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.

Background: Herpesvirus infections in cetaceans have always been attributed to theAlphaherpesvirinaeandGammaherpesvirinaesubfamilies. 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.

The emergence of Brucella infections in marine mammals is a growing concern. The present study reports two cases of systemic Brucella pinnipedialis infection detected in bottlenose dolphins ( Tursiops truncatus ) pair stranded together in the Cantabrian coast of Spain. Both animals showed systemic lesions associated with the Brucella infection, more severe in the younger dolphin, considered the likely offspring of the other individual. Real-time PCR, bacterial culture, and whole-genome sequencing were used to detect and characterize the Brucella strains involved in both dolphins. The phylogenetic analysis performed on the Brucella genomes retrieved revealed that the species involved was B. pinnipedialis (ST25). Both animals resulted seropositive in a commercial multispecies blocking ELISA but tested negative in the standard Rose Bengal test. To the best of our knowledge, this is the first report of a systemic infection resulting in various lesions associated with Brucella pinnipedialis (ST25) in two bottlenose dolphins. It is also the initial isolation of Brucella in the milk of a non-pregnant or non-aborting female cetacean likely stranded with its offspring. These findings provide new insights into the epidemiology and clinical impact of B. pinnipedialis infection in cetaceans and underscore the importance of continued diagnostic surveillance to gain better understanding of brucellosis effects and transmission in marine mammal populations. IMPORTANCE: Brucella spp. are zoonotic pathogens that can affect both terrestrial and marine mammals. Brucella ceti has been identified in various cetacean species, but only one sequence type (ST27) has been reported in humans. However, it is important to conduct surveillance studies to better understand the impact of marine Brucella species on marine mammals, a typically understudied host group. Here, we describe a systemic infection by two related strains of Brucella pinnipedialis (ST25) in a couple of live-stranded bottlenose dolphins, with more severe lesions in the younger animal. Furthermore, B. pinnipedialis was first detected in milk from a female cetacean that stranded with its offspring. Our study reveals novel insights into the epidemiology and pathological consequences of B. pinnipedialis infections in cetaceans, emphasizing the crucial importance of ongoing surveillance and accurate diagnosis to understand the impact of this pathogen on marine mammal populations.

Herpesvirus has the potential to infect a wide variety of animal species. In cetaceans, Alpha- and/or Gammaherpesvirinae have been identified in eight families of odontocetes, and one family of mysticetes. In May 2022, an adult humpback whale (Megaptera novaeangliae) was found stranded in Valencia, Spain. The whale was emaciated, in poor body condition, with multiple lacerations on the dorsal fin and a high number of epibionts of the Cyamidae family, known as whale lice. The individual had been previously released from a ghost net entanglement 5 days before becoming stranded. In a closer examination, various skin lesions were observed, including chronic, proliferative, and erosive dermatitis and a large ulcer extending to the deep dermis. As part of the infectious disease surveillance programme, molecular testing was performed on skin samples for herpesvirus, cetacean morbillivirus, and poxvirus. A positive result for herpesvirus was obtained from one of the skin lesions. The sequence was found to belong to the Alphaherpesvirinae subfamily, and it was closely related to alphaherpesvirus sequences from a fin whale (Balaenoptera physalus) and a humpback whale. Cetacean morbillivirus and poxvirus testing was negative. To the authors’ knowledge, this is the first report of herpesvirus in a humpback whale from the Mediterranean Sea. Reports on herpesvirus detection or infection in humpback whales (only species within the genus Megaptera) are scarce. In consequence, future virological assessments of humpback whales should include testing for herpesvirus.

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. 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. 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).