Wild dolphins are exposed to more pollutants than their captive counterparts, which could explain why they face higher rates of illness and disease, US researchers said Wednesday.
The study in the journal PLOS ONE analyzed the health of two wild dolphin populations — one group in Florida and another in South Carolina.
They were compared to two populations of captive dolphins in Georgia and California, which turned out to be far healthier.
Fewer than half the wild dolphins studied were "clinically normal," and many had chronically activated immune systems, signaling they were fighting off disease.
"This is likely a result of encountering pathogens, parasites, and anthropogenic pollutants in the ocean that do not exist in closely managed zoological habitats," said lead author Patricia Fair, research professor at the Medical University of South Carolina.
In humans, this kind of chronic immune response has been linked to cancer, heart disease, and increased vulnerability to infectious disease.
Co-author Gregory Bossart, chief veterinary officer at the Georgia Aquarium, has been studying the health of more than 360 individual dolphins living in Indian River Lagoon in Florida and Charleston, South Carolina since 2003.
Since then, he and fellow researchers have documented "emerging infectious diseases, tumors, antibiotic resistant bacteria, and alarmingly high levels of contaminants in dolphins from both wild populations," said the study.