Marine Mammal Parasite of the Month- Answer August 2019


This is my friend Acanthocheilonema spirocauda, a filarial parasite. It is commonly found in harbor seals but can also be found in hooded seals, ringed seals and harp seals. It is not yet a huge threat to seal populations but does cause infections like anorexia, fatigue, heart and lung illnesses as well as death. It has been proposed that the vector between A. spirocauda and seals is the seal louse Echinophthirius horridus.
A. spirocauda infects seals all over the world from the United States to the Baltic Sea and Netherlands at different rates.


Keroack, C. D., Williams, K. M., Fessler, M. K., DeAngelis, K. E., Tsekitsidou, E., Tozloski, J. M., & Williams, S. A. (2018). A novel quantitative real-time PCR diagnostic assay for seal heartworm (Acanthocheilonema spirocauda) provides evidence for possible infection in the grey seal (Halichoerus grypus). International Journal for Parasitology: Parasites and Wildlife, 7(2), 147–154.

Keroack, C. D., Wurster, J. I., Decker, C. G., Williams, K. M., Slatko, B. E., Foster, J. M., & Williams, S. A. (2016). Absence of the Filarial Endosymbiont Wolbachia in Seal Heartworm (Acanthocheilonema spirocauda) but Evidence of Ancient Lateral Gene Transfer. The Journal of Parasitology, 102(3), 312–318.

Lehnert et al. – 2016 – Heartworm (Acanthocheilonema spirocauda) and seal .pdf. (n.d.). Retrieved from

Lehnert, K., Schwanke, E., Hahn, K., Wohlsein, P., & Siebert, U. (2016). Heartworm (Acanthocheilonema spirocauda) and seal louse (Echinophthirius horridus) infections in harbour seals (Phoca vitulina) from the North and Baltic Seas. Journal of Sea Research, 113, 65–72.

Leidenberger, S., arding, K. C. H., & Härkönen, T. (2007). Phocid seals, seal lice and heartworms: a terrestrial host-parasite system conveyed to the marine environment. Diseases of Aquatic Organisms, 77(3), 235–253.

Measures, L., Gosselin, J.-F., & Bergeron, E. (1997). Heartworm, Acanthocheilonema spirocauda (Leidy, 1858), infections in Canadian phocid seals. Canadian Journal of Fisheries and Aquatic Sciences – CAN J FISHERIES AQUAT SCI, 54, 842–846.


Posted by Maddy G

Maddy is a summer 2019 intern at the National Marine Life Center. She is a recent graduate of Smith College.