Morbilliviral epizootic in bottlenose dolphins of the Gulf of Mexico

Survey of selected viral agents (herpesvirus, adenovirus and hepatitis E virus) in liver and lung samples of cetaceans, Brazil

Hepatic and pulmonary lesions are common in cetaceans, despite their poorly understood viral etiology. Herpesviruses (HV), adenoviruses (AdV) and hepatitis E virus (HEV) are emerging agents in cetaceans, associated with liver and/or pulmonary damage in mammals. We isolated and molecularly tested DNA for HV and AdV (n = 218 individuals; 187 liver and 108 lung samples) and RNA for HEV (n = 147 animals; 147 liver samples) from six cetacean families. All animals stranded or were bycaught in Brazil between 2001 and 2021. Positive-animals were analyzed by histopathology. Statistical analyses assessed if the prevalence of viral infection could be associated with the variables: species, family, habitat, region, sex, and age group. All samples were negative for AdV and HEV. Overall, 8.7% (19/218) of the cetaceans were HV-positive (4.8% [9/187] liver and 11.1% [12/108] lung), without HV-associated lesions. HV-prevalence was statistically significant higher in Pontoporiidae (19.2%, 10/52) when compared to Delphinidae (4.1%, 5/121), and in southeastern (17.1%, 13/76)-the most industrialized Brazilian region-when compared to the northeastern region (2.4%, 3/126). This study broadens the herpesvirus host range in cetaceans, including its description in pygmy sperm whales (Kogia breviceps) and humpback whales (Megaptera novaeangliae). Further studies must elucidate herpesvirus drivers in cetaceans.

Comparison between Sampling Techniques for Virological Molecular Analyses: Dolphin Morbillivirus and Herpesvirus Detection from FTA® Card and Frozen Tissue

Stranded animals offer valuable information on marine mammal physiology and pathology; however, the decomposition state of the carcasses and lack of a rigorous cold chain for sample preservation can sometimes discourage diagnostic analyses based on nucleic acid detection. The present paper aims at evaluating the reliability of FTA® card tissue imprints as an alternative matrix to frozen tissues for virological analyses based on biomolecular methods. Given the contribution of Cetacean morbillivirus (CeMV) to strandings and the increase of herpesvirus detection in cetaceans, these two pathogens were selected as representative of RNA and DNA viruses. Dolphin morbillivirus (DMV) and herpesvirus presence was investigated in parallel on tissue imprints on FTA® cards and frozen tissues collected during necropsy of dolphins stranded in Italy. Samples were analysed by nested RT-PCR for DMV and nested-PCR for herpesvirus. Only one animal was positive for herpesvirus, hampering further considerations on this virus. DMV was detected in all animals, both in FTA® card imprints and tissue samples, with differences possibly related to the decomposition condition category of the carcasses. Tissue sampling on FTA® cards seems a promising alternative to frozen tissues for biomolecular analyses, especially when ensuring adequate storage and shipment conditions for frozen tissues is difficult.

Causes of death and pathogen prevalence in bottlenose dolphins Tursiops truncatus stranded in Alabama, USA, between 2015 and 2020, following the Deepwater Horizon oil spill

Between 2010 and 2014, an unusual mortality event (UME) involving bottlenose dolphins Tursiops truncatus occurred in the northern Gulf of Mexico, associated with the Deepwater Horizon oil spill (DWHOS). Cause of death (COD) patterns in bottlenose dolphins since then have not been analyzed, and baseline prevalence data for Brucella ceti and cetacean morbillivirus, 2 pathogens previously reported in this region, are lacking. We analyzed records from bottlenose dolphins stranded in Alabama from 2015 to 2020 with necropsy and histological findings to determine COD (n = 108). This period included another UME in 2019 associated with prolonged freshwater exposure. A subset of individuals that stranded during this period were selected for molecular testing for Brucella spp. and Morbillivirus spp. Causes of death for all age classes were grouped into 6 categories, including (1) human interaction, (2) infectious disease, (3) noninfectious disease (prolonged freshwater exposure and degenerative), (4) trauma, (5) multifactorial, and (6) unknown. Two additional categories unique to perinates included fetal distress and in utero pneumonia. Human interaction was the most common primary COD (19.4%) followed closely by infectious disease (17.6%) and noninfectious disease (freshwater exposure; 13.9%). Brucella was detected in 18.4% of the 98 animals tested, but morbillivirus was not detected in any of the 66 animals tested. Brucella was detected in some moderately to severely decomposed carcasses, indicating that it may be beneficial to test a broad condition range of stranded animals. This study provides valuable information on COD in bottlenose dolphins in Alabama following the DWHOS and is the first to examine baseline prevalence of 2 common pathogens in stranded animals from this region.

Epidemiological and genetic analysis of Cetacean Morbillivirus circulating on the Italian coast between 2018 and 2021

Cetacean morbillivirus (CeMV) has caused several outbreaks, unusual mortality events, and interepidemic single-lethal disease episodes in the Mediterranean Sea. Since 2012, a new strain with a northeast (NE) Atlantic origin has been circulating among Mediterranean cetaceans, causing numerous deaths. The objective of this study was to determine the prevalence of CeMV in cetaceans stranded in Italy between 2018 and 2021 and characterize the strain of CeMV circulating. Out of the 354 stranded cetaceans along the Italian coastlines, 113 were CeMV-positive. This prevalence (31.9%) is one of the highest reported without an associated outbreak. All marine sectors along the Italian coastlines, except for the northern Adriatic coast, reported a positive molecular diagnosis of CeMV. In one-third of the CeMV-positive cetaceans submitted to a histological evaluation, a chronic form of the infection (detectable viral antigen, the absence of associated lesions, and concomitant coinfections) was suspected. Tissues from 24 animals were used to characterize the strain, obtaining 57 sequences from phosphoprotein, nucleocapsid, and fusion protein genes, which were submitted to GenBank. Our sequences showed the highest identity with NE-Atlantic strain sequences, and in the phylogenetic study, they clustered together with them. Regarding age and species, most of these individuals were adults (17/24, 70.83%) and striped dolphins (19/24, 79.16%). This study improves our understanding on the NE-Atlantic CeMV strain in the Italian waters, supporting the hypothesis of an endemic circulation of the virus in this area; however, additional studies are necessary to deeply comprehend the epidemiology of this strain in the Mediterranean Sea.

Linking morbillivirus exposure to individual habitat use of common bottlenose dolphins (Tursiops truncatus) between geographically different sites

Dolphin morbillivirus (DMV) is a virulent pathogen that causes high mortality outbreaks in delphinids globally and is spread via contact among individuals. Broadly ranging nearshore and open-ocean delphinids are likely reservoir populations that transmit DMV to estuarine populations. We assessed the seroprevalence of DMV antibodies and determined the habitat use of common bottlenose dolphins, Tursiops truncatus truncatus, from two estuarine sites, Barataria Bay and Mississippi Sound, in the northern Gulf of Mexico. We predicted that risk to DMV exposure in estuarine dolphins is driven by spatial overlap in habitat use with reservoir populations. Serum was collected from live-captured dolphins and tested for DMV antibodies. Habitat use of sampled individuals was determined by analysing satellite-tracked movements and stable isotope values. DMV seroprevalences were high among dolphins at Barataria Bay (37%) and Mississippi Sound (44%), but varied differently within sites. Ranging patterns of Barataria Bay dolphins were categorized into two groups: Interior and Island-associated. DMV seroprevalences were absent in Interior dolphins (0%) but high in Island-associated dolphins (45%). Ranging patterns of Mississippi Sound dolphins were categorized into three groups: Interior, Island-east and Island-west. DMV seroprevalences were detected across Mississippi Sound (Interior: 60%; Island-east: 20%; and Island-west: 43%). At both sites, dolphins in habitats with greater marine influence had enriched δ¹³ C values, and Barataria Bay dolphins with positive DMV titres had carbon isotope values indicative of marine habitats. Positive titres for DMV antibodies were more common in the lower versus upper parts of Barataria Bay but evenly distributed across Mississippi Sound. A dolphin's risk of exposure to DMV is influenced by how individual ranging patterns interact with environmental geography. Barataria Bay's partially enclosed geography likely limits the nearshore or open-ocean delphinids that carry DMV from interacting with dolphins that use interior, estuarine habitats, decreasing their exposure to DMV. Mississippi Sound's relatively open geography allows for greater spatial overlap and mixing among estuarine, nearshore and/or open-ocean cetaceans. The spread of DMV, and likely other diseases, is affected by the combination of individual movements, habitat use and the environment.

Pneumonia in endangered aquatic mammals and the need for developing low-coverage vaccination for their management and conservation

Anthropogenic activities can lead to several devastating effects on the environment. The pollutants, which include the discharge of effluents, runoffs in the form of different lethal and sub-lethal concentrations of pesticides, heavy metals, and other contaminants, can harm exposed fauna and flora. The aquatic environment is the ultimate destination for many pollutants which negatively affect aquatic biodiversity and even can cause a species to become extinct. A pollutant can directly affect the behavior of an animal, disrupt cellular systems, and impair the immune system. This harm can be reduced and even mitigated by adopting proper approaches for the conservation of the target biota. Among aquatic organisms, cetaceans, such as the Yangtze finless porpoise, Irrawaddy dolphin, Ganges River dolphin, Amazon River dolphin, and Indus River dolphin, are at a higher risk of extinction because of lack of knowledge and research, and thus insufficient information with respect to their conservation status, management, and policies. Pneumonia is one of the leading causes of mass mortalities of cetaceans. This article reviews the limited research reported on stress and pneumonia induced by pollution, stress-induced pneumonia and immunosuppression, pneumonia-caused mass mortalities of aquatic mammals, and vaccination in wildlife with a specific focus on aquatic mammals, the role of genomics in vaccine development and vaccination, and the major challenges in vaccine development for biodiversity conservation.

Risk of COVID-19 pneumonia in aquatic mammals

•The SARS-CoV-2 can enter the oceans, rivers, and lakes in several ways. •Aquatic mammals can recognise the receptor binding domain of SARS-CoV-2. •Cetacean species should be screened and monitored for the virus during a pandemic.

Neurobrucellosis in a common bottlenose dolphin (Tursiops truncatus) stranded in the Canary Islands

Background

Brucella spp. isolation is increasingly reported in cetaceans, although associated pathologies, including lesions of the musculoskeletal and nervous systems, are less frequently described. Concerning the nervous system, Brucella sp. infection causing meningitis, meningoencephalitis or meningoencephalomyelitis have been extensively reported in striped dolphins (Stenella coeruleoalba), and less frequently in other cetacean species.

Case presentation

A juvenile female common bottlenose dolphin (Tursiops truncatus) was found stranded alive in Lanzarote (Canary Islands, Spain) in 2005, but died shortly after. On physical examination, the dolphin showed a moderate body condition and was classified as code 2 (fresh dead) at the time of necropsy. The main gross findings were severe multiorgan parasitism, thickened and congested leptomeninges, and (sero)fibrino-suppurative and proliferative arthritis of the shoulder joint. Histopathological examination revealed the distinct features of a sub-acute systemic disease associated with Cetacean Morbillivirus (CeMV) infection. However, brain lesions diverged from those reported in systemic CeMV infection. This led to suspect that there was a coinfecting pathogen, based on the characteristics of the inflammatory response and the lesion distribution pattern in the central nervous system. Brucella sp. was detected in the brain tissue by PCR and Brucella antigen was demonstrated by immunohistochemistry in the brain and shoulder joint lesions.

Conclusions

The zoonotic potential of marine mammal strains of Brucella has been demonstrated both in natural and laboratory conditions. In this study, PCR detected Brucella sp. in the brain of a common bottlenose dolphin stranded in the Canary Islands; the dolphin was also co-infected with CeMV. This is the first detection of Brucella sp. infection in a stranded cetacean in this archipelago. Therefore, we stress the importance of taking adequate measures during the handling of these species to prevent the transmissions of the infection to humans.

Circulation of a novel strain of dolphin morbillivirus (DMV) in stranded cetaceans in the Mediterranean Sea

Dolphin morbillivirus (DMV) has been responsible for several outbreaks of systemic infection and has resulted in cetacean strandings in the Mediterranean. In August-October 2016, seven striped dolphins (Stenella coeruleoalba) stranded on the Sicilian coastline (Italy) tested positive for DMV. Tissue samples from brain, lung, pulmonary lymph nodes, heart, spleen, liver, stomach, intestine, kidneys and urinary bladder, as well as blowhole swabs, were collected during necropsy for molecular diagnostics and pathology studies. Extracted tissue RNA was screened for DMV by real-time reverse transcription polymerase chain reaction (PCR). Some tissues exhibited microscopic lesions that were consistent with DMV infection on histopathological and immunohistochemical grounds. Conventional reverse transcription PCR to target partial nucleoprotein and phosphoprotein genes yielded sequences used to genetically characterize the associated DMV strain. DMV RNA was detected by both PCR assays in all tested tissues of the seven dolphins, which suggests systemic infections, but was absent from another dolphin stranded on the Sicilian coastline during the same period. The partial phosphoprotein and nucleoprotein gene sequences from the positive dolphins were 99.7% and 99.5% identical, respectively, to the DMV sequences recently observed in cetaceans stranded on the Spanish Mediterranean. Our study suggests that this DMV strain is circulating in the Mediterranean.

Phylogenomic insights to the origin and spread of phocine distemper virus in European harbour seals in 1988 and 2002

The 1988 and 2002 phocine distemper virus (PDV) outbreaks in European harbour seals Phoca vitulina are among the largest mass mortality events recorded in marine mammals. Despite its large impact on harbour seal population numbers, and 3 decades of studies, many questions regarding the spread and temporal origin of PDV remain unanswered. Here, we sequenced and analysed 7123 bp of the PDV genome, including the coding and non-coding regions of the entire P, M, F and H genes in tissues from 44 harbour seals to shed new light on the origin and spread of PDV in 1988 and 2002. The phylogenetic analyses trace the origin of the PDV strain causing the 1988 outbreak to between May 1987 and April 1988, while the origin of the strain causing the 2002 outbreak can be traced back to between June 2001 and May 2002. The analyses further point to several independent introductions of PDV in 1988, possibly linked to a southward mass immigration of harp seals in the winter and spring of 1987-1988. The vector for the 2002 outbreak is unknown, but the epidemiological analyses suggest the subsequent spread of PDV from the epicentre in the Kattegat, Denmark, to haul-out sites in the North Sea through several independent introductions.

Evolutionary evidence for multi-host transmission of cetacean morbillivirus

Cetacean morbillivirus (CeMV) has emerged as the pathogen that poses the greatest risk of triggering epizootics in cetacean populations worldwide, and has a high propensity for interspecies transmission, including sporadic infection of seals. In this study, we investigated the evolutionary history of CeMV by deep sequencing wild-type viruses from tissue samples representing cetacean species with different spatiotemporal origins. Bayesian phylogeographic analysis generated an estimated evolutionary rate of 2.34 × 10⁻⁴ nucleotide substitutions/site/year and showed that CeMV evolutionary dynamics are neither host-restricted nor location-restricted. Moreover, the dolphin morbillivirus strain of CeMV has undergone purifying selection without evidence of species-specific mutations. Cell-to-cell fusion and growth kinetics assays demonstrated that CeMV can use both dolphin and seal CD150 as a cellular receptor. Thus, it appears that CeMV can readily spread among multiple cetacean populations and may pose an additional spillover risk to seals.

Genetic heterogeneity of dolphin morbilliviruses detected in the Spanish Mediterranean in inter-epizootic period

Background

In the last 20 years, Cetacean Morbillivirus (CeMV) has been responsible for many die-offs in marine mammals worldwide, as clearly exemplified by the three dolphin morbillivirus (DMV) epizootics of 1990–1992, 2006–2008 and 2011 that affected Mediterranean striped dolphins (Stenella coeruleoalba). Systemic infection caused by DMV in the Mediterranean has been reported only during these outbreaks.

Results

We report the infection of five striped dolphins (Stenella coeruleoalba) stranded on the Spanish Mediterranean coast of Valencia after the last DMV outbreak that ended in 2011. Animal 1 stranded in late 2011 and Animal 2 in 2012. Systemic infection affecting all tissues was found based on histopathology and positive immunohistochemical and polymerase chain reaction positive results. Animal 3 stranded in 2014; molecular and immunohistochemical detection was positive only in the central nervous system. Animals 4 and 5 stranded in 2015, and DMV antigen was found in several tissues. Partial sequences of the DMV phosphoprotein (P), nucleoprotein (N), and hemagglutinin (H) genes were identical for Animals 2, 3, 4, and 5, and were remarkably different from those in Animal 1. The P sequence from Animal 1 was identical to that of the DMV strain that caused the epizootic of 2011 in the Spanish Mediterranean. The corresponding sequence from Animals 2–5 was identical to that from a striped dolphin stranded in 2011 on the Canary Islands and to six dolphins stranded in northeastern Atlantic of the Iberian Peninsula.

Conclusions

These results suggest the existence of an endemic infection cycle among striped dolphins in the Mediterranean that may lead to occasional systemic disease presentations outside epizootic periods. This cycle involves multiple pathogenic viral strains, one of which may have originated in the Atlantic Ocean.

Morbillivirus infection in Risso's dolphin Grampus griseus: a phylogenetic and pathological study of cases from the Canary Islands

The earliest evidence of cetacean morbillivirus (CeMV) infection dates from 1982, when the dolphin morbillivirus strain (DMV) was identified in bottlenose dolphins Tursiops truncatus stranded in the mid-Atlantic region. Since then, CeMV has been detected globally in at least 26 species of mysticetes and odontocetes, causing widespread mortality and a wide range of pathological effects. In the Canary Islands, DMV and pilot whale morbillivirus have been detected in cetacean species, including short-finned pilot whales Globicephala macrorhynchus and bottlenose dolphins. Risso's dolphins Grampus griseus have been reported year-round in waters of the Canary Islands and are considered a resident species. No information is currently available on CeMV prevalence in this species in this ocean region. We searched for evidence of CeMV infection in 12 Risso's dolphins stranded in the Canary Islands from 2003 to 2015 by means of histopathology, PCR and immunohistochemistry. PCR revealed 2 CeMV-positive animals (16.6%). Phylogenetic analysis showed that the strains from the 2 positive specimens were phylogenetically quite distant, proving that more than 1 strain infects the Risso's dolphin population in this region. We also determined that the strain detected in one of the specimens mainly circulated in the northeastern Atlantic Ocean from 2007 to 2013.

Health and Environmental Risk Assessment Project for bottlenose dolphins Tursiops truncatus from the southeastern USA. I. Infectious diseases

From 2003 to 2015, 360 free-ranging Atlantic bottlenose dolphins Tursiops truncatus inhabiting the Indian River Lagoon (IRL, n = 246), Florida, and coastal waters of Charleston (CHS, n = 114), South Carolina, USA, were captured, given comprehensive health examinations, and released as part of a multidisciplinary and multi-institutional study of individual and population health. The aim of this review is to summarize the substantial health data generated by this study and to examine morbidity between capture sites and over time. The IRL and CHS dolphin populations are affected by complex infectious and neoplastic diseases often associated with immunologic disturbances. We found evidence of infection with cetacean morbillivirus, dolphin papilloma and herpes viruses, Chlamydiaceae, a novel uncultivated strain of Paracoccidioides brasiliensis (recently identified as the causal agent of dolphin lobomycosis/lacaziasis), and other pathogens. This is the first long-term study documenting the various types, progression, seroprevalence, and pathologic interrelationships of infectious diseases in dolphins from the southeastern USA. Additionally, the study has demonstrated that the bottlenose dolphin is a valuable sentinel animal that may reflect environmental health concerns and parallel emerging public health issues.

Successful treatment of azole-resistant invasive aspergillosis in a bottlenose dolphin with high-dose posaconazole

Invasive aspergillosis due to azole-resistant Aspergillus fumigatus is difficult to manage. We describe a case of azole-resistant invasive aspergillosis in a female bottlenose dolphin, who failed to respond to voriconazole and posaconazole therapy. As intravenous therapy was precluded, high dose posaconazole was initiated aimed at achieving trough levels exceeding 3 mg/l. Posaconazole serum levels of 3–9.5 mg/l were achieved without significant side-effects. Follow-up bronchoscopy and computed tomography showed complete resolution of the lesions.

Phenotyping and comparing the immune cell populations of free-ranging Atlantic bottlenose dolphins (Tursiops truncatus) and dolphins under human care

Background

Studies suggest that free-ranging bottlenose dolphins exhibit a suppressed immune system because of exposure to contaminants or microorganisms. However, due to a lack of commercially available antibodies specific to marine mammal immune cell surface markers, the research has been indecisive. The purpose of this study was to identify cross-reactive terrestrial-specific antibodies in order to assess the changes in the immune cell populations of dolphins under human care and free-ranging dolphins. The blood and PBMC fraction of blood samples from human care and free-ranging dolphins were characterized by H&E staining of cytospin slides and flow cytometry using a panel of terrestrial-specific antibodies.

Results

In this study, we show that out of 65 terrestrial-specific antibodies tested, 11 were cross-reactive and identified dolphin immune cell populations within their peripheral blood. Using these antibodies, we found significant differences in the absolute number of cells expressing specific markers within their lymphocyte and monocyte fractions. Interestingly, the peripheral blood mononuclear cell profile of free-ranging dolphins retained an additional population of cells that divided them into two groups showing a low (<27%) or high (>56%) percentage of smaller cells resembling granulocytes.

Conclusions

We found that the cross-reactive antibodies not only identified specific changes in the immune cells of free-ranging dolphins, but also opened the possibility to investigate the causal relationship between immunosuppression and mortality seen in free-ranging dolphins.

Coinfection by Cetacean morbillivirus and Aspergillus fumigatus in a juvenile bottlenose dolphin (Tursiops truncatus) in the Gulf of Mexico

A recently deceased juvenile male bottlenose dolphin (Tursiops truncatus) was found floating in the Gulf of Mexico, off Sand Key in Clearwater, Florida. At autopsy, we identified pneumonia and a focus of malacia in the right cerebrum. Cytologic evaluation of tissue imprints from the right cerebrum revealed fungal hyphae. Fungal cultures of the lung and brain yielded Aspergillus fumigatus, which was confirmed by amplification of a portion of the fungal nuclear ribosomal internal transcribed spacer 2 region sequence. Microscopic pulmonary lesions of bronchiolar epithelial cell syncytia with intracytoplasmic and intranuclear inclusions within bronchiolar epithelial cells were suggestive of Cetacean morbillivirus (CeMV) infection. The occurrence of CeMV infection was supported by positive immunohistochemical staining for morbillivirus antigen. CeMV detection was confirmed by amplification and sequencing a portion of the morbilliviral RNA-dependent RNA polymerase gene from lung tissue. This case provides CeMV sequence data available from the Gulf of Mexico and underscores the need for genomic sequencing across diverse host, temporospatial, and population (i.e., single animal vs. mass mortality events) scales to improve our understanding of these globally emerging pathogens.

Cetacean Morbillivirus-Associated Pathology: Knowns and Unknowns

The present minireview deals with the pathology of Cetacean Morbillivirus (CeMV) infection in free-ranging cetaceans. In this respect, while "classical" CeMV-associated lesions were observed in the lung, brain, and lymphoid tissues from striped dolphins (Stenella coeruleoalba) and pilot whales (Globicephala melas) which were victims of the 1990-1992 and 2006-2008 epidemics in the Western Mediterranean, an apparent reduction in CeMV neurovirulence, along with a different viral antigen's tissue and cell distribution, were found during the 2010-2011 and the 2013 outbreaks in the same area. Of remarkable concern are also the documented CeMV ability to induce maternally acquired infections in wild cetaceans, coupled with the progressively expanding geographic and host range of the virus in both Hemispheres, as well as in conjunction with the intriguing forms of "brain-only" morbilliviral infection increasingly reported in Mediterranean-striped dolphins. Future research in this area should address the virus-host interaction dynamics, with particular emphasis on the cell receptors specifying viral tissue tropism in relation to the different cetacean species and to their susceptibility to infection, as well as to the CeMV strains circulating worldwide.

Adrenal Gland and Lung Lesions in Gulf of Mexico Common Bottlenose Dolphins (Tursiops truncatus) Found Dead following the Deepwater Horizon Oil Spill

A northern Gulf of Mexico (GoM) cetacean unusual mortality event (UME) involving primarily bottlenose dolphins (Tursiops truncatus) in Louisiana, Mississippi, and Alabama began in February 2010 and continued into 2014. Overlapping in time and space with this UME was the Deepwater Horizon (DWH) oil spill, which was proposed as a contributing cause of adrenal disease, lung disease, and poor health in live dolphins examined during 2011 in Barataria Bay, Louisiana. To assess potential contributing factors and causes of deaths for stranded UME dolphins from June 2010 through December 2012, lung and adrenal gland tissues were histologically evaluated from 46 fresh dead non-perinatal carcasses that stranded in Louisiana (including 22 from Barataria Bay), Mississippi, and Alabama. UME dolphins were tested for evidence of biotoxicosis, morbillivirus infection, and brucellosis. Results were compared to up to 106 fresh dead stranded dolphins from outside the UME area or prior to the DWH spill. UME dolphins were more likely to have primary bacterial pneumonia (22% compared to 2% in non-UME dolphins, P = .003) and thin adrenal cortices (33% compared to 7% in non-UME dolphins, P = .003). In 70% of UME dolphins with primary bacterial pneumonia, the condition either caused or contributed significantly to death. Brucellosis and morbillivirus infections were detected in 7% and 11% of UME dolphins, respectively, and biotoxin levels were low or below the detection limit, indicating that these were not primary causes of the current UME. The rare, life-threatening, and chronic adrenal gland and lung diseases identified in stranded UME dolphins are consistent with exposure to petroleum compounds as seen in other mammals. Exposure of dolphins to elevated petroleum compounds present in coastal GoM waters during and after the DWH oil spill is proposed as a cause of adrenal and lung disease and as a contributor to increased dolphin deaths.

Demographic clusters identified within the northern Gulf of Mexico common bottlenose dolphin (Tursiops truncates) unusual mortality event: January 2010-June 2013

A multi-year unusual mortality event (UME) involving primarily common bottlenose dolphins (Tursiops truncates) was declared in the northern Gulf of Mexico (GoM) with an initial start date of February 2010 and remains ongoing as of August 2014. To examine potential changing characteristics of the UME over time, we compared the number and demographics of dolphin strandings from January 2010 through June 2013 across the entire GoM as well as against baseline (1990-2009) GoM stranding patterns. Years 2010 and 2011 had the highest annual number of stranded dolphins since Louisiana’s record began, and 2011 was one of the years with the highest strandings for both Mississippi and Alabama. Statewide, annual numbers of stranded dolphins were not elevated for GoM coasts of Florida or Texas during the UME period. Demographic, spatial, and temporal clusters identified within this UME included increased strandings in northern coastal Louisiana and Mississippi (March-May 2010); Barataria Bay, Louisiana (August 2010-December 2011); Mississippi and Alabama (2011, including a high prevalence and number of stranded perinates); and multiple GoM states during early 2013. While the causes of the GoM UME have not been determined, the location and magnitude of dolphin strandings during and the year following the 2010 Deepwater Horizon oil spill, including the Barataria Bay cluster from August 2010 to December 2011, overlap in time and space with locations that received heavy and prolonged oiling. There are, however, multiple known causes of previous GoM dolphin UMEs, including brevetoxicosis and dolphin morbillivirus. Additionally, increased dolphin strandings occurred in northern Louisiana and Mississippi before the Deepwater Horizon oil spill. Identification of spatial, temporal, and demographic clusters within the UME suggest that this mortality event may involve different contributing factors varying by location, time, and bottlenose dolphin populations that will be better discerned by incorporating diagnostic information, including histopathology.

Cetacean morbillivirus: current knowledge and future directions

We review the molecular and epidemiological characteristics of cetacean morbillivirus (CeMV) and the diagnosis and pathogenesis of associated disease, with six different strains detected in cetaceans worldwide. CeMV has caused epidemics with high mortality in odontocetes in Europe, the USA and Australia. It represents a distinct species within the Morbillivirus genus. Although most CeMV strains are phylogenetically closely related, recent data indicate that morbilliviruses recovered from Indo-Pacific bottlenose dolphins (Tursiops aduncus), from Western Australia, and a Guiana dolphin (Sotalia guianensis), from Brazil, are divergent. The signaling lymphocyte activation molecule (SLAM) cell receptor for CeMV has been characterized in cetaceans. It shares higher amino acid identity with the ruminant SLAM than with the receptors of carnivores or humans, reflecting the evolutionary history of these mammalian taxa. In Delphinidae, three amino acid substitutions may result in a higher affinity for the virus. Infection is diagnosed by histology, immunohistochemistry, virus isolation, RT-PCR, and serology. Classical CeMV-associated lesions include bronchointerstitial pneumonia, encephalitis, syncytia, and lymphoid depletion associated with immunosuppression. Cetaceans that survive the acute disease may develop fatal secondary infections and chronic encephalitis. Endemically infected, gregarious odontocetes probably serve as reservoirs and vectors. Transmission likely occurs through the inhalation of aerosolized virus but mother to fetus transmission was also reported.

Review of historical unusual mortality events (UMEs) in the Gulf of Mexico (1990-2009): providing context for the multi-year northern Gulf of Mexico cetacean UME declared in 2010

An unusual mortality event (UME) was declared for cetaceans in the northern Gulf of Mexico (GoM) for Franklin County, Florida, west through Louisiana, USA, beginning in February 2010 and was ongoing as of September 2014. The 'Deepwater Horizon' (DWH) oil spill began on 20 April 2010 in the GoM, raising questions regarding the potential role of the oil spill in the UME. The present study reviews cetacean mortality events that occurred in the GoM prior to 2010 (n = 11), including causes, durations, and some specific test results, to provide a historical context for the current event. The average duration of GoM cetacean UMEs prior to 2010 was 6 mo, and the longest was 17 mo (2005-2006). The highest number of cetacean mortalities recorded during a previous GoM event was 344 (in 1990). In most previous events, dolphin morbillivirus or brevetoxicosis was confirmed or suspected as a causal factor. In contrast, the current northern GoM UME has lasted more than 48 mo and has had more than 1000 reported mortalities within the currently defined spatial and temporal boundaries of the event. Initial results from the current UME do not support either morbillivirus or brevetoxin as primary causes of this event. This review is the first summary of cetacean UMEs in the GoM and provides evidence that the most common causes of previous UMEs are unlikely to be associated with the current UME.

A systematic health assessment of indian ocean bottlenose (Tursiops aduncus) and indo-pacific humpback (Sousa plumbea) dolphins incidentally caught in shark nets off the KwaZulu-Natal Coast, South Africa

Coastal dolphins are regarded as indicators of changes in coastal marine ecosystem health that could impact humans utilizing the marine environment for food or recreation. Necropsy and histology examinations were performed on 35 Indian Ocean bottlenose dolphins (Tursiops aduncus) and five Indo-Pacific humpback dolphins (Sousa plumbea) incidentally caught in shark nets off the KwaZulu-Natal coast, South Africa, between 2010 and 2012. Parasitic lesions included pneumonia (85%), abdominal and thoracic serositis (75%), gastroenteritis (70%), hepatitis (62%), and endometritis (42%). Parasitic species identified were Halocercus sp. (lung), Crassicauda sp. (skeletal muscle) and Xenobalanus globicipitis (skin). Additional findings included bronchiolar epithelial mineralisation (83%), splenic filamentous tags (45%), non-suppurative meningoencephalitis (39%), and myocardial fibrosis (26%). No immunohistochemically positive reaction was present in lesions suggestive of dolphin morbillivirus, Toxoplasma gondii and Brucella spp. The first confirmed cases of lobomycosis and sarcocystosis in South African dolphins were documented. Most lesions were mild, and all animals were considered to be in good nutritional condition, based on blubber thickness and muscle mass. Apparent temporal changes in parasitic disease prevalence may indicate a change in the host/parasite interface. This study provided valuable baseline information on conditions affecting coastal dolphin populations in South Africa and, to our knowledge, constitutes the first reported systematic health assessment in incidentally caught dolphins in the Southern Hemisphere. Further research on temporal disease trends as well as disease pathophysiology and anthropogenic factors affecting these populations is needed.

Killer whale nuclear genome and mtDNA reveal widespread population bottleneck during the last glacial maximum

Ecosystem function and resilience is determined by the interactions and independent contributions of individual species. Apex predators play a disproportionately determinant role through their influence and dependence on the dynamics of prey species. Their demographic fluctuations are thus likely to reflect changes in their respective ecological communities and habitat. Here, we investigate the historical population dynamics of the killer whale based on draft nuclear genome data for the Northern Hemisphere and mtDNA data worldwide. We infer a relatively stable population size throughout most of the Pleistocene, followed by an order of magnitude decline and bottleneck during the Weichselian glacial period. Global mtDNA data indicate that while most populations declined, at least one population retained diversity in a stable, productive ecosystem off southern Africa. We conclude that environmental changes during the last glacial period promoted the decline of a top ocean predator, that these events contributed to the pattern of diversity among extant populations, and that the relatively high diversity of a population currently in productive, stable habitat off South Africa suggests a role for ocean productivity in the widespread decline.

Is dolphin morbillivirus virulent for white-beaked dolphins (Lagenorhynchus albirostris)?

The virulence of morbilliviruses for toothed whales (odontocetes) appears to differ according to host species. In 4 species of odontocetes, morbilliviruses are highly virulent, causing large-scale epizootics with high mortality. In 8 other species of odontocetes, including white-beaked dolphins (Lagenorhynchus albirostris), morbilliviruses have been found as an incidental infection. In these species, the virulence of morbilliviruses is not clear. Therefore, the admission of 2 white-beaked dolphins with morbillivirus infection into a rehabilitation center provided a unique opportunity to investigate the virulence of morbillivirus in this species. By phylogenetic analysis, the morbilliviruses in both animals were identified as a dolphin morbillivirus (DMV) most closely related to that detected in a white-beaked dolphin in Germany in 2007. Both animals were examined clinically and pathologically. Case No. 1 had a chronic neural DMV infection, characterized by polioencephalitis in the cerebrum and morbillivirus antigen expression limited to neurons and glial cells. Surprisingly, no nervous signs were observed in this animal during the 6 months before death. Case No. 2 had a subacute systemic DMV infection, characterized by interstitial pneumonia, leucopenia, lymphoid depletion, and DMV antigen expression in mononuclear cells and syncytia in the lung and in mononuclear cells in multiple lymphoid organs. Cause of death was not attributed to DMV infection in either animal. DMV was not detected in 2 contemporaneously stranded white-beaked dolphins. Stranding rate did not increase in the region. These results suggest that DMV is not highly virulent for white-beaked dolphins.

Relationships between in vitro lymphoproliferative responses and levels of contaminants in blood of free-ranging adult harbour seals (Phoca vitulina) from the North Sea

In vitro culture of peripheral blood leucocytes (PBLs) is currently used in toxicological studies of marine mammals. However, blood cells of wild individuals are exposed in vivo to environmental contaminants before being isolated and exposed to contaminants in vitro. The aim of this study was to highlight potential relationships between blood contaminant levels and in vitro peripheral blood lymphocyte proliferation in free-ranging adult harbour seals (Phoca vitulina) from the North Sea. Blood samples of 18 individuals were analyzed for trace elements (Fe, Zn, Se, Cu, Hg, Pb, Cd) and persistent organic contaminants and metabolites (ΣPCBs, ΣHO-PCBs, ΣPBDEs, 2-MeO-BDE68 and 6-MeO-BDE47, ΣDDXs, hexachlorobenzene, oxychlordane, trans-nonachlor, pentachlorophenol and tribromoanisole). The same samples were used to determine the haematology profiles, cell numbers and viability, as well as the in vitro ConA-induced lymphocyte proliferation expressed as a stimulation index (SI). Correlation tests (Bravais-Pearson) and Principal Component Analysis with multiple regression revealed no statistically significant relationship between the lymphocyte SI and the contaminants studied. However, the number of lymphocytes per millilitre of whole blood appeared to be negatively correlated to pentachlorophenol (r=-0.63, p=0.005). In adult harbour seals, the interindividual variations of in vitro lymphocyte proliferation did not appear to be directly linked to pollutant levels present in the blood, and it is likely that other factors such as age, life history, or physiological parameters have an influence. In a general manner, experiments with in vitro immune cell cultures of wild marine mammals should be designed so as to minimize confounding factors in which case they remain a valuable tool to study pollutant effects in vitro.

Unusual striped dolphin mass mortality episode related to cetacean morbillivirus in the Spanish Mediterranean sea

Background

In the last 20 years, Cetacean Morbillivirus (CeMV) has been responsible for many die-offs in marine mammals worldwide, as clearly exemplified by the two dolphin morbillivirus (DMV) epizootics of 1990–1992 and 2006–2008, which affected Mediterranean striped dolphins (Stenella coeruleoalba). Between March and April 2011, the number of strandings on the Valencian Community coast (E Spain) increased.

Case presentation

Necropsy and sample collection were performed in all stranded animals, with good state of conservation. Subsequently, histopathology, immunohistochemistry, conventional reverse transcription polymerase chain reaction (RT-PCR) and Universal Probe Library (UPL) RT-PCR assays were performed to identify Morbillivirus. Gross and microscopic findings compatible with CeMV were found in the majority of analyzed animals. Immunopositivity in the brain and UPL RT-PCR positivity in seven of the nine analyzed animals in at least two tissues confirmed CeMV systemic infection. Phylogenetic analysis, based on sequencing part of the phosphoprotein gene, showed that this isolate is a closely related dolphin morbillivirus (DMV) to that responsible for the 2006–2008 epizootics.

Conclusion

The combination of gross and histopathologic findings compatible with DMV with immunopositivity and molecular detection of DMV suggests that this DMV strain could cause this die-off event.

Simultaneous diagnosis of Cetacean morbillivirus infection in dolphins stranded in the Spanish Mediterranean sea in 2011 using a novel Universal Probe Library (UPL) RT-PCR assay

A highly sensitive and specific real-time (rt) RT-PCR assay has been developed for rapid, simultaneous detection of three strains of cetacean morbillivirus (CeMV). In this assay, two PCR primers and a hydrolysis probe from a commercially available Universal Probe Library (UPL) are used to amplify a highly conserved region within the fusion protein gene. RT-PCR is carried out on the same sample using two primer sets in parallel: one set detects the more virulent strains, dolphin morbillivirus (DMV) and porpoise morbillivirus (PMV), and the other set detects the least virulent and least common strain, pilot whale morbillivirus (PWMV). Sensitivity analysis using dilute samples containing purified DMV, PMV and PWMV showed that viral RNA detection limits in this UPL RT-PCR assay were lower than in a conventional RT-PCR assay. Our method gave no amplification signal with field samples positive for viruses related and unrelated to CeMV, such as phocine distemper virus (PDV). The reliability and robustness of the UPL RT-PCR assay were verified using tissue samples previously analyzed by conventional methods, as well as a panel of clinical samples suspected of containing CeMV. Using the UPL RT-PCR assay, we were able to associate DMV with a mass stranding of striped dolphins in the Spanish Mediterranean in 2011 with greater reliability than was possible with a conventional RT-PCR method. These results suggest that this UPL RT-PCR method is more sensitive and specific than the conventional approach, and that it may be an affordable and rapid test for routine diagnosis of three CeMV strains.

Pulmonary ultrasound findings in a bottlenose dolphin Tursiops truncatus population

Lung disease is common among wild and managed populations of bottlenose dolphins Tursiops truncatus. The purpose of the study was to apply standardized techniques to the ultrasound evaluation of dolphin lungs, and to identify normal and abnormal sonographic findings associated with pleuropulmonary diseases. During a 5 yr period (2005 to 2010), 498 non-cardiac thoracic ultrasound exams were performed on bottlenose dolphins at the Navy Marine Mammal Program in San Diego, California, USA. Exams were conducted as part of routine physical exams, diagnostic workups, and disease monitoring. In the majority of routine exams, no abnormal pleural or pulmonary findings were detected with ultrasound. Abnormal findings were typically detected during non-routine exams to identify and track disease progression or resolution; therefore, abnormal results are overrepresented in the study. In order of decreasing prevalence, abnormal sonographic findings included evidence of alveolar-interstitial syndrome, pleural effusion, pulmonary masses, and pulmonary consolidation. Of these findings, alveolar-interstitial syndrome was generally nonspecific as it represented several possible disease states. Pairing ultrasound findings with clinical signs was critical to determine relevance. Pleural effusion, pulmonary masses, and pulmonary consolidation were relatively straightforward to diagnose and interpret. Further diagnostics were performed to obtain definitive diagnoses when appropriate, specifically ultrasound-guided thoracocentesis, fine needle aspirates, and lung biopsies, as well as radiographs and computed tomography (CT) exams. Occasionally, post mortem gross necropsy and histopathology data were available to provide confirmation of diagnoses. Thoracic ultrasound was determined to be a valuable diagnostic tool for detecting pleural and pulmonary diseases in dolphins.

Marine mammals as sentinel species for oceans and human health

The long-term consequences of climate change and potential environmental degradation are likely to include aspects of disease emergence in marine plants and animals. In turn, these emerging diseases may have epizootic potential, zoonotic implications, and a complex pathogenesis involving other cofactors such as anthropogenic contaminant burden, genetics, and immunologic dysfunction. The concept of marine sentinel organisms provides one approach to evaluating aquatic ecosystem health. Such sentinels are barometers for current or potential negative impacts on individual- and population-level animal health. In turn, using marine sentinels permits better characterization and management of impacts that ultimately affect animal and human health associated with the oceans. Marine mammals are prime sentinel species because many species have long life spans, are long-term coastal residents, feed at a high trophic level, and have unique fat stores that can serve as depots for anthropogenic toxins. Marine mammals may be exposed to environmental stressors such as chemical pollutants, harmful algal biotoxins, and emerging or resurging pathogens. Since many marine mammal species share the coastal environment with humans and consume the same food, they also may serve as effective sentinels for public health problems. Finally, marine mammals are charismatic megafauna that typically stimulate an exaggerated human behavioral response and are thus more likely to be observed.

Morbillivirus infection in free-ranging Atlantic bottlenose dolphins (Tursiops truncatus) from the Southeastern United States: seroepidemiologic and pathologic evidence of subclinical infection

From 2003 to 2007, sera (n=234) from free-ranging Atlantic bottlenose dolphins (Tursiops truncatus) inhabiting two southeast Atlantic estuarine regions, the Indian River Lagoon (IRL), FL and Charleston, SC (CHS) were tested for antibodies to cetacean morbilliviruses as part of a multidisciplinary study of individual and population health. Positive morbillivirus titers were found on initial capture in 12 of 122 (9.8%) IRL dolphins in the absence of an epizootic. All CHS dolphins were seronegative. Positive fluctuating morbillivirus titers and seroconversion were found in IRL dolphins. Seropositivity was detected in dolphins 8-13 years of age as well as in dolphins that were alive during the 1987-1988 epizootic. During the study period, pathologic and immunohistochemical findings from stranded IRL dolphins (n=14) did not demonstrate typical morbillivirus-associated lesions or the presence of morbillivirus antigen. The findings suggest that morbillivirus infections are occurring in the absence of widespread mortality in IRL dolphins.

Sequence of the nucleocapsid gene and genome and antigenome promoters for an isolate of porpoise morbillivirus

We have determined the first complete sequence of the nucleocapsid (N) gene of the porpoise morbillivirus (PMV) as well as the genome leader and trailer sequences which encode the genome and antigenome promoters, respectively. The PMV N gene is 1686 nucleotides long with a single open reading frame (ORF) encoding a protein of 523 amino acids with a predicted molecular weight of 57.39kDa. The nucleotide sequence of the N gene shows the closest identity (89%) to that of another cetacean morbillivirus, dolphin morbillivirus (DMV). Lower degrees of identity were found with the other members of the morbilliviruses genus; 67% identity to PDV and RPV, 68% to PPRV, 69% to CDV and 70% to MV. The distance from the 3' end of the genome up to the start of the N ORF is 107 nucleotides, identical to that found in all other morbilliviruses, and encompasses the genome promoter (GP) sequence. This promoter shows the same regions of conservation as found in other morbilliviruses with repeated CXXXXX motifs at positions 79-84, 85-90, and 91-96, the same bi-partite promoter arrangement found in many paramyxoviruses. The antigenome promoter (AGP) shows a similar arrangement, indicating a high degree of conservation in these functionally important regions.

Morbilliviral infection in a pygmy sperm whale (Kogia breviceps) from Taiwanese waters

Morbilliviral infection was diagnosed in an adult male pygmy sperm whale (Kogia breviceps) from southwestern Taiwan on the basis of pathological findings, immunohistochemical staining, and reverse transcription-polymerase chain reaction. The whale was found alive stranded on the beach and died after 5 days of medical care. It was thin and had dozens of nematode in the first stomach. The lungs were dark red and heavy. Histopathological examination revealed diffuse, moderate bronchointerstitial pneumonia. Intranuclear and intracytoplasmic inclusions with occasional syncytial cell formation were noted in the lungs, lymph nodes, and spleen. The RNA extracted from lung tissue was subjected to morbilliviral gene amplification. After priming with specific oligonucleotides, the cDNA covering the phosphoprotein (P) gene was copied and then amplified by PCR. The gene fragment amplified from the lung tissue was sequenced. Phylogenetic analysis of partial P gene revealed 97.6% sequence identity to the dolphin morbillivirus and 90.2% similarity to the pilot whale morbillivirus. Morbilliviral antigens were detected in the lungs, lymph nodes, and spleen by immunohistochemistry using polyclonal antibody against rinderpest virus. This is the first report of morbilliviral infection with genetic evidence in a pygmy sperm whale from the Western Pacific Ocean around Taiwan.

Disseminated toxoplasmosis in a Mediterranean pregnant Risso's dolphin (Grampus griseus) with transplacental fetal infection

Fatal disseminated toxoplasmosis was diagnosed in a Risso's dolphin (Grampus griseus) dam and its fetus on the basis of pathologic findings, immunohistochemistry, and structure of the parasite. The dolphin was stranded alive on the Spanish Mediterranean coast and died a few hours later. At necropsy the dam was in good condition. From the standpoint of pathology, however, it had generalized lymphadenomegaly and splenomegaly, enlargement of and multifocal hemorrhage in the adrenal glands, diffuse mucosal hemorrhage of the glandular and pyloric stomach, ulcerative glossitis and stomatitis, focal erosions and reddening of the laryngeal appendix, and severe paraotic sinusitis with intralesional nematodes Crassicauda grampicola. The dolphin was pregnant, most probably in the first gestational trimester. The most prominent microscopic lesions were multifocal granulomatous encephalomyelitis, diffuse subacute interstitial pneumonia, mild multifocal necrotizing hepatitis and nonsuppurative cholangiohepatitis, gastritis and adrenalitis, mild lymphoid depletion, medullary sinus and follicular histyocitosis, and systemic hemosiderosis. The fetus had foci of coagulative and lytic necrosis in the kidneys, the lung, and the heart. Most lesions were associated with tachyzoites and tissue cysts of Toxoplasma gondii. The diagnosis was confirmed immunohistochemically. This is the first report on toxoplasmosis in a Risso's dolphin (G. griseus) and on transplacental transmission to an early-stage fetus in any cetaceans.

Emerging morbillivirus infections of marine mammals: development of two diagnostic approaches

In the last 13 years, four viruses belonging in the Morbillivirus genus of the Paramyxoviridae family have emerged as significant causes of disease and mortality in marine mammals. The viruses involved are canine distemper virus (CDV) in seals and polar bears, dolphin morbillivirus (DMV) and porpoise morbillivirus (PMV) in cetaceans, and phocine distemper virus (PDV) in pinnipeds. The two cetacean morbilliviruses (DMV and PMV) are now considered to be the same viral species, named cetacean morbillivirus (CMV). All three morbillivirus species (CDV, CMV, and PDV) are genetically and antigenically related and cross-react in various serological tests. The diagnosis of morbilliviral infections in marine mammal specimens poses two challenges. First, various marine mammal species can be infected by more than one closely related but distinct morbilliviruses, making definitive virus identification unattainable by classical virology methods. Second, standard immunological reagents such as anti-species conjugates are unavailable for most marine mammal species, rendering definitive serological diagnosis difficult by classical serological techniques. The objectives of this study were to develop two diagnostic approaches that alleviate these difficulties, providing simple, rapid, and cost-effective diagnostic methods. For nucleic acid detection, reverse transcription-polymerase chain reaction (RT-PCR) and restriction endonuclease digestions were used to differentiate the three viruses. For antibody detection, a monoclonal antibody-based competitive enzyme-linked immunosorbent assay (c-ELISA) was used on sera from several species, thus avoiding the need for multiple anti-species enzyme conjugates.

Morbilliviral dermatitis in seals

A juvenile female hooded seal (Cystophora cristata) and a juvenile male harp seal (Phoca groenlandica) stranded separately on the New Jersey (USA) coast and were taken to a marine mammal rehabilitation center. Both were lethargic and emaciated, had dermatitis, and died. Histologic skin lesions in the seals were similar and consisted of epidermal and follicular epithelial hyperplasia, hyperkeratosis, degeneration, and necrosis. The most distinctive finding was extensive syncytial zones bounded superficially by hyperkeratosis and deeply by hyperplastic basal cells. Eosinophilic intracytoplasmic inclusion bodies were present in epithelial cells. Morbilliviral antigen was demonstrated in the skin lesions by immunohistochemistry. Phocine distemper virus was detected in the skin by reverse transcription polymerase chain reaction and a phocine distemper virus-specific probe using the Southern blot technique. This is the first report of morbilliviral dermatitis in marine mammals.

Morbillivirus in common seals stranded on the coasts of Belgium and northern France during summer 1998

Sixteen common seals (Phoca vitulina) were stranded on the Belgian and northern French coasts during the summer of 1998. Eleven (10 pups and one adult) were sampled for histopathological, immunohistochemical, serological, bacteriological, parasitological and virological investigations. The main gross findings were severe emaciation, acute haemorrhagic enteritis, acute pneumonia, interstitial pulmonary emphysema and oedema, and chronic ulcerative stomatitis. Microscopical lung findings were acute to subacute pneumonia with interstitial oedema and emphysema. Severe lymphocytic depletion was observed in lymph nodes. Severe acute to subacute meningoencephalitis was observed in one animal. Specific staining with two monoclonal antibodies directed against canine distemper virus (CDV) and phocine distemper virus was observed in a few lymphocytes in the spleen and lymph nodes of three seals. Anti-CDV neutralising antibodies were detected in sera from six animals. Seven of the seals were positive by reverse transcriptase-PCR for the morbillivirus phosphoprotein gene. The lesions observed were consistent with those in animals infected by a morbillivirus, and demonstrated that distemper has recently recurred in North Sea seals.

Monoclonal antibody-based competitive enzyme-linked immunosorbent assay for detection of morbillivirus antibody in marine mammal sera

A competitive enzyme-linked immunosorbent assay (cELISA), using two monoclonal antibodies (MAbs), was developed and compared with the standard virus neutralization test (VNT) for detecting antibodies against canine distemper virus (CDV) and phocine distemper virus (PDV) in sera from dogs and various species of marine mammals. The test depends on the blocking of MAb binding to solid-phase antigen in the presence of positive serum. Test conditions were optimized by using control VNT-negative and -positive sera specific for CDV and PDV. A positive cutoff value of 30% inhibition, which represents the mean cutoff of a VNT-negative population (n = 623) plus 2 standard deviations, was adopted for the test. A total of 736 serum samples were tested by the new cELISA and by the VNT as the "gold standard." An unexpected but useful finding was the ability of this CDV- and PDV-specific cELISA to also detect antibodies against the related pair dolphin morbillivirus and porpoise morbillivirus. Based on a subpopulation of 625 sera used in statistical analyses, the overall sensitivity and specificity of cELISA relative to those of the VNT were 94.9 and 97.7%, respectively. Because the cELISA proved to be nearly as sensitive and specific as the VNT while being simpler and more rapid, it would be an adequate screening test for suspect CDV or PDV cases and would also be useful for epidemiological surveillance of morbilliviral infections in marine mammal populations.

Molecular genetic evidence of a novel morbillivirus in a long-finned pilot whale (Globicephalus melas)

A long-finned pilot whale with morbilliviral disease was stranded in New Jersey. An immunohistochemical stain demonstrated morbilliviral antigen. Reverse transcriptase-polymerase chain reaction for morbillivirus P and N genes was positive. Novel sequences most closely related to, but distinct from, those of dolphin and porpoise morbilliviruses suggest that this virus may represent a third member of the cetacean morbillivirus group.

Non-purulent meningoencephalomyelitis of a Pacific striped dolphin (Lagenorhynchus obliquidens). The first evidence of morbillivirus infection in a dolphin at the Pacific Ocean around Japan

On March 22, 1998, a mature, male, hyposthenic Pacific striped dolphin (Lagenorhynchus obliquidens) was stranded at Aoshima Beach in Miyazaki prefecture, Japan. A necropsy performed 14 hr after death revealed mild diffuse congestion and edema of the leptomeninges and mild pulmonary atelectasis. Histopathologically, non-purulent inflammatory were observed throughout the cerebrum, thalamus, midbrain, pons, medulla oblongata, and spinal cord. Hematoxylin and eosin stain revealed no viral inclusion bodies. Immunohistochemistry using a monoclonal antibody against nucleoprotein of canine distemper virus (CDV-NP) revealed a number of CDV-NP-positive granular deposits in the cytoplasm and cell processes of the degenerating or intact neurons. The present paper is a first report of spontaneously occurred morbillivirus infection in a dolphin at the Pacific Ocean around Japan.

Epizootic of morbilliviral disease in common dolphins (Delphinus delphis ponticus) from the Black sea

Forty-seven common dolphins (Delphinus delphis ponticus) were stranded on the northern shores of the Black Sea between mid-July and early September 1994, more than in previous or subsequent years. Two of the 47 dolphins were examined in detail to try to determine the cause of the increased stranding rate. Their lesions included broncho-interstitial pneumonia with type II epithelial cell hyperplasia and multinucleate syncytial cells, neuronal necrosis, gliosis, and non-suppurative meningitis of the brain, necrotic stomatitis, gastroenteritis and cholangitis, and lymphoid depletion of the spleen and lymph nodes. The diseased tissues stained positive in an immunoperoxidase test, using a polyclonal antiserum to measles virus as the primary antibody, and electron microscopy showed that they contained regularly-shaped intranuclear particles about 22 nm in diameter. They were positive by the polymerase chain reaction (PCR) for the nucleoprotein gene of morbillivirus. However, there was no evidence of morbillivirus in frozen tissues either by virus isolation or by antigen capture ELISA. The concentration of sigma DDTS in the blubber of both dolphins was about 50 to 100 times higher than the levels in toothed cetaceans from the North Sea, North Atlantic Ocean, and Baltic Sea. The lesions were consistent with those found in other species with morbilliviral disease, and the positive immunoperoxidase test, PCR and electron microscopical examination confirmed a morbillivirus as the primary cause of these lesions.

Morbillivirus infections in aquatic mammals

Morbillivirus infections which were not documented in aquatic mammals until 1988, have caused at least five epizootics in these species during the last 10 years. Affected populations include European harbour seals (Phoca vitulina) and grey seals (Halichoerus grypus) in 1998, Baikal seals (Phoca siberica) in Siberia from 1987-1988, striped dolphins (Stenella coeruleoalba) in the Mediterranean Sea from 1990-1992 and bottlenose dolphins (Tursiops truncatus) along the eastern coast of the United States from 1987-1988 and in the Gulf of Mexico from 1993-1994. Clinical signs and lesions in affected animals were similar to those of canine distemper. Lesions were mainly seen in lung, central nervous and lymphoid tissues and included formation of intranuclear and intracytoplasmic inclusion bodies. Syncytia were commonly found in lung and lymphoid tissues of cetaceans but not of pinnipeds. Antigenic and molecular biological studies indicate that a newly discovered morbillivirus, termed phocine distemper virus, and canine distemper virus were responsible for recent pinniped epizootics; cetacean die-offs were caused by strains of a second, newly recognized cetacean morbillivirus. Serological evidence of morbillivirus infection has been identified in a broad range of marine mammal populations and recent epizootics probably resulted from transfer of virus to immunologically-naive populations.

Histologic, immunohistochemical, and polymerase chain reaction studies of bottlenose dolphins from the 1987-1988 United States Atlantic coast epizootic

Tissues from 95 bottlenose dolphins (Tursiops truncatus) that died during the 1987-1988 US Atlantic coast epizootic and 11 bottlenose dolphins that died along the Atlantic coast prior to 1987 were examined histologically and immunohistochemically. Polymerase chain reaction (PCR) testing was performed on 36 of the epizootic and all of the pre-1987 cases. Epizootic cases had syncytia and rare intranuclear and intracytoplasmic inclusion bodies within lung, lymph node, and spleen. Lymphoid depletion was present in lymph node, spleen, and gut-associated lymphoid tissue of epizootic cases. Pre-1987 cases did not have these pulmonary and lymphoid lesions. A larger percentage of epizootic than pre-1987 cases had bacterial and/or fungal infections (primarily pneumonias), pulmonary and lymphoid tissue histiocytosis, mucocutaneous ulcers, and evidence of negative energy balance. Immunohistochemically, 49/95 (52%) epizootic dolphins were positive for morbilliviral antigen. Morbilliviral antigen was detected in lung, lymph node, spleen, thymus, skin, tongue, esophagus, liver, pancreas, gastrointestinal tract, urinary bladder, oviduct, and mammary gland by immunohistochemistry. PCR testing identified morbilliviral RNA in 35/36 (97%) epizootic cases tested. Neither morbilliviral antigen nor morbilliviral RNA were detected in pre-1987 cases. Histologic, immunohistochemical, and PCR results provide strong evidence that morbillivirus infection was the primary cause of the 1987-1988 bottlenose dolphin epizootic.