South Island farmers are currently achieving greater success than those in the North in controlling Taenia ovis (T. ovis) - or sheep measles, according to the latest analysis by the Ovis Management programme.
Ovis or sheep measles is caused by the T. ovis tapeworm.
Although it poses no risk to human health, it can cause blemishes in sheep meat, which is undesirable for consumers here and overseas.
The programme promotes the control of T. ovis through communication and collaboration and by raising awareness of the importance that all dog owners regularly treat their dogs for the tapeworm.
Controlling sheep measles was important for the primary sector, according to Michelle Simpson, Ovis Management project manager.
While New Zealand currently has relatively low levels of sheep measles, an outbreak can result in the downgrading or condemnation of otherwise healthy animals.
Only 20 per cent of Ovis-affected carcasses are detected during meat inspection at processing plants, therefore the higher the prevalence rate, the higher the risk of meat from affected animals reaching the market.
"It costs farmers and processors a lot of money due to condemned stock," Simpson said.
"One concern with Ovis is that if a farmer is not the one sending their lambs for processing, they may not know that they are passing the problem on."
Simpson said data from the programme demonstrated that sheep measles can be controlled when farmers take the simple steps of regularly treating their dogs for the Taenia tapeworm.
"Dogs can become infected by eating untreated meat or offal, infected with live cysts. T. ovis is then spread to sheep through tapeworm eggs in dog faeces left in grazing areas."
Eggs can also be spread from dog faeces over large areas, predominantly by flies, she said.
"Best practice for dog health and sheep measles prevention is for all farm dogs to be treated monthly with cestocidal (tapeworm) drugs containing the ingredient Praziquantel - a cheap and effective treatment - and an All Wormer every three months."
All dog owners, such as hunters or farm visitors, who take their dogs near farmland, or where sheep graze, should also dose their dogs every month, Simpson said
"[This is] because the tapeworm has a 35-day lifecycle and dosing three-monthly is not enough to stop the parasite from spreading."
Sheep farmers should make this a condition of entry for all visitors bringing dogs onto the property, as part of their on-farm biosecurity plan, Simpson said.
Sheep measles: The numbers
Data from processors from October 1, 2021, to June 30, 2022, shows that the Southland region had one of the country's lowest occurrences of sheep measles identified in carcases, despite sending the highest number of animals for processing.
Of 1,919,242 sheep processed in the region, from 1510 farms, 1884 (0.1 per cent) of carcasses were found to be affected.
Buller and Westport had no affected carcasses, processing just over 13,000 sheep in total.
The highest number of sheep processed in a North Island area for that period was from the Gisborne district, with 694,266 livestock from 431 farms.
Of these, 5355 (0.8 per cent) of carcasses were affected.
Most South Island districts recorded low proportions of affected carcasses, apart from Marlborough (0.9 per cent) and Kaikōura (1.0 per cent).
Ōpōtiki recorded the second highest proportion of sheep measles nationally (1.7 per cent of carcasses processed), followed by the Kāpiti Coast (1.1 per cent).
Whakatāne (0.9 per cent), Ōtorohanga and Auckland (both 0.8 per cent) were also among areas with higher proportions of affected stock.
Some neighbouring districts recorded significantly different results, despite similar processing numbers.
Hastings/Napier had 669,499 sheep processed, from 446 farms with 4451 (0.7 per cent) of carcases affected.
Central Hawke's Bay processed 653,279 sheep from 462 farms with 2813 (0.4 per cent) affected.
In Marlborough, 156,716 sheep were processed from 242 farms, with 1396 (0.9 per cent) affected.
In neighbouring Tasman,146,437 sheep were processed from 241 farms, with only 332 carcases (0.2 per cent) affected.
For more information or to view the T. ovis prevalence map, showing data for all regions, see www.sheepmeasles.co.nz.