Case Studies in Infectious Disease: Leishmania Spp 9781136986697, 9780815341420, 0203853911, 0815341423, 1136986693

Table of contents :
Book Cover......Page 1
Title......Page 2
Copyright......Page 3
Preface to Case Studies in Infectious Disease......Page 4
Table of Contents......Page 5
Leishmania spp.......Page 8
Answers to Multiple Choice Questions......Page 19

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Leishmania spp.

Peter M. Lydyard Michael F. Cole John Holton William L. Irving Nino Porakishvili Pradhib Venkatesan Katherine N. Ward

This edition published in the Taylor & Francis e-Library, 2009. To purchase your own copy of this or any of Taylor & Francis or Routledge’s collection of thousands of eBooks please go to www.eBookstore.tandf.co.uk.

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©2010 by Garland Science, Taylor & Francis Group, LLC

This book contains information obtained from authentic and highly regarded sources. Reprinted material is quoted with permission, and sources are indicated. A wide variety of references are listed. Reasonable efforts have been made to publish reliable data and information, but the author and the publisher cannot assume responsibility for the validity of all materials or for the consequences of their use. All rights reserved. No part of this book covered by the copyright heron may be reproduced or used in any format in any form or by any means—graphic, electronic, or mechanical, including photocopying, recording, taping, or information storage and retrieval systems—without permission of the publisher.

The publisher makes no representation, express or implied, that the drug doses in this book are correct. Readers must check up to date product information and clinical procedures with the manufacturers, current codes of conduct, and current safety regulations. ISBN 978-0-8153-4142-0 Library of Congress Cataloging-in-Publication Data Case studies in infectious disease / Peter M Lydyard ... [et al.]. p. ; cm. Includes bibliographical references. SBN 978-0-8153-4142-0 1. Communicable diseases--Case studies. I. Lydyard, Peter M. [DNLM: 1. Communicable Diseases--Case Reports. 2. Bacterial Infections--Case Reports. 3. Mycoses--Case Reports. 4. Parasitic Diseases-Case Reports. 5. Virus Diseases--Case Reports. WC 100 C337 2009] RC112.C37 2009 616.9--dc22 2009004968

Published by Garland Science, Taylor & Francis Group, LLC, an informa business 270 Madison Avenue, New York NY 10016, USA, and 2 Park Square, Milton Park, Abingdon, OX14 4RN, UK. Visit our web site at http://www.garlandscience.com ISBN 0-203-85391-1 Master e-book ISBN

Peter M. Lydyard, Emeritus Professor of Immunology, University College Medical School, London, UK and Honorary Professor of Immunology, School of Biosciences, University of Westminster, London, UK. Michael F. Cole, Professor of Microbiology & Immunology, Georgetown University School of Medicine, Washington, DC, USA. John Holton, Reader and Honorary Consultant in Clinical Microbiology, Windeyer Institute of Medical Sciences, University College London and University College London Hospital Foundation Trust, London, UK. William L. Irving, Professor and Honorary Consultant in Virology, University of Nottingham and Nottingham University Hospitals NHS Trust, Nottingham, UK. Nino Porakishvili, Senior Lecturer, School of Biosciences, University of Westminster, London, UK and Honorary Professor, Javakhishvili Tbilisi State University, Tbilisi, Georgia. Pradhib Venkatesan, Consultant in Infectious Diseases, Nottingham University Hospitals NHS Trust, Nottingham, UK. Katherine N. Ward, Consultant Virologist and Honorary Senior Lecturer, University College Medical School, London, UK and Honorary Consultant, Health Protection Agency, UK.

Preface to Case Studies in Infectious Disease The idea for this book came from a successful course in a medical school setting. Each of the forty cases has been selected by the authors as being those that cause the most morbidity and mortality worldwide. The cases themselves follow the natural history of infection from point of entry of the pathogen through pathogenesis, clinical presentation, diagnosis, and treatment. We believe that this approach provides the reader with a logical basis for understanding these diverse medically-important organisms. Following the description of a case history, the same five sets of core questions are asked to encourage the student to think about infections in a common sequence. The initial set concerns the nature of the infectious agent, how it gains access to the body, what cells are infected, and how the organism spreads; the second set asks about host defense mechanisms against the agent and how disease is caused; the third set enquires about the clinical manifestations of the infection and the complications that can occur; the fourth set is related to how the infection is diagnosed, and what is the differential diagnosis, and the final set asks how the infection is managed, and what preventative measures can be taken to avoid the infection. In order to facilitate the learning process, each case includes summary bullet points, a reference list, a further reading list and some relevant reliable websites. Some of the websites contain images that are referred to in the text. Each chapter concludes with multiple-choice questions for self-testing with the answers given in the back of the book. In the contents section, diseases are listed alphabetically under the causative agent. A separate table categorizes the pathogens as bacterial, viral, protozoal/worm/fungal and acts as a guide to the relative involvement of each body system affected. Finally, there is a comprehensive glossary to allow rapid access to microbiology and medical terms highlighted in bold in the text. All figures are available in JPEG and PowerPoint® format at www.garlandscience.com/gs_textbooks.asp We believe that this book would be an excellent textbook for any course in microbiology and in particular for medical students who need instant access to key information about specific infections. Happy learning!!

The authors March, 2009

Table of Contents The glossary for Case Studies in Infectious Disease can be found at http://www.garlandscience.com/textbooks/0815341423.asp Case 1 Case 2 Case 3 Case 4 Case 5 Case 6 Case 7 Case 8 Case 9 Case 10 Case 11 Case 12 Case 13 Case 14 Case 15 Case 16 Case 17 Case 18 Case 19 Case 20 Case 21 Case 22 Case 23 Case 24 Case 25 Case 26 Case 27 Case 28 Case 29 Case 30 Case 31 Case 32 Case 33 Case 34 Case 35 Case 36 Case 37 Case 38 Case 39 Case 40

Aspergillus fumigatus Borellia burgdorferi and related species Campylobacter jejuni Chlamydia trachomatis Clostridium difficile Coxiella burnetti Coxsackie B virus Echinococcus spp. Epstein-Barr virus Escherichia coli Giardia lamblia Helicobacter pylori Hepatitis B virus Herpes simplex virus 1 Herpes simplex virus 2 Histoplasma capsulatum Human immunodeficiency virus Influenza virus Leishmania spp. Leptospira spp. Listeria monocytogenes Mycobacterium leprae Mycobacterium tuberculosis Neisseria gonorrhoeae Neisseria meningitidis Norovirus Parvovirus Plasmodium spp. Respiratory syncytial virus Rickettsia spp. Salmonella typhi Schistosoma spp. Staphylococcus aureus Streptococcus mitis Streptococcus pneumoniae Streptococcus pyogenes Toxoplasma gondii Trypanosoma spp. Varicella-zoster virus Wuchereia bancrofti

Guide to the relative involvement of each body system affected by the infectious organisms described in this book: the organisms are categorized into bacteria, viruses, and protozoa/fungi/worms

Organism

Resp

MS

GI

H/B

GU

CNS

CV

Skin

Syst

1+

1+

L/H

Bacteria Borrelia burgdorferi

4+

Campylobacter jejuni

4+

Chlamydia trachomatis

2+ 2+

Clostridium difficile

4+

4+

Coxiella burnetti

4+

Escherichia coli

4+

4+

Helicobacter pylori

4+

4+

4+

4+

4+

Listeria monocytogenes

2+

4+

Mycobacterium leprae

4+ 4+

4+

2+ 4+

Neisseria meningitidis

2+ 4+

Rickettsia spp.

4+ 4+

Salmonella typhi

4+

4+ 1+

1+

2+

1+ 1+

4+

Streptococcus pyogenes

4+ 4+

Streptococcus mitis Streptococcus pneumoniae

2+

2+

Neisseria gonorrhoeae

Staphylococcus aureus

4+

4+

Leptospira spp.

Mycobacterium tuberculosis

2+

4+

1+

4+

3+

4+

4+ 3+

Viruses Coxsackie B virus

1+

1+

4+

1+

Epstein-Barr virus Hepatitis B virus

4+

2+

4+

4+

Herpes simplex virus 1

2+

4+

4+

Herpes simplex virus 2

4+

2+

4+

2+

Human immunodeficiency virus

Influenza virus

2+

4+

1+

Norovirus

1+

4+

Parvovirus

2+

Respiratory syncytial virus

4+

Varicella-zoster virus

2+

3+

4+ 2+

4+

2+

Protozoa/Fungi/Worms Aspergillus fumigatus

4+

Echinococcus spp.

2+

Giardia lamblia Histoplasma capsulatum

1+ 4+ 4+

3+

1+

Leishmania spp.

4+

4+ 4+

4+

4+ 4+

Toxoplasma gondii Trypanosoma spp.

4+ 4+

Plasmodium spp. Schistosoma spp.

2+

2+ 4+

Wuchereria bancrofti

4+

4+ 4+ 4+

The rating system (+4 the strongest, +1 the weakest) indicates the greater to lesser involvement of the body system. KEY: Resp = Respiratory: MS = Musculoskeletal: GI = Gastrointestinal H/B = Hepatobiliary: GU = Genitourinary: CNS = Central Nervous System Skin = Dermatological: Syst = Systemic: L/H = Lymphatic-Hematological

Leishmania spp.

A 72-year-old gentleman retired to the south of Spain but returned to the UK for the summer months. He began to develop fever, malaise, loss of appetite, and weight loss. He was admitted to hospital and had temperatures reaching 39∞C. Both his liver and spleen were palpable. No lymph nodes could be felt. Blood tests showed a pancytopenia. Routine investigations for an infection were negative and he did not improve with broadspectrum antibiotics. His condition deteriorated and the size of the liver and spleen increased (Figure 1). A bone marrow examination did not show any sign of hematological malignancy. No organisms were seen on staining. His history was explored again. Four months before his illness he had been on a camping break in Spain to a coastal area. He recalled seeing many thin dogs in the vicinity. Part of his bone marrow sample was sent to a reference laboratory for Leishmania polymerase chain reaction (PCR). This returned positive. He was successfully treated with a course of liposomal amphotericin B and over the ensuing 3 months his liver and spleen became impalpable and his blood tests returned to normal. His diagnosis was visceral leishmaniasis probably due to Leishmania infantum. Figure 1. A child with visceral leishmaniasis. As in the patient described in the case history the liver and spleen are enlarged, causing distension of the abdomen.

1. What is the causative agent, how does it enter the body and how does it spread a) within the body and b) from person to person? Causative agent Leishmania are protozoan parasites. They have an intracellular form called an amastigote (Figure 2) and an extracellular, flagellated form called a promastigote (Figure 3). There is variety in the clinical diseases caused, geographical distribution, and animal reservoirs. The genus Leishmania is divided into groups, species, and complexes. Classification was classically determined by isoenzyme typing; molecular methods (using DNA) are now more common. Table 1 lists species and the diseases they cause.

Figure 2. A skin biopsy showing Leishmania amastigotes (arrowed).

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LEISHMANIA

Table 1. Species of Leishmania and the diseases they cause Disease

Species

Cutaneous leishmaniasis

L. aethiopica L. killicki L. major L. tropica L. amazonensis L. columbiensis L. guyanensis L. lainsoni L. mexicana L. naiffi L. shawi L. venezuelensis

Mucocutaneous leishmaniasis

L. braziliensis L. panamensis

Visceral leishmaniasis

L. donovani L. infantum L. chagasi

Figure 3. Elongated Leishmania promastigotes.

Entry and spread within the body People are infected after the bite of a sandfly laden with Leishmania promastigotes. Under the skin the promastigotes are rapidly phagocytosed by macrophages. For cutaneous disease lesions are confined to the locality of the sandfly bite. For L. braziliensis and L. panamensis cutaneous spread can occur and later this can involve mucous membranes of the mouth or nose. L. donovani and L. infantum are capable of deeper spread within macrophages to the rest of the mononuclear phagocytic system, mainly present in organs such as the liver, spleen, and bone marrow. They are responsible for visceral leishmaniasis. In India, visceral leishmaniasis is called kala-azar. Relapse of infection after an interval may be manifest as a widespread cutaneous form of disease, called post kala-azar dermal leishmaniasis (PKDL). This occurs in India and East Africa. The life cycle of Leishmania is shown in Figure 4. Person to person spread In areas with visceral leishmaniasis sandflies can ingest protozoa when they feed from the skin. Numbers of Leishmania in the skin are even higher in PKDL. However, leishmaniasis is largely a zoonosis. Different animal reservoirs occur in different regions. They include rodents, gerbils, hyraxes, sloths, and the domestic dog. The sandfly vector is a Phlebotomus species in the Old World and Lutzomyia species in the New World. Sandflies are small, less than 5 mm in size, and bite at dusk or during the night (Figure 5). They are not capable of flying great heights above the ground and usually bite individuals sleeping close to the ground. In the case described above the patient was probably infected through sandflies when he was lying near the ground on his camp bed. He normally lived in a flat. The sandflies will have carried infection from the local dog population.

LEISHMANIA

sandfly stages

1 sandfly takes a blood meal

3

human stages

(injects promastigote stage into the skin) i

8 promastigotes divide in midgut and migrate to proboscis

2 promastigotes are phagocytosed by macrophages

d

3 promastigotes transform into amastigotes inside macrophages

7 amastigotes transform into promastigotes inside midgut

d

4 amastigotes multiply in cells (including macrophages) of various tissues

6 ingestion of parasitized cell i

infective stage

d diagnostic stage

5 sandfly takes a blood meal (ingests macrophages infected with amastigotes)

Figure 4. Life cycle of Leishmania spp. Leishmania promastigotes are inoculated by sandflies into human and other animal hosts at the time of taking a blood meal (1). Promastigotes are phagocytosed by macrophages (2). Within macrophages

promastigotes transform into amastigotes (3). Amastigotes can multiply in various cell types (4). Macrophages containing amastigotes are ingested by sandflies taking a blood meal (5) and the life cycle continues within the sandfly vector (6–8).

Female sandflies bite and take blood from their target host. Any amastigotes ingested from the skin change into promastigotes. These pass into the sandfly midgut, proliferate, cause damage to the digestive valve system, and are regurgitated to the biting mouthparts and then onto the skin of the next host to be bitten. Another form of transmission for visceral leishmaniasis has been described among intravenous drug users in Southern Europe. Infection can be passed on with shared needles and equipment. In one study about half of discarded needles in Madrid were positive by PCR for Leishmania.

Epidemiology Notification of cases of leishmaniasis occurs in only 32 of 88 endemic countries. Numbers of people afflicted by the disease are therefore estimates. There are about 0.5 million new cases of visceral leishmaniasis annually, and 90% of these are seen in Bangladesh, Brazil, India, Nepal, and Sudan. Another 1.5 million individuals get cutaneous or mucocutaneous disease.

Figure 5. Phlebotomus sandfly.

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LEISHMANIA

About 90% of mucocutaneous disease occurs in Bolivia, Brazil, and Peru, while about 90% of cutaneous disease occurs in Afghanistan, Brazil, Iran, Peru, Saudia Arabia, and Syria. In total there is an estimated worldwide prevalence of 12 million cases.

2. What is the host response to the infection and what is the disease pathogenesis? As promastigotes enter the skin they are phagocytosed by macrophages and neutrophils. They change into amastigotes. Classically any pathogen engulfed by a phagocyte is wrapped within host cell plasma membrane. This forms a phagosome. Various membrane molecules are imported and exported as cytoplasmic vesicles fuse with or erupt from the phagosome. Eventually lysosomes fuse with the phagosome and discharge their contents. Lysosomal enzymes lyse susceptible pathogens. On engulfment phagocytes are activated to produce reactive oxygen species and reactive a), nitrogen intermediates. They secrete tumor necrosis factor-a (TNF-a which contributes to their activation state. Macrophages are activated further by T-helper 1 lymphocytes (Th1) through interferon-g (IFN-gg). These are stimulated by antigen-presenting cells, most efficiently by dendritic cells. They secrete interleukin-12 (IL-12). When it takes time to deal with a pathogen the combination of Th1 cells and macrophages organize into granulomas. To survive, Leishmania need to subvert the above process. Various effects have been described but the mechanisms by which these occur are not altogether clear. Some leishmanial molecules that have been shown experimentally to play a part are lipophosphoglycan, a surface membrane metalloprotease (gp63), cysteine proteases, and a Leishmania homolog of activated C kinase receptor (LACK). The outcome is macrophage activation and the generation of reactive oxygen and nitrogen intermediates is suppressed, Leishmania resist lysosomal attack, dendritic function is compromised, and LACK induces a Th2 response. Recent in vitro work on human cells suggests that Leishmania may use neutrophils as a ‘Trojan horse.’ Neutrophils fail to kill Leishmania after phagocytosis and undergo apoptosis. Apoptotic fragments may contain b, a chemokine that attracts Leishmania. The neutrophils release MIP-1b macrophages. When macrophages phagocytose the apoptotic neutrophil fragments, Leishmania enter ‘silently’ and continue to multiply. The b (TGF-b b), which is macrophages release transforming growth factor-b anti-inflammatory. In mice experimentally infected with L. major there is a clear polarization of Th1 and Th2 responses. Some strains mount a Th1 response and control infection, unlike others (BALB/c), which mount a Th2 response and experience fatal disseminated infection. Humans infected with L. major experience localized cutaneous disease. Conversely L. donovani, which causes visceral leishmaniasis in humans, can be controlled by BALB/c mice. L. donovani does not lead to a polarized Th1 and Th2 response between mouse strains. While there are differences between mice and humans in Leishmania infection, the experimental experience with mice indicates the important role of host genetics.

LEISHMANIA

5

In humans, markers of a Th1 (IFN-g) and Th2 (interleukin (IL)-4) response are both present at the same time. IL-4 down-regulates Th1 responses and so do other cytokines such as IL-10, IL-13, and TGF-b. These cytokines are more prominent in forms of infection that are not self-limiting like visceral leishmaniasis and PKDL. IL-10 seems to play a greater role in susceptibility to these infections than IL-4. Otherwise an unrestrained Th1 response heals other forms of infection.

3. What is the typical clinical presentation and what complications can occur? Infection may be asymptomatic. Leishmania may reside in the body for years and only cause clinical disease if the host becomes immunocompromised. Cutaneous leishmaniasis is seen on exposed parts of the body where the sandflies are likely to bite (Figure 6). Thus lesions may be found on the face, arms, and lower legs. Lesions may be single or multiple. They are usually apparent 2–6 weeks after the bite. Initially there is a red papule. This gradually enlarges over a few weeks. The lesion may take on a raised ulcerated form or be papulo-nodular. Secondary infection is possible and then lesions are more likely to be painful. Without specific treatment lesions will usually self-heal, but over prolonged periods. This may take 6 months to a few years. Over this period lesions may seem to regress and then relapse. All Leishmania species are capable of causing cutaneous disease, but the host immune response may alter the clinical picture. A weakened immune response with a high parasite burden causes diffuse cutaneous leishmaniasis with multiple, spreading papular lesions. There may also be lymphatic spread with localized nodules along the track of lymphatics. A strong immune response with a low parasite burden causes a condition called leishmania recidivans. The immune response effectively clears the initial site of infection. A series of small papules surround this central clearing and these in turn are cleared.

Figure 6. Cutaneous leishmaniasis of an ulcerating form.

Mucocutaneous leishmaniasis is associated with L. braziliensis and L. panamensis. As these species names suggest this form of leishmaniasis is restricted to South America. Cutaneous lesions occur first as in purely cutaneous leishmaniasis. These can self-heal, but the parasite does not disappear from the body. After an interval, sometimes of several years, the parasite re-emerges in the mucous membranes of nose or mouth. Local inflammation results in nasal stuffiness. There is then progressive destruction of the anatomy of the nose or mouth and infection can progress backwards towards the throat and larynx (Figure 7). Eating and drinking become difficult and secondary infections in the upper and lower respiratory tract often occur. These latter effects can prove fatal unless the infection is treated. There can be considerable scarring and disfigurement if treatment is delayed. Visceral leishmaniasis is associated with L. donovani in India and East Africa and with L. infantum around the Mediterranean and South America. A cutaneous lesion may not be apparent. After an incubation period of a few months illness is heralded by fevers. These may continue for about a month before abating. The spleen progressively enlarges first and then the liver (Figure 1). Both may become massively enlarged. The enlarged

Figure 7. Mucocutaneous leishmaniasis in a patient with progressive destruction of tissues around the lips and nose.

6

LEISHMANIA

spleen causes hypersplenism and consumption of blood cells, but infection within the bone marrow also causes a pancytopenia with anemia, leukopenia, and thrombocytopenia. In dark skins the anemia plus hormonal effects of chronic infection cause an altered appearance. In India the graying of the complexion is called kala-azar. Leukopenia predisposes to secondary infections, which themselves may be life-threatening. Thrombocytopenia can predispose to bleeding and there may be lifethreatening hemorrhage. On blood tests there is also a fall in albumin levels. A drop in oncotic pressure can result in edema. This may be peripheral in the legs or ascites within the abdomen. There is also a polyclonal stimulation of IgG antibodies. The polyclonal stimulation of B lymphocytes can compromise their ability to respond to other infections. Visceral leishmaniasis runs a chronic and progressive course. Patients become wasted. It is invariably fatal unless treated. If treated some parasites may escape killing and return later to cause post kala-azar dermal leishmaniasis (PKDL). In India this interval may be 2–3 years, but shorter intervals have been observed in Sudan. The host now has some immunity from the first spell of visceral leishmaniasis. The parasite is largely confined to the skin, with extensive papulo-nodular lesions starting on the face and peripheries and then spreading to most of the body surface. This may self-cure, only to relapse and remit at a later date. Leishmaniasis and HIV co-exist in many areas. The immunocompromised nature of HIV has caused more florid manifestations of leishmaniasis. Parasite burdens are higher. Species that may only cause cutaneous disease may become visceral.

4. How is the disease diagnosed and what is the differential diagnosis? In endemic areas cutaneous and mucocutaneous leishmaniasis may be diagnosed on purely clinical grounds. The clinical picture of fever, splenomegaly, and anemia due to visceral leishmaniasis may also be caused by other diseases. Investigations are required to confirm the diagnosis. These could entail direct visualization of the parasite in a tissue sample, detection of antigen, detection of nucleic acid by PCR, or immunodiagnosis. The latter includes serology or a leishmanial skin test. Deep tissue samples may be obtained by a splenic aspirate, bone marrow aspirate, lymph node aspirate, or sometimes liver biopsy. Cutaneous lesions may be squeezed firmly with fingers to exclude blood, superficially incised with a scalpel at their edge, and then tissue fluid expressed and impressed onto a glass slide. On staining of tissue samples intracellular amastigotes are sought. Their appearance is characteristic with a small kinetoplast body adjacent to the nucleus. This is called a Donovan body (Figure 8). The sensitivity of tissue sampling varies with the sample – >90% for splenic aspirate, 55–97% for bone marrow, and 60% for lymph nodes. If facilities are available culture can help, but now in resource-rich settings PCR is applied with a sensitivity of >95%. Leishmanial antigen can be detected in urine. A latex agglutination technique called KATEX has shown sensitivities of 68–100% for visceral leishmaniasis. After successful treatment antigen disappears from the urine.

LEISHMANIA

Figure 8. Characteristic Leishmania amastigote forms (Donovan bodies, arrowed) on an impression smear. Darkly staining small kinetoplast adjacent to nuclei.

Donovan body

Serological immunological tests are unable to distinguish current from past infection. A commonly used test for anti-leishmanial antibody is the direct agglutination test (DAT). Promastigotes are formalin-fixed onto slides and serum is placed on top. Agglutination is observed after 24 hours. DAT has a sensitivity of about 95% and its specificity is about 86%. A dipstick test has been developed with the K39 antigen impregnated on a reagent strip. Blood is added to the strip and a reaction noted after 20 minutes. The K39 dipstick has a sensitivity of about 94% and specificity of about 90%. Historically a test similar to the tuberculin skin test for tuberculosis was used for leishmaniasis. This was the Montenegro skin test. Leishmanial antigen was implanted in the forearm and the induration after 48–72 hours was measured. Now standardized antigen preparations are no longer available. When available the skin test had been useful in distinguishing present from past infection.

Differential diagnosis In endemic areas, cutaneous and mucocutaneous leishmaniasis may have a characteristic appearance. Cutaneous lesions may have to be differentiated from other infected insect bites, tuberculosis, fungal infection, myiasis, and skin cancers. Mucosal sites may also be affected by syphilis, histoplasmosis, paracoccidioidomycosis, and leprosy. Visceral leishmaniasis may have to be differentiated from other causes of fever, splenomegaly, and anemia. The differential diagnosis includes malaria, schistosomiasis, typhoid fever, brucellosis, tuberculosis, rickettsial infection, sarcoidosis, Still’s disease, and hematological malignancy.

5. How is the disease managed and prevented? Management Simple cutaneous leishmaniasis may be left to self-heal in geographical areas with L. major. Some cutaneous lesions, mucocutaneous disease, and visceral leishmaniasis require treatment. Until recently the mainstay of treatment has been pentavalent antimony compounds. These include sodium stibogluconate and meglumine antimonate. They are administered

7

8

LEISHMANIA

by intramuscular injection on a daily basis for up to 28 days. The intramuscular injections can be painful and there can be systemic toxicity. Amphotericin B and more recently liposomal amphotericin B represent advances in treatment. However, they require intravenous administration, are also toxic, and are much more expensive, especially liposomal amphotericin B. An oral, tolerable agent is now available for visceral leishmaniasis. Oral miltefosine for 28 days was shown to be equally effective with amphotericin B for visceral leishmaniasis in India. Alternative treatments are very welcome, as about 60% of visceral leishmaniasis infections in Bihar, India are resistant to treatment with pentavalent antimonials.

Prevention Vaccines have been trialed for leishmaniasis, but have not been encouraging to date. Prevention has therefore focused on sandflies. As they bite at night, sleeping under a bed-net might afford some protection. But the sandflies are small and can get through the mesh of the nets. However, if the nets are impregnated with a pyrethroid insecticide the sandflies are killed. Insecticide-treated bed-nets are also a key component of malaria control programmes. Their distribution and maintenance are a logistic challenge. To date there seems to have been little impact on the incidence of leishmaniasis. Numbers of cases seem to be growing worldwide.

LEISHMANIA

SUMMARY 1. What is the causative agent, how does it enter the body and how does it spread a) within the body and b) from person to person? ●

Leishmania are protozoan parasites.

●

There is a large number of species.

●

The extracellular stage is called the promastigote and the intracellular stage is the amastigote.

●

Spread is by sandflies either from animal reservoirs or humans with heavy skin loads of parasite. The latter occurs in a condition called post kala-azar dermal leishmaniasis.

●

●

●

Visceral leishmaniasis is due to L. donovani or L. infantum.

●

Infection spreads through the mononuclear phagocytic system with enlargement of spleen and liver, and bone marrow infiltration.

●

Skin complexion changes giving rise to the Indian term, kala-azar.

●

After treatment of visceral leishmaniasis relapse may be confined to the skin with post kala-azar dermal leishmaniasis.

4. How is the disease diagnosed and what is the differential diagnosis? ●

Leishmania are phagocytosed by neutrophils and macrophages.

Diagnosis of cutaneous or mucocutaneous leishmaniasis may be purely clinical.

●

T-helper 1 lymphocytes help macrophages to kill Leishmania.

Stained tissue samples may show characteristic Donovan bodies.

●

Species-specific PCR has a high sensitivity.

●

Assays exist for leishmanial antigen or antibody.

●

Some species may be more successful at subverting the immune response and causing disseminated infection.

●

Subversion of the immune response involves suppression of macrophage activation and diversion towards a T-helper 2 type of response.

●

After an initial cutaneous lesion there is a later mucosal lesion, which is progressively destructive of nose or mouth.

The ability to spread within the body is a function of both the species of Leishmania and the host immune response.

2. What is the host response to the infection and what is the disease pathogenesis? ●

●

In mice infected with L. major there is a clear polarization of T-helper 1 and 2 responses, depending on the genetic background of the mice.

3. What is the typical clinical presentation and what complications can occur? ●

Cutaneous leishmaniasis is caused by a large number of species with infection confined to one locality.

●

Lesions enlarge gradually over a few weeks, become papulo-nodular or ulcerate.

●

Lesions may self-heal.

●

Mucocutaneous leishmaniasis is caused by L. braziliensis and L. panamensis.

5. How is the disease managed and prevented? ●

Simple cutaneous lesions may self-heal.

●

Parenteral pentavalent antimonial drugs have been traditional treatment for all forms of disease.

●

Parenteral amphotericin B, either conventional or liposomal, can be used for visceral leishmaniasis.

●

Oral miltefosine is a recent advance in treating visceral leishmaniasis.

9

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LEISHMANIA

FURTHER READING Dedet JP, Pratlong F. Leishmaniasis. In: Cook GC, Zumla AI. Manson’s Tropical Diseases, 21st edition. Saunders/Elsevier, London/Philadelphia, 2003: 1339–1364.

Murphy K, Travers P, Walport M. Janeway’s Immunobiology, 7th edition. Garland Science, New York, 2008.

REFERENCES Chappuis F, Rijal S, Soto A, et al. A meta-analysis of the diagnostic performance of the direct agglutination test and rK39 dipstick for visceral leishmaniasis. BMJ, 2006, 333: 723–726. Herwaldt BL. Leishmaniasis. Lancet, 1999, 354: 1191–1199. Murray HW, Berman JD, Davies CR, Saravia NG. Advances in leishmaniasis. Lancet, 2005, 366: 1561–1577.

Sundar S, Jha TK, Thakur CP, et al. Oral miltefosine for Indian visceral leishmaniasis. N Engl J Med, 2002, 347: 1739–1746. Van Zandbergen G, Klinger M, Mueller A, et al. Neutrophil granulocyte serves as a vector for Leishmania entry into macrophages. J Immunol, 2004, 173: 6521–6525.

Sundar S, Rai M. Laboratory diagnosis of visceral leishmaniasis. Clin Diagn Lab Immunol, 2002, 9: 951–958.

WEB SITES Centers for Disease Control and Prevention, Atlanta, Georgia, USA: www.cdc.gov/

World Health Organization: www.who.int

Centre for Infections, Health Protection Agency, HPA Copyright, 2008: www.hpa.org.uk

MULTIPLE CHOICE QUESTIONS The questions should be answered either by selecting True (T) or False (F) for each answer statement, or by selecting the answer statements which best answer the question. Answers can be found in the back of the book. 1. Which of the following are true about the causative agent of leishmaniasis? A. The extracellular form of leishmania is called the amastigote. B. Leishmania can be taxonomically subdivided by isoenzyme typing. C. The form of clinical disease can depend on the species of Leishmania. D. There are both animal and human reservoirs of infection. E. Spread within the body occurs inside macrophages.

2. Which of the following are true of the transmission of leishmaniasis? A. The domestic dog can serve as a reservoir of infection. B. The insect vector is the mosquito. C. The infective form when the vector bites a new host is the amastigote. D. Infection can be transmitted between intravenous drug users with shared needles and equipment. E. Individuals with post kala-azar dermal leishmaniasis (PKDL) can serve as a human reservoir of infection. 3. Which of the following are true of the host response to leishmaniasis? A. A Th1 response is associated with susceptibility. B. Transforming growth factor-b activates macrophages to increase leishmanicidal functions.

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MULTIPLE CHOICE QUESTIONS (continued) C. In different strains of mice infected with L. major there is either a Th1 or Th2 response.

B. On staining tissue samples the characteristic appearance of the organism is called Donovan bodies.

D. Neutrophils fail to kill phagocytosed Leishmania.

C. The sensitivity of splenic aspirates is about 50%.

E. A granulomatous inflammatory response develops in tissues.

D. PCR has a high sensitivity and specificity.

4. Which of the following are true of the pathogenesis of leishmaniasis? A. Leishmania may enter macrophages in apoptotic neutrophil fragments.

E. Serological tests can distinguish recent acute infection from past infection. 8. Which of the following are true of the differential diagnosis of leishmaniasis?

B. Leishmania are susceptible to lysosomal attack.

A. Cutaneous tuberculosis may cause similar cutaneous lesions.

C. Leishmania homolog of activated C kinase receptor (LACK) steers the host to a Th1 response.

B. Mucocutaneous leishmaniasis is the only infection that destroys the nasal septum.

D. Dendritic cell antigen presentation is down-regulated by Leishmania.

C. Visceral leishmaniasis may have to be differentiated from malaria.

E. Leishmania suppresses the production of reactive oxygen and nitrogen intermediates.

D. Clinical features alone are sufficient to differentiate visceral leishmaniasis from other diagnoses.

5. Which of the following are true of cutaneous and mucocutaneous leishmaniasis? A. Cutaneous lesions are usually found in moist areas such as the armpit and groins.

E. Noninfectious diseases can cause fever like visceral leishmaniasis. 9. Which of the following are true of the treatment of leishmaniasis?

C. Lesions are always painful.

A. All cutaneous lesions need to be treated to prevent disease progression.

D. L. braziliensis and L. panamensis are the key species responsible for mucocutaneous disease.

B. All treatments are parenteral (i.e. need to be given by injection).

E. In mucocutaneous disease the mucosal lesions appear several years after an initial cutaneous lesion.

C. Treatment courses can last up to 28 days.

B. Lesions are manifest 2–6 days after a bite.

6. Which of the following are true of visceral leishmaniasis? A. Massive enlargement of the liver and spleen are possible. B. As a reaction to infection there is a rise in the number of platelets. C. In the blood there is a hypergammaglobulinemia. D. Post kala-azar dermal leishmaniasis occurs as an immediate reaction to treatment for visceral leishmaniasis. E. In HIV-infected patients usually cutaneous species of Leishmania can cause visceral disease. 7. Which of the following are true of the diagnosis of leishmaniasis? A. Mucocutaneous disease can be diagnosed clinically in endemic areas.

D. Liposomal amphotericin B can be used to treat visceral leishmaniasis. E. Miltefosine is less effective than other treatments for visceral leishmaniasis. 10. Which of the following are true of the control and prevention of leishmaniasis? A. Mosquito nets are sufficient to prevent sandfly bites. B. The distribution of mosquito nets to control malaria has reduced the incidence of leishmaniasis. C. Sandflies are intrinsically resistant to pyrethroid insecticides. D. There is no effective vaccine to date. E. Treatment of individuals with post kala-azar dermal leishmaniasis is sufficient to eliminate the reservoir of infection.

Answers to Multiple Choice Questions 1. Which of the following are true about the causative agent of leishmaniasis? A. The extracellular form of Leishmania is called the amastigote. FALSE: this is the intracellular form. The flagellated promastigote is extracellular. B. Leishmania can be taxonomically subdivided by isoenzyme typing. TRUE. C. The form of clinical disease can depend on the species of Leishmania. TRUE. D. There are both animal and human reservoirs of infection. TRUE. E. Spread within the body occurs inside macrophages. TRUE. 2. Which of the following are true of the transmission of leishmaniasis? A. The domestic dog can serve as a reservoir of infection. TRUE. B. The insect vector is the mosquito. FALSE: the vector is the sandfly. C. The infective form when the vector bites a new host is the amastigote. FALSE: it is the promastigote. D. Infection can be transmitted between intravenous drug users with shared needles and equipment. TRUE. E. Individuals with post kala-azar dermal leishmaniasis (PKDL) can serve as a human reservoir of infection. TRUE. 3. Which of the following are true of the host response to leishmaniasis? A. A Th1 response is associated with susceptibility. FALSE: Th1 is protective. B. Transforming growth factor-b activates macrophages to increase leishmanicidal functions. FALSE: interferon-g activates macrophages. C. In different strains of mice infected with L. major there is either a Th1 or Th2 response. TRUE. D. Neutrophils fail to kill phagocytosed Leishmania. TRUE. E. A granulomatous inflammatory response develops in tissues. TRUE. 4. Which of the following are true of the pathogenesis of leishmaniasis? A. Leishmania may enter macrophages in apoptotic neutrophil fragments. TRUE. B. Leishmania are susceptible to lysosomal attack.

FALSE: they resist lysosomal attack. C. Leishmania homolog of activated C kinase receptor (LACK) steers the host to a Th1 response. FALSE: it steers to a Th2 response. D. Dendritic cell antigen presentation is down-regulated by Leishmania. TRUE. E. Leishmania suppresses the production of reactive oxygen and nitrogen intermediates. TRUE. 5. Which of the following are true of cutaneous and mucocutaneous leishmaniasis? A. Cutaneous lesions are usually found in moist areas such as the armpit and groins. FALSE: they are usually found in exposed areas of the body where the sandfly bites. B. Lesions are manifest 2–6 days after a bite. FALSE: usually 2–6 weeks. C. Lesions are always painful. FALSE: lesions may be painless, but are more likely to become painful when secondarily infected. D. L. braziliensis and L. panamensis are the key species responsible for mucocutaneous disease. TRUE. E. In mucocutaneous disease the mucosal lesions appear several years after an initial cutaneous lesion. TRUE. 6. Which of the following are true of visceral leishmaniasis? A. Massive enlargement of the liver and spleen are possible. TRUE. B. As a reaction to infection there is a rise in the number of platelets. FALSE: usually platelet numbers fall due to a combination of bone marrow suppression and hypersplenism. C. In the blood there is a hypergammaglobulinemia. TRUE. D. Post kala-azar dermal leishmaniasis occurs as an immediate reaction to treatment for visceral leishmaniasis. FALSE: this is not a drug reaction, but a later relapse of incompletely treated infection. E. In HIV-infected patients usually cutaneous species of Leishmania can cause visceral disease. TRUE. 7. Which of the following are true of the diagnosis of leishmaniasis? A. Mucocutaneous disease can be diagnosed clinically in endemic areas. TRUE. B. On staining tissue samples the characteristic appearance of the organism is called Donovan bodies.

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TRUE. C. The sensitivity of splenic aspirates is about 50%. FALSE: it is > 90%. D. PCR has a high sensitivity and specificity. TRUE. E. Serological tests can distinguish recent acute infection from past infection. FALSE. 8. Which of the following are true of the differential diagnosis of leishmaniasis? A. Cutaneous tuberculosis may cause similar cutaneous lesions. TRUE. B. Mucocutaneous leishmaniasis is the only infection that destroys the nasal septum. FALSE: other infections include syphilis, leprosy, and paracoccidiodomycosis. C. Visceral leishmaniasis may have to be differentiated from malaria. TRUE. D. Clinical features alone are sufficient to differentiate visceral leishmaniasis from other diagnoses. TRUE. E. Noninfectious diseases can cause fever like visceral leishmaniasis. TRUE. 9. Which of the following are true of the treatment of leishmaniasis? A. All cutaneous lesions need to be treated to prevent disease progression. FALSE: cutaneous lesions can self-cure.

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B. All treatments are parenteral (i.e. need to be given by injection). FALSE: miltefosine is oral. C. Treatment courses can last up to 28 days. TRUE. D. Liposomal amphotericin B can be used to treat visceral leishmaniasis. TRUE. E. Miltefosine is less effective than other treatments for visceral leishmaniasis. FALSE: it is equi-effective with amphotericin B. 10.Which of the following are true of the control and prevention of leishmaniasis? A. Mosquito nets are sufficient to prevent sandfly bites. FALSE: the mesh is not always small enough to exclude sandflies. B. The distribution of mosquito nets to control malaria has reduced the incidence of leishmaniasis. FALSE: there is no evidence for this and in fact the incidence of leishmaniasis appears to be rising. C. Sandflies are intrinsically resistant to pyrethroid insecticides. FALSE. D. There is no effective vaccine to date. TRUE. E. Treatment of individuals with post kala-azar dermal leishmaniasis is sufficient to eliminate the reservoir of infection. FALSE: there is still an animal reservoir.

Figure Acknowledgements Figure 1. Reprint permission kindly given by the World Health Organization, Special Programme for Research and Training in Tropical Diseases, http://www.who.int/tdr/index.html image #9706290. Additional photographic credit is given to Andy Crump who took the photograph in 1997 in Sudan. Figure 2. Reprint permission kindly given by the Centers for Disease Control & Prevention, Atlanta, Georgia. Image is found in the Public Health Image Library #331. Additional photographic credit is given to Dr. Martin D. Hicklin who created the image in 1964. Figure 3. Reprint permission kindly given by the Centers for Disease Control & Prevention, Atlanta, Georgia. Image is found in the Public Health Image Library #544. Figure 4. Adapted with kind permission from the Centers for Disease Control & Prevention, Atlanta, Georgia. Image is found in the Public Health Image Library #3400. Additional photographic credit is given to Alexander J. da Silva, PhD, and Melanie Moser who created the image in 2002. Figure 5. Reprint permission kindly given by the Centers for Disease Control & Prevention, Atlanta, Georgia. Image is found in the

Public Health Image Library #6274. Additional photographic credit is given as follows: World Health Organization (WHO), Geneva, Switzerland. Figure 6. Reprint permission kindly given by the Centers for Disease Control & Prevention, Atlanta, Georgia. Image is found in the Public Health Image Library #352. Additional photographic credit is given to Dr. D. S. Martin. Figure 7. Reprint permission kindly given by the World Health Organization, Special Programme for Research and Training in Tropical Diseases, http://www.who.int/tdr/index.html image #9106015. Additional photographic data indicates that the photo was taken in Switzerland in 1990. Figure 8. Reprint permission kindly given by the Centers for Disease Control & Prevention, Atlanta, Georgia. Image is found in the Public Health Image Library #30. Additional photographic credit is given to Dr. Francis W. Chandler who created the image in 1979.