Marine Mammal Parasite of the Month- January 2022 Answer

This parasite is Stenurus minor! Most often found in the cranial sinuses and lungs, it is likely that cranial sinuses are the definitive site for adult parasites to grow and thrive. S. minor infects the frontal sinuses more so than the ear sinuses but has been found in high numbers in the middle ear. It puts pressure on the tympanic cavity, the round window, and the oval window and plugs the middle ear to prevent proper transmission of sound, which causes a muffling effect. It also causes chronic inflammation of the mucous membrane and the skeletal muscles of the ear, possibly due to secretions that irritate the middle and inner ear. Further, a few studies have speculated that this parasite causes physical damage to the auditory organs and others have hypothesized that this disruption of the organs in the cranial sinuses causes strandings to occur. Unfortunately, there is very little evidence of the life cycle, transmission, or the relationship between the parasite and the porpoises, and most is speculation. It has been hypothesized that infection causes an immune response that prevents reinfection and places a limit on the number of adult worms that are present. It’s also possible that space is a limiting factor on how many worms can be present at once. 

Posted by fall intern, Adrienne V-H.

References  

Faulkner, J., Measures, L. N., & Whoriskey F. G. (1998). Stenurus minor (Metastrongyloidea: Pseudaliidae) infections of the cranial sinuses of the harbour porpoise, Phocoena phocoena. Canadian Journal of Zoology, 76, 1209-1216.  

Kijewska, A. Jankowski, Z., Kuklik, I., & Rokicki, J. (2003). Pathological changes in the auditory organs of the harbor porpoise (Phocoena phocoena L.) associated with Stenurus minor Kuhn, 1829). Acta Parasitologica, 48(1), 60-63. 

Larsen, B. H. (1995). Parasites and pollutants in seven harbour porpoises (Phocoena phocoena L. 1758) from the Faroe Islands, 1987-1988. In A. Bjorge & G.P. Donovan (Eds.), Biology of phocoenids (pp. 223-230). The International Whaling Commission.