Study co-ordinator Shahista Nisa says leptospirosis can be seriously debilitating and even after treatment its effects can last for a long time.
The flu-like symptoms of leptospirosis include fever, headache, tiredness, sensitivity to light, muscle pain and cramps, chills, jaundice, nausea, skin rash and sweating.
"The disease is treated with antibiotics but for some people the symptoms remain for months and sometimes years. Some people are never able to return to work in their chosen field because of the extreme fatigue symptoms that can linger and leave them unable to work,'' she said.
The study, which is being led by principal investigator Jackie Benschop, entails several detailed questionnaires.
Nisa says the disease affects about 10 people a year in the Northland region and Massey's researchers are working closely with district health boards and Māori health organisations to identify and recruit newly infected study subjects.
Dr Tanya Quin was at the Dargaville Field Days last week spreading the word about the disease and the study. Charts showed how Northland infections have been growing and risk groups are changing.
More women are becoming infected, possibly as there are more working on farms, and over 50 per cent of leptospirosis patients require hospitalisation. Animals vaccines work well but don't cover all strains of lepto.
Nisa says there are more than 300 different variations of bacteria which cause leptospirosis worldwide, of which five are known to be in New Zealand. Only three of these are covered by the current vaccines, which means leptospirosis is continuing to grow in the community.
She says Northland is currently in the top five DHBs with reported leptospirosis cases and the study aims to find out why.
"Perhaps it's because of the hotter climate so perhaps there are more rodents. Also because it's more rural, there are a lot of people outside, including gardening.
"Floodwaters can also be a risk. It's a disease that is rarely reported in urban environments in New Zealand. Finding out the risk factors is an area of interest for us,'' she said.
Surveys of newly infected study subjects will ask questions about exposure to animals, travel, water and recreational activities to try and find the causes of their exposure to the illness.
Six months later another survey will ask how they are recovering.
"One in three patients can suffer effects long after infection, for months and even years,'' she said. "A study in the Netherlands showed some people had continuing symptoms such as extreme fatigue and headaches for up to two years.''
Nisa says changing farm practices such as herd homes and feeding supplements such as palm kernel which could be attractive to rodents could be among risk factors.
"We want to know if farmers are seeing evidence of rodents in these areas.''
Shearers and wool handlers can be exposed to urine-soaked wool. Milking, calving, cleaning effluent in yards, flood waters, and pets such as cats and dogs can all pose a risk, she says.
"Cats love eating rodents, and dogs can get very sick from leptospirosis. They can die from it.''
Nisa says workers in high-risk industries should make sure cuts and scratches are covered and protective gear should be worn.
"The first thing is hygiene and making sure workers wear gloves and protect eyes with goggles especially in the milking shed, where urine can splash around, and in feed storage areas. Rodent control on farms, especially around sheds and feed storage is important.''
The leptospirosis study aims to find about 150 newly infected recruits over the next couple of years.
