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EXTERNAL PARAS I TES
SUMMER 2014 ISSUE
LIVESTOCK MATTERS
10
Lice control
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Confirmation of diagnosis requires
professional identification of lice in the
fleece or from wool pluck samples.
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Plunge dipping in either OP or SP
dip is a very effective treatment of
lice infestations.
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Sucking lice can also be controlled
with systemic endectocide injection
(ivermectin, doramectin or moxidectin),
though this treatment is ineffective in the
treatment of chewing lice infestations.
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Application of SP pour-on or spot-on
products are also effective treatments.
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Good biosecurity, including the
presence of secure flock boundaries,
is essential to avoid introduction of
lice from bought-in or stray sheep.
Lice (Pediculosis)
Since the cessation of compulsory
dipping for sheep scab in 1989 there
has also been an increase in the
incidence of lice infestations. Both
chewing lice (Bovicola ovis) and sucking
lice (Lignonathus ovillus and Lignonathus
pedallis) are capable of causing clinical
disease in sheep during the autumn and
winter months.
Infestations with chewing lice are the
most common, causing disruption to
normal feeding patterns and self-trauma
due to the skin irritation caused by the
feeding lice. The result is wool loss and
damage, with heavy infestations being
seen more frequently in animals in poor
health or body condition score.
Since clinical signs and seasonality may
resemble those seen with sheep scab,
correct diagnosis is essential in order
to implement effective treatment and
control programmes.
Chorioptic mange
Chorioptic mange, caused by the
sheep adapted mange mite, Chorioptes
bovis, is primarily of importance as a
potential cause of poor fertility in
breeding rams. Clinical signs are caused
by a hypersensitivity reaction to the
presence of the mite, resulting in hair loss
and severe thickening, crusting and
irritation of the skin of the lower third of
the scrotum. Secondary bacterial infection
of the skin may also develop, further
elevating scrotal temperature.
Similar signs may also be seen on the
poll and/or lower limbs of affected
rams and ewes.
Chorioptic mange
control
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Confirmation of diagnosis depends
on visualisation of mites taken from
skin scrapings under a microscope.
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Treatment with injectable endectocides
is generally ineffective since these
mites feed only on skin surface debris.
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Treatment of choice is plunge dipping
(topical application of OP dip to the
scrotum of affected rams has been
used successfully in other countries.)