Mites As Parasites Flashcards
Mite pathway to inflammation
Mechanical abrasion and allergen deposition cause skin barrier disruption
Activates 1o rec cause release of inflam med IL6&8 and TNF trigger pro inflam cascade cause selectin and integrin expr
Cause leukocyte extravasation activating local DCs bridging innate to adaptive resp and causing loxal skin inflam
DC cell act TH2 resp which causes further disruption
Host resp to mange mites
Prod immediate inflam resp
Adaptive imm resp bia APCs
Innate imm eg eosins in stratum corneum
Protective imm takes time to dev
Adaptation to surf living
Large mites
Stout bodies
Long legs
Adaptation to living in epidermis
Small mites
Flattened round bodies
Short legs
Adaptation to living within follicle
Small Elongated body
Very stubby legs
Adaptation to free living
Large
Very long legs
Diagnosis of infestations in diff areas
Surf: tape strip or superficial skin scrape
Burrowing: deep skin scrap
Hair follicle: squeeze pustules onto slide
Specific sites: direct observation
Other diagnostic tests: haematology, chemistry, serology
Mange diagnosis
Clinical signs
Lesion distribution
Mite ID on skin scrapes or adhesive tape
Mange mite lifecycle
Eggs laid on skin (or other niche) and larvae dev in approx 3d
Larvae feed for 3-7d then moult
Nymphs emerge and change into males and pubescent females after 5d
About 3-4wk to complete
All dev stages on host and transmission by close contact (or rarely short survival period on fomites)
Susceptible to dessication so dont survive long off host
rarely able to infect new host of survived off host
Psoroptes ovis lifecycle
Same as gen mange mite lifecycle
Psoroptes ovis
Sheep scab
Cause of intense pruritus and after 6 wk wool loss and skin damage timescale dep on strain of mite, time of hr, length of wool, etc
Important animal welfare concern
Important cause of production loss
ND in scotland
Large money spent on inneffective disease control
Sheep scab as an ND
Legal obligation to notify DVM in scotland
Voluntary movement restrictions until treated slaughtered or negatively diagnosed
Failure to act can lead to compulsory movement restrictions and req to treat or slaughter affected animal in absence of negative diagnosis
Persistent offence can lead to prosecution
Powers to act when sheep scab discovered at market and deal with stray sheep
Sheep scab symptom progression
6wk post: clear serous exudate, crust formation which adheres to wool fibres and start to lift off skin
10wk post: wool loss area, skin with no wool is dry and hardened and hyperkeratatic, margin area exudative
3mnth post: epiderm split into layers and mite pop between each layer
Exudate is pro rich and so become quickly hyperprotonaemic so lose weight
Psoroptes cuniculi
Rabbit ear canker
Diff to distinguish from ovis
Localise ears and prolif to severe mange
Scales cont parasite, mite eggs, skin cells and blood can block auditory canal
Untreated can spread to whole body causing pruritus hair loss and debilitation
Chorioptes
Surf mites with bell shaped suckers on short pedical
Hypersens reaction causing exudative dermatitis
Variable pruritis level along with scaling hair loss and crusting
Host specific variants