Molecular Epidemiology and Spatial Distribution of Toxocara canis and Toxocara cati in Avian Paratenic Hosts: A One Health Perspective From Northeastern Iran

BACKGROUND: Toxocara canis and Toxocara cati are zoonotic nematodes, and birds may contribute to their transmission as paratenic hosts. Data on their molecular occurrence in avian hosts remain limited in northeastern Iran. OBJECTIVE: This study investigated the molecular detection and spatial distribution of T. canis and T. cati in synanthropic and domestic birds from Razavi Khorasan Province. METHODS: In this cross-sectional study, 300 tissue samples (brain, eye and liver) were collected from 100 birds: sparrows (n = 60), pigeons (n = 21) and chickens (n = 19). Detection and species identification were performed using multiplex nested PCR targeting ITS regions. Spatial patterns were assessed using kernel density estimation and Global Moran's I in ArcGIS 10.8. Associated factors were analysed by multivariable mixed-effects logistic regression. RESULTS: Toxocara spp. DNA was detected in 51/300 tissues (17.0%) and 35/100 birds (35.0%). Tissue-level positivity was highest in sparrows (23.3%), followed by chickens (8.8%) and pigeons (6.3%). In sparrows, detection differed among tissues (p = 0.026), with higher positivity in eye and liver. T. canis predominated (68.6%), followed by mixed infections (17.7%) and T. cati (13.7%). Bird species and tissue type were independently associated with PCR positivity. Kernel Density Estimation suggested localised southern and southeastern hotspots, whereas Global Moran's I showed a non-significant random spatial pattern. CONCLUSIONS: Synanthropic and domestic birds, particularly sparrows, may act as paratenic hosts for Toxocara spp. in northeastern Iran. Higher detection in eye and liver tissues suggests zoonotic relevance, especially through undercooked poultry giblets; however, DNA detection does not confirm larval viability.