Marine mammal mortality events have been linked to harmful algal bloom biotoxins, acoustic events, and infectious disease epidemics, but the underlying causes are often uncertain. We are improving epidemiological tools and modeling approaches to understand factors contributing to disease persistence and transmission, determine the cause, and provide guidance for mitigation and protection of marine wildlife.
Why We Care
Coastal population levels of marine mammals are highly susceptible to chemical contaminant and infectious disease exposure. Since 1991, 55 marine-mammal unusual mortality events (UMEs) have been formally declared by NOAA. These outbreaks often involve zoonotic pathogens—disease agents transmissible from animals to humans. In the past year, four UMEs have initiated epidemiological investigations to determine the cause of morbidity and mortality involving bottlenose dolphins from the Gulf of Mexico and pinniped species from Alaska and the northeast United States. Zoonotic pathogens (Brucella and influenza virus) have been associated with two of the outbreaks. Overarching factors, such as environmental pollution or short- and long-term climate fluctuations, may influence pathogen distribution or host susceptibility, as well as the occurrence and duration of harmful algal blooms (HABs). Because HAB toxins can impact human health and many diseases affecting coastal populations of marine mammals are zoonotic or closely related to terrestrial strains, identifying the pathogens and toxins to which near-shore marine mammals are exposed provides an early warning of health threats for other marine wildlife and humans users of coastal environments.
What We Are Doing
With our collaborators, we are working to apply epidemiological methods that will determine susceptibility, characterize pathologies and syndromes, evaluate causes and contributing factors for mortality and morbidity, and develop surveillance plans to detect additional cases. For example, we are:
- Developing visual health assessment approaches for monitoring skin diseases in coastal dolphin populations
- Designing and developing a generalized individual-based model to predict risks from persistent chemical contaminants for cetacean populations in both coastal and off-shore waters
- Developing of a bioenergetic model to estimate sea lion exposure to biotoxins
- Conducting spatial and temporal analyses of sea lion mortalities related to the biotoxin domoic acid
- Implementing a study design to test hypotheses for specific causes or factors associated with outbreak mortalities
- Developing models for outbreak timing, geographic range, and risk factors.
Historical analyses of influenza-related UMEs in the northeast United States will be conducted to examine temporal, spatial, and climatic factors contributing to the cyclical pattern of outbreaks in the region. Identifying key pathogens affecting marine mammals along U.S. Atlantic coast is also a priority.