The successful use of radiofrequency-induced heat therapy for cutaneous leishmaniasis: a review

From infection to vaccination: reviewing the global burden, history of vaccine development, and recurring challenges in global leishmaniasis protection

INTRODUCTION

Leishmaniasis is a major public health problem and the second most lethal parasitic disease in the world due to the lack of effective treatments and vaccines. Even when not lethal, leishmaniasis significantly affects individuals and communities through life-long disabilities, psycho-sociological trauma, poverty, and gender disparity in treatment.

AREAS COVERED

This review discusses the most relevant and recent research available on Pubmed and GoogleScholar highlighting leishmaniasis' global impact, pathogenesis, treatment options, and lack of effective control strategies. An effective vaccine is necessary to prevent morbidity and mortality, lower health care costs, and reduce the economic burden of leishmaniasis for endemic low- and middle-income countries. Since there are several forms of leishmaniasis, a pan-Leishmania vaccine without geographical restrictions is needed. This review also focuses on recent advances and common challenges in developing prophylactic strategies against leishmaniasis.

EXPERT OPINION

Despite advances in pre-clinical vaccine research, approval of a human leishmaniasis vaccine still faces major challenges - including manufacturing of candidate vaccines under Good Manufacturing Practices, developing well-designed clinical trials suitable in endemic countries, and defined correlates of protection. In addition, there is a need to explore Challenge Human Infection Model to avoid large trials because of fluctuating incidence and prevalence of leishmanasis.

Cutaneous and Mucocutaneous Leishmaniasis

Leishmaniasis is a chronic disease caused by flagellate protozoa of the genus Leishmania. It is a global disease, but most cases are seen in South America, the Mediterranean, and some areas of Asia and Africa. The 3 main types of leishmaniasis are cutaneous (the most common), mucocutaneous, and visceral (the most severe). Visceral leishmaniasis is also known as kala-azar. Leishmaniasis is diagnosed by demonstrating the presence of Leishmania amastigotes in clinical specimens using direct microscopic examination or molecular analysis. Various treatments exist, although the evidence supporting the options available for cutaneous leishmaniasis is weak. Both the classical presentation of leishmaniasis and our management of the disease have changed in recent decades because of acquired immune deficiency caused by conditions such as human immunodeficiency infection or the use of tumor necrosis factor inhibitors.

Leishmaniasis in the United States: Emerging Issues in a Region of Low Endemicity

Leishmaniasis, a chronic and persistent intracellular protozoal infection caused by many different species within the genus Leishmania, is an unfamiliar disease to most North American providers. Clinical presentations may include asymptomatic and symptomatic visceral leishmaniasis (so-called Kala-azar), as well as cutaneous or mucosal disease. Although cutaneous leishmaniasis (caused by Leishmania mexicana in the United States) is endemic in some southwest states, other causes for concern include reactivation of imported visceral leishmaniasis remotely in time from the initial infection, and the possible long-term complications of chronic inflammation from asymptomatic infection. Climate change, the identification of competent vectors and reservoirs, a highly mobile populace, significant population groups with proven exposure history, HIV, and widespread use of immunosuppressive medications and organ transplant all create the potential for increased frequency of leishmaniasis in the U.S. Together, these factors could contribute to leishmaniasis emerging as a health threat in the U.S., including the possibility of sustained autochthonous spread of newly introduced visceral disease. We summarize recent data examining the epidemiology and major risk factors for acquisition of cutaneous and visceral leishmaniasis, with a special focus on implications for the United States, as well as discuss key emerging issues affecting the management of visceral leishmaniasis.

Cutaneous and Mucocutaneous Leishmaniasis

Leishmaniasis is a chronic disease caused by flagellate protozoa of the genus Leishmania. It is a global disease, but most cases are seen in South America, the Mediterranean, and some areas of Asia and Africa. The 3 main types of leishmaniasis are cutaneous (the most common), mucocutaneous, and visceral (the most severe). Visceral leishmaniasis is also known as kala-azar. Leishmaniasis is diagnosed by demonstrating the presence of Leishmania amastigotes in clinical specimens using direct microscopic examination or molecular analysis. Various treatments exist, although the evidence supporting the options available for cutaneous leishmaniasis is weak. Both the classical presentation of leishmaniasis and our management of the disease have changed in recent decades because of acquired immune deficiency caused by conditions such as HIV infection or the use of TNF inhibitors.

Understanding the immune responses involved in mediating protection or immunopathology during leishmaniasis

Leishmaniasis is a vector-borne Neglected Tropical Disease (NTD) transmitted by the sand fly and is a major public health problem worldwide. Infections caused by Leishmania clinically manifest as a wide range of diseases, such as cutaneous (CL), diffuse cutaneous (DCL), mucosal (MCL) and visceral leishmaniasis (VL). The host innate and adaptative immune responses play critical roles in the defense against leishmaniasis. However, Leishmania parasites also manipulate the host immune response for their survival and replication. In addition, other factors such as sand fly salivary proteins and microbiota also promote disease susceptibility and parasite spread by modulating local immune response. Thus, a complex interplay between parasite, sand fly and the host immunity governs disease severity and outcome. In this review, we discuss the host immune response during Leishmania infection and highlight the factors associated with resistance or susceptibility.

Using Q-methodology to understand the perspectives and practical experiences of dermatologists about treatment difficulties of cutaneous leishmaniasis

Background

During the outbreak of cutaneous leishmaniasis in the Kurdistan Region of Iraq that started in 2015, the course of the disease and the treatment were not consistent with the available literature. Physicians, particularly dermatologists, faced challenges with treating the cutaneous leishmaniasis lesions with high rates of treatment failure and resistance to treatment. We used Q-methodology to understand the range and diversities of opinions and the practical experiences of dermatologists about the treatment difficulties of cutaneous leishmaniasis.

Methods

This Q-methodology study was carried out in Erbil, Kurdistan Region of Iraq, and involved 37 dermatologists. A set of 40 statements related to different aspects of difficulties and uncertainties of treating cutaneous leishmaniasis was prepared. The dermatologists were requested to distribute the 40 statements into a scaled grid of nine piles from least agree to most agree. We applied by-person factor analysis using PQMethod 2.35 for the data analysis.

Results

The analysis revealed two different viewpoints about the treatment of cutaneous leishmaniasis and a consensus viewpoint. The first viewpoint emphasized the use of sodium stibogluconate-based combination therapy, concerns with treatment failure, and lack of compliance with the treatment. The second viewpoint emphasized the lack of standard treatment and advances in the treatment of cutaneous leishmaniasis. There was a consensus between both groups of respondents about many aspects of the treatment of cutaneous leishmaniasis, including considering sodium stibogluconate the first drug of choice for cutaneous leishmaniasis treatment.

Conclusions

This study revealed a diversity of viewpoints and uncertainties about the effectiveness of the available treatment modalities and treatment difficulties and failure. Interrupted supply and poor quality of the available drugs and lack of a standard and advanced treatment are the main problems facing the treatment of cutaneous leishmaniasis. More research is required to determine the best treatment modalities for the different types of cutaneous leishmaniasis. There is a need for the development of treatment guidelines specific to the Iraqi context with a particular focus on the treatment of the resistant and atypical cases of cutaneous leishmaniasis.

Drug Discovery for Kinetoplastid Diseases: Future Directions

Kinetoplastid parasites have caused human disease for millennia. Significant achievements have been made toward developing new treatments for leishmaniasis (particularly on the Indian subcontinent) and for human African trypanosomiasis (HAT). Moreover, the sustained decrease in the incidence of HAT has made the prospect of elimination a tantalizing reality. Despite the gains, no new chemical or biological entities to treat kinetoplastid diseases have been registered in more than three decades, and more work is needed to discover safe and effective therapies for patients with Chagas disease and leishmaniasis. Advances in tools for drug discovery and novel insights into the biology of the host-parasite interaction may provide opportunities for accelerated progress. Here, we summarize the output from a gathering of scientists and physicians who met to discuss the current status and future directions in drug discovery for kinetoplastid diseases.

Leishmaniasis: current challenges and prospects for elimination with special focus on the South Asian region

Leishmania donovani, the most virulent species of Leishmania, is found in the South Asian region that harbours the majority of visceral leishmaniasis (VL) cases in the world. The traditionally accepted relationships between the causative species of Leishmania and the resultant disease phenotype have been challenged during recent years and have underscored the importance of revisiting the previously established taxonomy with revisions to its classification. The weak voice of the afflicted with decades of neglect by scientists and policy makers have led to the miserably inadequate and slow advancements in product development in the fields of diagnostics, chemotherapeutics and vector control that continue to hinder the effective management and control of this infection. Limitations notwithstanding, the regional drive for the elimination of VL initiated over a decade ago that focused on India, Nepal and Bangladesh, the three main afflicted countries in the Indian subcontinent is therefore, commendable, with the subsequent status reviews and restructuring of strategies possibly even more so. However, the renewed efforts would need to be combined with plans to combat new challenges in the South-Asian region that includes the emergence of atypical parasite variants, in order to realistically achieve the set goal of regional elimination of VL.