Sheep skin diseases Flashcards
What are the main economic and welfare problems associated with skin disease in sheep?
Pruritis
Weight loss
Fleece
What factors can help diagnose skin and wool disease?
- time of year
- part of the body affected
- how many affected
- pruritis
- visible parasites
- other clinical signs
- previous treatment tried
Contagious pustular dermatitis is also known as…?
Orf
What kind of a virus is orf?
Parapox vis - Zoonosis
Describe the lesions seen with orf
- Vesicular / proliferative scabby lesions
- Mouth/head and teats
- Lambs but can affect ewes too esp teats
- Painful
What are the impacts of orf?
- Interferes with sucking / eating
- Teat lesions – predispose to mastitis
- Poor growth
- Death
How does orf spread?
- By contact
- Damage to skin and mouth allows virus in
- Virus doesn’t survive overwinter outside
How can orf be controlled?
- Isolate clinical cases
- Disinfect equipment e.g. feeding bottles
- Care when oral dosing
- Thorough cleaning and disinfection of buildings, feed troughs, barriers
Describe the orf vaccine and its use
- Only use in infected farms
- Live vaccine
- Apply by scratching the skin in the armpit of lambs
- Don’t use indoors as it will contaminate housing
Name 3 parasitic mites that infect sheep
- Psoroptes ovis
- Chorioptes bovis
- Trombicula
Name a lice that infects sheep
Bovicola ovis
Sheep scab is caused by…?
Psoroptes ovis
How is sheep scab transmitted?
Direct contact sheep or infected scab fomites material on fencepost, vehicles etc
Allergic reaction to the mite - 6-8 weeks post infection
How do sheep with scab present?
- Pruritis
- Nibbling
- Kicking, scratching, rubbing
- Wool loss, ragged fleece, moist yellow appearance
- On flank, dorsal side or whole sheep
- Sheep stop eating, weight loss, death
Describe how to diagnose sheep scab
- Choose itchiest sheep with wool loss
- Exudative lesions
- Edge of lesion
- Wool pluck (sealed in bag)
- Skin Scrape (put in container)
Describe the appearance of psoroptes ovis mites and how you would identify them
Pointed mouth parts and bell shaped suckers on segmented pedicles
Which test can be used to diagnose sheep scab in the earlier stages?
ELISA
- Detects signs in early stages (within 2 weeks of infection)
- Good sensitivity and specificity
What must be considered when treating sheep scab?
Survives off host 17-19 days days so must consider re-infection
Must treat all sheep
What are the treatment options for sheep scab?
Dexamethosone (steroid) for severely affected sheep
Organophosphate dip – diazinon
Macrocytic lactones
Describe how to correctly administer organophosphate dips to be effective
- Dip replenishment (manufacturers instructions)
- 1 minute in dip
- DO NOT USE SHOWERS
- Do not use synthetic pyrethroid dips
Name 3 examples of macrocytic lactones that can be used for sheep scab treatment
Ivermectin
Doramectin
Moxidectin
Which macrocytic lactone cannot be administered with footvac?
Moxidectin 1%
How can sheep scab be prevented?
- Biosecurity – don’t buy in
- Observation not enough (7-8 weeks to see clinical signs)
- Treat all bought in sheep, sheep grazing away
- Double fence neighbouring stock
- Cleansing Disinfection vehicles and equipment, esp. shearers scanners
What are some of the main problems associated with scab management on farms?
- Diagnosis
- Incorrect products
- Under dosing because of weight, guns etc…
- Injection technique
- Mark when injected
- Poor dipping technique
- Re-infection from neighbour, bought in etc.
- Anthelmintic resistance
Is Bovicola ovis a chewing or sucking louse?
Chewing
Describe the features of a Bovicola ovis infection
- Small pale red brown
- Permanent parasites
- Highly host specific
- Spread via direct contact
- Chew at skin and coat broad heads feed on skin debris and wool
- Like a warm, dark environment
Which 2 factors reduce the risk of Bovicola ovis?
Shearing
Rainfall
How can Bovicola ovis be diagnosed?
Part fleece on back and flanks hind limbs several wool partings and look for clumps red brown lice
2-3 mm long so visible
How can outdoor sheep be treated for Bovicola ovis?
Shearing
Heavy Rainfall
Treat worst affected
How can indoor sheep be treated for Bovicola ovis?
- Synthetic Pyrethroid Pour ons
- Concern for resistance
- Plunge dip diazinon OP dip
At what time of year does fly strike most commonly occur?
May to October
What is the cause of fly strike?
Lucillia sericata
Describe how infection with Lucillia sericata leads to fly strike?
- Lays eggs in fleece
- Larva hatch about 12 hours later
- Proteolytic enzymes
- Mouth hooks
- Damage skin
- Attract other flies
What are the main sites affected in fly stike?
- Breech – affected around bum end
- Body
- Wounds
- Feet (foot lesions)
How may sheep affected with fly strike appear in the herd?
- Separate
- Depressed
- Toxaemia
- Dead
List the risk factors for fly strike
- Temperature: egg laying requires a temp of at least 10 degrees
- Humidity
- Rainfall
- Fleece length
- Faecal soiling
- Time of year
How is flystrike treated?
Synthetic Pyrethroid pour on – kills maggots
Deltamethrin – kills maggots
Clean wound
Supportive care - antibiotics, NSIADs, fluids, house
How can fly strike be controlled?
- Control risk factors
- Worm control
- Tail docking
- Shearing
- Prophylactic use of Insectsides
Name the head fly of sheep
Hydrotea irritans
Peri-orbital eczema is caused by which bacteria?
Staphylococcus aureus
‘Lumpy wool’ is caused by which bacterial infection?
Dermatophilus congolensi
How does lumpy wool present?
- Associated with wet conditions esp after shearing
- Thin wooled breeds
- Crusty lesions with wool loss
- Pruritic
- Confuse sheep scab
- Risk for fly strike
Caseous lymphadenitis is becoming an increasing problem in which group of sheep?
Terminal sires
What is the name of the bacteria that cause caseous lymphadenitis?
Corynebacterium pseudotuberculosis
Where in the body is affected by caseous lymphadenitis?
- Affects external & internal lymph nodes - Especially parotid LN
- Abscesses
How is caseous lymphadenitis treated?
- Antibiotic cannot penetrate
- So no effective treatment
How is caseous lymphadenitis spread?
- Close contact
- Fomites: shearing
- Respiratory spread (mediastinal LN abscess ruptures into airway)
How can CLA be controlled?
- ELISA & clinical examination before ram purchase: identify low risk animals
- Test and Cull affected animals
- Vaccine available Reduce incidence but not prevent all infections
- Biosecurity
- Hygiene of shearers, mobile dippers, mobile handling
Name two diseases/conditions that can cause abnormal wool fibres
Border disease
Copper deficiency
Name 2 tick species found in the UK
Ixodes ricinus
Dermacentaur reticulata
What is the main impact of ticks?
They are vectors for diseases
Name the agent that causes tick borne fever
Anaplasma phagocytophilia
What are the effects of tick-borne fever?
Profound Immuno-suppression
* Gateway infection
* Fever
* Rams in autumn- spermatogenesis infertility
* Ewes in autumn abortion
Which agent causes tick pyaemia?
Staphylococcus aureus
What are the effects of tick pyaemia?
Affects lambs
Polyarthritis/joint ill
Immunosuppression
Name a viral infection that is transmitted by ticks and is zoonotic
Louping ill
What are the effects of Louping ill virus?
Neurological - Non suppurative menigoencephomyelitis alitis
Varying severity inco-ordination to seizures death
How is Louping ill controlled?
Vaccine
Tick control
Grazing management
Describe the acaricide drugs that can be used to control tick borne infections
Diazinon OP plunge dip
* 3-6 weeks protection
Synthetic pyrethroids pour ons
* Varying protections 6- 12 weeks protection
