Environmental contamination with canine soil-transmitted helminths in New Zealand urban areas: A nationwide molecular, spatial, and risk factor analysis survey.

Urban parks and recreational areas are frequent gathering sites for dogs and their owners, where dog waste creates sources for pathogens of veterinary and zoonotic concern. Canine soil-transmitted helminths (cSTHs) such as hookworms (Ancylostoma spp. and Uncinaria stenocephala), roundworms (Toxocara canis and Toxascaris leonina), whipworms (Trichuris vulpis), and threadworms (Strongyloides stercoralis), are recognised for their ability to cause gastrointestinal disease and other health issues in dogs. In addition, some species are known for being zoonotic and cause potentially life-threatening conditions in humans. In an exploratory investigation performed in 2023, canine faecal samples were collected from 16 areas across five regions in New Zealand and screened using antigen-based tests, revealing that overall, 31.3% (95% CI 14.2-55.6) of areas were contaminated with at least one parasite, with 7.1% (95% CI 3.3-14.6) and 3.5% (95% CI 1.2-9.9) of individual samples testing positive for roundworms and whipworms, respectively. In a subsequent nationwide survey in 2024, 739 canine faecal samples were collected from 123 urban areas across New Zealand and analysed using multiplex real-time PCRs. Positive samples were further genetically characterised by Sanger and nanopore sequencing. Overall, 24.4% (95% CI 17.7-32.7) of areas tested positive for at least one cSTH, most commonly Ancylostoma caninum (12.2%, 95% CI 7.5-19.1), followed by Uncinaria stenocephala (9.8%, 95% CI 5.7-16.3), T. canis (3.3%, 95% CI 1.3-8.1), and T. vulpis (1.6%, 95% CI 0.4-5.7), whilst Ancylostoma ceylanicum and S. stercoralis were not detected. Logistic regression analyses identified dog density, proximity to city centres, and bioclimatic zone, as predictors of cSTHs contamination in urban areas. This study provides in depth information on the molecular identity and spatial distribution of cSTHs in New Zealand's urban areas and contributes to understanding environmental exposure risk to support parasite surveillance and control in companion animals.