297
Chapter thirteen: Disease
be exposed through direct contact with the oil in the water column; through ingestion of
contaminated water and prey; and through inhalation of petroleum vapors.
Inhalation of petroleum vapors has been linked to decreased lung function, chronic
bronchitis, and airway inflammation in humans (Sekkal et al. 2012). Ultrasonographic
pulmonary changes seen in dolphins in the spill area following the Deepwater Horizon
spill were similar to the findings associated with these pulmonary diseases. In addition to
pulmonary disease, affected dolphins also showed evidence of adrenal suppression, liver
damage, and tooth loss (Schwacke et al. 2014).
13.2.2 Physiologic adaptation: Skin
Cetacean skin has undergone significant changes in order to maintain homeostasis in the
marine environment. The skin is hairless, smooth, and lacks any cutaneous appendages or
glands. In order to protect against the osmotic challenges of living in water, the epidermis
provides a protective layer that is impermeable to water. To maintain this protection, the
epidermal turnover rate is 8.5 times higher than human skin (Hicks et al. 1985). Cetaceans
have also developed an alternative method of repairing skin damage because they are
unable to form a transition scab in the water (Bruce-Allen and Geraci 1985). A breach in the
dermis allows seawater contact with epidermal cells causing degeneration and swelling of
these cells in order to provide a protective barrier to the deeper regenerating cells. As the
skin wound heals from below, the degenerate cells are sloughed off as the wound closes.
In bottlenose dolphins, the skin heals at the same rate as humans; however, in other cetaceans, dermal wound healing is longer and affected by dermal thickness and environmental conditions such as water temperature and salinity. In the beluga whale (Delphinapterus
leucas), skin wounds heal in 30–40 days, five times longer than in bottlenose dolphins primarily due to the fact that beluga skin is five times thicker than dolphin skin (Geraci and
Bruce-Allen 1987). Belugas likely have thicker skin because they live in substantially colder
water and are exposed to water with low salinity when they inhabit river estuaries during
the summer months.
The dermis is a primary protective barrier against environmental stressors in cetaceans, but it is highly susceptible to water-quality abnormalities like changes in salinity and increases in pollutants and nutrients in the water caused by local freshwater and
storm water run-off. For example, 30% of dolphins living in the southern Indian River
Lagoon in Florida have developed lacaziosis (lobomycosis), a chronic mycotic disease of
the skin and subdermal tissues caused by a yeast-like organism known as Lacazia loboi
(Reif et al. 2006). Water quality of the Indian River Lagoon has dramatically decreased over
the past 50 years due to changes in watershed drainage and land development, leaving
the local dolphin population susceptible to this naturally occurring fungus. There is also
evidence that the population of dolphins affected by lacaziosis may have immunosuppression, showing depressed lymphocyte proliferation, which plays a role in responding
to external pathogens.
Dolphins that are infected with lacaziosis may have extensive areas of affected
skin that cover large areas of the body. Lesions may be associated with sites of previous
trauma such as shark bite scars, where the protective mechanisms of the skin may be
reduced. Raised, bumpy areas of skin may turn white or discolored, and are often found
on the dorsal fin, flukes, or head. As lacaziosis is a zoonotic disease, humans are also susceptible to infection by L. loboi, and care should be taken when handling animals with
visible skin lesions. The fungus is typically spread through breaks or cuts in the skin
(Figure 13.1).
Chapter thirteen: Disease
be exposed through direct contact with the oil in the water column; through ingestion of
contaminated water and prey; and through inhalation of petroleum vapors.
Inhalation of petroleum vapors has been linked to decreased lung function, chronic
bronchitis, and airway inflammation in humans (Sekkal et al. 2012). Ultrasonographic
pulmonary changes seen in dolphins in the spill area following the Deepwater Horizon
spill were similar to the findings associated with these pulmonary diseases. In addition to
pulmonary disease, affected dolphins also showed evidence of adrenal suppression, liver
damage, and tooth loss (Schwacke et al. 2014).
13.2.2 Physiologic adaptation: Skin
Cetacean skin has undergone significant changes in order to maintain homeostasis in the
marine environment. The skin is hairless, smooth, and lacks any cutaneous appendages or
glands. In order to protect against the osmotic challenges of living in water, the epidermis
provides a protective layer that is impermeable to water. To maintain this protection, the
epidermal turnover rate is 8.5 times higher than human skin (Hicks et al. 1985). Cetaceans
have also developed an alternative method of repairing skin damage because they are
unable to form a transition scab in the water (Bruce-Allen and Geraci 1985). A breach in the
dermis allows seawater contact with epidermal cells causing degeneration and swelling of
these cells in order to provide a protective barrier to the deeper regenerating cells. As the
skin wound heals from below, the degenerate cells are sloughed off as the wound closes.
In bottlenose dolphins, the skin heals at the same rate as humans; however, in other cetaceans, dermal wound healing is longer and affected by dermal thickness and environmental conditions such as water temperature and salinity. In the beluga whale (Delphinapterus
leucas), skin wounds heal in 30–40 days, five times longer than in bottlenose dolphins primarily due to the fact that beluga skin is five times thicker than dolphin skin (Geraci and
Bruce-Allen 1987). Belugas likely have thicker skin because they live in substantially colder
water and are exposed to water with low salinity when they inhabit river estuaries during
the summer months.
The dermis is a primary protective barrier against environmental stressors in cetaceans, but it is highly susceptible to water-quality abnormalities like changes in salinity and increases in pollutants and nutrients in the water caused by local freshwater and
storm water run-off. For example, 30% of dolphins living in the southern Indian River
Lagoon in Florida have developed lacaziosis (lobomycosis), a chronic mycotic disease of
the skin and subdermal tissues caused by a yeast-like organism known as Lacazia loboi
(Reif et al. 2006). Water quality of the Indian River Lagoon has dramatically decreased over
the past 50 years due to changes in watershed drainage and land development, leaving
the local dolphin population susceptible to this naturally occurring fungus. There is also
evidence that the population of dolphins affected by lacaziosis may have immunosuppression, showing depressed lymphocyte proliferation, which plays a role in responding
to external pathogens.
Dolphins that are infected with lacaziosis may have extensive areas of affected
skin that cover large areas of the body. Lesions may be associated with sites of previous
trauma such as shark bite scars, where the protective mechanisms of the skin may be
reduced. Raised, bumpy areas of skin may turn white or discolored, and are often found
on the dorsal fin, flukes, or head. As lacaziosis is a zoonotic disease, humans are also susceptible to infection by L. loboi, and care should be taken when handling animals with
visible skin lesions. The fungus is typically spread through breaks or cuts in the skin
(Figure 13.1).