By Linda Searle, District Veterinarian
Farmers are being warned to be on the lookout for photosensitisation in livestock.
Photosensitisation can be seen in cattle or sheep and manifests as areas of lightly pigmented skin being badly sunburnt to the point of blistering and peeling.
In cattle this usually occurs as reddening and pain of the udder and skin disturbances along the midline of the back in areas of light pigmentation.
In sheep the disease is often more severe and usually occurs in the non-wooled areas, particularly around the lips and ears, causing ‘big head’, and the coronet bands on the feet. Severely affected sheep may die from the condition (see photo, right, courtesy Amy Shergold).
Photosensitisation may be defined as either primary or secondary. Lately we have seen issues with the secondary type, which involves damage to the liver. The most common causes involve stock eating young hairy panic, cathead or heliotrope.
Primary photosensitisation can also be caused by the ingestion of toxic plants but this occurs without liver damage. This is most commonly seen with livestock consuming St John’s wort.
Farmers are advised to keep a close eye on livestock, especially looking for signs of swelling or sunburn on the noses and ears of sheep and sunburn along the backs of cattle. Early diagnosis and intervention is essential. Most animals will recover quickly if the condition is not too severe or progressed. Animals should be provided with good shade such as a shed, taken off green pasture and fed hay. What starts as one or two sheep on one day can grow to 30-40% of the flock overnight, so removing stock from affected paddocks as soon as signs are detected is important. More severe cases will require veterinary attention and some stock may need to be euthanised.
Farmers are advised to not allow stock, especially young stock, to graze on pastures where there is a large amount of hairy panic, heliotrope or cathead growing.
If you would like more information on photosensitization, or you have seen this condition in your animals please, call your district veterinarian on 6051 2200 or 03 5881 1055.
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