Facial eczema has killed at least nine dairy cows in the Okato area of coastal Taranaki.
Six cows have died on one farm and about 12 are sick. On another farm one cow has died and clinical cases number about 18.
Okato vet Graeme Charteris said 770,000 facial eczema spores were recorded yesterday just hours after the count was 540,000.
Counts in the district were averaging 300,000 yesterday after being between 60,000 and 120,000 on Friday, Charteris said.
He's warning farmers the facial eczema season is not over.
"Rain and warmth are a hotbed for facial eczema spores," he said. "Farmers need to be vigilant with protection. Counts could stay high until well into May, so don't stop treatment."
This week's counts were significant and farmers needed to ensure their cows were receiving the right dose of zinc to combat facial eczema.
Zinc could be given as a drench, added to stock water supplies, or applied to pasture as a spray.
At such high numbers, zinc capsules were the most effective form of treatment at 95 per cent, while water treatment was about 70 per cent effective.
Spore counts above 50,000 are considered to be a trigger level for the disease for unprotected stock exposed to that figure for a length of time.
Charteris said unprotected stock would die rapidly or be badly affected if they ate pasture with such high spore counts.
Taranaki Veterinary Centre chief executive Stephen Hopkinson, of Hawera, said counts around Patea were at a medium level but counts in other areas serviced by the group were still low.
Facial eczema damages the liver and affected animals lose weight, are sensitive to sunlight, suffer peeling and thickening skin, lick their udders and their milk production falls.
It is caused by a fungus that grows on soft or dead leaf litter at the base of pasture when conditions are moist and when the grass minimum night-time temperature are above 12 degrees Celsius for two or three nights.
- Taranaki Daily News