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

Cetacean Host-Pathogen Interaction(s): Critical Knowledge Gaps

Within the broad range of viral and non-viral pathogens infecting cetaceans, Cetacean Morbillivirus (CeMV), Herpesvirus (HV), Brucella ceti, and Toxoplasma gondii are of special concern, due to their impact(s) on the health and conservation of free-ranging cetacean populations worldwide (1). The most \u201cparadigmatic\u201d example in this direction is represented by CeMV, which throughout the last 3 decades has caused more than 10 mass mortality outbreaks among different cetacean species and populations across the globe (2, 3)

Genomic and structural investigation on dolphin morbillivirus (DMV) in Mediterranean fin whales (Balaenoptera physalus).

Dolphin morbillivirus (DMV) has been deemed as one of the most relevant threats for fin whales (Balaenoptera physalus) being responsible for a mortality outbreak in the Mediterranean Sea in the last years. Knowledge of the complete viral genome is essential to understand any structural changes that could modify virus pathogenesis and viral tissue tropism. We report the complete DMV sequence of N, P/V/C, M, F and H genes identified from a fin whale and the comparison of primary to quaternary structure of proteins between this fin whale strain and some of those isolated during the 1990-'92 and the 2006-'08 epidemics. Some relevant substitutions were detected, particularly Asn52Ser located on F protein and Ile21Thr on N protein. Comparing mutations found in the fin whale DMV with those occurring in viral strains of other cetacean species, some of them were proven to be the result of diversifying selection, thus allowing to speculate on their role in host adaptation and on the way they could affect the interaction between the viral attachment and fusion with the target host cells

An Unparalleled Sexual Dimorphism of Sperm Whale Encephalization

The sperm whale Physeter macrocephalus (Linnaeus, 1758) is the largest toothed whales and possesses the highest absolute values for brain weight on the planet (together with the killer whale Orcinus orca). Former calculations of the encephalization quotient (EQ), which is used to compare brain size of different mammalian species, showed that the sperm whale brain is smaller than expected for its body mass. However, the data reported in the literature and formerly used to calculate the sperm whale EQ suffered from a potential bias due to the tendency to measure mostly larger males of this extreme sexually dimorphic species. Accordingly, we found that the brains of female sperm whales are close to the absolute weight range of the males, but, given the much lower body mass of females, their EQ results more than double of what reported before for the whole species, and is thus nearly into the primate range (female EQ = 1.28, male EQ = 0.56). This sexual dimorphism is unique among mammals. Female sperm whales live in large families in which social interactions and inter-individual communication are essential, while adult males live solitarily. Thus the particular sex-specific behavior of SWs may have led to a maternally-driven social evolution, and eventually contributed to achieve female EQ values (but not male EQs) among the highest ever calculated for mammals with respect to their large body mass

Death associated to methicillin resistant staphylococcus aureus ST8 infection in two dolphins maintained under human care, Italy

The present study describes the isolation of Methicillin-resistant Staphylococcus aureus (MRSA) from respiratory tract of 2 dolphins of different origin, a stranded juvenile Risso's dolphin (Grampus griseus) and a captive born common bottlenose dolphin (Tursiops truncatus) calf, which died in the same institution at 1-month distance from the other. A complete microbiological and genetic investigation confirmed the presence of MRSA clone-complex 8, sequence type (ST) 8, spa-type t008 in both individuals. This strain differs from the one previously reported in walruses and dolphins and has never been described in dolphins before, but it is randomly isolated from Italian human patients. Vertical transmission of the infection may also occurs in other species and considering the description and location of the pathological lesions, this seems to be the most likely route of transmission implied in the young bottlenose dolphin. Staphylococcus aureus is known as an opportunistic agent, usually secondary to other pathogens, but its multiple antibiotic resistance and its zoonotic implications suggest a thorough and strict application of animal management hygiene protocols

Genomic and structural investigation on Dolphin Morbillivirus (DMV) in Mediterranean fin whales (Balaenoptera physalus)

Dolphin Morbillivirus (DMV) has been deemed as one of the most relevant threats for fin whales (Balaenoptera physalus) being responsible for a mortality outbreak in the Mediterranean Sea in the last years. Knowledge of the complete viral genome is essential to understand any structural changes that could modify virus pathogenesis and viral tissue tropism. We report the complete DMV sequence of N, P/V/C, M, F and H genes identified from a fin whale and the comparison of primary to quaternary structure of proteins between this fin whale strain and some of those isolated during the 1990-‘92 and the 2006-‘08 epidemics. Some relevant substitutions were detected, particularly Asn52Ser located on F protein and Ile21Thr on N protein. Comparing mutations found in the fin whale DMV with those occurring in viral strains of other cetacean species, some of them were proven to be the result of diversifying selection, thus allowing to speculate on their role in host adaptation and on the way they could affect the interaction between the viral attachment and fusion with the target host cells

Comparative Immunology of Marine Mammals

Marine mammals (MMs) are regarded as valuable bioindicators with tremendous potential for public health. However, many aspects of their immune system remain poorly understood. Monitoring immune responses of MMs is pivotal for the health assessment of both individuals and populations, as well as providing the scientific basis for analyzing the anthropogenic environmental impact on marine ecosystems and marine-terrestrial interphases. For instance, the increasing susceptibility of Mediterranean whale and dolphin populations to various diseases has been linked to a possible negative influence of multiple environmental factors on the immune system of MMs. The currently limited knowledge on MM immunology has mainly centered on: (i) lymphocyte transformation assays; (ii) natural killer cell activity; (iii) phagocytic activity and respiratory burst; (iv) humoral immune responses; (v) cytokines and (vi) acute phase immune responses. Therefore, further research is essential for deepening our understanding of the specificity of the host immune response in MMs, with a particular emphasis on the genesis and dynamics of (i) cytokine \u2018networks\u2019 or \u2018signatures\u2019; (ii) transcriptional regulation of immune cells and (iii) major immunomodulators. High-throughput molecular techniques, such as transcriptomic analysis and RNA sequencing, may enable the characterization of immune gene responses at the transcriptomic level. This integrative and holistic approach requires sophisticated tools and methods capable of unveiling the diversity of immune cells and immunologically relevant molecules that orchestrate environmental adaptation and immune protection against pathogens in MMs. This Research Topic aims to provide a comprehensive overview of the current knowledge of MM immunology with a particular emphasis on structural and functional studies at the protein and cellular level. We wish to encourage and coordinate studies and investigations in order to fill gaps of knowledge in this field. This article collection aims to help gain more data regarding: a) The characterization of the immune system in several species of MMs, i.e. cetaceans, pinnipeds and sirenians; b) The interplay between the host immune system and the most relevant pathogens, e.g., Morbillivirus, Brucella, Toxoplasma gondii and c) The possible interplay between the immune system and contaminants

Heartworm (Dirofilaria immitis) infection in a leopard (Panthera pardus pardus) housed in a zoological park in north-eastern Italy

Canine heartworm (cHW) disease is now recognised as potential cause of serious disease in cats and other felids, especially in endemic areas. In March 2009, a 23-years-old male African leopard (Panthera pardus pardus) housed in a zoological park located in the Province of Padova (Veneto Region), a cHW endemic area of the north-eastern Italy, died and was immediately necropsied. A cloth completely occluding the pyloric lumen was considered the presumptive cause of death. During necropsy, six nematodes (4 males and 2 females) were found within the right ventricle of the heart and the pulmonary artery. Diagnosis of HW (Dirofilaria immitis) infection was carried out by morphological features of adult worms and microfilariae, and then confirmed by detection of circulating HW antigens using a commercial SNAP kit (IDEXX Laboratories inc., USA). D. immitis infection was also confirmed by PCR amplification of the 5S ribosomal spacer region, performed on worm fragments and microfilaraemic blood samples obtained from the right ventricle of the heart. A glomerulonephritis of immuno-mediated origin and most likely associated with the HW infection is also reported. HW chemoprophylaxis and annual serological testing on wild felids housed outdoors in endemic cHW disease areas are recommended. This is the first diagnosis of D. immitis infection in an exotic felid in Italy