Source attributed case-control study of campylobacteriosis in New Zealand.

BACKGROUND: Following an initial reduction in human campylobacteriosis in New Zealand after the implementation of poultry food chain-focused interventions during 2006-2008, further decline has been relatively small. We report a year-long study of notified campylobacteriosis cases, incorporating a case control study combined with a source attribution study. The purpose was to generate up-to-date evidence on the relative contributions of different sources of campylobacteriosis in New Zealand. METHODS: The study approach included: • A case-control study of notified cases (aged six months or more) sampled in a major urban centre (Auckland, every second case) and a mixed urban/rural area (Manawatu/Whanganui, every case), between 12 March 2018 and 11 March 2019. • Source attribution of human campylobacteriosis cases sampled from these two regions over the study period by modelling of multilocus sequence typing data of Campylobacter jejuni and C. coli isolates from faecal samples of notified human cases and relevant sources (poultry, cattle, sheep). RESULTS: Most cases (84%) were infected with strains attributed to a poultry source, while 14% were attributed to a cattle source. Approximately 90% of urban campylobacteriosis cases were attributed to poultry sources, compared to almost 75% of rural cases. Poultry consumption per se was not identified as a significant risk factor. However specific risk factors related to poultry meat preparation and consumption did result in statistically significantly elevated odds ratios. CONCLUSIONS: The overall findings combining source attribution and analysis of specific risk factors indicate that poultry meat remains a dominant pathway for exposure and infection.

Update on the campylobacter epidemic from chicken meat in New Zealand: The urgent need for an upgraded regulatory response.

New Zealand has a long-running campylobacter infection (campylobacteriosis) epidemic with contaminated fresh chicken meat as the major source. This is both the highest impact zoonosis and the largest food safety problem in the country. Adding to this burden is the recent rapid emergence of antibiotic resistance in these campylobacter infections acquired from locally-produced chicken. Campylobacteriosis rates halved in 2008, as compared with the previous 5 years, following the introduction of regulatory limits on allowable contamination levels in fresh chicken meat, with large health and economic benefits resulting. In the following decade, disease rates do not appear to have declined further. The cumulative impact would equate to an estimated 539 000 cases, 5480 hospitalisations, 284 deaths and economic costs of approximately US$380 million during the last 10 years (2009-2018). Additional regulatory interventions, that build on previously successful regulations in this country, are urgently needed to control the source of this epidemic.

Does scientific effort reflect global need? A review of infectious disease publications over 100 years.

In a rational world, scientific effort would reflect society's needs. We tested this hypothesis using the area of infectious diseases, where the research response to emerging threats has obvious potential to save lives through informing interventions such as vaccination and prevention policies. Pathogens continue to evolve, emerge and re-emerge and infectious diseases that were once common become less so or their global distribution changes. A question remains as to whether scientific endeavours can adapt. Here, we identified papers on infectious diseases published in the four highest ranking, health-related journals over the 118 years from 1900. Focussing on outbreak-related and burden of disease-related metrics over the two time periods, 1990 to 2017 and 1900 to 2017, our analyses suggest that there is little underrepresentation of important infectious diseases among top ranked journals. Encouragingly our results suggest the scientific process is largely self-correcting.

Estimating the likely true changes in rheumatic fever incidence using two data sources.

Acute rheumatic fever (ARF) continues to produce a significant burden of disease in New Zealand (NZ) Maori and Pacific peoples. Serious limitations in national surveillance data mean that accurate case totals cannot be generated. Given the changing epidemiology of ARF in NZ and the major national rheumatic fever prevention programme (2012-2017), we updated our previous likely true case number estimates using capture-recapture analyses. Aims were to estimate the likely true incidence of ARF in NZ and comment on the changing ability to detect cases. Data were obtained from national hospitalisation and notification databases. The Chapman Estimate partially adjusted for bias. An estimated 2342 likely true new cases arose from 1997 to 2015, giving a mean annual incidence of 2·9 per 100 000 (95% CI 2·5-3·5). Compared with the pre-intervention (2009-2011) baseline incidence (3·4 per 100 000, 95% CI 2·9-4·0), the likely true 2015 incidence declined 44%. Large gaps in data completeness are slowly closing. During the period 2012-2015, 723 cases were identified; 83·8% of notifications were matched to hospitalisation data, and 87·2% of hospitalisations matched to notifications. Despite this improvement, clinicians need to remain aware of the need to notify atypical patients. A possible unintended consequence of the national ARF prevention programme is increased misdiagnosis.

Did exposure to a severe outbreak of pandemic influenza in 1918 impact on long-term survival?

There is some suggestion that infection with pandemic influenza may increase long-term mortality risks. Therefore we aimed to determine if exposure to a severe outbreak of pandemic influenza on a troopship in 1918 impacted on lifespan in the survivors. The troopship with the outbreak cohort had 1107 personnel and the comparison cohort was from two contemporaneous troopships (1108 randomly selected personnel). Data were collected from online individual military files. The main finding was that there was no statistically significant difference in the lifespan of the outbreak cohort and the comparison cohort (means of 71·5 and 71·0 years, respectively). Indeed, the outbreak cohort was actually more likely to survive into the period from 1950 onwards (P = 0·036) and to participate in the Second World War (P = 0·043). There were no significant differences between the cohorts in terms of occupational class, but the comparison cohort had a higher proportion of rural occupations (33·3% vs. 27·0%, P < 0·001) and was very slightly older in mid-1918 (27·8 vs. 27·2 years, P = 0·028). In conclusion, this study found no support for the hypothesis that exposure to the 1918 influenza pandemic adversely impacted on the lifespan in the survivors, at least in this male and military-age population.

Estimating the risk of acute rheumatic fever in New Zealand by age, ethnicity and deprivation.

In New Zealand, efforts to control acute rheumatic fever (ARF) and its sequelae have focused on school-age children in the poorest socioeconomic areas; however, it is unclear whether this approach is optimal given the strong association with demographic risk factors other than deprivation, especially ethnicity. The aim of this study was to estimate the stratum-specific risk of ARF by key sociodemographic characteristics. We used hospitalization and disease notification data to identify new cases of ARF between 2010 and 2013, and used population count data from the 2013 New Zealand Census as our denominator. Poisson logistic regression methods were used to estimate stratum-specific risk of ARF development. The likelihood of ARF development varied considerably by age, ethnicity and deprivation strata: while risk was greatest in Maori and Pacific children aged 10-14 years residing in the most extreme deprivation, both of these ethnic groups experienced elevated risk across a wide age range and across deprivation levels. Interventions that target populations based on deprivation will include the highest-risk strata, but they will also (a) include groups with very low risk of ARF, such as non-Maori/non-Pacific children; and (b) exclude groups with moderate risk of ARF, such as Maori and Pacific individuals living outside high deprivation areas.

Risk of infection and associated influenza-like disease among abattoir workers due to two Leptospira species.

The aims of this study were to determine the annual incidence of infection with Leptospira interrogans serovar Pomona and/or Leptospira borgpetersenii serovar Hardjo and its association with influenza-like illness (ILI) in meat workers in New Zealand. Sera were collected twice, 50-61 weeks apart, from 592 workers at eight abattoirs slaughtering sheep (n = 4), cattle (n = 2) and deer (n = 2), and tested by the microscopic agglutination test for Hardjo and Pomona. Forty-nine (8·3%) participants either seroconverted or had at least a twofold increased serological titre against either serovar. The worker infection risk was higher in sheep abattoirs (11·9%) than in abattoirs processing deer (0%) or cattle (1·2%) (P < 0·01). The annualized risk of mild (ILI) or severe clinical disease attributable to the two Leptospira serovars was 2·7%. This study has demonstrated that meat workers are at substantial risk of infection and clinical disease, suggesting further investigation of infection sources and preventive measures are warranted.

Estimating rheumatic fever incidence in New Zealand using multiple data sources.

Rheumatic fever (RF) is an important public health problem in New Zealand (NZ). There are three sources of RF surveillance data, all with major limitations that prevent NZ generating accurate epidemiological information. We aimed to estimate the likely RF incidence using multiple surveillance data sources. National RF hospitalization and notification data were obtained, covering the periods 1988-2011 and 1997-2011, respectively. Data were also obtained from four regional registers: Wellington, Waikato, Hawke's Bay and Rotorua. Coded patient identifiers were used to calculate the proportion of individuals who could be matched between datasets. Capture-recapture analyses were used to calculate the likely number of true RF cases for the period 1997-2011. A range of scenarios were used to correct for likely dataset incompleteness. The estimated sensitivity of each data source was calculated. Patients who were male, Maori or Pacific, aged 5-15 years and met the Jones criteria, were most likely to be matched between national datasets. All registers appeared incomplete. An average of 113 new initial cases occurred annually. Sensitivity was estimated at 80% for the hospitalization dataset and 60% for the notification dataset. There is a clear need to develop a high-quality RF surveillance system, such as a national register. Such a system could link important data sources to provide effective, comprehensive national surveillance to support both strategy-focused and control-focused activities, helping reduce the incidence and impact of this disease. It is important to remind clinicians that RF cases do occur outside the well-characterized high-risk group.

Clinical and molecular epidemiology of community-onset invasive Staphylococcus aureus infection in New Zealand children.

Our aim was to describe the epidemiology and incidence of community-onset invasive S. aureus disease in children presenting to our hospital, and to compare the clonal complexes and virulence genes of S. aureus strains causing invasive and non-invasive disease. The virulence gene repertoire of invasive disease isolates was characterized using DNA microarray and compared with the virulence gene repertoire of non-invasive S. aureus isolates. Over the study period, 163 children had an invasive S. aureus infection. There was no difference in the distribution of clonal complexes or in the prevalence of genes encoding virulence factors between invasive and non-invasive isolates. Future research should include a strong focus on identifying the host and environmental factors that, along with organism virulence factors, are contributing to the patterns of invasive S. aureus disease observed in New Zealand.

Molecular-based surveillance of campylobacteriosis in New Zealand--from source attribution to genomic epidemiology.

Molecular-based surveillance of campylobacteriosis in New Zealand contributed to the implementation of interventions that led to a 50% reduction in notified and hospitalised cases of the country's most important zoonosis. From a pre-intervention high of 384 per 100,000 population in 2006, incidence dropped by 50% in 2008; a reduction that has been sustained since. This article illustrates many aspects of the successful use of molecular-based surveillance, including the distinction between control-focused and strategy-focused surveillance and advances in source attribution. We discuss how microbial genetic data can enhance the understanding of epidemiological explanatory and response variables and thereby enrich the epidemiological analysis. Sequence data can be fitted to evolutionary and epidemiological models to gain new insights into pathogen evolution, the nature of associations between strains of pathogens and host species, and aspects of between-host transmission. With the advent of newer sequencing technologies and the availability of rapid, high-coverage genome sequence data, such techniques may be extended and refined within the emerging discipline of genomic epidemiology. The aim of this article is to summarise the experience gained in New Zealand with molecular-based surveillance of campylobacteriosis and to discuss how this experience could be used to further advance the use of molecular tools in surveillance.

Epidemiological investigation of a Legionnaires' disease outbreak in Christchurch, New Zealand: the value of spatial methods for practical public health.

Between April and August 2005 Christchurch, New Zealand experienced an outbreak of Legionnaires' disease. There were 19 laboratory-confirmed case including three deaths. Legionella pneumophila serogroup 1 (Lpsg1) was identified as the causative agent for all cases. A case-control study indicated a geographical association between the cases but no specific common exposures. Rapid spatial epidemiological investigation confirmed the association and identified seven spatially significant case clusters. The clusters were all sourced in the same area and exhibited a clear anisotropic process (noticeable direction) revealing a plume effect consistent with aerosol dispersion from a prevailing southwesterly wind. Four out of five cases tested had indistinguishable allele profiles that also matched environmental isolates from a water cooling tower within the centre of the clusters. This tower was considered the most probable source for these clusters. The conclusion would suggest a maximum dispersal distance in this outbreak of 11·6 km. This work illustrated the value of geostatistical techniques for infectious disease epidemiology and for providing timely information during outbreak investigations.

The epidemiology of human salmonellosis in New Zealand, 1997-2008.

This study describes the epidemiology of human salmonellosis in New Zealand using notified, hospitalized and fatal cases over a 12-year period (1997-2008). The average annual incidence for notifications was 42·8/100 000 population and 3·6/100 000 population for hospitalizations. Incidence was about twice as high in summer as in winter. Rural areas had higher rates than urban areas (rate ratio 1·23, 95% confidence interval 1·22-1·24 for notifications) and a distinct spring peak. Incidence was highest in the 0-4 years age group (154·2 notifications/100 000 and 11·3 hospitalizations/100 000). Hospitalizations showed higher rates for Maori and Pacific Island populations compared to Europeans, and those living in more deprived areas, whereas notifications showed the reverse, implying that notifications are influenced by health-seeking behaviours. Salmonella Typhimurium was the dominant serotype followed by S. Enteritidis. For a developed country, salmonellosis rates in New Zealand have remained consistently high suggesting more work is needed to investigate, control and prevent this disease.

The spatial and temporal determinants of campylobacteriosis notifications in New Zealand, 2001-2007.

Despite recent improvements, New Zealand still has one of the highest per-capita incidence rates of campylobacteriosis in the world. To reduce the incidence, a thorough understanding of the epidemiology of infection is needed. This retrospective analysis of 36 000 notified human cases during a high-risk period between 2001 and 2007 explored the spatial and temporal determinants of Campylobacter notifications at a fine spatial scale in order to improve understanding of the complex epidemiology. Social deprivation was associated with a decreased risk of notification, whereas urban residence was associated with an increased risk. However, for young children rural residence was a risk factor. High dairy cattle density was associated with an increased risk of notification in two of the three regions investigated. Campylobacter notification patterns exhibit large temporal variations; however, few factors were associated with periods of increased risk, in particular temperature did not appear to drive the seasonality in campylobacteriosis.

Acute gastrointestinal illness in New Zealand: a community study.

We report the results of the New Zealand Acute Gastrointestinal Illness (AGI) Community Study, a representative cross-sectional community telephone survey of 3655 participants conducted over a 12-month period. Respondents were asked questions about vomiting and diarrhoea in the previous 4 weeks. At least one episode of diarrhoea and/or vomiting was reported by 8·6% of respondents, an incidence of 1·11 episodes/person per year. Prevalence was highest in children aged <5 years and lowest in those aged >64 years. The mean duration of illness was 2·5 days and most common symptoms were diarrhoea (82·5%), stomach cramps (75·7%), nausea (56·9%) and vomiting (49·0%). Extrapolation of the adjusted estimates indicates there are about 4·66 million episodes of AGI per year in New Zealand, nearly 1 million visits to the general medical practitioner, in excess of 300,000 courses of antibiotics being dispensed and more than 4·5 million days of paid work lost due to AGI. This represents a significant burden of disease.

Increasing hospitalizations for serious skin infections in New Zealand children, 1990-2007.

The incidence of serious skin infections in New Zealand children is significantly higher than in comparative countries. This study aimed to describe the epidemiology of these infections and identify changes in disease distribution over time. Discharge data were analysed for all children admitted to a New Zealand public hospital with a serious skin infection during the period 1990-2007. Patient and admission variables were compared between 1990-1999 and 2000-2007. The incidence of serious skin infections almost doubled from 298·0/100,000 in 1990 to 547·3/100,000 in 2007. The highest rates were observed in boys, preschool-aged children, Maori and Pacific children, those living in deprived neighbourhoods, urban areas and northern regions. Over time there were disproportionate increases in infection rates in Maori and Pacific children and children from highly deprived areas. Serious skin infections are an increasing problem for New Zealand children. Worsening ethnic and socioeconomic health inequalities may be contributing to increasing rates.

Transmissibility of 2009 pandemic influenza A(H1N1) in New Zealand: effective reproduction number and influence of age, ethnicity and importations.

The first wave of pandemic influenza A(H1N1) has subsided in New Zealand as in other southern hemisphere countries. This study aimed to estimate the effective reproduction number (R) of 2009 pandemic influenza A(H1N1) taking into account imported cases. It also aimed to show the temporal variation of R throughout the New Zealand epidemic, changes in age- and ethnicity-specific cumulative incidence, and the effect of school holidays. Using a new modelling method to account for imported cases, we have calculated the peak R during the containment phase of the pandemic as 1.55 (95% confidence interval: 1.16 to 1.86). This value is less than previously estimated in the country early in the pandemic but in line with more recent estimates in other parts of the world. Results also indicated an increase in the proportion of notifications among school-age children after the school holiday (3-19 July 2009). This finding provides support for the potential effectiveness of timely school closures, although such disruptive interventions need to be balanced against the severity of the pandemic.

A cross-sectional survey of influenza A infection and management practices in small rural backyard poultry flocks in New Zealand.

AIM: To obtain baseline data on the management of small non-commercial backyard poultry flocks, in two rural regions of New Zealand, to investigate potential transmission pathways for avian influenza (AI), and to investigate the presence of AI in these flocks. METHODS: During August-October 2006 a questionnaire was sent to 105 farms in the Bay of Plenty and Wairarapa with poultry flocks comprising fewer than 50 chickens, located near wetlands where AI virus had been detected previously in wild ducks. Information was collected on the number and species of poultry reared, opportunities for interaction between wild birds and poultry, farm biosecurity measures, and health status of poultry. Between September and November 2006, blood and tracheal/cloacal swabs were collected from poultry on a subset of 12 high-risk farms in each location. Influenza A-specific antibodies in sera were assayed using ELISA, and positive sera were further tested for the presence of H5 and H7 subtype-specific antibodies, using haemagglutination inhibition (HI) assay. The presence of influenza A virus in swabs was detected using real-time reverse transcriptase-PCR (RRT-PCR). RESULTS: Returned questionnaires were received from 54 farms. Overall, 80% had only chickens, 13% chickens and ducks, and 7% had chickens and other galliform species. Nearly all (96%) kept backyard chickens for personal consumption of eggs, with a small proportion (19%) preparing birds for the table. On surveyed farms wild waterfowl were seen on pastures (70%) and/or farm waterways (46%). Waterfowl were recorded as visiting areas where domestic birds were kept on 31% of farms. Bird litter and manure were composted (94%) or buried (6%) on-farm, as were most (82%) dead birds. During the targeted cross-sectional survey of 24 farms clinical disease was not recorded in any poultry flock. Of 309 chicken sera tested, 11 (3.6%) from five farms across both regions tested positive for influenza A antibodies. In contrast, 16/54 (30%) duck sera from three farms in the Wairarapa were positive. Avian influenza H5 and H7 subtype-specific antibodies were excluded in ELISA positive sera using HI testing, and influenza A virus was not detected using RRT-PCR. CONCLUSIONS: The study confirmed that small backyard poultry flocks located near waterfowl habitats were exposed to non-notifiable low-pathogenic AI viruses. Findings indicate a number of potential risk pathways for the transmission of AI viruses between wild birds and non-commercial poultry, and hence the need for continued surveillance for AI in backyard flocks and wild birds in New Zealand.

The disease pyramid for acute gastrointestinal illness in New Zealand.

The disease pyramid of under-ascertainment for surveillance of acute gastrointestinal illness (AGI) in New Zealand has been estimated using 2005-2007 data on notifiable diseases, a community telephone survey, and a survey of diagnostic laboratories. For each notified case of AGI there were an estimated 222 cases in the community, about 49 of which visited a general practitioner. Faecal samples were requested from about 15 of these cases, and 13 samples were provided. Of the faecal samples, pathogens were detected in about three cases. These ratios are similar to those reported in other developed countries, and provide baseline measurements of the AGI burden in the New Zealand community.