Facial eczema is caused by a toxin (sporisdesim) produced by the spores of the fungus Pithomyces chartarum growing on pasture. The fungus grows in the dead litter at the base of pasture in warm moist conditions.
Sporisdesim, 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 of the skin.
Signs to look for
- a drop in milk production
- cows are restless, seeking shade and lick 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) has occurred. It is estimated that for every clinical case there will be 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).
Timing
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 as does topping which increases the build-up of soft litter.
Prevention
There is no cure for 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.
Breeding cows that are more tolerant to facial eczema is a solution to reduce the impact from facial eczema in the long term.
Treatment
Cows showing clinical signs of facial eczema can recover if prompt action is taken
- Dry off affected cows now, 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) but make sure there is a good water supply and supplementary feed available for cows
- 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 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
- Make sure the diet is balanced, with good levels of energy and protein.
In addition to the above, for very sick cows
- Use a starter drench to boost metabolic function
- Use vitamin B12 supplementation
- Seek veterinary advice regarding additional pain relief treatment.
Practical 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.
When making decisions to cull cows act early before body condition score and the severity of the condition cause unnecessary distress and suffering. If sending cows for processing farmers need to be aware that animals will not be accepted if emaciated or with severe skin damage (sores, weeping wounds etc.).
Resources:
Facial eczema: management for New Zealand dairy herds
Steps to managing facial eczema using zinc
Farmfact 3-6: Facial eczema – treatment and prevention
Farmfact 3-7: Facial eczema – zinc treatment, recipes and dose rates
