Facial Eczema

NEW Findings 2016


Emma Cuttance, a vet from Te Awamutu, recently did a FE study on 1000 cows across 100 NI herds. She found that 79% of cows and 33% of herds had high GGT levels (i.e. liver damage). When they tested zinc levels, 53% of cows were below protective levels, 44% were in the ballpark, and 3% were high (and potentially toxic).Cows supplemented with zinc in water were 5.5 times more likely to have blood zinc levels below protection, compared to cows being drenched. Furthermore, dose rates of zinc were low on 42/68 farms.

The next thing they checked was 160 cows in 16 Waikato farms feeding zinc oxide mixed with supplements in-shed or on a feedpad. They found that 44% of cows had low zinc levels, 46 % were at protective levels and 10% were too high
(risking toxicity). The feedpad systems yielded more variable zinc blood levels, presumably due to differing DM intakes.
The team also trialled applying lime to paddocks in November or March; it had NO effect on the spore count.

So we can still improve our FE protection programs:
  • double-check your zinc dose rates to avoid underdosing or poisoning.
  • check levels in blood and feed to see if you need to alter your program.
  • zinc sulphate in the water on its own may not give adequate protection in a high challenge year / farm. Alternatives include drenching zinc oxide or mixing it with feed supplement, administering zinc bullets,or applying fungicide spray to pasture. I would add that CRV are also focusing on breeding FE resistance,and various summer crops have a lower risk of spores, such as fescue or chicory.
  • monitor spore counts on your farm specifically by dropping in pasture samples.This will allow you to start and stop zinc supplementation at the correct time of risk, or to avoid high risk paddocks

Causes and Symptoms

 
Facial eczema (FE) is a disease of sheep, cattle, deer and goats that causes death and lowered production from liver injury, mainly during periods of warm humid weather between January and May.  The pasture fungus Pithomyces charatarum multiplies and produces spores, which contain the toxin sporidesmin.  Sporidesmin causes injury to the liver, the bile ducts become thickened and may be completely blocked .  The damaged liver cannot rid the body of wastes and a breakdown product of chlorophyll accumulates in the tissues and causes sensitivity to sunlight.  Sunlight causes immediate and severe skin inflammation to exposed parts of the body.
 
The symptoms of FE therefore can vary from severe photo-sensitisation and in some cases death to sub-clinical effects on the production of meat, wool and milk.  In any FE outbreak, many animals with liver damage show no clinical signs - but they suffer from sub-clinical FE.
 

Toxic Conditions

 
For rapid growth and spore formation the fungus needs warm, moist conditions common during the autumn.  4-5mm of rain or even heavy dews in conjunction with 2-4 nights when grass minimum temperatures remain above 12 degrees Celsius are sufficient to initiate rapid increases in spore numbers.  Spore counts rise even more rapidly when higher grass minimum temperatures (15-16 degrees Celsius) are associated with high humidity and/or light rain.  Generally it takes two or three such “danger” periods before spore numbers reach dangerous levels, each spore rise providing the base for the next increase in spore numbers.  However prolonged periods of warm, humid weather early in the season can accelerate the onset of toxic pastures.

 

THERE IS NO SUCH THING AS AN UNQUALIFIED

“DANGEROUS SPORE LEVEL”

 
Cambridge Vets monitor several farms during the danger period.  THESE SHOULD BE USED AS A ROUGH GUIDE ONLY.
Spore numbers can vary not only on individual farm and district but also within and between paddocks depending on the topography, aspect, altitude and previous management practices. Species vary in their susceptibility to FE.  Fallow deer and sheep are most susceptible, followed by dairy cattle, beef cattle and red deer.  Most resistant are goats.


 

The toxicity of a pasture at any one time depends on several factors.

· The spore count.
· The age of spores in the pasture (old spores are less toxic).  
· The grazing intensity and level of the pasture being consumed. (Animals grazing down at the base of the pasture are at most risk).
· Prior exposure of animals to toxic spores (makes them more susceptible).
· The susceptibility of different breeds and species.
· The length of time for which the high level is present and consumed.
 
Depending on the above factors the level of spores on pasture may prove to be toxic anywhere above 40,000 spores/gram of grass.  Long-term ingestion of lower levels of spores may also lead to FE.

 

Prevention

 
Prevention is by management as well as zinc therapy or pasture spraying.
Beware  - we usually face a LONG facial eczema season
Zinc based prevention relies on dosing animals with zinc salts, either zinc oxide as a drench  or water treatment with zinc sulphate, or the zinc bolus.
· Dry stock can be dosed at twice weekly or even weekly intervals.
· Zinc dosing can be expected to reduce, but not completely eliminate FE outbreaks.



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