Marine Animal Rehabilitation Center - University of New England

Pathogen Identification and Monitoring in Seals and Other Free Ranging Mammals in
Maine
By: Courtney C. Wallace, Anna L. Bass, and Philip Yund
Center for Land – Sea Interactions
Numerous waterborne pathogens affect not only terrestrial animals, such as cattle, dogs, cats, and humans, but
also marine mammals such as seals. The protozoans Giardia intestinalis and Cryptosporidium spp. are examples of
waterborne pathogens, which cause diseases known as giardiasis and cryptosporidiosis, respectively. Symptoms for
both include diarrhea, dehydration and malnutrition. These symptoms tend to be more severe in younger animals,
oftentimes leading to a greater degree of mortality. The focus of our lab is to not only detect infection in MARC seals,
but also collect and test fecal samples from other wild and domestic animals in Maine in order to determine how
many and what type of animals carry these protozoans. Once we identify carriers and the pathogen genotype present
we can begin to develop a picture of how these protozoans are getting to marine mammals.
So far, we have successfully detected Giardia intestinalis in both terrestrial and marine mammals. Terrestrial
hosts include cows, coyotes, moose, mice, geese, turkeys and even an otter. By using molecular methods, we have
been able to determine that the strains found in these animals are similar to those found in marine mammals. We
have detected Giardia in both harp and harbor seals, not just from animals rehabilitated by MARC, but from areas all
along the coast of Maine. We have found infections in pups as well as adults. We have also confirmed the presence
of a new strain (Assemblage H) of Giardia intestinalis detected previously only in grey seals. Our research shows that
this strain is also found in harbor seals. Further investigation into Assemblage H by our lab has found significant
similarities between H and a strain found in wild deer mice, which may also provide a clue as to how these
protozoans are
transmitted among species.
Although we have not detected any Cryptosporidium infections in terrestrial animals, we have identified an
uncharacterized species of Cryptosporidium in harbor, harp and hooded seals. This uncharacterized species was
previously identified only in ringed seals living far north of the Gulf of Maine. Although we still do not fully understand
this new Cryptosporidium species, our research has revealed that this protozoan does indeed infect other seal
species and extends further south than previously suspected.
It seems that we are on the right trail in terms of uncovering the transmission pathway for Giardia and learning
more about Cryptosporidium in seals. Eventually, if we can pinpoint the cause of these infections in marine
mammals, we can then take the next steps to reducing water contamination and save a few more seals.
Giardia and
cryptosporidium
have been observed
in seals at MARC