, Volume 4, Issue 2, pp 135–150 | Cite as

Is Marine Mammal Health Deteriorating? Trends in the Global Reporting of Marine Mammal Disease

  • Frances M. D. Gulland
  • Ailsa J. Hall


A recent rise in the reporting of diseases in marine organisms has raised concerns that ocean health is deteriorating. The goal of this study was to determine whether or not there has been a recent deterioration in marine mammal health by investigating the trends in disease reports over the past 40 years (categorized by the method of study, the species affected, and the etiology of the disease) and by exploring the changes in frequency of mass mortality events among marine mammals reported in the United States since 1978. The number of papers on marine mammal disease published each year has increased since 1966, although the annual publication rate appears to have stabilized since ∼1992. Those published in the 1960s and 1970s were largely about helminth and bacterial disease, those investigating viruses emerged in the late 1970s and increased in the 1980s and 1990s, whereas protozoal diseases and harmful algal toxins were largely not reported until the 1990s. The annual number of mass mortality events in the U.S. approximately doubled between 1980 and 1990 but since 2000 has been between seven and eight events per year. Causes of mass mortality events have included biotoxins, viruses, bacteria, parasites, human interactions, oil spills, and changes in oceanographic conditions. Events due to biotoxins appear to be increasing, but the change in the frequency of mass mortality events from other causes over the past 40 years cannot be determined from the available published literature due to changes in marine mammal abundance, inconsistencies in effort and extent of resources for pathological investigation, and advances in technology that have allowed improved detection of pathogens and toxins in more recent years. To ensure future information on the true incidence of marine diseases and their underlying causes is more reliable, specific and directed marine health monitoring programs, well-equipped stranding networks, and dedicated diagnostic laboratories are needed.


disease epidemiology marine mammal mortality morbidity 



We particularly thank Dr. Teri Rowles, NOAA, National Marine Fisheries Service (NMFS), Center for Marine Animal Health, for her encouragement and support. We also thank all members of the National Marine Mammal Health and Stranding Network for their hard work in collecting the data presented here and caring for the stranded animals, and the staff of the NMFS for managing the Marine Mammal Health and Stranding Program, especially Janet Whaley, Trevor Spradlin, Sarah Wilkin, Michelle Ordono, Angela Collins-Payne, Joe Cordaro, and Brent Norberg. We also thank Denise Greig for assistance with this manuscript.


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Copyright information

© Ecohealth Journal Consortium 2007

Authors and Affiliations

  1. 1.Veterinary Science DepartmentCenter for Marine Animal Health and The Marine Mammal CenterSausalitoUSA
  2. 2.Center for Marine Animal Health and Sea Mammal Research UnitUniversity of St. AndrewsSt. AndrewsUK

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