Facial eczema - signs, prevention & monitoring

Facial eczema is a disease in cattle (and some other grazing ruminants) caused by a toxin (sporidesmin) produced by the spores of the fungus Pithomyces chartarum growing on pasture.

The fungus typically thrives in warm, humid conditions prevalent in parts of New Zealand typically between January and May each year.  The fungus grows in the dead litter at the base of pasture. Therefore hard grazing during danger periods increases the risk of high spore intake.

Sporidesmin, when ingested by cattle, damages the liver and bile ducts.

The damaged liver cannot rid the body of wastes and a breakdown product of chlorophyll builds up in the blood causing sensitivity to sunlight, which in turn causes inflammation and peeling of the skin.

Signs of disease in grazing animals

• A drop in milk production
• Cows are restless, seeking shade
• Blisters on teats/whites of skin, may lick their udder or kick at the abdomen
• Exposed unpigmented or thin skin reddens, thickens and peels.

Not all animals affected with facial eczema show physical signs.

It is estimated that for every clinical case there will be 10 cows with subclinical disease whereby liver damage and production loss occurs but is not easy to detect. Blood tests can be used to monitor the extent of subclinical eczema.

Badly damaged liver tissue will not regenerate. Chronic wasting and/or death may occur at the time of damage or months later when the animal is under stress (e.g. calving).

Prevention

There is no cure for facial eczema so prevention is the only way of protecting animals. To be effective, preventative measures need to be in place before eczema spores are found.

• Zinc supplementation is the most common method of protection. (Fungicide sprays are another option)
• Start early – at least two to three weeks before the spore growth danger period.
• Dose the animals accurately according to the zinc product recommendations, weighing a sample of animals is a good idea.
• Fully dose cows with zinc: drenching with zinc oxide, water dosing with zinc sulphate, administering in feed or as an intra-ruminal bolus (e.g. Time Capsule, Face-Guard).
• The more control a farmer has over the amount of zinc an animal receives the more likely it is that the cows are receiving the correct daily dose. Zinc drenching and intra-ruminal bolus will, for this reason, provide more reliable protection than adding zinc sulphate to drinking water.
• Zinc is toxic in high doses; care should be taken in calculating dose rates.

Monitor

1. Spore counts – Regional counts are done by the clinic but collection of grass from your farm helps you understand the risk to your animals more accurately.
2. Zinc blood tests in a sample of cows can ensure the zinc being dosed to the animals is providing a protective zinc level in the bloodstream
3. GGT blood tests in a sample of cows can detect if any subclinical liver damage is occurring.

Speak to the vets if you are interested in any of these tools. ZincCheck – the new Fonterra Bulk Milk test for herd zinc levels. This is a bulk milk test (actually based on 3 tests taken within 5 – 15 days apart) that measures zinc levels.

Studies (2017 and 2020) have been done during the development of this test to correlate bulk milk with herd serum zinc levels. There was an 84% correlation with predicting adequate zinc supplementation to provide protection. The test was also 95% effective at detecting if overdosing/zinc toxicity is occurring.

Further blood testing is an option to confirm abnormal findings if results indicate an issue.

All Fonterra suppliers will be offered one free ZincCheck test this coming eczema season (Autumn 2022); they will also have the option to purchase additional tests. Farmers can opt-in to have their ZincCheck results automatically sent to their nominated veterinary clinic, as veterinarians are able to support farmers to optimise their FE management programme.

I would highly recommend undertaking this test, to confirm your zinc programme is working effectively.