Marine Mammal Parasite of the Month – Answer Oct 2012

Dr. Williams

These are seal lice, or Echinophthrius horridus.

They are lice, sucking lice, or Anoplurans to be more precise. Lice are insects within the hexapods with 6 legs, as opposed to mites which are arachnids with 8 legs (some  parasite mites may have fewer; impress your friends!).

Echinophthrius horridus are found on many phocids such as Harbor, Hooded, Bearded, Gray, Harp, and Ringed seals.

Seal lice can perforate the skin and may cause infections. Overwhelming infections can cause anemia, and at least one yearling harbor seal with a severe lice infestation was found to have died of anemia (Lehnert, Raga et al. 2007). Seal lice are implicated as the vectors for seal heart-worm disease (Geraci, Fortin et al. 1981). Large numbers may compromise diving ability (Thompson, Corpe et al. 1998). There was no evidence of anemia in this animal (PCV 57%) and the infection was mild and not related to the severe clinical presentation of this neonatal seal.

~ Bess, E. and K. P. Johnson. (2008). “Echinophthirius.” Tree of Life, Web Project, from
~ Ferris, G. F. (1934). Contributions Towards a Monograph of the Sucking Lice Part VII. Stanford University Publications, University Series, Biological Sciences, Standford University. II: 475-480.
~ Geraci, J. R., J. F. Fortin, et al. (1981). “The seal louse, Echinophthirius horridus: an intermediate host of the seal heartworm, Dipetalonema spirocauda (Nematoda).” Canadian Journal of Zoology 59: 1457-1459.
~ Lehnert, K., J. A. Raga, et al. (2007). “Parasites in harbour seals (Phoca vitulina) from the German Wadden Sea between Phocine Distemper Virus epidemics.” Helgol Mar Res 61: 239-245.
~ Thompson, P. M., H. M. Corpe, et al. (1998). “Prevalence and intensity of the ectoparasite Echinophthirius horridus on harbour seals (Phoca vitulina): effects of host age and inter-annual variability in host food availability.” Parasitology 117 (Pt 4): 393-403.