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Sheep > Sheep Skin Disease > Flashcards

Sheep Skin Disease Flashcards

1
Q

Name 4 common ectoparasites of sheep

A

Sheep scab (psoroptes ovis)
blowfly strike (myiasis)
Lice (bovicola ovis linognathus spp)
and Ticks

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2
Q

Name 5 non-parasitic causes of skin disease

A 
Orf
caseous lymphadenitis
dermatophilosis
photosensitization
ringworm
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3
Q

Cause of sheep scab?

A

Psoroptes ovis (host-specific mite)

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4
Q

Epidemiology of sheep scab - (spread? how long in environment?)

A

Mites in env for up to 17d

Direct contact spread

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5
Q

What time of the year are sheep scab outbreaks?

A

Winter/spring

optimal for multiplication of mites

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6
Q

What do sheep scab mites use for nutrition?

A

serous exudate, gross

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7
Q

CS of sheep scab

A

Early cases = discoloration of wool, serous exudate initially on shoulders

  • starts w/ one animal, but then whole flock
  • INTENSE PRURITUS - “nibbling” reflex common
  • more advanced cases = WOOL LOSS, “sore” lesions, increase in size, scab formation (abscesses), Death
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8
Q

Diagnosis of sheep scab?

A

Skin scrapes, ELISA Ab test: Psoo2 (mite antigen)

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9
Q

Sheep scab treatment

A

Plunge dipping - Diazinon (organosphosphate)

Systemic endectocide injections - Macrocyclic lactones

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10
Q

Advantages and disadvantages of sheep scab dipping?

A 
advantages = kills w/in 24 hours, washing removes dead guys, residual protection for weeks, also controls blowfly, lice, keds, ticks
disadvantages = hazards, operator needs certificate, stressful for sheep, 70d meat withdrawal period
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11
Q

Advantages and disadvantages to macro lactone injections for sheep scab?

A 
Advantages = less complex, safer, residual protection for several weeks
Disadvantages = pruritis may persist for up to 30 days, takes time to kill mites, anthelmintic resistance, narrow range efficacy against other parasites, may not tx all animals
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12
Q

Control of sheep scab

A

Gather and treat all sheep at the same time
Use correct tx and dose
coordinate w/ neighboring farms

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13
Q

When does blowfly strike occur?

A

Summer months (may-sept)

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14
Q

What are flies attracted to?

A

Soiled areas of fleece. (tail, breech, skin lesions, footrot lesions).

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15
Q

What is pathogenesis of blowfly strike?

A

Lay eggs -> hatch w/in 12 hours -> larvae penetrate skin, and secrete enzymes -> irritation -> secondary bacterial infection and strike -> toxemia

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16
Q

CS of blowfly strike

A

Restlessness, bite/kick affected area

Discolored (grey), moist wool and offensive smell, wool loss, and moist dermatitis, toxemia, death

17
Q

Control of blowfly strike

A

Change to a wool shedding breed.
Plunge dipping (OP dips) - at least 3 weeks after shearing
-Shower dipping
-Pour ons (synthetic pyrethroids, insect growth regulators)

18
Q

Name the sheep lice - chewing (1) & sucking (2)

A 
Chewing = bovicola ovis
Sucking = linognathus ovillus and pedalis
19
Q

CS of chewing lice

A
  • Dorsum and flanks feeding on skin debris
  • Irritation and intense pruritis
  • Rubbing/biting shoulders, flanks, back
  • Broken wool, matting, & discoloration
20
Q

Tx chewing lice

A

Shearing, plunge dipping (OP), synthetic pyrethroid pour-ons (most effective right after shearing)
Systemic endecotocides NOT effective

21
Q

What is the common name for contagious pustular dermatitis?

A

Orf

Zoonotic!!

22
Q

What kind of virus is Orf?

A

parapox virus

23
Q

Is there colostral transfer of immunity with Orf?

A

No

24
Q

CS of Orf

A
  • Proliferative lesions on lips and nostrils of lambs
  • Lesions of teats of nursing ewes (mastitis)
  • Persistent proliferative lesions (ex- head/poll of rams, ears)
  • scabs contain live virus
25
Q

Transmission of Orf

A

Dry scab material remains infectious for several months - persists in buildings, can get PI carrier animals

  • Grazing lambs (post weaning) on rough pasture
  • hungry, infected, lambs try to steal milk from other ewes
26
Q

Diagnosis of Orf

A

CS, Virus culture/microscopy on moist scabs

27
Q

DDx for Orf

A

Foot and Mouth disease, Bluetongue, Sheep pox

28
Q

Tx / management of Orf

A
  • Natural recovery (24-30 days), oral lesion = nursing
  • Topical or parenteral abx for 2ndry infection
  • reduce stocking density
  • Vaccination! (live vaccine - Scabivax)
  • Weed management
29
Q

What causes caseous lymphadenitis (CLA)?

A

Corynebacterium pseudotuberculosis

30
Q

CS of CLA

A

Firm, palpable swellings involving LN of head and neck (parotid, submandibular) or anywhere

occasionally rupture and discharge pus
~25% infected sheep have internal abscesses only (ill thrift)

31
Q

Diagnosis of CLA

A

Bacterial culture from infected nodes,

Serology - ELISA

32
Q

Risk factors for CLA and transmission

A

Risk factors = housing, high stocking rates, trough feeding, shearing

Transmission = discharging, entry via wounds on head or mouth abrasions
(bacteria survive in soil/sheds and in sheep dip)

33
Q

CLA management/ control

A

-No treatment
-Isolate or cull animals w/ discharging lesions
hygiene
-blood test and cull -seropositive animals
-vaccination (none licensed in UK, but can be imported)

34
Q

What causes photosensitization?

A

Plants containing photodynamic agents (ex- St. John’s wort) (primary cause)

(secondary) hepatotoxic damage (bog Asphodel - saponins?)

35
Q

CS photosensitization

A

Unpigmented skin -> skin necrosis and sloughing -> may also affect the wool parting

36
Q

Dermatophilosis - what is is caused by and what is the common name?

A

Lumpy wool, dermatophilus congolensis

37
Q

What are CS of lumpy wool? what weather is it associated with?

A

Papul and crust formation on ears/nose/dorsum
Generally NOT pruritic

associated w/ prolonged wet weather

38
Q

Tx lumpy wool

A

Self-cure or abx (penicillin)

39
Q

What is strawberry footrot?

A

Infection w/ orf virus AND dermatophilus congolensis

-affects lower libs and rest of body, rather than feet

  • if remove scab, see ulcerated, bleeding raw surface (like strawberry)
  • usually self resolving

Sheep (11 decks)

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