A six year study by Waikato District Health Board has found that the number of farm workers in the region who contracted the infectious livestock disease leptospirosis was almost double the national rate.
Leptospirosis is commonly associated with cattle and pigs and is transmitted to humans through contact with infected animal urine.
Its symptoms range from jaundice to abdominal pain, fever, nausea, headache, sore throat and vomiting.
Medical officer of health Anita Bell says 97 cases of leptospirosis were notified in Waikatobetween January 2004 and December 2010. Almost half the sufferers were hospitalised for treatment.
She says there was a sustained effort in the 1980s and early 1990s regarding vaccination of dairy herds.
Ms Bell says the study will look at which groups are getting leptospirosis and whether it is still dairy farmers.
She says of those cases that are notified, occupational groups that catch the disease are generally beef and cattle farmers, but also some meat workers.
Ms Bell says dairy farmers tend to vaccinate their herds which helps the animals resist infection.
She says 93% of those who contracted leptospirosis had direct exposure to animals, and 87% had potential exposure to the disease as a result of their job.