Does my cow have facial eczema?

Gippsland is approaching facial eczema peak season, so it’s worth having a look at what exactly the condition is – and what it isn’t.

Facial eczema and photosensitisation are not the same thing. Facial eczema is a specific disease caused by the spores of the fungus Pithomyces chartarum that lives mainly in ryegrasses.

The fungus grows best, and hence facial eczema occurs, in late summer and autumn. I

n contrast, photosensitisation is a broader term to describe toxic damage to the skin. There are many other causes of photosensitisation only one of which is facial eczema.

So, let’s take a step back and look at what facial eczema actually is.

Animals ingest pasture along with spores that release a mycotoxin (sporidesmin). The liver is damaged by these mycotoxins and which means it cannot rid the body of waste.

Some of the waste products which build up in the blood are what cause the unpigmented skin to become sensitive to UV light.

There are several signs that could indicate an animal has facial eczema. These include diarrhoea, milk production decline, restless cows and photosensitisation which includes reddening and thickening of skin, itchiness, restlessness and lesions.

Skin lesions can lead to oozing, infections and fly strike. In severe cases animals may lose unpigmented areas of skin.

Affected animals should be kept away from sunlight and administered anti-inflammatory drugs and antihistamines for pain and inflammation.

Not all animals show skin lesions, but liver damage can still be occurring.

Damaged liver tissue does not regenerate, and death may occur later during stressful event such as calving.

Favourable conditions for Pithomyces chartarum fungus to produce spores are a combination of high night-time temperatures and periods of rain and high humidity.

This usually occurs in late summer and autumn. There is no cure for facial eczema, but it can be prevented by monitoring weather conditions, spore counts and administering zinc.

Feeding high levels of zinc prevents cell damage caused by the mycotoxin. It is important that zinc preventatives are given two to three weeks prior to the danger period.

Other causes of photosensitisation that are not facial eczema include ingestion of certain toxic plants (eg St John’s wort) and some species of ryegrass, clover, Lucerne and Brassica.

There are also other causes of liver damage, such as ingestion of blue green algae or Patterson’s curse, that cause photosensitisation.

There is also a condition called “spring eczema” which occurs in cattle grazing improved ryegrass species between August and December and is often worst in early-weaned calves.

It is not yet known what the cause of “spring eczema” is. In both facial eczema and other causes of photosensitisation, usually unpigmented skin and hairless areas are most affected.

It is important to determine whether the cause of photosensitisation and where possible and isolate animals from the cause.

This will also indicate the likelihood of liver damage and further complications.