Doctoral Dissertations
Date of Award
12-2024
Degree Type
Dissertation
Degree Name
Doctor of Philosophy
Major Professor
Richard W. Gerhold
Committee Members
John J. Schaefer, Michelle Dennis, Chunlei Su, Bradley C. Cohen
Abstract
Toxoplasma gondii is an apicomplexan protozoan parasite that infects mammals, including humans, and avian species. The spectrum of clinical disease is wide and ranges from asymptomatic/subclinical to systemic disease that can be fatal. It has been widely investigated in many domestic and wild species, but little is known about its prevalence and impact on North American waterfowl. This work aims to examine Toxoplasma’s serologic and molecular prevalence in waterfowl species in the United States, to better understand its effect on the immune response, clinical disease, and tissue tropism in wild ducks, and to investigate its potential relationship with another zoonotic pathogen, avian influenza virus.
Hunter-harvested and wildlife management-collected samples of duck and goose serum or ‘meat juices’ and hearts from Arkansas, Minnesota, North Dakota, Pennsylvania, and Tennessee were evaluated via the modified agglutination test (MAT) for seropositivity for toxoplasmosis. DNA was extracted from the hearts and molecularly tested for T. gondii DNA using the B1 gene as a primer target. Overall, 218 of the 736 (29.7%) serum/‘meat juice’ samples were seropositive with statistically significant differences between MAT titer status and the flyway from which the sample was collected
An experimental infection of 64 Mallard ducks with two doses and two strains T. gondii tachyzoites and 10 uninfected control birds was performed to gain better insight into the Mallard’s immune response, changes in weight, and clinical signs associated with toxoplasmosis. Overall, 93.8% of the birds seroconverted, and no birds showed any clinical signs of disease throughout the study period. Histopathologically, T. gondii bradyzoites were identified in three birds in the high virulence groups with a fourth bird demonstrating characteristic inflammation of toxoplasmosis in the neural tissue but no bradyzoites were found in that tissue section.
A geographically narrowed investigation was conducted in western Tennessee looking at T. gondii seroprevalence and avian influenza status in ducks. 23.6% (139/590) of birds tested were seropositive for toxoplasmosis, and 34.9% (15/43) were positive for avian influenza virus. Only four birds were positive for both toxoplasmosis and avian influenza virus.
Recommended Citation
Szafranski, Nicole Marie, "Investigation of the prevalence, seroreactivity, tissue tropism, and epidemiology of Toxoplasma gondii in North American waterfowl species. " PhD diss., University of Tennessee, 2024.
https://trace.tennessee.edu/utk_graddiss/11389