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Poxiviridae Flashcards

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1
Q

Family Poxiviridae

A

Subfamily: Chordopoxvirinae (poxvirus of vertebrates)
8 genera
Disease in humans, animals, birds

  1. genus: Orthopoxviurs
  2. genus: Parapoxvirus
  3. genus: Avipoxvirus
  4. genus: Capripoxvirus
  5. genus: Leporipoxvirus
  6. genus: suipoxvirus
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2
Q

Properties of poxviruses

A

Large, sometimes enveloped, DNA viruses with complex structure (symmetry)
Most are pleomorphic, typically brick-shaped
Possess irregular surface of projecting tubular or globular structures
Genus parapoxvirus= ovoid, covered with long thread-like surface tubules- criss cross fashion like ball of yarn

Two distinct infectious particles: intracellular mature; extracellular enveloped
Extracellular= 2 membranes: envelope, and inner membrane
Virions are released from cells by budding rather than by cellular disruption, acquire extra envelope that contains virus encoded-proteins from host membrane
IMV- only inner membrane. Out by disruption of host cell

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3
Q

Properties of poxviruses- cont

A

Do not conform to icosahedral or helical symmetry- have complex symmetry
Virion outer layer encloses a dumbbell-shaped core and two lateral bodies
Core contains viral DNA together with several proteins
Have more than 200 genes in genome. 100 encode proteins that are contained in virions

genome= single molecule of linear double-stranded DNA
Many proteins encoded by this genome are enzymes involved in nucleic acid synthesis and virion structural components
Also encode proteins that specifically counteract host adaptive and innate immune response

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4
Q

Properties of poxviruses- contt

A

Replication occurs predominantly in cytoplasm
Possible bc unlike other DNA viruses, poxviruses have evolved to encode the enzymes required for transcription and replication of viral genome
Following replication, virions are released by budding, exocytosis, or cell lysis
Most are not enveloped and released by lysis
enveloped are taken up by cells more readily and appear to be more important in the spread of virions through body of animal

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5
Q

Properties of poxviruses- stability

A

The virion of poxvirus is an enveloped particle that differs significantly from other enveloped viruses
Unlike other enveloped viruses, poxviruses show a high environmental stability and remain infectious over a period of several months in an ambient environment
Due to their low lipid content, they are less sensitive to organic solvents/disinfectant compared to other enveloped viruses
Poxvirus show an extraordinary high resistance to drying
Can survive for many years in dried scabs or other virus laden material

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6
Q

Properties of poxviruses- transmission

A

Several routes:
Skin: cannot infect intact skin. must be broken or lacerated. Common
respiratory: by aerosol route. Inhalation= infection
mechanically: by biting arthropods

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7
Q

Pathogenesis and Immunity

A

Poxviruses are highly epitheliotropic, causing cutaneous (skin) lesions
Occasionally, poxviruses causes systemic diseases in birds and wild animals
Many are host specific
However, orthopoxviruses infect a wide range of species

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8
Q

Spread of poxvirus

A

Following introduction into the body, the poxvirus usually gains access to the systemic circulation via the lymphatic system
A secondary viremia disseminated the virus back to the skin and to other target organs

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9
Q

Skin lesions in poxvirus infection

A

There are degenerative changes in the epithelium
Rupture of pustule can predispose to secondary bacterial infection
Ulceration may develop
Poxvirus can survive in dried scabs for many months or years
Order: macule, papule, vesicle, pustule, scab, scar (or ulcer complication)

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10
Q

Macule

A

Flat, red.

Local inflammation immune response infiltrating leukocytes

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11
Q

Papule

A

Raised, red
More marked inflammation
Invasion of neighboring tissues

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12
Q

Vesicle

A

Small blister

Microbe invades epithelium

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13
Q

Genus: Orthopoxvirus

A

Cowpox

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14
Q

Cowpox: distribution

A

Endemic only in europe and asia

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15
Q

Cowpox: Hosts

A

Cattle, wild and domestic cats, humans, zoo animals, etc

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16
Q

Cowpox: Reservoir hosts

A

Rodents

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17
Q

Cowpox: Transmission

A

From cow to cow in a herd is through infected milker’s hand or teat cups
Infected farm cats can also transmit the disease
Rodents serve as the reservoir and can transmit the disease

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18
Q

Cowpox: Economic importance

A

Losses to farmers due to inconvenience in milking because of soreness of teats and mastitis resulting from secondary bacterial infections

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19
Q

Cowpox: Clinical findings

A

During which cows may be mildly febrile, papules appear on the teats and udder. Sucking calves may develop lesions in mouth
Vesicles may not be evident or may rupture readily leaving raw, ulcerated areas that form scabs

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20
Q

Cowpox in cats: Transmission

A

Usual route of infection in cats in skin inoculation, probably through a bite or skin wound. Rodents are a common source of infection
Transmission by oro-nasal route is also possible
In exotic felids (cheetahs), viral pneumonia may be evident

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21
Q

Cowpox in cats: clinical signs- Primary lesions

A

Primary lesions:
Most affected cats have a history of a single primary skin lesion, usually on head, neck, or forelimb
Primary lesion can vary from a small, scabbed wound to a large abscess

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22
Q

Cowpox in cats: clinical signs- Secondary lesions

A

Secondary lesions:
After the primary lesion appears, widespread secondary ones begin to appear
Throughout 2-4 days, these develop into discrete, circular, ulcerated papules ~0.5-1 cm diameter
The ulcers soon become covered by scabs, and healing is usually complete by ~6wks
Many cats show no signs other than skin lesions, but ~20% may develop mild coryza or conjunctivitis
Complications can result from secondary bacterial infections

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23
Q

Cowpox in humans: transmission

A

Mainly caused by direct contact to cuddly cats
Rarely from rodents and zoo animals
Virus not commonly found in cattle so chances of getting it from cow is low

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24
Q

Cowpox in humans: clinical signs

A

Macropapular lesions first observed on hands and face. Later develop into vesicular and then ulcerative lesions
Enlarged painful local lymph nodes
Patients may report fever, vomiting, and sore throat

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25
Monkeypox (other orthopoxvirus): in humans
Viral zoonosis with symptoms in humans similar to those seen in smallpox patients
26
Monkeypox (other orthopoxvirus): in humans: transmission- primary infection
Results from direct contact with the blood, bodily fluids, or rashes of infected animals. In africa, human infections have been documented through the handling of infected monkeys, Gambian rats or squirrels
27
Monkeypox (other orthopoxvirus): in humans: transmission- Secondary transmission
Human-to-human Resulting from close contact with infected respiratory tract excretions, with the skin lesions of an infected person or with recently contaminated objects
28
Genus: Parapoxviruses
Pseudocowpox (cattle, humans) Contagious Ecthyma/Orf virus (sheep, goats, humans) Bovine Papular Stomitis Virus (cattle, humans)
29
Pseudocowpox: definition
Viral skin disease that causes mild sores on the teats and udders of cattle Can also infect humans and the condition is referred to as milker's nodule
30
Pseudocowpox: etiology
Member of the genus parapoxvirus
31
Pseudocowpox: Epidemiology
Reported from most countries
32
Pseudocowpox: transmission
Source of infection is the infected cattle Contaminated milkers hand, teat cups biting insects may transmit virus Calves get infected during sucking infected teats semen of bulls
33
Pseudocowpox: pathogenesis
Lesions are characterized by hyperplasia of squamous epithelium
34
Pseudocowpox: clinical signs
Infections generally mild
35
Pseudocowpox: acute lesions
Erythema ->papules -> vesicle or pustule -> rupture -> thick scab The thick scab is 0.5-25cm in diameter, becomes elevated due to accumulation of granulation tissue After 7-10 d, the scab drops off, leaving a horseshow shaped ring of small scabs surrounding a small wart-like granuloma
36
Pseudocowpox: chronic lesions
``` Commences as erythema Yellow-gray, soft scurfy scabs which are rubbed off during milking Skin is corrugated No pain Lesions may persist for months ```
37
Pseudocowpox: Diagnosis
Horseshoe-shaped ring like lesion are pathognomonic for the disease Isolation and detection of the virus by various diagnostic laboratory methods from vesicular fluid or from teat skin
38
Pseudocowpox: differential diagnosis
``` Cowpox virus Bovine herpesvirus ulcerative mammilitis Vesicular stomatitis Udder impetigo Teat chaps and frostbite Black spot ```
39
Pseudocowpox: treatment
Removal of scabs Burn the scabs to prevent environmental contamination Application of an emollient ointment before milking Application of astringent preparation after milking
40
Pseudocowpox: prevention
Disinfection. Use iodophor teat dip Isolation and tx of infected cows Reduce teat trauma, as injuries to skin of teat predisposes to infection
41
Pseudocowpox in humans
Milkers nodule Causes a milk skin lesion On hands of dairy farmers milking teats or vet treating infected cows May vary from multiple vesicles to a single, indurated nodule
42
Contagious ecthyma (ORF): etiology
Orf virus, Genus Parapoxvirus
43
Contagious ecthyma (ORF): Host
Sheep and goats. Primarily in lambs and kids
44
Contagious ecthyma (ORF): Distribution
Worldwide
45
Contagious ecthyma (ORF): Transmission
Scabs that fall off from the healing lesions contain virus Virus are stable in the environment- remains highly infectious for long periods under dry conditions Contaminated instruments, like docking instrument or ear tagging plier can transmit the virus Spread in flocks v rapid virus infects healthy animals primarily through damaged skin Oral lesions in lambs or kids results from nursing dams with teat lesions and vice versa
46
Contagious ecthyma (ORF): Pathogenesis
Damage of skin is essential to establish infection Skin reaction to viral infection consists of a cellular response with necrosis and sloughing of the affected epidermis and underlying stratum papillare of dermis Cutaneous response to infection includes a delayed-type hypersensitivity reaction and an influx of inflammatory cells Lesions evolve from macule -> papule -> vesicle -> pustule -> ulcers -> scab formation
47
Contagious ecthyma (ORF): Clinical signs
First lesions develop in the mucocutaneous junction and are accompanied by swelling of lips From there, lesions spread to muzzle and nostrils, surrounding hairy skin and buccal mucosa Animal may find it difficult to take food because of oral lesions: anorexia and weight loss Affected lambs or kids sucking ewes or goats may result in lesions on teats This may predisose to secondary bact infection, resulting in mastitis Severe cases may show lesions in genitals, coronets, and ears Lesions on feet= lameness Lesions on scrotum= infertility
48
Contagious ecthyma (ORF): CS (pt 2)
scabs can drop off and underlying tissues heal without scarring Complications can result from secondary bact infections or from invasion of lesions by fly larvae Malignant form of disease has also been observed in sheep
49
Contagious ecthyma (ORF): Vaccination
Prepared from suspension of scabs in glycerol saline and painted onto a small area of scarified skin inside thigh, where a localized lesion develops In no circumstances should the vaccine be used on farms that do not have a problem with orf You should inspect lamb 1 wk after vx for local rxn which indicated viability of vaccine Vx do not offer long-lasting immunity ~1-2 yrs In problem flocks lambs/kids need to be vx at 6-8 wks Vaccinate preg ewes before lambing
50
Contagious ecthyma (ORF): in humans
Macro-papular lesions and large nodular lesions in finger, hand, arm, face, and even penis secondary bact infections of lesions may cause complications
51
Genus: Capripoxvirus
Sheep pox Goat pox Lumpy skin disease (of cattle)
52
Sheeppox and Goatpox: etiology
Members of genus Capripoxvirus
53
Sheeppox and Goatpox: distribution
Endemic in Africa, Asia, and parts of europe
54
Sheeppox and Goatpox
SPV and GPV once believed to be strains of same virus, but genetic sequencing shows they are separate Most strains are host specific and cause severe clinical disease in either sheep or goats, while some strains have equal virulence in both spp SPV and GPV cannot be distinguished from each other with serological tests Closely related to lumpy skin disease virus in cattle but no evidence LSDV can cause disease in sheep and goats
55
Sheeppox and Goatpox: transmission
Highly contagious Virus enters respiratory tract and transmission is commonly aerosol route Spread can also occur through mucous membrane or abraded skin, esp by direct contact with contaminated iatrogenic materials Virus is present in nasal and oral secretions for several weeks after infection Can survive in dry scabs for months Evidence for mechanical transmission by biting arthropods Transmission by aerosol (resp route is considered important/common route of transmission)
56
Sheeppox: pathogenesis
A systemic disease incubation period is followed by a leukocyte-associated viremia The virus localized in the skin and other internal organs Deposition of immune-complexes results in severe necrotizing vasculitis develop in arterioles and postcapillary venules of the skin (type III hypersensitivity) Results in ischemic necrosis of dermis and overlying epidermis `
57
Sheeppox: Clinical signs
There are two forms of disease: | Malignant and Benign
58
Sheeppox: Malignant form
Seen in lambs and susceptible nonnative breeds Pox lesions develop on skin and on buccal, respiratory, digestive and urinary tract mucosae Pox lesions extend to pharynx, larynx, lungs, vagina, abomasum and spleen Secondary pneumonia common Abortion rare Cutaneous nodules are distributed widely over body Nodules, occasionally become vesicular, pustular and finally scab Lesions heal leaving star shaped scar, free of hair or wool High mortality and case fatality rate
59
Sheeppox: Benign form
More common in adults and resistant breeds Only skin lesions occur No, or a very mild systemic reaction
60
Sheeppox: Prevention and control
Notifiable disease in most countries
61
Sheeppox: Vaccination
A large variety of commercial vxs available, including subunit vaccine Killed vaccines elicit, at best, temporary protection Live attenuated vaccines offer excellent protects >1 yr
62
Goatpox
``` Occurs in Africa, Asia, and parts of Europe Reportable Clinically similar to sheeppox Young kids suffer systemic disease Milder form of disease seen in adults ```
63
Lumpy skin disease: etiology
Member of genus Capripoxvirus
64
Lumpy skin disease: Distrivution
Enzootic in sub-saharan africa and middle east with recent incursion in iraq
65
Lumpy skin disease: Transmission
``` Arthropod vector (most common) also direct contact ```
66
Lumpy skin disease: Host
Cattle, all ages and types
67
Lumpy skin disease: clinical findings
Fever, multiple nodular lesions on skin and mucous membrane, lumphadenopathy
68
Genus: Suipoxvirus
Swinepox
69
Swinepox: Etiology
Member of genus Suipoxvirus
70
Swinepox: Distribution
Worldwide | Widespread sporadic disease
71
Swinepox: Host
Pigs Generally benign with low mortality and low morbidity in older pigs High case fatality in congenitally infected and v young suckling piglets
72
Swinepox: Transmission
Direct contact with skin injury. Virus can survive in scab for years Mechanical transmission by pig louse, Haematopinus suis These lice can carry the virus for weeks or months Also mechanical transmission by flies and insects There is evidence of transplacental infection of neonatal pigs
73
Swinepox: Clinical signs
Typical pox lesions Skin lesions may occur anywhere but most obvious on skin of abdomen and inner aspects of thighs Exudative epidermitis (greasy pig disease) and secondary bact dermatitis occasionally occur as a sequel to swine pox In sever infections, esp in congenitally-aquired pox infections (piglets born w/ or develop lesions all over after birth) lesions may occur in upper resp and gi tracts
74
Swinepox: Control
Eradication of lice from piggery | No commercially available vx
75
Genus: Avipoxvirus
Fowlpox and other avian poxviruses
76
Fowlpox: etiology
Member of genus Avipoxvirus | First virus to be grown in embryonated eggs
77
Fowlpox: Host
Highly infectious disease of poultry and turkeys
78
Fowlpox: Distribution
Worldwide
79
Fowlpox: Transmission
Virus is: extremely resistant to desiccation; can survive in exfoliated scabs for a long time. Routes: Within flock through minor wounds and abrasions in mouth, comb, wattles, or skin as result of fighting, pecking or other injuries Mechanically by mosquitoes, lice, ticks Possibly aerosol route
80
Fowlpox: clinical signs
3 forms: Cutaneous (dry) Diphtheritic (wet) Ocular
81
Fowlpox: Cutaneous form
Most common Low mortality Probably results from injecting by biting arthropods or mechanical transmission to injured or lacerated skin Small papules on comb, wattles, and around beak Lesions occasionally develop on legs, feet and around cloaca Nodules become yellowish and progress to a thick scab Sharp fall in egg production In uncomplicated cases, affected birds recover in about 4 weeks
82
Fowlpox: Diphtheritic form
Probs causes by droplet infection Involved infection of mucous membranes of mouth, pharynx, larynx, and sometimes trachea Lesions, as they coaslesce, result in necrotic pseudomembrane, which may cause death by asphyxiation Prognosis poor
83
Fowlpox: Ocular form
Conjunctivitis | Cheesy exudate accumulates under eyelids
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Avipoxvirus: Bollinger bodies
Eosinophilic granular intracytoplasmic inclusion bodies
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Avipoxvirus: Borrel bodies
Occur inside bollinger bodies. | Minute spherical bodies obtained by tryptic digestion of bollinger bodies
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Fowlpox: Control- Vaccination
Modified live fowlpox or pigeon pox virus vxs of chicken embryo or avian cell culture origin are available commercially Recombinant fowlpox vectored vxns have been develeoped Control mosquito pop and other biting insects
87
Unclassified poxviruses
Ulcerative dermatosis of sheep
88
Ulcerative dermatosis of sheep: transmission
Virus infection through damages skin or by coitus
89
Ulcerative dermatosis of sheep: Clinical forms
Lesions usually ulcers with a raw crater that bleeds easily 2 forms: Lip and leg ulceration Venereal form
90
Ulcerative dermatosis of sheep: venereal form
Venereally transmitted ulceration of the prepuce and penis or vulva Ram can become unfit for natural breeding
91
Dx of poxviruses
CS Sampling material: scrapings from skin lesions, vesicular fluid, crusts, scabs Electron microscopy: characteristic morphology and size of poxviruses Orthopoxviruses are brick shaped Parapoxviruses are ovoid Inoculation of embryonated egg (parapoxviruses do not multiply in chicken embryo)- CAM Serological assay (ELISA) Detection of poxvirus nucleic acid by PCR
92
Dx of poxviruses: histopathology
Presence of characteristic intracytoplasmic inclusion bodies - type B or Guarnieri inclusion bodies: most poxviruses induce the presence of these. Slightly basophilic and composed of viral particles and protein aggregates - type A or ATI inclusion bodies: cowpox and ectromelia virus. Strongly eosinophilic - Bollinger and Borrel bodies in avipoxvirus infection

Virology (28 decks)

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