The Department of Primary Industries and Regional Development (DPIRD) is urging sheep producers to closely monitor stock after receiving an increase in reports and enquiries relating to photosensitisation in sheep.
Photosensitisation is a condition that causes the skin to become highly sensitive to sunlight, resulting in inflammation, swelling, irritation and skin damage. Sheep with unpigmented skin, recently shorn sheep and young animals are particularly susceptible.
DPIRD Field Veterinary Officer Izzy Drage said producers should be vigilant for signs of the condition, particularly while sheep were grazing green feed and rapidly growing pastures.
"DPIRD has received a number of reports and enquiries from producers concerned about photosensitisation in their sheep in recent weeks," Dr Drage said.
"While cases can vary in severity, early recognition and management are critical to reducing animal welfare impacts and production losses."
Photosensitisation can develop either directly from eating certain plants, known as primary photosensitisation, or following liver damage caused by plant or fungal toxins, known as secondary photosensitisation.
Plants associated with photosensitisation include St John's wort, Paterson's curse, heliotrope and caltrop, while cases are also sometimes seen in sheep grazing crops and pastures such as canola, lucerne and clover-dominant feed.
Dr Drage said secondary photosensitisation was the form most commonly seen in Australian livestock.
“Common signs include swelling of the ears, eyelids, lips and muzzle, drooping ears, reddening of the skin, discharge from the eyes, and sheep seeking shade or showing signs of irritation,” she said.
“In more severe cases, affected skin may become scabby, crack or peel.
"Conditions at this time of year can favour the development of photosensitisation, and producers should inspect mobs regularly, particularly recently shorn sheep and animals with unpigmented skin.
"If you suspect photosensitisation, remove affected animals from the source paddock immediately and provide protection from direct sunlight. Housing animals under cover is preferable to relying solely on natural shade."
Affected livestock should be monitored for infection and flystrike, and veterinary advice should be sought for severely affected animals.
Dr Drage said investigations of photosensitisation cases also contributed to Western Australia's livestock disease surveillance system.
"Some reportable and exotic diseases can initially resemble photosensitisation, so veterinary investigations play an important role in protecting our livestock industries and supporting market access," she said.
Producers concerned about photosensitisation should contact their private veterinarian or local DPIRD field veterinary officer.
