Photosensitisation in livestock

Page last updated: Friday, 23 March 2018 - 11:03am

Please note: This content may be out of date and is currently under review.

How can I treat photosensitisation?

Remove affected livestock from the toxic plant and provide shade. Housing is preferred for shade cover, rather than trees. Affected livestock will need protection from sunlight for at least seven days.

With primary photosensitisation, if detected early animals should recover within 4–5 days. If skin lesions are more severe, recovery will take a little longer.

With secondary photosensitisation, do not feed green or high-protein feeds. Provide only good quality hay with limited amounts of grain. Recovery may take 4–6 weeks, and during this time the affected group should not be stressed by activities such as droving, shearing or transport, nor should they be sold for slaughter as residual jaundice may result in carcass condemnations.

During recovery, monitor affected stock for infection and flystrike. Seek veterinary advice for treatment of severely affected animals. Consider euthanasia in livestock with extensive tissue damage.

How can I prevent photosensitisation?

Some plants implicated in photosensitisation are considered weeds or are undesirable for livestock feed. Avoid grazing paddocks in which these plants make up more than 30–40% of the available ground cover, and control weeds to improve the nutritional value of these paddocks. Where crops, crop stubbles or pastures that may occasionally cause photosensitisation are grazed, monitor the animals closely for early signs of this disease, and if they are seen, remove stock immediately.

How can a veterinarian help?

A veterinarian can help by correctly diagnosing the condition and ruling out any of the diseases that may show similar signs to photosensitisation. They can also provide advice on appropriate treatment, especially of severely affected livestock.

Exotic and common diseases that look like photosensitisation

Some exotic and some common diseases have signs that resemble photosensitisation.

Other diseases that photosensitisation can resemble
Disease Comments

Known as lumpy wool or dermo in sheep.

Scabby mouth Identifying and controlling scabby mouth is very important where sheep are being sold for live export as some markets reject sheep with scabby mouth. Scabby mouth can be prevented by vaccination. Discuss a suitable vaccination program with your exporter and veterinarian.
Bluetongue disease (exotic to Australia) The early phases of photosensitisation can resemble bluetongue disease. Many live export trading partners restrict entry of stock from countries with bluetongue disease. Although Australia has an effective surveillance program for bluetongue virus, it is important to have a veterinarian investigate any signs in sheep that look like bluetongue disease.
Foot-and-mouth disease (exotic to Australia) Early detection of a case of foot-and-mouth disease will be critical in reducing its impact on the Australian economy. If you have sheep with sores on their mouth or feet, contact a veterinarian to investigate the cause.
Sheep pox (exotic to Australia) Affected sheep will initially have reddish lumps on their skin, being most visible in areas affected in photosensitisation. These progress to scabs and may resemble some of the signs of photosensitisation. The sheep will also have a fever and may have a cough due to pox lesions in the lung. Your veterinarian will be able to test for sheep pox as part of an investigation into photosensitisation.

DPIRD veterinary officer contacts

For more information on photosensitisation, contact your local DPIRD veterinary officer. Their contacts are listed on the Livestock biosecurity program contacts page.