Introduction to Parasitology

Each animal is a host of many parasites; thus,
there are far more parasitic organisms on earth
than there are nonparasitic organisms.

It has been estimated that more than 50% of
all living plants and animals are parasitic at
some stage during their life cycle.

There are 3 major groups of parasites:
1. Protozoa- Protozoans are microscopic onecelled organisms that are categorized
according to their method of movements
flagellates, amebas, ciliata
2. Helminths - parasitic worms such as the flukes,
tapeworms, and roundworms
3. Arthropods - insects and arachnids that are
ectoparasites and carriers (vectors) of diseases
Protozoa!
Helminths!
Arthropods!
Why do we study parasites?
• Parasites provide unique examples of
biological phenomena not found in
free-living organisms.
○ Medical Importance
○ Veterinary Importance
○ Economic Importance
Medical Importance of Parasites
• Humans are hosts to many species of
parasites.
• Many of these parasites are causative
agents of major public health problems
of the world.
Examples of Medical Importance in the
World
The life expectancy of an Egyptian is in
the mid-40's due to Schistosomes.
 15 million children in the world will die this
year from a combination of malnutrition
and parasites.
 Over 1 million African children will die this
year from the effects of malaria.
 Many cases of plague, transmitted by
fleas, still occur throughout the world.

Introduction to Mycology


Mykes (Greek word) : Mushroom
Fungi are eukaryotic protista; differ from
bacteria and other prokaryotes.
1. Cell walls containing chitin (rigidity & support) &
2.
3.
4.
5.
other polysaccharides
Cytoplasmic membrane contains ergosterols
Possess true nuclei with nuclear membrane &
paired chromosomes.
Divide asexually, sexually or by both
Unicellular or multicellular
Characteristics of Fungus
Diverse group of chemo heterotrophs > 90,000
known species
 Saprophytes: Digest dead organic matter
 Parasites: Obtain nutrients from tissues of
organisms
 Molds & mushrooms are multicellular
 Yeasts are unicellular

Fungus Everywhere
12
How the fungus are nourished
Absorption of nutrients: powerful
Exoenzyme
 Grow at lower pH-5 than bacteria
 Grow in high salt and sugar
 Metabolize complex CH2O like lignin in
wood-wood rot

FUNGI (Mycology)
- Over 100,000 fungal species
identified. Only about 100 are
human or animal pathogens.
- Most human fungal infections are nosocomial
and/or occur in immunocompromised individuals
(opportunistic infections).
Yeasts and molds

Yeasts and molds have

different structural and reproductive characteristics
 Yeast are unicellular, nucleated rounded fungi while molds
are multicellular, filamentous fungi
 Yeast reproduce by a process called budding while molds
produce spores to reproduce
 Some yeast are opportunistic pathogens in that they
cause disease in immuno-compromised individuals
 Yeast are used in the preparation in the variety of foods
Fungal Diseases
 Mycosis-
fungal infection
Not highly contagious
Humans acquire from nature
 Groups based on degree on tissue involvement
and mode of entry
 Cutaneous mycoses-dermatophytes
Epidermis, hair & nails
Contagious-direct or indirect contact
Introduction to Virology
A virus is an obligate intracellular
parasite containing genetic material
surrounded by protein
 Virus particles can only be observed by
an electron microscope

Introduction to Virology

The classification of viruses is based on
the type of nucleic acid contained within
 RNA viruses---also known as a retrovirus
 DNA viruses
Introduction to Virology

Recognizing the shape, size, and
structure of different viruses is critical to
the study of disease
 Viruses have an inner core of nucleic acid
surrounded by protein coat known as an
envelope
 Most viruses range in sizes
 from 20 – 250 nanometers
Introduction to Virology

Replication
 Viruses replicate within a host cell while
utilizing the host cell’s nucleic acids.
Introduction to Virology

Viral life cycle consists of six stages
within the host cell






Attachment
Penetration
Uncoating
Multiplication
Assembly
Release
Introduction to Virology

The cultivation of viruses is complex and
includes three common methods
 Chicken egg culture
 Cell culture
 Animal inoculation
Introduction to Virology

Viral Diseases-Examples
 Influenza
 Rabies
 HIV
 Hepatitis