Spatial epidemiology of Toxoplasma gondii seroprevalence in sentinel feral chickens (Gallus gallus) in Kaua‘i, Hawai‘i

Abstract

Toxoplasma gondii is a globally prevalent coccidian parasite that fatally infects a wide range of endangered avian and mammalian hosts in Hawai‘i including the Hawaiian Monk Seal (llio holo I ka uaua; Monachus schauinslandi), Hawaiian Goose (Nēnē; Branta sandvicensis) and Hawaiian Crow (‘Alalā; Corvus hawaiiensis). Thus, identifying environmental factors that predict or impact T. gondii exposure is important for mitigating disease risks. The island of Kaua‘i is a good model system to study spatial and environmental covariates of T. gondii prevalence due to (1) high landscape heterogeneity spanning a small geographical area, (2) the presence of an ideal sentinel species, the feral chicken (Gallus gallus), and (3) recent evidence that T. gondii contributes to local declines of Hawai‘i’s endemic bird and mammal species. Despite these compelling opportunities, little is known about the prevalence or distribution of T. gondii in Hawai‘i. In this study, 294 Kaua‘i feral chickens were tested for T. gondii using ELISA IgG immunoassays, of which 117 chickens (39.8%) tested seropositive – indicating infection with the parasite – and nearly every sampled site contained chickens with positive seroprevalence. Prevalence varied among the 34 sampled localities and was significantly, positively correlated with proximity to the coast. These findings reveal that T. gondii is prevalent across Kaua‘i. Furthermore, this variability offers insight to the factors that might predict T. gondii seropositivity across the landscape, and likewise predict exposure risks for endangered wildlife.