Summer is the season for shearing in some areas of Australia and shearing is the best time to attempt eradication of body lice from a flock. Sheep treated immediately off-shears controls the lice when the population is naturally at its lowest and is very exposed to chemical treatment. To have the best chance of eradication, it is critical that all sheep are treated at the same time so that no carriers are left to reinfest the entire flock.
Body lice (Bovicola ovis) feed on dead skin and secretions found on the skin surface of sheep. They do not eat the wool directly and they do not suck blood. Infestations cause irritation and thickening of the skin which causes sheep to rub, lick and chew. This leads to damage of the fleece, including discolouration, reduced yield, and reduced staple length.
Lice have a significant economic impact on the sheep industry in Australia due to costs associated with lost production and treatment. Estimated production losses in lousy Merino wool ranges from $10.51 to $11.94 per head1.
Lice typically cause most problems during the cooler months of the year, peaking in numbers during late winter and early spring. Severe infestations can, however, occur at any time of the year, particularly during drought when animals are in poor condition.
Once a lice infestation has established within a flock it can be difficult to control and even more difficult to eradicate. Development of an integrated management program is key, firstly to conduct strategic treatments to eradicate the current infestation and secondly, implementation of a lice biosecurity plan2 to prevent new infestations.
A great opportunity to eradicate lice is by using off-shears backline treatments, ideally within 24 hours of shearing. Treatments applied at other times may reduce the lice population but will not eradicate the infestation.
There are many backline lousicide treatments available and it is important to keep the following factors in mind when choosing a treatment: no known resistance to the active ingredients, duration of persistent activity, degree of water fastness and ease of application. For best effect, ensure every sheep is mustered and receives an accurate treatment according to label directions.
Once eradication treatments have been applied it is time to implement an effective lice biosecurity plan to prevent reintroductions onto the property. Stray and purchased sheep are the two most likely sources, therefore, a good biosecurity plan should take into consideration the surveillance and maintenance of boundary fences, as well as a quarantine and treatment protocol for new stock acquisitions.
If you’re about to start shearing in the coming months, monitor your flock for lice and prepare an eradication plan accordingly. FENNEC® Pour-On for Sheep is an ideal choice for an off-shears backline treatment due to its combination of two actives with no known lice resistance, 5-weeks protection from re-infestation* and the convenience of a pour-on.
If you require further assistance, contact your animal health advisor about the right treatment and timing in your area.