Pathogens identified in bottlenose dolphins may indicate the emergence of new diseases from human sources.
Dissertation research, by recently graduated Dr. Leslie Burdett Hart, used over four decades of photographic data to identify and track skin diseases among bottlenose dolphins in Sarasota Bay. She also examined environmental factors associated with the occurrence of skin lesions.
Leslie’s Doctorate is from the Medical University of South Carolina.
Her path towards a career in marine mammal science began as an undergraduate intern for SDRP during the summer of 2000 (along with recently graduated PhDs, Katie McHugh and Brian Balmer).
Leslie’s research used photographs of SDRP dolphins across generations to estimate the prevalence of a highly visible white skin diseases called lacaziosis (Lacazia loboi). Also called Lobo’s Disease or lobomycosis, this skin lesion is known in humans, and it was first identified in a dolphin in 1970 by SDRP researchers Randy Wells and Blair Irvine.
About 2-3% of the dolphins in Sarasota Bay and Charlotte Harbor, Florida are infected with lacaziosis or a lacaziosis-like disease.
In Sarasota Bay, lacaziosis-like disease is most common among adult males. The white patches of skin are usually located on the dorsal fin, flippers, and tail flukes.
While it never goes away, the growth of lacaziosis lesions does appear to gradually slow over time and can proceed at a rate that is different between animals.
The SDRP photographic records suggests that lacaziosis is non-communicable. Infected dolphins were not often observed with each other. Among groups or pairings with infected dolphins, uninfected animals never developed the disease.
This research was possible because the SDRP has a 40 year photographic record of local dolphins. Those with skin diseases have been examined by veterinarians during health assessments.
This has allowed us to develop a model of lacaziosis-like diseases in dolphins. We can applied to other skin diseases on dolphins that are commonly observed in photographic images.
The research is important because it suggests that dolphin photographic studies, which are being conducted throughout the world, may be able to develop skin disease models using only 5-10 years worth of data.
The health assessments conducted by SDRP are of great scientific and medical benefit to assess the health of wild dolphin populations. But health assessments require substantial effort and cost, and they are not broadly practical.
Leslie’s research suggests that photographic studies of well-known bottlenose dolphin populations can be used as a non-invasive approach to better understand factors that may contribute to skin disease susceptibility, transmission, and sources.
Monitoring disease occurrence in dolphins can serve as a surveillance system to track current and future emerging pathogens.
To learn more on the technical side, read Leslie’s publication or contact Leslie by email (Leslie.Burdett@noaa.gov) for a pdf. The Abstract of her Dissertation is included below.
Leslie has another article In Press (Burdett Hart, L., Rotstein, D.S., Wells, R.S., Bassos-Hull, K., and L.H. Schwacke. In Press. Lacaziosis and Lacaziosis-like Prevalence among Wild, Common Bottlenose Dolphins (Tursiops truncatus) from the West Coast of Florida, USA. Diseases of Aquatic Organisms), and a third article is in preparation.
Leslie Burdett Hart
2011 Dissertation Abstract
Many populations of bottlenose dolphins (Tursiops truncatus) inhabit coastal and estuarine waters near highly populated and developed areas, which make them susceptible to anthropogenic and terrestrial threats from pollution and runoff. Pathogens historically considered to be terrestrial and zoonotic have been identified in bottlenose dolphins (Tursiops truncatus) in recent years, possibly indicating a shift in host preference or the emergence of new diseases in naïve populations. This project utilized a visual assessment approach for evaluating small cetacean health based on the prevalence, extent, and etiology of observed skin lesions and specific diseases such as lacaziosis. The prevalence of skin lesions and occurrence of different lesion types were examined among free-ranging bottlenose dolphins from three different sites in the southeastern United States (Charleston, SC; Brunswick and Sapelo, GA; Sarasota Bay, FL). The prevalence of skin lesions for the three sites ranged between 37-58% and comparisons between sites revealed significant differences in the occurrence of skin lesions, as well as differences in lesion types. A similar seasonal trend in lesion prevalence was observed for all three sites, and regression modeling revealed associations between lesion occurrence and colder water temperatures. Lacaziosis was used as a model skin disease for epidemiologic investigations of infected dolphins from Sarasota Bay and Charlotte Harbor, Florida. Approximately 2-3% of the dolphins in both populations were infected with lacaziosis or lacaziosis-like disease, and these estimates were robust to alterations in estimation methodologies. Descriptive analyses of a case series of dolphins in Sarasota Bay indicated that lacaziosis and lacaziosis-like disease were most common among adult males, and lesions were primarily located on the extremities. Case-control analyses for lacaziosis and non-lacaziosis dolphins in Sarasota Bay revealed differences in the spatial distribution and clustering of sightings, a ten-year difference in the median survival time, and social associations that suggested a non-communicable transmission pathway. Growth modeling of lacaziosis lesion progression among three lacaziosis cases from Sarasota Bay showed some individual variation in lesion progression and a gradual decrease in lesion growth over time. Furthermore, truncated modeling approaches revealed that 5-10 years of longitudinal photographic data may be sufficient for the development of similar models in other populations. Recent efforts to assess the health of wild dolphin populations have used capture and release methods; however, such methods require substantial effort, risk and cost, and are not appropriate across a broad geographic or temporal scale. Longitudinal and cross-sectional photographs of well-known bottlenose dolphin populations can be used as a non-invasive approach to develop epidemiological studies to better understand the demographic, geographic, and environmental variables that may contribute to skin disease susceptibility, transmission, and sources/reservoirs. Developing efficient means to monitor disease occurrence in these sentinel species ultimately serves as a surveillance system to track current and future emerging pathogens.