Sheep skin disease (Yr 4) Flashcards
what causes orf?
parapos virus (zoonosis)
what are the clinical signs of orf?
vesicular/proliferative scabby lesions (mouth, head, teats)
painful lesions
teat lesions predispose to mastitis
poor growth
4-6 week duration to dry up
how can lambs be effected by orf?
interferes with sucking
lambs more commonly affected and spread to ewe via suckling
what is orf also known as?
contagious pustular dermatitis
how is orf spread?
direct contact with damaged skin/mouth (rough grazing/feed…)
more active indoors (dry conditions)
how is orf controlled?
isolate (hygiene)
clean and disinfect equipment
no treatment (treat secondary infection with antibiotics)
vaccine only on infected farms
is there a vaccine for orf?
yes - only use on confirmed infected farm as it is a live vaccine (so will infect uninfected flocks)
what mites are seen in sheep?
Psoroptes ovis (scab)
Chorioptes bovis
Trombicula
what are the main ticks seen in sheep?
Ixodes ricinus
Haemaphyllis punctuata
what are the main flies of concern in sheep?
Lucilia sericata
Hydrotea irritans
what is the main louse seen in sheep?
Bovicola ovis
what time of year is Psorptes ovis seen?
autumn/winter
how is Psorptes ovis transmitted?
direct contact and fomites
what are the clinical signs of Psorptes ovis (sheep scab)?
allergic reaction to mites…
pruritus, wool loss, scratching, distress
what does Psorptes ovis cause?
sheep scab
how should you sample when suspecting Psorptes ovis for a diagnosis?
choose itchiest worst effected sheep
sample at edge of exudative lesion (skin scrape)
what is the identifying feature of Psorptes ovis mites?
bell shaped sucker on the end pedicle
how can you diagnose Psorptes ovis (scab)?
antibody ELISA
skin scrapes
why is Psorptes ovis (scab) difficult to treat?
mite survives 17-19 days off of the host so reinfection can occur
how is Psorptes ovis (scab) treated?
dexamethasone if intensely itchy
organophosphate dip (diazinon)
macrocyclic lactones (ivermectin)
what organophosphate is used for Psorptes ovis (scab)?
diazinon (one minute dip)
what macrocytic lactones can be used for Psorptes ovis (scab)?
ivermectin, doramectin, moxidectin
(move to clean pasture after dose)
what is an issue with using macrocytic lactones to treat Psorptes ovis (scab)?
can cause resistance in GI nematodes
what is the distribution of Chorioptes bovis?
found on ventral abdomen (scrotum in males)
what effects does Chorioptes bovis have?
pruritus and hypersensitivity
scrotal mange (infertility)
how is Chorioptes bovis treated?
organophosphate dips (macrocytic lactones don’t work because mites don’t live deep enough)
what is the main louse of sheep?
Bovicola ovis
what type of louse is Bovicola ovis?
chewing
what conditions does Bovicola ovis thrive in?
warm dry housing….
shearing and rainfall reduce the numbers
how can Bovicola ovis be diagnosed?
part wool on back/flank and lice will be visible
how can Bovicola ovis be treated?
turnout (rain, shearing, light…)
synthetic pyrethroid pour on
organophosphate dip (diazinon)
what flies cause strike?
Lucilia sericata
how does Lucilia sericata cause strike?
lay eggs which hatch, these produce proteolytic enzymes causing necrosis and attracting more flies
what is the major risk factor for strike?
faecal soiling (lush pasture and worms) in summer months
how can strike be treated?
maggots - synthetic pyrethroid pour on, deltamethrin
clean and clip area, supportive care
what products are available to control strike?
organophosphate dips (diazinon)
synthetic pyrethroid pour ons
insect growth regulators (not for maggots)
what is the head fly that affects sheep?
Hydrotea irritans
what does Hydrotea irritans feed on?
ocular discharge (can be vector for disease spread)
what cause ovine sweet itch?
hypersensitivity to midges/mosquitoes (uncommon)
what causes peri-orbital eczema?
Staphylococcus aureus
how is peri-orbital eczema treated?
penicillin
what is lumpy wool caused by?
Dermatophillus congolesi
what is the main risk factor for Dermatophillus congolesi?
wet conditions after shearing in thin wooled breeds
what are the clinical signs of Dermatophillus congolesi?
crusty lesions on back and pruritus
(risk of fly strike)
how can Dermatophillus congolesi be treated?
penicillin (3-5 day)
what causes caseous lymphadenitis?
Corynebacterium pseudotuberculosis
what is the main site caseous lymphadenitis is found?
external lymph nodes around head (parotid, submandibular…)
how can caseous lymphadenitis be treated?
no effective treated (cull)
how is CLA diagnosed?
culture
what is a possible cause of abnormal wool fibres in lambs?
border disease (hairy shakers)
copper deficiency in growing lambs
what are the main tick borne diseases of sheep?
tick borne fever
tick pyaemia
looping ill
Q fever (Coxiella burnetti)
what causes tick borne fever?
Anaplasma phagocytophilia
what is the pathogenesis of tick borne fever?
profound immunosuppression (allows other infections)
fever causes infertility and abortions
can sheep get immunity against tick borne fever?
yes - new lambs and bought in stock more susceptible
what is the main signs of tick pyaemia?
polyarthritis and joint ill
spinal abscesses
what is the causative agent of tick pyaemia?
Staphylococcus aureus
what tick borne disease has a vaccine?
louping ill
what drugs are available to protect against ticks?
organophosphate dips (diazinon)
synthetic pyrethroid pour ons
