Lacaziosis (Lacazia loboi) is a chronic, fungal skin disease that naturally occurs only in humans and dolphins, and was first discovered in a dolphin from Sarasota Bay in 1970 that was recovered and necropsied by Blair Irvine and Randy Wells. Recent analyses of longitudinal photographs of diseased dolphins have revealed that lacaziosis is slowly progressive and that lesion growth may be variable among individuals belonging to the same population. In addition to historical observations of lacaziosis in Sarasota Bay, bottlenose dolphin photo-ID efforts in Charlotte Harbor during the 1990s have also revealed the occurrence of skin lesions consistent with lacaziosis. Although lacaziosis has been documented for over 20 years in Charlotte Harbor and over four decades in Sarasota Bay, the disease burden in these populations was previously unknown.
Lacaziosis (LD) prevalence in Sarasota Bay was estimated using historical capture-release health assessment records
for the time periods 1980-1989 and 1990-1999. Cases were identified through historical photographs (see below), skin assessment forms, veterinary records, and pathology reports confirming the presence of L. loboi in lesion biopsies. A total of 106 and 117 individual dolphins were captured and released during the 1980s and 1990s, respectively, and of these, approximately 2-3% were diagnosed with lacaziosis. This skin disease has been observed in dolphins from many populations across the globe, including the Indian River Lagoon (IRL) in Florida, Mayotte, Colombia, Ecuador, and Brazil (see graph). Statistical analyses comparing the Sarasota Bay lacaziosis prevalence to these other population estimates revealed no significant differences in disease occurrence.
For Charlotte Harbor bottlenose dolphins, lacaziosis confirmation was not possible as lesion biopsies were not available for histological diagnosis. Instead, the prevalence of lacaziosis-like disease (LLD) was estimated using photo-ID images from 2003 that were screened for the presence of skin lesions consistent with characteristics of lesions from confirmed lacaziosis cases (see photo below). Of the 591 individual dolphins with images suitable for case detection, animals were classified as either 1) no LLD; 2) possible LLD; or 3) LLD case. Overall, the prevalence of LLD in Charlotte Harbor for 2003 ranged between 2% and 5% depending on the inclusion of ‘possible LLD’ cases. Statistical
comparisons of the Charlotte Harbor LLD prevalence estimate to other estimates of lacaziosis in dolphin populations across the globe revealed significant differences in LLD/LD between Charlotte Harbor and IRL dolphins.
Despite their close proximity, the LD/LLD estimates for Sarasota Bay and Charlotte Harbor were lower than estimates for dolphins inhabiting the IRL on the east coast of Florida. Future research efforts will focus on methods to identify geographic, environmental, and demographic factors that may contribute to differences in disease occurrence across populations. Because lacaziosis is a zoonotic pathogen, the discovery of factors that contribute to disease susceptibility, transmission, and persistence in infected dolphins may also enhance our understanding of disease mechanisms in human populations.
All photos © Sarasota Dolphin Research Program under NMFS permit #522-1785