Prolonged, mild weather in Autumn appears to have caused high rates of facial eczema in sheep in some parts of the North Island.
The disease is caused by toxin in a fungus that grows in grass. The toxin affects cattle, sheep, goats and deer and can result in liver and skin damage and weight loss, which can stop animals from falling pregnant and in some cases result in death.
It is estimated that production losses caused by the disease are around $200 million annually in New Zealand.
A senior animal proteins analyst for AgriHQ, Mel Croad, said farmers in Hawke's Bay, where she was based, and Waikato, had started to scan ewes to find out if they are pregnant.
Some of those had found lower than normal pregnancy rates among their flock, Ms Croad said.
"The results have been fairly mixed, but the key note that everyone's making is that dry rates [ewes that aren't pregnant] in some of their mobs have been quite a lot higher than normal, and most are just putting that down to the possibility of facial eczema being around," she said.
The fungus, Pithomyces chartarum, that causes facial eczema becomes a problem when spore numbers skyrocket in warm, moist conditions.
Ms Croad said prolonged mild weather conditions in Autumn appeared to have exaggerated this issue for farmers.
"We're hearing instances of people finding sheep that are showing clinical signs of facial eczema where they've sort of never had facial eczema present in their flocks before," she said.
Beef and Lamb (BLNZ) senior advisor Will Halliday said he had received reports of high levels of facial eczema in some areas, while others seemed to be less affected than they were in 2018.
"So we've seen quite a lot of facial eczema, particularly on the East Coast of the North Island this year. It also seems to be gradually moving up [in] the altitude, so we've seen some cases in Taumarunui, for example and Taihape," he said.
Mr Halliday said preliminary scanning results so far didn't seem to be too badly affected at this stage, but BLNZ expected to see some health issues in ewes going into winter, which farmers needed to keep an eye out for.
Farmers who thought they might have stock affected by facial eczema were advised to consult their vet and make sure the animals had lots of feed, Mr Halliday said.
Breeding for facial eczema tolerance in sheep was the best option farmers had at the moment, he said.