A landmark study of Leptospirosis by Massey University has found that a strain previously thought to be infrequent raised public health concerns in 10% of the dairy herds in the study with farmers, veterinarians and dairy workers at risk.
The study was the first to explore the effect of long-term vaccination in a nationally representative sample. 200 dairy herds randomly selected from throughout New Zealand and 20 milking cattle were sampled (blood and urine) from each herd between December 2015 and March 2016.
The findings indicated that 97.6% dairy cows in 73.5% of the herds did not shed Leptospira. However, 2.4% of vaccinated cows were shedding from 26.5% of herds. This shedding was predominately associated with a positive blood test to a re-discovered strain (serovar Tarassovi), which is not currently controlled by vaccines. The association is shown in the figure below.
Director of the EpiCentre Professor Cord Heuer says “We can now be confident that vaccination is effective in dairy herds, but the Tarassovi strain needs our immediate attention”. He said it cannot easily be included in commercial vaccines on the short run. Until new vaccines become available, people in rural occupations need to be aware and take protective measures against leptospirosis.
“2.4 per cent of over 5 million cows across the country is 120,000 cows – people working with dairy herds are exposed every day – a vet doing 120 pregnancy tests, a farmhand milking twice a day, even people’s families are at risk of exposure. The fact that the new strain is associated with most of the cases of shedding is evidence that the vaccine works for the others, so keep programmes in place – that means regular programmes with calves receiving first shots at 3-6 months with booster shots throughout their lives to ensure the best protection.
Massey University’s mEpiLab co-director Dr Jackie Benschop says management of this infection on dairy farms is an essential on-going issue. “Vaccination programmes have been considered a cornerstone in the prevention of human disease for many years, and continue to be an effective measure to prevent shedding [the release of bacteria into the environment from urine] of strains contained in the vaccine.”
Dr Julie Collins-Emerson, molecular biologist and leptospirologist, adds “We can’t say it enough – the emergence of new strains doesn’t mean you should abandon your vaccination programmes against the regular strains as they are still just as dangerous as once they were. Our results reinforce the importance of a multi-faceted approach to this complex disease – controlling rodents and wildlife, good personal hygiene and awareness of risks both on and off the farm.”
Dean of Veterinary Sciences Associate Professor Jenny Weston advises “Farmers must ensure that all cattle on the farm are vaccinated and the vaccine is administered at the right time(s) of year in conjunction with veterinary advice. Other risk management approaches such as rodent control and effluent management need to be included given the risk from other strains of the bacteria which aren’t in the current vaccines. The development of new vaccines is not going to be quick or easy.”
“We are using the results of this study to update best practice guidelines for farmers, veterinarians and industry stakeholders in order to reduce infection in animals and people working on farms and in the dairy industry. They come with a list of recommendations for humans coming into contact with herds.”
A Farmer Leptospirosis Action Team (FLAG) was established that includes representatives from Massey University, the New Zealand Veterinary Association, Rural Women New Zealand and DairyNZ. The group made the study results available to participating farmers, vets, and stakeholders of industries, government and the public.
Funding has been provided by the Sustainable Farming Fund of the Ministry for Primary Industries, AgMardt, industry and stakeholder groups.
The list of recommendations is available here [link: http://www.worksafe.govt.nz/worksafe/information-guidance/all-guidance-items/prevention-and-control-of-leptospirosis]. Advice includes: controlling rodents and wildlife, good personal hygiene and being aware of not only your exposure, but others and exposure outside of the farm.
The ‘Leptospirosis Dairy Study 2016’ from Massey’s Farmer Leptospirosis Action Group Dairy (FLAG-Dairy) the first to explore the effect of long-term vaccination in a nationally representative sample of herds by looking at vaccine use and efficacy.
The study was prompted by a small pilot study by Professor Peter Wilson of Massey in 2010-11 that found 3% per cent of cows properly vaccinated against the disease were shedding [releasing the bacteria via urine]. These results were not representative of the entire New Zealand dairy population – prompting a more in-depth study into the effectiveness of vaccination on farms.
“Thank you to the many farmers, veterinarians, veterinary technicians and clinic staff who have assisted us with this,” Chair of the group, Professor Cord Heuer says,
The FLAG-Dairy team at Massey University is represented by chair of the group, Professor Heuer and PhD candidate Yuni Yupiana, who coordinated the collection and testing. The work was done in conjunction with 92 vets from around the country who collected blood and urine samples from stock – in order to be collated at Massey University.
To learn more about the disease, click here.
About Leptospirosis
Transmission of the bacteria occurs when infected animal urine, or water contaminated with urine, gets in your eyes, nose, mouth or through cracks in your skin.
Leptospirosis is a globally important disease and in New Zealand it disproportionately burdens rural communities and Māori. It is estimated to cost the NZ economy $36 million per year.
Domestic animal vaccination has been practised since the late 1970s, predominantly in dairy cattle and pigs, and animal vaccination programmes have been considered a cornerstone in the prevention of human disease.
What are the symptoms?
It may just feel like a bad case of flu, with headaches and fever. Some people become seriously ill and need hospital intensive care and it can cause death. The disease might progress to kidney failure, liver failure or meningitis, requiring hospitalisation. Symptoms are often prolonged and recurrent because the physical damage to the kidney and liver may remain after the infection has cleared.
There are around 1000 reported cases each year – the actual number is potentially much higher with uncertainties around underreporting. If you have a ‘flu-like illness seek medical help early and raise the suspicion of lepto to your doctor – “hey doc, might this be lepto?’
Source: Massey University