Abstract
Mortality investigation for bottlenose dolphins (Tursiops truncatus) stranded on the Alabama coast increased from 2010 to 2014 during the northern Gulf of Mexico unusual mortality event (UME) associated with the Deepwater Horizon oil spill (DWHOS). Cause of death (COD) patterns since that event have not been published and baseline prevalence of Brucella and morbillivirus, two infectious diseases previously reported in bottlenose dolphins in this region, are lacking for this population. We analyzed stranding records (n=225) of bottlenose dolphins in Alabama from 2015 to 2020 to determine COD and prevalence of Brucella spp. and morbillivirus spp. Cause of death was determined using gross necropsy and histological findings. To determine prevalence of Brucella and morbillivirus infections in stranded animals, a subset of individuals was selected for molecular testing. Necropsies were completed on 181 dolphins, and histology data were available for 63 of those animals to date. Cause of death was grouped into 7 general categories, including human and fisheries interaction, infectious, organ failure, prolonged freshwater exposure, trauma, multifactorial, and unknown. Unknown was further divided into those with poor and good body condition and those with evidence of fetal distress. Advanced decomposition limited COD determination in many individuals, however, fisheries interaction (n=8) was the most often confirmed cause. Morbillivirus was detected in 0% of samples tested (n=68), and Brucella was detected in 20% of samples tested (n=70). Brucella was detected in some moderately to severely decomposed carcasses, indicating that it may be feasible to test a broader range of stranded animals than previously assumed. This study provides valuable information on COD trends in bottlenose dolphins in Alabama since the DWHOS and is the first to establish baseline prevalence of two common infectious diseases in stranded animals from this population.
