FASH14: Foot and Skin Conditions of Sheep Flashcards
What are the ectoparasitic causes of sheep skin disese?
- Sheep scab (Psoroptes ovis)
- Blowfly strike (myiasis)
- Lice (Bovicola ovis & Linognathus spp)
- Ticks
What are the non-parasitic causes of sheep skin disese?
- Orf
- Caseous lymphadenitis
- Dermatophilosis
- Photosensitization
- Ringworm
What is the agent of sheep scab?
Psorptes ovis
Is sheep scab a notifiable disease?
Yes
How long to scabbies mites last in the environment?
up to 17 days
Describe the pathogenesis of Sheep Scab.
Following infection up to 3-21 days before clinical signs
Immediate and delayed hypersensitivity reactions
Inflammation > microclimate favourable for mite survival and multiplication
Serous exudate > nutrition for mites
How do you diagnose sheep scab?
Skin scrapes
ELISA antibody test
How do you treat sheeb scab?
Plunge dipping in diazinon
Systemic endectocide injections - macrocyclic lactones
What are the advantages of a plunge organophosphate dip for treatment of sheep scab? Disadvantages?
Advantages
- Kills mites within 24 hours
- Washing effect removes dead mites
- Residual protection for several weeks
- Also controls blowfly, live, keds, ticks
Disadvantages
- Humenvironmentalnmnetal hazards
- Operator requires certificate of competence
- Adequate facilities
- Stressful procedure for sheep
- Long meat withdrawal periods (70 days)
What are the advantages and disadvantages of a macrocyclic lactone injection as treatment for sheep scab?
- Advantages
- Less complex to administer
- Safer for operator, sheep, and environment
- Residual protection for several weeks
Disadvantages
- Pruritus may persist for up to 30 days
- Takes time to kill mites
- Promotes anthelmintic resistance
- Narrow range of efficacy against other ectoparasites
- May not treat all animals
How to you control against sheep scab?
- Beware of carrier sheep (purchased, returning away from grazing, strays)
- Mites in the environment
- GAther and treat all sheep at the same time
- Use appropriate treatment and dose
- COordinate treatment with neighbouring farms
What is another name for blowfly strike?
Myiasis
When does blowfly strike hit?
May-sept
Describe the pathogenesis of blowfly strike.
Flies are attracted to soiled areas of fleece > lay eggs > hatch within 12 hours > larvae penetrate skin and secrete enzymes > irritation > secondary bacterial infection and strike > toxaemia
How do you control against blowfly strike?
Plunge dipping at least 3 weeks after shearing
Pour on (synthetic pyrethroids or insect growth regulators)
Farm management
What are the types of lice that affect sheep?
Chewling live - Bovicola ovis
Sucking live - linognathus ovillus or pedalis
Describe the life cycle of chewing lice.
Entire life cycle is spent on the host in about 30 days
Slow spread of infection - requires clsoe contact
How do you diagnose chewing lice?
Visible to nake eye when wool parted
How do you treat against chewing lice?
Shearing
Plunge dipping
Synthetic pyrethroid pour ons (after shearing)
SYSTEMIC ENDECTOCIDES ARE NOT EFFECTIVE
What species of tick attack sheep?
Ixodes ricinus
What disease do tick carry that affect sheep?
Tick-borne fever
Tick pyaemia
Louping-ill
Q fever
How do you control against ticks?
Plunge dips
Pour-on
Grazing management
What is another name for Orf?
Contagious pustular dermatitis
What is the agent of Orf?
Parapox virus
Describe the epidemiology of orf.
Dry scab material remains infectious for a number of years - persists in buildings
PI animals
Outbreaks most common in suckling lambs born indoors
How do you treat/manage orf?
Natural recovery 24-30 days
Topical or parenteral antibiotics for secondary bacterial infection
Reduce stocking densities
Vaccinate
Weed management
Separate affected sheep
What is the agent of caseous lymphadenitis?
Corynebacterium pseudotuberculosis
How is caseous lymphagenitis spread?
Via skin abrasions
What do casous lymphadenitis look like?
Abscesses in regional lymph nodes
How do you diagnose caseous lymphadenitis?
Bacterial culture from infected nodes
How to do you treat caseous lymphadenitis?
No treatment
How do you control against caseous lymphadenitis?
Isolate or cull animls with discharging lesions
Hygiene at shearing and dipping
What is another name for dermatophilosis?
Lumpy wool
What is the agent of dermatophilosis?
Dermatophilus congolensis
How do you treat dermatophilosis?
self cure or penicillin
