Poxviral infections
Introduction
Highly epitheliotropic virus
Causing cutaneous and systemic disease in birds, wild
and domestic mammals and humans.
Family: Poxviridae
Subfamily: Chordopoxvirinae
Genus:
- Orthopoxvirus
- Parapoxvirus
- Avipoxvirus
- Capripoxvirus
- Leporipoxvirus
- Suipoxvirus
- Family:
Poxviridae
- Subfamily:
Chordopoxvirinae
- Genus:
1)
Orthopoxvirus
§ Camelpox virus
§ Cowpox virus
§ Ectromelia virus (mousepox virus)
§ Monkeypox virus
§ Vaccinia virus (buffalopox virus, rabbitpox virus)
2)
Parapoxvirus:
- Orf
virus / contagious pustular dermatitis virus / contagious
ecthyma virus
- Pseudocowpox
virus (milker's
nodule virus)
- Bovine
papular stomatitis virus
- Parapox
virus of red deer
- Sealpox
virus
- Virus
causes papillomatous dermatitis and pododermatitis in cattle
- Others
3)
Avipoxvirus:
- Fowlpox
virus, Pigeon-pox virus, and many other avian poxviruses.
4) Capripoxvirus: Most severe infection
- Sheeppox
virus
- Goat
pox virus
- Lumpy
skin disease virus
5)
Leporipoxvirus:
- Myxoma
virus; Rabbitfibroma virus (Shope fibroma virus)
6) Suipoxvirus: Swinepox virus.
7) Molluscipoxvirus: Molluscum contagiosum virus
8) Yatapoxvirus – Tana pox virus, Yaba monkey tumor virus
Sheeppox and
Goatpox
OIE listed diseases
Synonyms
ü Capripox infection
Sheep pox is an acute to chronic, contagious, systemic
disease characterized by generalized pox lesions throughout the skin
(especially sparsely haired areas) and mucous membranes, persistent fever,
lymphadenitis, and often pneumonia
Etiology:
Sheeppox virus and Goatpox virus – ds DNA
Genus: Capripox
virus
Family: Poxviridae
Host:
ü Sheep and Goat
Transmission
ü Close contact
ü Inhalation of aerosols
ü Abraded skin
ü Fomites
ü Insects (mechanical)
ü Virus infection is present in all secretions, excretions and
scabs
Pathogenesis
Introduction of virus into skin or respiratory tract
⇓
local viral
replication seen in epidermis, dermis,
or respiratory system epithelium
⇓
passes to regional lymph nodes and reticuloendothelial
cells via macrophages
⇓
replicates in cytoplasm
⇓
exits via
efferent lymphatics into blood
⇓
Virus
disseminated in to body and replicate in skin and lungs
⇓
Virus enter in to skin through infected macrophages
⇓
Virus
replication in epidermis
⇓
Infected cells release cytokines
⇓
Cytokines
induced vasodilation, Increased vascular permeability and leukocytes chemotaxis
⇓
Edema,
diapedesis and hemorrhages
⇓
Formation of macular lesions
⇓
Epidermal cells undergone ballooning and reticular
degeneration
⇓
Formation of papule
⇓
Necrosis of
affected cells of epidermis
⇓
Necrotic space
filled by fluid
⇓
Vesicle
formation
⇓
Neutrophilic
infiltration in vesicle
⇓
Pustule
formation
⇓
Hyperplasia of
viral infected epidermal cells
⇓
Epidermal
hyperplasia
⇓
Pustule
enlarged and ruptured
⇓
Scab formation over epidermis
⇓
If not complicated, healed within moths
⇓
Vesicles and pustules are very fragile, present for
only few hours or some time not seen
⇓
In lung induced pneumonia by viral replication and
inflammation
✔️
Clinical Signs
Initial clinical signs include
✔️ Fever
✔️ Oculonasal, seromucous discharge
✔️Increased respiratory rate
✔️ Salivation and
✔️ Hyperesthesia.
Vesicular stage:
✔️ Generalized prominent
✔️ Umbilicated, multilocular vesicles and
✔️ Cutaneous nodules (0.5-1.5 cm in diameter)
Pustular phase: Vesicles become covered by a thin crust, may coalesce
and may persist for up to 6 weeks.
In animals that recover, these lesions ultimately heal
leaving permanent depressed scars.
Death is due to secondary bacterial infections
(septicemia and/or pneumonia).
Macroscopic Pathology
Most
lesions confined to sparsely wooled skin and mucous membranes
Sheep
pox lesions have a prominent vesicular stage followed by a pustule stage
cauterized by a thin crust with marked, gelatinous dermal edema
Approximately
one-third of the animals develop respiratory lesions that may be severe and
extensive; miliary foci of consolidation as the result of hematogenous
infection
Mediastinal
lymph nodes are enlarged, congested, hemorrhagic, and edematous.
Renal
lesions: multifocal, circular, fleshy nodules throughout cortex
Microscopic Pathology
Cutaneous lesions:
Epidermis showed marked hydropic degeneration of
keratinocytes, acanthosis, microvesiculation, eosinophilic intracytoplasmic
inclusion bodies (ICIB), hemorrhage, and pustule formation.
During the papular phase, there is extensive dermal
edema, and the accumulation of large numbers of mononuclear cells around blood
vessels and between collagen bundles.
These cells (sheep-pox cells, cellules claveleuses
or Borrel cells), have vacuolated cytoplasm with intranuclear inclusions
and vacuolated nuclei with marginated chromatin.
Sheep-pox cells are virus-infected monocytes,
macrophages, and fibroblasts
Severe necrotizing vasculitis develops in arterioles
and post-capillary venules often resulting in ischemic necrosis of the dermis
and overlying epidermis
Pulmonary Lesions
Pulmonary lesions: proliferative alveolitis and
bronchiolitis with areas of focal caseous necrosis
Alveolar septal cells may contain intracytoplasmic
inclusions
Pseudocowpox
Etiology: Pseudocowpox virus, a Parapoxvirus
Host: Cattle
Macules and papules on teats, udder, and perineum
Decreased milk production
Lesions may heal within 6 weeks
Transmission to people induces "milker's
nodule."
Cowpox
Etiology: cowpox virus, Orthopoxvirus
Host: Wild and domestic cattle and other animals like
dog and cats
Macules and papules on teats, udder
Decreased milk production
Cat developed more severe infection than cow
Cutaneous and respiratory form seen
Buffaopox
Etiology: Buffalo pox
virus, Orthopoxvirus
Host: Buffaloes
In India it is
considered to be an emerging enzootic virus
Lesions on teats,
udder, medial aspects of the thighs, lips and muzzle
Zoonotic virus
Swinepox
Etiology: swinepox
virus, Suipoxvirus
Host: Swine; young
and growing piglets
Gross lesions: affect
the ventral and lateral abdomen, lateral thorax, and medial foreleg and thigh.
Diagnosis
Clinical signs
Laboratory tests
Virus isolation
Virus neutralization
Enzyme-linked
immunosorbent assay (ELISA)
Polymerase chain
reaction
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