Leptospirosis in Aotearoa New Zealand: Protocol for a Nationwide Case-Control Study

Shahista Nisa; Emilie Vallee; Jonathan Marshall; Julie Collins-Emerson; Polly Yeung; Gerard Prinsen; Jeroen Douwes; Michael G Baker; Jackie Wright; Tanya Quin; Maureen Holdaway; David A Wilkinson; Ahmed Fayaz; Stuart Littlejohn; Jackie Benschop

doi:10.2196/47900

Leptospirosis in Aotearoa New Zealand: Protocol for a Nationwide Case-Control Study

JMIR Res Protoc. 2023 Jun 8:12:e47900. doi: 10.2196/47900.

Authors

Affiliations

¹ Molecular Epidemiology and Public Health Laboratory, School of Veterinary Science, Massey University, Palmerston North, New Zealand.
² EpiCentre, School of Veterinary Science, Massey University, Palmerston North, New Zealand.
³ School of Mathematical and Computational Sciences, Massey University, Palmerston North, New Zealand.
⁴ School of Social Work, Massey University, Palmerston North, New Zealand.
⁵ School of People, Environment and Planning, Massey University, Palmerston North, New Zealand.
⁶ Research Centre for Hauora and Health, Massey University, Wellington, New Zealand.
⁷ Department of Public Health, University of Otago, Wellington, New Zealand.
⁸ Enteric and Leptospira Reference Laboratory, Institute of Environmental Science and Research, Christchurch, New Zealand.
⁹ Goodfellow Unit, University of Auckland, Auckland, New Zealand.
¹⁰ College of Health, Massey University, Palmerston North, New Zealand.
¹¹ Unité Mixte de Recherche, Animal, Santé, Territoires, Risques et Ecosystèmes, Centre de coopération internationale en recherche agronomique pour le développement, Institut national de la recherche agronomique, University of Montpellier, Plateforme Technologique Cyclotron Réunion Océan Indien, Sainte-Clotilde, La Réunion, France.

PMID: 37289491
PMCID: PMC10288348
DOI: 10.2196/47900

Abstract

Background: In Aotearoa New Zealand, 90% of patients with notified leptospirosis (a zoonotic bacterial disease) have been men working in agricultural industries. However, since 2008, the epidemiology of notified cases has been gradually changing, that is, more women are affected; there are more cases associated with occupations traditionally not considered high risk in New Zealand; infecting serovars have changed; and many patients experience symptoms long after infection. We hypothesized that there is a shift in leptospirosis transmission patterns with substantial burden on affected patients and their families.

Objective: In this paper, we aimed to describe the protocols used to conduct a nationwide case-control study to update leptospirosis risk factors and follow-up studies to assess the burden and sources of leptospirosis in New Zealand.

Methods: This study used a mixed methods approach, comprising a case-control study and 4 substudies that involved cases only. Cases were recruited nationwide, and controls were frequency matched by sex and rurality. All participants were administered a case-control questionnaire (study 1), with cases being interviewed again at least 6 months after the initial survey (study 2). A subset of cases from two high-risk populations, that is, farmers and abattoir workers, were further engaged in a semistructured interview (study 3). Some cases with regular animal exposure had their in-contact animals (livestock for blood and urine and wildlife for kidney) and environment (soil, mud, and water) sampled (study 4). Patients from selected health clinics suspected of leptospirosis also had blood and urine samples collected (study 5). In studies 4 and 5, blood samples were tested using the microscopic agglutination test to test for antibody titers against Leptospira serovars Hardjo type bovis, Ballum, Tarassovi, Pomona, and Copenhageni. Blood, urine, and environmental samples were also tested for pathogenic Leptospira DNA using polymerase chain reaction.

Results: Participants were recruited between July 22, 2019, and January 31, 2022, and data collection for the study has concluded. In total, 95 cases (July 25, 2019, to April 13, 2022) and 300 controls (October 19, 2019, to January 26, 2022) were interviewed for the case-control study; 91 cases participated in the follow-up interviews (July 9, 2020, to October 25, 2022); 13 cases participated in the semistructured interviews (January 26, 2021, to January 19, 2022); and 4 cases had their in-contact animals and environments sampled (October 28, 2020, and July 29, 2021). Data analysis for study 3 has concluded and 2 manuscripts have been drafted for review. Results of the other studies are being analyzed and the specific results of each study will be published as individual manuscripts..

Conclusions: The methods used in this study may provide a basis for future epidemiological studies of infectious diseases.

International registered report identifier (irrid): DERR1-10.2196/47900.

Keywords: Indigenous health; Leptospira; New Zealand; One Health; case-control study; leptospirosis; mixed methods; protocol; public health.

©Shahista Nisa, Emilie Vallee, Jonathan Marshall, Julie Collins-Emerson, Polly Yeung, Gerard Prinsen, Jeroen Douwes, Michael G Baker, Jackie Wright, Tanya Quin, Maureen Holdaway, David A Wilkinson, Ahmed Fayaz, Stuart Littlejohn, Jackie Benschop. Originally published in JMIR Research Protocols (https://www.researchprotocols.org), 08.06.2023.