Virology is the scientific study of biological viruses. It is a subfield of microbiology that focuses on their detection, structure, classification and evolution, their methods of infection and exploitation of host cells for reproduction, their interaction with host organism physiology and immunity,
3. General features of protozoa
• The protozoa are unicellular eukaryotic cells that perform all the
physiological function. More than two lakhs protozoa are
named but only about 70 species belonging to nearly 30 genera
infect human beings Many of these protozoa are relatively
harmless but few may cause some of the important diseases of
tropical countries like malaria, kalaazar, sleeping sickness and
Chaga’s disease, etc which together threaten one quarter of the
population of the World
4. Classification of protozoa
the traditional 1980s Classification
• Based on the recommendation of the committee on Systematics
and Evolution of the Society of Protozoologists conducted by
Levine et al (1980), the protozoan parasites were classified
(Table 2.1)
• Though it satisfied the requirements of the protozoologists but
couldn’t meet some of the requirements of medical
parasitologists.
5. Corliss’s interim user Friendly Classification (1994)
• Corliss proposed a userfriendly classification trying to meet the
requirements of both protozoologists and medical
parasitologists. He divided the living creatures into six
kingdoms. Unicellular parasites (generally accepted as
protozoa) are categorized into two phylum—Archezoa and
Protozoa.
6. Molecular Classification (2000)
• The hierarchical system can be accurately represented by the
ribonucleic acid (RNA) and protein sequences of the organisms.
With advance of molecular techniques, the ribosomal RNA and
protein sequences are studied, and a new classification has been
devised. Cavalier and Smith’s six kingdoms classification—
molecular classification is based on the six kingdom theory
proposed by Cavalier and Smith (1998). They are bacteria,
protozoa, animalia, fungi, plantae and chromista.
7. Conti…….
• The unicellular protozoan parasites constitute thirteen phyla of
which the human parasites belong to seven phyla which are
distributed in three kingdoms—Protozoa, Fungi and Chromista
(Table 2.2).
8. Kingdom Protozoa
• Unicellular eukaryotic, phagotrophic, nonphotosynthetic organism
without a cell wall.
• Subkingdom Archezoa
• Unicellular eukaryotic organisms exhibiting various prokaryotic features
in ribosomes and transfer ribonucleic acid (tRNA) and lacking
mitochondria and other organelles.
• Phylum Metamonada: Unicellular intestinal flagellates (2–8 numbers)
• Phylum Parabasalia: Unicellular flagellates with one or more nuclei
and numerous flagella and parabasal body.
9. Conti……
• Subkingdom Neozoa
Unicellular eukaryotic organisms typically possessing
mitochondria and other organelles.
• Phylum Amoebozoa: Unicellular eukaryotic organisms with
pseudopodia used for locomotion and feeding
• Class Amoebaea: free living amoeba with and mitochondria
10. Conti……
• Class Entamoebidea: Obligate amoeba with secondary loss of
mitochondria
• Phylum Percolozoa: Unicellular organisms having 1–4 temporary
flagella and mitochondria but lacking Golgi bodies
• Phylum Euglenozoa: Unicellular organisms having 1–4 flagella,
mitochondria and Golgi bodies
• Phylum Sporozoa: Unicellular eukaryotic organisms possessing apical
complex made up of polar rings, rhoptries, micronemes and conoid
11. Conti……
Phylum Ciliophora: Unicellular organisms having cilia as loco
motor organ and two nuclei of different size and ploidy—(1)
macronucleus and (2) micronucleus.
12. Kingdom Fungi
• Eukaryotic heterotrophic organisms lacking plastids but
possessing cell wall containing chitin and β -glucan.
13. Kingdom Chromista
• Unicellular eukaryotic, photosynthetic filamentous or colonial,
organisms (in part “algae”); some with secondary loss of
plastids.
