Seal Health and Disease

A comprehensive understanding of the current health of and diseases present in seal populations in the northwest Atlantic is useful not only for management of seals, but also as indicators of the overall health of the Gulf of Maine. 

In turn, the health of the Gulf of Maine and the animals, plants and microbes inhabiting it are intimately connected to human health. Seals can serve as sentinels of emerging pathogens and environmental quality due to their life history traits, such as utilization of coastal habitats and fish commonly consumed by humans. 

We are interested in understanding the health of seal populations, and using their health status to provide a more complete picture of the overall health of the Northwest Atlantic ecosystem. The "health" of a population is measured in multiple ways including traditional population assessments (e.g. age class structure, reproductive output and survivorship) that are used to generate life history tables. Estimates of the physical health of a population, however, are not as easy to generate. Simply defining what constitutes a healthy seal can be a daunting task. 

Recognizing that pinnipeds (walrus, seals and sea lions) are oftentimes difficult to work with in terms of capture for health assessments, members of NASRC have defined priority research areas that will aid in addressing issues concerning health and disease of sentinel species such as seals. While much work has been conducted in other geographic areas, sufficient baseline information is unavailable for the Northwest Atlantic and specifically, the Gulf of Maine.

These are the key areas that the Health and Disease Working Group of NASRC would like to see addressed: 


1. What constitutes a healthy individual? 

It is clear that we need baseline data for several species of seals, including grey, harbor and harp. We have identified several types of data that would be useful in defining the health status of seals. These include, but are not limited to, the following:

  • Complete blood cell counts and blood chemistry value
  • Body condition
  • Immunocompetence estimates (e.g. proliferation of peripheral blood mononuclear cells; phagocytosis and respiratory burst of leukocytes)
  • Toxin levels, such as organochlorides and other chemicals of anthropogenic origin as well as natural toxins, such as domoic acid and saxitoxin
  • Microbial community composition
  • Assessment of previous exposure to defined pathogens of interest


2. What types of parasites are found in the seal populations? Are they transmittable to humans? Are parasites associated with seals impacting fisheries?

A more comprehensive survey of parasites and the effect of climate change on distributions of parasites that impact seals, fisheries and human health is needed.


3. What are the emerging diseases that can potentially impact seals and human populations? Are the viral and bacterial communities affecting Atlantic animals the same as the Pacific populations or does geography affect the distribution and genetic and pathogenic characteristics of emerging pathogens?

Continued work on identification and understanding of diseases affecting northwest Atlantic seals is important to distinguishing pathogens that have the potential to jump to humans. In addition, a comprehensive list of pathogens and other common disease threats is also important for characterizing both natural and anthropogenic factors impacting disease ecology in the northwest Atlantic.



References for Related Studies and Techniques

Anthony, S. J., St. Leger, J. A., Pugliares, K., Ip, H. S., Chan, J. M., Carpenter, Z. W., Navarrete-Macias, I., Sanchez-Leon, M., Saliki, J. T., Pedersen, J., Karesh, W., Daszak,P.,Rabadan, R., Rowles, T. and W. I. Lipkin. (2012) Emergence of Fatal Avian Influenza in New England Harbor Seals.  mBio 3(4):e00166-12.  doi:10.1128/mBio.00166-12.


Bogomolni, A.L., Gast, R.J., Ellis, J.C., Dennett, M., Pugliares, K.R., Lentell, B.J., Moore, M.J. 2008. Victims or vectors: a survey of marine vertebrate zoonoses from coastal waters of the Northwest Atlantic. Diseases of Aquatic Organisms 81:13-38.


Brock, P.M., Hall, A.J., Goodman, S.J., Cruz,M., and K. Acevedo-Whitehouse. (2013) Immune Activity, Body Condition and Human-Associated Environmental Impacts in a Wild Marine Mammal. PLoS ONE 8(6): e67132. doi:10.1371/journal.pone.0067132.


Keogh, M.J., Spoon, T., Ridgway, S.H., Jensen, E., Van Bonn, W., and T.A. Romano. (2011) Simultaneous measurement of phagocytosis and respiratory burst of leukocytes in whole blood from bottlenose dolphins (Tursiops truncatus) utilizing flow cytometry. Veterinary Immunology and Immunopathology 144:468– 475.


Krahn, M.M., Becker, P.R., Tilbury, K.L., and J.E. Stein. (1997) Organochlorine contaminants in blubber of four seal species: Integrating biomonitoring and specimen banking. Chemosphere 34 (9110):2109-2121.


Lasek-Nesselquist, E., D.M. Welch & M.L. Sogin. 2010. The identification of a new Giardia duodenalis assemblage in marine vertebrates and a preliminary analysis of G. duodenalis population biology in marine systems. International Journal of Parasitology 40:1063-1074.


Lehnert, K., von Samson-Himmelstjern, G., Schaudien, D., Bleidorn, C., Wohlsein, P., and U. Siebert. (2010) Transmission of lungworms of harbour porpoises and harbour seals: Molecular tools determine potential vertebrate intermediate hosts. International Journal for Parasitology 40:845–853.


Morgan, L.W., Jakush, J., Simpson, A., Norman, M.M., Pabst, A., Simmons, S., 2009. Evaluation of hematologic and biochemical values for convalescing seals from the coast of Maine. J. Zoo. Wildl. Med. 40, 421–429.


Ramis, A.J., van Riel, D., van de Bildt, M.W.G., Osterhaus, A. and T. Kuiken. (2012)  Influenza A and B Virus Attachment to Respiratory Tract in Marine Mammals. Emerging Infectious Diseases 18(5): 817–820.


Rose JM, Gast RJ, Bogomolni A, Ellis JC, Lentell BJ, Touhey K, et al. (2009) Occurrence and patterns of antibiotic resistance in vertebrates off the Northeastern United States coast. FEMS Microbiology Ecology 76:421-431.


Wallace, C.C., P.O. Yund, T.E. Ford, K.A. Matassa, and A.L. Bass. 2013. Increase in antimicrobial resistance in bacteria cultured from stranded marine mammals of the Northwest Atlantic. EcoHealth10(2):201-210.

Waltzek, T.B., Cortes-Hinojosa, G., Wellehan Jr., J.F.X., and G.C. Gray. (2012) Marine Mammal Zoonoses: A Review of Disease Manifestations. Zoonoses and Public Health: doi: 10.1111/j.1863-2378.2012.01492.x.


Last updated: December 22, 2014