Flashcards in Exam 2 - Family: Poxviridae Deck (86):
Chordopoxvirinae (poxviruses of vertebrates) and Entomopoxvirinae (poxviruses of insects)
8 Genera in the subfamily Chordopoxvirinae
1. Genus: Orthopoxvirus
2. Genus: Parapoxvirus
3. Genus: Avipoxvirus
4. Genus: Capripoxvirus
5. Genus: Leporipoxvirus
6. Genus: Suipoxvirus
7. Genus: Molluscipoxvirus (Myxoma virus)
8. Genus: Yatapoxvirus (Yaba Monkey Tumor Virus)
Properties of Poxviruses
- Large, sometimes enveloped doubled stranded DNA viruses.
- Pleomorphic, brick shaped Possess an irregular surface of projecting tubular or globular structures
- Do not conform to icosahedral or helical symmetry.
Genus: Parapoxvirus properties
Ovoid, covered with long thread-like surface tubules, arranged in crisscross fashion, resembling a ball of yarn.
Two distinct infectious poxvirus particles exists
Intracellular Mature Virus (IMV) and Extracellular Enveloped Virus (EEV)
Extracellular Enveloped Virus (EEV)
Contains two membranes: envelope and inner membrane. Are released by budding that contain virus encoded proteins from host cells membrane.
Intracellular Mature Virus (IMV)
Only have an inner membrane. Come out by disruption of host cell and have only inner membrane.
Occurs in cytoplasm. Unlike other DNA viruses, poxviruses have evolved to encode the enzymes required for transcription and replication of the viral genome.
Poxvirus Antigenic Characteristics
Group-specific Nucleoprotein (NP), genetic recombination among the viruses
Unlike other enveloped viruses, there is high environmental stability and remain infectious. Less sensitive to organic solvents/disinfectants due to low lipid content. High resistance of drying. Can survive for many months and years in dried scabs.
Poxvirus Transmission - Skin
Only with broken or lacerated skin.
Poxvirus Transmission - Respiratory route
Aerosol route, typically most common route
Poxvirus Transmission - mechanical
Biting of arthropods
Poxvirus Pathogenesis and Immunity
Are highly epitheliotropic. Can cause systemic diseases, and are host specific.
Spread of Poxvirus
Gains access to the systemic circulation via the lymphatic system. Secondary viremia disseminates the virus back to the skin.
Chronological pathway of skin lesions poxvirus
Macule, Papule, Vesicle, Pustule, Ulcer, Scab
Cowpox in cattle, cats and humans; Monkeypox
Endemic only in Europe and Asia.
(definition of endemic: regularly found among particular people or in a certain area)
Cowpox in Cattle - Transmission
From cow to cow, infected milker's hands or contaminated teat cups
Cowpox in Cattle - Incubation Period
Cowpox in Cattle - Clinical Findings
Papular lesions appear on the teats and udder or in mouths of suckling calves.
Cowpox in Cats - Transmission
Typically through bite or skin wound. Most commonly from rodents. Can be oro-nasal route.
Cowpox in Cats - Clinical signs (Primary Lesions)
Single primary lesion usually on head, neck or forelimb
Cowpox in Cats - Clinical signs (Secondary Lesions)
7-10 days after primary lesion, develop into discrete, circular, ulcerated papules. May develop mild coryza or conjunctivitis.
Cowpox in Humans - Transmission
Direct contact with cats, rarely from cattle.
Cowpox in Humans - Clinical signs
Macropapular lesions on hands and face. Enlarged painful local lymph nodes, some may report fever, vomiting, and sore throat.
Monkeypox in Humans - Symptoms
Similar to smallpox
Monkeypox in Humans - Transmission (primary)
Results from direct contact with blood, bodily fluids, or rashes of infected animals.
Monkeypox in Humans - Transmission (secondary)
Results from close contact with infected respiratory tract excretions, with the skin lesions of an infected person or with recently contaminated objects.
Monkeypox - Distribution
Villages in Central and West Africa
Monkeypox - invasion period
(0-5 days) Fever, intense headache, lymphadenopathy, muscle pain
Monkeypox - Skin eruption period
Evolution of the rash from maculo-papules to vesicles, pustules, followed by crusts.
Monkeypox in Monkeys
The disease in characterized by generalized skin eruptions, developing to papules on the trunk, face palms and soles.
2. Contagious Ecthyma/Orf Virus
Pseudocowpox is a viral skin disease that causes mild sores on the teats and udders of cattle. This virus can also infect humans and the condition is commonly referred to as milker's nodule.
Infected cattle, contaminated milker's hands and teat cups, biting insects, suckling calves, semen of bulls
Pseudocowpox Acute Lesions
Thick scab that is elevated due to accumulation of granulation tissue. After 7-10 days, the scab drops off, leaving a Horseshoe-shaped ring of small scabs surrounding a small wart-like granuloma.
Pseudocowpox Chronic Lesions
Yellow-gray, soft scurfy scabs which are rubbed off during milking. Skin is corrugated, no pain, lesions may persists for months.
Horseshoe-shaped ring like lesion (pathognomonic for the disease). Isolation and detection of the virus by various diagnostic laboratory methods from vesicular fluid or from teat skin.
Removal of scabs, burn the scabs to prevent environmental contamination, application of an emollient ointment before milking. Application of astrigent preparation after milking.
Disinfection, use iodophor teat dip. Isolation and treatment of infected cows. Reduce teat trauma, as injuries to skin of teat predisposes to infection.
Pseudocowpox in Humans (The Milker's Nodule)
Causes a milk skin lesion known as Milker's Nodule. Lesions on the hands of dairy farmers milking teats or vets treating infected cows. Lesions may vary from multiple vesicles to a single, indurated nodule.
Contagious Ecthyma - Synonyms
ORF, Scabby Mouth, Contagious Pustular Dermatitis, Sore Mouth
Contagious Ecthyma - Host
Sheep and goats, primarily in lambs and goats kids
Contagious Ecthyma - Transmission
Contaminated instruments, virus infects healthy animals primarily through damaged skin, oral lesions in lambs or kids result from nursing dams with teat lesions, and vice-versa.
Contagious Ecthyma - Pathogenesis
The skin reaction to viral infection consists of a cellular response with necrosis and sloughing of the affected epidermis and underlying stratum papillare of the dermis. The cutaneous response to infection includes a delayed-type hypersensitivity reaction and an influx of inflammatory cells.
Contagious Ecthyma - Clinical signs
First: lesion develops in mucocutaneous junction and swelling of the lips.
Next: Lesions spread to the muzzle and nostrils and buccal mucosa
Secondary signs: anorexia and weight loss, bacterial infections cause mastitis, lameness, infertility.
Underlying tissue heals without scarring.
Contagious Ecthyma - Vaccination
- Does not offer long-lasting immunity.
- NO circumstances should the vaccine be used on farms that DO NOT have a problem with ORF.
- Inspect the lamb 1 week after vaccination.
- Lambs/kids may need to be vaccinated at 6-8 weeks to help prevent the disease
- Vaccinate pregnant ewes only 7-8 weeks before lambing.
This includes sheep pox, goat pox, and lumpy skin disease of cattle.
Sheep and Goat Pox - Distribution
Endemic in Africa, Asia and parts of Europe.
SPV and GPV cannot be distinguished from each other with serological technique, including viral neutralization.
SPV and GPV - Transmission
Highly contagious. Enter respiratory tracts and is commonly by aerosol route. Spread through mucous membrane and abraded skin. Especially from contaminated iatrogenic materials. Mechanical transmission by biting arthropods
SPV and GPV - Pathogenesis
A systemic disease. Leukocyte associated viremia. Localized in skin and other internal organs. Results in ischemic necrosis of dermis and overlying epidermis.
SPV - Clinical signs - Malignant Form - Initial Signs
- Seen in lambs and Merino breeds.
- Incubation period: 4-8 days
- Marked depression and prostration
- High fever, salivation, lacrimation
- Edema of the eyelids
- Serous nasal discharge that becomes mucopurulent
SPV - Clinical signs - Malignant form - Later signs
- 1-2 days after, pox lesions develop on skin and buccal, respiratory, digestive, and urinary tract mucosa
- Extend to pharynx, larynx, vagina, abomasum and spleen.
- Cutaneous nodules are distributed widely over the body.
- Lesions heal leaving a STAR SHAPED SCAR , free of hair or wool
SPV - Clinical signs - Benign form
- More common in adults and resistant breeds
- Only skin lesions occur
- Mild systemic reactions
SPV - Prevention and control
- Ring vaccination, destruction of affected flocks and quarantine of infected premises should be instituted.
SPV - Vaccination
- Large variety of commercial vaccines are now available, including a subunit vaccine
- Killed vaccine elicit, at best, temporary protection
- Live attenuated vaccines offer excellent protection > 1 year
GPV - Properties
-Young kids suffer systemic disease with lesions on skin, respiratory and alimentary mucosa
- A flat hemorrhagic form of capripox is seen in some European goats and this has a high case fatality.
Lumpy Skin Disease - Distribution
Enzootic in sub-saharan Africa and Middle east with recent incursion in Iraq
(def. of enzootic: of, relating to, or denoting a disease that regularly affects animals in a particular district or at a particular season.)
Lumpy Skin Disease - Transmission
Arthropod vector (most common) and direct contact.
Lumpy Skin Disease - Host
Lumpy Skin Disease - Clinical findings
Fever, multiple nodular lesions on skin and mucous membrane, lymphadenopathy. Morbidity reaches 80% during epizootics.
Lumpy Skin Disease - Control
Live attenuated vaccines available. Slaughter of affected and in-contact animals.
Swinepox Virus - Transmission
Direct contact with skin injury. Mechanical transmission by Haematopinus suis (pig louse). Evidence of transplacental infection.
Swinepox Virus - Clinical signs
- Transient fever
- Skin lesions in abdomen and inner thigh
- Exudative epidermitis (greasy pig)
Swinepox Virus - Control
Eradication of lice from piggery. No commercially available vaccine.
This includes: fowlpox and other avian poxviruses.
DO NOT CONFUSE WITH CHICKEN POX.
Fowlpox - Transmission
Extremely resistant to desiccation and can survive in exfoliated scabs for a long period.
Can be transmitted by minor wounds and abrasions. Mechanical vectors and possibly aerosol routes.
Fowlpox - Clinical Signs - The Cutaneous Form
The dry form. Most common form. Low mortality.
-Results from mechanical vectors or lacerated skin.
-Small papules on comb, wattles, neck, legs, feet and around cloaca
- Nodules become yellowish and progress to a thick scab
- Recover in about 4 weeks
Fowlpox - Clinical Signs - The Diphtheritic form
The wet form.
- Caused by droplet infection.
- Infection of mouth, pharynx, larynx and trachea mucosa
- Lesions coalesce and result in pseudomembrane that causes asphyxiation
- Prognosis is poor
- High morbidity
Fowlpox - Clinical Signs - Ocular form
Conjunctivitis, cheesy exudate accumulates under the eyelids
Eosinophilic granular intracytoplasmic inclusion bodies
Occur inside bollinger bodies. Borrel bodies are minute spherical bodies obtained by tryptic digestion of bollinger bodies
Fowlpox - Control (vaccination)
MLV of fowlpox or pigeonpox virus of chicken embryo of avian cell culture origin are available commercially. Vaccines indicated in areas where the disease is endemic. In enzootic areas, vaccinated during the first week of life and then again 8-12 weeks later.
Control mosquito population and other biting insects.
Ulcerative Dermatosis of Sheep
Ulcerative Dermatosis of Sheep - Transmission
Virus infection through damaged skin or by coitus
Ulcerative Dermatosis of Sheep - Clinical forms
Regardless of location, lesions are usually ulcers with a raw crater that bleeds easily. Manifest in two forms:
1. Lip and leg ulceration
2. Venereal form
Lip and leg ulceration
-Formation of ulcers around the mouth and nose or on the legs (lips and leg ulceration)
- Face lesions occur on the upper lip, between the border of the lip and the nasal orifice, on the chin, and on the nose
- Foot lesions are seen anywhere between the coronet and the carpus or tarsus
- Venereally transmitted ulceration of the prepuce and penis or vulva
- Rarely, ulcers may extend to the glans penis so that the ram becomes unfit for natural breeding
- In ewes, edema, ulceration and scabbing of the vulva have less serious consequences
Superficial necrosis of the skin of the mucosa of the prepuce and glans penis
Diagnosis of Poxviruses
- Clinical signs
- Sampling material (scrapings from skin lesions, vesicular fluid, crusts, scabs
- Electron Microscope (characteristic morphology and size of poxviruses. Orthopoxviruses are brick shaped. Parapoxviruses are ovoid)
- Histopathology: presence of characteristic intracytoplasmic inclusion bodies.
-Chorioallantoic membrane (CAM)
- PCR, ELISA, Pock Assay, etc.
Type B inclusion bodies
Guarnieri inclusion bodies. Most poxviruses induce presence of type B inclusion bodies. These are slighly basophilic and composed of viral particles and protein aggregates.