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

Sheep Skin Disease Flashcards by Caitlin Riley

Name 4 common ectoparasites of sheep

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

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Name 5 non-parasitic causes of skin disease

Orf
caseous lymphadenitis
dermatophilosis
photosensitization
ringworm

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Cause of sheep scab?

Psoroptes ovis (host-specific mite)

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

Mites in env for up to 17d

Direct contact spread

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What time of the year are sheep scab outbreaks?

Winter/spring

optimal for multiplication of mites

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What do sheep scab mites use for nutrition?

serous exudate, gross

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CS of sheep scab

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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Diagnosis of sheep scab?

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

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Sheep scab treatment

Plunge dipping - Diazinon (organosphosphate)

Systemic endectocide injections - Macrocyclic lactones

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Advantages and disadvantages of sheep scab dipping?

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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Advantages and disadvantages to macro lactone injections for sheep scab?

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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Control of sheep scab

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

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When does blowfly strike occur?

Summer months (may-sept)

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What are flies attracted to?

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

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What is pathogenesis of blowfly strike?

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

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CS of blowfly strike

Restlessness, bite/kick affected area

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

Control of blowfly strike

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)

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

Chewing = bovicola ovis
Sucking = linognathus ovillus and pedalis

CS of chewing lice

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

Tx chewing lice

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

What is the common name for contagious pustular dermatitis?

Orf

Zoonotic!!

What kind of virus is Orf?

parapox virus

Is there colostral transfer of immunity with Orf?

CS of Orf

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

Transmission of Orf

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

Diagnosis of Orf

CS, Virus culture/microscopy on moist scabs

DDx for Orf

Foot and Mouth disease, Bluetongue, Sheep pox

Tx / management of Orf

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

What causes caseous lymphadenitis (CLA)?

Corynebacterium pseudotuberculosis

CS of CLA

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)

Diagnosis of CLA

Bacterial culture from infected nodes, | Serology - ELISA

Risk factors for CLA and transmission

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)

CLA management/ control

-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)

What causes photosensitization?

Plants containing photodynamic agents (ex- St. John's wort) (primary cause) (secondary) hepatotoxic damage (bog Asphodel - saponins?)

CS photosensitization

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

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

Lumpy wool, dermatophilus congolensis

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

Papul and crust formation on ears/nose/dorsum Generally NOT pruritic associated w/ prolonged wet weather

Tx lumpy wool

Self-cure or abx (penicillin)

What is strawberry footrot?

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