Facial eczema: the hidden disease

Facial eczema: the hidden disease
By Scott McDougall, Cognosco - Research Division of Anexa FVC Vets

With the warm humid weather we’ve been experiencing, the facial eczema spore counts on pasture are rising with subsequent risk of liver damage and photosensitisation in cattle.
The clinical signs of peeling skin, sensitive udders and milk drop are very obvious outward signs that the sporidesmin toxin has caused liver damage.

But are cows clinical signs the only ones affected?
No, clinical cases are the proverbial tip of the iceberg. The degree of liver damage in both clinical and nonclinical cows can be assessed by measuring the blood concentration of an enzyme called gamma glutamyl transferase (GGT). GGT rises a couple of weeks after spores are eaten. A concentration of GGT of >36 IU/L indicates liver damage, while GGT >800 IU/L indicates severe liver damage. We bleed 30 cows without clinical signs and all those with clinical signs in 10 herds where there was clinical facial eczema. All of the cows with clinical eczema had GGT levels >36 IU/L (Table 1; Figure 1), and 24 of the 27 (85%) had GGT concentrations >800 IU/L. However, amongst those cows without clinical signs, 47% had GGT >36 IU/L and 16% had GGT >800 IU/L.

So if you are seeing clinical facial eczema, there will be other cows with liver damage in the herd. Any signs of clinical facial eczema should be taken seriously and zinc treatment reviewed, zinc levels in cows tested and grazing strategies to reduce spore exposure considered.

For further information and advice, talk to your Anexa FVC Vet.

Date Added: Friday, 1st December 2017