Neisseria meningitidis - Eurosurveillance

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Perspectives Molecular-based surveillance of campylobacteriosis in New Zealand – from source attribution to genomic epidemiology P Muellner (petra@epi-interactive.com) 1,2 , E Pleydell 2 , R Pirie 3 , M G Baker 4 , D Campbell 5 , P E Carter 3 , N P French 2 1. Epi-interactive, Miramar, Wellington, New Zealand 2. mEpiLab, Institute of Animal, Biomedical and Veterinary Science, Massey University, Palmerston North, New Zealand 3. Institute of Environmental Science and Research, Kenepuru Science Centre, Porirua, New Zealand 4. Department of Public Health, University of Otago, Wellington, New Zealand 5. Ministry for Primary Industries, Wellington, New Zealand Citation style for this article: Muellner P, Pleydell E, Pirie R, Baker MG, Campbell D, Carter PE, French NP. Molecular-based surveillance of campylobacteriosis in New Zealand – from source attribution to genomic epidemiology. Euro Surveill. 2013;18(3):pii=20365. Available online: http://www.eurosurveillance.org/ViewArticle.aspx?ArticleId=20365 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 strategyfocused 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. Controlling campylobacteriosis – recent successes Molecular tools are being used increasingly to inform the control of enteric zoonosis worldwide [1] and to meet a wide range of public health aims and objectives [2-4]. In New Zealand, a country with a historically high rate of campylobacteriosis notifications [5,6], results from molecular-based surveillance in a sentinel site founded in 2005 – where human cases and potential sources were sampled and typed by multilocus sequence typing (MLST) simultaneously over Article submitted on 27 June 2012 / published on 17 January 2013 consecutive years [7,8] – provided strong evidence that a large proportion of human cases were linked poultry meat consumption. These findings contributed to a mounting body of evidence [5,9] and stimulated the implementation of regulatory and voluntary control strategies along the poultry supply chain. They were announced in 2007 and fully implemented in 2008 (when they became mandatory) [10], resulting in a 50% reduction in disease incidence of cases in 2008 compared with the previous high level during 2002 to 2006 [10,11]. Campylobacteriosis notifications in humans were markedly above the reference value until 2008, when the incidence dropped considerably (Figure 1); a likely effect of a reduction in poultry-associated cases due to the implementation of the control strategies in the poultry supply chain [10,11]. No comparable changes in the annual incidence of other enteric notifiable diseases were observed over the same time period (2002–2011) (Figure 1). Sustained decline in campylobacteriosis case numbers has been shown to have additional health and economic benefits by, for example reducing the incidence of Guillain–Barré syndrome, an autoimmune condition associated with prior Campylobacter spp. infection [12]. Furthermore, in the New Zealand sentinel surveillance site, a dominant poultry-associated MLST sequence type of C. jejuni (ST-474) was identified that, to date, has been reported rarely from other countries. Before the implementation of the poultry interventions, ST-474 accounted for 30% of human cases in the sentinel site [14,15], but in 2010–11, it was isolated from less than 5% of cases [16]. Figure 2 shows the dramatic reduction in two major poultry-associated genotypes, ST-474 and ST-48 (Figure 2, panel A), and provides a comparison with other STs over the same time period (Figure 2, panels B and C). 110 www.eurosurveillance.org
Figure 1 Relative rates a of notification of campylobacteriosis, cryptosporidiosis, salmonellosis and yersiniosis, New Zealand, 2002–2011 compared with 1999–2001 Relative rate (log scale) 2.0 1.5 1.0 0.5 a Rates were calculated using a negative binomial model, which was used to estimate the change in incidence between each year from 2002 to 2011 and the reference period of interest, 1999–2001, as previously described by Henao et al. [13]. Values above the reference line indicate increases in notification incidence and points below the line show decreases, relative to the 1999–2001 reference period. The pre- and post-intervention periods refer to the implementation of a number of control measures in the poultry supply chain by the regulatory authority. The annual incidence of other enteric notifiable diseases (cryptosporidiosis, salmonellosis and yersiniosis) over the same time period is displayed to show that notification rates were stable for other comparable disease and that the drop in campylobacteriosis notifications was not a surveillance artefact. Focused molecular epidemiological studies have been contributing to our understanding of the epidemiology of this widespread disease both in New Zealand and elsewhere [7,14,15,17]. For example, the association between ruminant-associated genotypes and preschool-age children (0–5 years of age) in rural areas has provided evidence for direct contact with faecal material being the foremost infection route in this high-incidence group [14]. This is of high relevance for the development and evaluation of appropriate, country-specific control strategies to decrease the human disease burden. Since the number of human cases linked to poultry has fallen in New Zealand, there has been a relative increase in importance of ruminant strains of C. jejuni, and ongoing work is investigating the complex epidemiology of Campylobacter in ruminant [18] and wildlife sources [19]. While this article describes the MLST-supported Campylobacter surveillance conducted at the sentinel site, other typing approaches are used to increase resolution of the molecular analysis. For example, research is currently underway to further differentiate between www.eurosurveillance.org Pre-intervention period Post-intervention period 1999−2001 2002 2003 2004 2005 2006 2007 2008 2009 2010 2011 Year Campylobacteriosis Cryptosporidiosis Salmonellosis Yersiniosis exposure to ruminant-associated Campylobacter subtypes of food and non-food origin to refine attribution estimates using antigen gene sequence typing [20], ribosomal MLST [21] and targeted genes identified by whole genome analysis [22]. In this article, we summarise the experience gained in New Zealand and discuss how this experience could be used to further advance the use of molecular tools in surveillance. What have we learned? Experience from New Zealand and elsewhere has provided insight into key aspects of molecular-based surveillance. These include the following: (i) its application to both control-focused and strategy-focussed surveillance; (ii) a change in our definition of epidemiological response variables; and (iii) the emergence of genomic epidemiology. Application of molecular tools to disease surveillance The framework developed by Baker et al. [23], which differentiates between control-focused and strategyfocused surveillance, provides a meaningful way to 111
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Editorial team Editorial advisors B
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genome sequencing technologies, we
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References 1. Struelens MJ, De Ghel
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microorganisms [23]. After PCR, amp
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from: http://www.eurosurveillance.o
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Table 1 Online molecular typing dat
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Table 2 Currently available softwar
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Current concepts and technologies f
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References 1. Hesper B, Hogeweg P.
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Review articles Automated extractio
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diverse organisms, such as the meni
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Figure 3 Relationships of 139 Neiss
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