Poxviridae (Ex2) Flashcards
General properties of Poxviridae
morphology, two types, DNA, location of replication, stability
- large, pleomorphic, sometimes enveloped, DNA virus with complex structure
- irregular surface of projecting tubular or globular structures
- extracellular enveloped virus (inner membrane and envelope), and intracellular mature virus (only inner membrane)
- single molecule of linear double stranded DNA
- replication occurs in the cytoplasm
- high resistance in environment and scabs
How are poxviruses transmitted?
- through broken or lacerated skin
- inhalation of aerosol
- mechanically by biting arthropods
Describe the spread of poxviruses in the body
- after entry, the virus gains access to systemic circulation via the lymphatics
- a secondary viremia disseminates the virus back to the skin and other target organs
Describe the skin lesions caused by poxviruses
including order of lesion development
- degenerative changes in epithelium
- rupture of pustules can predispose to secondary bacterial infections
- macule > papule > vesicle > pustule > ulcer or scab > scar and healing
Hosts and reservoir of Cowpox
Hosts: cattle, cats, humans, zoo animals
Reservoir: rodents
What is the genus of Poxviridae that causes Cowpox?
Orthopoxvirus
Transmission of Cowpox
cattle and cats
Cattle: cow to cow in a herd from infected milkers hands or teat cups - infected farm cats - rodent reservoirs Cats: skin inoculation - rodents - oro-nasal route
Clinical signs of Cowpox in Cattle
- mildly febrile
- papules appear on teats and udder
- suckling calves develop lesions in mouth
- vesicles may rupture, leaving raw, ulcerated areas that form scabs
Clinical signs of Cowpox in Cats
Primary lesions: lesions on head, neck, or forelimb
- small, scabbed wound to large abscess
Secondary: widespread, develop into discrete, circular, ulcerated papules
- ulcers become covered by scabs
Clinical signs of Cowpox in Humans
- macropapular lesions on hands and face
- enlarged, painful local lymph nodes
- fever, vomiting, sore throat
What is Monkeypox?
What genus of Poxviridae?
- in monkeys, a disease characterized by generalized skin eruptions, developing to papules on the trunk, face, palms, and sole
- Orthopoxvirus
What is Pseudocowpox?
What genus of Poxviridae?
- a viral skin disease that causes mild sores on teats and udders of cows
- referred to as Milker’s Nodule
- Parapoxvirus
Transmission of Pseudocowpox
- source is the infected cattle
- contaminated milker’s hands, teat cups
- biting insects
- suckling calves are infected
- semen of bulls
Describe acute lesions of Pseudocowpox
- erythema > papules > vesicle or pustule > rupture > thick scab
- scab becomes elevated due to accumulation of granulation tissue
- scab drops off after 7-10 days, leaving horse-shoe shaped ring of small scabs surrounding a small wart-like granuloma
Describe chronic lesions of Pseudocowpox
- commences as erythema
- yellow-gray, soft scabs rubbed off during milking
- skin is corrugated
- no pain
- may persist for months
Treatment of Pseudocowpox
- remove scabs and burn to prevent environmental contamination
- application of emollient ointment before milking
- application of astringent preparation after milking
Pseudocowpox in Humans
- Milker’s Nodule
- mild skin lesions on hands
What are the hosts of Contagious Ecthyma (ORF)?
What is the genus and family?
- sheep and goats, mainly lambs and kids
- Poxviridae, parapoxvirus
Transmission of ORF
- scabs that fall off from healing lesions contain the virus
- remains stable in environment
- contaminated instruments
- rapid spread in flock
- infection through damaged skin
- oral lesions in suckling kids and lambs from infected teats of mother and vice versa
Clinical signs of ORF
- first lesions in mucocutaneous junction, accompanied by swelling of lips
- lesions spread to muzzle and nostrils
- anorexia and weight loss
- lesions on teats, secondary bacterial leading to mastitis
- severe cases show lesions in feet, genitals, and ears (infertility, lameness)
- scab falls off in 1-4 weeks, no scar
Evolution of lesions in ORF
macule > papule > vesicle > pustule > ulcer > scab formation
Vaccination for ORF
- vaccine prepared from suspension of scabs in glycerol saline, and painted on small area of scarified skin
- should not be used on farms with no ORF
- inspect lamb 1 week after vaccination
- do not offer long-lasting immunity
- vaccinate pregnant ewes
ORF in humans
- macro-papular lesions and large nodular lesions on fingers, hand, arm, face
- healing without scar
- secondary bacterial infections possible
What is the genus of Sheeppox and Goatpox
Capripoxvirus
Tranmission of Sheeppox and Goatpox
- highly contagious
- enters respiratory tract via aerosol
- also spread through mucus membrane or abraded skin via direct contact
- virus present in nasal and oral secretions for weeks
- can survive in dry scabs for months
- mechanical via biting arthropods
Pathogenesis of Sheeppox
- incubation period is followed by a leukocyte-associated viremia
- virus localizes in the skin and other organs
- deposition of immune complexes results in severe necrotizing vasculitis in arterioles and postcapillary venules of the skin
- results in ischemic necrosis of dermis and epidermis
Sheeppox Clinical Signs
Malignant form: lambs and susceptible breeds
- marked depression and prostration, high fever, salivation, lacrimation, edema of eyelids, serous nasal discharge
- pox lesions on mucosa, extend to other tissues
- secondary pneumonia common
- cutaneous nodules, heal leaving star shaped scar
Benign: adults and resistant breeds
- only skin lesions occur
Goatpox
- reportable
- in Africa, Asia, Europe
- young kids get systemic disease with lesions on skin, respiratory, and alimentary mucosa
- milder form in adults
Lumpy Skin disease
genus/family, transmission, host, signs, control
- Poxviridae, capripoxvirus
- Arthropod vector, direct contact
- fever, nodular lesions on skin and mucous membranes, lymphadenopathy
- live attenuated vaccines
- slaughter affected and in contact animals
Transmission of Swinepox
- direct contact with skin injury
- mechanical by pig louse, flies, and insects
- transplacental infection
Clinical signs of Swinepox
- transient fever
- typical pox lesions, mostly on abdomen and inner thighs
- exudative epidermatitis and secondary bacterial dermatitis occur often
- lesions may appear in upper respiratory tract and digestive tract
Transmission of Fowlpox
- resistant to desiccation
- can survive in scabs
- transmitted through minor wounds
- mechanically by arthropods
- possibly by aerosol
What are the forms of Fowlpox?
- Cutaneous form (dry)
- Diphtheritic form (wet)
- Ocular form
Clinical signs of Dry form of Fowlpox
- low mortality
- small papules on comb, wattles, and around beak
- lesions can develop on legs, feet, and around cloaca
- nodules become yellowish and progress to thick scab
- sharp fall in egg production
Clinical signs of Wet form of Fowlpox
- infection of mucus membranes of mouth, pharynx, larynx, and trachea
- lesions result in pseudomembrane, which can lead to asphyxiation
- poor prognosis
Clinical signs of Ocular form of Fowlpox
- conjunctivitis
- cheesy exudate accumulates under the eue
What are Bollinger Bodies?
eosinophilic granular intracytoplasmic inclusion bodies
What are Borrel Bodies?
minute spherical bodies obtained by tryptic digestion of Bollinger bodies
- occur inside Bollinger bodies
Ulcerative Dermatosis of Sheep
transmission, signs
- transmitted through damaged skin or coitus
- lesions are ulcers with a raw crater that bleeds easily
- two clinical forms: lip and leg ulceration, and venereal form
What are Type-B or Guarnieri inclusion bodies?
- most poxviruses induce the presence of these
- slightly basophilic and composed of viral particles and protein aggregates
What are Type-A or ATI inclusion bodies?
- some poxviruses induce these
- strongly eosinophilic
What is the shape of orthopoxviruses and parapoxviruses?
Ortho: brick shaped
Para: ovoid shaped
