Abstract
Skin disease occurs frequently in many cetacean species across the globe; methods to categorize lesions have relied on photo-identification (photo-id), stranding, and by-catch data. The current study used photo-id data from four sampling months during 2009 to estimate skin lesion prevalence and type occurring on bottlenose dolphins (Tursiops truncatus) from three sites along the southeast United States coast [Sarasota Bay, FL (SSB); near Brunswick and Sapelo Island, GA (BSG); and near Charleston, SC (CHS)]. The prevalence of lesions was highest among BSG dolphins (P = 0.587) and lowest in SSB (P = 0.380), and the overall prevalence was significantly different among all sites (p<0.0167). Logistic regression modeling revealed a significant reduction in the odds of lesion occurrence for increasing water temperatures (OR = 0.92; 95%CI:0.906–0.938) and a significantly increased odds of lesion occurrence for BSG dolphins (OR = 1.39; 95%CI:1.203–1.614). Approximately one-third of the lesioned dolphins from each site presented with multiple types, and population differences in lesion type occurrence were observed (p<0.05). Lesions on stranded dolphins were sampled to determine the etiology of different lesion types, which included three visually distinct samples positive for herpesvirus. Although generally considered non-fatal, skin disease may be indicative of animal health or exposure to anthropogenic or environmental threats, and photo-id data provide an efficient and cost-effective approach to document the occurrence of skin lesions in free-ranging populations.
Highlights
Skin lesions in delphinids and other small cetaceans are geographically widespread [1,2,3,4,5,6,7,8,9]
In Brunswick and Sapelo Island, GA (BSG), images of 322 distinct individuals were suitable for lesion screening, and 189 (P = 0.587; 95% CI: 0.531–0.641) animals were found to have visible skin lesions
These results suggest that skin lesion occurrence is influenced by factors other than just water temperature, that there is a lag time between exposure to colder water temperatures and the clinical manifestation of disease, or that pathogen viability and dolphin susceptibility may be heightened when water temperatures are within a particular range
Summary
Skin lesions in delphinids and other small cetaceans are geographically widespread [1,2,3,4,5,6,7,8,9]. Tattoo lesions have been studied extensively by Van Bressem et al [5,9,12], where the reported prevalence of this specific lesion type among bottlenose dolphins ranges from 0% [9] to 71% [12]. Most of these studies used photo-identification (photo-id) data to estimate the population prevalence of skin disease Other studies have relied on bycatch or stranding data [1,4,5,9,16,17], or capture-release health assessment data [3,18,19] to estimate disease burden in wild populations; these methods can be limited by small sample sizes or in the case of stranding data, biased towards individuals with compromised health [20]
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