Partially observed epidemics in wildlife hosts: modelling an outbreak of dolphin morbillivirus in the northwestern Atlantic, June 2013-2014

MORBIDITY AND MORTALITY PATTERNS OF INDIAN RIVER LAGOON COMMON BOTTLENOSE DOLPHINS (TURSIOPS TRUNCATUS TRUNCATUS) 2002-2020

Mortality patterns in cetaceans are critical to understanding population health. Common bottlenose dolphins (Tursiops truncatus truncatus) inhabiting the Indian River Lagoon (IRL), Florida have been subjected to four unusual mortality events (UMEs), highlighting the need to evaluate morbidity and mortality patterns. Complete gross examinations were conducted on 392 stranded dolphins and histopathological analyses were conducted for 178 animals (2002-2020). The probable causes of mortality were grouped by etiologic category: degenerative, metabolic, nutritional, inflammatory (infectious and noninfectious disease), and trauma. Probable cause of mortality was determined in 57% (223/392) of cases. Inflammatory disease (infectious/noninfectious) and trauma were the most common. Inflammatory disease accounted for 41% of cases (91/223), with the lungs (pneumonia) most commonly affected. Trauma accounted for 36% of strandings (80/223). The majority of trauma cases were due to anthropogenic activities (entanglement, fishing gear or other debris ingestion, and propeller strikes), accounting for 58% of trauma cases (46/80). Natural trauma (prey-associated esophageal obstruction or asphyxiation, shark bites, and stingray interactions) accounted for 12% of all cases (26/223), and trauma of undetermined origin was identified in 4% of cases (8/223). Starvation or inanition (nutritional) were the probable cause of mortality in 17% of cases and peaked during the 2013 UME (61% of cases). Degenerative and metabolic etiologies accounted for 5% of cases. This study represents the most comprehensive evaluation of morbidity and mortality patterns in IRL dolphins. Because IRL dolphins are routinely exposed to anthropogenic threats and have endured multiple UMEs, these baseline data are critical to the conservation and management of this population.

Historical isolates of dolphin morbillivirus: origin and new data

Dolphin morbillivirus (DMV) was isolated in striped dolphins Stenella coeruleoalba from the Mediterranean Sea stranded along the coast of Spain during a lethal epidemic that killed thousands of individuals in 1990-1992. Though some of these isolates (MUC, 16A and the reference strain) have been extensively characterised, details on their origin were not reported in the literature, and records for these isolates are often difficult to trace and are, sometimes, erroneous. Here, we provide unpublished biological and histopathological data for these isolates, summarize the literature on their characterization and make suggestions for future studies.

Gut bacterial communities in Atlantic bottlenose dolphins (Tursiops truncatus) throughout a disease-driven (Morbillivirus) unusual mortality event

Gut microbiomes are important determinants of animal health. In sentinel marine mammals where animal and ocean health are connected, microbiome impacts can scale to ecosystem-level importance. Mass mortality events affect cetacean populations worldwide, yet little is known about the contributory role of their gut bacterial communities to disease susceptibility and progression. Here, we characterized bacterial communities from fecal samples of common bottlenose dolphins, Tursiops truncatus, across an unusual mortality event (UME) caused by dolphin Morbillivirus (DMV). 16S rRNA gene sequence analysis revealed similar diversity and structure of bacterial communities in individuals stranding before, during, and after the 2013-2015 Mid-Atlantic Bottlenose Dolphin UME and these trends held in a subset of dolphins tested by PCR for DMV infection. Fine-scale shifts related to the UME were not common (10 of 968 bacterial taxa) though potential biomarkers for health monitoring were identified within the complex bacterial communities. Accordingly, acute DMV infection was not associated with a distinct gut bacterial community signature in T. truncatus. However, temporal stratification of DMV-positive dolphins did reveal changes in bacterial community composition between early and late outbreak periods, suggesting that gut community disruptions may be amplified by the indirect effects of accumulating health burdens associated with chronic morbidity.

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.

A Review of Circumpolar Arctic Marine Mammal Health-A Call to Action in a Time of Rapid Environmental Change

The impacts of climate change on the health of marine mammals are increasingly being recognised. Given the rapid rate of environmental change in the Arctic, the potential ramifications on the health of marine mammals in this region are a particular concern. There are eleven endemic Arctic marine mammal species (AMMs) comprising three cetaceans, seven pinnipeds, and the polar bear (Ursus maritimus). All of these species are dependent on sea ice for survival, particularly those requiring ice for breeding. As air and water temperatures increase, additional species previously non-resident in Arctic waters are extending their ranges northward, leading to greater species overlaps and a concomitant increased risk of disease transmission. In this study, we review the literature documenting disease presence in Arctic marine mammals to understand the current causes of morbidity and mortality in these species and forecast future disease issues. Our review highlights potential pathogen occurrence in a changing Arctic environment, discussing surveillance methods for 35 specific pathogens, identifying risk factors associated with these diseases, as well as making recommendations for future monitoring for emerging pathogens. Several of the pathogens discussed have the potential to cause unusual mortality events in AMMs. Brucella, morbillivirus, influenza A virus, and Toxoplasma gondii are all of concern, particularly with the relative naivety of the immune systems of endemic Arctic species. There is a clear need for increased surveillance to understand baseline disease levels and address the gravity of the predicted impacts of climate change on marine mammal species.

The potential use of skin and liver as biomarkers to estimate mercury in the brain, kidney, and muscle of bottlenose dolphins (Tursiops truncatus)

For marine cetaceans, Hg biomagnification can negatively affect neurological, hepatic, renal, and immune functions. To evaluate the use of biomarkers for Hg in dolphins, multiple tissues were analyzed from 127 stranded common bottlenose dolphins (Tursiops truncatus) from the estuarine and oceanic waters of Virginia, USA. Twenty-two percent of liver Hg concentrations exceeded the published observed effect level for liver abnormalities, and 26 % of cerebrum samples exceeded the published threshold for neurochemical changes, suggesting that Hg may have impacted dolphin health. Mercury tissue levels were similar to or lower than those reported from other locations (liver range: 1.4-943 μg/g-dw). Significant correlations were found between tissue types, indicating that skin or liver can be used as a biomarker to estimate the total Hg concentrations in the other tissue types (kidney, liver, cerebrum, cerebellum, pons). This is the first study to measure Hg concentrations in multiple brain regions of T. truncatus.

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.

Specific capture and whole-genome phylogeography of Dolphin morbillivirus

Dolphin morbillivirus (DMV) is considered an emerging threat having caused several epidemics worldwide. Only few DMV genomes are publicly available. Here, we report the use of target enrichment directly from cetacean tissues to obtain novel DMV genome sequences, with sequence comparison and phylodynamic analysis. RNA from 15 tissue samples of cetaceans stranded along the Italian and French coasts (2008-2017) was purified and processed using custom probes (by bait hybridization) for target enrichment and sequenced on Illumina MiSeq. Data were mapped against the reference genome, and the novel sequences were aligned to the available genome sequences. The alignment was then used for phylogenetic and phylogeographic analysis using MrBayes and BEAST. We herein report that target enrichment by specific capture may be a successful strategy for whole-genome sequencing of DMV directly from field samples. By this strategy, 14 complete and one partially complete genomes were obtained, with reads mapping to the virus up to 98% and coverage up to 7800X. The phylogenetic tree well discriminated the Mediterranean and the NE-Atlantic strains, circulating in the Mediterranean Sea and causing two different epidemics (2008-2015 and 2014-2017, respectively), with a limited time overlap of the two strains, sharing a common ancestor approximately in 1998.

Occurrence of Brucella ceti in stranded bottlenose dolphins Tursiops truncatus coincides with calving season

Brucellosis is a disease caused by the Gram-negative facultative intracellular bacterium Brucella spp. In terrestrial species, this zoonotic bacterium is a global public health risk, but there is also concern over the zoonotic potential of marine forms, such as B. ceti, which affects cetaceans. Due to the detection of B. ceti in samples from bottlenose dolphins Tursiops truncatus during the 2010-2014 Gulf of Mexico Unusual Mortality Event, a long-term study of the prevalence of Brucella in stranded bottlenose dolphins from South Carolina, USA, was conducted. From 2012 through 2017, 282 stranded bottlenose dolphins were tested for B. ceti via real-time PCR. Nearly 32% of the dolphins tested positive in at least one sample (brain, lung, blowhole swab). Very little information exists in the literature on the occurrence of Brucella spp. in marine mammals, though in terrestrial species, such as cattle and elk, higher prevalence is often reported in spring. Similar results were found in this study with the peak occurrence being between March and June, a known period of calving in South Carolina. Results from this study provide important insights into the occurrence of the marine bacterium B. ceti.

Pathologic findings and causes of death in bottlenose dolphins Tursiops truncatus stranded along the Georgia coast, USA (2007-2013)

Between 2007 and 2013, before the 2013 cetacean morbillivirus outbreak, 26 fresh bottlenose dolphin carcasses were necropsied on the coast of Georgia, USA. Here, we present the pathological and microbiological findings associated with their most likely causes of death. The primary cause of death was determined in 25 individuals and included systemic bacterial infection (n = 7), verminous and bacterial bronchopneumonia (n = 5), drowning/entanglement (n = 5), disseminated histoplasmosis (n = 1), intestinal intussusception (n = 1), vegetative endocarditis (n = 1), meningitis (n = 1), necrotizing dermatitis (n = 1), disseminated angiomatosis (n = 1), emaciation (n = 1) and stingray spine trauma (n = 1). Histiocytic and eosinophilic bronchopneumonia associated with Halocerchus sp. infection was observed in 69% of the animals (18/26) and eosinophilic gastritis due to Anisakidae nematodes was found in 36% of the examined stomachs (8/22). Moderate to severe eosinophilic pancreatitis with fibrosis was observed in 4 animals infected with Brachycladiidae trematodes. Proliferative and ulcerative lymphoplasmacytic dermatitis was found in 5 animals and was considered to contribute to deteriorated health status in 2 calves. Pulmonary and lymph node angiomatosis were observed in 15 and 10 animals, respectively. In at least 2 animals, the concentration of polychlorinated biphenyls (PCBs) in the blubber exceeded 1500 µg g-1 of lipid. Bottlenose dolphins stranded on the Georgia coast have a wide range of inflammatory lesions associated with a variety of helminth, bacterial, and fungal pathogens. Some resident animals have also been exposed to high levels of PCB contamination, which could reduce host immunocompetence. Higher exposure to these or other pathogens could result in further decline in the health of resident and migrant dolphin populations in this region.

Viral emergence in marine mammals in the North Pacific may be linked to Arctic sea ice reduction

Climate change-driven alterations in Arctic environments can influence habitat availability, species distributions and interactions, and the breeding, foraging, and health of marine mammals. Phocine distemper virus (PDV), which has caused extensive mortality in Atlantic seals, was confirmed in sea otters in the North Pacific Ocean in 2004, raising the question of whether reductions in sea ice could increase contact between Arctic and sub-Arctic marine mammals and lead to viral transmission across the Arctic Ocean. Using data on PDV exposure and infection and animal movement in sympatric seal, sea lion, and sea otter species sampled in the North Pacific Ocean from 2001-2016, we investigated the timing of PDV introduction, risk factors associated with PDV emergence, and patterns of transmission following introduction. We identified widespread exposure to and infection with PDV across the North Pacific Ocean beginning in 2003 with a second peak of PDV exposure and infection in 2009; viral transmission across sympatric marine mammal species; and association of PDV exposure and infection with reductions in Arctic sea ice extent. Peaks of PDV exposure and infection following 2003 may reflect additional viral introductions among the diverse marine mammals in the North Pacific Ocean linked to change in Arctic sea ice extent.

Role of social behaviour in the epidemiology of lobomycosis-like disease (LLD) in estuarine common bottlenose dolphins from Ecuador

Lobomycosis-like disease (LLD) is a chronic granulomatous skin disorder that affects Delphinidae worldwide. LLD has been observed in common bottlenose dolphins Tursiops truncatus from the Gulf of Guayaquil, Ecuador, since 1990. Although exogenous factors such as salinity and pollution may play a role in the pathogenesis of this disease in estuarine and coastal dolphin communities, we hypothesized that demography and social behaviour may also influence its epidemiology. To address this issue, the role of social behaviour in the distribution and prevalence of LLD was assessed through hierarchical cluster analysis and spatial distribution analysis in 7 dolphin communities inhabiting the inner estuary. Individuals with LLD lesions were observed in 5 of the 7 dolphin communities, with 13 of the 163 (8%) animals being positive, all adults. Among 8 dolphins of known sex, LLD affected mostly males (86%), who usually were found in pairs. Prevalence was low to moderate (5.1-13%) in dolphin communities where low-rank males had LLD. Conversely, it was high (44.4%, n = 9) in a small community where a high-rank male was infected. LLD affected both dolphins in 2 of the 4 male pairs for which large time series data were available, suggesting horizontal transmission due to contact. Thus, association with LLD-positive males seems to be an important risk factor for infections. Additionally, low-rank males had larger home ranges than high-rank males, indicating that low-status LLD-affected dolphins are likely responsible for the geographic dissemination of the disease in this population.

Genome-wide association study of an unusual dolphin mortality event reveals candidate genes for susceptibility and resistance to cetacean morbillivirus

Infectious diseases are significant demographic and evolutionary drivers of populations, but studies about the genetic basis of disease resistance and susceptibility are scarce in wildlife populations. Cetacean morbillivirus (CeMV) is a highly contagious disease that is increasing in both geographic distribution and incidence, causing unusual mortality events (UME) and killing tens of thousands of individuals across multiple cetacean species worldwide since the late 1980s. The largest CeMV outbreak in the Southern Hemisphere reported to date occurred in Australia in 2013, where it was a major factor in a UME, killing mainly young Indo-Pacific bottlenose dolphins (Tursiops aduncus). Using cases (nonsurvivors) and controls (putative survivors) from the most affected population, we carried out a genome-wide association study to identify candidate genes for resistance and susceptibility to CeMV. The genomic data set consisted of 278,147,988 sequence reads and 35,493 high-quality SNPs genotyped across 38 individuals. Association analyses found highly significant differences in allele and genotype frequencies among cases and controls at 65 SNPs, and Random Forests conservatively identified eight as candidates. Annotation of these SNPs identified five candidate genes (MAPK8, FBXW11, INADL, ANK3 and ACOX3) with functions associated with stress, pain and immune responses. Our findings provide the first insights into the genetic basis of host defence to this highly contagious disease, enabling the development of an applied evolutionary framework to monitor CeMV resistance across cetacean species. Biomarkers could now be established to assess potential risk factors associated with these genes in other CeMV-affected cetacean populations and species. These results could also possibly aid in the advancement of vaccines against morbilliviruses.

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.

Ranging patterns, spatial overlap, and association with dolphin morbillivirus exposure in common bottlenose dolphins (Tursiops truncatus) along the Georgia, USA coast

During 2013-2015, an outbreak of dolphin morbillivirus (DMV) occurred in the western North Atlantic, which resulted in the stranding of over 1,600 common bottlenose dolphins (Tursiops truncatus). There are currently five coastal and 10 bay, sound, and estuary dolphin stocks along the U.S. Atlantic coast, yet there is very limited understanding of which stocks were exposed to DMV during the recent outbreak, or how DMV was transmitted across stocks. In order to address these questions, information is needed on spatial overlap and stock interactions. The goals of this project were to determine ranging patterns, prevalence of DMV, and spatial overlap of the South Carolina-Georgia (SC-GA) Coastal Stock, and adjacent Southern Georgia Estuarine System (SGES) Stock. During September 2015, a health assessment and telemetry study was conducted in which 19 dolphins were captured, tested for antibodies to DMV, and satellite tagged. Dolphins were classified into one of three ranging patterns (Coastal, Sound, or Estuary) based upon telemetry data. Coastal dolphins (likely members of the SC-GA Coastal Stock) had a significantly higher prevalence of positive DMV antibody titers (0.67; N = 2/3), than Sound and Estuary dolphins (likely members of the SGES Stock) (0.13; N = 2/16). These results suggest that the SC-GA Coastal Stock may have experienced greater exposure to DMV as compared to the SGES Stock. However, due to the small size of the SGES Stock and its exposure to high levels of persistent contaminants, this stock may be particularly vulnerable to DMV infection in the future.

Positive selection in coding regions and motif duplication in regulatory regions of bottlenose dolphin MHC class II genes

The vertebrate immune response is mediated through highly adaptive, quickly evolving cell surface receptors, the major histocompatibility complex (MHC). MHC molecules bind and present a diverse array of pathogenic molecules and trigger a cascade of defenses. Use of MHC variation as a marker for population health has also evolved quickly following advances in sequencing methods. We applied a combination of traditional and next generation sequencing methodology to characterize coding (peptide binding region) and regulatory (proximal promoter) sequence variation in MHC Class II DQA and DQB genes between estuarine and coastal populations of the bottlenose dolphin, Tursiops truncatus, an apex predator whose health status is indicative of anthropogenic impacts on the ecosystem. The coding regions had 10 alleles each at DQA and DQB; the promoters had 6 and 7 alleles at DQA and DQB, respectively with variation within key regulatory motifs. Positive selection was observed for the coding regions of both genes while both coding and promoter regions exhibited geographic differences in allele composition that likely indicates diversifying selection across habitats. Most notable was the discovery of a complete duplication of a 14-bp T-box motif in the DQA promoter. Four class II promoter regions (DQA, DQB, DRA, DRB) were characterized in species from four cetacean families (Delphinidae, Monodontidae, Lipotidae, and Physeteridae) and revealed substantial promoter structural diversity across this order. Peptide binding regions may not be the only source of adaptive potential within cetacean MHC for responding to pathogenic threats. These findings are the first analysis of cetacean MHC regulatory motifs, which may divulge unique immunogenetic strategies among cetaceans and reveal how MHC transcriptional control continues to evolve. The combined MHC regulatory and coding data provide new genetic context for distinct vulnerability profiles between coastal and estuarine populations, which are key concerns for health and risk management.

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.

Predicting the effects of polychlorinated biphenyls on cetacean populations through impacts on immunity and calf survival

The potential impact of exposure to polychlorinated biphenyls (PCBs) on the health and survival of cetaceans continues to be an issue for conservation and management, yet few quantitative approaches for estimating population level effects have been developed. An individual based model (IBM) for assessing effects on both calf survival and immunity was developed and tested. Three case study species (bottlenose dolphin, humpback whale and killer whale) in four populations were taken as examples and the impact of varying levels of PCB uptake on achievable population growth was assessed. The unique aspect of the model is its ability to evaluate likely effects of immunosuppression in addition to calf survival, enabling consequences of PCB exposure on immune function on all age-classes to be explored. By incorporating quantitative tissue concentration-response functions from laboratory animal model species into an IBM framework, population trajectories were generated. Model outputs included estimated concentrations of PCBs in the blubber of females by age, which were then compared to published empirical data. Achievable population growth rates were more affected by the inclusion of effects of PCBs on immunity than on calf survival, but the magnitude depended on the virulence of any subsequent encounter with a pathogen and the proportion of the population exposed. Since the starting population parameters were from historic studies, which may already be impacted by PCBs, the results should be interpreted on a relative rather than an absolute basis. The framework will assist in providing quantitative risk assessments for populations of concern.

Model-based testing for space-time interaction using point processes: An application to psychiatric hospital admissions in an urban area

Spatio-temporal interaction is inherent to cases of infectious diseases and occurrences of earthquakes, whereas the spread of other events, such as cancer or crime, is less evident. Statistical significance tests of space-time clustering usually assess the correlation between the spatial and temporal (transformed) distances of the events. Although appealing through simplicity, these classical tests do not adjust for the underlying population nor can they account for a distance decay of interaction. We propose to use the framework of an endemic-epidemic point process model to jointly estimate a background event rate explained by seasonal and areal characteristics, as well as a superposed epidemic component representing the hypothesis of interest. We illustrate this new model-based test for space-time interaction by analysing psychiatric inpatient admissions in Zurich, Switzerland (2007-2012). Several socio-economic factors were found to be associated with the admission rate, but there was no evidence of general clustering of the cases.

Post-mortem findings in southern right whales Eubalaena australis at Península Valdés, Argentina, 2003-2012

Between 2003 and 2012, 605 southern right whales (SRW; Eubalaena australis) were found dead along the shores of Península Valdés (PV), Argentina. These deaths included alarmingly high annual losses between 2007 and 2012, a peak number of deaths (116) in 2012, and a significant number of deaths across years in calves-of-the-year (544 of 605 [89.9%]; average = 60.4 yr(-1)). Post-mortem examination and pathogen testing were performed on 212 whales; 208 (98.1%) were calves-of-the-year and 48.0% of these were newborns or neonates. A known or probable cause of death was established in only a small number (6.6%) of cases. These included ship strike in a juvenile and blunt trauma or lacerations (n = 5), pneumonia (n = 4), myocarditis (n = 2), meningitis (n = 1), or myocarditis and meningitis (n = 1) in calves. Ante-mortem gull parasitism was the most common gross finding. It was associated with systemic disease in a single 1-2 mo old calf. Immunohistochemical labeling for canine distemper virus, Toxoplasma gondii and Brucella spp., and PCR for cetacean morbillivirus (CeMV), influenza A, and apicomplexan protozoa were negative on formalin-fixed, paraffin-embedded lung and brain samples from a subset of whales; PCR for Brucella spp. was positive in a newborn/neonate with pneumonia. Skin samples from whales with gull parasitism were PCR negative for CeMV, poxvirus, and papillomavirus. This is the first long-term study to investigate and summarize notable post-mortem findings in the PV SRW population. Consistent, significant findings within or between years to explain the majority of deaths and those in high-mortality years remain to be identified.

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.