Date of Conferral

7-29-2026

Date of Award

July 2026

Degree

Ph.D.

School

Health Sciences

Advisor

German Gonzalez

Abstract

Highly Pathogenic Avian Influenza (HPAI) H5N1 threatens agriculture, wildlife, and public health in California, where flooded rice fields in the Central Valley provide surrogate wetland habitat for migratory waterfowl and may create ecological interfaces for viral spillover into poultry systems. This quantitative ecological study examined whether county-level rice acreage, Lesser Snow Goose activity, and their interaction were associated with poultry HPAI H5N1 outbreak incidence during complete winter seasons available for analysis. Guided by One Health and disease ecology frameworks, secondary data from USDA, eBird, PRISM, and public surveillance sources were analyzed for 36 county-winter observations using negative binomial regression, logistic sensitivity models, and GIS-based spatial overlays. Adjusted models found no statistically significant associations for rice acreage (RR = 0.75, 95% CI [0.45, 1.25], p = .271), Snow Goose activity (RR = 1.10, 95% CI [0.60, 2.03], p = .762), or their interaction (RR = 1.47, 95% CI [0.57, 3.82], p = .426). However, descriptive and GIS analyses showed increasing outbreak counts from 3 in 2022–2023 to 31 in 2024–2025 among rice-producing counties, with spatial convergence of rice agriculture, Snow Goose activity, poultry inventory, wild-bird detections, and outbreak burden. These results suggest county-level data may be too coarse to detect fine-scale transmission pathways but highlight areas of ecological overlap that can inform targeted surveillance and One Health preparedness.

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