2. • Parasitology branch of biology concerned with
dependence of one living on another
• Study of parasites, their host and the
relationship between them.
3. Fields of Parasitology
• Medical Parasitology
• Veterinary Parasitology
• Parasite Ecology
• Taxonomy and Phylogenetic
4. Key Definitions
• Medical parasitology: “the study and medical
implications of parasites that infect humans”
• A parasite: “a living organism that acquires
some of its basic nutritional requirements
through its intimate contact with another
living organism”.
• An organism that has sustained contact with
another organism to the detriment of the host
organism.
5. Types of Parasites
• Parasites may be simple unicellular protozoa,
or complex multicellular metazoan
• Parasites can be classified into three main
groups: protozoa, helminths, and
ectoparasites.
7. Helminths (Worms)
• Helminths are multicellular eukaryotic organisms.
• Examples include:
• Roundworms (nematodes)
• Tapeworms (cestodes)
• Flukes (trematodes)
• These parasites can cause a variety of diseases,
such as ascariasis, taeniasis, and schistosomiasis.
8. Ectoparasites
• Ectoparasites are parasites that live on the
outside of the host.
• Examples include:
• Lice (Pediculus)
• Ticks (Ixodes)
• Mites (Sarcoptes)
• Fleas (Ctenocephalides)
• Ectoparasites can transmit diseases and cause
skin irritations.
9. Key Definitions
• An ectoparasite: “a parasite that lives on the external
surface of another living organism” – e.g. lice, ticks
• Host: “the organism in, or on, which the parasite lives and
causes harm”
• Definitive host: “the organism in which the adult or
sexually mature stage of the parasite lives”
• Intermediate host: “the organism in which the parasite
lives during a period of its development only”
• Zoonosis: “a parasitic disease in which an animal is
normally the host - but which also infects man”
• Vector: “a living carrier (e.g.an arthropod) that transports a
pathogenic organism from an infected to a non-infected
host”. A typical example is the female Anopheles mosquito
that transmits malaria
11. Types of Host
• Definitive Host: The host in which the
parasite goes through its sexual cycle (I.e.,
fertilization & meiosis)
• E.g., mosquitoes serve as definitive hosts
of the malaria parasite (Plasmodium spp.)
12. • Intermediate Host: Host in which the
parasite replicates but does not go through
its sexual cycle and may multiply asexually
• E.g., mammals, including humans, serve
as intermediate hosts of the malaria
parasite (Plasmodium spp.)
13. • Reservoir host: Organism in which a parasite
that is pathogenic for some other species,
lives and multiplies usually without damaging
its host e.g rats are known carriers of
Trypanosoma cruzi, which causes Chagas
disease.
14. Vectors
• Living organism that carries disease causing
organism to a new host.
• Host that transmit parasite to man;
• Anopheles mosquito is a vector for the
parasitic disease malaria (Plasmodium
parasite)
15. Types of Vector
• Biological Vector
• Biological Vectors: These are living organisms that
transmit parasites from one host to another. Examples
include:
• Mosquitoes: Transmit diseases like malaria, dengue
fever, and yellow fever.
• Ticks: Transmit diseases like Lyme disease, Rocky
Mountain spotted fever, and babesiosis.
• Fleas: Transmit diseases like plague and typhus.
• Tsetse flies: Transmit diseases like African sleeping
sickness.
16. Mechanical Vectors:
• These are non-living objects that can passively
carry parasites from one host to another.
Examples include:
– Houseflies: Can carry pathogens on their bodies and
legs, potentially contaminating food and surfaces.
– Cockroaches: Can carry parasites like tapeworms and
roundworms in their digestive tracts.
– Dust mites: Can trigger allergic reactions and asthma,
potentially worsening symptoms in individuals with
parasitic infections.
17. Examples of Parasitic Vector-Borne
Diseases:
• Malaria: Transmitted by mosquitoes, causing high
fever, chills, and flu-like symptoms.
• Dengue fever: Transmitted by mosquitoes, causing
high fever, headache, muscle and joint pain, and a
characteristic rash.
• Lyme disease: Transmitted by ticks, causing fever,
headache, fatigue, and a characteristic bull's-eye rash.
• African sleeping sickness: Transmitted by tsetse flies,
causing fever, headaches, and neurological problems.
• Leishmaniasis: Transmitted by sandflies, causing skin
sores, fever, and weight loss.
18. Introduction to Parasite Taxonomy
• Taxonomy is the science of classifying
organisms based on their evolutionary
relationships and shared characteristics.
• Parasites are classified using a hierarchical
system that groups them into different
taxonomic levels.
19. • Taxonomic classification helps in:
• Identifying and differentiating between
different parasites
• Understanding the evolutionary relationships
and genetic diversity of parasites
• Developing targeted diagnostic tests and
treatment strategies
• Studying the epidemiology and ecology of
parasitic diseases
20. - Taxonomic Levels
• Domain
• Kingdom
• Phylum
• Class
• Order
• Family
• Genus
• Species
22. Kingdoms of Parasites
•
• Parasites are found in the following kingdoms:
• Protista (protozoa)
• Animalia (helminths, ectoparasites)
23. Phyla of Parasitic Protozoa
• Protozoan parasites belong to the following
phyla:
• Apicomplexa (e.g., Plasmodium, Toxoplasma)
• Amoebozoa (e.g., Entamoeba, Acanthamoeba)
• Excavata (e.g., Giardia, Trypanosoma)
24. Phyla of Parasitic Helminths
• Helminth parasites belong to the following
phyla:
• Platyhelminthes (flatworms: tapeworms,
flukes)
• Nematoda (roundworms)
• Acanthocephala (thorny-headed worms)
25. Parasitic arthropods belong to the
phylum
• Arthropoda, which includes:
• Arachnida (ticks, mites)
• Insecta (lice, fleas)
26. Classification of Protozoan
Sub
kingdom
Phylum Sub-phylum Class Species-
examples
Protozoa Sarcomastig-
ophora
further divided into
Sarcodina-- -
move by
pseudopodia
Rhizopods E. histolytica
Mastigophora
move by flagella
Flagellates G. lamblia
Apicomplexa
no organelle of
locomotion
Sporozoa P. falciparum,
P. vivax,
P. malariae,
P. ovale
Ciliophora
move by cillia
Ciliates B. coli
27. Classification of Helminths
Sub
kingdom
Phylum Class Genus –
examples
Metazoa
Nematodes
Round worms; appear round
in cross section, they have
body cavities, a straight
alimentary canal and an
anus
Ascaris (roundworm)
Trichuris (whipworm)
Ancylostoma (hookworm)
Necator (hookworm)
Enterobius (pinworm or
threadworm)
Strongyloides
Platyhelminthes
Flat worms; dorsoventrally
flattened, no body cavity
and, if present, the
alimentary canal is blind
ending
Cestodes
Adult tapeworms are found in
the intestine of their host
They have a head (scolex) with
sucking organs, a segmented
body but no alimentary canal
Each body segment is
hermaphrodite
Taenia (tapeworm)
Trematodes
Non-segmented, usually leaf-
shaped, with two suckers but
no distinct head
They have an alimentary canal
and are usually hermaphrodite
and leaf shaped
Schistosomes are the
exception. They are thread-
like, and have separate sexes
Fasciolopsis (liver fluke)
Schistosoma (not leaf
shaped!)
