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Author: search.filters.author.Collins-Emerson JSubject: search.filters.subject.Leptospira

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    Genotyping Reveals Potential Sources of Human Leptospirosis Outbreaks in Aotearoa New Zealand
    (Wiley-VCH GmbH, 2026-02-01) Nisa S; Littlejohn S; Fayaz A; Deen S; Sokolova M; Ogbuigwe P; Moinet M; Cookson AL; Collins-Emerson J; Niebuhr CN; Vallee EM; Marshall J; Benschop J
    Introduction: The introduction of PCR testing for leptospirosis in Aotearoa New Zealand has reduced the availability of serotyping data, and current diagnostic PCRs do not routinely genotype Leptospira. This study genotyped Leptospira from PCR-confirmed human cases between 2016 and 2023 and compared them with genotypes found in animals to identify potential sources of infection in a 2023 human leptospirosis outbreak. Methods: Human samples were genotyped using glmU amplicon sequencing and compared to animal genotypes from previous studies. In addition, human national surveillance data were analysed to provide broader epidemiological context including regional distribution to reveal outbreak areas; diagnostic test usage to assess trends; serotyping results to evaluate consistency across methods; and demographic information to evaluate the representativeness of the genotyped dataset. Chi-squared and Poisson regression were used to assess host-genotype associations, and phylogenetics evaluated genetic relatedness. Results: Surveillance data showed flood-associated outbreaks in several regions and a significant shift in diagnostic practice (p ≤ 0.001), with increased use of PCR. Genotyping of PCR-confirmed cases revealed a rise in Pomona infections in 2023 across rural flood-associated regions (Gisborne, Hawke's Bay, Manawatū-Whanganui, Waikato and Wairarapa). In contrast, the Auckland region—including Aotearoa's largest city which also experienced flooding—had infections linked to Ballum, Copenhageni and Balcanica NZ. In animals, Pomona was primarily detected in sheep (Ovis aries), followed by cattle, while Ballum, Copenhageni and Balcanica NZ were primarily detected in mice (Mus musculus), Norway rats (Rattus norvegicus) and brushtail possums (Trichosurus vulpecula), respectively. Conclusions: Flooding-driven outbreaks in rural areas with pastoral livestock were predominantly linked to livestock-associated strains, while urban cases were associated with rodents and small wildlife. These findings highlight the need for tailored mitigation strategies addressing distinct epidemiological risks in rural and urban settings. Surveillance strategies should be adapted to preserve typing capabilities to better inform public health responses in future outbreaks.
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    A cross-sectional investigation of Leptospira at the wildlife-livestock interface in New Zealand
    (PLOS, 2023-09-06) Moinet M; Oosterhof H; Nisa S; Haack N; Wilkinson DA; Aberdein D; Russell JC; Vallée E; Collins-Emerson J; Heuer C; Benschop J; Stevenson B
    There has been a recent upsurge in human cases of leptospirosis in New Zealand, with wildlife a suspected emerging source, but up-to-date knowledge on this topic is lacking. We conducted a cross-sectional study in two farm environments to estimate Leptospira seroprevalence in wildlife and sympatric livestock, PCR/culture prevalence in wildlife, and compare seroprevalence and prevalence between species, sex, and age groups. Traps targeting house mice (Mus musculus), black rats (Rattus rattus), hedgehogs (Erinaceus europaeus) and brushtail possums (Trichosurus vulpecula) were set for 10 trap-nights in March-April 2017 on a dairy (A) and a beef and sheep (B) farm. Trapped wild animals and an age-stratified random sample of domestic animals, namely cattle, sheep and working dogs were blood sampled. Sera were tested by microagglutination test for five serogroups and titres compared using a Proportional Similarity Index (PSI). Wildlife kidneys were sampled for culture and qPCR targeting the lipL32 gene. True prevalence in mice was assessed using occupancy modelling by collating different laboratory results. Infection profiles varied by species, age group and farm. At the MAT cut-point of ≥ 48, up to 78% of wildlife species, and 16-99% of domestic animals were seropositive. Five of nine hedgehogs, 23/105 mice and 1/14 black rats reacted to L. borgpetersenii sv Ballum. The sera of 4/18 possums and 4/9 hedgehogs reacted to L. borgpetersenii sv Hardjobovis whilst 1/18 possums and 1/9 hedgehogs reacted to Tarassovi. In ruminants, seroprevalence for Hardjobovis and Pomona ranged 0-90% and 0-71% depending on the species and age group. Titres against Ballum, Tarassovi and Copenhageni were also observed in 4-20%, 0-25% and 0-21% of domestic species, respectively. The PSI indicated rodents and livestock had the most dissimilar serological responses. Three of nine hedgehogs, 31/105 mice and 2/14 rats were carrying leptospires (PCR and/or culture positive). True prevalence estimated by occupancy modelling in mice was 38% [95% Credible Interval 26, 51%] on Farm A and 22% [11, 40%] on Farm B. In the same environment, exposure to serovars found in wildlife species was commonly detected in livestock. Transmission pathways between and within species should be assessed to help in the development of efficient mitigation strategies against Leptospira.