The impact of human immunodeficiency virus infection on the epidemiology and treatment of Trypanosoma brucei gambiense sleeping sickness in Nioki, Zaire

Tissue Parasites in HIV Infection

PURPOSE OF REVIEW

The purpose of this review is to discuss the current knowledge of HIV and tissue parasite co-infection in the context of transmission enhancement, clinical characteristics, treatment, relapse, and clinical outcomes.

RECENT FINDINGS

The pathophysiology and clinical sequelae of tissue parasites in people living with HIV (PLWH) have been well described for only a handful of organisms, primarily protozoa such as malaria and leishmaniasis. Available published data indicate that the interactions between HIV and tissue parasites are highly variable depending on the infecting organism and the degree of host immunosuppression. Some tissue parasites, such as Schistosoma species, are known to facilitate the transmission of HIV. Conversely, uncontrolled HIV infection can lead to the earlier and more severe presentation of a variety of tissue parasites and can make treatment more challenging. Although much investigation remains to be done to better understand the interactions between consequences of HIV and tissue parasite co-infection, it is important to disseminate the current knowledge on this topic to health care providers in order to prevent, treat, and control infections in PLWH.

Tropical Parasitic Infections in Individuals Infected with HIV

PURPOSE OF REVIEW

Neglected tropical diseases share both geographic and socio-behavioral epidemiological risk factors with HIV infection. In this literature review, we describe interactions between parasitic diseases and HIV infection, with a focus on the impact of parasitic infections on HIV infection risk and disease progression, and the impact of HIV infection on clinical characteristics of tropical parasitic infections. We limit our review to tropical parasitic infections of the greatest public health burden, and exclude discussion of classic HIV-associated opportunistic infections that have been well reviewed elsewhere.

RECENT FINDINGS

Tropical parasitic infections, HIV-infection, and treatment with antiretroviral therapy alter host immunity, which can impact susceptibility, transmissibility, diagnosis, and severity of both HIV and parasitic infections. These relationships have a broad range of consequences, from putatively increasing susceptibility to HIV acquisition, as in the case of schistosomiasis, to decreasing risk of protozoal infections through pharmacokinetic interactions between antiretroviral therapy and antiparasitic agents, as in the case of malaria. However, despite this intimate interplay in pathophysiology and a broad overlap in epidemiology, there is a general paucity of data on the interactions between HIV and tropical parasitic infections, particularly in the era of widespread antiretroviral therapy availability.

SUMMARY

Additional data are needed to motivate clinical recommendations for detection and management of parasitic infections in HIV-infected individuals, and to consider the implications of and potential opportunity granted by HIV treatment programs on parasitic disease control.

Revisiting zoonotic human African trypanosomiasis control in Uganda

OBJECTIVES

Human migration and concomitant HIV infections are likely to bring about major changes in the epidemiology of zoonotic parasitic infections. Human African trypanosomiasis (HAT) control is particularly fraught with intricacies. The primarily zoonotic form, T.b. rhodesiense, and the non-zoonotic T.b. gambiense co-exist in Northern Uganda, leading to a potential geographic and genetic overlap of the two foci. This region also has the highest HIV prevalence in Uganda plus poor food security. We examine the bottlenecks facing the control program in a changed political and economic context.

METHOD

We searched the literature in July 2015 using three databases: MEDLINE, Google Scholar, and Web of Science.

FINDINGS

Decentralized zoonotic HAT control for animal reservoirs and vectors compromise sustainability of the control programs. Human transmission potential may be underestimated in a region with other endemic diseases and where an HIV-HAT epidemic, could merge two strains.

CONCLUSION

Our comprehensive literature review concludes that enhanced collaboration is imperative not only between human and animal health specialists, but also with political science. Multi-sectorial collaborations may need to be nurtured within existing operational national HIV prevention frameworks, with an integrated surveillance framework.

Clinical profiles, disease outcome and co-morbidities among T. b. rhodesiense sleeping sickness patients in Uganda

Background

The acute form of Human African Trypanosomiasis (HAT, also known as Sleeping sickness) caused by Trypanosoma brucei rhodesiense has been shown to have a wide spectrum of focus specific clinical presentation and severity in East and Southern Africa. Indeed HAT occurs in regions endemic for other tropical diseases, however data on how these co-morbidities might complicate the clinical picture and affect disease outcome remains largely scanty. We here describe the clinical presentation, presence of co-infections, and how the latter impact on HAT prognosis.

Methods and Findings

We carried out a retrospective analysis of clinical data from 258 sleeping sickness patients reporting to Lwala hospital between 2005 and 2012. The mean patient age was 28.6 years with a significant number of cases below 18 years (p< 0.0001). About 93.4% of the cases were diagnosed as late stage (p< 0.0001). The case fatality rate was 10.5% with post treatment reactive encephalopathys reported in 7.9% of the cases, of whom 36.8% eventually died. Fever was significantly (p = 0.045) higher in patients under 18 years. Of the early stage patients, 26.7% and 6.7% presented with late stage signs of sleep disorder and mental confusion respectively. Among the co-infections, malaria was significantly more prevalent (28.9%; p< 0.0001) followed by urinary tract infections (4.2%). Co-infections were present in 14.3% of in-hospital deaths, 38.5% of which were recorded as Malaria. Malaria was significantly more common in patients under 18 years (45.5%; p< 0.02), and was reported in 60% of the fatal cases in this age group.

Conclusions

We show a wide spectrum of sleeping sickness clinical presentation and disease outcome that was apparently not significantly influenced by concurrent infections. It would thus be interesting to determine the host and/or parasite factors that might be responsible for the observed diverse clinical presentation.

Melarsoprol sensitivity profile of Trypanosoma brucei gambiense isolates from cured and relapsed sleeping sickness patients from the Democratic Republic of the Congo

BACKGROUND

Sleeping sickness caused by Trypanosoma brucei (T.b.) gambiense constitutes a serious health problem in sub-Sahara Africa. In some foci, alarmingly high relapse rates were observed in patients treated with melarsoprol, which used to be the first line treatment for patients in the neurological disease stage. Particularly problematic was the situation in Mbuji-Mayi, East Kasai Province in the Democratic Republic of the Congo with a 57% relapse rate compared to a 5% relapse rate in Masi-Manimba, Bandundu Province. The present study aimed at investigating the mechanisms underlying the high relapse rate in Mbuji-Mayi using an extended collection of recently isolated T.b. gambiense strains from Mbuji-Mayi and from Masi-Manimba.

METHODOLOGY/PRINCIPAL FINDINGS

Forty five T.b. gambiense strains were used. Forty one were isolated from patients that were cured or relapsed after melarsoprol treatment in Mbuji-Mayi. In vivo drug sensitivity tests provide evidence of reduced melarsoprol sensitivity in these strains. This reduced melarsoprol sensitivity was not attributable to mutations in TbAT1. However, in all these strains, irrespective of the patient treatment outcome, the two aquaglyceroporin (AQP) 2 and 3 genes are replaced by chimeric AQP2/3 genes that may be associated with resistance to pentamidine and melarsoprol. The 4 T.b. gambiense strains isolated in Masi-Manimba contain both wild-type AQP2 and a different chimeric AQP2/3. These findings suggest that the reduced in vivo melarsoprol sensitivity of the Mbuji-Mayi strains and the high relapse rates in that sleeping sickness focus are caused by mutations in the AQP2/AQP3 locus and not by mutations in TbAT1.

CONCLUSIONS/SIGNIFICANCE

We conclude that mutations in the TbAQP2/3 locus of the local T.b. gambiense strains may explain the high melarsoprol relapse rates in the Mbuji-Mayi focus but other factors must also be involved in the treatment outcome of individual patients.

Mechanisms of interaction between protozoan parasites and HIV

PURPOSE OF REVIEW

This review summarizes the current knowledge on human immunodeficiency virus type 1 (hereinafter called HIV)/protozoan co-infections in the case of three important, although neglected, tropical diseases: malaria, trypanosomiasis (Chagas disease) and leishmaniasis. The HIV pandemic has modified the immunopathogenic, epidemiological and therapeutic aspects of these human diseases.

RECENT FINDINGS

In-vitro data suggests that HIV favors Leishmania infection, whereas different parasites have contrasting effects on HIV. However, many of the previous models are a limited representation of the complex interactions within the host; this situation is particularly the case when microbial products are used in place of live parasites.

SUMMARY

In the host, protozoan parasites generally enhance HIV replication and accelerate AIDS progression. HIV alters parasite pathogenesis, often worsening disease outcome. These aspects bring significant complications for the treatment of co-infected individuals.

HIV-1 replication in monocyte-derived dendritic cells is stimulated by melarsoprol, one of the main drugs against human African trypanosomiasis

Human African trypanosomiasis (HAT) is a disease caused by the protozoan parasite Trypanosoma brucei, the causative agent of sleeping sickness that is still endemic in well defined regions of sub-Saharan Africa. Co-infections with this human pathogen and human immunodeficiency virus (HIV) are not uncommon, but their potential interaction has been little studied. The organo-arsenical drug melarsoprol has been widely used for the treatment of late stage trypanosomiasis since the early 1950s and is still widely used despite very serious adverse effects. Because arsenic trioxide, another trivalent arsenical structurally related to melarsoprol, has been shown to markedly increase HIV replication in dendritic cells (DCs), we tested the effect of melarsoprol on virus replication in various primary human immune cell types, including DCs. We show here that this medicinal drug stimulates the replication of several strains of HIV-1, specifically in monocyte-derived DCs, and also renders such cells susceptible to HIV-2 infection. The drug acts mainly through an increase in the efficacy of the reverse transcription process, and this effect is mediated, at least partly, by an inhibition of expression of the cellular restriction factor APOBEC3G. These observations raise concerns about the harmful effect that melarsoprol might exert on the natural history of HIV in co-infected patients and on virus transmission.

Prevalence and types of coinfections in sleeping sickness patients in kenya (2000/2009)

The occurrence of coinfections in human African trypanosomiasis (HAT) patients was investigated using a retrospective data of hospital records at the National Sleeping Sickness Referral Hospital in Alupe, Kenya. A total of 31 patients, 19 males and 12 females, were diagnosed with HAT between the years 2000 and 2009. The observed co-infections included malaria (100%), helminthosis (64.5%), typhoid (22.5%), urinary tract infections (16.1%), HIV (12.9%), and tuberculosis (3.2%). The species of helminthes observed included Ancylostoma duodenale (38.7%), Ascaris lumbricoides (45.7%), Strongyloides stercoralis (9.7%), and Taenia spp. (3.2%). The patients were also infected with Entamoeba spp. (32.3%) and Trichomonas hominis (22.6%) protozoan parasites. The main clinical signs observed at the point of admission included headache (74.2%), fever (48.4%), sleep disorders (45.2%), and general body pain (41.9%). The HAT patients were treated with suramin (early stage, 9/31) and melarsoprol (late stage, 22/31). In conclusion, the study has shown that HAT patients have multiple co-infections which may influence the disease pathogenesis and complicate management of HAT.

Clinical presentation of T.b. rhodesiense sleeping sickness in second stage patients from Tanzania and Uganda

Background

A wide spectrum of disease severity has been described for Human African Trypanosomiasis (HAT) due to Trypanosoma brucei rhodesiense (T.b. rhodesiense), ranging from chronic disease patterns in southern countries of East Africa to an increase in virulence towards the north. However, only limited data on the clinical presentation of T.b. rhodesiense HAT is available. From 2006-2009 we conducted the first clinical trial program (Impamel III) in T.b. rhodesiense endemic areas of Tanzania and Uganda in accordance with international standards (ICH-GCP). The primary and secondary outcome measures were safety and efficacy of an abridged melarsoprol schedule for treatment of second stage disease. Based on diagnostic findings and clinical examinations at baseline we describe the clinical presentation of T.b. rhodesiense HAT in second stage patients from two distinct geographical settings in East Africa.

Methodology/Principal Findings:

138 second stage patients from Tanzania and Uganda were enrolled. Blood samples were collected for diagnosis and molecular identification of the infective trypanosomes, and T.b. rhodesiense infection was confirmed in all trial subjects. Significant differences in diagnostic parameters and clinical signs and symptoms were observed: the median white blood cell (WBC) count in the cerebrospinal fluid (CSF) was significantly higher in Tanzania (134cells/mm³) than in Uganda (20cells/mm³; p<0.0001). Unspecific signs of infection were more commonly seen in Uganda, whereas neurological signs and symptoms specific for HAT dominated the clinical presentation of the disease in Tanzania. Co-infections with malaria and HIV did not influence the clinical presentation nor treatment outcomes in the Tanzanian study population.

Conclusions/Significance

We describe a different clinical presentation of second stage T.b. rhodesiense HAT in two distinct geographical settings in East Africa. In the ongoing absence of sensitive diagnostic tools and safe drugs to diagnose and treat second stage T.b. rhodesiense HAT an early identification of the disease is essential. A detailed understanding of the clinical presentation of T.b. rhodesiense HAT among health personnel and affected communities is vital, and awareness of regional characteristics, as well as implications of co-infections, can support decision making and differential diagnosis.

Sleeping sickness, or Human African Trypanosomiasis (HAT), caused by Trypanosoma brucei rhodesiense is one of the most neglected tropical diseases. It affects mainly rural, poor East African populations and has very high socio-economic impacts. T.b. rhodesiense HAT is an acute disease; patients quickly progress from the first stage, where trypanosomes are detectable in blood and lymph, to the second stage, where parasites penetrate the central nervous system. If left untreated, T.b. rhodesiense HAT is fatal. Disease control is hampered by the absence of sensitive diagnostic tools and safe drugs. Second stage patients can only be treated with melarsoprol, a highly toxic, arsenical drug. It is more difficult to treat patients successfully at advanced stages of the disease, and late onset of treatment should be avoided. Yet, most patients are treated for other conditions prior to HAT diagnosis. Therefore, it is important that health personnel in T.b. rhodesiense endemic regions have a detailed understanding of the clinical presentation of the disease and consider regional characteristics of T.b. rhodesiense HAT for decision making and differential diagnosis.

Low specificities of HIV diagnostic tests caused by Trypanosoma brucei gambiense sleeping sickness

The accuracy of diagnostic tests for HIV in patients with tropical infections is poorly documented. Human African trypanosomiasis (HAT) is characterized by a polyclonal B-cell activation, constituting a risk for false-positive reactions to diagnostic tests, including HIV tests. A retrospective study of the accuracy of HIV diagnostic tests was performed with 360 human African HAT patients infected with Trypanosoma brucei gambiense before treatment and 163 T. b. gambiense-infected patients 2 years after successful treatment in Mbuji Mayi, East Kasai, Democratic Republic of the Congo. The sensitivities, specificities, and positive predictive values (PPVs) of individual tests and algorithms consisting of 3 rapid tests were determined. The sensitivity of all tests was 100% (11/11). The low specificity (96.3%, 335/348) and PPV (45.8%, 11/24) of a classical seroconfirmation strategy (Vironostika enzyme-linked immunosorbent assay [ELISA] followed by line immunoassay) complicated the determination of HIV status, which had to be determined by PCR. The specificities of the rapid diagnostic tests were 39.1% for Determine (136/348); 85.3 to 92.8% (297/348 to 323/348) for Vikia, ImmunoFlow, DoubleCheck, and Bioline; and 96.6 to 98.3% (336/348 to 342/348) for Uni-Gold, OraQuick, and Stat-Pak. The specificity of Vironostika was 67.5% (235/348). PPVs ranged between 4.9 and 64.7%. Combining 3 different rapid tests resulted in specificities of 98.3 to 100% (342/348 to 348/348) and PPVs of 64.7 to 100% (11/17 to 11/11). For cured HAT patients, specificities were significantly higher for Vironostika, Determine, Uni-Gold, and ImmunoFlow. T. b. gambiense infection decreases the specificities of antibody detection tests for HIV diagnosis. Unless tests have been validated for interference with HAT, HIV diagnosis using classical algorithms in untreated HAT patients should be avoided. Specific, validated combinations of 3 HIV rapid tests can increase specificity.

Cerebrospinal fluid B lymphocyte identification for diagnosis and follow-up in human African trypanosomiasis in the field

OBJECTIVES

In human African trypanosomiasis (HAT, sleeping sickness), staging of disease and treatment follow-up relies on white cell count in the cerebrospinal fluid (CSF). As B lymphocytes (CD19 positive cells) are not found in the CSF of healthy individuals but occur in neurological disorders such as multiple sclerosis, B lymphocyte count may be useful for field diagnosis/staging and therapeutic follow-up in HAT.

METHODS

Seventy-one HAT patients were diagnosed and 50 were followed-up 6-24 months after treatment. White cell counts were used for conventional staging (stage 1, < or =5 cells/microl CSF, n = 42; stage 2, > or =20 cells/microl, n = 16) and intermediate stage (6-19 cells/microl, n = 13). Slides containing 1 microl of CSF mixed with Dynabeads CD19 pan B were examined microscopically to detect B cell rosettes (bound to at least four beads).

RESULTS

Stage 1 patients exhibited zero (n = 37) or one CSF rosette/microl (n = 5), contrary to most stage 2 patients (14/16: > or =2 rosettes/microl). Intermediate stage patients expressed 0 (n = 9), 1 (n = 3) or 2 (n = 1) rosettes/microl of CSF. During follow-up, rosette counts correlated with white cell count staging but were much easier to read.

CONCLUSION

B cell rosettes being easily detected in the CSF in field conditions may be proposed to replace white cell count for defining HAT stages 1 and 2 and limit uncertainty in treatment decision in patients with intermediate stage.

Parasitic central nervous system infections in immunocompromised hosts: malaria, microsporidiosis, leishmaniasis, and African trypanosomiasis

Immunosuppression associated with HIV infection or following transplantation increases susceptibility to central nervous system (CNS) infections. Because of increasing international travel, parasites that were previously limited to tropical regions pose an increasing infectious threat to populations at risk for acquiring opportunistic infection, especially people with HIV infection or individuals who have received a solid organ or bone marrow transplant. Although long-term immunosuppression caused by medications such as prednisone likely also increases the risk for acquiring infection and for developing CNS manifestations, little published information is available to support this hypothesis. In an earlier article published in Clinical Infectious Diseases, we described the neurologic manifestations of some of the more common parasitic CNS infections. This review will discuss the presentation, diagnosis, and treatment of the following additional parasitic CNS infections: malaria, microsporidiosis, leishmaniasis, and African trypanosomiasis.

The impact of HIV infection on tropical diseases

HIV and tropical infections affect each other mutually. HIV infection may alter the natural history of tropical infectious diseases, impede rapid diagnosis, or reduce the efficacy of antiparasitic treatment. Tropical infections may facilitate the transmission of HIV and accelerate progression from asymptomatic HIV infection to AIDS. This article reviews data on known interactions for malaria, leishmaniasis, human African trypanosomiasis, Chagas' disease, schistosomiasis, onchocerciasis, lymphatic filariasis, and intestinal helminthiases.

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.

Treatment perspectives for human African trypanosomiasis

Human African trypanosomiasis (HAT), or sleeping sickness, is currently on the rise. HAT develops in two stages, the first involving the hemolymphatic system, and the second, the neurological system. Left untreated, HAT is invariably fatal. There have been no therapeutic advances in more than 40 years. Stage 1 can be treated with pentamidine and suramin, but stage 2 can only be treated with melarsoprol, a toxic arsenic derivative that has a 2-12% incidence of fatal side-effects (encephalopathy). Eflornithine has never achieved widespread use because it is difficult to administer under field conditions. Nifurtimox has been used successfully in the treatment of American trypanosomiasis, or Chagas disease, but only in small studies or as a compassionate use treatment. There is little research and development for new drugs in this area: only one prodrug is in the clinical development phase, a pentamidine analog that offers hope for the replacement of injectable pentamidine with an orally administered drug. Current efforts appear to be focused on reevaluating older drugs. A course of treatment with melarsoprol for 10 days at 2.2 mg/kg/day is now in the multicenter evaluation phase. Orally administered eflornithine is also slated for reevaluation. In addition, studies of drug combinations are recommended to determine possible combined or synergistic effects and find ways to reduce toxicity.

HIV infection and tropical parasitic diseases - deleterious interactions in both directions?

HIV and parasitic infections interact and affect each other mutually. Whereas HIV infection may alter the natural history of parasitic diseases, impede rapid diagnosis or reduce the efficacy of antiparasitic treatment, parasitoses may facilitate the infection with HIV as well as the progression from asymptomatic infection to AIDS. We review data on known interactions for malaria, leishmaniasis, Human African Trypanosomiasis, Chagas' disease, onchocerciasis, lymphatic filariasis, schistosomiasis and intestinal helminthiases. The common immunopathogenetic basis for the deleterious effects parasitic diseases may have on the natural history of HIV infection seems to be a particular type of chronic immune activation and a preferential activation of the T helper (Th)2 type of help. Control of parasitic diseases should complement the tools currently used in combating the HIV pandemic.

Leishmania, Trypanosoma and monoxenous trypanosomatids as emerging opportunistic agents

Immunosuppression is associated with the occurrence of a large variety of infections, several of them due to opportunistic protozoa. The parasitic protozoa of the family Trypanosomatidae vary greatly in their importance as potential opportunistic pathogens. African trypanosomiasis is no more common nor severe during AIDS. The situation with Chagas' disease, however, is much different. Although the process is not clearly understood, there appears to be a reactivation of Trypanosoma cruzi infection, which can lead to severe meningoencephalitis. In persons with AIDS, leishmaniasis is often exacerbated, particularly Leishmania infantum, which causes visceral leishmaniasis in southern Europe. Since 1990, 1,616 cases of visceral leishmaniasis/HIV co-infection have been reported, mainly from southern Europe, and particularly from Spain, southern France, and Italy. The co-infected patients are primarily young adults and belong to the risk group of intravenous drug users. Isoenzymatic identification of 272 isolates showed 18 different L. infantum zymodemes, of which 10 represent new zymodemes hitherto found only during HIV co-infection. New foci of co-infection are emerging in various parts of the world, including Brazil and East Africa. Moreover, since 1995, non-human monoxenous trypanosomatids have been found in AIDS patients, causing both diffuse cutaneous lesions and visceral infections. In countries where visceral leishmaniasis is endemic, particularly in southern Europe, immunosuppressive treatments for organ transplants or malignant diseases often result either in reactivation of asymptomatic visceral leishmaniasis or in facilitation of new infections.

Human immunodeficiency virus infection and human African trypanosomiasis: a case-control study in Côte d'Ivoire

To assess the association between human immunodeficiency virus (HIV) infection and human African trypanosomiasis (HAT) in Côte d'Ivoire, West Africa, a cross-sectional case-control study was conducted on 301 HAT patients recruited in the main foci of the country. For each HAT patient, 3 controls, matched for sex, age and residence, were selected. Data relating to socio-demographic factors and potential risk factors for Trypanosoma brucei gambiense and HIV infections were obtained, and serum samples were collected for HIV-1 and HIV-2 tests. A positive test consisted of enzyme immunoassay reactive to HIV-1, HIV-2 or both and confirmed by a synthetic peptide test or Western blot. Data were analyzed using conditional logistic regression with EGRET software. No statistically significant difference was found between the prevalence of HIV infection in HAT patients and controls (4.3% and 3.5% respectively; crude odds ratio (OR) 1.28, 95% confidence interval (CI) 0.65-2.50). In multivariate analysis, allowance for 5 covariates did not change the association between the 2 infections (adjusted OR 1.27, 95% CI 0.64-2.52). Although this study had limited statistical power, no significant association was found between HIV infection and T.b. gambiense infection in rural Côte d'Ivoire. Studies are needed to determine whether HIV infection influences the clinical course of HAT, a question not addressed in the present study.

Efficacy and toxicity of eflornithine for treatment of Trypanosoma brucei gambiense sleeping sickness

The usual first-line treatment for Trypanosoma brucei gambiense sleeping sickness is melarsoprol, but when that fails the outlook has hitherto been grim. The polyamine synthesis inhibitor eflornithine (difluoromethylornithine, DFMO) has emerged as an alternative therapy. 207 patients with late-stage T b gambiense sleeping sickness were treated in rural Zaire with three different regimens of DFMO in an open-trial design. During treatment, trypanosomes disappeared from the CSF of all 87 patients in whom parasites had been seen before DFMO administration, and there was a sharp fall in CSF white cell count from a mean of 186/microliters to 21/microliters. 152 patients have been followed for at least a year after DFMO treatment, and only 13 (9%) have relapsed. Treatment failures were more common in children less than 12 years, among patients treated with oral DFMO only, and among patients who received DFMO as the initial treatment of their recently diagnosed trypanosomiasis. Toxicity was acceptable. Only 4 patients died during or shortly after treatment. Bone marrow suppression resulting in anaemia (43%) or leucopenia (53%) was common but bore little consequence. This open trial shows that DFMO is as active as and possibly less toxic than melarsoprol. For economic and logistic reasons DFMO may not be the first-choice therapy in rural Africa but for the vast majority of patients who relapse after melarsoprol DFMO will be curative.

Interactions between immunity and chemotherapy in the treatment of the trypanosomiases and leishmaniases

The immune status of a host infected with Trypanosoma spp. or Leishmania spp. can play an important role in successful chemotherapy. In animal models, treatment of African trypanosomiasis with difluoromethylornithine or melarsoprol requires an appropriate antibody-mediated immune response. An intact immune system is also necessary for rapid clearance of trypanosomes from the bloodstream following treatment with suramin or quinapyramine. Similarly, an efficient cell-mediated immune responses is required for maximal efficacy of pentavalent antimonials in the treatment of leishmaniasis. However, the potential relationship between parasite-induced or acquired immunosuppression and effective chemotherapy has been poorly studied. Macrophages which have been activated by bacterial cell wall components or gamma-interferon are known to display increased activity against Leishmania donovani or Trypanosoma cruzi. In experimental and clinical visceral leishmaniasis, use of macrophage activators together with pentavalent antimonials has lowered the dose of antimony required to cure the infection.