Poxviridae Flashcards
How is it possible for poxviruses to replicate in the cytoplasm
Unlike other DNA viruses, poxviruses have evolved to encode the enzymes required for transcription and replication of the viral genome
Pathogenesis of contagious ecthyma
Macule → Papule → Vesicle → Pustule → Ulcer → Scab
Damage of skin essential to infection
Cellular response with necrosis and sloughing of the affected epidermis and underlying stratum papillare of the dermis
Cutaneous response to infection includes a delayed type hypersensitivity reaction and influx in inflammatory cells
Transmission of contagious ecthyma
Scabs that fall off contain less virus
Virus stable in environment
Transmitted on contaminated instruments
Spread rapidly
Infects healthy animals through damaged skin
Oral lesions infect lambs or kids result from nursing
Subfamily of Poxviridae that infects vertebrates
Chordopoxvirinae
Venereal form of ulcerative dermatosis
Venereally transmitted ulceration of the prepuce and penis or vulva
Rarely, the ulcers may extend to the glans penis so that the ram becomes unfit for natural breeding
Ewes- edema, ulceration and scabbing of the vulva have less serious consequences
Properties of Parapoxviruses
Ovid
Covered with long thread-like surface tubules
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Appear to be arranged in crisscross fashion, resembling a ball of yarn
How are poxviruses transmitted?
Skin
Respiratory route
Mechanically transmitted
Two distinct infectious pox viruses
Intracellular Mature Virus (IMV)
Extracellular Mature Virus (EMV)
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Both forms are infectious
Describe the skin lesions of poxvirus infection
Degenerative changes in the epithelium
Rupture of the pustule can pre-dispose to secondary bacterial infection
Ulceration may develop
Clinical signs of lumpy skin disease
Fever
Multiple nodular lesions on skin and mucous membrane
Lymphadenopathy
Contagious ecthyma disease in humans
Macropapular lesions and large nodular lesions
Healing occurs without scarring
Secondary bacterial infections
Parapoxviruses are what shape
Ovoid
Transmission of Ulcerative Dermatosis of Sheep
Virus infection through damaged skin or by coitus
Primary lesions of cowpox in cats
History of primary skin lesion
Small, scabbed wound to large abscess
Distribution of swinepox
Worldwide
Widespread sporadic disease
Prevention and control of sheeppox
Notifiable disease!
Ring vaccine, destruction of affected flocks and quarantine of infected premises should be instituted
Type A (ATI) inclusion bodies are induced by what diseases
Cowpox
Ectromelia virus
Goat pox virus
Reportable
Clinically similar to sheeppox
Young kids suffer systemic disease with lesions on skin, respiratory and alimentary mucosae
Milder form of disease seen in adults
Hosts of Cowpox
Cattle, Wild and Domestic Cats, Humans and Zoo Animals
Prevention of pseudocowpox
Disinfection, iodophor teat dip
Isolation and treatment of infected cows
Reduce teat trauma, as injuries to skin of teat predisposes to infection
Benign form of sheepox
More common in adults and resistant breeds
Only skin lesions occur
No or very mild systemic reaction
Type B (Guarnieri) Inclusion Bodies
Slightly basophilic and composed of viral particles and protein aggregates
Describe the structure of poxvirus virions
Outer layer encloes a dumbbell shaped core and two lateral bodies
Chronic lesions of pseudocowpox
Commenses as erythema
Yellow-grey, soft scurfy scabs which are rubbed off during milking
Skin is corrugated
No pain
Lesions may persist for months
Examples of diseases caused by genus Orthopoxvirus
Cowpox
Monkeypox
Varioloa
Monkeypox
Genus Orthopoxvirus
Viral zoonosis with symptoms in humans similar to those seen in the past smallpox patients
Distribution of contagious ecthyma
worldwide
Clinical signs of swinepox
Erythematous macule → Papule → Vesicle → Pustule → Ulcer → Scab
Transient fever
Exudative epidermitis (Greasy pig disease) and secondary bacterial dermatits
Pathogenesis of psudocowpox
Lesions are characterized by hyperplasia of squamous epithelium
Two forms of sheeppox virus
Malignant form
Benign form
Routes of transmission of fowlpox virus
Transmitted within a flock through minor wounds and abrasions in mouth, comb, wattles, or skin as result of fighting, pecking and other injuries
Mechanically transmitted by mosquitos, lice and ticks
Possible aersol route
Malignant form of sheeppox
Lambs and susceptible nonnative breeds
Marked depression and prostration
High fever, salivation, lacrimation
Edema of eylids
Serous nasal discharge that becomes mucopurulent
Days after infection pox lesions develop in respiratory, digestive and urinary tracts
Pseudocowpox disease in humans
Milkers Nodule
Cause mild skin lesion
Lesions on hands - dairy farmers and vets treating infected cows
Lesions vary from multiple vesicles to a single indurated nodule
Enveloped/Non-Enveloped virions are taken up by cells more readily and appear to be more important in the spread of virions through the body of the animal
Enveloped
Transmission of Sheep Pox
Highly contagious
Enters respiratory tract and transmission is commonly by aerosol route
Can also occur through MM or abraded skin
Virus present in nasal and oral secretions for several weeks after infection
Virus survive months in dry scabs
Mechanical transmission by biting arthropods
T/F: Sheep Pox and Goat Pox are strains of the same virus
False
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Genetic sequencing has now demonstrated them to be separate viruses
Primary transmission of monkeypox in humans
Results from direct contact with blood, bodily fluids or rashes of infected animals
Deadliest form of fowlpox disease
Diphtheric form - wet form
Clinical signs of contagious ecthyma
Mucocutaneous junction - swelling lips
Animal may find it difficult to take food
Lesions in genitals, coronets and ears
Scab drops off (1-4 wks) tissue heals without scarring
Economic importance of Cowpox
Losses to farmers due to inconvenience in milking because of soreness of teats and mastitis resulting from secondary bacterial infections
Clinical signs of cowpox in humans
Macropapular lesions first observed on hands and face
Develop into vesicular and then ulcerative lesions
Enlarged painful local lymph nodes
Fever, vomiting and sore throat
Extracellular Mature Viruses (EMV) are released from cells by
budding
Transmission of lumpy skin disease
Arthropod vector - most common
Direct contact
Epidemiology of pseduocowpox
Reported from most countries
Lip and leg ulcerative form of ulcerative dermatosis of sheep
Formation of ulcers around the mouth and nose or on the legs
Face lesions occur on the upper lip, between the border of the lip and nasla orifice, on the chin and on the nose
Foot lesions are seen anywhere between teh coroent and the carpus or tarsus
Cutaneous form of fowlpox
Small papules on comb, wattles and around beak
Lesions occassionally develop on legs, feet and around cloaca
Nodules become yellowish and progress to thick scab
Sharp fall in egg production
Reservoir host of Cowpox
Rodents
Vaccination for sheeppox
Commercial and subunit vaccine available
Killed vaccine elicit temporary protection
Live attenuated vaccines offer excellent protection
Swine pox is transmitted mechanically by
Haematopinus suis - pig louse
Transmission of Cowpox in cattle
From cow to cow in a herd is through infected milkers hands or teat cups
Monkeypox infection in monkeys
Disease characterized by generalized skin erruptions, developing to papules on the trunk, face, palms and soles
Diseases caused by genus capripoxvirus
Sheep pox
Goat pox
Lumpy Skin disease
Clinical forms of ulcerative dermatosis of sheep
Lip and leg ulceration
Venereal
Orthopoxviruses are what shape
Brick shaped
T/F - Poxvirus can survive in dried scabs for many months or years
True
Transmission of swinepox
Direct contact associated with skin injury - virus can survive in scab for years
Mechanical transmission by pig louse, flies and insects
Transplacental infection of neonatal pigs
Clinical signs of pseudocowpox
Infection generally mild
Multiple lesions per teat
Acute lesions vs chronic lesions
Control of lumpy skin disease
Live attenuated vaccine available
Slaughter of affected and in-contact animals
Distribution of Sheeppox and Goatpox
Endemic in Africa, Asia and parts of Europe
Characteristics of fowlpox virus
Extremely resistant to desiccation
Can survive in exfoliated scabs for long periods
Etiology of Ulcerative Dermatosis of Sheep
Infectious disease of sheep caused by a virus antigenially similar to the ectheyma virus
Hosts of lumpy skin disease
Cattle - all ages and types susceptible
Bollinger bodies
Eosinophillic granular intracytoplasmic granules inclusion bodies
Distirbution of Cowpox
Endemic only in Europe and Asia
Are enveloped or non-enveloped virions of poxvirus infectious?
Both
Poxviruses replicate primarily in the
Cytoplasm
Diagnosis of poxviruses
Clinical signs
Sampling material
Electron microscopy
Histopathology
Inoculation in embryonated egg
Serological assay
Detection of pox nucleic acid by PCR
Secondary lesions of cowpox in cats
7-10 days after primary lesion appears
Develop into discrete, circular, ulcerated papules
Ulcers become covered by scabs
Vaccination for contagious ecthyma
Suspension of scabs in glycerol saline and is painted onto a small area of scarified skin inside the thigh
Does not offer long-lasting immunity
Treatment of pseudocowpox
Removal of scabs
Burn the scabs to prevent environmental contamination
Application of an emollient ointment before milking
Application of astrigent preparation after milking
Control of swinepox
Eradication of lice from piggery
No vaccine
First virus to be grown in embryonated egg
Fowlpox virus
Acute lesions of pseudocowpox
Erythema → Papules → Vesicle/Pustule → Rupture → Thick Scab
Scab elevated due to accumulation of granulation tissue
Scab drops (7-10 days) leaving horseshoe shaped ring of small scabs
Type A (ATI) Inclusion Bodies
Cowpox and Ectromelia virus
Strongly eosinophilic
Antigenic characteristics of poxviruses
Group specific nucleoprotein (NP)
Most common form of fowlpox disease
Cutaneous form - dry form
Hosts of Contagious Ecthyma
Sheep and goats
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Primarily in lambs and kids
T/F: Parapoxviruses do not multiply in chicken embryo
True
Properties of Poxviruses
Large, sometimes enveloped, DNA viruses
Complex structure - pleomorphic, brick shaped
Irregular surface of projecting tubular/globular structures
Hosts of swinepox
Pigs
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Benign with low mortality and low morbidity in older pigs
Transmission of pseudocowpox
Source of infection is infected cattle
Contaminated milkers hands and teat cups
Biting insects can transmit
Calves infected when suckling
Semen of bull
Pathogenesis of Sheeppox
Systemic disease
Incubation period is followed by leukocyte associated viremia
Virus localizes in skin and other internal organs
Immune complexes results in severe necrotizing vasculitis develop in arterioles and postcapillary venules of the skin
Borrel Bodies
Occur inside bollinger bodies, minute spherical bodies obtained by tryptic digestion of bollinger bodies
Chicken pox is caused by what virus
Human Herpesvirus 3 - Varicella zoster virus
Transmission of cowpox in cats
Skin inoculation, probably through a bite or skin wound
Bollinger bodies andn borrel bodies are seen in what pox virus
Fowlpox
Enveloped poxvirus show a (high/low) environmental stability.
High
Diseases caused by genus Suipoxvirus
Swinepox
Diseases caused by genus parapoxviruses
Pseudocowpox
Contagious Ecthyma / Orf
Bovine Papular Stomatitis Virus
Diphtheric form of fowlpox
Caused by droplet infection
Involves infection of mucous membranes of mouth, pharynx, larynx, and sometimes trachea
Lesions result in a necrotic pseudomembrane which may cause death by asphyxiation
Prognosis is poor
Pseudocowpox
Genus parapoxvirus
VIral skin infection that causes mild sores on the teats and udders of cattle
Commonly referred to as milkers nodule in humans
Bollinger and Borrel bodies are seen in what type of pox virus infection
Avipoxvirus
Secondary transmission of monkeypox in humans
Human to human contact, resulting from close contact with infected respiratory tract excretions, with skin lesions of an infected person or with recently contaminated objects
Lumpy skin disease distribution
Enzootic in sub-saharan Africa and Middle East with recent incursion in Iraq
Diseases of genus Avipoxvirus
Fowlpox
Turkeypox
Canarypox
Avipox
Clinical signs of monkeypox in humans
Invasion period - fever, intense headache, lymphadenopathy, muscle pain
Skin erruption period - rash from amculopapules to vesicles, pustules followed by crusts
Transmission of cowpox in humans
Caused by direct contact to cats
Host of fowlpox
Highly infectious disease of poultry and turkeys
Control of fowlpox
Vaccination
Control mosquito population and other biting insects
Distribution of fowlpox
Worldwide
Why do enveloped poxviruses show high environmental stability?
Due to their low lipid content, they are less sensitive to organic solvents/disinfectants compared to other enveloped viruses
Histopathological characteristics of poxviruses
Type B (Guarnieri) Inclusion Bodies
Type A (ATI) Inclusion Bodes
Three forms of fowlpox disease
Cutaneous Form - Dry Form
Diphtheric Form - Wet Form
Ocular Form
Form of pox virus that contains two membranes
Extracellular Mature Virus (EMV)
Ocular form of fowlpox
Conjunctivitis
Cheesey exudate accumulates under the eyelids
Hemagglutinin is produced by what poxvirus
Orthopoxvirus
Eitiology of Fowlpox
Genus Avipoxvirus
Diagnosis of pseudocowpox
Horseshoe shaped ring like lesion are pathognomic
Isolation and detection of the virus by various diagnostic laboratory methods from vesicular fluid or from teat skin
Clinical findings of cowpox in cattle
Incubation period of 3-7 days
Mildly febrile
Papules on teats and udder
Sucking calves may develop lesions in mouth
Vesicles may be evident or may rupture
