Health Assessments of Common Bottlenose Dolphins (Tursiops truncatus): Past, Present, and Potential Conservation Applications.

The common bottlenose dolphin (Tursiops truncatus) is a global marine mammal species for which some populations, due to their coastal accessibility, have been monitored diligently by scientists for decades. Health assessment examinations have developed a comprehensive knowledge base of dolphin biology, population structure, and environmental or anthropogenic stressors affecting their dynamics. Bottlenose dolphin health assessments initially started as stock assessments prior to acquisition. Over the last four decades, health assessments have evolved into essential conservation management tools of free-ranging dolphin populations. Baseline data enable comparison of stressors between geographic locations and associated changes in individual and population health status. In addition, long-term monitoring provides opportunities for insights into population shifts over time, with retrospective application of novel diagnostic tests on archived samples. Expanding scientific knowledge enables effective long-term conservation management strategies by facilitating informed decision making and improving social understanding of the anthropogenic effects. The ability to use bottlenose dolphins as a model for studying marine mammal health has been pivotal in our understanding of anthropogenic effects on multiple marine mammal species. Future studies aim to build on current knowledge to influence management decisions and species conservation. This paper reviews the historical approaches to dolphin health assessments, present day achievements, and development of future conservation goals.

Electrocardiograms of bottlenose dolphins (Tursiops truncatus) out of water: habituated collection versus wild postcapture animals.

Electrocardiography (ECG) was performed on captured free-ranging bottlenose dolphins (Tursiops truncatus) during a health assessment exercise and compared with that of a Navy collection of dolphins habituated to handling out of water in order to assess possible cardiovascular impacts of capture and handling. Six-lead recordings (I, II, III, aVr, aVl, and aVf) in the frontal plane and direct thorax leads were collected from both groups, with a modified base-apex lead additionally employed with the Navy collection dolphins. Measured and calculated parameters included amplitudes of P, R, S, and T waves and total QRS complex; T:S and T:QRS ratios; heart rate; durations of P wave; QRS complex, PR, QT, and RR intervals; maximum minus minimum RR interval; ST segment elevation-depression; and mean electrical axis (MEA). Physiologically minor but statistically significant differences were detected in S wave amplitude, PR interval, QRS duration, and MEA. The PR interval, QRS duration, and S wave amplitude were slightly greater and the MEA oriented slightly rightward in wild postcapture dolphins compared to Navy collection dolphins. There were no differences in heart rate or maximum minus minimum RR interval, which serves as a proxy for the expected sinus arrhythmia of dolphins. The base-apex lead resulted in greater QRS amplitude than lead II, as expected for the category B ventricular activation of dolphins. The left-side direct thorax lead was more consistent than that of the right side. Clinically, ECG was a useful adjunct to auscultation and thoracic palpation for monitoring heart rate and rhythm and generated a record for archiving. Safe capture and handling protocols in place, under which dolphins are immediately returned to the water at progressive signs of distress, may make cardiovascular decompensation less likely to be detected by ECG. It appears that the dolphin cardiovascular system compensates suitably well to capture, as measured by ECG under the conditions of this study.

Eosinophilia and biotoxin exposure in bottlenose dolphins (Tursiops truncatus) from a coastal area impacted by repeated mortality events.

Bottlenose dolphins (Tursiops truncatus) inhabiting coastal waters in the northern Gulf of Mexico have been impacted by recurrent unusual mortality events over the past few decades. Several of these mortality events along the Florida panhandle have been tentatively attributed to poisoning from brevetoxin produced by the dinoflagellate Karenia brevis. While dolphins in other regions of the Florida coast are often exposed to K. brevis blooms, large-scale dolphin mortality events are relatively rare and the frequency and magnitude of die-offs along the Panhandle raise concern for the apparent vulnerability of dolphins in this region. We report results from dolphin health assessments conducted near St. Joseph Bay, Florida, an area impacted by 3 unusual die-offs within a 7-year time span. An eosinophilia syndrome, manifested as an elevated blood eosinophil count without obvious cause, was observed in 23% of sampled dolphins. Elevated eosinophil counts were associated with decreased T-lymphocyte proliferation and increased neutrophil phagocytosis. In addition, indication of chronic low-level exposure to another algal toxin, domoic acid produced by the diatom Pseudo-nitzschia spp., was determined. Previous studies of other marine mammal populations exposed recurrently to Pseudo-nitzschia blooms have suggested a possible link between the eosinophilia and domoic acid exposure. While the chronic eosinophilia syndrome could over the long-term produce organ damage and alter immunological status and thereby increase vulnerability to other challenges, the significance of the high prevalence of the syndrome to the observed mortality events in the St. Joseph Bay area is unclear. Nonetheless, the unusual immunological findings and concurrent evidence of domoic acid exposure in this sentinel marine species suggest a need for further investigation to elucidate potential links between chronic, low-level exposure to algal toxins and immune health.

Hematologic and serum biochemical reference intervals for free-ranging common bottlenose dolphins (Tursiops truncatus) and variation in the distributions of clinicopathologic values related to geographic sampling site.

OBJECTIVE: To develop robust reference intervals for hematologic and serum biochemical variables by use of data derived from free-ranging bottlenose dolphins (Tursiops truncatus) and examine potential variation in distributions of clinicopathologic values related to sampling sites' geographic locations. ANIMALS: 255 free-ranging bottlenose dolphins. PROCEDURES: Data from samples collected during multiple bottlenose dolphin capture-release projects conducted at 4 southeastern US coastal locations in 2000 through 2006 were combined to determine reference intervals for 52 clinicopathologic variables. A nonparametric bootstrap approach was applied to estimate 95th percentiles and associated 90% confidence intervals; the need for partitioning by length and sex classes was determined by testing for differences in estimated thresholds with a bootstrap method. When appropriate, quantile regression was used to determine continuous functions for 95th percentiles dependent on length. The proportion of out-of-range samples for all clinicopathologic measurements was examined for each geographic site, and multivariate ANOVA was applied to further explore variation in leukocyte subgroups. RESULTS: A need for partitioning by length and sex classes was indicated for many clinicopathologic variables. For each geographic site, few significant deviations from expected number of out-of-range samples were detected. Although mean leukocyte counts did not vary among sites, differences in the mean counts for leukocyte subgroups were identified. CONCLUSIONS AND CLINICAL RELEVANCE: Although differences in the centrality of distributions for some variables were detected, the 95th percentiles estimated from the pooled data were robust and applicable across geographic sites. The derived reference intervals provide critical information for conducting bottlenose dolphin population health studies.

Home ranges of bottlenose dolphins (Tursiops truncatus) in the Indian River Lagoon, Florida: environmental correlates and implications for management strategies.

Photo-identification surveys conducted between 2002 and 2005 were used to determine dolphin home ranges and site fidelity within the Indian River Lagoon (IRL), Florida. The IRL was divided into six segments based on hydrodynamics and geographic features for purposes of characterization. Among the 615 dolphins with identifiable dorsal fins, 339 had > or =6 sightings and were used in segment and linear range analyses. The majority (98%) of dolphins were seen in < or =3 consecutive segments (331/339); of these, 44% (144/331) occurred in two segments, and 33% (109/331) in one segment. No dolphins were observed in all six segments. The largest number of dolphins was sighted in segment 1C (North Indian River). However, the highest density of dolphins was found in segment 2 (North-Central Indian River). Re-sighting rates for dolphins with > or =6 sightings ranged from 2.8 to 8.7 times observed. The mean linear home range varied from 22 to 54 km. Distributional analyses indicated that at least three different dolphin communities exist within the IRL: Mosquito Lagoon, and the North and South Indian River. No statistically significant correlations were found between the total number or density per km(2 )of dolphins and surface water area, salinity, or contaminant loads within segments of the lagoon. These results suggest that dolphins do not selectively avoid areas with relatively unfavorable water quality. IRL dolphins should be studied on smaller spatial scales than currently practiced, and potential anthropogenic impacts should be evaluated based on geographic partitioning.

Bartonella species detection in captive, stranded and free-ranging cetaceans.

We present prevalence of Bartonella spp. for multiple cohorts of wild and captive cetaceans. One hundred and six cetaceans including 86 bottlenose dolphins (71 free-ranging, 14 captive in a facility with a dolphin experiencing debility of unknown origin, 1 stranded), 11 striped dolphins, 4 harbor porpoises, 3 Risso's dolphins, 1 dwarf sperm whale and 1 pygmy sperm whale (all stranded) were sampled. Whole blood (n = 95 live animals) and tissues (n = 15 freshly dead animals) were screened by PCR (n = 106 animals), PCR of enrichment cultures (n = 50 animals), and subcultures (n = 50 animals). Bartonella spp. were detected from 17 cetaceans, including 12 by direct extraction PCR of blood or tissues, 6 by PCR of enrichment cultures, and 4 by subculture isolation. Bartonella spp. were more commonly detected from the captive (6/14, 43%) than from free-ranging (2/71, 2.8%) bottlenose dolphins, and were commonly detected from the stranded animals (9/21, 43%; 3/11 striped dolphins, 3/4 harbor porpoises, 2/3 Risso's dolphins, 1/1 pygmy sperm whale, 0/1 dwarf sperm whale, 0/1 bottlenose dolphin). Sequencing identified a Bartonella spp. most similar to B. henselae San Antonio 2 in eight cases (4 bottlenose dolphins, 2 striped dolphins, 2 harbor porpoises), B. henselae Houston 1 in three cases (2 Risso's dolphins, 1 harbor porpoise), and untyped in six cases (4 bottlenose dolphins, 1 striped dolphin, 1 pygmy sperm whale). Although disease causation has not been established, Bartonella species were detected more commonly from cetaceans that were overtly debilitated or were cohabiting in captivity with a debilitated animal than from free-ranging animals. The detection of Bartonella spp. from cetaceans may be of pathophysiological concern.

Evaluation and comparison of the health status of Atlantic bottlenose dolphins from the Indian River Lagoon, Florida, and Charleston, South Carolina.

OBJECTIVE: To conduct health assessments and compare outcomes in 2 populations of Atlantic bottlenose dolphins. Design-Repeated cross-sectional study. ANIMALS: 171 Atlantic bottlenose dolphins. PROCEDURES: During June and August of 2003 through 2005, 89 dolphins from the Indian River Lagoon (IRL), Florida, and 82 dolphins from estuarine waters near Charleston, SC, were evaluated. A panel of 5 marine mammal veterinarians classified dolphins as clinically normal, possibly diseased, or definitely diseased on the basis of results of physical and ultrasonographic examinations, hematologic and serum biochemical analyses, and cytologic and microbiologic evaluations of gastric contents and swab specimens. RESULTS: Prevalence of dolphins classified as definitely diseased did not differ significantly between the IRL (32%) and Charleston (20%) sites. Proportions of dolphins classified as possibly diseased also did not differ. Lobomycosis was diagnosed in 9 dolphins from the IRL but in none of the dolphins from Charleston. Proportions of dolphins with orogenital papillomas did not differ significantly between the IRL (12%) and Charleston (7%) sites. From 2003 through 2005, the proportion classified as definitely diseased tripled among dolphins from the Charleston site but did not increase significantly among dolphins from the IRL. Dolphins from the Charleston site were more likely to have leukocytosis, lymphocytosis, and low serum concentrations of total protein and total J-globulins than were dolphins from the IRL. CONCLUSIONS AND CLINICAL RELEVANCE: High prevalences of diseased dolphins were identified at both sites; however, the host or environmental factors that contributed to the various abnormalities detected are unknown.

Aerobic microorganisms associated with free-ranging bottlenose dolphins in coastal Gulf of Mexico and Atlantic Ocean waters.

Our abilities to assess health risks to free-ranging dolphin populations, to treat live-stranded or captive dolphins, and to evaluate the risks of disease transmission between humans and dolphins have suffered from a lack of basic information on microorganisms associated with normal, presumably healthy free-ranging individuals. In order to provide these data, we sampled free-ranging bottlenose dolphins (Tursiops truncatus) off Florida, Texas, and North Carolina during 1990-2002. Blowhole and anal/fecal samples yielded 1,871 bacteria and yeast isolates and included 85 different species or groups of organisms. Vibrios, unidentified pseudomonads, Escherichia coli, Staphylococcus spp., and a large group of nonfermenting gram-negative bacteria represented >50% of isolates. Vibrio alginolyticus and Vibrio damsela were the most commonly recovered bacteria from both anal/fecal and blowhole samples. Many organisms occurred sporadically in dolphins that were sampled repeatedly, but some were consistently isolated from individual animals and may indicate the carrier state. Vibrios were common, but some geographic variability in the presence of these and other organisms was noted. Potential pathogens of significance to humans and other animals were recovered.

Geographic variation in polychorinated biphenyl and organochlorine pesticide concentrations in the blubber of bottlenose dolphins from the US Atlantic coast.

Concentrations of polychorinated biphenyls (PCBs) and other organochlorine contaminants (OCs) were measured in blubber collected from live bottlenose dolphins (Tursiops truncatus) at three sites along the United States Atlantic coast. Dolphins were sampled via surgical biopsy during capture-release studies near Charleston, South Carolina and Beaufort, North Carolina. Additional animals were sampled using remote biopsy techniques in estuarine waters near Charleston and from the Indian River Lagoon, Florida. Overall concentrations of major contaminant groups were found to vary between sites and mean concentrations of most OCs from male dolphins in the Indian River Lagoon were less than half of those measured from Charleston and Beaufort males. Geometric mean total PCB concentrations were 30, 27 and 14 microg/g lipid for male dolphins sampled in Beaufort, Charleston and the Indian River Lagoon, respectively. Significant variation related to sex- and age-class, as well as geographic sampling location, was seen in the PCB congener profiles. The measured PCB concentrations, although lower than those reported for stranded animals from the 1987/1988 epizootic along the United States mid-Atlantic coast, are sufficiently high to warrant concern for the health of dolphins from the sampled populations, particularly the animals near Charleston and Beaufort.

Probabilistic risk assessment of reproductive effects of polychlorinated biphenyls on bottlenose dolphins (Tursiops truncatus) from the Southeast United States Coast.

High levels of polychlorinated biphenyls (PCBs) have been reported in the tissues of some species of marine mammals. The high concentrations are of concern because a growing body of experimental evidence links PCBs to deleterious effects on reproduction, endocrine homeostasis, and immune system function. Much of the recent research has focused on determining the exposure of marine mammal populations to PCBs, but very little effort has been devoted to the actual risk assessments that are needed to determine the expected impacts of the documented exposures. We describe a novel risk assessment approach that integrates measured tissue concentrations of PCBs with a surrogate dose-response relationship and leads to predictions of health risks for marine mammals as well as to the uncertainties associated with these predictions. Specifically, we use PCB tissue residue data from three populations of bottlenose dolphins (Tursiops truncatus), study the feasibility of published dose-response data from a surrogate species. and combine this information to estimate the risk of detrimental reproductive effects in female dolphins. Our risk analyses for dolphin populations near Beaufort (NC, USA), Sarasota (FL, USA), and Matagorda Bay (TX, USA) indicate a high likelihood that reproductive success, primarily in primiparous females, is being severely impaired by chronic exposure to PCBs. Excess risk of reproductive failure, measured in terms of stillbirth or neonatal mortality, for primiparous females was estimated as 60% (Beaufort), 79% (Sarasota), and 78% (Matagorda Bay). Females of higher parity, which have previously off-loaded a majority of their PCB burden, exhibit a much lower risk.