Dissertation
ECOLOGICAL AND BIOLOGICAL STRESS EFFECTS ON THE GROUND SQUIRREL FLEA, OROPSYLLA MONTANA (SIPHONAPTERA: CERATOPHYLLIDAE)
Doctor of Philosophy (PhD), Washington State University
01/2015
Handle:
https://hdl.handle.net/2376/111241
Abstract
Background: Transmission and persistence of Yersinia pestis, the agent of plague, depend on properties of the pathogen, fleas, vertebrate hosts, and environment. In North America the ground squirrel flea, Oropsylla montana, is the primary vector of Y. pestis. Little is known about the interactions between O. montana and the pathogen or larval resource requirements. To better understand the role of abiotic conditions, flea demographics, and larval competition in plague dynamics, I determined flea survival, fecundity and pathogen load under different conditions of temperature, relative humidity, gender, mating condition, and food resources.
Methods: To test abiotic effects on Y. pestis infectivity, O. montana fleas were reared under different temperatures, then infected with Y. pestis followed by bacterial load quantification. Further abiotic tests exposed infected fleas to high or low variation abiotic regimes for 5 weeks; mortality, fecundity, and bacterial loads determined at the conclusion. To test adult flea demographic effects, sexually dimorphic (un)mated adults were infected followed by bacterial load and mortality calculation. Finally, flea larvae were subjected to varying degrees of density and food-resource dilutions to evaluate effects on metamorphosis and adult size.
Results: Fleas experiencing stress from abiotic changes had higher bacterial loads and laid fewer eggs than fleas under less extreme or dynamic conditions. Overall, survival was greater at lower temperatures. A higher proportion of unmated females survived than other gender and mating treatments and bacterial loads were higher in females but did not differ between like sexes in either unmated or mated fleas. No larval density or resource dilutions tested affected the number of F1 generation adults, but the lowest food dilutions resulted in smaller adult females.
Conclusions: Fleas under stress from abiotic changes had increased Y. pestis growth, reduced fecundity, and unpredictable mortality. This implies that flea and pathogen microclimate variation has a significant effect upon Y. pestis prevalence in the environment, possibly increasing plague risk due to global climate change. Also, female fleas have a greater role in plague transmission due to increased bacterial development. Finally, food resource requirements of O. montana larvae are extremely minimal and likely have little effect upon flea population size.
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Details
- Title
- ECOLOGICAL AND BIOLOGICAL STRESS EFFECTS ON THE GROUND SQUIRREL FLEA, OROPSYLLA MONTANA (SIPHONAPTERA: CERATOPHYLLIDAE)
- Creators
- Adam Strong
- Contributors
- Jeb Owen (Advisor)Viveka Vadyvaloo (Committee Member)Glen Scoles (Committee Member)William Snyder (Committee Member)
- Awarding Institution
- Washington State University
- Academic Unit
- Entomology, Department of
- Theses and Dissertations
- Doctor of Philosophy (PhD), Washington State University
- Number of pages
- 80
- Identifiers
- 99900581731701842
- Language
- English
- Resource Type
- Dissertation