Epidemiology and temporal trends of gastrointestinal parasites and vector-borne pathogens in golden retriever dogs: an eight-year cohort study

Longitudinal studies evaluating gastrointestinal parasites and vector-borne pathogens in companion dogs are relatively uncommon despite their importance for animal health, veterinary public health, and One Health surveillance. This study investigated the cumulative occurrence, incidence rates, and temporal trends of gastrointestinal parasites and vector-borne pathogens among Golden Retrievers enrolled in the Golden Retriever Lifetime Study (GRLS). A retrospective longitudinal analysis was conducted using publicly available GRLS data collected across eight annual study years (study years 0–7). Following data cleaning and consolidation of duplicate dog-year observations, the final analytical dataset comprised 24,352 unique dog-year observations from 3,044 dogs. Cumulative occurrence and incidence rates per 1,000 dog-years at risk were estimated. Temporal trends were assessed using Mann–Kendall trend tests and Sen’s slope estimation. Logistic regression and generalized estimating equation (GEE) models were performed as complementary analyses. Giardia demonstrated the highest cumulative occurrence (9.10%), followed by roundworms (8.21%), coccidia (5.45%), and Lyme disease (4.73%). Lyme disease exhibited the highest incidence rate (4.22 cases per 1,000 dog-years), followed by Giardia (3.31), Anaplasma spp. (3.09), and hookworms (2.97). Significant increasing temporal trends were identified for Giardia , roundworms, Lyme disease, Anaplasma spp. coccidia , hookworms, Ehrlichia. spp., Eimeria , Rocky Mountain spotted fever (RMSF), tapeworms, whipworms, and leptospirosis (all p < 0.05). Sensitivity analyses yielded findings consistent with the primary analyses. Multiple pathogens showed increasing detection frequencies during the follow-up period; however, we cannot attribute these increases to genuine epidemiological changes versus aging cohort effects, testing practice changes, or other unmeasured factors. These findings highlight the need for multivariate analyses incorporating demographic and environmental covariates to clarify mechanism.