Presence of herpesvirus in striped dolphins stranded during the cetacean morbillivirus epizootic along the Mediterranean Spanish coast in 2007

A systematic review on global zoonotic virus-associated mortality events in marine mammals

Marine mammals play a critical role as sentinels for tracking the spread of zoonotic diseases, with viruses being the primary causative factor behind infectious disease induced mortality events. A systematic review was conducted to document marine mammal mortality events attributed to zoonotic viral infections in published literature across the globe. This rigorous search strategy yielded 2883 studies with 88 meeting inclusion criteria. The studies spanned from 1989 to 2023, with a peak in publications observed in 2020. Most of the included studies were retrospective, providing valuable insights into historical trends. The United States (U.S.) reported the highest number of mortality events followed by Spain, Italy, Brazil and the United Kingdom. Harbor seals were the most impacted species, particularly in regions like Anholt, Denmark and the New England Coast, U.S. Analysis revealed six main viruses responsible for mortality events, with Morbillivirus causing the highest proportion of deaths. Notably, the occurrence of these viral events varied geographically, with distinct patterns observed in different regions. Immunohistochemistry emerged as the most employed detection method. This study underscores the importance of global surveillance efforts in understanding and mitigating the impact of viral infections on marine mammal populations, thereby emphasizing the necessity of collaborative One Health approaches to address emerging threats at the human-animal-environment interface. Additionally, the potential transfer of zoonotic viruses to aquatic organisms used in food production, such as fish and shellfish, highlights the broader implications for food safety, food security and public health.

Coinfection with Dolphin Morbillivirus (DMV) and Gammaherpesvirus in a Spinner Dolphin (Stenella longirostris) Stranded in Sri Lanka

Following the X-Press Pearl maritime disaster off the coast of Sri Lanka, a stranded spinner dolphin (Stenella longirostris) was recovered, and the cause of death was investigated. Post-mortem examinations revealed evidence of by-catch, but a natural coinfection with dolphin morbillivirus (DMV) and gammaherpesvirus was detected by further analyses, marking the first documented case of a dual viral infection in this species within the region. Molecular diagnostics, including PCR and sequencing, were performed on tissue imprints collected on FTA® cards, confirming the presence of DMV in the prescapular lymph node and gammaherpesvirus in the lesions in the oral cavity. The concurrent detection of DMV and gammaherpesvirus raises significant concerns regarding the potential impacts of environmental stressors, such as chemical pollutants from the X-Press Pearl maritime disaster, on exacerbating susceptibility to viral infections in marine mammals. These findings highlight the need for ongoing surveillance of cetacean populations in the Indian Ocean to better understand pathogen circulation and health and conservation implications of anthropogenic activities on the marine ecosystem.

Herpesvirus surveillance in stranded striped dolphins (Stenella coeruleoalba) and bottlenose dolphins (Tursiops truncatus) from Italy with emphasis on neuropathological characterization

Herpesvirus (HV) is widely distributed among cetacean populations, with the highest prevalence reported in the Mediterranean Sea. In this study, a comprehensive analysis was conducted, including epidemiological, phylogenetic, and pathological aspects, with particular emphasis on neuropathology, to better understand the impact of HV in these animals. Our results show a higher presence of HV in males compared to females, with males exhibiting a greater number of positive tissues. Additionally, adults were more frequently affected by HV infection than juveniles, with no infections detected in calves or neonates. The affected species were striped (Stenella coeruleoalba) and bottlenose dolphins (Tursiops truncatus). The highest positivity rates were observed in the genital system, cerebrum, and skin tissues. Phylogenetic analysis indicated a higher occurrence of Gammaherpesvirus (GHV) sequences but increased genetic diversity within Alphaherpesvirus (AHV). Key neuropathological features included astro-microgliosis (n = 4) and meningitis with minimal to mild perivascular cuffing (n = 2). The presence of concurrent infections with other pathogens, particularly cetacean morbillivirus (CeMV), underscores the complex nature of infectious diseases in cetaceans. However, the presence of lesions at the Central Nervous System (CNS) with molecular positivity for GHV, excluding the involvement of other potential neurotropic agents, would confirm the potential of this HV subfamily to induce neurological damage. Pathological examination identified lesions in other organs that could potentially be associated with HV, characterized by lymphoid depletion and tissue inflammation. These findings enhance our understanding of HV in odontocetes and highlight the need for ongoing research into the factors driving these infections and their broader implications.

Pathogen Prevalence in Cetaceans Stranded along the Italian Coastline between 2015 and 2020

The monitoring of stranded marine mammals represents a strategic method to assess their health, conservation status, and ecological role in the marine ecosystem. Networks worldwide track stranding events for the passive monitoring of mortality patterns, emerging and reemerging pathogens, climate change, and environmental degradation from a One Health perspective. This study summarizes pathogen prevalence data from the Italian Stranding Network (ISN) derived from post-mortem investigations on cetaceans found dead stranded along the Italian coastline between 2015 and 2020. The decomposition of the carcasses and logistics limited the post-mortem examination to 585 individuals, out of 1236 single-stranding reports. The most relevant pathogens identified were Cetacean Morbillivirus, Herpesvirus, Brucella spp., and Toxoplasma gondii, whose roles as environmental stressors are well known, despite their real impact still needing to be investigated in depth. Statistical analysis showed that age and sex seem to be positively related to the presence of pathogens. This study represents the first step in harmonizing post-mortem investigations, which is crucial for evidence-based conservation efforts. Implementing diagnostic and forensic frameworks could offer an indirect insight into the systematic monitoring of diseases to improve the identification of regional and temporal hotspots in which to target specific mitigation, management, and conservation strategies.

Novel Gammaherpesvirus Infections in Narrow-Ridged Finless Porpoise (Neophocaena asiaeorientalis) and False Killer Whales (Pseudorca crassidens) in the Republic of Korea

A female narrow-ridged finless porpoise (Neophocaena asiaeorientalis) stranded on a beach on Jeju Island showed epithelial proliferative skin lesions on its body. Two false killer whales (Pseudorca crassidens), caught using nets near Gangneung and Samcheok, respectively, had multiple plaques on their penile epidermis. Histological examination of the epidermis revealed that all the lesions had common features, including accentuated rete pegs, ballooning changes, and eosinophilic intranuclear inclusion (INI) bodies. Based on the histopathological results, herpesvirus infection was suspected, and thus further analysis was conducted using herpesvirus-specific primers. Based on nested polymerase chain reaction (PCR) tests using the herpesvirus-detectable primers, the PCR products demonstrated two fragments: a 222-base-pair (bp) sequence of the DNA polymerase gene, SNUABM_CeHV01, showing 96.4% identity with a bottlenose dolphin herpesvirus from the Jeju narrow-ridged finless porpoise; and a 222 bp sequence of the DNA polymerase gene, SNUABM_CeHV02, showing 95.95% identity with the same bottlenose dolphin herpesvirus from the Gangneung and Samcheok false killer whales. The significance of this study lies in its ability to demonstrate the existence of novel cetacean herpesviruses in South Korean seawater, representing an important step forward in studying potentially harmful pathogens that affect endangered whale and dolphin populations.

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.

Viral skin diseases in odontocete cetaceans: gross, histopathological, and molecular characterization of selected pathogens

Fifty-five skin lesions from 31 stranded cetaceans along the Canary coasts (2011-2021) were submitted to macroscopic, histological, and molecular analyses to confirm infection by cetacean poxvirus, herpesvirus and cetacean morbillivirus. They were macroscopically categorized into eight categories with respective subcategories according to their color, shape, size, and consistency. Cetacean poxvirus was detected in 54.54% of the skin lesions through real-time and conventional PCRs based on the DNA polymerase gene. Additionally, herpesvirus and morbillivirus were currently detected from 43.63 and 1.82% of the cutaneous lesions, respectively. Coinfection of poxvirus and herpesvirus was detected in nine of them (16.36%), which makes the present study the first to report coinfection by both pathogens in skin lesions in cetaceans. A plausible approach to histopathological characterization of poxvirus-and herpesvirus-positive skin lesions was established. Hyperkeratosis, acanthosis, ballooning degeneration, and intracytoplasmic inclusion bodies in vacuolized keratinocytes through the stratum spinosum were common findings in poxvirus skin lesions. Alphaherpesvirus was associated with a prominent acanthotic epidermis, moderate necrosis, multifocal dyskeratosis, and irregular keratinocytes with both cellular and nuclei pleomorphism. The common histopathological findings of both pathogens were observed in coinfection lesions. However, those associated with herpesvirus were considerably more remarkable. Relationships between molecular and microscopic findings were observed for the lesions that showed tattoo-like and tortuous patterns. Further multidisciplinary diagnostic studies of infected skin lesions are needed to understand the epidemiology of these emerging infectious diseases.

First description of a lesion in the upper digestive mucosa associated with a novel gammaherpesvirus in a striped dolphin (Stenella coeruleoalba) stranded in the Western Mediterranean Sea

BACKGROUND

A wide variety of lesions have been associated with herpesvirus in cetaceans. However, descriptions of herpesvirus infections in the digestive system of cetaceans are scarce.

CASE REPORT

A young female striped dolphin stranded in the Valencian Community (Spain) on the 6th August 2021. The animal showed external macroscopic lesions suggestive of an aggressive interaction with bottlenose dolphins (rake marks in the epidermis). Internally, the main findings included congestion of the central nervous system and multiple, well-defined, whitish, irregularly shaped, proliferative lesions on the oropharyngeal and laryngopharyngeal mucosa. Histopathology revealed lymphoplasmacytic and histiocytic meningoencephalitis, consistent with neuro brucellosis. The oropharyngeal and laryngopharyngeal plaques were comprised histologically of focally extensive epithelial hyperplasia. As part of the health surveillance program tissue samples were tested for cetacean morbillivirus using a real-time reverse transcription-PCR, for Brucella spp. using a real-time PCR, and for herpesvirus using a conventional nested PCR. All samples were negative for cetacean morbillivirus; molecular positivity for Brucella spp. was obtained in pharyngeal tonsils and cerebrospinal fluid; herpesvirus was detected in a proliferative lesion in the upper digestive mucosa. Phylogenetic analysis showed that the herpesvirus sequence was included in the Gammaherpesvirinae subfamily. This novel sequence showed the greatest identity with other Herpesvirus sequences detected in skin, pharyngeal and genital lesions in five different species.

CONCLUSIONS

To the best of the authors' knowledge, this is the first report of a proliferative lesion in the upper digestive mucosa associated with gammaherpesvirus posititvity in a striped dolphin (Stenella coeruleoalba).

Molecular Characterization of Herpesviral Encephalitis in Cetaceans: Correlation with Histopathological and Immunohistochemical Findings

Simple Summary

In this study we describe the molecular and pathological characteristics of alpha- and gamma-herpesvirus infection of the central nervous system of stranded cetaceans and correlate them with viral load, immunohistochemical findings and biological data such as age, sex, and the presence of co-infections. The viruses (alpha- and gamma-herpesvirus) were detected in twelve out of 103 analysed stranded cetaceans and were associated with a wide range of histopathological lesions, as previously described for these and other species. In five out the twelve animals, lesions were severe enough (malacia, neuronal necrosis and neuronophagia) to cause death. Intranuclear inclusions bodies were present in brain tissue samples from half of the HV-positive animals, indicating that the injury was due to an infective agent belonging to a group of filterable viruses. These results are in accordance with immunohistochemical findings, as all the brain tissue samples with INIBs were immunolabeled with Anti-HSV1. Males, juveniles, and calves were predominantly infected among the analysed cetaceans and a 41.6% (5/12) incidence of co-infections in the brain was detected, with three animals co-infected with Dolphin Morbillivirus (DMV). In this study, we present, to the best of our knowledge, the first histopathological evidence of superinfection between HV and DMV pathogens in brain tissue.

Abstract

Herpesviruses are causative agents of meningitis and encephalitis in cetaceans, which are among the main leading known natural causes of death in these species. Brain samples from 103 stranded cetaceans were retrospectively screened for the presence of herpesvirus DNA in the brain. Molecular detection of Cetacean Morbillivirus was performed in HV positive brain cases. Histopathologic evaluation of brain samples included the presence or absence of the following findings (n = 7): meningitis, perivascular cuffings, microgliosis, intranuclear inclusion bodies, malacia, neuronal necrosis and neurophagic nodules, and haemorrhages. Histological evidence of the involvement of other etiological agents led to complementary analysis. We detected the presence of alpha and gamma-HVs in 12 out of 103 (11.6%) brain samples from stranded cetaceans of five different species: one bottlenose dolphin, six striped dolphins, three Atlantic spotted dolphins, one Cuvier’s beaked whale, and one common dolphin. Pathogenic factors such as viral strain, age, sex, and the presence of co-infections were analysed and correlated with the brain histopathological findings in each case. Herpesvirus was more prevalent in males, juveniles, and calves and a 41.6% incidence of co-infections in the brain was detected in our study: three with Dolphin Morbillivirus, one with Staphilococcus aureus septicaemia and one with Brucella spp.

Molecular Diagnosis of Cetacean Morbillivirus in Beaked Whales Stranded in the Canary Islands (1999–2017)

A retrospective survey for detecting the cetacean morbillivirus (CeMV) was carried out in beaked whales (BWs) stranded in the Canary Islands (1999–2017). CeMV is responsible for causing worldwide epizootic events with the highest mass die-offs in cetaceans, although the epidemic status of the Canarian Archipelago seems to be that of an endemic situation. A total of 319 tissue samples from 55 BWs (35 Cuvier’s BWs and 20 specimens belonging to the Mesoplodon genus) were subjected to the amplification of a fragment of the fusion protein (F) and/or phosphoprotein (P) genes of CeMV by means of one or more of three polymerase chain reactions (PCR). RNA integrity could not be demonstrated in samples from 11 animals. Positivity (dolphin morbillivirus strain (DMV)) was detected in the skin sample of only a subadult male Cuvier’s BW stranded in 2002, being the earliest confirmed occurrence of DMV in the Cuvier’s BW species. The obtained P gene sequence showed the closest relationship with other DMVs detected in a striped dolphin stranded in the Canary Islands in the same year. A phylogenetic analysis supports a previous hypothesis of a cross-species infection and the existence of the circulation of endemic DMV strains in the Atlantic Ocean similar to those later detected in the North-East Atlantic, the Mediterranean Sea and the South-West Pacific.

Highly divergent herpesviruses in threatened river dolphins from Brazil

River dolphins are a highly threatened polyphyletic group comprised of four odontocete families: Iniidae, Pontoporiidae, Lipotidae, and Platanistidae, the first two endemic to South America. To address the knowledge gap regarding infectious agents in this cetacean group, we surveyed the presence of herpesviruses by PCR in skin and/or blood samples of live-captured Amazon (Inia geoffrensis, n = 25) and Bolivian (Inia boliviensis, n = 22) river dolphins of the Amazon basin and in selected tissue samples of franciscanas (Pontoporia blainvillei, n = 27) stranded or bycaught in southeastern Brazil. Additionally, available franciscana tissue samples were examined by histopathology. Herpesvirus DNA was amplified in 13 Bolivian river dolphins (59.1%, 95% CI 38.5–79.6%) and 14 franciscanas (51.9%, 95% CI 33.0–70.7%). All Amazon river dolphins were herpesvirus-negative. Two different herpesviruses were found in Bolivian river dolphins: a previously known gammaherpesvirus detected in blood and/or skin samples of all positive individuals and a novel alphaherpesvirus in the skin of one animal. A new gammaherpesvirus was found in several franciscana samples—the first herpesvirus recorded in Pontoporiidae. Intranuclear inclusion bodies consistent with herpesvirus were observed in the lymph node of one franciscana. The high divergence among the obtained herpesviruses and those previously described can be explained by viral-host coevolution, and by the fact that these populations are fairly isolated.

Systematic Determination of Herpesvirus in Free-Ranging Cetaceans Stranded in the Western Mediterranean: Tissue Tropism and Associated Lesions

The monitoring of herpesvirus infection provides useful information when assessing marine mammals’ health. This paper shows the prevalence of herpesvirus infection (80.85%) in 47 cetaceans stranded on the coast of the Valencian Community, Spain. Of the 966 tissues evaluated, 121 tested positive when employing nested-PCR (12.53%). The largest proportion of herpesvirus-positive tissue samples was in the reproductive system, nervous system, and tegument. Herpesvirus was more prevalent in females, juveniles, and calves. More than half the DNA PCR positive tissues contained herpesvirus RNA, indicating the presence of actively replicating virus. This RNA was most frequently found in neonates. Fourteen unique sequences were identified. Most amplified sequences belonged to the Gammaherpesvirinae subfamily, but a greater variation was found in Alphaherpesvirinae sequences. This is the first report of systematic herpesvirus DNA and RNA determination in free-ranging cetaceans. Nine (19.14%) were infected with cetacean morbillivirus and all of them (100%) were coinfected with herpesvirus. Lesions similar to those caused by herpesvirus in other species were observed, mainly in the skin, upper digestive tract, genitalia, and central nervous system. Other lesions were also attributable to concomitant etiologies or were nonspecific. It is necessary to investigate the possible role of herpesvirus infection in those cases.

Contribution to Herpesvirus Surveillance in Beaked Whales Stranded in the Canary Islands

Simple Summary

Herpesviruses (HVs) are a large family of DNA viruses infecting animals (including insects and mollusks) and humans. Cetaceans can be also infected by HVs presenting different range of lesions, from dermatitis to meningoencephalitis, or being asymptomatic. Several studies have addressed the question of HVs in cetaceans, although no previous systematic survey of HV in beaked whales (BWs) (Ziphiidae family) has been previously performed. The family Ziphiidae, which includes 22 species in 6 genera, is one of the most widespread families of cetaceans, with a strict oceanic habitat pattern. Beaked whales, Cuvier’s BW in particular, are one of the deepest diving whales and are of particular interest because of a notable relationship between military operations employing mid-frequency sonar and the mass stranding of BWs in different geographic areas, including the Canary Islands. In this study, we analyzed 55 BWs (294 samples) stranded in the Canary Islands from 1990 to 2017 by molecular methods (conventional nested polymerase chain reaction). Our results showed that 8 BWs were infected by HVs, although only three animals displayed lesions indicative of active viral replication. Phylogenetic analysis suggests that HV-BW sequences are species-specific, although more studies are needed to better address this question.

Abstract

Herpesviruses (HVs) (Alpha- and Gammaherpesvirinae subfamilies) have been detected in several species of cetaceans with different pathological implications. However, available information on their presence in beaked whales (BWs) is still scarce. In this study, a total of 55 BWs (35 Ziphius cavirostris and 20 animals belonging to the Mesoplodon genus) were analyzed. Samples (n = 294) were obtained from BWs stranded along the coasts of the Canary Islands (1990–2017). Molecular detection of HV was performed by means of a conventional nested PCR based on the DNA polymerase gene. Herpesvirus was detected in 14.45% (8/55) of the analyzed BWs, including 2 positive animals from a previous survey. A percentage positivity of 8.57% was found within the Cuvier’s BW group, while the percentage of positivity rose to 25% within the Mesoplodon genus group (three M. densirostris, one M. europaeus, and one M. bidens). All the obtained sequences from this study belonged to the Alphaherpesvirinae subfamily, from which three are considered novel sequences, all of them within the Mesoplodon genus group. In addition, to our knowledge, this is the first description of HV infection in Gervais’ and Sowerby’s BWs. Three out of eight HV-positive BWs displayed histopathological lesions indicative of active viral replication.

Alpha- and gammaherpesviruses in stranded striped dolphins (Stenella coeruleoalba) from Spain: first molecular detection of gammaherpesvirus infection in central nervous system of odontocetes

BACKGROUND

Herpesvirus infections in cetaceans have always been attributed to the Alphaherpesvirinae and Gammaherpesvirinae subfamilies. To date, gammaherpesviruses have not been reported in the central nervous system of odontocetes.

CASE PRESENTATION

A mass stranding of 14 striped dolphins (Stenella coeruleoalba) occurred in Cantabria (Spain) on 18th May 2019. Tissue samples were collected and tested for herpesvirus using nested polymerase chain reaction (PCR), and for cetacean morbillivirus using reverse transcription-PCR. Cetacean morbillivirus was not detected in any of the animals, while gammaherpesvirus was detected in nine male and one female dolphins. Three of these males were coinfected by alphaherpesviruses. Alphaherpesvirus sequences were detected in the cerebrum, spinal cord and tracheobronchial lymph node, while gammaherpesvirus sequences were detected in the cerebrum, cerebellum, spinal cord, pharyngeal tonsils, mesenteric lymph node, tracheobronchial lymph node, lung, skin and penile mucosa. Macroscopic and histopathological post-mortem examinations did not unveil the potential cause of the mass stranding event or any evidence of severe infectious disease in the dolphins. The only observed lesions that may be associated with herpesvirus were three cases of balanitis and one penile papilloma.

CONCLUSIONS

To the authors' knowledge, this is the first report of gammaherpesvirus infection in the central nervous system of odontocete cetaceans. This raises new questions for future studies about how gammaherpesviruses reach the central nervous system and how infection manifests clinically.

Novel herpesviruses in riverine and marine cetaceans from South America

Herpesvirus (HV) infections in cetaceans are frequently associated with skin and mucosal lesions. Although HV infections have been reported worldwide, their occurrence in southern Atlantic marine mammals is still poorly understood. We tested skin, oral and genital mucosal beta-actin PCR-positive samples from 109 free-ranging Brazilian cetaceans using a universal herpesvirus DNA polymerase PCR. Herpesvirus-positive skin samples from a Guiana dolphin (Sotalia guianensis), a dwarf sperm whale (Kogia sima), a Bolivian river dolphin (Inia boliviensis), and a lingual sample from an Atlantic spotted dolphin (Stenella frontalis) were histologically evaluated. Additional tissue samples from these animals were also PCR-positive for HV, including a novel sequence obtained from the dwarf sperm whale's stomach and mesenteric lymph node. Four novel HV species were detected in the Guiana dolphin (one), the dwarf sperm whale (two) and the Bolivian river dolphin (one). The cutaneous lesions (marked, focally extensive, chronic proliferative dermatitis) of the Guiana dolphin and the Bolivian river dolphin were similar to previous HV reports in cetaceans, despite the absence of intranuclear inclusion bodies. This is the largest HV survey in South American cetaceans and the first detection of HV infection in riverine dolphins worldwide.

Herpesvirus infection in marine mammals: A retrospective molecular survey of stranded cetaceans in the Portuguese coastline

Herpesvirus (HVs) infection has already been reported in cetaceans, but available information on its epidemiology is scarce. In this study we surveyed a total of 179 cetaceans belonging to 6 different species. Samples were obtained from cetaceans stranded along the Portuguese coastline, belonging to populations that roam the north-east region of the Atlantic Ocean. Detection of HVs was performed by conventional nested PCR. Amplicons were sequenced by Sanger's method and sequences used to construct phylogenetic trees by Maximum Likelihood method. Our results show that prevalence of positive samples, among fresh carcasses, reached 14.3% (10/70) and both alpha and gammaherpesvirus were detected. Histopathology showed that herpesvirus infection varied from absence of signs compatible with disease, localized genital lesions and systemic disease. Phylogenetic analysis revealed three clusters within the alphaherpesvirus family; within the gammaherpesvirus no subdivision was detected. All clusters included animals from different species and geographic origins. In seven of the positive HVs samples, co-infections with other agents such as morbillivirus and toxoplasma gondii were detected. The viral nucleotide sequences were not assigned to a specific animal species, nor presented a given geographic distribution, which may imply a wider distribution of herpesvirus in these animal populations. Our results are also the first report of herpesvirus infection in common dolphins (Delphinus delphis), with both alpha and gammaherpesvirus detected.

Pathologic findings and causes of death of stranded cetaceans in the Canary Islands (2006-2012)

This study describes the pathologic findings and most probable causes of death (CD) of 224 cetaceans stranded along the coastline of the Canary Islands (Spain) over a 7-year period, 2006-2012. Most probable CD, grouped as pathologic categories (PCs), was identified in 208/224 (92.8%) examined animals. Within natural PCs, those associated with good nutritional status represented 70/208 (33.6%), whereas, those associated with significant loss of nutritional status represented 49/208 (23.5%). Fatal intra- and interspecific traumatic interactions were 37/208 (17.8%). Vessel collisions included 24/208 (11.5%). Neonatal/perinatal pathology involved 13/208 (6.2%). Fatal interaction with fishing activities comprised 10/208 (4.8%). Within anthropogenic PCs, foreign body-associated pathology represented 5/208 (2.4%). A CD could not be determined in 16/208 (7.7%) cases. Natural PCs were dominated by infectious and parasitic disease processes. Herein, our results suggest that between 2006 and 2012, in the Canary Islands, direct human activity appeared responsible for 19% of cetaceans deaths, while natural pathologies accounted for 81%. These results, integrating novel findings and published reports, aid in delineating baseline knowledge on cetacean pathology and may be of value to rehabilitators, caregivers, diagnosticians and future conservation policies.

Occlusive mycotic tracheobronchitis and systemic Alphaherpesvirus coinfection in a free-living striped dolphin Stenella coeruleoalba in Italy

A juvenile female striped dolphin Stenella coeruleoalba live stranded on 4 March 2016 at Alassio, western Ligurian Sea coast, Italy. The dolphin died shortly after stranding, and a complete postmortem examination was performed. Necropsy revealed severe tracheal occlusion and unilateral bronchial stenosis with luminal accumulation of abundant green-yellow mucous-gelatinous material. Histological features suggestive of tracheobronchial aspergillosis were observed. Cultures of lung tissue and tracheo-bronchial exudate isolated Aspergillus fumigatus, identified by a Microseq D2 LSUrDNA fungal sequencing kit. A pan-Herpesvirus nested-PCR assay on frozen samples obtained from multiple organs was positive. Phylogenetic analysis on the partial DNA polymerase gene revealed that the striped dolphin isolate was closely related to known cetacean Alphaherpesvirus sequences from the same host species. Attempted virus isolation was unsuccessful. The tissue levels of different persistent organic pollutants and the toxicological stress, evaluated using a theoretical model, showed a severely impaired immune response. This study reports the first case of occlusive mycotic tracheobronchitis in a free-living cetacean and the first molecular identification of an Alphaherpesvirus in a free-ranging striped dolphin stranded on the coast of Italy.

Herpesviral infection in a Guiana dolphin ( Sotalia guianensis) from the northern coast of Brazil

We describe herein herpesvirus-associated genital lesions in a Guiana dolphin ( Sotalia guianensis) from the northern Brazilian coast. Papillary lesions on the vulva, with epithelial hyperplasia, swollen keratinocytes, and intranuclear inclusions, were positive for a herpesvirus ( Gammaherpesvirinae subfamily).

First molecular determination of herpesvirus from two mysticete species stranded in the Mediterranean Sea

BACKGROUND

Herpesvirus can infect a wide range of animal species: mammals, birds, reptiles, fish, amphibians and bivalves. In marine mammals, several alpha- and gammaherpesvirus have been identified in some cetaceans and pinnipeds species. To date, however, this virus has not been detected in any member of the Balaenoptera genus.

CASE PRESENTATION

Herpesvirus was determined by molecular methods in tissue samples from a male fin whale juvenile (Balaenoptera physalus) and a female common minke whale calf (Balaenoptera acutorostrata) stranded on the Mediterranean coast of the Region of Valencia (Spain). Samples of skin and penile mucosa from the fin whale and samples of skin, muscle and central nervous system tissue from the common minke whale tested positive for herpesvirus based on sequences of the DNA polymerase gene. Sequences from fin whale were identical and belonged to the Alphaherpesvirinae subfamily. Only members of the Gammaherpesvirinae subfamily were amplified from the common minke whale, and sequences from the muscle and central nervous system were identical. Sequences in GenBank most closely related to these novel sequences were viruses isolated from other cetacean species, consistent with previous observations that herpesviruses show similar phylogenetic branching as their hosts.

CONCLUSIONS

To our knowledge, this is the first molecular determination of herpesvirus in the Balaenoptera genus. It shows that herpesvirus should be included in virological evaluation of these animals.

Mx1 and Mx2 key antiviral proteins are surprisingly lost in toothed whales

Viral outbreaks in dolphins and other Delphinoidea family members warrant investigation into the integrity of the cetacean immune system. The dynamin-like GTPase genes Myxovirus 1 (Mx1) and Mx2 defend mammals against a broad range of viral infections. Loss of Mx1 function in human and mice enhances infectivity by multiple RNA and DNA viruses, including orthomyxoviruses (influenza A), paramyxoviruses (measles), and hepadnaviruses (hepatitis B), whereas loss of Mx2 function leads to decreased resistance to HIV-1 and other viruses. Here we show that both Mx1 and Mx2 have been rendered nonfunctional in Odontoceti cetaceans (toothed whales, including dolphins and orcas). We discovered multiple exon deletions, frameshift mutations, premature stop codons, and transcriptional evidence of decay in the coding sequence of both Mx1 and Mx2 in four species of Odontocetes. We trace the likely loss event for both proteins to soon after the divergence of Odontocetes and Mystocetes (baleen whales) ∼33-37 Mya. Our data raise intriguing questions as to what drove the loss of both Mx1 and Mx2 genes in the Odontoceti lineage, a double loss seen in none of 56 other mammalian genomes, and suggests a hitherto unappreciated fundamental genetic difference in the way these magnificent mammals respond to viral infections.

First Gammaherpesvirus detection in a free-living Mediterranean bottlenose dolphin

Recently, herpes viruses have been detected in different cetacean species from the Atlantic and in Mediterranean striped dolphins (Stenella coeruleoalba). While pathogens such as cetacean morbillivirus have been widely studied following recent epizootics, herpesvirus (HV) distribution and pathogenic effects in cetaceans are still understudied. This study reports the first molecular identification of a Gammaherpesvirus in the genital mucosa of a free-living Mediterranean bottlenose dolphin (Tursiops truncatus) stranded off the coast of central Italy. Sequenced herpesviral PCR product was closely related to other HVs recently isolated in the genital mucosa of various cetacean species.

Retrospective study of etiologic agents associated with nonsuppurative meningoencephalitis in stranded cetaceans in the canary islands

Nineteen natural cases of etiologically undetermined encephalitides in free-ranging cetaceans were studied retrospectively. Histological examination of the brains revealed variable degrees of nonsuppurative encephalitis or meningoencephalitis, characterized predominantly by perivascular lymphohistiocytic infiltrates. A PCR assay was used on brain and other available tissues to detect the presence of morbillivirus, herpesvirus, West Nile virus, Toxoplasma gondii, and Brucella spp. In addition, immunohistochemical (IHC) staining was performed on selected tissues to determine the presence of morbilliviral antigens. Six animals (5 striped dolphins and 1 common dolphin) showed IHC and/or molecular evidence of morbilliviral antigens and/or genomes, mainly in brain tissue. Conventional nested PCR detected herpesviral DNA in brain tissue samples from two striped dolphins. There was no evidence of West Nile virus, T. gondii, or Brucella spp. in any of the brain tissue samples examined. The information presented here increases the number of confirmed morbillivirus-positive cases within the Canarian archipelago from two previously reported cases to eight. Furthermore, a new nested-PCR method for the detection of morbillivirus is described here. Regarding herpesvirus, the phylogenetic analysis performed in the current study provides valuable information about a possible pathogenic branch of cetacean alphaherpesviruses that might be responsible for some fatal cases worldwide.

Cetacean strandings in Italy: an unusual mortality event along the Tyrrhenian Sea coast in 2013

An unusual mortality event involving cetaceans, mainly striped dolphins Stenella coeruleoalba (Meyen, 1833), occurred along the Tyrrhenian Sea coast of Italy during the first 3 mo of 2013. Based on post-mortem analyses carried out according to body condition on 66 dolphins (54% of stranded animals), several hypotheses to explain the causes of this mortality event were proposed. Although no definitive conclusions can be drawn, dolphin morbillivirus was deemed the most likely cause, although other infectious agents (including Photobacterium damselae damselae and herpesvirus) or environmental factors may also have contributed to this recent mortality event.

Herpes virus infection associated with interstitial nephritis in a beaked whale (Mesoplodon densirostris)

Background

The capacity for herpesvirus to cause disease in cetaceans is unclear and may be varied depending on the different conditions of individuals and between different species. Kidney pathology and intralesional virus-associated infection have been rarely reported in cetaceans.

Result

On April 2004, an old adult male Blainville’s beaked whale (Mesoplodon densirostris) 420 cm long with a poor body condition was stranded on Tenerife Island. During necropsy, no gross lesions were observed in the kidneys. However, membranous glomerulonephritis, multifocal interstitial lymphoplasmacytic nephritis and acute multifocal necrotizing tubulointerstitial nephritis with intranuclear inclusion bodies was diagnosed by histological analysis. Tissue samples were submitted for bacteriological analysis and molecular viral screening.

Conclusion

A novel alpha herpesvirus associated with interstitial nephritis was identified in an old adult male Blainville's beaked whale (M. densirostris) with a poor body condition stranded in the Canary Islands. This report suggests that identification of herpesvirus infection could be used as a differential diagnosis for interstitial nephritis in cetaceans.

Isolation of a novel herpesvirus from a Pacific white-sided dolphin

During establishment of primary cell culture from the kidney of a dead Pacific white-sided dolphin (Lagenorhynchus obliquidens), a cytopathic effect was observed. Polymerase chain reaction with a set of herpesvirus consensus primers yielded a fragment of the expected size. Nucleotide sequencing of the product indicated that the isolated virus was closely related to an alphaherpesvirus detected in a bottlenose dolphin in the United States, but the sequence identity at the protein level was low (86.6 %). Phylogenetic analysis of the encoded sequence confirmed that the new isolate belonged to the subfamily Alphaherpesvirinae and clustered together with other cetacean alphaherpesviruses. The complete gene encoding glycoprotein B (2,757 bp) was amplified from the novel isolate; the encoded protein was compared with the corresponding protein of other herpesviruses, revealing that this virus belongs to the genus Varicellovirus. Taken together, these results suggest that this virus corresponds to a novel herpesvirus capable of infecting Pacific white-sided dolphins.

Papillomaviruses and herpesviruses: who is who in genital tumor development of free-ranging Atlantic bottlenose dolphins (Tursiops truncatus)?

The number of studies addressing neoplasia in marine mammals has recently increased, giving rise to concern whether such lesions could be reflective of an emerging infectious disease. Eight species-specific viruses, seven papillomaviruses (PVs) and two herpesviruses (HVs) have separately been shown to be associated with genital tumors in Atlantic bottlenose dolphins (Tursiops truncatus, Tt): TtPV1-6, as well as HVs provisionally assigned the names DeHV4 and -5 (Delphinid HVs). A definite causal role of these viruses in cell transformation remains to be demonstrated. Concurrent PV- and HV-infection has never been reported in marine mammals. DNA extractions from biopsies of genital tumors derived from 15 free-ranging Atlantic bottlenose dolphins were selected for molecular examination. Polymerase chain reaction (PCR) analyses revealed the presence of DeHV4, while a serological screening using an antibody-based TtPV enzyme-linked immunosorbent assay (ELISA) demonstrated previous and/or current infection of the HV-positive dolphins with at least one TtPV type. Therefore, care must be taken when drawing conclusions about viral causalities in tumor development, since the "hit and run" and other mechanisms have been described for types of both viral families. This study presents the first evidence of marine mammals having a history of PV- as well as HV-infection and discusses the disputed effects of viral co-infection.

Post-epizootic chronic dolphin morbillivirus infection in Mediterranean striped dolphins Stenella coeruleoalba

Dolphin morbillivirus (DMV) has caused 2 epizootics with high mortality rates on the Spanish Mediterranean coast, in 1990 and 2006-07, mainly affecting striped dolphins Stenella coeruleoalba. Following the first epizootic unusual DMV infections affecting only the central nervous system of striped dolphins were found, with histological features similar to subacute sclerosing panencephalitis and old dog encephalitis, the chronic latent localised infections caused by defective forms of measles virus and canine distemper virus, respectively. Between 2008 and 2010, monitoring by microscopic and immunohistochemical (IHC) studies of 118 striped dolphins stranded along Catalonia, the Valencia Region and Andalusia showed similar localised DMV nervous system infections in 25.0, 28.6 and 27.4% of cases, respectively, with no significant differences among regions or sex. The body length of DMV-infected dolphins was statistically greater than that of non-infected dolphins (196.5 vs. 160.5 cm; p < 0.001). Molecular detection of DMV was performed by 2 different RT-PCR techniques amplifying a 429 bp fragment and a 78 bp fragment both within the phosphoprotein (P) gene. The 429 bp RT-PCR results contradicted the IHC-DMV results as only 3 of 6 dolphins with positive IHC-DMV had positive PCR results. All 6 cases were positive with the 78 bp RT-PCR. These findings contraindicate the use of the 429 bp RT-PCR protocol based on the P gene to detect this specific form of DMV. DMV localised nervous infection constitutes the most relevant single cause of stranding and death in Mediterranean striped dolphins in the years following a DMV epizootic, and it might even overwhelm the effects of the epizootic itself, at least in 2007.

Biologically threatened dolphins and whales

Among the several threats to which free-ranging cetaceans are exposed, a number of biological noxae are believed to represent a serious hazard to their health and conservation on a global scale, with special emphasis on the Mediterranean Sea. These pathogens include viral agents such as Morbillivirus, which during the last 25 years have caused dramatic epidemics and die-offs among several aquatic mammal species and populations worldwide, as well as Herpesvirus, protozoan agents such as Toxoplasma gondii and bacterial pathogens such as Brucella spp.

Systemic herpesvirus and morbillivirus co-infection in a striped dolphin (Stenella coeruleoalba)

During 2007 a dolphin morbillivirus epizootic affected the western Mediterranean and several striped dolphins (Stenella coeruleoalba) stranded on the Catalonian coasts. One of those animals had severe lymphoid depletion, necrosis and syncytial formation in lymph nodes and spleen, with large basophilic nuclear inclusions compatible with herpesvirus detected by immunohistochemical and ultrastructural examination. Non-suppurative encephalitis with associated morbillivirus antigen and morbillivirus antigen within alveolar macrophages were also observed. A pan-herpesvirus nested polymerase chain reaction amplified a sequence virtually identical to two cetacean herpesvirus sequences previously identified in systemic infections in an Atlantic Cuvier's beaked whale (Ziphius cavirostris) and in a Mediterranean striped dolphin. The herpesviral infection was probably secondary to the immunosuppression caused by the morbillivirus. To our knowledge, this is the first report of a cetacean co-infected by dolphin morbillivirus and herpesvirus with evidence of lesions attributable to both viruses.

Sometimes sperm whales (Physeter macrocephalus) cannot find their way back to the high seas: a multidisciplinary study on a mass stranding

Background

Mass strandings of sperm whales (Physeter macrocephalus) remain peculiar and rather unexplained events, which rarely occur in the Mediterranean Sea. Solar cycles and related changes in the geomagnetic field, variations in water temperature and weather conditions, coast geographical features and human activities have been proposed as possible causes. In December 2009, a pod of seven male sperm whales stranded along the Adriatic coast of Southern Italy. This is the sixth instance from 1555 in this basin.

Methodology/Principal Findings

Complete necropsies were performed on three whales whose bodies were in good condition, carrying out on sampled tissues histopathology, virology, bacteriology, parasitology, and screening of veins looking for gas emboli. Furthermore, samples for age determination, genetic studies, gastric content evaluation, stable isotopes and toxicology were taken from all the seven specimens.

The animals were part of the same group and determined by genetic and photo-identification to be part of the Mediterranean population. Causes of death did not include biological agents, or the “gas and fat embolic syndrome”, associated with direct sonar exposure. Environmental pollutant tissue concentrations were relatively high, in particular organochlorinated xenobiotics. Gastric content and morphologic tissue examinations showed a prolonged starvation, which likely caused, at its turn, the mobilization of lipophilic contaminants from the adipose tissue. Chemical compounds subsequently entered the blood circulation and may have impaired immune and nervous functions.

Conclusions/Significance

A multi-factorial cause underlying this sperm whales' mass stranding is proposed herein based upon the results of postmortem investigations as well as of the detailed analyses of the geographical and historical background. The seven sperm whales took the same “wrong way” into the Adriatic Sea, a potentially dangerous trap for Mediterranean sperm whales. Seismic surveys should be also regarded as potential co-factors, even if no evidence of direct impact has been detected.