Sheep ectoparasites Flashcards
What is another name for blowfly strike
cutaneous myiasis
When is the risk period for fly strike
between may and september
Describe the signs seen with blowfly strike
first sign is a patch of discoloured wool and agitation
pruritus
unpleasant smell
Describe the treatment of blowfly strike
application of insecticides (systhetic pyrethroids or organophophate dips)
shearing
cleaning of affected areas
topical antibiotics
NSAIDs
List some ways in which fly strike can be prevented
shearing/ dagging/ tail docking
reducing faecal soiling
organophophate dips, synthetic pyrethroids
What causes sheep scab
Psoroptes ovis
Is a mite
What is pediculosis
lice infestation
List 6 signs of pediculosis
can be asymptomatic
pruritus
excoriation
fleece damage and loss
severe infestations can result in anaemia
can look similar to scab
Describe how pediculosis be diagnosed
visual inspection
direct microscopy of hair samples
What are the treatment options for sheep lice
pour-on synthetic pyrethroid (deltamethrin or cypermethrin)
organo-phosphate dips
which sheep should be treated for sheep lice
all sheep in direct contact
When should sheep be preventatively treated for lice
the start of the winter housing period
Where do ticks spend the majority of their lifecycle
off the host
what is the most common tick of sheep
Ixodes rincus
what diseases can be spread to sheep by ticks
Louping ill
Tickbourne fever
Tick pyaemia
Describe louping ill
viral infection causing encephalomyelitis
is zoonotic
what are the symptoms of louping ill
seizures
paralysis
death
what sheep are most commonly affected by louping ill
weaned lambs
yearlings
describe how louping ill can be controlled
tick control
vaccination can play a role (but not currently avaliable)
What causes tickbourne fever
Anaplasma phagocytophilum
What is tickbourne fever
immunosuppressive disease
bacteria infects and destroys WBC causing leucopaenia
List 5 signs of tickbourne fever
pyrexia
anorexia
depression
pregnant ewes may abort
naive tups may become infertile
What will happen if a naive animal is introduced to a TBF endemic area
more severe signs
what is tick pyaemia
Staphylococcus infection of lambs often following
immunosuppression due to tickborne fever
When are lambs affected by tick pyaemia
2-12 weeks of age
what does tick pyaemia cause
abscesses develop throughout the body often in joints, tendons, muscle and brain
what signs may lambs with tick pyaemia display
severe lameness
paralysis of backend
death
List 3 host controls that can be carried out for ticks in sheep
avoid buying naive animals
synthetic pyrethroids (deltamethrin and cypermethrin)
organophosphate dips
what are the advantaes of synthetic pyrethroids
better operator safety
longer protection
what is the disadvantage of synthetic pyrethroids
no immediate kill
what are the advantages of organophosphates
protect against more parasites
immediate kill
what is a disadvantage of organophosphates
toxic to humans
List 3 ways ticks can be controlled in the environment
expose lambs to tick prone pastures in early spring when have some passive protection
avoid tick prone pastures if possible
drainage and scrub clearance of pasture
where is sheep scab notifiable
scotland
Is psoroptes ovis (sheep scab) viable off the host
yes- for 17 days
when is sheep scab prevalent
winter
lots of contact
Describe how sheep scab can be diagnosed
skin scrabe
blood coproantigen ELISA (early diagnosis)
Describe how sheep scab can be treated
organophosphate plunge dipping (diazinon)
Macrocyclic lactone injections- moxidectin (1% or 2%), doramectin, ivermectin
What is the advantage of 2% moxidectin against sheep scab
last longer
what is a problem with 1% moxidectin against sheep scab
will react if sheep ever been given footvax
what is the problem with moxidectin
resistance
how long does moxidectin provide protection
28days residual protection
how long does doramectin provide protection
14 days residual protection
what residual protection does ivermectin have
no residual protection
what is the ivermectin protocol to treat sheep scab
two injections 7 days apart
List 5 challenges of sheep scab control
safety of chemical control measures
resistance of mites to MLs
Sub-clinical infestations
biosecurity with neighbors and common grazing
farmer motivation- under-reporting/ fatalistic view of scab control
Describe how sheep scab can be controlled
quarantine to avoid bringing in
OP dipping is only consistently reliable way to prevent scab
serology to dectect within 2 weeks of infestation
How can blowfly strike cause toxaemia and death
tocins released by damaged tissues and ammonia secreted by the maggots are absorbed through lesions into the sheep’s bloodstream
