Sheep scab, lice and keds

What does psoroptes ovis cause

Sheep scab / ovine psoroptic mange

What does psoroptes ovis look like

What are the symptoms of psoroptes ovis

• Intense itching

• Lesions

• Wool loss

What countries is psoroptes ovis found in

• Worldwide

• Eradicated from New Zealand and Australia

What is the life cycle of psoroptes ovis

What does psoroptes ovis feed on

• Surface of skin

• Lipids

• Superficial fluids

• Cells

• Bacteria

• Lymph

What is the pathogenesis of psoroptes ovis

• Type 1 hypersensitivity response

• Chronic exudative superficial dermatitis

• Centre of lesion formes a crust, mites move to edge, more hypersensitivity and lesions grow

• Mites density highest around moist edge of lesion

What are the clinical signs of psoroptes ovis

• Chronic skin changes

• Aural haematomas

• Lesions across neck, back, shoulders, flank

• Intense pruritis

• 30% decrease in weight gain

• Weight loss

• Decrased birth weight

• Restlessness

• Wool loss

• Epileptiform seizures

• Death

• Secondary bacterial infections

How is psoroptes ovis diagnosed by blood ELISA

Detects IgG in sheep serum 2 weeks after infestation and before appearance of clinical signs

How is psoroptes ovis diagnosed by clinical signs and mite ID

1. Part wool to examine for lesions

2. Superficial skin scrapes using a scalpel

3. Macerate material in 1-5% KOH for 5-10 minutes to release mites

4. View under microscope and look for live mites, cuticles and eggs

What is the morphology of psoroptes ovis

How are forage mites identified

By lack of thumbprint striations

How is psoroptes ovis transmitted

• Direct contact - common grazing, neighbours sheep

• Indirect fomites - mites survive off host for 16 days

How are new infestations introduced to a farm

• Mixing with other farms on common grazing

• Bought in sheep not treated on arrival

• Rented land contaminated by previous occupants

• Poor fencing

• Contaminated lorries, shears, trailers

• Contact in markets or fomites in showing pens

What is the epidemiology of psoroptes ovis

• Late autumn/winter disease

• Upland regions

• Longer fleece in winter

• Shearing reduced population in summer

What is the current legislation on sheep scab

• Sheep scab order 1997

• Sheep scab order 2010

• Legal requirement to treat affected sheep and entire flock, movement restrictions, notifiable disease in Scotland

How do you prevent infestation of psoroptes ovis

• Quarantine and test bought in sheep

• Consider options for sheep returning from markets

• Disinfect shearing equipment

• Double fencing

How do you treat psoroptes ovis prophylactically

• Organphosphate dip - protects for 60 days

• Moxidectin injection 1% - protects for 28 days

• Moxidectin injection LA - protects for 60 days

How do you treat psoroptes ovis infection

• Dipping with organophosphate - 60 seconds and head under twice

• Moxidectin injection 1% - 2 times 10 days apart

• Moxidectin injection LA

• Doramectin injection

• Ivermectin injection - 2 times 7 days apare

What does chorioptes bovis cause

Chorioptic mange

What do chorioptes bovis mites look like

How does chorioptic mange compare to sheep scab

More common but less severe

What is bovicola ovis

• Chewing louse

• Common world wide

What are the less important sucking lice of sheep

• Linognathus pedalis - foot louse

• L. ovillus - face louse

What are the clinical signs of bovicola ovis

• Wool loss

• Restlessness

• Itching

• Reduced appetite

• Rubbing

• Lesions attract blowflies

How is bovicola ovis diagnosed

• Adult lice next to skin

• Eggs on wool

What is the epidemiology of lice

• 11% prevalence

• Upland farms and common grazing are risk factors

• Severity varies between individuals

How are lice controlled

• Quarantine bought in stock for 3 weeks

• Remove potential fomites from housing

• Severity varies between individuals

• Shearing reduces populations

• Accurate diagnosis to inform correct control

How are lice treated

Synthetic pyrethroids or organophosphate dip

What is melophagus ovinus

• Sheep ked

• Diptera fly without wings

What does melophagus ovinus look like

What is the epidemiology of melophagus ovinus

Mainly a winter problem

What is the pathogenesis of melophagus ovinus

1. Suck blood

2. Cause pruritis

3. Loss of condition

What do melophagus ovinus transmit

Non-pathogenic Trypanosoma melophagium