Pox diseases are caused by viruses in the family Poxviridae. Poxviruses that affect animals include sheep pox virus, goat pox virus, and vaccinia virus. Sheep pox and goat pox viruses cause significant disease in sheep and goats, characterized by fever and pox lesions on skin and mucous membranes. The diseases can spread rapidly between animals through direct contact or indirect contact with contaminated materials. Diagnosis involves identifying characteristic lesions and isolating virus from samples. Vaccines are available and used to control outbreaks.

1. Faculty of Veterinary Medicine & Animal
Husbandry
Somali National University
Mogadishu, Gaheyr Campus
Sep. 21. 2019
INFECTIOUS DISEASES II (Viral Diseases)
POX DISEASES

2. Pox diseases are acute viral diseases that
affect many animals, including humans and
birds, but not dogs.
They are caused by viruses of the family
Poxviridae, which includes several viruses
of veterinary and medical importance.

3. Pox viruses are the largest and most complex of
known animal viruses.
 They are Large, enveloped (some virions
contain double envelope), double-stranded
DNA viruses
 The capsid / nucleocapsid is brick-shaped to
ovoid containing the genome and lateral bodies
(function unknown).
 They are the only DNA viruses known to
complete their replication cycle in the
cytoplasm.
 Poxviruses remain viable in scabs for long
periods.

4. Pox diseases are of considerable economic
importance in some regions of the world.
Typically, lesions of the skin and
mucosae are widespread and progress
from macules to papules, vesicles, and
pustules before encrusting and healing.
 Most lesions contain multiple
intracytoplasmic inclusions, which
represent sites of virus replication in
infected cells.

5.  Strains of poxvirus with reduced virulence
are used to immunize against some infections,
the classic example being the global
eradication of smallpox in humans by
immunization with strains of live vaccinia
virus.
 The family is divided into two subfamilies -
the Chordopoxvirinae infecting vertebrates,
and the Entomopoxvirinae infecting insects.

6. The Chordopoxvirinae are divided into the
following genera:
MembersGenera
Cow pox (vaccinia variola), Horse pox, camel and buffalo pox,
rabbit pox.
Orthopox
Orf (sheep), bovine pustular stomatitis, Pseudocowpox /
milker's nodules
Ectromelia / mouse pox(An important disease of laboratory
and wild mice)
Parapox
Sheep pox, goat pox, Lumpy skin disease.Capri pox
Swine pox.Suipox
Fowl pox, pigeon pox, turkey pox and other galliformesAvipox
Myxoma virus, rabbit (Shope) fibroma virus.Leporipox

7. Para-, Capri- and Leporipox viruses are
ether sensitive, but otherwise all pox
viruses are stable and very resistant to
temperature change, particularly in dry
conditions. They last months or years in
dust.

8. Poxviruses can be transmitted between animals by
several routes:
 By introduction of virus into small skin abrasions
from other infected animals or from a
contaminated environment (e. g., Orf ),
 By droplet infection of the respiratory tract (e. g.,
Sheep pox),
 Through mechanical transmission by biting
arthropods (e.g., swinepox, fowl pox, and
myxomatosis).

9. Cowpox

10. The virus of cowpox is closely related
antigenically to vaccinia and smallpox
viruses.
Vaccinia virus had been used for
vaccination against smallpox and it was
observed that, some outbreaks in cows
were due to infection with vaccinia from
recently vaccinated persons.

11. In this mild, eruptive disease of dairy
cows, lesions occur on the udder and
teats. Although once common, cowpox is
now extremely rare and reported only in
Western Europe.

12. • The disease spreads by contact during milking.
• After an incubation period of 3-7 days, during
which cows may be mildly febrile, papules
appear on the teats and udder.
• Vesicles may not be evident or may rupture
readily, leaving raw, ulcerated areas that form
scabs.
• Lesions heal within 1 month.
• Most cows in a milking herd may become
affected. Milkers may develop fever and have
lesions on the hands, arms, or face.

13. • Cowpox or vaccinia infection may be
confused with bovine herpes
Mammillitis; because the lesions are
superficially similar, laboratory
confirmation is required.
Pseudocowpox is a milder disease.
Measures to prevent spread within a herd
must be based on segregation and hygiene.

14. Pseudocowpox
(Milker's nodes, Paravaccinia)

15. This common, mild infection of the udder
and teats of cows is caused by a Parapoxvirus
and is widespread worldwide.
The virus of Pseudocowpox is related to
those of contagious ecthyma and bovine
papular stomatitis.

16.  Lesions begin as small, red papules on
the teats or udder.
 These may be followed rapidly by
scabbing, or small vesicles or pustules
may develop before scabs form.
 Scabs may be abundant but can be
removed without causing pain.

17.  Granulation occurs beneath the scabs,
resulting in a raised lesion that heals from
the center and leaves a characteristic
horseshoe or circular ring of small scabs.
 Some lesions persist for several months,
giving the affected teats a rough feel and
appearance .

18.  The infection spreads slowly throughout
milking herds and a variable percentage of
cows show lesions at any time.
 The scabbed lesions may be confused with
mild traumatic injuries to the teats and
udder.
 Scabs examined with an electron
microscope frequently show characteristic
virus particles.

19. Control of infection within a herd is difficult
and depends essentially on hygienic
measures, such as teat dipping, to destroy the
virus and prevent transmission.
Little immunity appears to develop.

20. Sheep and Goat Pox
 Sheep pox and goat pox are highly contagious
viral diseases of sheep and goats, clinically
characterized by fever, ocular and nasal
discharges.
 Pox lesions appear on the skin and on the mucosa
of the respiratory and gastro-intestinal tracts.
 They result in high morbidity and mortality,
reduced productivity and poor quality of wool.

21. SGP - Etiology
SGP result from infection by sheep-pox virus
(SPV) or goat-pox virus (GPV)
Those viruses are closely related members of the
Capripox genus in the family Poxviridae
SPV and GPV cannot be distinguished from
each other with serological techniques, this why
it has been thought they are strains of single virus

22. Genetic sequencing has now demonstrated
that these viruses are distinct
SPV and GPV are closely related to the
virus that causes lumpy skin disease in
cattle LSDV

23. SGP - Etiology
Pox Virus

24. Occurrence:
The disease is endemic in southern Europe,
Africa north of the equator and in parts of
Asia such as Iran, India and neighboring
countries.

25. SGP - Hosts
Capripoxviruses cause disease only in
Sheep and goat
Many SPV isolates are specific for sheep
and many GPV strains are specific for
goats
But some strains of these viruses readily
affect both species
Infections have not been reported in wild
ungulates

26. SGP - Distribution
SGP are found in parts of
Africa, Asia, Middle East, Indian subcontinent

27. Transmission:
 The sheep-specific disease is an air-borne
infection and transmission most readily
occurs when there is direct contact
between sick and healthy sheep.
 In addition, however, indirect contact
with infected dust spreads the disease.

28.  Some strains of the virus type that infects
both sheep and goats do not spread readily
by contact and an unknown biting
arthropod is believed to be the major
disseminator.
 Intra-uterine infection occurs and lambs
have been born with developed pocks.

29.  Infected animals do not become chronic
carriers.
 The hair or wool of recovered sheep,
however, is usually contaminated with the
virus and the contamination persists for
many months.

30. Epidemiology:
 Animals are most infectious soon after the
appearance of papules, during the 10-day period
before the development of significant levels of
protective antibody.
 High titres of virus are present in papules, and
those on the mucous membranes quickly ulcerate
and release virus in nasal, oral and lachrymal
secretions, and into milk, urine and semen, which
all constitute important sources of virus
dissemination.

31. Animals that develop generalized lesions
produce considerable quantities of virus
and are highly infectious and all constitute
important sources of virus dissemination.
The virus is very resistant and remains
viable for long periods, on or off the animal
host; for example, they may persist for up
to 6 months in shaded animal pens, and for
at least 3 months in dry scabs on the fleece,
skin and hair from infected animals.

32. There is no evidence for the existence of
animals persistently infected with GPV or
SPV (i.e. there is no carrier state).

33. Clinical features:
 The incubation period is seven days.
 Clinical reactions may be peracute, acute,
or subacute and mortality can vary from 5
to 80 per cent.
 Lesions as well as mortality tend to be
more severe in lambs than in adult sheep.

34. Peracute infections occur in indigenous
lambs and in exotic sheep imported into
the endemic area or affected in a wave of
a virgin epidemic.
They are characterized by generalized
hemorrhages, widespread cutaneous
ulceration and death.
The course is usually too short for pocks
to develop.

35.  The onset of acute reactions is sudden and
manifested by a high fever, nasal and
ocular discharges, and salivation.
 Fever is usually followed by cutaneous
eruptions beginning with erythematous
areas especially noticeable in hair or
wool-free parts of the body.

36.  Papules appear 24 hours later on mucous
membranes and the thin-skinned areas of
the body.
 Papules may transform into vesicles.
 After rupture of vesicles, a thick crust
covers the lesions.
 Necrosis and sloughing of the nodules
leaves a hairless scar.

37.  Within a week the fever regresses and the
papules are crusted with exudate.
 Pox lesions are seen on mucous
membranes of the eyes, mouth, nose,
pharynx, epiglottis, trachea, on the
ruminal and abomasal mucosae, and on
the muzzle, nares, in the vulva, prepuce,
testicles, udder, and teats.

38. Pox Lesions

39. Sheep, inguinal skin. Several coalescing macules contain
petechiae.

40. Sheep, inguinal skin. There are several coalescing macules.

41. Sheep, scrotum. There are multiple papules on the scrotum and
adjacent inguinal skin.

42. Sheep, scrotum and inguinal skin. There are multple red brown
papules. There are two hemorrhagic ulcers on the medial aspect
of the stifle.

43. Goat, skin. Pox are coalescing red papules with central,
slightly depressed, pale (necrotic) areas.

44. Goat. Two pox on the ventral tail have desiccated, dark red,
undermined (necrotic and sloughing) centers.

45. Goat, udder. The skin contains two sharply demarcated necrotic
foci (subacute pox).

46. Goat, muzzle. The muzzle contains several papules and is
partially covered by hemorrhagic nasal exudate.

47. Pox Lesions

48. Pathology:
The lesions of goat pox are not restricted to
the skin, but also may affect any of the
internal organs, in particular the
gastrointestinal tract from the mouth and
tongue to the anus, and the respiratory
tract.
Necropsy reveals skin lesions that may
involve the full depth of the epidermis,
dermis and adjacent muscle.

49. Postmortem lesions usually include
tracheal congestion, small-sized bullet-
shaped nodules and white patches on
lungs, inflamed spleen and lymph nodes
with greying white necrotic lesions and
increased quantity of blood-tinged
pleural fluid.
In some animals, lesions develop in the
lungs as multiple consolidated areas.

50. Lung. There are numerous, small, coalescing, red-tan,
consolidated foci (pneumonia).

51. Lungs. The lungs contain multiple discrete turn to red-brown nodules
(multifocal interstitial pneumonia). Mediastinal lymph nodes are enlarged.

52. Lung. There are multiple red-brown consolidated foci
(multifocal pneumonia).

53. Sheep, lung. The numerous widely disseminated discrete round
tan foci are foci of pneumonia; a few have pale (necrotic) centers.

54. Sheep, lungs. Lungs with diffuse granulomatous nodules.

55. Diagnosis:
 The provisional diagnosis is based on the history,
clinical signs and post mortem lesions and
confirmation is seldom sought.
 When necessary early pocks are examined
histopathologically.
 They may also be diffused through agar against
known sheep pox antiserum.
 Virus can be isolated from pocks by inoculating
suspensions treated liberally with antibiotics into
tissue cultures of lamb testicular cells.

56. Differential diagnosis:
Other skin infections rarely exhibit the
explosive character of virgin epidemics of
sheep pox but in endemic areas contagious
pustular dermatitis, mange, cutaneous
streptothricosis and bluetongue often create
difficulties in differential diagnosis.

57. Lab. Diagnosis:
 Specimens to submit for laboratory
diagnosis (virus isolation) can include
biopsy tissue material, but autopsy
specimens collected from one or two
severely affected acute cases are preferable.
Biopsy specimens should include samples
from two or three lesions at the papular or
vesicular stage.

58. Skin lesions should be clipped, and
cleansed with a non-disinfectant soap and
rinsed with water.
 Blood (with added anticoagulant) should
be collected aseptically from early febrile
cases.
Biopsy specimens should include lesions
from skin, turbinates, trachea, lungs and
enlarged lymph nodes.

59. A number of tests have recently evolved
which employ the soluble antigen fraction
and its antiserum for the diagnosis of goat
pox.
The detection of GPV and SPV or their
antigens may be performed by virus
isolation and neutralization in cell culture
(lamb/kid testis/kidney cells), fluorescent
antibody or electron microscopy.

60. Molecular biology tools such as
polymerase chain reaction (PCR)-based
diagnostic methods are extremely useful
for the detection of the viral nucleic acid
of GPV .

61. Immunology:
 Each type of virus induces a durable active
immunity in surviving animals but there is no
cross-protection between the two major types.
 The virus that infects both sheep and goats is,
however, related antigenically to a specific goat
pox virus to the extent that the goat pox virus
will protect sheep against sheep pox but the
sheep pox virus does not protect goats against
goat pox. It is also related to the Neethling virus
of bovine lumpy skin disease.

62. Control:
 Both live and inactivated vaccines are
available.
 The former are usually administered by
scarification and the induced resistance is
reasonably durable.
 Inactivated vaccines containing adjuvants
can confer resistance for about a year

63. Low-risk areas ensure their freedom from
sheep pox by prohibiting the importation of
sheep and goats from endemic areas.
In high-risk areas control is difficult if
flocks are herded communally or are
owned by nomads; infected animals should
be destroyed and in-contact animals should
be vaccinated.
In the endemic areas prophylactic
vaccination is recommended.