The use of omics for disease evaluation in the brains of marine mammals
Marine mammals are top predators that are essential for the health and function of our oceans. These top predators are often affected by various factors that can be detrimental to their populations. Therefore, there is a need to evaluate undetermined causes of deaths and to better understand known d...
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| Other Authors: | , , , , , , |
| Format: | Doctoral or Postdoctoral Thesis |
| Language: | English unknown |
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Oregon State University
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| Online Access: | https://ir.library.oregonstate.edu/concern/graduate_thesis_or_dissertations/zw12z8093 |
| Summary: | Marine mammals are top predators that are essential for the health and function of our oceans. These top predators are often affected by various factors that can be detrimental to their populations. Therefore, there is a need to evaluate undetermined causes of deaths and to better understand known diseases in marine mammals to mitigate future marine mammal mortality events. In this dissertation, I examined a mortality event that occurred in 2009 and affected seven harbor seals that died from an unknown brain disease. In 2009, a cohort of harbor seals stranded along the California coastline and the necropsies of these animals showed necrosis in the cerebrum and cerebellum. However, the etiology of the disease could not be determined with conventional diagnostic procedures. The results from the necropsy reports suggested that a virus was the likely causative agent, although it was also noted that exposure to a toxin, nutrient depletion, or hypoxia could have also caused the death of these animals. To investigate the source of this stranding event I compared the brain tissues of these harbor seals, that I termed “unknown cause of death” (UCD), to the brain tissues of seven other harbor seals with known causes of death that I termed “comparative” samples. Given that UCD animals were hypothesized to have died from an unknown virus type, I used meta-transcriptomics analysis of the brains to assess the presence of gene expression patterns from DNA/RNA viruses and opportunistic bacteria. Upon evaluation of the UCD animals, I found that there was no indication that viruses were present in the brain tissue of these animals. However, I did find the presence of a previously described Phocine herpesvirus-1 (PhV-1) in 57% of comparative harbor seal samples. Interestingly, the microbiome analysis of the UCD animals showed two significantly abundant bacteria types, Burkholderia cepacia complex (BCC) and Coxiella burnetii. BCC was prevalent in all UCDs, which expressed a significant abundance of BCC virulence factors relative to ... |
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