Sheep a major source of leptospirosis infection

Wednesday 30 April 2008, 3:03PM
By Massey University


The changing profile of victims of leptospirosis and the high number of cases amongst Hawke’s Bay meat workers have prompted a co-operative study into the disease between Massey University’s EpiCentre and meat company PPCS. The research was carried out in February and March at the PPCS Takapau plant.

Thirteen of 15 patients admitted to the ICU at Hawke’s Bay Hospital suffering from leptospirosis from 1999-2005 were employed as meat workers or inspectors.

Blood samples and interviews were conducted with 242 volunteers. Twenty-three, (9.5 percent), tested positive to antibodies for Leptospira serovars pomona (13) or hardjo-bovis (9) and one tested positive to both.

Dr Jackie Benschop says these workers had occupational exposure to sheep only. “This, in combination with our results, adds weight to the hypothesis that sheep are an important source of leptospiral infections for humans.”

The results are preliminary and the EpiCentre leptospirosis team, led by Associate Professor Cord Heuer, still has more work to do on the data collected.

“These results are not adjusted for the fact that these workers may have had exposure to leptospirosis outside of the workplace,” says Dr Benschop. “We’ll be concentrating on potential lifestyle exposure to leptospirosis in the data over the next few months.”

Further data analysis will also help determine the effect of the worker position in the meat plant on exposure to Leptospira species, giving clues to transmission pathways.

Dr Benschop says workers reported - and researchers saw - good use of protective gear at the PPCS plant, with staff wearing gloves, glasses and face masks when working in potentially exposed areas, limiting exposure to Leptospira bacteria that are shed in the urine of infected animals.

Keith Sandilands, PPCS group health and safety manager, says the company has a rigorous policy around the wearing of personal protective equipment. With support from occupational health nurses and doctors the company runs a leptospirosis education programme, including sound knowledge on early intervention.

“This has eliminated reported cases to a large extent and enables early treatment in the isolated reported cases,” says Mr Sandilands. “In the majority of instances this alleviates to a significant level the potential severity of the symptoms that individuals can experience with this condition.”

The EpiCentre team intends to build on the study to look at other occupationally-exposed groups including those working with cattle such as farmers, meat workers, technicians and veterinarians. Over the 2001-2003 period most human leptospirosis infections in New Zealand were associated with contact with cattle, either on their own or with other animals.

“Disease control in New Zealand has focused on dairy cattle and pigs, however an estimated 90 percent of beef and 10 percent of dairy herds are still not vaccinated. Exposure from deer and sheep is also high.

“Research to determine a baseline prevalence amongst people who have no occupational exposure is another important area for future work,” says Dr Benschop.

Researchers believe there is significant under-estimation of the disease, particularly as it takes seven to 10 days for leptospirosis to be detected by blood tests, leading to under-reporting.

“What we can say is that leptospirosis is a serious disease of unknown magnitude,
with leptospirosis incidence in New Zealanders high in comparison with other temperate developed countries.”

A rise in public interest and awareness of leptospirosis follows news last year that a meat worker had died from the disease. This prompted the revival of Rural Women New Zealand fundraising for leptospirosis research. Earlier fundraising efforts by the organisation enabled the publication of more than 70 research papers by Massey University scientists in the 1970s and 1980s and the development of vaccines for cattle and pigs.

The exposure of meat workers is one of the areas requiring further research identified in the Department of Labour’s report into leptospirosis last August.

“We are especially grateful to PPCS for its assistance and willingness to participate in the study,” says Dr Benschop.

On 19 May Rural Women New Zealand will present a cheque for leptospirosis research to Dr Benschop at its national conference in Blenheim, following its year-long leptospirosis fundraising campaign.

Dr Jackie Benschop will present the results of the PPCS study at the New Zealand Veterinary Association Conference to be held in Wellington from 25-28 June.

Leptospirosis Data

In New Zealand meat workers are one of the occupations most at risk of contracting leptospirosis, comprising 30 percent of notifications in 2006
Infection can result in severe illness and in some cases death.
During 2003-2005 leptospirosis resulted in 207 hospitalisations
The majority of cases of leptospirosis are relatively mild and may be misdiagnosed as influenza.
The true incidence of leptospirosis is probably many times the reported incidence.
Leptospira species have many animal hosts including the main livestock species, wildlife and rodents.
An NZ slaughterhouse survey in lambs found 59 percent of lines had one or more carcasses with antibodies to two of the strains of leptospirosis – hardjo-bovis or pomona.
Leptospirosis occurs more frequently in humans in NZ than in any other country where it is notifiable.
Beef herds exposure to hardjo-bovis and pomona is high with prevalence estimates over 50 percent for serovar hardjo-bovis.
A survey of 110 deer farms found hardjo-bovis was present on 61 percent.
A slaughter-house survey in lambs found 49 percent of lines had one or more carcasses with titres to either hardjo-bovis, pomona or both
There is evidence that clinical disease in sheep and deer is emerging with morbidity and mortality in lambs and weaners.