Human African trypanosomiasis: diagnosis, relapse and survival after severe melarsoprol-induced encephalopathy

Clinical management of East African trypanosomiasis in South Africa: Lessons learned

BACKGROUND

East African trypanosomiasis is an uncommon, potentially lethal disease if not diagnosed and treated in a timely manner. South Africa, as a centre for emergency medical evacuations from much of sub-Saharan Africa, receives a high proportion of these patients, mostly tourists and expatriate residents.

METHODS

The cases of East African trypanosomiasis patients evacuated to South Africa, for whom diagnostic and clinical management advice was provided over the years 2004-2018, were reviewed, using the authors' own records and those of collaborating clinicians.

RESULTS

Twenty-one cases were identified. These originated in Zambia, Malawi, Zimbabwe, Tanzania, and Uganda. Nineteen cases (90%) had stage 1 (haemolymphatic) disease; one of these patients had fatal myocarditis. Of the two patients with stage 2 (meningoencephalitic) disease, one died of melarsoprol encephalopathy. Common problems were delayed diagnosis, erroneous assessment of severity, and limited access to treatment.

CONCLUSIONS

The key to early diagnosis is recognition of the triad of geographic exposure, tsetse fly bites, and trypanosomal chancre, plus good microscopy. Elements for successful management are rapid access to specific drug treatment, skilled intensive care, and good laboratory facilities. Clinical experience and the local stock of antitrypanosomal drugs from the World Health Organization have improved the chance of a successful outcome in the management of East African trypanosomiasis in South Africa; the survival rate over the period was 90.5%.

MRI findings of the brain in human African trypanosomiasis: a case series and review of the literature

Human African Trypanosomiasis (HAT) is a neglected tropical disease that affected 3797 people worldwide in 2014. Without treatment mortality approaches 100%. Due to its low incidence and non-specific clinical features, diagnosis can be challenging and the role of MRI in diagnosis of HAT has not been evaluated outside of case reports. We carried out a retrospective, institutional review of three patients presenting with neurological stage (Stage 2) HAT presenting to the Hospital of Tropical Diseases, London between 2004 and 2016. MRI brain was performed in both the acute and follow-up stages of their infection. In addition to confirming that the most common MRI abnormality is T ₂ weighted fluid-attenuated inversion recovery (T2W FLAIR) high signal intensity in the supratentorial white matter, this series has identified radiological findings not previously reported in the literature. In the acute stages, restricted diffusion can be seen in the internal capsules and splenium of the corpus callosum and microhaemorrhages not related to melarsoprol have been identified. Furthermore, the signal abnormality appears to be largely reversible upon treatment with regression associated with mild atrophy demonstrated on follow-up MRI post-treatment. We conclude that although direct microscopy remains the mainstay of diagnosis with serological and polymerase chain reaction (PCR) testing providing useful adjuncts, MRI brain can be helpful in assessing neurological involvement and may provide important prognostic information post-treatment.

Trypanosoma brucei rhodesiense infection in a Chinese traveler returning from the Serengeti National Park in Tanzania

BACKGROUND

Human African trypanosomiasis (HAT) is one of the most complex parasitic diseases known to humankind. It usually occurs in endemic areas in Africa, but is occasionally detected in returning travelers and migrants in non-endemic countries.

CASE PRESENTATION

In August 2017, a case of HAT was diagnosed in China in a traveler returning from the Masai Mara area in Kenya and the Serengeti area in Tanzania. The traveler visited Africa from 23 July to 5 August, 2017. Upon return to China, she developed a fever (on 8 August), and Trypanosoma brucei rhodesiense infection was confirmed by laboratory tests (on 14 August) including observation of parasites in blood films and by polymerase chain reaction. She was treated with pentamidine followed by suramin, and recovered 1 month later.

CONCLUSIONS

This is the first imported rhodesiense HAT case reported in China. This case alerts clinical and public health workers to be aware of HAT in travelers, and expatriates and migrants who have visited at-risk areas in Africa.

Highly sensitive in vivo imaging of Trypanosoma brucei expressing "red-shifted" luciferase

Background

Human African trypanosomiasis is caused by infection with parasites of the Trypanosoma brucei species complex, and threatens over 70 million people in sub-Saharan Africa. Development of new drugs is hampered by the limitations of current rodent models, particularly for stage II infections, which occur once parasites have accessed the CNS. Bioluminescence imaging of pathogens expressing firefly luciferase (emission maximum 562 nm) has been adopted in a number of in vivo models of disease to monitor dissemination, drug-treatment and the role of immune responses. However, lack of sensitivity in detecting deep tissue bioluminescence at wavelengths below 600 nm has restricted the wide-spread use of in vivo imaging to investigate infections with T. brucei and other trypanosomatids.

Methodology/Principal findings

Here, we report a system that allows the detection of fewer than 100 bioluminescent T. brucei parasites in a murine model. As a reporter, we used a codon-optimised red-shifted Photinus pyralis luciferase (PpyRE9H) with a peak emission of 617 nm. Maximal expression was obtained following targeted integration of the gene, flanked by an upstream 5′-variant surface glycoprotein untranslated region (UTR) and a downstream 3′-tubulin UTR, into a T. brucei ribosomal DNA locus. Expression was stable in the absence of selective drug for at least 3 months and was not associated with detectable phenotypic changes. Parasite dissemination and drug efficacy could be monitored in real time, and brain infections were readily detectable. The level of sensitivity in vivo was significantly greater than achievable with a yellow firefly luciferase reporter.

Conclusions/Significance

The optimised bioluminescent reporter line described here will significantly enhance the application of in vivo imaging to study stage II African trypanosomiasis in murine models. The greatly increased sensitivity provides a new framework for investigating host-parasite relationships, particularly in the context of CNS infections. It should be ideally suited to drug evaluation programmes.

Parasites of the Trypanosoma brucei species complex are the causative agents of human African trypanosomiasis. There is an urgent need for new drugs to treat this debilitating and potentially fatal infection, especially in its late stage, when parasites have entered the central nervous system. Factors which hamper drug development include the limitations of the current murine models for stage II disease. In vivo bioluminescence imaging is a non-invasive technique that can be used to monitor infections in real time and is a powerful new approach for studying drug effectiveness. However, application of this imaging technology to trypanosome infections has been restricted because of lack of sensitivity. In this paper, we have taken a major step to resolve this problem. The enhanced sensitivity in infected mice is based on the high level expression in trypanosomes of a “red-shifted” luciferase variant that greatly improves bioluminescence detection in deep tissue. The system which we have developed should be a widely applicable tool for providing new insights into the infection biology of T. brucei.

Parasitoses of the human central nervous system

Cerebral involvement in parasitoses is an important clinical manifestation of most of the human parasitoses. Parasites that have been described to affect the central nervous system (CNS), either as the dominant or as a collateral feature, include cestodes (Taenia solium (neurocysticerciasis), Echinococcus granulosus (cerebral cystic echinococcosis), E. multilocularis (cerebral alveolar echinococcosis), Spirometra mansoni (neurosparganosis)), nematodes (Toxocara canis and T. cati (neurotoxocariasis), Trichinella spiralis (neurotrichinelliasis), Angiostrongylus cantonensis and A. costaricensis (neuroangiostrongyliasis), Gnathostoma spinigerum (gnathostomiasis)), trematodes (Schistosoma mansoni (cerebral bilharziosis), Paragonimus westermani (neuroparagonimiasis)), or protozoa (Toxoplasma gondii (neurotoxoplasmosis), Acanthamoeba spp. or Balamuthia mandrillaris (granulomatous amoebic encephalitis), Naegleria (primary amoebic meningo-encephalitis), Entamoeba histolytica (brain abscess), Plasmodium falciparum (cerebral malaria), Trypanosoma brucei gambiense/rhodesiense (sleeping sickness) or Trypanosoma cruzi (cerebral Chagas disease)). Adults or larvae of helminths or protozoa enter the CNS and cause meningitis, encephalitis, ventriculitis, myelitis, ischaemic stroke, bleeding, venous thrombosis or cerebral abscess, clinically manifesting as headache, epilepsy, weakness, cognitive decline, impaired consciousness, confusion, coma or focal neurological deficits. Diagnosis of cerebral parasitoses is dependent on the causative agent. Available diagnostic tools include clinical presentation, blood tests (eosinophilia, plasmodia in blood smear, antibodies against the parasite), cerebrospinal fluid (CSF) investigations, imaging findings and occasionally cerebral biopsy. Treatment relies on drugs and sometimes surgery. Outcome of cerebral parasitoses is highly variable, depending on the effect of drugs, whether they are self-limiting (e.g. Angiostrongylus costaricensis) or whether they remain undetected or asymptomatic, like 25% of neurocysticerciasis cases.

Human African trypanosomiasis in non-endemic countries (2000-2010)

BACKGROUND

Human African trypanosomiasis (HAT) can affect travelers to sub-Saharan Africa, as well as migrants from disease endemic countries (DECs), posing diagnosis challenges to travel health services in non-disease endemic countries (non-DECs).

METHODS

Cases reported in journals have been collected through a bibliographic research and complemented by cases reported to the World Health Organization (WHO) during the process to obtain anti-trypanosome drugs. These drugs are distributed to DECs solely by WHO. Drugs are also provided to non-DECs when an HAT case is diagnosed. However, in non-DEC pentamidine can also be purchased in the market due to its indication to treat Pneumocystis and Leishmania infections. Any request for drugs from non-DECs should be accompanied by epidemiological and clinical data on the patient.

RESULTS

During the period 2000 to 2010, 94 cases of HAT were reported in 19 non-DECs. Seventy-two percent of them corresponded to the Rhodesiense form, whereas 28% corresponded to the Gambiense. Cases of Rhodesiense HAT were mainly diagnosed in tourists after short visits to DECs, usually within a few days of return. The majority of them were in first stage. Initial misdiagnosis with malaria or tick-borne diseases was frequent. Cases of Gambiense HAT were usually diagnosed several months after initial examination and subsequent to a variety of misdiagnoses. The majority were in second stage. Patients affected were expatriates living in DECs for extended periods and refugees or economic migrants from DECs.

CONCLUSIONS

The risk of HAT in travelers and migrants, albeit low, cannot be overlooked. In non-DECs, rarity, nonspecific symptoms, and lack of knowledge and awareness in health staff make diagnosis difficult. Misdiagnosis is frequent, thus leading to invasive diagnosis methods, unnecessary treatments, and increased risk of fatality. Centralized distribution of drugs for HAT by WHO enables an HAT surveillance system for non-DECs to be maintained. This system provides valuable information on disease transmission and complements data collected in DECs.

Association of Trypanosoma vivax in extracellular sites with central nervous system lesions and changes in cerebrospinal fluid in experimentally infected goats

Changes in cerebrospinal fluid (CSF) and anatomical and histopathological central nervous system (CNS) lesions were evaluated, and the presence of Trypanosoma vivax in CNS tissues was investigated through PCR. Twelve adult male goats were divided into three groups (G): G1, infected with T. vivax and evaluated during the acute phase; G2, infected goats evaluated during the chronic phase; and G3, consisting of non-infected goats. Each goat from G1 and G2 was infected with 1.25 × 10⁵ trypomastigotes. Cerebrospinal fluid (CSF) analysis and investigation of T. vivax was performed at the 15^th day post-infection (dpi) in G1 goats and on the fifth day after the manifestation of nervous system infection signs in G2 goats. All goats were necropsied, and CNS fragments from G1 and G2 goats were evaluated by PCR for the determination of T. vivax. Hyperthermia, anemia and parasitemia were observed from the fifth dpi for G1 and G2, with the highest parasitemia peak between the seventh and 21^st dpi. Nervous system infection signs were observed in three G2 goats between the 30^th and 35^th dpi. CSF analysis revealed the presence of T. vivax for G2. Meningitis and meningoencephalitis were diagnosed in G2. PCR were positive for T. vivax in all the samples tested. In conclusion, T. vivax may reach the nervous tissue resulting in immune response from the host, which is the cause of progressive clinical and pathological manifestations of the CNS in experimentally infected goats.

Trypanosomiasis and the brain

Neurological involvement following trypanosome infection has been recognised for over a century. However, there are still many unanswered questions concerning the mechanisms used by the parasite to gain entry to the CNS and the pathogenesis of the resulting neuroinflammatory reaction. There is a paucity of material from human cases of the disease therefore the majority of current research relies on the use of animal models of trypanosome infection. This review reports contemporary knowledge, from both animal models and human samples, regarding parasite invasion of the CNS and the neuropathological changes that accompany trypanosome infection and disease progression. The effects of trypanosomes on the blood-brain barrier are discussed and possible key molecules in parasite penetration of the barrier highlighted. Changes in the balance of CNS cytokines and chemokines are also described. The article closes by summarising the effects of trypanosome infection on the circadian sleep-wake cycle, and sleep structure, in relation to neuroinflammation and parasite location within the CNS. Although a great deal of progress has been made in recent years, the advent and application of sophisticated analysis techniques, to decipher the complexities of HAT pathogenesis, herald an exciting and rewarding period for advances in trypanosome research.

Genetic characterisation of Trypanosoma brucei s.l. using microsatellite typing: new perspectives for the molecular epidemiology of human African trypanosomiasis

The pathogenic agent of human African trypanosomiasis (HAT) is a trypanosome belonging to the species Trypanosoma brucei s.l. Molecular methods developed for typing T. brucei s.l. stocks are for the most part not polymorphic enough to study genetic diversity within T. brucei gambiense (T. b. gambiense) group 1, the main agent of HAT in West and Central Africa. Furthermore, these methods require high quantities of parasite material and consequently are hampered by a selection bias of the isolation and cultivation techniques. In this study, we evaluated the potential value of microsatellite markers (eight loci) in the genetic characterisation of T. brucei s.l. compared to the multi-locus enzyme electrophoresis reference technique. Stocks isolated in Ivory Coast and reference stocks were used for this purpose. Microsatellite markers were shown to be polymorphic enough to evidence the existence of genetic diversity within T. b. gambiense group 1 and to show the existence of mixed infections. Furthermore, they were able to amplify trypanosome DNA directly from field samples without the usual culturing stages. While the ability of microsatellite markers to detect mixed infections in such field samples is currently being discussed, they appear to be useful to study the parasite population's geographical structure and may provide new insight into their reproductive mode, a topic that is still under debate. Thus, use of microsatellite markers will contribute to the study of the influence of parasite genetics in the diversity of responses to HAT and may contribute to the improvement of HAT molecular diagnosis.