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Still 'dairy farm fever'? A Bayesian model for Leptospirosis notification data in New Zealand
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Benschop, Jackie, Nisa, Shahista and Spencer, Simon E. F. (2021) Still 'dairy farm fever'? A Bayesian model for Leptospirosis notification data in New Zealand. Journal of The Royal Society Interface, 18 (175). 20200964. doi:10.1098/rsif.2020.0964 ISSN 1742-5689.
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WRAP-still-dairy-farm-fever-Bayesian-model-Leptospirosis-notification-data-New-Zealand-Spencer-2021.pdf - Accepted Version Embargoed item. Restricted access to Repository staff only - Requires a PDF viewer. Download (833Kb) |
Official URL: https://doi.org/10.1098/rsif.2020.0964
Abstract
Routinely collected public health surveillance data are often partially complete, yet remain a useful source by which to monitor incidence and track progress during disease intervention. In the 1970s, leptospirosis in New Zealand (NZ) was known as ‘dairy farm fever’ and the disease was frequently associated with serovars Hardjo and Pomona. To reduce infection, interventions such as vaccination of dairy cattle with these two serovars was implemented. These interventions have been associated with significant reduction in leptospirosis incidence, however, livestock-based occupations continue to predominate notifications. In recent years, diagnosis is increasingly made by nucleic acid detection which currently does not provide serovar information. Serovar information can assist in linking the recognized maintenance host, such as livestock and wildlife, to infecting serovars in human cases which can feed back into the design of intervention strategies. In this study, confirmed and probable leptospirosis notification data from 1 January 1999 to 31 December 2016 were used to build a model to impute the number of cases from different occupational groups based on serovar and month of occurrence. We imputed missing occupation and serovar data within a Bayesian framework assuming a Poisson process for the occurrence of notified cases. The dataset contained 1430 notified cases, of which 927 had a specific occupation (181 dairy farmers, 45 dry stock farmers, 454 meatworkers, 247 other) while the remaining 503 had non-specified occupations. Of the 1430 cases, 1036 had specified serovars (231 Ballum, 460 Hardjo, 249 Pomona, 96 Tarassovi) while the remaining 394 had an unknown serovar. Thus, 47% (674/1430) of observations had both a serovar and a specific occupation. The results show that although all occupations have some degree of under-reporting, dry stock farmers were most strongly affected and were inferred to contribute as many cases as dairy farmers to the burden of disease, despite dairy farmer being recorded much more frequently. Rather than discard records with some missingness, we have illustrated how mathematical modelling can be used to leverage information from these partially complete cases. Our finding provides important evidence for reassessing the current minimal use of animal vaccinations in dry stock. Improving the capture of specific farming type in case report forms is an important next step.
Item Type: | Journal Article | ||||||||||||
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Alternative Title: | |||||||||||||
Subjects: | Q Science > QA Mathematics R Medicine > RA Public aspects of medicine S Agriculture > SF Animal culture |
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Divisions: | Faculty of Science, Engineering and Medicine > Science > Mathematics | ||||||||||||
Library of Congress Subject Headings (LCSH): | Markov processes , Monte Carlo method, Epidemiology -- Statistical methods, Leptospirosis in animals -- New Zealand, Leptospirosis in animals -- Mathematical models | ||||||||||||
Journal or Publication Title: | Journal of The Royal Society Interface | ||||||||||||
Publisher: | The Royal Society Publishing | ||||||||||||
ISSN: | 1742-5689 | ||||||||||||
Official Date: | 17 February 2021 | ||||||||||||
Dates: |
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Volume: | 18 | ||||||||||||
Number: | 175 | ||||||||||||
Article Number: | 20200964 | ||||||||||||
DOI: | 10.1098/rsif.2020.0964 | ||||||||||||
Status: | Peer Reviewed | ||||||||||||
Publication Status: | Published | ||||||||||||
Access rights to Published version: | Open Access (Creative Commons) | ||||||||||||
Copyright Holders: | © 2021 The Authors | ||||||||||||
Date of first compliant deposit: | 22 January 2021 | ||||||||||||
Date of first compliant Open Access: | 17 February 2021 | ||||||||||||
RIOXX Funder/Project Grant: |
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