A Formalin Fixation…..
All of the formalin-fixed tissues from subsistence harvested seals and walruses taken during the 2010 harvest require trimming in preparation for paraffin-embedding, sectioning and standard H & E staining. I spent the last week of my summer in Barrow trimming and making over 1,000 tissue blocks from the seals and walruses sampled in 2010. These blocks will be made into slides at the Colorado State University Diagnostic Medicine Center and read by me under the direct supervision of Terry R. Spraker, DACVP and noted marine mammal pathology expert. The subsistence hunters have been so kind and generous letting me collect tissues from their seals and walruses. They are most supportive of research that documents the health of these important subsistence resources. Furthermore, their willingness to let us collect tissues from these animals is allowing us to develop an appreciation and understanding of the gross anatomy and microscopic attributes of Arctic marine mammals. These 3 cassettes contain tissues from 2010RS8. From left to right, the first cassette contains skin and vibrissae, the second cassette contains a section of liver, and the third cassette contains a section of trachea and a section of liver. The gross changes in the liver are consistent with a parasitic infection caused by a fluke. There is severe, chronic fibrosis of the bile ducts associated with this fluke infection.
Here are some photomicrographs from my work…..
These two photos are sections of liver from a bearded seal with a heavy fluke infection caused by Orthosplanchnus arcticus. The life cycle is likely complicated and may involve multiple intermediate hosts, one of them likely being a fecal feeding fish. It is amazing that the definitive host, the bearded seal has adapted quite well to the presence of this parasite. Histologically, there is severe cholangitis and cholangiohepatitis caused by the fluke.
This photo is a section of lung from a ringed seal. This low magnification photo illustrates histopathological changes associated with heartworm infection. Yes, even seals get heartworm! There is severe fibrointimal and fibromuscular proliferation of the medium-sized arteries in the lung caused by the seal heartworm, Anchanthocheilonema spiracauda. Although this ringed seal and the numerous other subsistence harvested ringed seals that have lung pathology associated with heartworm infection did not die from heartworm disease, heartworm is a significant cause of mortality in juvenile ringed seals.