Honors Theses and Capstones

Date of Award

Spring 2021

Project Type

Senior Honors Thesis

College or School



Molecular, Cellular, & Biomedical Sciences

Program or Major

Biomedical Science: Medical and Veterinary Science

Degree Name

Bachelor of Science

First Advisor

Inga Sidor


Gray seals (Halichoerus grypus) are a common pinniped species in New England coastal waters. Parasitic infection is an important cause of mortality for this species, and lungworm species are frequently implicated in cases of respiratory infection, especially in pups and weanling seals. The most common of these is Otostrongylus circumlitus, a large nematode found in the bronchi and bronchioles of affected seals. The full life cycle is unknown but its presence in lungs and sometimes pulmonary arteries suggests that migration via arterial circulation occurs. Signs and microscopic findings are widely variable; our cases included dyspnea, bloody mucoid oral and nasal discharge, eosinophilic bronchitis/bronchiolitis, suppurative pneumonia, and pulmonary congestion and emphysema. Recent evidence suggests a possible increase in O. circumlitus respiratory infection among gray seals that includes arterial vasculitis lesions with deposition of Splendore-Hoeppli tissue and infiltrates of eosinophils. We aim to describe and document the occurrence of this lesion in cases of O. circumlitus in the gray seal population on Cape Cod, MA. Necropsy results including gross and histologic examination of lung were compiled for 34 gray seals, with 11 of these being diagnosed with pulmonary nematodiasis. Eight of the diagnosed nematodiasis cases were found to have concurrent arteritis. Work is ongoing to evaluate the changes in both the pathology and prevalence of this pathogen over time.