Investigation and response to an outbreak of leptospirosis among raspberry workers in Australia, 2018.

BACKGROUND: In 2018, an outbreak of leptospirosis was identified among raspberry workers from a mixed-berry farm in New South Wales, Australia. Initial testing had not revealed a cause, but eventually leptospirosis was detected via polymerase chain reaction (PCR). Further serological testing detected Leptospira borgpetersenii serovar Arborea, of which rodents are the predominant reservoir. Leptospirosis is rare in Australia, with outbreaks usually related to flooding. We conducted an investigation to identify risk factors for infection, to inform control measures. METHODS: Cases were detected through laboratory notifications, hospital-based syndromic surveillance, awareness-raising among farm employees and clinician alerts. Confirmed cases had a four-fold rise in antibody titre or single titre ≥400 on microscopic agglutination test, and a positive IgM. Probable cases had a positive Leptospira PCR or IgM, and possible cases had a clinically compatible illness. We conducted a case-control study among raspberry workers on the farm and compared reported exposures between cases and seronegative controls. We assessed environmental risks on-site and tested rodents for leptospirosis. RESULTS: We identified 84 cases over a 5-month period (50 confirmed, 19 probable and 15 possible). Compared with controls, cases were less likely to wear gloves and more recently employed. Cases also more commonly reported always having scratched hands, likely from the thorns on raspberry plants. We observed evidence of rodent activity around raspberry plants and three of thirteen trapped mice tested positive for Leptospira Arborea. Control measures included enhanced glove use, doxycycline prophylaxis and rodent control. CONCLUSIONS: This is the largest known outbreak of leptospirosis in Australia. Workers were likely exposed through scratches inflicted during harvesting, which became contaminated with environmental leptospires from mice. Leptospirosis should be considered an occupational risk for raspberry workers, requiring protective measures. Chemoprophylaxis may assist in controlling outbreaks. PCR assists in the early diagnosis and detection of leptospirosis and should be included in surveillance case definitions.

Clinical diagnosis and chemical confirmation of ciguatera fish poisoning in New South Wales, Australia.

Ciguatera fish poisoning is common in tropical and sub-tropical areas and larger fish (> 10 kg) are more susceptible to toxin accumulation with age. Although the coastal climate of northern New South Wales is considered sub-tropical, prior to 2014 there has only been 1 documented outbreak of ciguatera fish poisoning from fish caught in the region. During February and March 2014, 2 outbreaks of ciguatera fish poisoning involved 4 and 9 individuals, respectively, both following consumption of Spanish mackerel from northern New South Wales coastal waters (Evans Head and Scotts Head). Affected individuals suffered a combination of gastrointestinal and neurological symptoms requiring hospital treatment. At least 1 individual was symptomatic up to 7 months later. Liquid chromatography-tandem mass spectrometry detected the compound Pacific ciguatoxin-1B at levels up to 1.0 µg kg(-1) in fish tissue from both outbreaks. During April 2015, another outbreak of ciguatera fish poisoning was reported in 4 individuals. The fish implicated in the outbreak was caught further south than the 2014 outbreaks (South West Rocks). Fish tissue was unavailable for analysis; however, symptoms were consistent with ciguatera fish poisoning. To our knowledge, these cases are the southernmost confirmed sources of ciguatera fish poisoning in Australia. Educational outreach to the fishing community, in particular recreational fishers was undertaken after the Evans Head outbreak. This highlighted the outbreak, species of fish involved and the range of symptoms associated with ciguatera fish poisoning. Further assessment of the potential for ciguatoxins to occur in previously unaffected locations need to be considered in terms of food safety.

A field study of household attack rates and the effectiveness of macrolide antibiotics in reducing household transmission of pertussis.

Bordetella pertussis (whooping cough) is an endemic, highly contagious bacterial respiratory infection, which is notifiable to Australian state and territory health departments. Between 2008 and 2011 there was a substantial outbreak in New South Wales with an initial increase in cases occurring in North Coast New South Wales from late 2007. During September and October 2011 the North Coast Public Health Unit conducted a household study of secondary attack rates to assess the effectiveness of pertussis vaccination as well as the timely use of antibiotics in preventing household transmission. At the time the study was commenced, notified cases included a large proportion of individuals with a documented history of vaccination against pertussis. We found lower attack rates amongst vaccinated compared with non-vaccinated subjects in all age groups, with the exception of the 5-11 years age group, who were also primarily responsible for the introduction of pertussis into the household. There was an increased risk of pertussis transmission from the household first primary case to contacts when antibiotic treatment was commenced later than 7 days after the onset of symptoms compared with within 7 days. This protective effect of timely antibiotic treatment in relation to transmission highlights the need to control for antibiotic treatment in field studies of pertussis. The benefits of timely diagnosis and use of antibiotics in preventing household transmission underscore the importance of early presentation and diagnosis of pertussis cases, particularly in households with susceptible occupants.

Lessons from a respiratory illness outbreak in an aged-care facility.

This report outlines practical lessons learnt from an influenza-like outbreak in an aged-care facility in NSW, which affected 26 residents, resulted in 14 hospital admissions and was associated with six deaths. No common causative agent was identified. Key recommendations include: encouraging aged-care facilities to establish mechanisms that improve the early identification of outbreaks and timely implementation of outbreak control strategies; identifying strategies to inform general practitioners of outbreaks if they have patients residing in aged-care facilities; and improving the vaccination coverage of the aged-care workforce.

The role of television advertising in increasing pneumococcal vaccination coverage among the elderly, North Coast, New South Wales, 2006.

North Coast Area Health Service (NCAHS) conducted a seven week television advertising campaign to raise community awareness of the availability of free adult pneumococcal vaccination and to increase coverage among North Coast residents in high risk groups. Effectiveness of the campaign was evaluated by examining vaccine ordering patterns of North Coast vaccination providers from 2005/2006 as a proxy for vaccination coverage. In the months during and immediately following (June-September 2006) the advertising campaign, a significantly higher proportion of vaccines were despatched to North Coast immunisation service providers. The advertising campaign was an effective strategy to promote vaccination among NCAHS residents not immunised in the first year of the National Pneumococcal Program for Older Australians. This higher immunisation coverage is expected to contribute to the statewide trend of significant reductions in invasive pneumococcal disease (IPD) notifications.

Immunisation attitudes, knowledge and practices of health professionals in regional NSW.

OBJECTIVE: This study investigated the immunisation knowledge, attitudes and practices among health professionals in two regional Area Health Services of NSW with low and high immunisation rates. It also compared these factors between the areas and between the health professional groups. METHODS: A self-administered questionnaire was posted in 2006 to health professionals, located within the North Coast and Hunter New England Area Health Services, whose practice could include immunisation. This included general practitioners (GPs), practice nurses, community nurses, hospital nurses and midwives. RESULTS: Out of 926 surveys sent, 434 were returned (47%). The great majority of the health professionals (97%) believed that vaccines were safe, effective and necessary. However, in approximately one-third of respondents, there were specific concerns about additives, immune system overload and the number of vaccines. Significantly more health professionals in the North Coast area believed that additives in vaccines may be harmful and that adding more vaccines to the schedule would make immunisation too complex. Among GPs, over half felt uncomfortable about giving more than two injections at the one visit. CONCLUSIONS: Health professionals in this study had overall confidence in vaccines but had specific concerns about the number of vaccines given to children and vaccine content. These unfounded concerns may reduce parental confidence in immunisation. IMPLICATIONS: There is value in governments and immunisation support workers continuing their efforts to maintain up-to-date knowledge among health professionals and support the delivery of appropriate and targeted information to address concerns about vaccines.