Novartis Trial – Eradication of Lice
Results:
No lice were found at any post treatment inspection. Furthermore no animals displaying symptoms of lice, or having louse affected wool, were found at shearing 12 months later.
Object:
To test the efficacy of a mixture of Seraphos 500 (propetamphos) and Zenith (diflubenzuron) against the sheep biting louse, Bovicola ovis, when applied off shears to normal comb/machine shorn merino ewes, using an automatic jetting race (Electrodip).
Trial Location:
Property of Mr John Downard
Pukewaikaha Station
R.D. Ongarue
King Country NZ
Trial Period:
5/5/1999 - 3/5/2000
Farm Details:
Area: 554 ha (500 effective) flat to rolling medium hill country
Average Annual Rainfall: 1500mm
Stock:
1850 crossbred ewes plus replacements
800 merino ewes plus replacements (18.0 - 19.0 micron)
195 beef cows
150 fattening cattle
Background:
Merinos have been farmed on the trial property since 1984, beginning with 100 ewes and building up to the current flock of 800 ewes plus replacements. The merino flock is run separately from the crossbreeds. Shearing is carried out in the autumn, usually the first week of May, with all animals machine shorn using a normal comb.
Infestations of the sheep biting louse, Bovicola ovis, have consistently caused problems in the merino flock. Louse control in the past has been based around the animals receiving a synthetic pyrethroid pour-on treatment immediately off-shears. Additional control of lice was thought to be achieved by up to 4 treatments of an organophosphate, (Topclip, Diazinon 40) applied over the late Spring/Summer for flystrike prevention. These treatments were applied by an automatic jetting race ( Electrodip). Despite this high number of chemical treatments, in most years between 10 -20% of the flock exhibited obvious signs of lousiness at around 8 months following shearing, often necessitating a long wool synthetic pyrethroid treatment.
In order to gain more effective louse control and hopefully avoid the pesticide residues caused by long wool emergency treatments, an alternative treatment strategy was sought in Autumn 1999.
After consultation with Novartis Animal Health, it was decided to use a combination of an effective knockdown product along with a long acting louse effective I.G.R. through the Electrodip.
The use of a combination approach was made on the basis that the knockdown product would remove most of the adult lice that survive shearing. The louse effective I.G.R. would provide residual long term control of any juvenile lice that hatch from eggs remaining after shearing, or from eggs laid by adults surviving shearing and the knockdown treatment. The knockdown treatment selected was an organophosphate based product, "Seraphos 500" (propetamphos) and the I.G.R., "Zenith" (diflubenzuron).
Application.
20 animals from a mob of 323 mixed age merino ewes displaying obvious symptoms of lousiness, such as rubbed out flanks and matted fleeces, were inspected for lice. Total lice counts for each animal were reached by counting the lice in 3 x 10cm partings of the wool at 14 sites around the animal’s body (total of 42 partings per animal). Where the number of lice in one area was greater than 50, a score of 50+ was entered for that site.
These sites were chest, neck, lower and upper shoulder, withers, flank and hindquarters on each side of the animal's body. Each animal was identified with a double sided, numbered Allflex eartag and returned to the mob immediately prior to shearing.
All animals in this mob were then machine shorn using a normal comb, leaving behind approximately 2-12mm of wool. It was noted that the shearing in the neck /brisket region in particular was very variable, with patches of wool up to 12-25 mm long remaining.
Following shearing all animals were treated with the previously described mixture of Seraphos 500 and Zenith, applied through a modified Electrodip. An untreated control group was not included in this study.
Seraphos 500 batchJ01
Zenith Batch 07991
The Seraphos 500 was diluted at 1:333 (=480 ppm propetamphos) and the Zenith at 1:666 (= 375 ppm diflubenzuron). Both products mixed readily and appeared compatible in the wash. The Electrodip used to apply treatments had a total of 17 nozzles arranged to give the following spray pattern:
3 nozzles operating from above the animal, set to deliver wash along the back from the ears to the breech.
5 nozzles operating on each side, 10 nozzles in total, set to apply wash along the flanks.
2 nozzles operating from below and in front of the animal, set to treat the brisket/neck.
2 nozzles operating from below and behind the animal, which applied dip onto to the crutch/tail area. The mean volume of wash applied to each animal was 1.23 litres.
Following treatment and for the remainder of the trial period all animals were run as one mob according to normal farm practice.
Inspection
Post treatment louse inspection, following the same protocol as that described for the pre treatment counts, were carried out at 50, 93, 198, 261, 317 and 365 days post treatment. 2 sheep were not available due to death of the animal or a lost tag.
Cost of Treatment
Seraphos 500 @1:333 = 10.3 c/L
Zenith @ 1:666 = 13.5 c/L
1.23 L/ animal =29.27 cents per animal.
Electroquip note. Chemical cost have reduce markedly since this work was done in 1999
Other Ectoparasite Treatments
All animals received a treatment of Topclip 40 diluted 1:1000 (400ppm diazinon) , applied through the Electrodip, for short term flystrike control in early November 1999. A spray on formulation containing 25 g/L dicyclanil (Clik) was applied in early December 1999 for long term flystrike protection. It is worth noting that the application of the Topclip 40 through the Electrodip for flystrike prevention has not had a noticeable effect on louse populations and Clik has no efficacy against lice.
Results
No lice were found at any post treatment inspection. Furthermore no animals displaying symptoms of lice, or having louse affected wool, were found at shearing 12 months post treatment.
Summary
This study indicates that, under North Island conditions, a mixture of a knockdown product (Seraphos 500) and a louse effective I.G.R. (Zenith) can provide effective control of lice, when applied off-shears by Electrodip to autumn shorn (normal comb) merino ewes carrying light to moderate louse infestations.
Further work is required to determine if this treatment method is effective where there is likely to be a greater challenge, i.e. South Island merinos cover comb or blade shorn pre-lamb in late winter/early spring.