Medical Parasitology: A Textbook

198 Pages·2017·8.272 MB·English

by  Rohela Mahmud, Yvonne Ai Lian Lim, Amirah Amir

Rohela Mahmud · Yvonne Ai Lian Lim
Amirah Amir
Medical
Parasitology
A Textbook
Medical Parasitology
Rohela Mahmud
Yvonne Ai Lian Lim • Amirah Amir
Medical Parasitology
A Textbook
Rohela Mahmud Yvonne Ai Lian Lim
Fac. of Medicine, Dept. of Parasitology Fac. of Medicine, Dept. of Parasitology
University of Malaya University of Malaya
Kuala Lumpur, Malaysia Kuala Lumpur, Malaysia
Amirah Amir
Fac. of Medicine, Dept. of Parasitology
University of Malaya
Kuala Lumpur, Malaysia
ISBN 978-3-319-68794-0 ISBN 978-3-319-68795-7 (eBook)
https://doi.org/10.1007/978-3-319-68795-7
Library of Congress Control Number: 2017961316
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Foreword
My heartfelt congratulations to the authors, Professor Dr. Rohela Mahmud, Professor
Dr. Yvonne Ai-Lian Lim and Dr. Amirah Amir, for bringing out this textbook on
medical parasitology. Why you may ask another textbook on medical parasitology
when so many already exist? The answer is simple. Most of the textbooks until
recently have been written by western authors on an academic slant without consid-
ering the actual reality and needs of students and researchers in endemic countries of
Asia-Pacific or other regions. As the authors rightly point out, the study of medical
parasitology is indeed daunting to the uninitiated, and this book aims to promote an
easy yet comprehensive way of learning the subject.
Like the authors, I have been teaching medical parasitology to medical and non-
medical students in Malaysia as well as in Southeast Asia for the past four decades,
and there was no “one” reference book that I could recommend to students on issues
related to parasitic infections in the Asia-Pacific and in particular the south-east region.
This book—well written and comprehensive—fills that gap. It will be a useful book
not just to medical students but to medical scientists, clinicians, veterinary scientists,
biologists, researchers and public health workers in tropical medicine.
This book integrates available information on parasitic diseases in the Asia-
Pacific region through reader-friendly illustrations, case reports, diagnostic
methodologies, treatment and preventive methods. With the emphasis given on
the global elimination of neglected tropical diseases (NTD) by the World Health
Organization (WHO) which affects millions of people, especially the poor in the
developing world, I hope this book will help to contribute knowledge towards
prevention, control, treatment and elimination of parasitic diseases in this region
as well as globally.
Once again, my congratulations to the authors in bringing out this book at this
timely moment.
Emeritus Dato Dr. C.P. Ramachandran
Academician Professor
Retired Chief of Filariasis Research and Control
World Health Organization
Geneva, Switzerland
v
Preface
Medical Parasitology: A Textbook is the fruit of many years of experience in teach-
ing medical students in the field of parasitology. We are teachers in one of the very
few existing departments of parasitology around the world. This book intends to
provide a systematic comprehension of the various medically important human
parasites; their distribution, morphology, life cycle, pathogenesis and clinical fea-
tures; and laboratory diagnosis, treatment, prevention and control. The main empha-
sis is on the protozoan and helminthic parasites including a brief mention of vectors
relevant to infections caused by these parasites. Ectoparasites of medical impor-
tance are also included.
The study of parasitology is daunting to the uninitiated. This book aims to promote
an easy yet comprehensive way of learning this subject. It attempts to simplify the
complexity of medical parasitology into parts that are easy to understand, integrating
the essential information of parasitic infections. This integration of knowledge will be
achieved through reader-friendly illustrations, inclusion of a collection of case reports,
samples of test questions and the images of human parasites. Essentially, the book
provides a “one-stop learning package” for medical parasitology.
This book will be useful for medical students, medical lecturers, clinicians,
researchers and also those interested in the fields of biology, zoology, microbiology,
pathology, entomology, medicine, veterinary medicine, allied sciences, tropical
medicine and public health.
We hope this book will be beneficial to a wide range of readers by giving them a
better understanding and appreciation of medically important parasites and their
infections.
Kuala Lumpur, Malaysia Rohela Mahmud
Yvonne Ai-Lian Lim
Amirah Amir
vii
Acknowledgements
We would like to express our appreciation to all staff at the Department of
Parasitology, Faculty of Medicine, University of Malaya, for their valuable advice
and comments. We are grateful to the contributors of the various case reports: Dr.
Low Lee Lee, infectious diseases consultant physician, Hospital Sultanah Bahiyah,
Kedah, Malaysia; Dr. Dharmaraj Karthikesan, cardiologist; and Dr. Giri Shan
Rajahram, infectious diseases consultant physician, Hospital Queen Elizabeth II
(Sabah Heart Centre), Kota Kinabalu, Sabah, Malaysia. Our sincere thanks also go
to Dr. Benedict Sim Lim Heng, infectious diseases consultant physician, Hospital
Sungai Buloh, Selangor, Malaysia, for providing the learning points and Dr. Amir
Abdullah, general surgeon, Clinic and Surgery, Semenyih, Selangor, Malaysia, for
proofreading the case reports.
ix
Contents
1 Introduction . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 1
2 Protozoa and Helminths . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 3
3 Amoebae . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 5
4 Intestinal and Genital Flagellates . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 19
5 Hemoflagellates . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 25
6 Malaria Parasites and Babesia . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 39
7 Coccidia . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 53
8 Microsporidia . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 71
9 Ciliate . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 75
10 Nematodes: Roundworms . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 79
11 Cestodes: Tapeworms . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 117
12 Trematodes: Flukes . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 135
13 Ectoparasites of Medical Importance . . . . . . . . . . . . . . . . . . . . . . . . . . 151
14 Case Reports . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 157
Question Bank . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 179
xi
Introduction 1
Medical Parasitology is the study of organisms that parasitize humans. According to
the definition, parasites include the viruses, bacteria, fungi, protozoa and metazoan
(helminths and arthropods). Since viruses, bacteria and fungi are not categorized as
animals, they have been incorporated into the discipline of Microbiology.
The discipline of Parasitology includes protozoa, helminths, and arthropods
whose existence depends on the availability of hosts and these are obligate para-
sites. Those which can survive and reproduce without a host are facultative para-
sites. Very few of these facultative parasites infect humans (e.g. the free-living
amoebae). Ectoparasites are referred to as parasites living on the host body surface
while endoparasites live inside the body of host. Entomology is the study of insects.
In Parasitology, insects play a role as vectors of several infections although several
are true parasites in their own right. On the other hand, acarology is the study of
ticks and mites. These are mainly ectoparasites.
Parasitic diseases have caused some of the most serious health problems in the
world today, particularly in the tropics and subtropics regions. One of the most sig-
nificant parasitic diseases, malaria, kills approximately half a million people each
year. Most of them are children under the age of 5 years in Sub-Saharan Africa.
The neglected tropical diseases (NTDs) include parasitic diseases such as
Chagas’ disease, cysticercosis, echinococcosis, human African trypanosomiasis,
schistosomiasis, leishmaniasis, soil-transmitted helminthiasis, lymphatic filariasis,
and onchocerciasis. These NTDs affect more than one billion people, mostly in
rural areas of low socio-economic countries, trapping one sixth of the world’s popu-
lation in a vicious cycle of poverty and neglect.
Though not in all cases, parasitic diseases are mostly confined to developing
countries. However, geographic distributions of parasitic diseases are evolving and
changing due to ease of international travel and influx of refugees and migrants to
developed countries for leisure, education, and economic reasons. Gastrointestinal
diseases, liver diseases, vector-borne diseases, scabies, and tuberculosis are com-
mon among migrants. Inbound migrants may harbour long-eliminated diseases in
the host country which may still be endemic in their country of origin and the
© Springer International Publishing AG 2017 1
R. Mahmud et al., Medical Parasitology,
https://doi.org/10.1007/978-3-319-68795-7_1
2 1 Introduction
importation of infection may cause problems in diagnosis, transmission, prevention,
and control.
Another important contributing factor to the high incidence of parasitic infec-
tions is the prevalence of opportunistic infections such as toxoplasmosis, strongy-
loidiasis, microsporidiosis, and cryptosporidiosis in the immunocompromised
especially HIV/AIDS patients. HIV/AIDS remains one of the world’s most signifi-
cant public health challenges, particularly in low- and middle-income countries.
More than 36 million people were living with HIV at the end of 2015. The group of
people was at high risk of acquiring opportunistic parasitic infections.
Occurrence of zoonotic parasitic infections is also a challenge. In 2004, a large
focus of zoonotic P. knowlesi (simian malaria) infection was reported in humans in
Sarawak, Malaysia. Since then, many human cases have been reported in various
Southeast Asian countries. This malaria parasite is capable of producing severe dis-
ease and can be fatal. Due to the similar morphological features of its early stage to
P. falciparum and late stage to P. malariae, microscopic diagnosis is a challenge. In
many instances, molecular technique is used to confirm the species.
In addition, there are other parasites that have been reported to cause zoonosis in
humans which include cysticercosis, cryptosporidiosis, microsporidiosis, hydatid
disease, trichinellosis, babesiosis, toxoplasmosis, and cynomolgi malaria. Clinicians
have to be aware of these zoonotic infections to make early diagnosis and prompt
treatment. Public health personnels have to be more alert and vigilant regarding
these zoonotic infections to ensure that they do not cause any outbreak.
In diagnosis of parasitic infections, microscopic identification of the organisms
based on their morphological characteristics remains the gold standard. In Parasitology,
in vitro culture was for a long time virtually impossible for most parasites. Nevertheless,
in recent years, technical advances have allowed the in vitro cultivation of protozoan
parasites (e.g. Plasmodium, Giardia, Toxoplasma, Cryptosporidium, Blastocystis)
including helminths. The culture techniques for helminths are still in their infancy and
are carried out mostly for research, rather than for routine laboratory diagnosis.
In recent years, diagnostic tools for parasitic infections have been improved with
the introduction of molecular techniques such as polymerase chain reaction (PCR).
PCR is an upcoming diagnostic tool that can be used to confirm parasitic infections.
Molecular techniques are also increasingly being used for species identification or
strain-typing. Immunological technique using monoclonal antibodies to detect spe-
cific antigens has also been found useful for rapid diagnostic test of malaria and
filariasis.
This textbook presents essential information on parasites of medical importance.
It is meant for medical students, medical educators and clinicians as a reference for
parasitic infections. Case reports are also included in the handbook to provide real-
life clinical scenarios for reference.
It is hoped that readers will find this book helpful and of practical use.