methodology/Principal Findings

We took a non-biased approach to identify potential immunodiagnostic parasite protein antigens. The IgG fractions from the sera from Trypanosoma brucei gambiense infected and control patients were isolated using protein-G affinity chromatography and then immobilized on Sepharose beads. The IgG-beads were incubated with detergent lysates of trypanosomes and those proteins that bound were identified by mass spectrometry-based proteomic methods. This approach provided a list of twenty-four trypanosome proteins that selectively bound to the infection IgG fraction and that might, therefore, be considered as immunodiagnostic antigens. We selected four antigens from this list (ISG64, ISG65, ISG75 and GRESAG4) and performed protein expression trials in E. coli with twelve constructs. Seven soluble recombinant protein products (three for ISG64, two for ISG65 and one each for ISG75 and GRESAG4) were obtained and assessed for their immunodiagnostic potential by ELISA using individual and/or pooled patient sera. The ISG65 and ISG64 construct ELISAs performed well with respect to detecting T. b. gambiense infections, though less well for detecting T. b. rhodesiense infections, and the best performing ISG65 construct was used to develop a prototype lateral flow diagnostic device.

Conclusions/Significance

Using a panel of eighty randomized T. b. gambiense infection and control sera, the prototype showed reasonable sensitivity (88%) and specificity (93%) using visual readout in detecting T. b. gambiense infections. These results provide encouragement to further develop and optimize the lateral flow device for clinical use.

Human African Trypanosomiasis is caused by infection with Trypanosoma brucei gambiense or T. b. rhodesiense. Preliminary diagnosis of T. b. gambiense infection relies mainly on a Card Agglutination Test for Trypanosomiasis (CATT), which has acknowledged limitations. New approaches are needed, first to identify new diagnostic antigens and, second, to find a more suitable platform for field-based immunodiagnostic tests. We took an unbiased approach to identify candidate diagnostic antigens by asking which parasite proteins bind to the antibodies of infected patients and not to the antibodies of uninfected patients. From this list of twenty-four candidate antigens, we selected four and from these we selected the one that worked the best in conventional immunodiagnostic tests. This antigen, ISG65, was used to make lateral flow devices, where a small sample of patient serum is added to a pad and thirty minutes later infection can be inferred by simple optical read out. This simple prototype device works as well as the CATT test and may be developed and optimized for clinical use in the field.

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.

Trypanosome diversity in wildlife species from the serengeti and Luangwa Valley ecosystems

Background

The importance of wildlife as reservoirs of African trypanosomes pathogenic to man and livestock is well recognised. While new species of trypanosomes and their variants have been identified in tsetse populations, our knowledge of trypanosome species that are circulating in wildlife populations and their genetic diversity is limited.

Methodology/Principal Findings

Molecular phylogenetic methods were used to examine the genetic diversity and species composition of trypanosomes circulating in wildlife from two ecosystems that exhibit high host species diversity: the Serengeti in Tanzania and the Luangwa Valley in Zambia. Phylogenetic relationships were assessed by alignment of partial 18S, 5.8S and 28S trypanosomal nuclear ribosomal DNA array sequences within the Trypanosomatidae and using ITS1, 5.8S and ITS2 for more detailed analysis of the T. vivax clade. In addition to Trypanosoma brucei, T. congolense, T. simiae, T. simiae (Tsavo), T. godfreyi and T. theileri, three variants of T. vivax were identified from three different wildlife species within one ecosystem, including sequences from trypanosomes from a giraffe and a waterbuck that differed from all published sequences and from each other, and did not amplify with conventional primers for T. vivax.

Conclusions/Significance

Wildlife carries a wide range of trypanosome species. The failure of the diverse T. vivax in this study to amplify with conventional primers suggests that T. vivax may have been under-diagnosed in Tanzania. Since conventional species-specific primers may not amplify all trypanosomes of interest, the use of ITS PCR primers followed by sequencing is a valuable approach to investigate diversity of trypanosome infections in wildlife; amplification of sequences outside the T. brucei clade raises concerns regarding ITS primer specificity for wildlife samples if sequence confirmation is not also undertaken.

The trypanosomes include a number of species that cause disease in livestock. In recent years, several trypanosomes have been identified which do not fit into the classic trypanosome classification system. However, previous work has focused on trypanosomes identified in the tsetse vector, with little information available on trypanosomes found in their natural hosts, wildlife. We studied trypanosome sequences from wildlife in Serengeti National Park in Tanzania and the Luangwa Valley in Zambia and found a number of trypanosome species pathogenic to livestock were circulating in these areas. For Trypanosoma vivax, one of the causes of trypanosomiasis in cattle, variants were identified in giraffe and waterbuck that were different from all published sequences and from each other. These variants did not test positive with the molecular tests usually used to identify T. vivax suggesting that T. vivax may often be under-diagnosed in Tanzania. The trypanosome classification system is facing challenges as molecular data are incorporated into a system that historically was based on factors such as morphology, host range and geographical distribution.

Priorities for the elimination of sleeping sickness

Sleeping sickness describes two diseases, both fatal if left untreated: (i) Gambian sleeping sickness caused by Trypanosoma brucei gambiense, a chronic disease with average infection lasting around 3 years, and (ii) Rhodesian sleeping sickness caused by T. b. rhodesiense, an acute disease with death occurring within weeks of infection. Control of Gambian sleeping sickness is based on case detection and treatment involving serological screening, followed by diagnostic confirmation and staging. In stage I, patients can remain asymptomatic as trypanosomes multiply in tissues and body fluids; in stage II, trypanosomes cross the blood-brain barrier, enter the central nervous system and, if left untreated, death follows. Staging is crucial as it defines the treatment that is prescribed; for both forms of disease, stage II involves the use of the highly toxic drug melarsoprol or, in the case of Gambian sleeping sickness, the use of complex and very expensive drug regimes. Case detection of T. b. gambiense sleeping sickness is known to be inefficient but could be improved by the identification of parasites using molecular tools that are, as yet, rarely used in the field. Diagnostics are not such a problem in relation to T. b. rhodesiense sleeping sickness, but the high level of under-reporting of this disease suggests that current strategies, reliant on self-reporting, are inefficient. Sleeping sickness is one of the 'neglected tropical diseases' that attracts little attention from donors or policymakers. Proper quantification of the burden of sleeping sickness matters, as the primary reason for its 'neglect' is that the true impact of the disease is unknown, largely as a result of under-reporting. Certainly, elimination will not be achieved without vast improvements in field diagnostics for both forms of sleeping sickness especially if there is a hidden reservoir of 'chronic carriers'. Mass screening would be a desirable aim for Gambian sleeping sickness and could be handled on a national scale in the endemic countries - perhaps by piggybacking on programmes committed to other diseases. As well as improved diagnostics, the search for non-toxic drugs for stage II treatment should remain a research priority. There is good evidence that thorough active case finding is sufficient to control T. b. gambiense sleeping sickness, as there is no significant animal reservoir. Trypanosoma brucei rhodesiense sleeping sickness is a zoonosis and control involves interrupting the fly-animal-human cycle, so some form of tsetse control and chemotherapy of the animal reservoir must be involved. The restricted application of insecticide to cattle is the most promising, affordable and sustainable technique to have emerged for tsetse control. Animal health providers can aid disease control by treating cattle and, when allied with innovative methods of funding (e.g. public-private partnerships) not reliant on the public purse, this approach may prove more sustainable. Sleeping sickness incidence for the 36 endemic countries has shown a steady decline in recent years and we should take advantage of the apparent lull in incidence and aim for elimination. This is feasible in some sleeping sickness foci but must be planned and paid for increasingly by the endemic countries themselves. The control and elimination of T. b. gambiense sleeping sickness may be seen as a public good, as appropriate strategies depend on local health services for surveillance and treatment, but public-private funding mechanisms should not be excluded. It is timely to take up the tools available and invest in new tools - including novel financial instruments - to eliminate this disease from Africa.

Stoking the drug target pipeline for human African trypanosomiasis

Trypanosoma brucei is the causative agent of African sleeping sickness, putting at risk up to 50 million people in sub-Saharan Africa. Current drug therapies are limited by toxicity and difficult treatment regimes and as the development of vaccines remains unlikely, the identification of better drugs to control this deadly disease is needed. Strategies for the identification of new lead compounds include phenotypic screening or target-based approaches. Implementation of the latter has been hampered by the lack of defined targets that are both essential and druggable. In this issue of Molecular Microbiology, Jones et al. (2012) report on the characterization of T. brucei pyridoxal kinase (PdxK), an enzyme required for the salvage of vitamin B6, an essential enzymatic cofactor. Genetic knock-down and small molecule inhibitor studies were used to demonstrate that PdxK is essential for parasite growth both in vitro and in a mouse model, providing both genetic and chemical validation of the target. An enzyme assay compatible with high-throughput screening (HTS) was developed and the X-ray crystal structure solved, showing the potential for species selective inhibition. These studies add a greatly needed additional target into the drug discovery pipeline for this deadly parasitic infection.

Late stage infection in sleeping sickness

At the turn of the 19^th century, trypanosomes were identified as the causative agent of sleeping sickness and their presence within the cerebrospinal fluid of late stage sleeping sickness patients was described. However, no definitive proof of how the parasites reach the brain has been presented so far. Analyzing electron micrographs prepared from rodent brains more than 20 days after infection, we present here conclusive evidence that the parasites first enter the brain via the choroid plexus from where they penetrate the epithelial cell layer to reach the ventricular system. Adversely, no trypanosomes were observed within the parenchyma outside blood vessels. We also show that brain infection depends on the formation of long slender trypanosomes and that the cerebrospinal fluid as well as the stroma of the choroid plexus is a hostile environment for the survival of trypanosomes, which enter the pial space including the Virchow-Robin space via the subarachnoid space to escape degradation. Our data suggest that trypanosomes do not intend to colonize the brain but reside near or within the glia limitans, from where they can re-populate blood vessels and disrupt the sleep wake cycles.

Actigraphy in human African trypanosomiasis as a tool for objective clinical evaluation and monitoring: a pilot study

Background

Human African trypanosomiasis (HAT) or sleeping sickness leads to a complex neuropsychiatric syndrome with characteristic sleep alterations. Current division into a first, hemolymphatic stage and second, meningoencephalitic stage is primarily based on the detection of white blood cells and/or trypanosomes in the cerebrospinal fluid. The validity of this criterion is, however, debated, and novel laboratory biomarkers are under study. Objective clinical HAT evaluation and monitoring is therefore needed. Polysomnography has effectively documented sleep-wake disturbances during HAT, but could be difficult to apply as routine technology in field work. The non-invasive, cost-effective technique of actigraphy has been widely validated as a tool for the ambulatory evaluation of sleep disturbances. In this pilot study, actigraphy was applied to the clinical assessment of HAT patients.

Methods/Principal Findings

Actigraphy was recorded in patients infected by Trypanosoma brucei gambiense, and age- and sex-matched control subjects. Simultaneous nocturnal polysomnography was also performed in the patients. Nine patients, including one child, were analyzed at admission and two of them also during specific treatment. Parameters, analyzed with user-friendly software, included sleep time evaluated from rest-activity signals, rest-activity rhythm waveform and characteristics. The findings showed sleep-wake alterations of various degrees of severity, which in some patients did not parallel white blood cell counts in the cerebrospinal fluid. Actigraphic recording also showed improvement of the analyzed parameters after treatment initiation. Nocturnal polysomnography showed alterations of sleep time closely corresponding to those derived from actigraphy.

Conclusions/Significance

The data indicate that actigraphy can be an interesting tool for HAT evaluation, providing valuable clinical information through simple technology, well suited also for long-term follow-up. Actigraphy could therefore objectively contribute to the clinical assessment of HAT patients. This method could be incorporated into a clinical scoring system adapted to HAT to be used in the evaluation of novel treatments and laboratory biomarkers.

The clinical picture of the parasitic disease human African trypanosomiasis (HAT, also called sleeping sickness) is dominated by sleep alterations. We here used actigraphy to evaluate patients affected by the Gambiense form of HAT. Actigraphy is based on the use of battery-run, wrist-worn devices similar to watches, widely used in middle-high income countries for ambulatory monitoring of sleep disturbances. This pilot study was motivated by the fact that the use of polysomnography, which is the gold standard technology for the evaluation of sleep disorders and has greatly contributed to the objective identification of signs of disease in HAT, faces tangible challenges in resource-limited countries where the disease is endemic. We here show that actigraphy provides objective data on the severity of sleep-wake disturbances that characterize HAT. This technique, which does not disturb the patient's routine activities and can be applied at home, could therefore represent an interesting, non-invasive tool for objective HAT clinical assessment and long-term monitoring under field conditions. The use of this method could provide an adjunct marker of HAT severity and for treatment follow-up, or be evaluated in combination with other disease biomarkers in body fluids that are currently under investigation in many laboratories.

Using molecular data for epidemiological inference: assessing the prevalence of Trypanosoma brucei rhodesiense in tsetse in Serengeti, Tanzania

Background

Measuring the prevalence of transmissible Trypanosoma brucei rhodesiense in tsetse populations is essential for understanding transmission dynamics, assessing human disease risk and monitoring spatio-temporal trends and the impact of control interventions. Although an important epidemiological variable, identifying flies which carry transmissible infections is difficult, with challenges including low prevalence, presence of other trypanosome species in the same fly, and concurrent detection of immature non-transmissible infections. Diagnostic tests to measure the prevalence of T. b. rhodesiense in tsetse are applied and interpreted inconsistently, and discrepancies between studies suggest this value is not consistently estimated even to within an order of magnitude.

Methodology/Principal Findings

Three approaches were used to estimate the prevalence of transmissible Trypanosoma brucei s.l. and T. b. rhodesiense in Glossina swynnertoni and G. pallidipes in Serengeti National Park, Tanzania: (i) dissection/microscopy; (ii) PCR on infected tsetse midguts; and (iii) inference from a mathematical model. Using dissection/microscopy the prevalence of transmissible T. brucei s.l. was 0% (95% CI 0–0.085) for G. swynnertoni and 0% (0–0.18) G. pallidipes; using PCR the prevalence of transmissible T. b. rhodesiense was 0.010% (0–0.054) and 0.0089% (0–0.059) respectively, and by model inference 0.0064% and 0.00085% respectively.

Conclusions/Significance

The zero prevalence result by dissection/microscopy (likely really greater than zero given the results of other approaches) is not unusual by this technique, often ascribed to poor sensitivity. The application of additional techniques confirmed the very low prevalence of T. brucei suggesting the zero prevalence result was attributable to insufficient sample size (despite examination of 6000 tsetse). Given the prohibitively high sample sizes required to obtain meaningful results by dissection/microscopy, PCR-based approaches offer the current best option for assessing trypanosome prevalence in tsetse but inconsistencies in relating PCR results to transmissibility highlight the need for a consensus approach to generate meaningful and comparable data.

Human African trypanosomiasis is a fatal disease that is carried by a tsetse vector. Assessing the proportion of tsetse which carries human-infective trypanosomes is important in assessing human disease risk and understanding disease transmission dynamics. However, identifying flies which carry transmissible infections is difficult, due to potential presence of other trypanosome species in the same fly, and concurrent detection of immature infections which are not transmissible. We used three methods to estimate the proportion of flies carrying human-infective trypanosomes: dissection and microscopic examination of flies to visualise trypanosomes directly in the fly; PCR of fly midguts in which trypanosomes were observed by microscopy; and theoretical analysis using a mathematical model of disease transmission. All three methods found the prevalence to be extremely low. Given the low prevalence, dissection/microscopy requires prohibitively large sample sizes and therefore PCR-based approaches are likely to be of most value. However, interpretation of PCR data is not straightforward; whilst PCR identifies flies carrying pathogen genetic material it does not directly identify flies with transmissible infections. This study highlights the need for a consensus approach on the analysis and interpretation of PCR data to generate reliable and comparable measures of the proportion of flies which carry transmissible human-infective trypanosomes.