Page 10 - Medical Parasitology_ A Textbook ( PDFDrive )

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.