Stock introduction and quarantine policies

A good biosecurity plan must assume that introduced sheep are infested with lice regardless of their history or whether there are no lice or signs of lice. Your decision on how to manage the introduced sheep will be a personal risk management choice. This is based on

  • The number of sheep being introduced, how many this is in relation to the existing flock size, the cost of their treatment and impact of out-of-season shearing compared with the cost and impact of treating the whole flock if lice spread to them.
  • Your ability to properly quarantine the introduced sheep both until they can be treated off-shears or in short wool and for a period afterwards, while the treatment takes affect. This will depend on the product used and application method; see the label for the recommended time, but it can be many weeks.

Management options for introduced sheep

There are four management options to keep your flock lice free in the long term. You can use the LiceBoss Treatment Guide (available here in late June 2015) to help choose an option to suit your situation.

The options are presented below in descending order of biosecurity rigour. Additional notes for the options are further below.
 

Option 1: Shear and treat immediately*

  1. Shear regardless of when sheep were last shorn.
  2. Apply an off-shears/short wool treatment.
  3. Quarantine for the required period after treatment, as shown on the product label.

Note: This option may produce high chemical residues in the shorn wool if the sheep had already been treated off-shears or in short wool.
This option is rarely cost-effective. See below for situations it may suit and how to assess the cost.

Option 2: Treat short wool sheep immediately

  1. Sheep introduced with less than 6 weeks wool: apply a short wool treatment (choose a product suitable for the time since shearing).
  2. Quarantine for the required period after treatment, as shown on the product label.

Note: this option may produce high chemical residues in the shorn wool if the sheep had already been treated off-shears or in short wool.
Use another option for sheep with longer than 6 weeks wool.

Option 3: Quarantine and decide treatment at the next shearing

  1. Quarantine introduced sheep and check for lice when they are next being shorn.
  2. If lice or signs of lice become evident by shearing OR the sheep were introduced less than 6 months before shearing, then apply an off-shears/short wool treatment at shearing to the introduced mob and continue quarantine for the required period after treatment, as shown on the product label.
  3. If no lice or signs of lice are present at shearing AND the sheep were introduced at least 6 months before shearing, do not treat.

Option 4: No quarantine and decide treatment at the next shearing

  1. Do not quarantine introduced sheep—if lice are present, this will allow them to spread to your flock—and check for lice when they are next being shorn.
  2. If lice or signs of lice become evident by shearing OR the sheep were introduced less than 6 months before shearing, then apply an off-shears/short wool treatment at shearing to your entire flock.
  3. If no lice or signs of lice are present at shearing AND the sheep were introduced at least 6 months before shearing, do not treat.

All options assume that you apply any off-shears/short wool treatments according to label instructions (including within the correct time since shearing) to all sheep in the mob or flock and maintain the necessary period of isolation after treatment as directed by the product label.

*Option 1, despite being the best option for biosecurity, is rarely cost effective. It best suits these situations:

  • When the introductions are few in number, such as purchased rams or strays collected from the neighbour.
  • When the consequences of lice spreading to your existing flock are more serious than just the cost of fleece damage and treating the flock next shearing, for example, a stud breeder may have a reputation to protect.
  • When the introduced sheep are obviously lousy and your ability to isolate them from the existing flock is poor.
  • When your sheep have been lice-free for many years and you want to completely remove any chance of lice introduction from external sources.

To weigh up Option 1 for your situation:

  • Use the LiceBoss Long Wool Tool to calculate estimated cost of fleece damage from lice in the introduced sheep, should they turn out to have lice.
  • Use the LiceBoss Long Wool Tool again to calculate possible cost of fleece damage in your existing flock, should lice spread to them.
  • Use the LiceBoss Products Tool to find the cost of lice treatments.
  • Ask your wool broker for the discount you would suffer on premature shorn wool, both if the introduced sheep were shorn now and also if they are prem. shorn again later to line their shearing up with your main flock.
  • Compare the cost from one or two prem. shearings and a treatment to the introduced sheep versus the cost of fleece damage to the introduced sheep (and possibly some or all of your flock), plus subsequent treatment of the whole flock.

When estimating the cost of fleece damage using the Long Wool Tool you will need to make assumptions about the level of rubbing and when it might appear, both in the introduced sheep (if no rubbing is currently evident) and in your existing flock (which could vary considerably). The extent of rubbing that will appear in your flock, if lice spread to them, will depend on how lousy the introduced sheep are, how many and which of the introduced sheep are exposed to your existing sheep (as they will have different levels of infestation) and when the contact takes place before the existing sheep are shorn. You might consider a number of scenarios, such as a worst-case scenario where the level of rubbing is high well in advance of shearing, and also a moderate and a light level of rubbing in your main flock, and estimate how likely these scenarios are. Weigh these up against the costs associated with an early shearing and treatment.

In options 3 and 4, also check for lice each 2 months leading to shearing. If lice become apparent before the next shearing, the introduced sheep and any they they have mixed with may require an interim long wool treatment to suppress lice. Consult the Long Wool Tool to see if this is warranted. As long wool treatments cannot eradicate lice, an off-shears/short wool treatment will also be required at next shearing. Different long wool treatments are registered for different lengths of wool and for different times until shearing. Consult the Products Tool or product label to choose a suitable product.