Pathogenesis and immunological response of Yersina pestis in carnivores
Date
2019
Authors
Baeten, Laurie Ann, author
Bowen, Richard A., advisor
Pabilonia, Kristy L., advisor
Huyvaert, Kathryn P., committee member
VandeWoude, Susan, committee member
Gidlewski, Thomas, committee member
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Abstract
Yersinia pestis is the causative agent of plague. The pathogen is endemic in rodent populations in the western United States where humans and other mammals become infected with this highly virulent organism when exposed to infected rodents or their fleas. Coyotes (Canis latrans) have been used in animal-based surveillance efforts for the detection of plague foci for over 40 years. Coyotes are likely exposed via flea bite or oral routes and are presumed to be refractory to the development of clinical disease. Historical data have been useful in establishing models of the geographic distribution of Y. pestis in the landscape. Because the pathological and immunological response of coyotes to Y. pestis infection had not been thoroughly characterized, I conducted experimental inoculations of captive-reared, juvenile coyotes (n=12) with Y. pestis CO92 via oral and intradermal routes. No clinical signs of disease were observed, and minimal changes were noted in body temperature, and white blood cell counts during the 7 days following exposure. Gross pathology was unremarkable and minimal histopathological changes were noted at days 3 and 7 post-inoculation. The innate immune response was characterized by a brief peak in acute phase proteins between day 2 and 5 after oral exposure but little to no response was noted in the intradermal exposure group. The humoral response to Y. pestis fraction 1 capsular protein (anti-F1) was significantly different between inoculation groups in magnitude and duration of antibody production. The anti-F1 titers were measured by passive hemagglutination assay (PHA) and animals inoculated by the intradermal route peaked at day 10 post-inoculation (range = 1:32 to 1:128) with titers remaining stable through day 84. In contrast, orally inoculated animals developed higher titers (range =1:125 to 1:1024) that remained stable through day 42. Re-challenge at day 98 post-inoculation using the same dosage and routes did not result in changes in clinical behavior, body temperature, or white blood cell counts. Anti-F1 titers in the oral challenge group produced a striking increase (up to 1:4096) within three days, whereas there was minimal to no increase in antibody response noted in the intradermal challenge group. Using western blot, the antibody profile against known immunogenic Y. pestis antigens was evaluated. In pre-infection samples, antibodies against components of the Yersinia type III secretory system (LcrV, YopD, YopH, YpkA) were detected indicating a possible mechanism for acquired resistance to plague. Post-inoculation samples were found to contain antibodies against all of the antigens in the testing profile (F1, LcrV, Pla, Pst, YopD, YopH, YpkA). Serum samples generated from this experimental trial were used to develop an enzyme-linked immunosorbent assay (ELISA) using recombinant Y. pestis antigens where isotypic immunoglobulin production (IgG, IgM) was subsequently compared to PHA. The assay was subsequently optimized for use in testing of whole blood collected from free-ranging coyotes using Nobuto filter paper strips. ELISA was also evaluated for use in the testing of other wildlife species commonly encountered in plague endemic regions. Information gathered from this experimental work may provide additional insight into the use of coyotes for plague serosurveillance programs.
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Subject
coyote
Canis latrans
serology
Yersinia pestis
experimental infection