Browsing by Author "Thomason, Courtney A."

Now showing 1 - 4 of 4
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    Experimental logging alters the abundance and community composition of ovipositing mosquitoes in the southern Appalachians
    Hopkins, M. Camille; Thomason, Courtney A.; Brown, Bryan L.; Kirkpatrick, Laila T.; Paulson, Sally L.; Hawley, Dana M. (2018-08)
    1. The loss of intact forest via logging can influence vector-borne disease dynamics in part by altering the abundance or diversity of mosquito species. Using an experimental field approach, we characterised how two types of logging (clearcut and repeat-entry shelterwood) affected temperate forest mosquito abundance and diversity in southwestern Virginia. 2.From May to September in 2008-2010, infusion-baited gravid traps were used to collect ovipositing female mosquitoes across experimental forest plots that varied in logging treatment. Of the 29680 collected adult female mosquitoes, the three dominant taxa captured were Aedes triseriatus (55%), Aedes japonicus (21%), and Culex pipiens/restuans (20%). 3. Logging treatment had a significant effect on the overall number of female mosquitoes caught per trap night, with lower average abundance of females on both logged treatments relative to two types of unlogged, control plots. When the three most abundant mosquito species were examined separately, logging treatment significantly influenced the abundance of both Aedes species, but did not significantly affect C. pipiens/restuans abundance. 4. Logging treatment did not influence the richness or diversity of mosquito species captured in gravid traps. However, logging treatment significantly altered the multivariate community composition of captured mosquitoes, an effect probably mediated by differential species-specific impacts of logging on abundance. 5. Overall, the results of the present study suggest that the risk of arboviruses transmitted by container-breeding Aedes species may be lower following a logging event in Appalachian forests because of reduced A. japonicus and A. triseriatus abundance with logging.
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    Experimental parasite community perturbation reveals associations between Sin Nombre virus and gastrointestinal nematodes in a rodent reservoir host
    Sweeny, Amy R.; Thomason, Courtney A.; Carbajal, Edwin A.; Hansen, Christina B.; Graham, Andrea L.; Pedersen, Amy B. (2020-12-23)
    Individuals are often co-infected with several parasite species, yet measuring within-host interactions remains difficult in the wild. Consequently, the impacts of such interactions on host fitness and epidemiology are often unknown. We used anthelmintic drugs to experimentally reduce nematode infection and measured the effects on both nematodes and the important zoonosis Sin Nombre virus (SNV) in its primary reservoir (Peromyscus spp.). Treatment significantly reduced nematode infection, but increased SNV seroprevalence. Furthermore, mice that were co-infected with both nematodes and SNV were in better condition and survived up to four times longer than uninfected or singly infected mice. These results highlight the importance of investigating multiple parasites for understanding interindividual variation and epidemiological dynamics in reservoir populations with zoonotic transmission potential.
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    High virulence is associated with pathogen spreadability in a songbird–bacterial system
    Hawley, Dana M.; Thomason, Courtney A.; Aberle, Matthew A.; Brown, Richard; Adelman, James S. (Royal Society Publishing, 2023-01-11)
    How directly transmitted pathogens benefit from harming hosts is key to understanding virulence evolution. It is recognized that pathogens benefit from high within-host loads, often associated with virulence. However, high virulence may also directly augment spread of a given amount of pathogen, here termed ‘spreadability’. We used house finches and the conjunctival pathogen Mycoplasma gallisepticum to test whether two components of virulence—the severity of conjunctival inflammation and behavioural morbidity produced—predict pathogen spreadability. We applied ultraviolet powder around the conjunctiva of finches that were inoculated with pathogen treatments of distinct virulence and measured within-flock powder spread, our proxy for ‘spreadability’. When compared to uninfected controls, birds infected with a high-virulence, but not low-virulence, pathogen strain, spread significantly more powder to flockmates. Relative to controls, highvirulence treatment birds both had more severe conjunctival inflammation—which potentially facilitated powder shedding—and longer bouts on feeders, which serve as fomites. However, food peck rates and displacements with flockmates were lowest in high-virulence treatment birds relative to controls, suggesting inflammatory rather than behavioural mechanisms likely drive augmented spreadability at high virulence. Our results suggest that inflammation associated with virulence can facilitate pathogen spread to conspecifics, potentially favouring virulence evolution in this system and others.
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    Resident Microbiome Disruption with Antibiotics Enhances Virulence of a Colonizing Pathogen
    Thomason, Courtney A.; Mullen, Nathan; Belden, Lisa K.; May, Meghan; Hawley, Dana M. (Springer Nature, 2017-11-23)
    There is growing evidence that symbiotic microbes play key roles in host defense, but less is known about how symbiotic microbes mediate pathogen-induced damage to hosts. Here, we use a natural wildlife disease system, house finches and the conjunctival bacterial pathogen Mycoplasma gallisepticum (MG), to experimentally examine the impact of the ocular microbiome on host damage and pathogen virulence factors during infection. We disrupted the ocular bacterial community of healthy finches using an antibiotic that MG is intrinsically resistant to, then inoculated antibiotic and sham-treated birds with MG. House finches with antibiotic-disrupted ocular microbiomes had more severe MG-induced conjunctival inflammation than birds with unaltered microbiomes, even after accounting for differences in conjunctival MG load. Furthermore, MG cultures from finches with disrupted microbiomes had increased sialidase enzyme and cytadherence activity, traits associated with enhanced virulence in Mycoplasmas, relative to isolates from sham-treated birds. Variation in sialidase activity and cytadherence among isolates was tightly linked with degree of tissue inflammation in hosts, supporting the consideration of these traits as virulence factors in this system. Overall, our results suggest that microbial dysbiosis can result in enhanced virulence of colonizing pathogens, with critical implications for the health of wildlife, domestic animals, and humans.