Sheep lice and keds Flashcards
What are the symptoms of Psoroptes ovis? Which species does it affect?
Intense itching, rubbing, scratch, nibbling
Sheep - rarely cattle and horses
What are the distinguishing features of Psoroptes ovis?
Pointed mouth Long setae (hair like strucutres) Long legs Jointed pedicles with 3 part trumpet Thumb print pattern on dorsum (all mange mites)
How long do Psoroptes mites live for? How many eggs do they lay? How long is their life cycle?
1 month
100
16 days
Are Psoroptes burrowing or non-burrowing?
Non-burrowing - feed at surface of skin
What are all mange mites sensitive to? What type of fleece does this mean they struggle to survive on?
Sensitive to desiccation
Struggle to survive on longer fleece
What are Psoroptes lesions like? Where are the mites found?
Inflammation, serous exudate, scale and crust. Centre is thick and crusty, vesicle ruptures to form moist yellow pustule
Mites found on moist skin at edge of resin
Psoroptes lesions spread rapidly and cover most of the body in weeks. What does this cause?
Chronic exudative superficialities dermatitis
Describe the pathogenesis of psoroptes ovis?
Type I hypersensitivity due to antigens in mite faeces
Causes chronic skin changes, hyperkeratosis, aural haematomas, intense irritation, decreased weight gain, seizures, death
How is psoroptes ovis diagnosed?
Clinical signs, skin scraping
What is sheep scab also known as? What is it caused by?
Psoroptic mange
Psoroptes ovis
What are the symptoms of sheep scab?
Pruritic, irritation Scratching against walls Wool loss Weight loss Stood alone Depressed Wool in mouth
What can be used to test for Sheep scab?
Nibble reflex - sheep respond to back scratching with lip and tongue movements
How is sheep scab transmitted?
Direct contact, contaminated environment, fomites
How long do Psoropes ovis survive off the host?
2 weeks
What introduces sheep scab to a flock?
Poor fencing, mixing flocks, contaminated lorries
What season is Sheep Scab usually seen?
Autumn/Winter
Shearing in Summer reduces population
Where are the sites of mites on sheep, that act of reservoirs?
Axilla (armpit)
Ears
Skin folds
What is the treatment for Sheep scab?
OPs - dip in Diazinon
Injectable MLs - ivermectin
What species of Psoroptes is found in rabbits? Where is it usually localised and what does it cause?
Psoropotes cunicoli
Ears - causes mange in auditory canal
Where about on sheep do Chorioptes bovis usually affect?
Lower limbs, abdomen
What are the 3 species of lice found in sheep? Which is biting and which is sucking?
Damalinia ovis (body louse) Linognathus pedalis (foot louse) Linognathus ovillus (face louse)
What are the symptoms of lice in sheep?
Restlessness, rubbing, stopping feeding, wool loss if heavy infestation
What do lice lesions attract?
Blowflies
How are lice controlled in sheep?
Shearing
Quarantine
Remove wool rom housing
What is the weird looking half tick half lice? What species is this?
Sheep keds
Melophagus ovinus
What is the morphology of sheep keds?
Flattened like lice
Short legs with stout claws
5mm
True flies but no wings
Where do larvae of Melophagus ovinus develop?
Inside female
Become pupa in wool
Emerge 2-5 weeks later
How are sheep keds transmitted? What do they cause?
Direct contact
Pruritis, loss of condition
What season are sheep keds usually present? Do they transmit pathogens?
Winter
Transmit non-pathogenic Trypanosoma melphagium
