Poxviridae Flashcards
Describe the look of pox viruses VS parapoxvirus.
- Poxvirus
-lg, some enveloped, DNA virus, complex symmetry
-pleomorphic, brick shaped, irregular surface w tubular/globular structures projecting - Parapoxvirus
-ovoid w thread like surface tubules arranged in cross cross
Describe IMV & EEV of pox viruses.
- IMV
-intracellular mature virus
-infectious
-inner membrane only
-virions released by disruption of host cell - EEV
-extracellular enveloped virus
-infectious
-envelope + inner membrane
-virions released via budding
*IMP for spread of virions bc taken up by cells more readily
Describe pox virus structure.
-virion outer layer encloses dumbbell shaped core + 2 lateral bodies
-core = viral DNA + proteins
-200+ genes in genome & 100 encode proteins
>genome = single molecule of linear double stranded DNA
>proteins encoded are enzymes in nucleic acid syn & virion structural components + proteins that counteract host adaptive & innate IR
Describe replication in poxvirus.
-replication in cytoplasm
>encode enzymes required for transcription & replication of viral genome
-after replication virion released by:
>budding = enveloped virions
>exocytosis
>cell lysis = non enveloped virions (most)
Describe stability of poxvirus.
-high environmental stability & stay inf for months
-low lipid content = less sensitive to organic solvents/disinf compared to other enveloped virus
-high resistance to drying
>survive years in dried scabs or other virus laden material
Describe transmission of poxvirus.
transmitted between animals
1. Skin
-cant inf intact skin
2. Respiratory route
-inhale aerosol
3. Mechanically transmitted
-biting arthropods (myxoma virus & avipoxvirus)
Describe the pathogenesis & immunity of poxvirus.
-highly epitheliotropic = cause cutaneous skin lesion
-systemic disease in bird & wild animals
-host specific
>orthopoxvirus inf wide range of species
Describe the spread of poxvirus.
-systemic circ via lymphatic system
-secondary viremia disseminates the virus back to skin & other target organ
Describe the skin lesions in pox virus infection.
Ma
Pa
Ve
Pu
Sca sca
Describe orthopoxvirus.
‘Cowpox’
1. Distribution
-endemic in Europe & Asia
2. Host
-cattle, cats, humans, zoo animals, etc
3. Reservoir
-rodents
Describe cowpox in cattle.
- Transmission
-cow to cow via inf milker hand or teat cup
-inf farm cats can transmit disease - Economic imp
-loss of $ to farmer bc of milking = soreness of teats & mastitis from secondary bacterial inf - Clinical findings
-cows mildly febrile, papules on teats & udder -> sucking calves develop lesions in mouth
-vesicles not evident or may rupture readily, leaving raw, ulcerated areas that form scabs
Describe cow pox in cats.
- Transmission
-skin inoculation (bite or wound)
-rodents
-exotic cat = viral pneumonia - CS Primary lesion
-skin lesion on head, neck, forelimb
-small scabbed wound to lg abscess - CS Secondary lesion
-2-4d primary lesion develop into discrete, circular, ulcerated papules
-ulcers become covered in scabs & healing complete by 6wk
-cats show no signs other than skin lesions but 20% develop mild coryza or conjunctivitis
-complication from secondary bacterial inf
Describe cow pox in humans.
- Transmission
-direct contact w cats (most common)
-rarely from rodents/zoo animals
-virus not commonly found in cattle - CS
-macropapular lesion on hands & face -> develop into vesicular & ulcerative lesions
-enlarged painful local LN
-fever, vomit, sore throat
Describe monkey pox in humans.
viral zoonosis w symptoms in humans similar to those seen in small pox patients
1. Transmission
-primary inf: direct contact w blood, body fluids, rash of inf animal (monkey, Gambian rat, squirrels in Africa)
-secondary inf: close contact w inf respiratory tract excretion w the skin lesion of inf person or recently contaminated objects
Describe the different types of parapox viruses.
- Pseudocowpox virus (cattle & humans)
- Contagious ecthyma/orf virus (sheep, goat, human)
- Bovine papular stomatitis virus (cattle, humans)
Describe pseudocowpox virus.
- Definition
-viral skin disease that causes mild sores on teats & udder of cattle
-inf humans = milks nodules
>dairy farmer, vet - Etiology
-member of parapoxvirus - Epidemiology
-most countries - Transmission
-source of inf = inf cattle
-contaminated milk hand, teat cup
-biting insect
-calves inf during suckling inf teats
-semen of bulls - Pathogenesis
-hyperplasia or squamous epi - CS
-mild
Describe pseudo cow pox virus acute VS chronic lesions.
- Acute
Erythema -> papules -> vesicle or pustule -> rupture -> scab
-scab becomes elevated due to accumulation of granulation tissue
-after 7-10d the scab falls off leaving a horseshoe shaped ring of small scabs surrounding a small wart like granuloma - Chronic
-start as erythema
-yellow gray, soft scurfy scabs rubbed off during milking
-skin is corrugated
-no pain
-lesion persist for months
Describe the diagnosis & differential diagnosis of pseudocowpox.
- Diagnosis
-horse shoe shaped ring like lesion = pathognomic
-isolation & detection of virus via various diagnostic lab methods from vesicular fluid or from teat skin - Differential diagnosis
-cow pox virus
-bovine herpes virus ulcerative mammilitis
-vesicular stomatitis
-udder impetigo (bacterial dermatitis = sm pustules)
-teat chaps & frost bite
-black spot (hyperkeratosis)
Describe the treatment & prevention of pseudocowpox.
- Treatment
-removal of scabs
-burn scabs to prevent environmental contamination
-apply emollient ointment before milking
-apply astringent prep after milking - Prevention
-disinf + iodophor teat dip
-isolation & treatment of inf cow
-reduce teat trauma
Describe contagious ecthyma.
‘Orf’
1. Etiology
-parapoxvirus
2. Host
-sheep, goat (mostly lamb, kids)
3. Distribution
-worldwide
Describe contagious ecthyma transmission.
-scab fall off have virus
-virus stable in environment for long time under dry conditions
-contaminated instruments (docking, ear tagging)
-rapid spread
-inf healthy animal thru damage skin
-oral lesion in lambs or kids from nursing dams w teat lesions (vice versa)
Describe contagious ecthyma pathogenesis.
-damage of skin establish inf
-skin reaction to viral inf = cell response w necrosis & sloughing of epi & underlying stratum papillare of dermis
-cutaneous response to inf = delayed type hypersensitivity reaction + influx of inflam cells
Macule -> papule -> vesicle -> pustule -> ulcers -> scab
Describe the clinical signs of contagious ecthyma.
-first lesion in mucocutaneous junction + swelling of lips -> spread to muzzle & nostril surrounding hairy skin & buccal mucosa
>discomfort from lesion -> anorexia & weight loss
-affected lambs/kids inf ewes or goats = lesion on teat
>secondary bacterial inf -> mastitis
-severe: lesion in genital, coronets, ears
>lameness, infertility
-scabs drop off & underlying tissue heal w/o scarring -> complication from secondary bacterial inf or invasion of lesion by fly larvae
-malignant form of disease seen in sheep
Describe contagious ecthyma vaccine.
-prepared from suspension of scabs in glycerol saline & painted onto small area of scarified skin inside thigh = localized lesion develops
-DONT vaccinate on farms that dont have an issue w orf
-inspect lamb 1 week after vaccine for local reaction = indicated viability of vaccine
-vaccine last for 1-2y (not long lasting immunity)
-vaccinate:
1. Problem flocks/herds & lambs/kids
2. Pregnant ewes before lambing
Describe orf in humans.
-macropapular lesion & lg nodular lesion in finger, hand, arm, face, penis
-secondary bacterial inf cause complications
Describe Capripoxvirus.
- Sheep pox
- Goat pox
- Lumpy skin disease of cattle
Describe sheep pox & goat pox.
*thought to be strain of same virus but genetic seq demonstrated sep virus
*most strain host specific & cause severe CS in sheep/goat while some have equal virulence in both species
-cant be distinguished via serological test like viral neutralization
-related to lumpy skin disease in cattle (LSDV doesnt cause disease in shoats)
1. Etiology
-capripox virus
2. Distribution
-endemic in Africa, Asia, parts of Europe
Describe the transmission of sheep pox & goat pox.
-highly contagious
-virus enter respiratory tract & transmission by aerosol route
-spread thru MM or abraded skin, esp by direct contact w contaminated iatrogenic materials
-virus present in nasal & oral secretion for weeks after inf
-virus survive in dry scab for months
-mechanical transmission by biting arthropods
Describe the pathogenesis of sheep pox.
-systemic disease
-incubation period followed by leukocyte associated viremia
-virus localizes in skin & internal organs
-deposit immune complex result in severe necrotizing vasculitis in arterioles & post capillary venules of skin (type III HS) = ischemic necrosis of dermis & overlying epi
Describe the clinical signs of sheep pox.
- Malignant form
-lambs & sus non native breeds (merino)
-pox lesion on skin & buccal, respiratory, digestive & urinary tract mucosa -> pharynx, larynx, lungs, vagina, abomasum, spleen
-secondary pneumonia common & abortion is rare
-cutaneous nodule over whole body -> become vesicular, pustular, then scab
-lesion heal leaving star shaped scar free of hair/wool
-high mortality & case fatality rate (50%) - Benign form
-more common in adults & resistant breeds
-only skin lesion
-no or milk systemic reaction
Describe sheep pox prevention & vaccine.
- Prevention
-notifiable !!! - Vaccine
-lg variety of commercial vaccine
-subunit, killed (temporary protection), live attenuated (>1 yr)
Describe goat pox.
-Africa, Asia, parts of Europe
-reportable !!!
-clinical similar to sheep pox
-young kinds suffer systemic disease
-milder form on adults
Describe lumpy skin disease.
- Etiology
-capripoxvirus - Distribution
-enzootic in sub Saharan Africa, Middle East, iraq - Transmission
-arthropod vector (most common)
-direct contact - Host
-cattle of all ages & types are sus - CS
-fever, multi nodular lesions on skin & MM, lymphadenopathy
Describe suipoxvirus.
‘Swinepox’
1. Etiology
-suipoxvirus
2. Distribution
-worldwide
-sporadic
3. Host
-pigs
-benign w low mortality & low morbidity in older pig
-high case fatality in congenital inf & young suckling pig
4. Transmission
-direct contact w skin injury
-virus survive in scab for yrs
-mechanical transmission by pig louse Haematopinus suis (carry virus for weeks or months), flies, insects
-transplacental inf of neonatal pig
5. Control
-eradicate lice
-no vaccine
Describe swine pox clinical signs.
-typical pox lesion
>anywhere but mostly skin of abdomen & inner thigh
-exudative epi (greasy pig disease) & secondary bacterial dermatitis
-severe: esp congenital inf -> lesion occur in URT & GIT
Describe Avipoxvirus.
‘Fowl pox’
1. Etiology
-Avipoxvirus
2. Host
-highly inf disease of poultry & turkeys
3. Distribution
-worldwide
4. Transmission
-resistant to desiccation
-survive in exfoliated scabs for long periods
-routes:
>within flock thru wounds in mouth, comb, wattle, skin
>mechanically via mosquito, lice ,ticks
>aerosol
Describe the clinical signs of fowlpox.
- Cutaneous form (dry)
-most common
-low mortality
-results from injury by biting arthropod, mechanical transmission to injured skin
-small papule on comb, wattle, beak
>legs, feet, cloaca less common
-nodules become yellow -> scab
-fall in egg prod
-recover in 4 wk - Diphtheritic form (wet)
-caused by droplet inf
-inf of MM, pharynx, larynx, trachea
-lesion can cause death by asphyxiation
-poor prognosis - Ocular form
-conjunctivitis
-exudate under eye lid
Describe avipoxvirus bollinger & borrel bodies.
- Bollinger
-eosinophilic granular intracytoplasmic inclusion bodies - Borrel
-occur inside bollinger bodies
-spherical bodies obtained by tryptic digestion of bollinger bodies
Describe fowlpox control.
- Vaccine
-modified live fowlpox or pigeon pox virus of chicken embryo or avian cell culture origin avail commercially
-recombinant fowl pox vectored vaccines - Control mosquito & other biting insects
Describe unclassified pox virus.
‘Ulcerative dermatosis of sheep’
1. Transmission
-virus inf thru damaged skin or by coitus
2. CS
lesion usually ulcers w raw crater that bleeds easily
A) lip & leg ulceration
B) venereal form
>transmitted ulceration of prepuce & penis or vulva
>ram becomes unfit for natural breeding
Describe the diagnosis of poxvirus.
- CS
- Sampling material
-scrape skin lesion, vesicular fluid, crust, scab - Electron microscopy
-morphology & size - Histopath
intracytoplasmic inclusion bodies
A) type B or Guarneri inclusion bodies = most poxvirus
>slightly basophilic
>viral particles & protein aggregates
B) type A or ATI inclusion bodies
>cowpox & ectromelia virus
>strongly eosinophilic
C) bollinger & borrel bodies
>avipoxvirus - Inoculation in embryonated egg
>CAM = pock lesion
>parapoxvirus dont multiply in chicken embryo - Serological assay (ELISA)
- Detection of poxvirus nucleic acid by PCR