3.1.4: Farm animal dermatology Flashcards
Where are Chorioptes mites generally found?
- On and around the tail head
- Cases are generally self-limiting
What is the causative agent of sheep scab?
Psoroptes ovis (mite)
Clinical signs of biting lice
- Decreased BCS/ DLWG -> too busy itching to eat
- Damaged skins/ fleece damage and loss
- Pruritus
- Excoriation
- Severe infestations can result in anaemia
- Biting lice can look similar to sheep scab but sheep don’t itch as much as they do with scab
- May be asymptomatic
Lice in cattle
Bovicola bovis
* Commonest
* Chewing louse
* Found on head
Haemtopinnus eurysternus
* Sucking louse
* Found around the horns
Linognathus vituli
* Sucking louse
* Found around the head area
Images: hair loss, skin is not too erythematous
True/false: lice are very common and a concern for mixed-species farms.
False
* Lice are very common!
* However they are species-specific so not a concern for mixed species.
* Lice cannot live off the host. They are typically worst in winter when cows have thick coats. Sheep-shearing in summer decreases the population by 30-50%.
Diagnosis of lice
- Visual inspection - can be seen with the naked eye
- Direct microscopy of hair samples
How can you treat mites in cattle?
Options
* Pour-on synthetic pyrethroid e.g. deltamethrin - kills everything
* Pour-on group 3-ML anthelmintics e.g. ivermectin, doramectin, eprinomectin -> kills everything
* Injectable group 3-ML anthelmintics e.g. ivermectin, doramectin, eprinomectin -> removes all suckling lice and >98% biting lice
All cattle must be treated - treat at start of winter housing period.
Consider the impact on GI parasite resistance with these different options.
Deltamethrin is
a) a synthetic pyrethroid
b) a group 3-ML anthelmintic
c) a group 2-LV anthelmintic
a) a synthetic pyrethroid
Ivermectin, doramectin and epinomectin are all examples of:
a) Synthetic pyrethroids
b) Group 1-BZ anthelmintics
c) Group 2-LV anthelmintics
d) Group 3-ML anthelmintics
d) Group 3-ML anthelmintics
What options do you have for treating lice in sheep?
Options
* Pour-on synthetic pyrethroid e.g. deltamethrin, cypermethrin -> kills biting lice
* Organophosphate dips -> kills everything including humans so take care to ensure correct usage and PPE
Flies can act as vectors for which bacterial ocular disease in cattle? What is the causative agent?
Infectious bovine keratoconjunctivitis (IBK)
a.k.a. Pinkeye disease
* Causative agent = Moraxella bovis
* Vector: face fly, feeds on tears and rapidly spreads throughout herd
Clinical signs of IBK
- Corneal ulcers
- Oedema
- Lacrimation
- Opacity
- Epiphora
Treatment and control of IBK
- Antibiotics (oxytetracycline or penicillin): IM injection is equally as effective as subconjunctival
- NSAIDs (meloxicam)- very painful!
Control
* Fly control e.g. fly tags/ pour-on synthetic pyrethroids e.g. permethrin -> lasts for several months
What are Onchocerca and what are the clinical signs of infection? How do you treat this?
Onchocerca: thin, white worms found in the eye of cattle.
* Vectors: blackfly, Culicoides
* Causes ocular infection: acute oedematous necrosis to chronic granulomatous changes, marked fibrosis and mineralisation
* Treatment: systemic ivermectin + NSAIDs
* Not currently present in UK
Species of blowfly
- Lucilia spp
- Calliphora spp
- Phormia spp.
Risk factors for blowfly strike
- Climatic conditions (warm and wet)
- Breed susceptibility (heavy dense fleece)
- Wet or dirty fleece -> easy for larvae to survive (dirty fleece may be caused by PGE)
Clinical signs of blowfly strike
- Agitated sheep with area of discoloured wool
- If you itch the area, sheep nibbles in the air
Treatment of blowfly strike
- Insecticides: synthetic pyrethroids and organophosphates
- Animals can be very sick -> electrolytes, propylene glycol, 3-5 days broad spectrum antibiotics (e.g. penicillin + something else)
- NSAIDs (meloxicam)
Prevention of blowfly strike
- Long-acting synthetic pyrethroids and IGRs
- Non-chemical prevention: genetic selection for wool-shedding breeds, early shearing, dagging, good endoparasite control
Causative agent of warble fly
- Hypoderma bovis
- Hypoderma lineatum
Warble fly has been eradicated from the UK and all imported cattle must be treated on arrival. Still notifiable in Scotland.
Clinical signs of warble fly
- Gadding behaviour: flies harass cattle, causing them to become restless, charge around, become depressed -> reduced production and growth
- Ectopic migration and paralysis -> risk if wrong treatment used! Larvae migrate to the wrong place and damage nerves.
- Downgrade of hides caused by larvae
- Reduced reproduction -> larvae emerge in spring -> cow will not stand to be mounted as painful
Treatment of warble fly
- Organophosphates 98% effective in autumn, less effective in spring
Sarcoptes spp.
Demodex spp.
Chorioptes spp.
Psoroptes spp.
Sheep scab
Causative agent: Psoroptes ovis
Legal requirement to treat or slaughter in UK. Notifiable in Scotland.
Psoroptes ovis
Causative agent of sheep scab
True/false: Psoroptes ovis can survive off the host.
True
Mite can survive off the host for 15 days
Clinical signs of sheep scab
- Extreme pruritus
- Rubbing
- Head tossing
- Wool loss
- Wounds
- Rapid loss of condition
- May see seizures
Diagnosis of sheep scab
- Mites just visible to naked eye
- Skin scrape around edge of lesion -> look on the leading edge (caudally or ventrally) because lesion starts on the shoulder
- Blood coproantigen ELISA -> good for early disease (2 weeks post infection can be detected); can sample a portion of the flock and see if present
Treatment options for sheep scab
- Organophosphate plunge dipping (diazinon) -> need correct PPE and correctly dip sheep. The only way if you have ML-resistance.
- ML injections but this does not provide much residual protection (doramectin/moxidectin provides some, ivermectin none) -> there is some resistance
Control challenges of sheep scab
Control of sheep scab
- Quarantine treatment to avoid bringing in scab
- OP dipping
- Serology to detect infection early
Chorioptic mange (a surface mite)
Consequences of tick infestations
- Spread of infectious disease
- Poor BCS
- Weight loss/ reduced milk yields
- Hide/ fleece damage
- Intense irritation -> associated behavioural issues
- Lesions and opportunistic bacterial infections
- Prolonged infestation -> small granuloma formation due to retention of mouth parts of salivary secretions
Tick control
- Avoid buying in naïve animals
- Pour on synthetic pyrethroids e.g. deltamethin, cypermethrin OR organophosphate dips
- Avoid tick-borne pastures if possible/ pasture improvement and scrub clearance
Causative agent of tickborne fever
Anaplasma phagocytophilum (a rickettsia)
What is tick pyaemia?
- Lambs 2-12 weeks old
- La,bs are infected by anaplasmosis and this causes immuno-suppression
- There is then opportunistic by S. aureus through bite wounds/ umbilicus -> leads to abscesses
- Can look like joint ill but tick pyaemia occurs at weeks (not days) old
Clinical signs of Babesia in cattle
Babesia = redwater fever. Spread by ticks.
* Pyrexia
* Severe haemolytic anaemia -> haemoglobinuria
* Potentially death
Types of photosensitisation
- Direct photosensitisation: defect in metabolism of RBCs or plants e.g. St John’s wort
- Secondary photosensitisation: animals will liver damage that means they do not breakdown chlorophyll adequately.
- Local photosensitivity: reaction to the sap of some plants.
Treatment of photosensitisation
- NSAIDs
- Removal to cool shaded housing
- Fly control
- Treatment of liver failure
