A histopathologic evaluation of gross lesions excised from commercially important North Altantic marine fishes

Histopathologic studies of lesions found in commercially important North Atlantic marine fishes are uncommon. As part of a comprehensive Northeast Fisheries Center program ("Ocean Pulse") to evaluate environmental and resource health on the U.S. Continental Shelf from Cape Hatteras to Nova Scotia, grossly visible lesions of the gills, integument, muscle, and viscera of primarily bottom-dwelling fishes were excised and examined using light microscopy. Several gadid and pleuronectid fishes accounted for most of the lesions observed. Most pathological examinations were incidental to samples taken for age and growth determination and evaluation of predator/prey relationships. Several gadids, with either gill, heart, or spleen lesions, were sampled more intensively. Gill lesions principally affected gadids and were caused by either microsporidans or an unidentified oocyte-like cell. The majority of gastrointestinal lesions consisted of encapsulated or encysted larval worms or microsporidan-induced cysts. Few heart lesions were found. Integumental lesioos included ulcers, lymphocystis, and trematode metacercariae. Liver lesions almost always consisted of encapsulated or encysted larval helminths. Necrotic granulomata were seen in muscle and microsporidan-induced granulomata in spleen. Although not numerous, histologically interesting lesions were noted in integument, heart, liver, spleen, and muscle of several fish species. Histologic study of tissues excised from a variety of demersal and pelagic fishes from the eastern North Atlantic (France, Germany, Spain) revealed assorted integumental, renal, hepatic, and splenic lesions. Small sample size and non-random sampling precluded obtaining a meaningful quantitative estimate of the prevalence of the observed lesions in the population at risk; however, a useful census has been made of the types of lesions present in commercially important marine fishes. (PDF file contains 20 pages.)

Skin lesions on common bottlenose dolphins (Tursiops truncatus) from three sites in the Northwest Atlantic, USA

Skin disease occurs frequently in many cetacean species across the globe; methods to categorize lesions have relied on photo-identification (photo-id), stranding, and bycatch 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.

Gill lesions associated with acute exposure to ammonia

Histopathological effects of ammonia on the gills of milkfish (Chanos chanos ) fingerlings were examined qualitatively.

Study of bacterial agents on external lesions of cultured Sturgeons in Sngar zone of Gilan Province

This study was carried out to isolate and determine bacterial agents in outer lesions of sturgeons in Shahid Dr. Beheshti sturgeon propagation and rearing center in Gilan province. Five species of sturgeons were studied from viewpoint of lesions. A number of 167 specimens of Beluga, 76 specimens of Persian sturgeon, 27 specimens of Russian sturgeon, 42 specimens of stellate and finally 23 specimens of ship had bacterial lesions in different outer parts of their bodies. After sampling and purification, bacterial cultures and biochemical tests were done. After the isolation of bacteria from lesions, Edwardsiella tarda was selected by means of PCR. To obtain molecular acceptance, a pair of E. tarda special primer, forward primer ETa2-351 and reverse primer (Edwsp-780r) were reproduced. A number of 12 E. tarda DNA sample were identified by PCR. After molecular diagnosis, Persian sturgeon challenged with E. tarda for determination of pathogenesis. Challenge method was done by means of injection of different dilutes of E. tarda into dorsal muscle. Sampling of hematopoietic organs (kidney, spleen and liver) were carried out and located in Boin's fixator to perform pathology survey. Also, in order to survey of existence and effect of E. tarda, sampling of kidney for bacterial culture was done by molecular and biochemical methods. Results showed that the most lesions in all five species belonged to abdominal surface. Skin and scutes of this part were involved in comparison with other parts. Also, It was removed some samples from lesions to pathological survey. Microscopic observations showed some levels of destruction of epidermis layers, necrosis of dermis cells and destruction of muscular layer of skin. On the other hand, invasion of inflammatory cells and haemorrhagic in dermis were clear. Based on biochemical results, Aeromonas sobria, A cavia . A. hydrophila , Acinetobacter lowffii , A.baumanni , A.cakoaceticus, Pseudomonas putida , P fluorescens , P.aeruginosa , Serratia marcescens , Escherichia coli , Enterobacter aerogenes , Edwardsiella tarda , Proteus mirabilis , kelebsiella oxytoca and Staphylococcus sp. were isolated from outer lesions. Results of PCR confirmed that E. tarda was before and after challenge in 200 bp range. LD50, 96h was determined 1.2 x 10^5 (CFU/ml). Pathological experiments showed lesions in the kidney, including hemorrhages, degeneration of glumeruli and tubular epithelia, degeneration and necrosis of interestitium tissue, accumulation of protein casts in the tubular lumen. It was observed haemorhages, engorged blood vessels, congestion of sinusoids, increased of melanine, melano macrophage centers, degeneration and necrosis of hepatocytes in the liver. In the spleen, it was recorded congestion, degeneration, necrosis changes in the white and red pulpa, blood engorged and detachment of ellipsoid wall.

Effects of commercial fishing regulations on stranding rates of bottlenose dolphin (Tursiops truncatus).

Fisheries management actions taken to protect one species can have unintended, and sometimes positive, consequences on other species. For example, regulatory measures to reduce fishing effort in the winter gillnet fishery for spiny dogfish (Squalus acanthias) off North Carolina (NC) also led to decreases in the number of bycaught bottlenose dolphins (Tursiops truncatus). This study found that a marked decrease in fishing effort for spiny dogfish in NC also corresponded with a marked decrease in winter stranding rates of bottlenose dolphins with entanglement lesions (P= 0.002). Furthermore, from 1997 through 2002, there was a significant positive correlation (r2 = 0.79; P= 0.0003) between seasonal bycatch estimates of bottlenose dolphins in gill nets and rates of stranded dolphins with entanglement lesions. With this information, stranding thresholds were developed that would enable the detection of those increases in bycatch in near real-time. This approach is valuable because updated bycatch estimates from observer data usually have a time-lag of two or more years. Threshold values could be used to detect increases in stranding rates, triggering managers immediately to direct observer effort to areas of potentially high bycatch or to institute mitigation measures. Thus, observer coverage and stranding investigations can be used in concert for more effective fishery management.

Report on Marine Mammal Unusual Mortality Event UMESE0501Sp: Multispecies Mass Stranding of Pilot Whales (Globicephala macrorhynchus), Minke Whale (Balaenoptera acutorostrata), and Dwarf Sperm Whales (Kogia sima) in North Carolina on 15-16 January 2005

On 15-16 January 2005, three offshore species of cetaceans (33 short-finned pilot whales, Globicephala macrorhynchus, one minke whale, Balaenoptera acutorostrata, and two dwarf sperm whales, Kogia sima) stranded alive on the beaches of North Carolina. The pilot whales stranded near Oregon Inlet, the minke whale in northern North Carolina, and the dwarf sperm whales near Cape Hatteras. Live strandings of three species in one weekend was unique in North Carolina and qualified as an Unusual Mortality Event. Gross necropsies were conducted on 16-17 January 2005 on 27 pilot whales, two dwarf sperm whales, and the minke whale. Samples were collected for clinical pathology, parasitology, gross pathology, histopathology, microbiology and serology. There was variation in the number of animals sampled for each collection type, however, due to carcasses washing off the beach or degradation in carcass condition during the course of the response. Comprehensive histologic examination was conducted on 16 pilot whales, both dwarf sperm whales, and the minke whale. Limited organ or only head tissue suites were obtained from nine pilot whales. Histologic examination of tissues began in February 2005 and concluded in December 2005 when final sampling was concluded. Neither the pilot whales nor dwarf sperm whales were emaciated although none had recently ingested prey in their stomachs. The minke whale was emaciated; it was likely a dependent calf that became separated from the female. Most serum biochemistry abnormalities appear to have resulted from the stranding and indicated deteriorating condition from being on land for an extended period. Three pilot whales had clinical evidence of pre-existing systemic inflammation, which was supported by histopathologic findings. Although gross and histologic lesions involving all organ systems were noted, consistent lesions were not observed across species. Verminous pterygoid sinusitis and healed fishery interactions were seen in pilot whales but neither of these changes were causes of debilitation or death. In three pilot whales and one dwarf sperm whale there was evidence of clinically significant disease in postcranial tissues which led to chronic debilitation. Cardiovascular disease was present in one pilot whale and one dwarf sperm whale; musculoskeletal disease and intra-abdominal granulomas were present in two pilot whales. These lesions were possible, but not definitive, causal factors in the stranding. Remaining lesions were incidental or post-stranding. The minke whale and three of five tested pilot whales had positive morbillivirus titers (≥1:8 with one at >1:256), but there was no histologic evidence of active viral infection. Parasites (nematodes, cestodes, and trematodes) were collected from 26 pilot whales and two dwarf sperm whales. Sites of collection included stomach, nasal/pterygoid, peribullar sinuses, blubber, and abdominal cavity. Parasite species, locations and loads were within normal limits for free-ranging cetaceans and were not considered causative for the stranding event. Gas emboli lesions which were considered consistent with or diagnostic of sonarassociated strandings of beaked whales or small cetaceans were not found in the whales stranded as part of UMESE0501Sp. Twenty-five heads were examined with nine specific anatomic locations of interest: extramandibular fat, intramandibular fat, auditory meatus, peribullar acoustic fat, peribullar soft tissue, peribullar sinus, pterygoid sinus, melon, and brain. The common finding in all examined heads was verminous pterygoid sinusitis. Intramandibular adipose tissue reddening, typically adjacent to the vascular plexus, was observed in some individuals and could represent localized hemorrhage resulting from vascular rete rupture, hypostatic congestion, or erythrocyte rupture during the freeze/thaw cycle. One cetacean had peracute to acute subdural hemorrhage that likely occurred from thrashing on the beach post-stranding, although its occurrence prior to stranding cannot be excluded. Information provided to NMFS by the U.S. Navy indicated routine tactical mid-frequency sonar operations from individual surface vessels over relatively short durations and small spatial scales within the area and time period investigated. No marine mammals were detected by marine mammal observers on operational vessels; standard operating procedure for surface naval vessels operating mid-frequency sonar is the use of trained visual lookouts using high-powered binoculars. Sound propagation modeling using information provided to NMFS indicated that acoustic conditions in the vicinity likely depended heavily on position of the receivers (e.g., range, bearing, depth) relative to that of the sources. Absent explicit information on the location of animals meant that it was not possible to estimate received acoustic exposures from active sonar transmissions. Nonetheless, the event was associated in time and space with naval activity using mid-frequency active sonar. It also had a number of features in common (e.g., the “atypical” distribution of strandings involving multiple offshore species, all stranding alive, and without evidence of common infectious or other disease process) with other sonar-related cetacean mass stranding events. Given that this event was the only stranding of offshore species to occur within a 2-3 day period in the region on record (i.e., a very rare event), and given the occurrence of the event simultaneously in time and space with a naval exercise using active sonar, the association between the naval sonar activity and the location and timing of the event could be a causal rather than a coincidental relationship. However, evidence supporting a definitive association is lacking, and, in particular, there are differences in operational/environmental characteristics between this event and previous events where sonar has apparently played a role in marine mammal strandings. This does not preclude behavorial avoidance of noise exposure. No harmful algal blooms were present along the Atlantic coast south of the Chesapeake Bay during the months prior to the event. Environmental conditions, including strong winds, changes in upwelling- to downwelling-favorable conditions, and gently sloping bathymetry, were consistent with conditions which have been correlated with other mass strandings. In summary, we did not find commonality in gross and histologic lesions that would indicate a single cause for this stranding event. Three pilot whales and one dwarf sperm whale had debilitating conditions identified that could have contributed to stranding, one pilot whale had a debilitating condition (subdural hemorrhage) that could have been present prior to or resulting from stranding. While the pilot and dwarf sperm whale strandings may have had a common cause, the minke whale stranding was probably just coincidental. On the basis of examination of physical evidence in the affected whales, however, we cannot definitively conclude that there was or was not a causal link between anthropogenic sonar activity or environmental conditions (or a combination of these factors) and the strandings. Overall, the cause of UMESE0501Sp in North Carolina is not and likely will not be definitively known. (PDF contains 240 pages)

USGS/NOAA Workshop on Mycobacteriosis in Striped Bass, May 7-10, 2006, Annapolis, Maryland

As a Federal trust species, the well-being of the striped bass (Morone saxatilis) population along the Eastern Seaboard is of major concern to resource users. Striped bass are an extremely valuable commercial and recreational resource. As a principal piscivore in Chesapeake Bay, striped bass directly or indirectly interact with multiple trophic levels within the ecosystem and are therefore very sensitive to biotic and abiotic ecosystem changes. For reasons that have yet to be defined, the species has a high intrinsic susceptibility to mycobacteriosis. This disease has been impacting Chesapeake Bay striped bass since at least the 1980s as indicated by archived tissue samples. However, it was not until heightened incidences of fish with skin lesions in the Pocomoke River and other tributaries of the Chesapeake Bay were reported in the summer and fall of 1996 and 1997 that a great deal of public and scientific interest was stimulated about concerns for fish disease in the Bay. (PDF contains 50 pages)

Coral Disease and Health Workshop: Coral Histopathology II

The health and continued existence of coral reef ecosystems are threatened by an increasing array of environmental and anthropogenic impacts. Coral disease is one of the prominent causes of increased mortality among reefs globally, particularly in the Caribbean. Although over 40 different coral diseases and syndromes have been reported worldwide, only a few etiological agents have been confirmed; most pathogens remain unknown and the dynamics of disease transmission, pathogenicity and mortality are not understood. Causal relationships have been documented for only a few of the coral diseases, while new syndromes continue to emerge. Extensive field observations by coral biologists have provided substantial documentation of a plethora of new pathologies, but our understanding, however, has been limited to descriptions of gross lesions with names reflecting these observations (e.g., black band, white band, dark spot). To determine etiology, we must equip coral diseases scientists with basic biomedical knowledge and specialized training in areas such as histology, cell biology and pathology. Only through combining descriptive science with mechanistic science and employing the synthesis epizootiology provides will we be able to gain insight into causation and become equipped to handle the pending crisis. One of the critical challenges faced by coral disease researchers is to establish a framework to systematically study coral pathologies drawing from the field of diagnostic medicine and pathology and using generally accepted nomenclature. This process began in April 2004, with a workshop titled Coral Disease and Health Workshop: Developing Diagnostic Criteria co-convened by the Coral Disease and Health Consortium (CDHC), a working group organized under the auspices of the U.S. Coral Reef Task Force, and the International Registry for Coral Pathology (IRCP). The workshop was hosted by the U.S. Geological Survey, National Wildlife Health Center (NWHC) in Madison, Wisconsin and was focused on gross morphology and disease signs observed in the field. A resounding recommendation from the histopathologists participating in the workshop was the urgent need to develop diagnostic criteria that are suitable to move from gross observations to morphological diagnoses based on evaluation of microscopic anatomy. (PDF contains 92 pages)