Polysomnography as a diagnosis and post-treatment follow-up tool in human African trypanosomiasis: A case study in an infant

Sleeping Sickness: A Tale of Two Clocks

Sleeping sickness is caused by a eukaryotic unicellular parasite known to infect wild animals, cattle, and humans. It causes a fatal disease that disrupts many rhythmic physiological processes, including daily rhythms of hormonal secretion, temperature regulation, and sleep, all of which are under circadian (24-h) control. In this review, we summarize research on sleeping sickness parasite biology and the impact it has on host health. We also consider the possible evolutionary advantages of sleep and circadian deregulation for the parasite.

Sleep and brain infections

Sleep is frequently altered in systemic infections as a component of sickness behavior in response to inflammation. Sleepiness in sickness behavior has been extensively investigated. Much less attention has instead been devoted to sleep and wake alterations in brain infections. Most of these, as other neuroinfections, are prevalent in sub-Saharan Africa. The present overview highlights the importance of this topic from both the clinical and pathogenetic points of view. Vigilance states and their regulation are first summarized, emphasizing that key nodes in this distributed brain system can be targeted by neuroinflammatory signaling. Sleep-wake changes in the parasitic disease human African trypanosomiasis (HAT) and its animal models are then reviewed and discussed. Experimental data have revealed that the suprachiasmatic nucleus, the master circadian pacemaker, and peptidergic cell populations of the lateral hypothalamus (the wake-promoting orexin neurons and the sleep-promoting melanin-concentrating hormone neurons) are targeted by African trypanosome infection. It is then discussed how prominent and disturbing are sleep changes in HIV/AIDS, also when the infection is cured with antiretroviral therapy. This recalls attention on the bidirectional interactions between sleep and immune system, including the specialized brain immune response of which microglial cells are protagonists. Sleep changes in an ancient viral disease, rabies, and in the emerging infection due to Zika virus which causes a congenital syndrome, are also dealt with. Altogether the findings indicate that sleep-wake regulation is targeted by brain infections caused by different pathogens and, although the relevant pathogenetic mechanisms largely remain to be clarified, these alterations differ from hypersomnia occurring in sickness behavior. Thus, brain infections point to the vulnerability of the neural network of sleep-wake regulation as a highly relevant clinical and basic science challenge.

Neural Damage in Experimental Trypanosoma brucei gambiense Infection: The Suprachiasmatic Nucleus

Trypanosoma brucei (T. b.) gambiense is the parasite subspecies responsible for most reported cases of human African trypanosomiasis (HAT) or sleeping sickness. This severe infection leads to characteristic disruption of the sleep-wake cycle, recalling attention on the circadian timing system. Most animal models of the disease have been hitherto based on infection of laboratory rodents with the T. b. brucei subspecies, which is not infectious to humans. In these animal models, functional, rather than structural, alterations of the master circadian pacemaker, the hypothalamic suprachiasmatic nucleus (SCN), have been reported. Information on the SCN after infection with the human pathogenic T. b. gambiense is instead lacking. The present study was aimed at the examination of the SCN after T. b. gambiense infection of a susceptible rodent, the multimammate mouse, Mastomys natalensis, compared with T. b. brucei infection of the same host species. The animals were examined at 4 and 8 weeks post-infection, when parasites (T. b. gambiense or T. b. brucei) were detected in the brain parenchyma, indicating that the disease was in the encephalitic stage. Neuron and astrocyte changes were examined with Nissl staining, immunophenotyping and quantitative analyses. Interestingly, significant neuronal loss (about 30% reduction) was documented in the SCN during the progression of T. b. gambiense infection. No significant neuronal density changes were found in the SCN of T. b. brucei-infected animals. Neuronal cell counts in the hippocampal dentate gyrus of T. b. gambiense-infected M. natalensis did not point out significant changes, indicating that no widespread neuron loss had occurred in the brain. Marked activation of astrocytes was detected in the SCN after both T. b. gambiense and T. b. brucei infections. Altogether the findings reveal that neurons of the biological clock are highly susceptible to the infection caused by human pathogenic African trypanosomes, which have the capacity to cause permanent partial damage of this structure.

Sleeping sickness is a circadian disorder

Sleeping sickness is a fatal disease caused by Trypanosoma brucei, a unicellular parasite that lives in the bloodstream and interstitial spaces of peripheral tissues and the brain. Patients have altered sleep/wake cycles, body temperature, and endocrine profiles, but the underlying causes are unknown. Here, we show that the robust circadian rhythms of mice become phase advanced upon infection, with abnormal activity occurring during the rest phase. This advanced phase is caused by shortening of the circadian period both at the behavioral level as well as at the tissue and cell level. Period shortening is T. brucei specific and independent of the host immune response, as co-culturing parasites with explants or fibroblasts also shortens the clock period, whereas malaria infection does not. We propose that T. brucei causes an advanced circadian rhythm disorder, previously associated only with mutations in clock genes, which leads to changes in the timing of sleep.

African sleeping sickness is well known for the alterations of sleeping patterns, but it is not known how circadian biology is altered by the causative pathogen Trypanosoma brucei. Here the authors show T. brucei causes a disorder of the cellular circadian clock that is unrelated to the immune response to the parasite.

Human African trypanosomiasis

Human African trypanosomiasis (sleeping sickness) is a parasitic infection that almost invariably progresses to death unless treated. Human African trypanosomiasis caused devastating epidemics during the 20th century. Thanks to sustained and coordinated efforts over the past 15 years, the number of reported cases has fallen to an historically low level. Fewer than 3000 cases were reported in 2015, and the disease is targeted for elimination by WHO. Despite these recent successes, the disease is still endemic in parts of sub-Saharan Africa, where it is a considerable burden on rural communities, most notably in central Africa. Since patients are also reported from non-endemic countries, human African trypanosomiasis should be considered in differential diagnosis for travellers, tourists, migrants, and expatriates who have visited or lived in endemic areas. In the absence of a vaccine, disease control relies on case detection and treatment, and vector control. Available drugs are suboptimal, but ongoing clinical trials provide hope for safer and simpler treatments.

Clinical features, diagnosis, and treatment of human African trypanosomiasis (sleeping sickness)

Human African trypanosomiasis, or sleeping sickness, is caused by infection with parasites of the genus Trypanosoma, transmitted by the tsetse fly. The disease has two forms, Trypanosoma brucei (T b) rhodesiense and T b gambiense; and is almost always fatal if untreated. Despite a recent reduction in the number of reported cases, patients with African trypanosomiasis continue to present major challenges to clinicians. Because treatment for CNS-stage disease can be very toxic, diagnostic staging to distinguish early-stage from late-stage disease when the CNS in invaded is crucial but remains problematic. Melarsoprol is the only available treatment for late-stage T b rhodesiense infection, but can be lethal to 5% of patients owing to post-treatment reactive encephalopathy. Eflornithine combined with nifurtimox is the first-line treatment for late-stage T b gambiense. New drugs are in the pipeline for treatment of CNS human African trypanosomiasis, giving rise to cautious optimism.

Management of African trypanosomiasis of the CNS: polysomnography as a noninvasive staging tool

Human African trypanosomiasis staging follows human African trypanosomiasis diagnosis (trypanosomes in blood and/or lymph glands, trypanosome-positive). Staging determines treatment, as stage 2 medications are toxic and/or difficult to administer. It relies on cerebrospinal fluid examination: stage 1 (no cerebrospinal fluid trypanosome, trypanosome-negative; white blood cell count ≤5/µl); stage 2 (trypanosome-positive and/or white blood cell count ≥20/µl); intermediate stage (6–19 white blood cell/µl; trypanosome-negative). Lumbar puncture is repeated biannually during the 24-month post-treatment follow-up to confirm cure or detect relapse. Sleep disorders are major at stage 2, with a two-symptom polysomnographic syndrome: sleep–wake circadian disruptions; and sleep-onset rapid eye movement sleep periods. Polysomnography (PSG) was proposed as a noninvasive diagnostic tool, and 24-h PSG recordings were performed throughout a 5-year survey in Congo. Before treatment, 76 patients were included and recorded. Normal sleep–wake patterns occurred in 45 out of 47 stage 1 patients and in 16 out of 19 intermediate-stage patients. PSG syndrome was observed in seven out of ten stage 2 patients. During post-treatment follow-up, PSG syndrome occurrence indicated relapse at stage 2. Thus, noninvasive PSG may represent a valuable alternative for human African trypanosomiasis staging, especially in the post-therapeutic follow-up. The detection of a PSG syndrome would then provoke examination of the patient’s cerebrospinal fluid.

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.