Poxviridae

Question 1

Describe the look of pox viruses VS parapoxvirus.

Answer 1

1. Poxvirus
   -lg, some enveloped, DNA virus, complex symmetry
   -pleomorphic, brick shaped, irregular surface w tubular/globular structures projecting
2. Parapoxvirus
   -ovoid w thread like surface tubules arranged in cross cross

Question 2

Describe IMV & EEV of pox viruses.

Answer 2

1. IMV
   -intracellular mature virus
   -infectious
   -inner membrane only
   -virions released by disruption of host cell
2. EEV
   -extracellular enveloped virus
   -infectious
   -envelope + inner membrane
   -virions released via budding
   *IMP for spread of virions bc taken up by cells more readily

Question 3

Describe pox virus structure.

Answer 3

-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

Question 4

Describe replication in poxvirus.

Answer 4

-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)

Question 5

Describe stability of poxvirus.

Answer 5

-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

Question 6

Describe transmission of poxvirus.

Answer 6

transmitted between animals
1. Skin
-cant inf intact skin
2. Respiratory route
-inhale aerosol
3. Mechanically transmitted
-biting arthropods (myxoma virus & avipoxvirus)

Question 7

Describe the pathogenesis & immunity of poxvirus.

Answer 7

-highly epitheliotropic = cause cutaneous skin lesion
-systemic disease in bird & wild animals
-host specific
>orthopoxvirus inf wide range of species

Question 8

Describe the spread of poxvirus.

Answer 8

-systemic circ via lymphatic system
-secondary viremia disseminates the virus back to skin & other target organ

Question 9

Describe the skin lesions in pox virus infection.

Answer 9

Ma
Pa
Ve
Pu
Sca sca

Question 10

Describe orthopoxvirus.

Answer 10

‘Cowpox’
1. Distribution
-endemic in Europe & Asia
2. Host
-cattle, cats, humans, zoo animals, etc
3. Reservoir
-rodents

Question 11

Describe cowpox in cattle.

Answer 11

1. Transmission
   -cow to cow via inf milker hand or teat cup
   -inf farm cats can transmit disease
2. Economic imp
   -loss of $ to farmer bc of milking = soreness of teats & mastitis from secondary bacterial inf
3. 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

Question 12

Describe cow pox in cats.

Answer 12

1. Transmission
   -skin inoculation (bite or wound)
   -rodents
   -exotic cat = viral pneumonia
2. CS Primary lesion
   -skin lesion on head, neck, forelimb
   -small scabbed wound to lg abscess
3. 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

Question 13

Describe cow pox in humans.

Answer 13

1. Transmission
   -direct contact w cats (most common)
   -rarely from rodents/zoo animals
   -virus not commonly found in cattle
2. CS
   -macropapular lesion on hands & face -> develop into vesicular & ulcerative lesions
   -enlarged painful local LN
   -fever, vomit, sore throat

Question 14

Describe monkey pox in humans.

Answer 14

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

Question 15

Describe the different types of parapox viruses.

Answer 15

1. Pseudocowpox virus (cattle & humans)
2. Contagious ecthyma/orf virus (sheep, goat, human)
3. Bovine papular stomatitis virus (cattle, humans)

Question 16

Describe pseudocowpox virus.

Answer 16

1. Definition
   -viral skin disease that causes mild sores on teats & udder of cattle
   -inf humans = milks nodules
   >dairy farmer, vet
2. Etiology
   -member of parapoxvirus
3. Epidemiology
   -most countries
4. Transmission
   -source of inf = inf cattle
   -contaminated milk hand, teat cup
   -biting insect
   -calves inf during suckling inf teats
   -semen of bulls
5. Pathogenesis
   -hyperplasia or squamous epi
6. CS
   -mild

Question 17

Describe pseudo cow pox virus acute VS chronic lesions.

Answer 17

1. 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
2. Chronic
   -start as erythema
   -yellow gray, soft scurfy scabs rubbed off during milking
   -skin is corrugated
   -no pain
   -lesion persist for months

Question 18

Describe the diagnosis & differential diagnosis of pseudocowpox.

Answer 18

1. Diagnosis
   -horse shoe shaped ring like lesion = pathognomic
   -isolation & detection of virus via various diagnostic lab methods from vesicular fluid or from teat skin
2. 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)

Question 19

Describe the treatment & prevention of pseudocowpox.

Answer 19

1. Treatment
   -removal of scabs
   -burn scabs to prevent environmental contamination
   -apply emollient ointment before milking
   -apply astringent prep after milking
2. Prevention
   -disinf + iodophor teat dip
   -isolation & treatment of inf cow
   -reduce teat trauma

Question 20

Describe contagious ecthyma.

Answer 20

‘Orf’
1. Etiology
-parapoxvirus
2. Host
-sheep, goat (mostly lamb, kids)
3. Distribution
-worldwide

Question 21

Describe contagious ecthyma transmission.

Answer 21

-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)

Question 22

Describe contagious ecthyma pathogenesis.

Answer 22

-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

Question 23

Describe the clinical signs of contagious ecthyma.

Answer 23

-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

Question 24

Describe contagious ecthyma vaccine.

Answer 24

-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

Question 25

Describe orf in humans.

Answer 25

-macropapular lesion & lg nodular lesion in finger, hand, arm, face, penis
-secondary bacterial inf cause complications

Question 26

Describe Capripoxvirus.

Answer 26

1. Sheep pox
2. Goat pox
3. Lumpy skin disease of cattle

Question 27

Describe sheep pox & goat pox.

Answer 27

*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

Question 28

Describe the transmission of sheep pox & goat pox.

Answer 28

-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

Question 29

Describe the pathogenesis of sheep pox.

Answer 29

-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

Question 30

Describe the clinical signs of sheep pox.

Answer 30

1. 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%)
2. Benign form
   -more common in adults & resistant breeds
   -only skin lesion
   -no or milk systemic reaction

Question 31

Describe sheep pox prevention & vaccine.

Answer 31

1. Prevention
   -notifiable !!!
2. Vaccine
   -lg variety of commercial vaccine
   -subunit, killed (temporary protection), live attenuated (>1 yr)

Question 32

Describe goat pox.

Answer 32

-Africa, Asia, parts of Europe
-reportable !!!
-clinical similar to sheep pox
-young kinds suffer systemic disease
-milder form on adults

Question 33

Describe lumpy skin disease.

Answer 33

1. Etiology
   -capripoxvirus
2. Distribution
   -enzootic in sub Saharan Africa, Middle East, iraq
3. Transmission
   -arthropod vector (most common)
   -direct contact
4. Host
   -cattle of all ages & types are sus
5. CS
   -fever, multi nodular lesions on skin & MM, lymphadenopathy

Question 34

Describe suipoxvirus.

Answer 34

‘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

Question 35

Describe swine pox clinical signs.

Answer 35

-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

Question 36

Describe Avipoxvirus.

Answer 36

‘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

Question 37

Describe the clinical signs of fowlpox.

Answer 37

1. 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
2. Diphtheritic form (wet)
   -caused by droplet inf
   -inf of MM, pharynx, larynx, trachea
   -lesion can cause death by asphyxiation
   -poor prognosis
3. Ocular form
   -conjunctivitis
   -exudate under eye lid

Question 38

Describe avipoxvirus bollinger & borrel bodies.

Answer 38

1. Bollinger
   -eosinophilic granular intracytoplasmic inclusion bodies
2. Borrel
   -occur inside bollinger bodies
   -spherical bodies obtained by tryptic digestion of bollinger bodies

Question 39

Describe fowlpox control.

Answer 39

1. Vaccine
   -modified live fowlpox or pigeon pox virus of chicken embryo or avian cell culture origin avail commercially
   -recombinant fowl pox vectored vaccines
2. Control mosquito & other biting insects

Question 40

Describe unclassified pox virus.

Answer 40

‘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

Question 41

Describe the diagnosis of poxvirus.

Answer 41

1. CS
2. Sampling material
   -scrape skin lesion, vesicular fluid, crust, scab
3. Electron microscopy
   -morphology & size
4. 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
5. Inoculation in embryonated egg
   >CAM = pock lesion
   >parapoxvirus dont multiply in chicken embryo
6. Serological assay (ELISA)
7. Detection of poxvirus nucleic acid by PCR