Facial eczema

What is facial eczema?

Facial eczema (FE) is a disease that causes liver damage, lowered production, skin irritation and peeling, and sometimes death.

Facial eczema is caused by sporidesmin, a toxin produced primarily by the spores of the fungus Pseudopithomyces toxicarius growing on pasture. The fungus grows in the dead litter at the base of pasture in warm moist conditions.

Sporidesmin, when ingested by cattle, damages the liver and bile ducts. The damaged liver cannot get rid of a breakdown product of chlorophyll that builds up in the blood causing sensitivity to sunlight, which in turn causes inflammation of the skin.

The fungus produces spores when grass minimum temperatures are above 12°C for two or three nights and humidity is high (usually January to May).

The fungus grows on soft litter at the base of the pasture so hard grazing during danger periods increases the risk of spore intake. Pasture management, which increases the build-up of soft litter, is a likely contributor to increased FE risk.

What to look for

• a drop in milk production
• cows are restless, seeking shade and licking their udder
• exposed, unpigmented or thin skin reddens, thickens, and peels

Not all animals affected with FE show physical signs (i.e. clinical FE) although liver damage (i.e. subclinical FE) may have occurred. It is estimated that for every clinical case, there will be at least 10 cows with subclinical FE.

Milk production of animals with subclinical FE can be depressed by up to 50%. Blood tests can be used to monitor the extent of subclinical FE.

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 treatment that reverses the liver damage caused by FE so prevention is the only way of protecting animals. To be effective, preventative measures need to be in place before eczema spores are found.

Preventative measures include monitoring pasture spore count and either dosing animals with zinc or spraying pastures with a fungicide.

Treatment

Cows showing clinical signs of facial eczema can recover if prompt action is taken:

• Provide pain relief as prescribed by your veterinarian.
• Dry off affected cows immediately, to reduce pressure on the liver.
• Put zinc cream on white areas of the coat and the udder (if affected).
• Move affected stock into dense shade. Indoors is best (hay-barn, calf-rearing and implement sheds) ensuring access to a good water supply and supplementary feed.
• Feed cows at night, so they are not exposed to sunlight and stop hard grazing so cows do not graze down into dead matter where most of the spores that cause FE live.
• Feeding maize and/or silage can help, but cows will still tend to graze if they are kept on pasture.

In addition to the above, for very sick cows talk to your veterinarian about treatment options.

Indicators of recovery include liveweight gain and improvement in body condition score (BCS). Be aware that animals can take up to 12 months to fully recover. Animals with a previous history of clinical FE have a lower chance of recovery than previously unaffected animals due to prior liver damage.

When making decisions to cull cows, act early before low body condition score and skin irritation negatively impact animal welfare. Read transporting stock to check if cows are fit for transport.

Zinc dosing

Start early based on spore counts. Weigh a representative sample of at least 20 cows in each of the mobs to be treated to calculate the dose of zinc required. All classes of animals are at risk, from calves to adult cattle.

Fully dose cows with zinc but take extra care when calculating dose rates - zinc is toxic in high doses and signs of toxicity can present very similarly to facial eczema.

Common options for dosing are drenching with zinc oxide, water dosing with zinc sulphate, administering in-feed or as an intraruminal bolus (e.g. Time Capsule, Face-Guard).The more control a farmer has over the amount of zinc a cow receives the more likely it is that the cows are receiving the correct daily dose. Zinc drenching and intraruminal bolus are the most reliable forms of prevention.

Recent research has shown that zinc delivered through drinking water is not recommended as the sole method of facial eczema prevention because individual water intake is highly variable. When dosing zinc in water, it needs to be combined with another method of administration (e.g. in-feed) and monitored closely.

Talk to your veterinarian about options to monitor whether your FE management programme is working. Since 2022, Fonterra suppliers have had the additional option of using ZincCheck - a bulk milk test to indicate whether the majority of the herd may have reached the zinc level needed for protection from FE. ZincCheck should not be used as a complete replacement for other forms of monitoring.

Pasture spraying

Spraying the pasture with a fungicide will slow the development of the fungus and subsequent production of spores. Apply only when pasture has confirmed spore counts below 20,000 and is green and growing.

Spraying should cover all areas including fence lines and under hedges. Check spore counts after spraying and before grazing, to ensure pastures are below acceptable levels. Pasture will be safe for 4-6 weeks after which they will need to be resprayed or monitored with spore counting.

Minimise the build-up of soft litter by avoiding topping and managing pasture quality in November/December. Avoid grazing below 4cm pasture height during summer months; use supplements to reduce grazing pressure.

FE tolerant genetics

Breeding cows that are more tolerant to facial eczema is a longer term solution to reduce the impact from facial eczema. Facial eczema tolerance is a heritable trait and the right breeding programme can reduce the severity of the disease over time.

Breeding companies offer FE tolerant sires in their bull catalogues. Cows resulting from FE tolerant sires will typically have improved tolerance to FE spores and maintain production under FE challenge.

Gains in FE tolerance will be made as each generation of daughters from FE sires enters the herd. A full herd with FE tolerance is achievable in 7-8 years. If you’re in a high-FE challenge area, talk to your breeding company for more information.