Poxviruses are large, brick-shaped viruses that cause diseases characterized by skin lesions, including smallpox, monkeypox, and cowpox. They are resistant to certain conditions and share common antigens, which can be cultivated in chick embryos and tissue culture. Smallpox, caused by variola major and minor, was declared eradicated in 1980 due to effective vaccination and surveillance measures.

1. POXVIRUSES

2. Introduction
 Largest viruses that infect vertebrates
 Can be seen under light microscope
 Poxvirus diseases are characterized by skin lesions –
localized or generalized
 Important diseases caused by poxviruses are-
 Smallpox
 Monkeypox
 Cowpox
 Tanapox
 Molluscum contagiosum

3. Morphology
 Poxviruses are brick shaped
 Largest animal viruses & can be seen under
light microscope
 In vertical section poxviruses have a biconcave
double stranded DNA core surrounded by a
double layered membrane
 Envelope is the outermost layer & surrounds
the outer membrane

5. Resistance
 May remain viable for months at room temp.
 Survive for years in freeze dried form
 They are susceptible to UV light & are
 Resistant to 1% phenol but readily inactivated
by formalin
 Though poxviruses are enveloped, they are not
inactivated by ether

6. Antigenic Structure
 All poxviruses share a common nucleoprotein
(NP) antigen
 Other antigens include –
• LS antigen - a complex of the heat labile (L)
and the heat stable (S) antigens
• Agglutinogen
• Haemagglutinin

7. Cultivation
 They grow in chorioallantoic membrane
(CAM) of chick embryo and in tissue culture
 Variola and vaccinia viruses produce pocks on
the CAM in 48-72 hours
 Variola pocks are small, shiny ,white, convex,
non-necrotic & non-hemorrhagic
 Vaccinia pocks are larger, irregular, grayish,
flat, necrotic & sometimes hemorrhagic

8. Cultivation………
 Tissue culture of monkey kidneys
 HeLa & chick embryo cells can be used
 Cytopathic effects are produced by vaccinia in
24-48hrs but variola takes longer time to
produce these changes
 Eosinophilic inclusion bodies (Guarnieri
bodies) can be seen in stained preparations

9. Diseases caused by Pox Viruses
 Small Pox
 Vaccinia
 Monkeypox
 Cow Pox
 Milker’s Node
 Molluscum Contagiosum

10. Difference Between Small Pox & Chicken Pox

11. Small Pox
 An infectious disease unique to humans, caused by
either of two virus variants, Variola major and
Variola minor.
 localizes in small blood vessels of the skin and in
the mouth and throat.
 in the skin, this results in a characteristic
maculopapular rash, and later, raised fluid-filled
blisters. V. major produces a more serious disease
and has an overall mortality rate of 30–35%. V.
minor causes a milder form of disease

12. SMALL POX…….
 Variola major last natural
case detected in 24th May 1975
 Variola minor last case
occurred in Somalia, in
October 1977
 On 8th May 1980 WHO
formally announced the global
eradication of smallpox

13. Eradication achieved because of -
 No sub-clinical infection or carrier state
 An effective vaccine – originally discovered
by Jenner in 1796
 No animal reservoir
 Aggressive surveillance-containment measures
 Two laboratories still hold the stock of variola
virus – WHO Collaboration Centre in Atlanta,
USA & Koltsovo, Russian Federation

14. Vaccinia of Knee

15. Cow Pox Of the upper Arm

16. Cow Pox of the Udder

17. Haemmorrghic Small Pox

18. VACCINIA VIRUS
 Vccinia virus was used for small pox
vaccination
 It may have evolved from cowpox or smallpox
virus
 It causes a localized skin infection
 Employed as a vector for the development of
recombinant vaccines

19. Prophylaxis of Smallpox
 Both variola & vaccinia viruses can be grown
on CAM of chick embryo
 Vaccination with vaccinia induces protection
against smallpox for about five years
 Natural infection of smallpox gives complete
protection against re-infection

20. Cowpox
 Produces ulcers on the teats & udders
 Human infection acquired by the process of
milking
 Localized lesions on the hands of man
 Undergo changes from macules to pustules
 Rodents are the reservoir hosts of cowpox
virus

21. Human Monkeypox
 Infection acquired by handling infected
animals
 Resembles mild smallpox

22. Human MonkeyPox
 Monkey pox - is a rare smallpox like disease
of children in central Africa. It is acquired
from monkeys but does occasionally spread
from man to man in unvaccinated
communities. Antigenically it cross-reacts
with other poxviruses.

23. MONKEY POX

24. Orf
 It is a contagious pustular dermatitis of sheep
& goats
 In man , disease occurs as a single lesion on
finger or hand or occasionally on the face

25. ORF
 ORF - a worldwide occupational disease
associated with handling sheep and goats
afflicted ". In humans it manifests as a single
painless, papulo-vesicular lesion on the hand,
forearm or face.

26. Bulla Caused by orf virus infection

27. Milker Node
 Pseudocowpox - occurs worldwide and is a
disease primarily of cattle. In humans it
causes non-ulcerating "milker's nodes".

28. Milker Nodule of Hand

29. Molluscum contagiosum
 It is a benign epidermal tumour-like lesion
 It mainly involves the arms, legs, buttocks &
genital area
 It is a contagious disease
 Virus is also transmitted sexually in adults
 Nodules show hyaline acidophilic inclusion
bodies (molluscum bodies) within the
proliferated epidermal cells

30. Molluscum Contagiusm of Face

31. Molluscum Contagisum of Penis

32. Molluscum Contagiusm of Labia

33. Prophylaxis
 Vaccination with vaccinia induces protection
against small pox .