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This article was published in 2000
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Chemical Dermatitis in Sheep
Tony Morton DV Wagga Wagga
On 21.12.99 I visited a Temora property to investigate a complaint of severe widespread dermatitis in sheep following off shears treatment with Clout S (Deltamethrin 10g/L).
A total of 1360 merino sheep (ewes, wethers & weaners) had been shorn and 30-40% were estimated at this initial inspection to have dermatitis (a subsequent inspection revealed the situation was far worse).
The owner has been regularly using Clout S without any problems. Two drums of Clout S had been used, the first had been used in 1998 without problems being noted & was used for most of the 1999 shearing. The second drum (bn vo1989/1) was used for the last day of shearing. Both drums were associated with dermatitis. The weather was relatively mild and shearing was interrupted by rain. The owner states that between runs the backpack containing the Clout S was put in the shade.
The dose rate used was 15 mls for adults & 8 mls for hoggets.
History
Shorn 19.11.99 to 29.11.99 and treated with Clout S off shears the same day they were shorn (run by run)i.e.. 4 treatments done each day. Has been using Clout S for many years without problems. Rainfall was above average both before and after shearing & caused shearing to be interrupted.
The owners records (in points)
| 06/11/99 | 38 |
| 16/11/99 | 4 |
| 22/11/99 | 175 |
| 23/11/99 | 3 |
| 08/12/99 | 60 |
| 09/12/99 | 88 |
| 17/12/99 | 79 |
| 24/12/99 | 7 |
| 26/12/99 | 157 |
| 27/12/99 | 69 |
| 28/12/99 | 57 |
| 29/12/99 | 15 |
| 27/01/00 | 65 |
There was no further rain to 21/02/99.
Clinical Signs
Dry scabs of varying size (up to the size of saucers), hard, crusted and on some cases lesions are in mid line but clout is off to one side of midline. The lesions were consistently on or near the midline.
Photographs
Lesions were recorded on 10 photographs. A copy of the photograph of the worst affected sheep is in the proceedings.
Laboratory Results
Three scabs were submitted to the EMAI. Primary culture yielded a sparse mixed growth including Dermalophilus congolensis from one swab & n.s.f. from the other two. Fungal culture was negative. No growth was obtained from a swab of Clout S.
SECOND VISIT
On 25.1.2000 the property was revisited and a mixed mob of ewes and wethers examined. Ranger Mick Adams was also present (he is a former NSW Livestock Officer S & W and former Dalgetys Wool Rep).
A detailed examination was made on one race of sheep and then a yard full of sheep inspected and lesions assessed as wool loss only, moderate lesions or severe lesions.
Observation on 1 race of sheep 25/1/2000.
| 2 yr old female | no sign |
| 2 yr old female | 8cm scab on thorax |
| 2 yr old female | 7cm wool loss only on thorax and lumbosacral area |
| 2 yr old wether | minor wool loss on withers |
| 3 yr old wether | 27cm x 16cm scab on thorax, wool loss running down shoulder, some wool loss on hips |
| 3 yr old wether | extensive (65cm) x 15cm scab formation along backline, total wool loss under scab |
| 3 yr old wether | no visual signs |
| 4 yr old wether | no visual signs |
| 2 yr old ewe | no visual signs |
| 2 yr old ewe | 4 cm diam wool loss break on tip |
| 4 yr old wether | 16cm x 8cm scab on withers (total wool loss on scab) |
| 2 yr old ewe | no visual signs |
| 3 yr old wether | dry crusting 5 cm diam lesion on rump , dry wool ; 10cm x 4cm lesion on withers |
| 4 yr old wether | no visual signs |
| 2 yr old wether | 3cm diam wool break on tip on the rump |
| 2 yr old ewe | no visual signs |
| 2 yr old ewe | no visual signs |
| 2 yr old ewe | 50cm x 17cm (widest point at T/L junction) lesion down backline |
| 3 yr old wether | no visual signs |
| 2 yr old ewe | no visual signs |
| 4 yr old wether | 6cm x 9cm lesion, scab sloughed off on withers |
| 4 yr old wether | 16cm x 7 cm lesion, scab sloughed off on withers |
| 4 yr old wethers long | lesion on withers running back along thorax, scabbing and wool loss 13cm x 2cm wide |
| 3 yr old wether | extensive lesions 55cm long x 10cm at widest point thick scabs on thorax Thinner scabbingon lumbar area |
| 2 yr old wether | no scabs, wool break on tip thorax and lumbar areas about 35cm |
| 2 yr old wether | normal, no visual signs |
| 2 yr old wether | no visual signs |
| 2 yr old wether | 7cm x 6cm scabbing on withers |
| 2 yr old ewe | 9cm x 7cm scab on thorax/withers, 3cm dia. Wool loss and scabbing on right rump |
| 4 yr old wether | 53cm lesion from withers to rump, widest at withers 20cm |
| 3 yr old wether | 66cm x 24cm at widest point behind shoulders. Two photocopies of photographs of this sheep are included in the proceedings. |
Yard Inspection 25.01.2000
| NORMAL | WOOL LOSS ONLY | LESIONS < 10cm x 3cm | LESIONS > 10cm x 3cm |
| MODERATE | SEVERE | ||
| 25 (34%) | 15 (20%) | 16 (22%) | 18 (24%) |
It was quite clear this was not dermatophilus but the lesions were typical of a severe chemical burn. Despite a proteinaceous exudate there was no flystrike, presumably due to the presence of pyrethroids. Skin biopsies were taken from two affected sheep, affected and apparently normal skin was taken. EMAI reported (mn00/0916) "consistent with a severe chemical dermatitis". A sample of Clout S was taken & forwarded to Coopers Animal Health. The full laboratory report stated:
HISTOPATHOLOGY — 1 February 2000
Skin: Amended 4 February, 2000 following second opinion. The two sections of skin had a segmental alopecia, acanthosis and hyperkeratosis. There was a sharp transition between affected skin and skin with relatively unaffected epidermis and ednexal elements. In one section of skin there were several intraepidermal pustules containing necrotic cellular debris and neutrophils, mostly in the stratum corneum and associated with localised parakertosis. In the other section of skin there were localised segments of crusting with necrotic cellular debris and neutrophils superficially. There was loss of follicles and associated structures in affected segments of both sections of skin. There was probable necrosis of a follicle at the margin of the affected skin. In others there was a complete loss of follicular epithelium with a few multinucleate giant cells in the remaining spaces. Rod-shaped bacteria were present diffusely or in clusters extending along remnant follicular spaces, in some areas of dermis and in the hypodermis. The dermis had marked fibrosis accompanied by a mild, diffuse increase in mostly mononuclear cells.
Morphological diagnosis:
1. Segmental epidermal alopecia, acanthosis and hyperkeratosis.
2. Necrotising folliculitis.
3. Epidermal pustules and crusting.
4. Dermal fibrosis.
Comment
There appears to have been reepithelialisation from the edges of the lesion following full-thickness necrosis of the epidermis and loss of follicles. Bacteria have extended along remnant follicular spaces. Consistent with a severe chemical dermatitis.
Special stain — periodic acid-Schiff: No fungal elements were detected in sections of skin.
Gram stain: The rod shaped bacteria in the dermis and hypodermis were Gram positive.
In an attempt to see if the condition could be replicated five adult sheep with skin lesions were shorn along each side of the backline and 15 m1s of Clout S applied to the left hand side, the shorn right hand side was not treated.
THIRD VISIT
On 21/02/2000 Mick Adams and myself inspected the five trial sheep.
One sheep had a small lesion in the treated area typical of previous cases. The lesion was a small scab on the left shoulder which lifted off leaving a raw area approximately 1 cm diameter. The area between this lesion and the severely affected original backline lesion appeared normal. A biopsy was taken and labelled no. 1, a biopsy was taken of untreated apparently normal skin from the right hand side. The possibility that this lesion originated from the original midline lesion was considered however careful examination revealed no evidence of inflammation or wool break linking the two lesions. The original skin damage was permanent and wool growth had ceased. Three photocopies of photographs are included in the proceedings.
A second sheep had wool that could easily be plucked ventral to the left hand treated area while the wool was much stronger on the right hand control shorn strip. Biopsies were taken from both sides.
The remaining three sheep were apparently normal.
The owner commented that the hoggets which only received 8 mls of Clout S are showing less severe symptoms than the adults that received 15 m1s.
The laboratory report MN00/2028 stated:
HISTOPATHOLOGY
Sheep 1 (slides 1 & 2)
The hairless lesion on the withers was a largely healed ulcerated area with replacement of the epidermis and most of the dermis. Nearly all adnexal glands and hair follicles were destroyed and replaced by dermis without glands and a keratotic epidermis. There is a mild residual granolomatous dermatitis (presumably cleaning up the remnants of dermal debris). The lesion is consistent with a resolving severe focal necrotising dermatitis. Why it was restricted to a small circular scabby lesion and not the much larger treated area is not known.
Sheep 2 (slides 3 & 4)
There are not obvious histopathological changes on the treated LHS skin biopsy compared to the control biopsy on the untreated RHS. The observation of weak wool fibres suggests either a follicle or fibre problem which is not visible microscopically.
COMMENT
Dr Alistair Murdoch of Schering Plough advises me that:- Results from analysis of Clout S samples collected 25/01/00 and sent to Coopers Animal Health (Schering Plough) 27/01/00 revealed no abnormalities.
The history, clinical findings, histopathology and trial work with five sheep all support a diagnosis of chemical dermatitis due to Clout S.
Clinically & histopathologically wool loss is permanent along the backline of many sheep. This will have enormous long term implications:
1. loss of production
2. handling fleeces at shearing will be a nightmare
3. fleece wool downgraded to pieces & locks
4. C.F.A. wethers will not be suitable as boat wethers thus reducing sale price
5. C.F.A. ewes may suffer marketplace discrimination
6. rain may penetrate along backline leading to fleecerot and flystrike.
It's hard to explain why such an adverse reaction should occur and a large range of possibilities spring to mind. 1. Fraud: I've known the owner for 5 years and I have been impressed by his forthright and honest manner. I don't see this as a realistic possibility.
2. Malicious contamination of Clout S: seems unlikely. Analysis by Schering Plough should have revealed if this possible.
3. Manufacturing error: seems unlikely with two drums purchased one year apart. Analysis by Schering Plough should have revealed such a problem.
4. Clout too hot: the owner says the pack was not left in the sun between runs but even if it was late November was not a period of exceptionally hot weather. Shearing was interrupted by heavy rain 175 points 22/11/99.
5. Heavy rain post shearing: significant rain 8/12/99 60 points, 9/12/99 88 points, 17/12/99 79 points and 26/12/ 157 points and 27/12/99 69 points, 28/12/99 57 points is unusual in this district. On the one hand perhaps it should dilute the chemical, on the other hand perhaps high fleece moisture levels have played a role in this problem.
6. "It happens". Prior to presenting this talk I showed photographs of the case to Johann Schroeder Business Unit Manager Livestock Bayer Australia. He said that such problems sporadically occur with backline products and are rarely repeatable. It's uncertain if the problem is due to the active ingredient or other solvents/carriers in the formulation.
Discussion
1. Alistair Murdoch
As the veterinary spokesperson for Coopers Animal Health I have reviewed our adverse event reporting data since the release of Clout S. In this historical review we have not experienced or reported any such previous events and view this unfortunate clinical event as an unique episode. The clinical history, QA analysis of the Clout S, histopathology and the final clinical outcome have not assisted Coopers in determining a primary causative agent or event in this matter. Further research in our global database has also failed to provide further information on this event.
2. Ian Harradine DV Grafton:- commented that a similar lesion has been seen in calves following "Bayticol" (flumethrin) administration. One calf with extreme hair loss had a biopsy that suggested an allergic reaction. Other cases have been clinically consistent with a chemical dermatitis or sunburn. Farmers often treat calves with Bayticol as soon as they find them after birth to prevent paralysis tick deaths. The liquid may part the hair leaving a thin line of skin that could possibly be sunburnt.
3. Christine Haylock DV Cooma has seen skin reactions with Zapp in poll dorset sheep and the owner later reported a reaction to Magnum.
4. Keith Hart DV Moss Vale recalls chemical dermatitis in sheep in Braidwood RLPB as a result of the use of the original backline product Clout. Very close shearing of British breed sheep and hot clout were the likely causes of this problem.
5. On 3.3.99 L. Rast DV Gundagai saw a similar problem at Cootamundra with 50 ex 150 adult merino ewes affected. The notes made by Luzia record that the sheep were shorn at the end of December and Clout S applied on the evening of shearing. Owner noticed sores on backlinc about 3-4 weeks ago. Full skin thickness ulcerations along backline, more severe between shoulder blades, scabs cover wounds. New skin forming around edges.
CASE FOLLOW UP
On 16.10.00 the owner rang me shortly after shearing had finished. From 1,200 sheep treated with Clout S in November 1999 between 150 & 160 head carried a permanent scar. An estimated 50-60 sheep without permanent scarring also had spots as large as a 10c coin of bleached wool along the backline. Not surprisingly there were many fleeces which broke down the back and in many cases deterioration of the wool extended down the back of the shoulder. There were a total of three bales of tender wool much of it with a tip break. Laboratory wool test results are not available.