Animal viruses are intracellular parasites that depend on host cells for replication, classified into seven groups based on their nucleic acid and transcription methods. Examples include dsDNA viruses like adenoviruses and herpes viruses, which can cause various diseases such as respiratory illness and chickenpox. Other virus groups include ssDNA, (+) ssRNA, (−) ssRNA, dsRNA, and reverse-transcribing viruses, each associated with specific viral characteristics and diseases.

2. ANIMAL VIRUSES
Animal viruses are self replicating,
intracellular parasites that completely
rely on host animal cell for
reproduction. They use the host's
cellular components to replicate, then
leaves the host cell to infect other
cells.

3. THE BALTIMORE CLASSIFICATION OF VIRUSES
Animal viruses are classified in the following 7 groups
according to relationship between virion, nucleic acid
& mRNA transcription :
Group1. ds DNA viruses
Group2. ss DNA viruses
Group3. ds RNA viruses
Group4. (+) sense ss RNA viruses
Group5. (-) sense ss RNA viruses
Group6. ss RNA reverse transcribing viruses
Group7. ds DNA reverse transcribing viruses

4. Group1. ds DNA viruses:the mRNA
is synthesized on a ds DNA genome
template.following are eg. Of some
viruses 1. adenoviruses
2.herpes virus
3. papovavirus
4. poxvirus

5. 1. Adenoviruses
• virions are naked ,
non enveloped. 90-100
nm diameter & have
icosahedral symmetry.
•The penton fibers with
a globular head are
involved in the process
of attachment of the
virus to the host cell.
•Hexons consists of
protein II with a central
core, invoved in the
stabilization & assembly
of particles.

6. Diseases caused by adenoviruses are :
1. respiratory disease
2.conjunctival pneumonia
3.acute hemorrhagic cyctitis
4.acute gastroenteritis

7. 2.Herpes virus
•The nucleocapsid is spherical
icosahedral &100 nm in
diameter , enclosed in
glycoprotein lipid envelop.
•Glycoprotein are visible as
“spikes” that are projected from
the surface.
•The nucleic acid is linear ds
DNA which is converted into a
circular DNA molecule upon
slight digestion .
•Disease caused by herpes virus
: herpes simplex I ( cold sores),
herpes simplex II (genital sores)
& varicellovirus (chicken pox.
Shingles) .

8. 3. Papovavirus
• Capsid is of 45-55 nm
diameter, naked ,
icosahedral, virion
consists of DNA &
protein. capsid is made
up of 72 capsomers.
•Virus enter the cell &
migrates to the nucleus
for replication.
•Disease:
•Papilomavirus (cervical
cancer,human warts)
•Polyomavirus (cause
tumor in mice)

9. 4. poxvirus
•Poxvirus are brick
shaped (240-
300nm),dsDNA genome
(130-260kb) & naturally
associated with enzyme
•Virions are enveloped .
Viral multiplication is
started by viral
transcriptase, the viral
components are
synthesized & assemble
in the cytoplasm of the
host cell.
•Pathogenesis:
•Human monkey pox
•Smallpox (variola virus)

10. Grpoup 2. ssDNA
virus: parvovirus
•Parvovirus are linear,
average genome size of
5000 nucleotide,
smallest virus with 18-
28 nm diameter.
•Viral capsid s made up
of 2-4 protein form
naked icosahedral
structure.
•Diseases:
•Human parvovirus B19
•Erythema infectiosum
•Joint disease syndrome

11. Group3. (+) ss RNA
virus:1. corona virus
•Corona virus are
enveloped, helical &60-
200 nm
diameter.genomes size
are 16-21kb.
•it replicates in the
cytoplasm.
•Diseases :
•Respiratory syndrome
•Severe acute
respiratory syndrome

12. 2.Picorna virus
Virions naked
,icosahedral. Capsid is
composed of 60 copies of
4 structiural protein .
Viral genome are linear
7.1-8.9 kb size
Diseases:
poliovirus (polio)
Rihinovirus( common
cold)
Hepatitis A virus
(hepatitis A)

13. 3.Togavirus
•Envelop consists of 80
trimer spikes . The
spikes consists of
glycoprotein that help
in attachment protein
to receptor of host cell
membrane.
•Eg. Alpha virus
•Eastern equine
encephalitis virus
•Yellow fever virus
•Rubella virus

14. Group 4. (-) ssRNA
viruses
1.Rhabdovirus
Envelop with spikes
made up of gly coprotein
linked matrix protein
contain nucleocapsid
Eg. Mumps virus , rabies
virus

15. 2. Orthomyxo virus

16. Group 5. ds RNA virus :eg. reovirus
Group6. ss RNA RT virus : eg.reterovirus
Group 7. ds DNA RT virus: eg Hepadna
virus.