On June 18th, our team received a call from Kiawah Island Beach Patrol about a dead dolphin that had washed ashore. Initial observations indicated this was a male, juvenile (~1-3 yrs old) bottlenose dolphin.
This dolphin also had an unusually short rostrum (or snout) with a pronounced underbite. The could indicate this he was from an offshore population of dolphins, as offshore dolphins tend to have shorter rostrums. The skin we collected for DNA testing will help us confirm that.
This dolphin also exhibited extensive tattoo skin lesions. Tattoo skin disease (TSD) is caused by a poxvirus and presents as irregular, gray or black stippling of the skin with hyperpigmentation around the perimeter. It is rarely lethal for cetaceans but can affect individuals for months. Studies have found that young calves (< 1 year) often have a low prevalence of TSD due to maternal immunity, while yearlings (1-2 years) have a higher prevalence. As they age, prevalence declines again as they develop infection-acquired immunity.
We were able to pick up this dolphin and bring it back to the NCCOS NOS laboratory and conduct a full necropsy. This animal had an abnormally pale liver and a moderate parasite infection in both lungs, which could indicate verminous pneumonia. Tissue samples were sent off to our colleague, Dr. Dave Rotstein, DVM, for pathology testing which will help identify a possible cause of death.
Thank you to Will Bowling and other team members with the Kiawah Island Beach Patrol for reporting this animal to us and helping us retrieve it off the beach.
UPDATE: Histopathology Results
Histopathology reports confirmed this animal's likely cause of death was due to verminous pneumonia. This occurred due to a severe infection of lungworm in the respiratory tract which led to pneumonia and likely reduced feeding as well.
Lungworm infection is relatively common in other whale, dolphin, and porpoise species and does not always lead to death. It is not entirely clear how marine mammals become infected, however, it is believed to be transmitted either through prey species, or direct transmission of larvae via transplacental or transmammary routes. This would mean that adult females are transferring a parasite load to their offspring through the placenta during gestation or through milk after birth. Neonates tend to have the most active and severe infections. If a neonatal animal is further compromised by a difficult birth or high environmental contaminant loads, then lungworm infection may be a contributory factor in increased neonatal mortality.
Sources:
Fauquier, D. A., Kinsel, M. J., Dailey, M. D., Sutton, G. E., Stolen, M. K., Wells, R. S., & Gulland, F. M. D. (2009). Prevalence and pathology of lungworm infection in bottlenose dolphins Tursiops truncatus in southwest Florida. Diseases of Aquatic Organisms, 88, 85-90. https://doi.org/10.3354/dao02095
Powell, S. N., Wallen, M. M., Bansal, S., & Mann, J. (2018). Epidemiological investigation of tattoo-like skin lesions among bottlenose dolphins in Shark Bay, Australia. Science of the Total Environment, 630, 774–780. https://doi.org/10.1016/j.scitotenv.2018.02.202
Van Bressem, M.-F., Van Waerebeek, K., & Duignan, P. J. (2022). Tattoo Skin Disease in Cetacea: A Review, with New Cases for the Northeast Pacific. Animals, 12(24), 3581. https://doi.org/10.3390/ani12243581