Tropical Fungus Range Expands into Northern Waters

image of swimming dolphin with visible lobomycosis

This dolphin was spotted swimming off the coast of North Carolina. The bottlenose appears to have lobomycosis, a fungal skin infection usually associated with warmer tropical waters. A NOAA-led team is now working to determine how factors like water temperature, salinity, and coastal land-use might be influencing the types, prevalence, and severity of these type of infections.

In August 2008, an Atlantic bottlenose dolphin was found dead on the North Carolina coast, its skin cracked and ulcerated with an alarming growth of gray and white nodules.

This dolphin was confirmed as having lobomycosis, the first confirmed case in North Carolina waters of this chronic fungal skin infection.

Reports of this type of infection in both humans and dolphins are relatively common in the warmer coastal waters of South America. Cases of lobomycosis have also turned up in waters off both east and west coasts of southern Florida and the Texas Gulf Coast.

Now, however, the range of the fungus that causes the lobomycosis infection appears to be expanding northward.

In a study appearing in the April issue of the journal Emerging Infectious Diseases, an interdisciplinary team of researchers from the National Ocean Service, NOAA Fisheries, University of North Carolina Wilmington, and University of Tennessee report on a potential change in the northern distribution of this fungus in North America.

close up image of lobomycosis skin infection on dolphin

Lobomycosis, a fungal skin infection, found on an Atlantic bottlenose dolphin in North Carolina.

These findings are part of a larger effort to investigate the different types and range of skin disease in dolphins along the eastern U.S. coast.

Various types of skin disease are often observed in stranded and free-swimming marine mammals, and more specifically dolphins, along the U.S. coast. The skin lesions are often related to environmental conditions or bacterial, viral, or even fungal infections.

In addition to finding out more about the underlying causes of the skin lesions found along the east coast, the NOAA team is working to determine how factors like water temperature, salinity, and coastal land-use might be influencing the types, prevalence and severity of the infections.

To aid in this pursuit, the NOAA-led research team is now working on a new way to document various types of skin lesions in dolphins based on photographs.

From the National Centers for Coastal Ocean Science’s Hollings Marine Laboratory in Charleston, South Carolina, the research team recently distributed field kits for use by members of NOAA Fisheries’ Southeast Regional Marine Mammal Stranding Network. The aim of the kits is to standardize how information and samples are collected when stranded dolphins or live,free-swimming animals with skin lesions are found.

Stranding Network partners take photographs and document information such as lesion location on the body, size, and color. They also take multiple tissue samples and ship them to a NOAA Fisheries pathology lab. There, samples are processed and analyzed and, when necessary, sent off for closer study to determine the specific pathogen.

All of the resulting data from the field and lab work are being used by a team of scientists to develop a visual classification system for the lesions. While it will take a while to develop this new system, it is expected to allow researchers to more quickly and accurately track and better understand physical, chemical, and biological factors that influence skin infections in the wild.

Understanding shifts in distribution of marine pathogens like the fungus that causes lobomycosis is critical not only to better gauge potential health risks to humans and marine life, but also to more effectively forecast ecological impacts of certain human activities.

What is learned through this long-term study will help ecosystem and public health managers develop more effective management strategies to threats posed by bacteria, viruses, fungi, and other pathogens found in the ocean.